A Critical Review and Analysis on the Recycling of ... - ACS Publications

Perspective Cite This: ACS Sustainable Chem. Eng. 2018, 6, 1504−1521

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A Critical Review and Analysis on the Recycling of Spent Lithium-Ion Batteries Weiguang Lv,†,‡,§ Zhonghang Wang,†,§ Hongbin Cao,†,§ Yong Sun,∥ Yi Zhang,†,§ and Zhi Sun*,†,§ †

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National Engineering Laboratory for Hydrometallurgical Cleaner Production & Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China ‡ University of Chinese Academy of Sciences, Beijing 100190, China § Beijing Engineering Research Center of Process Pollution Control, Beijing 100190, China ∥ Edith Cowan University School of Engineering, 270 Joondalup Drive, Joondalup, Western Australia 6027, Australia ABSTRACT: Recycling of spent lithium-ion batteries (LIBs) has attracted significant attention in recent years due to the increasing demand for corresponding critical metals/materials and growing pressure on the environmental impact of solid waste disposal. A range of investigations have been carried out for recycling spent LIBs to obtain either battery materials or individual compounds. For the effective recovery of materials to be enhanced, physical pretreatment is usually applied to obtain different streams of waste materials ensuring efficient separation for further processing. Subsequently, a metallurgical process is used to extract metals or separate impurities from a specific waste stream so that the recycled materials or compounds can be further prepared by incorporating principles of materials engineering. In this review, the current status of spent LIB recycling is summarized in light of the whole recycling process, especially focusing on the hydrometallurgy. In addition to understanding different hydrometallurgical technologies including acidic leaching, alkaline leaching, chemical precipitation, and solvent extraction, the existing challenges for process optimization during the recycling are critically analyzed. Moreover, the energy consumption of different processes is evaluated and discussed. It is expected that this research could provide a guideline for improving spent LIB recycling, and this topic can be further stimulated for industrial realization. KEYWORDS: Spent LIBs, Pretreatment, Recycling, Environmental impact, Hydrometallurgy

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fluoride (HF).6 Furthermore, during the cycle life period, Li tends to deposit on the anode due to overcharging or other improper usage. The deposited Li can react with water to release hydrogen gas (H2) and produce lithium hydroxide (LiOH). The residual electric power tends to cause explosions or fire accidents.7 Therefore, effective recycling of spent LIBs in light of the environmental and safety challenges is critical to ensure sustainable development in this field. A single methodology is hard to be both cost-effective and environmentally friendly due to the complexity of raw materials. Therefore, a combination of physical and chemical approaches is widely adopted to recycle spent LIBs. Generally, physical methods are used to enhance the efficiency of recycling and typically include dismantling, crushing, sieving, and thermal and mechanochemical treatment.8 The chemical methods could be classified into pyrometallurgy and hydrometallurgy. In comparison with pyrometallurgical processes that are usually undertaken at high temperature, hydrometallurgical methods

INTRODUCTION The rapid growth of lithium-ion batteries (LIBs) used in portable electronic devices and electric vehicles requires a significant amount of metal resources, especially lithium (Li) and cobalt (Co).1 According to the United States Geological Survey (USGS) and the China Industry Information Network, nearly 40% of Li and 42.46% Co were consumed in the production of batteries in 2014.2,3 Specifically, the consumption of Co for power batteries has increased to 13.7% in 2016 and if the trend holds will increase to 20.3% in 2018 because of the rapid development of electric vehicles.4 Meanwhile, worldwide cobalt and lithium production have only increased slightly in recent years. With the current growth rate, significant pressure is imposed on the supply side of cobalt and lithium.5 It is predicted that Co and Li will face a serious shortage in the foreseeable future. Apart from the above-mentioned resource issues, the environmental and potential safety problems caused by spent LIBs are also substantial. If a spent LIB is directly discarded without proper treatment, heavy metals like Co, Ni, and Mn would contaminate soil and underground water. The electrolyte easily reacts with water to release harmful gas such as hydrogen © 2017 American Chemical Society

Received: October 26, 2017 Revised: December 6, 2017 Published: December 13, 2017 1504

DOI: 10.1021/acssuschemeng.7b03811 ACS Sustainable Chem. Eng. 2018, 6, 1504−1521

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ACS Sustainable Chemistry & Engineering

Figure 1. Supply risk, (a) circulability (CM), and (b) market value of different cathode materials based on their metal content; (c) estimation of spent LIBs in Canada, Mexico, and the USA, 2010−2030 and the market size in North America, USA, China, and globally (supply risk is based on the worldwide governance indicator, WGI; the quality of cathode materials only considers the quality of metals to evaluate the market value of cathode materials; metal prices are the 1-month average price obtained from Shanghai Metals Market).13−16,25,26

Commission and Shanghai Metals Market.13−16 It demonstrates that (1) the recycling of LiCoO2 and NCM is slightly more important and profitable than that of other materials due to high cobalt content, (2) the high-cost and low-circulability metals in the cathode materials are gradually replaced by lowcost and high-circulability ones with lower supply risks in the last decades, (3) to decrease the pressure from supply risk, it is necessary to enhance the circulability of Co and research new cathode materials containing metals with little supply risk and high circulability. The production of LIBs from 2011 to 2016 remains increasing at a fast rate and is estimated to reach 169.09 GWh in 2018.17−19 One reason is the rapid development of electric vehicles, whose sales remain increasing healthily in recent years.20 As important cathode materials of power battery, NCM, NCA, and LiFePO4 will increase accordingly, resulting in a large amount of valuable metals such as Ni, Co, and Li awaiting to be recycled through the waste stream.21 The components of LIBs waste will become much more complex without efficient classification and management. Nevertheless, data from the USGS indicated that at most 20% of the batteries available for recycling actually were recycled.22 Meanwhile, the International Resources Panel reported that less than 1% of lithium from spent LIBs was recycled in the world.23 Contrast this with the increasing quantity of spent LIBs around the world, which is illustrated in Figure 1(c) and also demonstrates the market revenue of LIBs in the USA from 2013 to 2024. Moreover, it is obvious that a positive correlation exists between the quantity of spent LIBs and the market size of LIBs. Therefore, from the market revenue of LIBs, the rising tendency of spent LIBs could be

have obvious advantages, such as milder reaction conditions, more environmentally friendly, and higher recovery efficiency of valuable metals, especially Li.1,9,10 These advantages make hydrometallurgical methods preferable and promising approaches for processing spent LIBs. In this paper, the current status of lithium-ion batteries and recently developed strategies in pretreatment and metallurgical processes are systematically addressed, focusing especially on the hydrometallurgical processes. Furthermore, the challenges and deficiencies are analyzed and discussed. The regulations and legislations concerning spent LIB management are also reviewed. The aim of this review is to provide a general guideline for how spent LIB recycling techniques can be improved.

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DEVELOPMENT OF LITHIUM-ION BATTERIES At the beginning of the 1990s, SONY manufactured the first ever commercial rechargeable LIBs in the world, consisting of a carbon anode and a LiCoO2 cathode.11 Since then, LIBs have been regarded as the most promising “green battery” for their high energy density, good design flexibility, and long lifespan in comparison with other types of batteries.12 For the increasing needs of developing battery-powered devices to be satisfied, new types of LIBs have been extensively explored in recent years, including LiCoO2, LiNiO2, LiFePO4, lithium nickel cobalt manganese (NCM), and lithium nickel cobalt aluminum (NCA). As seen in Figure 1(a and b), the supply risk, circulability (CM), and market value of different cathode materials are evaluated based on data from the European 1505


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ACS Sustainable Chemistry & Engineering predicted.24,25 The recycling of spent LIBs urgently needs to be studied to establish a more economic and eco-friendly industrial process than current processes.

waste battery streams ready for subsequent processing. The more careful the pretreatment is applied, the more convenient the following process will be. The pretreatment processes mainly include dismantling, crushing, screening, thermal treatment, mechanochemical method, dissolution, and so on. Some of valuable metals or materials, like Cu, Al, and anode, are easy to recycle through pretreatment due to their significantly different physical properties. Meanwhile, pretreatment methods play an important role in separating cathode materials from the Al foil and the organic binder, which will increase the complexity of leachate or make the waste hard to leach. For example, because of the malleable properties of copper being much better than those of graphite, the copper foils are easy to separate from graphite carbon particles.33 Shin et al.34 presented a single pretreatment technology in which the spent LIBs were crushed directly into a suitable size and then a magnetic separation was conducted to collect the magnet. At the end of the process, fine crushing and sieving were employed to eliminate Al foil, which will influence the leaching process. The removal of organic binder is important in the pretreatment process. Common solutions are thermal treatment,35,36 ultrasonic cleaning,37 and organic reagent dissolution.38 Granata et al.35 used two-rotor crushing and a splitter to achieve the separation of different materials. The organic binder was eliminated by thermal treatment at 300 °C for 2 h. However, the decomposition of organic components like PVDF will release toxic and hazardous gases such as HF and heavy metal-contaminated exhaust. Hence, using a system that consists of a cooler, a condensation chamber, carbon filters, and bag filters as tail gas process plants to dispose gases appears to be necessary. Considering these disadvantages of the thermal treatment, researchers tried organic reagents to dissolve the organic binder. For example, the mixture of N,N-dimethylformamide (DMF) and ethanol or N-methylpyrrolidone (NMP) is used as the dissolution reagent to dissolve PVDF, whereas the dissolution solvent itself is commonly known as toxicant.38 To offset the shortcoming of using a toxic solvent, Pant and Dolker39 reported a green, nontoxic, and environmentally friendly solvent: citrus fruit juice (CFJ), as dissolution reagent. Nevertheless, the execution of the process involving CFJ normally requires harsh conditions (over 90 °C) to achieve effective dissolution. In addition to mechanical processing approaches, the mechanochemical process is also an important technology that induces mechanically changes of raw materials to influence their physical and chemical properties through high-energy ballmilling of materials.40−43 Meanwhile, some chemical reactions could be accidentally started during the grinding and rubbing. After that, the activity of materials will be improved. Therefore, mechanochemical technology is usually used in pretreatment processes to change or disrupt the crystal structure of spent materials to enhance the leaching efficiency.40 Though many researches have focused on the research of pretreatment methods, some technical hurdles and challenges still exist during the pretreatment, as summarized in Table 1. Furthermore, the disordered classification of spent batteries, complex disassembly processes, and low efficiency of extracting valuable metals like lithium still hinder the application of some pretreatment processes. Therefore, to meet the goal of recycling all valuable materials or metals in spent LIBs, pretreatment methods need to be combined with other physical and chemical processes.

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STATE-OF-THE-ART FOR SPENT LIBS RECYCLING The recycling processes of spent LIBs mainly include reuse, repair, and recovery, among which the recovery process has drawn much attention and will be introduced in detail in this section. In addition, the challenges of recycling processes will be analyzed in the Discussion. A summary of currently available treatment approaches is shown in Figure 2. Prior to processing,

Figure 2. General flow sheet of spent LIB treatment processes.

the spent LIBs should be first discharged to reduce the existence of Li metal and minimize the risk of explosion. A common method is using salt-saturated solutions such as NaCl and Na2SO4 to discharge spent LIBs.27 The critical downside of this method is the emission of HF directly triggered by leakage of electrolyte into water, which is shown in eq 2. LiPF6 + H 2O → LiF + POF3 + 2HF↑

(1)

Afterward, there are three recycling routes: Route 1 is the recycling or recovery process, which is composed of pretreatment (sometimes the discharging process is also regarded as a pretreatment process), pyrometallurgical process, and hydrometallurgical process. Route 2 is the repairing process. Route 3 is the reusing process, which mainly focuses on reusing Cu, Al foil, and plastic that could be directly reused after disassembly. The profit of route 3 largely depends on the efficiency of the disassembly process. As for route 2, the advantage of it is shorting the recycling route to decrease the loss of valuable metals or materials and increase the profile of technologies. The general process is using NMP or other organic agents to separate cathode materials from Al foil and then achieving the repair of spent cathode materials through calcination.28−30 It is not cost-effective to respectively recover Fe and Li compounds from the spent LiFeO4 through conventional extraction technologies. Through the repairing process, a green chemical and economic technology could be established.30−32 Additionally, the methods of reuse and repair are often ignored though these processes could be very convenient and economical due to their short and effective flows. Pretreatment Method. For the efficiency of recycling materials to be enhanced, either a mechanical or chemical pretreatment process is usually applied to make the different 1506


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41,42,50,51

low energy consumption and almost no exhaust emission enhancing the leaching efficiency of valuable metal and making the reaction conditions become mild mechanochemical method

dissolve the adhesive substance using special organic reagents discording the structure of the materials using grinding techniques dissolution process

thermal process

Pyrometallurgical Process. The pyrometallurgical process is one branch of the extractive metallurgies to dispose ore and concentrates with thermal treatment through physical and chemical transformations to enable recovery of valuable metals. Pyrometallurgical methods have been widely investigated in recovering Zn, Ni, Cd, and other heavy metals from spent Zn− Mn dry batteries or Ni−Cd batteries.52,53 Generally, smelt slags were used in pyrometallurgical methods to separate metals in which some metals go to the slag and target metals turn into alloy. Except for the Umicore technology,54,55 pretreatment processes are unavoidable for most of the pyrometallurgical technologies. Ren et al.56 proposed a new slag system of MnOSiO2-Al2O3 by adding CaO+SiO2, pyrolusite, and some Al shells into the pretreated spent LIBs. The mixture was then heated to 1475 °C for 30 min. A high purity alloy with Co (99.03%), Ni (99.30%), Cu (99.30%), and enriched slag with MnO (47.03%) and Li2O (2.63%) were achieved by this novel process. In a typical pyrometallurgical process, Li will end up in the slag phase, which has to be further extracted.15 Carbothermal reduction methods as a pyrometallurgical method to recycle Li and other metals have received attention in recent years.57 In this process, the mixed spent LIBs can be converted to metal oxide, pure metal, or lithium carbonate. In one step, lithium carbonate is leached by water, whereas the graphite in the leaching slag burn and leave metal oxide as the final residue.58 In the subsequent step, pure metal, graphite, and lithium carbonate are further separated by wet magnetic separation.59 However, the pyrometallurgical technologies also currently face challenges on reducing energy consumption and matching the rigorous requirements for the treatment equipment. Hydrometallurgical Process. A hydrometallurgical process mainly consists of leaching and extraction. It has many advantages in comparison with the pyrometallurgical process, such as high extraction efficiency, low energy consumption, little hazardous gas emission, and low capital cost. It has a huge potential in industrial realization. However, little adaptability for disposing raw materials is a great challenge. Figure 3 shows a comprehensive summary of the hydrometallurgical process, which mainly includes leaching, solvent extraction, precipitation, and the electrochemical method. Among them, a very limited number of studies are reported on the disposal of spent

high energy consumption and noise problems

29,48,49

46,47

require high input of energy, cannot recover organic compounds, and would cause serious exhaust pollution if no exhaust purification device is equipped high cost of organic solvent as well as device investment simple and convenient operation

44,45 cannot recycle all kinds of components in spent LIBs completely simple and convenient operation

separate materials according to different physical properties, including density, conductivity, magnetic behavior, and so forth remove organic additives and binders via thermal treatment mechanical separation

advantages detail of methods technology

Table 1. Summary of Advantages and Disadvantages of Different Pretreatment Methods

disadvantages

ref


Figure 3. Hydrometallurgical processes for spent LIBs. 1507


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Figure 4. (a) Connections between pH and the equilibrium concentration of metal ions in aqueous solution (25 °C); (b) E-pH diagram for the CoH2O and Ni-H2O systems (25 °C, Co = 0.2 mol L−1, Ni = 0.2 mol L−1).

leaching reagents. The reaction mechanism of leaching by citric acid could be described as71

LIBs via the electrochemical process due to its high energy consumption, even though prior arts do suggest its feasibility for obtaining pure Co metal or Co compounds.8,60−62 Traditional Leaching. For spent LIBs to be recycled, the cathode materials are usually dissolved in leaching reagents followed by separation and extraction as the main steps, which are similar to other metallurgical processes. In early research, inorganic acid reagents, such as HCl, HNO3, and H2SO4 were widely used as leaching agents and were proven to be feasible and effective, but disadvantages, e.g., the emission of secondary pollutants and complexity of separation and purification steps, also appeared.47,63,64 The chemical reaction of leaching using HCl can be described as 8HCl + 2LiCoO2 → 2CoCl 2 + Cl 2 ↑ +2LiCl + 5H 2O

18LiNi1/3Co1/3Mn1/3O2 + 18H3Cit + C6H12O6→ 6Li3Cit + 2Ni3(Cit)2 + 2Co3(Cit)2 + 2Mn3(Cit)2 + 33H 2O + 6CO2 ↑

(4) 72

According to Li et al., the leaching efficiency of Co using citric acid is higher than that when using HCl or H2SO4, whereas the Li leaching efficiency remains similar among those different leaching media. Most of organic acids present a similar reaction mechanism to critic acid with some exceptions such as oxalic acid. The oxalic acid could act both as reductant and leachant, and the leaching efficiencies of Co and Li could achieve 97 and 98%, with the reaction described as68

(2)

4H 2C2O4 + 2LiCoO2 → CoC2O4 ↓ + LiHC2O4 + 2CO2 ↑ + 4H 2O

The reaction using other monatomic acid or ployatomic acid for leaching is similar. The leaching efficiency of Co without reductants follows the order of HCl > HNO3 ≈ H2SO4. The relatively high reducibility of HCl mainly contributes to this different leaching performance.65 Therefore, the leaching efficiency of most reagents would be unsatisfying unless H2O2 or other reductants are added. The mechanism of the reduction reaction can be described as (taking LiCoO2 as an example)

(5)

In addition to the acid leaching system, an alkaline system such as ammonia has also been investigated. Zheng et al.73 introduced an ammonia-ammonium sulfate system as a leaching system with metal selectivity during leaching. Ku et al.9 used a similar system including ammonia, ammonia sulfite, and ammonia carbonate to leach. It was easy to separate Cu from Co, Ni in the ammonia system, because Co and Ni in spent LIBs were in high valence state, making them hard to dissolve. Ammonia carbonate acted as a pH buffer to stabilize the pH of leaching solution. Ammonia sulfite was added as reductant to increase the leaching efficiencies of Co and Ni. In addition, the widely employed supercritical fluid in extracting metals offers a potential opportunity in leaching spent batteries. Bertuol et al.74 investigated the leaching of cobalt from the spent LIBs under a supercritical CO 2 atmosphere with sulfuric acid and H2O2. The results showed that the reduction duration and consumption of H2O2 could respectively drop from 60 min and 8 vol % to 5 min and 4 vol % while achieving the same leaching performance (95.5% Co). Liu et al. 75 used subcritical water to accelerate the dechlorination of PVC, which was regarded as the acid source in this experiment. Over 95% Co and closely 98% Li were leached under the conditions PVC/LiCoO2 ratio of 3:1, solid/ liquid ratio (S/L) of 16:1 (g/L), and temperature of 350 °C. However, the rigorous requirements of the equipment, high temperature, and high pressure atmosphere increase the capital cost and complexity of the operation. All of these technical

3H 2SO4 + 2LiCoO2 + 2H 2O2 → Li 2SO4 + 5H 2O + 1.5O2 ↑ + 2CoSO4

(3)

The reason that reductants like H2O2 or ascorbic acid can facilitate leaching can be explained by Figure 4(a). Although Co2+ is much easier to dissolve than Co3+ at room temperature, Co3+ is predominately rich in spent materials. Hence, when the Co3+ is converted to Co2+, the leaching efficiency and reaction kinetics will be obviously improved. Furthermore, the shadow in Figure 4(a) may be a favorable area to separate Co3+ from Cu2+, Mn2+, and other metal ions because of its significantly different solubility constant among these metal ions. With increasing in reductant concentrations, the leaching efficiency and reaction rate would first increase accordingly and then reach a plateau at which leaching efficiency and reaction rate would not vary appreciably.66 Except for adding reductant, many organic leaching reagents, such as citric acid,67 aspartic acid,67 malic acid,67 oxalic acid,68 ascorbic acid,69 and glycine,70 are extensively investigated to solve those problems associated when using the inorganic 1508


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ACS Sustainable Chemistry & Engineering Table 2. Cases of Leaching Spent LIBs Using Different Leaching Reagents

leaching efficiency (%) raw material Inorganic Acid Leaching spent LIBs spent LIBs (LiCoO2) LiFePO4 and LiMn2O4 LIB industry waste (LiCoO2) LiNixMnyCozO compounds spent LIBs (mixture) spent LIBs (LiCoO2) (from laptop computers) spent LIBs (LiCoO2) (from mobile phones) spent LIBs (LiCoO2) spent LIBs (LiCoO2) Alkaline Leaching spent LIBs (Li(Ni1/3Co1/3Mn1/3)O2) Organic Acid Leaching spent LIBs (LiCoO2) spent LiCoO2 and CoO spent LIBs (LiCoO2) spent LIBs (LiCoO2) spent LIBs (LiCoO2) spent LIBs (LiCoO2) spent LIBs (LiCoO2) spent LIBs (LiCoO2) spent LIBs (LiCoO2and LiNi0.5Co0.2Mn0.3O2)

reagent

temp (°C)

time (min)

Co

Li

ref

50 80 30 75 65−70 95 75 90 40 75

90 30 60 30 120 240 60 60 60 60

99.0 90.6 94.0 96.0 91.6 70.0 99.0 99.0 95.0

100.0 93.1 74.1 95.0 96.7 99.1 88.0 100.0 95.0

78 79 80 81 82 83 84 85 86 87

4 mol/L NH3-1.5 mol/L (NH4)2SO4 + 0.5 M Na2SO4

80

300

80.7

95.3

73

0.4 mol/L tartaric acid +0.02 mol/L ascorbic acid 1 mol/L oxalate + 5 vol % H2O2 2 mol/L citric acid + 0.6 g/g H2O2 (H2O2/spent LIBs) 1 mol/L oxalic acid 1 mol/L iminodiacetic acid + 0.02 M ascorbic acid 1 mol/L maleic acid +0.02 M ascorbic acid 0.5 mol/L glycine +0.02 M ascorbic acid 1.5 mol/L succinic acid + 4 vol % H2O2 2 mol/L L-tartaric acid + 4 vol % H2O2

80 80 70 95 80 80 80 70 70

60 120 80 150 120 120 120 40 30

93.0 96.7 96.0 97.0 99.0 99.0 91.0 100.0 98.6

95.0

69 88 89 68 66 66 70 90 37

1.75 mol/L HCl 4 mol/L HCl 6.5 mol/LHCl + 5 vol % H2O2 2 mol/L H2SO4+5 vol % H2O2 4 mol/L H2SO4 + 5 vol % H2O2 1 mol/L H2SO4 + 0.075 M NaHSO3 2 mol/L H2SO4 + 5 vol % H2O2 2% H3PO4 + 2 vol % H2O2 0.7 mol/L H3PO4 + 4 vol % H2O2 1 mol/L HNO3 + 1.7 vol % H2O2

98.0 98.0 90.0 96.0 96.0 99.1

hurdles mentioned above have reduced the passion for applying supercritical fluid in recycling batteries. Table 2 provides a summary of the details of leaching processes of spent LIBs. Though there are many reports about leaching processes, few of them focus on explaining the leaching mechanism based on the crystallographic method at the molecular or atomic level. Takacova et al.76 explored the change of spent LIBs in the HCl leaching process depending on the change in d(003). It could be a good choice for further investigations of the leaching process in the future. The more mechanisms we understand for the leaching process, the more conveniences we obtain for enhancing the efficiency of the leaching process. For achieving visualization of pros and cons of using different leaching reagents, quantifying methods for leaching rates of Li and Co are proposed in this work. The leaching rate of metal is defined as rM = WM × a × R /t

(6)

Figure 5. Spider chart for a relative evaluation index of leaching spent LIBs with typical leaching reagents.

where rM represents the leaching rate of metal, WM (w/w %) represents weight percentage of metal in raw materials (spent LIB), a (%) is the leaching efficiency of metal, R (g/L) is the S/ L, and t is the leaching time. This equation allows us to compare the leaching performance among different reagents. In general, the leaching efficiency of valuable metals can reach more than 90%. However, some of them use a low S/L or long leaching time. Assuming 1 kg of Co is leached from spent LIBs by different leaching processes, greenhouse gas (GHG) emissions, energy consumption, and cost are also calculated with stoichiometric consumption of materials to evaluate recycling. The relative data are gathered from the greenhouse gases, regulated emissions, and energy use in transportation (GREET) model proposed by Argonne National Laboratory.77 As given in Figure 5, the GHG emission, energy consumption,

and cost of organic reagent are much higher than those of inorganic reagent. However, considering the biodegradability of leaching reagent and reducing flue gas of the productive process, the advantages of organic reagent are quite obvious.67 Moreover, we do not give the relevant data about GHG emission and energy consumption of H2SO4. The leaching rate of valuable metal in H2SO4 is much better than other reagents for a large S/L and short reaction time. However, H2SO4 is usually obtained as a byproduct of other technologies in many companies, i.e., copper smelting. Therefore, there are no data about GHG emission and energy consumption of H2SO4 production.77 1509


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immiscible liquids to separate them from each other. Although facing the challenges of separating compounds with similar functional groups, it remains reliable and is widely adopted in the extraction of tungsten and molybdenum, copper from minerals, nuclear reprocessing, and the production of fine organic compounds. The effect of equilibrium pH on the extraction of different metals is significant in solvent extraction. For example, the di(2ethylhexyl) phosphoric acid (D2EHPA) is good at extracting copper and manganese ions, whereas its selectivity in extracting Co is poor at pH 2.2−3.0.102 When the pH of the leachate increases, the extraction efficiency of Co with cationic extractant D2EHPA is improved accordingly.103 The extraction reaction follows the mechanism63,104

In summary, leaching time, agitation speed, solid-to-liquid ratio, temperature, and concentration of leachant and reductant were found to be the most influential factors on the leaching performance. The leaching process would be enhanced with increasing temperature, leaching time, agitation speed, as well as concentrations of leachant and reductant, whereas the leaching efficiency and rate both obviously decrease as the solid−liquid ratio increases. It should be noted that plateaus would show up when these factors increase to a certain value. These will guide future efforts in optimization of leaching processes upon processing different types of LIBs using different leaching media. Biometallurgical Process. The performance of the biometallurgical process primarily depends on the ability of microorganisms to convert insoluble solid compounds into soluble and extractable forms.91 Mishra et al.92 used chemolithotrophic and acidophilic bacteria Acidithiobacillus ferrooxidans as leaching bacteria. The reaction could be maintained at 30 °C with a pH of 2.5, but the leaching efficiencies of Co and Li both were quite low even with a long leaching time and Fe2+ as catalyst. However, according to the reports from Zeng et al. and Chen et al.,93,94 the leaching efficiency of Co could reach 98.4% within 7 days in Acidithiobacillus ferrooxidans with 0.02 g/L Ag+. Similarly, Cu2+ could also be used as catalyst during the Acidithiobacillus ferrooxidans leaching process.95 The result showed that the leaching efficiency of Co could reach 99.9% in 6 days with 0.75 g/L of Cu2+ added into solution. Using a mixed culture of different bacteria in one system was trialed, such as the system mixed with acidophilic sulfur-oxidizing bacteria (SOB) and iron-oxidizing bacteria (IOB).96,97 Fungal leaching is a favorable technology compared with bacterial leaching.98 It has many advantages, including growing over a wide pH range, tolerating toxic materials, and conducting with a high leaching rate. Various organic acids in fungi metabolites have been used to achieve the leaching process.98,99 Compared to the conventional methods, the biometallurgical process occurs under mild conditions with less energy consumption, making it an eco-friendly technology.100 Nevertheless, the slow kinetics and low pulp density are fatal weaknesses of the biometallurgical process when it is applied to industrial production. In one research study,101 the bioleaching efficiency decreased from 52 to 10% for Co and from 80 to 37% for Li when the pulp density increased from 1 to 4%. Even though high leaching efficiencies of Co and Li may be achieved with a high pulp density by controlling reaction temperature, increasing the dose of mixed energy substrates, and adjusting the pH,101 the leaching processes are still very time consuming. Hence, the biometallurgical methods of disposing spent LIBs are still far from industrial application, although they have significant advantages in energy-saving. Solvent Extraction. One of the main targets for the recycling process is to obtain pure metal or metal compounds. However, the coexistance of various metal ions in the leachate will inevitably suppress the recycling of pure metal or metal compounds. In addition, the overlap of pH range for precipitation of different metals makes the attempt of single step precipitation ineffective for obtaining pure metals. Hence, the leaching solution must undergo numerous steps of separation and extraction, e.g., solvent extraction, selective precipitation, and electrochemical method to achieve satisfactory levels of purity. Solvent extraction is a liquid−liquid extraction method that utilizes the different relative solubilities of compounds in two

M2Aq+ + A −Org + 2(HA)2Org → MA 2·3HA Org + H+Aq

(7)

or + + 2(HA)2Org + MOH(Aq) + A −Org → M(OH)A· 3HA (Org) + H(Aq)

(8)

where as

A −Org

Na +Aq +

+ 2(HA)2Org represents the saponification reaction 1 (HA)2Org → NaA Org + H+Aq 2

(9)

The extractant PC-88A can effectively separate Co and Ni ions from other metal ions at pH 4.5, whereas it has no extraction efficiency when the pH is less than 3.102 Cyanex272 has been widely investigated as an extractant due to its excellent selectivity. Swain et al.81 used Cyanex 272 as extractant, 5 vol % tributyl phosphate (TBP) as phase modifier, and kerosene as diluent to extract 85.42% Co from the leachate at pH 5. Jha et al.105 also reported a similar system except that isodecanol was used as phase modifier. The extraction efficiency of Co reached 99.9% at pH 5.0. The suitable scales of pH of different extraction reagents are summarized in Figure 6.79,103,106−108 It is obvious that the suitable pH to separate Co and Ni of some reagents distributes in the pH range between 3 and 5, which requires a good

Figure 6. Effect of suitable pH on the solvent extraction of different extraction reagents (the pH scale of different extractants is summarized under the same conditions including 25 °C and A:O = 1, except Mextral 5640H (A:O = 2)). 1510


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methods to achieve one-step fabrication from leachate to regenerate materials were recently researched, such as the leaching-resynthesis method.110−112 The leaching-resynthesis method, which belongs to regeneration methods, is focused on synthesizing the regenerated materials in short steps through sol−gel or coprecipitation technologies. In recent research, Sa et al.111 used the leachate as a raw liquor to regenerate LiNi1/3Mn1/3Co1/3O2 in N2 atmosphere at room temperature using a typical coprecipitation method. After 50 cycles, the capacity of regenerated material decreases to 80% (120 mA h g−1) with the first cycle.111 With previous experience of using ascorbic acid for leaching, Lu et al.113 adjusted the metal ion ratio and pH of the leachate to obtain regenerated cathode material LiCo1/3Ni1/3Mn1./3O2 through a sol−gel process. Zou et al.114 used similar technology to dispose the mixed raw cathode materials and obtained regenerated cathode materials as products with good electric performance. Some information on the leaching-resynthesis approaches are provided in Table 3. It can be seen that the regenerated cathode materials present similar characteristics to the commercial batteries in terms of rate capacity and cycle life. Among them, the electrochemical properties of regenerated cathode materials from the ascorbic acid leaching system are much better than those prepared from other systems. Other than that, the available data suggest that little difference of electrochemical properties exists in cathode material from different leachates. Except for cathode materials, synthesizing other reactive materials from the spent LIBs is also a good alternative and has been widely developed by many researchers. Yao et al.115 used a simple technology, including pretreatment, sulfuric acid leaching, filtering, sol−gel, and calcination method, to obtain sintered or hydrothermal cobalt ferrite precursor (S-CoFe2O4 or H-CoFe2O4). The products have excellent characteristics in terms of magnetostriction coefficient (−158.5 ppm) and train derivative coefficient (−1.69 × 10−9 A−1).115

performance in corrosion resistance for the reactor. For this reason, Cynaex 272 and P507 may be a good choice. The additive can change the optimal pH of solvent extraction. For example, in Figure 6, when the PC-88A is used alone to selectively extract Co, the suitable pH range falls between 3.5 and 4. The extraction efficiency of Ni is low in this range. When TOA is added as phase modifier, the suitable pH scale will shift between 3.5 and 5, which is higher than its previous one and leaves more room for operational parameters to adjust. Precipitation. The selective precipitation is a single chemical process that has been widely investigated and applied in extracting metals from complex systems. Sometimes, it is hard to precipitate only one ion from solution. From the E-pH diagram shown in Figure 4(b), the overlap between stable areas of Co(OH)2 and Ni(OH)2 is so large that Ni2+ and Co2+ are prone to be coprecipitated via neutralization reaction. However, Figure 4(b) also indicates that the stable areas of Ni2+ and Co(OH)3 have a small overlap. Thus, one possible approach is to transform Co2+ to Co3+ to achieve selective precipitation of Co3+ in this small area. This strategy was proven to be feasible and effective by Joulié et al.65 With NaClO as oxidant, the recovery efficiencies of Co and Ni were both nearly 100%. The reaction mechanism can be expressed as Co2 + + ClO− + 2H3O+ → 2Co3 + + Cl− + 3H 2O

(10)

Co3 + + 6HO− → Co2O3 + 3H 2O

(11)

It should be noted that no Mn exists in the system reported by Joulié et al.65 When Mn2+ is oxidized to Mn4+ at pH 2, it will form MnO2 or manganese hydroxide according to the reaction 3Mn 2 + + 2MnO4 + 2H 2O → 5MnO2 + 4H+

(12)

The dimethylglyoxime reagent (DMG, C4H8N2O2) is widely used to precipitate Ni2+ as nickle dimethylglyoxime chelating precipitate from Co, Ni, and Mn mixed solutions. As reported by Chen et al.,109 nearly 96% of Ni2+ could be precipitated within 20 min at room temperature (eq 14). The values of pKsp for Co2+, Ni2+, and Li+ are on the order of NiC2O4 ≈ CoC2O4 ≫ Li2C2O4.39 After removing Ni2+ and Co2+, the main metal ion in leachate is Li+, which can be precipitated efficiently as Li2CO3 or Li3PO4 (eq 16).71

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CURRENT RESEARCH FOR THE RECYCLING OF ANODE AND ELECTROLYTE The recycling of anode and electrolyte is also important to establish a comprehensive recovery technology of the spent LIBs as well as to release the environmental pollution and potential safety risks. However, because of their relatively low value, only a little attention has been paid to this area. In the Umicore process, the electrolyte is removed and pyrolyzed under 300 and 600 °C, respectively.120 In hydrometallurgical processes, the electrolyte can be reclaimed using an organic or supercritical solvent.121 Liu et al.122 developed a process for the recycling of spent LIB electrolyte including supercritical CO2 extraction, weakly basic anion exchange resin deacidification, molecular sieve dehydration, and component supplement. The electrochemical performance of the reclaimed electrolyte was acceptable compared to that of the commercial one. The high cost and low process capacity are the key factors limiting further promotion of supercritical solvent. As for the anode, it is usually separated from spent LIBs through physical methods, including dismantling, crushing, screening, and other mechanical processes. Guo et al.123 indicated that 30.07 mg/g of Li existed in the anode active materials. Therefore, a traditional acid leaching method was used to recover Li from anode active materials. Moreover, the graphite obtained from spent anode showed a large surface area and stable crystal structure. After removing the organic binder

6C4 H8N2O2 + Ni3(Cit)2 → 3Ni(C4H6N2O2 )2 + 2H3Cit (13)

(NH4)2 C2O4 + Co2 + + 2OH− → CoC2O4 · 2H 2O + 2NH3

(14)

Co3(Cit)2 + 3H 2C2O4 → 3CoC2O4 + 2H3Cit

(15)

Li3Cit + H3PO4 → Li3PO4 + H3Cit

(16)

Method of Leaching Resynthesis. Traditional separation and extraction technologies, e.g., solvent extraction, precipitation, and ion-exchange, are usually not economically justifiable to be applied in industrial production due to their significant disadvantages, e.g., complicated recycling routes, high chemical reagent consumption, and high waste emission. Therefore, a short and efficient route for the recycling of spent LIBs is the potential process and needs to be researched. To shorten the route, avoid the problems in separating metal ions from each other, reduce secondary pollution, and enhance the recycling efficiencies of valuable metals, material synthesis 1511


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110 111 113 116 117 118 114 119 ammonia solution NaOH and NH3·H2O metal nitrate ammonia solution NaOH and NH3·H2O controlled crystallization NaOH oxalic acid

197.7, 174.3, 168.3 139.0 147.2 (0.5 C) 154.2 (0.2 C) 155.0 152.7 (0.2 C) 160.0 258.8

CURRENT INDUSTRIAL RECYCLING PROCESS The recovery of spent LIBs are relatively new in comparison with the recycling of Ni-Cd and Pb-acid batteries, and many of the technologies are still in lab- or small-scale pilot stages. The first commercial production line was established by TOXCO in 1994.126 After that, with the increased attention, more and more technologies have been applied in commercial production, and many companies have established a complete line to recycle spent LIBs around the world. Current industrial processes for the recycling of spent LIBs are summarized in Table 4. The percentage and annual processing capacity of spent LIBs recycled using different technologies are shown in Figure 7 in which the data are mainly based on 30 and 12 companies, respectively. A flow sheet of the main processes is shown in Figure 7(c). Many of the commercial processes used pyrometallurgical methods as secondary technologies.127 The reason is that most of them are not an LIB-dedicated recycling process in their original design, such as Xstrata, Batrec AG, Akkuser, and so forth. Only Co, Ni, and Cu could be recovered effectively through pyrometallurgical methods. Li and Al are lost in the slag. Moreover, an alloy of cobalt and nickel also needs to be processed through hydrometallurgical methods, such as electrolyzing. Therefore, most of these companies establish a process combining pyrometallurgical and hydrometallurgical methods. In the Umicore process, the discharging phase is omitted, and pretreatment of spent LIBs is unnecessary, which are the important technologies in other processes. Compared to other processes, it is simple and effective. Complex mechanical methods are used to separate materials from each other. The Cu foil, Al foil, and steel are separated from other components and reused directly in new batteries through mechanical methods in other processes. However, they need to be further recovered to obtain production in the Umicore process. Toxco and Sumitomo-Sony processes face the issues of gas emissions in pyrometallurgical methods and H2 emissions in wet crushing. The processes include similar methods that also have these issues. The Recupyl Valibat process conducts the recycling process under low temperature, making it easy to dispose of flue gas and H2. Handling spent LIBs under a CO2 atmosphere also reduces the risk of mechanical treatment with discharged LIBs. Many hydrometallurgical methods have also been achieved in industrial applications, including the Recupyl Valibat process, Toxco process, Accurec, and so forth. In the Recupyl process, the slag from mechanical treatment is dissolved in H2SO4. Cobalt in solution is oxidized by NaClO to obtain cobalt hydroxide. Lithium remaining in the solution is precipitated by CO2 gas. In other companies, the hydrometallurgical processes include similar technologies, such as leaching, solvent extraction, precipitation, and so forth. Their long routes are the main drawback, which will result in the loss of valuable metal and pollution. Brump establishes a closedloop for the recycling of spent LIBs from waste to regenerated cathode materials or other valuable materials, which could achieve the recycling of spent LIBs in a short route. The details of these hydrometallurgical processes are not available, but they could be similar to the processes we introduced in Hydrometallurgical Process.

H2SO4 (+ H2O2) H2SO4 (+ H2O2) D,L-malic acid citric acid (+ H2O2) H2SO4 (+ H2O2) H2SO4 (+ H2O2) H2SO4 (+ H2O2) ascorbic acid LiNixCoyMn1−x−yO2 (LiNi0.8Co0.1Mn0.1O2 LiNi0.5Co0.2Mn0.3O2 LiNi1/3Co1/3Mn1/3O2) LiNi1/3Mn1/3Co1/3O2 LiNi1/3Mn1/3Co1/3O2 LiNi1/3Co1/3Mn1/3O2 LiNixMnyCozO2 Li[(Ni1/3Co1/3Mn1/3)1−xMgx]O2 LiNi1/3Mn1/3Co1/3O2 Li1.2Co0.13Ni0.13Mn0.54O2

sulfate salts sulfate salts solution nitrate salts sulfate salts sulfate salts sulfate salts acetate salts

leaching reagent

addition reagent

and other organic impurities under high temperature, it could be used as a porous supporting material to synthesize new functional materials like sorbents.124,125

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final production

Table 3. Summary of the Regeneration Approach of Cathode Materials from Spent LIBs in the Literature

precipitant

initial discharge capacity (mA h g−1, 2.7−4.3 V, 0.1 C)

ref


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300 200 6000

20000 3600

U.S.A.

France Switzerland U.S.A.

Japan

Finland Canada France

Germany

U.K. Canada/ Norway USA

Germany China

China

Umicore (VAL’EAS) SNAM Batrec AG Inmetco

Sumitomo-Sony

AkkuSer Ltd. Toxco Recupyl Valibat

Accurec GmbH

AEA Glencore plc. (former Xstrata) Onto process

LithoRec proces Green Ecomanufacture HiTech Co Bangpu Ni/Co High-Tech Co

7000

6000

4000 4500 110

150

7000

location(s)

company/process

annual capacity (tonnes/year)

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hydrometallurgical methods including leaching, purifying, and leaching- resynthesis used

combines similar mechanical and hydrometallurgical methods hydrometallurgical methods including leaching, purifying, and leaching- resynthesis used

preliminary step involves discharge, electrolyte recovery, refurbishing, and ball mill; supercritical fluid used to separate different materials

vacuum furnace used first; mechanical methods then used to separate different materials; scrap then fed to an electric furnace; slag is disposed of through hydrometallurgical methods first stage uses organic solvent to remove electrolyte, solvent, and binder; leaching of cathode carried by electrolyzing combines pyro- and hydrometallurgical methods

electrolyte and plastics removed through calcination; pyrometallurgical process used to recover alloy containing Co-Ni-Fe; hydrometallurgical process conducted to recover Co two-phase crushing line is designed; magnetic and other separation methods follow it; scrap then delivered to smelting plants and leaching combines mechanical methods including shredding, milling, and screening and hydrometallurgical methods including leaching and precipitation mechanical methods used as first stage; hydrometallurgical methods then used to obtain Co(OH)2 and Li3PO4

combines pyrometallurgical and hydrometallurgical technologies; spent LIBs are fed to a single shaft furnace; alloy containing Co and Ni from furnace further processed through leaching; Li and Al mainly exist in the slag and need to be further treated through hydrometallurgical technologies first stage is sortation techniques; rough crushed products then disposed by pyrolysis pretreatment, crushing, and sieving spent LIBs stored and shredded under CO2 atmosphere; scrap then neutralized by moist air and further treated with hydrometallurgical process scrap processed in a rotary hearth furnace and further refined in an electric arc furnace

details of technology

Table 4. Summary of Current LIB Recycling Industrial Technologies Throughout the World120,128,129

cathode material, Co3O4

metal powder CoO, Li2CO3 Co(OH)2, Li3PO4 Co alloy, Li2CO3 LiOH, CoO alloy (Co/ Ni/Cu) cathode powder CoO, Li salt Co powder

alloy (Co/ Ni/Fe) CoO

CoCl2

main end products

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Figure 7. Percentage of spent LIBs recycled by different technologies based on the (a) quantity of companies (30 companies) and (b) annual processing capacity of some of these companies (twelve companies); (c) flow-sheet of main processes used in the industry.

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DISCUSSION First, it is very interesting to note that, in comparison with the inorganic leachants, there are relatively few organic leachants recently chosen as leaching media to conduct the extraction process even though they are regarded as green reagents. In most reports about solvent extraction, precipitation, or regeneration technology, the leachate are from an inorganic leaching process. Among them, H2SO4 is the most frequent leachant. Organic reagents can avoid the problems associated with inorganic leachants, such as triggering air pollution, rigorous requirements of equipment, and difficulty in recycling leaching reagents. However, the research results have shown that the organic leaching can only conduct well with a low solid-to-liquid ratio, which decreases the concentration of Li+ in leachate and limits the treatment capacity for industrial production. A leachate with low concentration of Li+ is difficult to produce high-purity lithium compounds and needs to be concentrated. Moreover, all of these leaching processes need to be followed by solvent extraction or precipitation, in which the loss of Li is serious, to obtain the pure production of Ni/Co/ Mn or compounds. For example, when D2EHPA is used to extract Ni and Co, 20% Li will be coextracted.130 The loss of Li is nearly 17% in removing Ca and Mg by NaF.118 Therefore, all of these leaching reagents have their own limitations for recovering valuable metals from spent LIBs in a cost-effectively and environmentally friendly way. Selectively extracting target metals with a hydrometallurgical process from mines or electronic wastes has been proved to be feasible in many prior research studies. It is regarded as a promising approach to change the current situation in recycling spent LIBs.131 Gao et al.132 achieved the selective extraction of Al and Li from LiNi1/3Co1/3Mn1/3O2 cathode scrap using formic acid as leaching reagent. It was found that the selectivity of Al was more than 95% with no Al(OH)3 phase existing in the Ni/Co/ Mn hydroxide precipitate. Meanwhile, the relatively low solubilities of Co(COOH)2, Ni(COOH)2, and Mn(COOH)2 compared with that of Li(COOH)2 contributes to the spontaneous separation of Ni/Co/Mn and Li. As Zheng et al.73 reported, the ammonia-ammonium sulfate solution with reductant could also achieve the selective leaching of Li, Ni, and Co from Li(Ni1/3Co1/3Mn1/3)O2 cathode scraps. However, the optimal solid-to-liquid ratio in the alkali system was so small that the subsequent extraction approaches were hard to conduct. Li et al.133 reported the selective leaching of Li from spent LiFePO4 through H2SO4 at a low concentration, which

was much better than the traditional leaching with a high concentration of H2SO4 and a large consumption of H2O2. In consideration of the increasing price of lithium carbonate in recent years, it is a quite significant direction to research the selective extraction of Li. Of course, the best outcome is that we can achieve recovery of single metal element from spent LIBs or other waste and leave the other metals in solid waste.15 Second, with respect to energy consumption, data of the hydrometallurgical process, intermediate physical method from Toxco, direct physical process from OnTo Technology, and pyrometallurgical process from Umicore introduced by Dunn et al.134,135 have also been estimated. For simplicity, Figures 8 and

Figure 8. Estimated energy consumption for LiCoO2 and LiMn2O4 production via different automotive battery recycling processes (energy consumption during virgin LiMn2O4 production in Nevada and Chile is from Dunn et al;134 energy consumption during virgin LiCoO2 production is from Kushnir and Sandén136).

9 only summarize the results of energy consumption from Dunn et al.,134,135 in which the estimate is based on the GREET model proposed by Argonne National Laboratory.77 Note that the energy consumption of recycling LiCoO2 through some processes is not directly shown in the article. The estimate of missing data follows the mechanism introduced by Dunn et al.135 For example, the production of the intermediate recycling process is Li2CO3. We estimate the energy consumption of LiCoO2 of the intermediate recycling process by adding the 1514


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whole process to produce LiMn2O4 may be possible when recycled LiMn2O4, Al, and Cu are used as raw materials as shown in Figure 9.134 Furthermore, a reduction in total energy consumption could be foreseeable if a closed-loop recycling scenario of LIBs is achieved. Because of the lack of relevant data, the literature seldom reports the energy consumption of other methods, such as the regenerated and biometallurgical methods. However, it is important to estimate the energy consumption, which will make a difference in future work. Third, the “3R” principles in green chemistry should be emphasized in recycling processes. Though current research mainly focuses on the recovery and regeneration, which are the last principles of “3R”, it is still hard to implement recently developed technologies in industrial production because of the low economic benefit and secondary pollution. For easiness of implementing the proposed process in industrial production, how simple the process or route is plays a pivotal role. It is widely known that a loss coefficient needs to be considered during industrial production. The longer and more complex a technology is, the more valuable metal will be lost and will result in less economic benefit, such as the loss of Li in organic phase.130 Therefore, the best method is to observe the “reuse” principle, which requires that the waste should be reused as its original purpose or reused as a component to fulfill a different function. In this principle, the waste is directly recycled or undergoes a repair process before being recycled. The reuse or regeneration methods are all short routes to recycle materials with little loss and low energy consumption. With respect to legislation, successfully making “3R” ideology into integrated utilization and recycling the valuable components in spent LIBs not only rely on technical breakthroughs made from industry and research organizations but also rely on government support, public awareness of environmental protection, manufacturing innovation, and management of LIBs from the cradle to the grave. The recycling efficiency and complexity of technology mainly depend on the complexity of spent materials. With an excellent collection system and wellknown classification method, the recycling process will become

Figure 9. Energy consumption (MJ/kg battery) of using recycled aluminum, copper, cathode materials, or all of them to fabricate batteries used in electric vehicles (solid back line is consumption of using virgin materials134).

energy consumption of producing virgin Co3O4 and recycling Li2CO3 following the chemical reaction of producing LiCoO2. Figure 8 illustrates that the energy intensities of recycling materials are less than producing virgin materials. With the consumption of citric acid and hydrogen peroxide included in the overall process, the energy consumption of the hydrometallurgical process is tremendous, whereas the process itself is not energy intensive. Moreover, an external process of the hydrometallurgical method, adding Mn2O3 to react with Li2CO3 to form LiMn2O4 in the end, also makes the energy consumption of the hydrometallurgical process more than that of other processes. Figure 9 contains estimates of the energy consumption and greenhouse gas (GHG) in total LiMn2O4 production with different recycled materials. It indicates that, the more recycled materials are used in production, the less energy will be needed in the overall process. Therefore, the reduction of energy consumption and GHG emissions in the Table 5. Regulations Relevant to Spent Batteries in China regulation title

year

policy on pollution prevention techniques from municipal solid waste

2000

main related content

policy on pollution prevention techniques from hazardous wastes

2001

policy on pollution prevention techniques from waste batteries

2003

discarded household appliances and electronic products pollution control technology policy auto product recovery and usage technology policy

2006

measures for the control of environmental pollution of electronic waste emission standard of pollutants for battery industry technical requirement for environmental labeling products battery policy on recycling technology of electric vehicle power battery (ask for comment) policy on recycling technology of electric vehicle power battery (2015)

2008 2013 2013 2015

industry norms of utilizing waste power battery from new energy vehicles; interim measures for managing industry norms of utilizing waste power battery from new energy vehicles policy on pollution prevention techniques from waste batteries (ask for comment)

2016

2006

2016

2016

lead the development and improvement of managing and disposing municipal solid waste lead the development and improvement of managing and disposing hazardous wastes require manufacturers to collect spent batteries; aim to encourage the development of managing and recycling technology of spent batteries and reduce pollution aim to reduce the pollution of electric waste require the automobile production enterprises to establish the collection and treatment of power batteries produced by them or send the spent power batteries to a special company who can dispose of them cover stipulations about collecting, disposing, and managing electric waste stipulate the quantity of wastewater and gas from the industry add the requirements about design, product, and recycle process lead the development of managing and disposing spent electric vehicles power batteries emphasize the fact that the responsibility of recycling spent power batteries belongs to the battery manufacturers give the requirements about the factory size, equipment, technology, and energy consumption of recycling industries enlarge the managing scope of spent batteries; encourage establishing a collecting system and researching new recycling technology

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ACS Sustainable Chemistry & Engineering much simpler. As a result, the simplified process will lead to an improved efficiency of recovery, reduction of cost, and increased profit margin. For a good collection system to be established, both the collection mechanism itself and enforcement of legislative policies are important. Fortunately, with the problem of spent LIBs gaining more and more public awareness, governments realize the importance of setting up a comprehensive collection system. The relevant laws and policies have been established to encourage the development of recycling spent LIBs. As seen in Table 5, laws relevant to the collection and disposal of spent batteries have been constantly increasing from 2000 to now. In the early years, the regulations of recycling spent LIBs were covered as a small aspect of the laws for disposing of solid waste. Afterward, some comprehensive policies about spent batteries, mainly pointing to lead acid battery, have been established. In recent years, special laws for spent LIBs have been established, as the severity of pollution caused by battery leakage is spreading quickly and widely. Given that these legislative policies have already been nailed in, the public is less prone to ignore pollution caused by battery leakage.

spent LIBs, which are hazardous for soil, water, and living organisms on Earth. • Not restricting the recycling process of spent LIBs and comprehensive and holistic views from the cradle to the grave in designing, manufacturing, and recycling LIBs needs to be addressed. Last but not the least, a global homogenized mechanism in manufacturing, classification, collection, and recycling will significantly reduce the complexity of raw material, which in turn minimizes the energy consumption of the recycling process. All of these aspects have a lasting influence on achieving economic and eco-friendly recycling of spent LIBs.

CONCLUSIONS AND OUTLOOK Globally, several companies, including AEA Technology (U.K.), SNAM (France), Toxco (Canada), and Umicore (Belgium), have established complete production lines to recycle metals from spent LIBs.55 They are mainly focusing on employing pyrometallurgical or hydrometallurgical methods or a combination of them both. Concerning economic benefit, traditional metallurgical processes (a long process including pretreatment, leaching, and purifying) have little competitiveness in comparison with newer shorter processes, such as selective extraction, regeneration, and repairing processes. Though many reports researched the recycling technologies of metals from spent LIBs, few of them have achieved costeffectiveness on an industrial scale. Meanwhile, there is no commercial technology to achieve the recycling of waste mixed with different cathodes. Many mechanisms of physical and chemical changes in the recycling process need to be deeply explored. A complete system of recycling LIBs needs to be discussed and established. For future research in the recycling of spent LIBs, we believe that it should focus on the following aspects: • Whether the lab-scale technologies have industrial application prospects and how to scale them step-by-step are of primary importance. • The mechanisms of the leaching process are still inconclusive. Significant work still needs to be done to guide the selection of leaching reagent and operating conditions. For example, changes in the crystal structure of the leaching process need to be deeply researched. It will be very helpful for providing insight into the reaction mechanism during leaching. • Selective leaching of most of the valuable metals from the spent LIBs has not been achieved yet. Relative research studies should be strengthened in the future. • Most studies of disposing spent LIBs only focused on the kinetics and influence of operational parameters on leaching process, whereas more efforts need to be paid for establishing a complete evaluation system in which more critical factors, such as energy consumption of the whole process, could be considered. • Furthermore, efforts also need to be concentrated on enhancing the collecting efficiency and reducing the landfill of

Notes

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; Tel: +86 10 82544844; Fax: +86 10 82544845. ORCID

Hongbin Cao: 0000-0001-5968-9357 Zhi Sun: 0000-0001-7183-0587

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The authors declare no competing financial interest. Biographies

Weiguang Lv is a doctoral student in the Institute of Process Engineering, Chinese Academy of Sciences. He received his B.Sc. degree in metallurgical engineering (Central South University). His current research focuses on efficient recovery of valuable metal from spent LIBs.

Dr. Zhonghang Wang is a postdoctoral researcher at the Institute of Process Engineering, Chinese Academy of Sciences (IPE, CAS). He received his B.Sc. degree in chemical engineering and technology (Central South University), and Ph. D. in chemical technology (University of Chinese Academy of Sciences). He has been working on electrometallurgy and molten salt electrochemistry for many years. His 1516


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chief scientist, she had presided over the first National Sci-Tech Project and the first 863 Project on cleaner process research. Furthermore, she proposed a revolutionary green process for highly efficient and clean conversion of mineral resources with submolten salt medium. Professor Zhang has achieved second and third prizes of National Technical Invention Awards, second and third prizes of National Sci-Tech Progress Awards, and first prize of the Sci-Tech Progress Awards of CAS (3 times). Professor Zhang has published more than 170 papers and edited 9 books. She has also submitted 34 China invention patent applications with 10 granted. Under her direction, 48 graduates have obtained their master’s or Ph.D. degrees since 1990.

current research focuses on efficient recovery of valuable metals from e-waste and the electroconversion of e-waste to high-value products.

Dr. Hongbin Cao is a professor at the Institute of Process Engineering, Chinese Academy of Sciences, deputy director of the National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, and director of Beijing Engineering Research Center of Process Pollution Control. His research interest is the whole process control of industrial pollution: theory, technology, and application. Dr. Cao has published over 100 papers and applied over 60 patents including 5 international. He won second prize for the State Technological Innovation Award (2013), first prize for the Environmental Protection Science and Technology Award (2012), and first prize for the Science and Technology Invention Award of Liaoning province (2011). He is also the holder of National High-level personnel of special support program (2013) and of the National Science Fund for Distinguished Young Scholars of China (2014).

Dr. Zhi Sun is a professor at the Institute of Process Engineering, Chinese Academy of Sciences. He received his B.Sc. degree in metallurgical engineering (University of Science and Technology Beijing), M.Sc. degree in chemical engineering (Chinese Acadamy of Sciences), and Ph.D. in materials engineering (KU Leuven, Belgium). He has been working as a postdoctoral researcher at the University of Queensland, Australia, and as a senior researcher at Delft University of Technology, The Netherlands. His current research focuses on electronic waste treatment, sustainable process design for metal recycling, and green design of electronic products. He is member of the Chinese association of waste battery treatment. Dr. Sun has coauthored more than 50 publications and 5 patents. He is also an editorial board member of two international journals.

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ACKNOWLEDGMENTS This work was financially supported by the National Key Research and Development Program of China (2017YFB0403300/2017YFB043305), Beijing Science and Technology Program (No. Z171100002217028), the National Natural Science Foundation of China (No. 51425405 and L1624051), and the National Science and Technology Support Plan Project (2015BAB02B05).

Dr. Yong sun is Technical Support Engineer within the School of Engineering’s Technical Support team. He received his Ph.D. in biochemical engineering in China and M.Sc degree of engineering science at Monash University. His current research focuses on expertise in Fischer−Tropsch synthesis, heterogeneous catalysis, hydrometallurgy, gas separation and storage, and fluidization. Dr. Sun has coauthored more than 50 publications.

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REFERENCES

(1) Georgi-Maschler, T.; Friedrich, B.; Weyhe, R.; Heegn, H.; Rutz, M. Development of a recycling process for Li-ion batteries. J. Power Sources 2012, 207, 173−182. (2) Jaskula, B. W. Lithium. In Minerals Yearbook, Survey, U. S. G., Ed.; United States Geological Survey: Reston, VA, 2014. (3) http://www.chyxx.com/industry/201611/470783.html. (4) http://www.chyxx.com/industry/201703/500669.html. (5) Sun, X.; Hao, H.; Zhao, F.; Liu, Z. Tracing global lithium flow: A trade-linked material flow analysis. Resources, Conservation and Recycling. 2017, 124, 50−61. (6) Zeng, X.; Li, J.; Liu, L. Solving spent lithium-ion battery problems in China: Opportunities and challenges. Renewable Sustainable Energy Rev. 2015, 52, 1759−1767.

Professor Zhang, working at the Institute of Process Engineering, Chinese Academy of Sciences (CAS), is one of the chief scientists first entering the field of green process engineering in China and is currently engaged in fundamental and application research on green process engineering and environmental control technology. As the 1517


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ACS Sustainable Chemistry & Engineering (7) Zeng, X.; Li, J.; Singh, N. Recycling of Spent Lithium-Ion Battery: A Critical Review. Crit. Rev. Environ. Sci. Technol. 2014, 44 (10), 1129−1165. (8) Xu, J.; Thomas, H. R.; Francis, R. W.; Lum, K. R.; Wang, J.; Liang, B. A review of processes and technologies for the recycling of lithium-ion secondary batteries. J. Power Sources 2008, 177 (2), 512− 527. (9) Ku, H.; Jung, Y.; Jo, M.; Park, S.; Kim, S.; Yang, D.; Rhee, K.; An, E. M.; Sohn, J.; Kwon, K. Recycling of spent lithium-ion battery cathode materials by ammoniacal leaching. J. Hazard. Mater. 2016, 313, 138−46. (10) Sun, Z.; Cao, H.; Zhang, X.; Lin, X.; Zheng, W.; Cao, G.; Sun, Y.; Zhang, Y. Spent lead-acid battery recycling in China - A review and sustainable analyses on mass flow of lead. Waste Manage. 2017, 64, 190−201. (11) Nitta, N.; Wu, F.; Lee, J. T.; Yushin, G. Li-ion battery materials: present and future. Mater. Today 2015, 18 (5), 252−264. (12) Kraytsberg, A.; Ein-Eli, Y. Higher, stronger, better···A review of 5 V cathode materials for advanced lithium-ion batteries. Advanced Energy Materials. 2012, 2 (8), 922−939. (13) http://info.worldbank.org/governance/wgi/index.aspx#home. (14) http://ec.europa.eu/growth/sectors/raw-materials/specificinterest/critical_en. (15) Sun, Z.; Cao, H.; Xiao, Y.; Sietsma, J.; Jin, W.; Agterhuis, H.; Yang, Y. Toward sustainability for recovery of critical metals from electronic waste: The Hydrochemistry Processes. ACS Sustainable Chem. Eng. 2017, 5 (1), 21−40. (16) https://price.metal.com. (17) http://www.chyxx.com/industry/201704/514553.html. (18) http://www.chyxx.com/industry/201612/475004.html. (19) http://www.chyxx.com/research/201611/465155.html. (20) http://www.chyxx.com/industry/201707/543308.html. (21) http://www.chyxx.com/industry/201608/439335.html. (22) Goonan, T. G. Lithium Use in Batteries; U.S. Department of the Interior, U.S. Geological Survey: Reston, VA, 2012; https://pubs.usgs. gov/circ/1371/pdf/circ1371_508.pdf. (23) Swain, B. Cost effective recovery of lithium from lithium ion battery by reverse osmosis and precipitation: a perspective. J. Chem. Technol. Biotechnol. 2017, DOI: 10.1002/jctb.5332. (24) Lithium-Ion Battery Market Analysis By Product (Lithium Cobalt Oxide, Lithium Iron Phosphate, NCA, LMO, LTO, Lithium Nickel Manganese Cobalt (NMC)), By Application, And Segment Forecasts, 2014−2025; GVR-1-68038-668-4; Grand view research: San Francisco, CA, 2017; http://www.grandviewresearch.com/industryanalysis/thermal-energy-storage-market. (25) https://imformed.com/li-ion-battery-recycling-no-worries-forraw-material-suppliersyet/. (26) https://www.variantmarketresearch.com/report-categories/ semiconductor-electronics/lithium-ion-battery-market. (27) Nie, H.; Xu, L.; Song, D.; Song, J.; Shi, X.; Wang, X.; Zhang, L.; Yuan, Z. LiCoO2: Recycling from spent batteries and regeneration with solid state synthesis. Green Chem. 2015, 17 (2), 1276−1280. (28) Zhang, X.; Xue, Q.; Li, L.; Fan, E.; Wu, F.; Chen, R. Sustainable recycling and regeneration of cathode scraps from industrial production of lithium-ion batteries. ACS Sustainable Chem. Eng. 2016, 4 (12), 7041−7049. (29) Song, D.; Wang, X.; Zhou, E.; Hou, P.; Guo, F.; Zhang, L. Recovery and heat treatment of the Li(Ni1/3Co1/3Mn1/3)O2 cathode scrap material for lithium ion battery. J. Power Sources 2013, 232, 348− 352. (30) Chen, J.; Li, Q.; Song, J.; Song, D.; Zhang, L.; Shi, X. Environmentally friendly recycling and effective repairing of cathode powders from spent LiFePO4 batteries. Green Chem. 2016, 18 (8), 2500−2506. (31) Bian, D.; Liu, S.; Sun, Y.; Yang, Z. Recycle of LiFePO4 cathode materials from spent lithium ion batteries and the electrochemical performance. Journal of the Chinese Ceramic Society. 2015, 43 (11), 1511−1516.

(32) Song, X.; Hu, T.; Liang, C.; Long, H. L.; Zhou, L.; Song, W.; You, L.; Wu, Z. S.; Liu, J. W. Direct regeneration of cathode materials from spent lithium iron phosphate batteries using a solid phase sintering method. RSC Adv. 2017, 7 (8), 4783−4790. (33) Zhu, S.; He, W.; Li, G.; Zhou, X.; Huang, J.; Zhang, X. Recovering copper from spent Lithium ion battery by a mechanical separation process. IEEE Shanghai,China 2011, 2, 1008−1012. (34) Shin, S. M.; Kim, N. H.; Sohn, J. S.; Yang, D. H.; Kim, Y. H. Development of a metal recovery process from Li-ion battery wastes. Hydrometallurgy 2005, 79 (3−4), 172−181. (35) Granata, G.; Pagnanelli, F.; Moscardini, E.; Takacova, Z.; Havlik, T.; Toro, L. Simultaneous recycling of nickel metal hydride, lithium ion and primary lithium batteries: Accomplishment of European Guidelines by optimizing mechanical pre-treatment and solvent extraction operations. J. Power Sources 2012, 212, 205−211. (36) Paulino, J. F.; Busnardo, N. G.; Afonso, J. C. Recovery of valuable elements from spent Li-batteries. J. Hazard. Mater. 2008, 150 (3), 843−9. (37) He, L.; Sun, S.; Mu, Y.; Song, X.; Yu, J. Recovery of lithium, nickel, cobalt, and manganese from spent lithium-ion batteries using Ltartaric acid as a leachant. ACS Sustainable Chem. Eng. 2017, 5 (1), 714−721. (38) Song, D.; Wang, X.; Nie, H.; Shi, H.; Wang, D.; Guo, F.; Shi, X.; Zhang, L. Heat treatment of LiCoO2 recovered from cathode scraps with solvent method. J. Power Sources 2014, 249, 137−141. (39) Pant, D.; Dolker, T. Green and facile method for the recovery of spent Lithium Nickel Manganese Cobalt Oxide (NMC) based Lithium ion batteries. Waste Manage. 2016, 60, 689−695. (40) Yang, Y.; Zheng, X.; Cao, H.; Zhao, C.; Lin, X.; Ning, P.; Zhang, Y.; Jin, W.; Sun, Z. A Closed-Loop Process for Selective Metal Recovery from Spent Lithium Iron Phosphate Batteries through Mechanochemical Activation. ACS Sustainable Chem. Eng. 2017, 5 (11), 9972−9980. (41) Wang, M.; Zhang, C.; Zhang, F. An environmental benign process for cobalt and lithium recovery from spent lithium-ion batteries by mechanochemical approach. Waste Manage. 2016, 51, 239−44. (42) Guan, J.; Li, Y.; Guo, Y.; Su, R.; Gao, G.; Song, H.; Yuan, H.; Liang, B.; Guo, Z. Mechanochemical process enhanced cobalt and lithium recycling from wasted lithium-ion batteries. ACS Sustainable Chem. Eng. 2017, 5 (1), 1026−1032. (43) Saeki, S.; Lee, J.; Zhang, Q.; Saito, F. Co-grinding LiCoO2 with PVC and water leaching of metal chlorides formed in ground product. Int. J. Miner. Process. 2004, 74, S373−S378. (44) Vanitha, M.; Balasubramanian, N. Waste minimization and recovery of valuable metals from spent lithium-ion batteries − a review. Environ. Technol. Rev. 2013, 2 (1), 101−115. (45) Chagnes, A.; Pospiech, B. A brief review on hydrometallurgical technologies for recycling spent lithium-ion batteries. J. Chem. Technol. Biotechnol. 2013, 88 (7), 1191−1199. (46) Hanisch, C.; Loellhoeffel, T.; Diekmann, J.; Markley, K. J.; Haselrieder, W.; Kwade, A. Recycling of lithium-ion batteries: a novel method to separate coating and foil of electrodes. J. Cleaner Prod. 2015, 108, 301−311. (47) Sun, L.; Qiu, K. Vacuum pyrolysis and hydrometallurgical process for the recovery of valuable metals from spent lithium-ion batteries. J. Hazard. Mater. 2011, 194, 378−84. (48) Li, J.; Zhao, R.; He, X.; Liu, H. Preparation of LiCoO2 cathode materials from spent lithium−ion batteries. Ionics 2009, 15 (1), 111− 113. (49) He, L.; Sun, S.; Song, X.; Yu, J. Recovery of cathode materials and Al from spent lithium-ion batteries by ultrasonic cleaning. Waste Manage. 2015, 46, 523−8. (50) Tan, Q.; Li, J. Recycling metals from wastes: a novel application of mechanochemistry. Environ. Sci. Technol. 2015, 49 (10), 5849−61. (51) Wang, M.; Zhang, C.; Zhang, F. Recycling of spent lithium-ion battery with polyvinyl chloride by mechanochemical process. Waste Manage. 2017, 67, 232−239. 1518


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and ascorbic acid mixture to recover Co. Hydrometallurgy 2016, 161, 54−57. (70) Nayaka, G. P.; Pai, K. V.; Santhosh, G.; Manjanna, J. Recovery of cobalt as cobalt oxalate from spent lithium ion batteries by using glycine as leaching agent. J. Environ. Chem. Eng. 2016, 4 (2), 2378− 2383. (71) Chen, X.; Fan, B.; Xu, L.; Zhou, T.; Kong, J. An atom-economic process for the recovery of high value-added metals from spent lithium-ion batteries. J. Cleaner Prod. 2016, 112, 3562−3570. (72) Li, L.; Zhai, L.; Zhang, X.; Lu, J.; Chen, R.; Wu, F.; Amine, K. Recovery of valuable metals from spent lithium-ion batteries by ultrasonic-assisted leaching process. J. Power Sources 2014, 262, 380− 385. (73) Zheng, X.; Gao, W.; Zhang, X.; He, M.; Lin, X.; Cao, H.; Zhang, Y.; Sun, Z. Spent lithium-ion battery recycling - Reductive ammonia leaching of metals from cathode scrap by sodium sulphite. Waste Manage. 2017, 60, 680−688. (74) Bertuol, D. A.; Machado, C. M.; Silva, M. L.; Calgaro, C. O.; Dotto, G. L.; Tanabe, E. H. Recovery of cobalt from spent lithium-ion batteries using supercritical carbon dioxide extraction. Waste Manage. 2016, 51, 245−51. (75) Liu, K.; Zhang, F. Innovative leaching of cobalt and lithium from spent lithium-ion batteries and simultaneous dechlorination of polyvinyl chloride in subcritical water. J. Hazard. Mater. 2016, 316, 19−25. (76) Takacova, Z.; Havlik, T.; Kukurugya, F.; Orac, D. Cobalt and lithium recovery from active mass of spent Li-ion batteries: Theoretical and experimental approach. Hydrometallurgy 2016, 163, 9−17. (77) https://greet.es.anl.gov/. (78) Barik, S. P.; Prabaharan, G.; Kumar, L. Leaching and separation of Co and Mn from electrode materials of spent lithium-ion batteries using hydrochloric acid: Laboratory and pilot scale study. J. Cleaner Prod. 2017, 147, 37−43. (79) Zhang, P.; Yokoyama, T.; Itabashi, O.; Suzuki, T. M.; Inoue, K. Hydrometallurgical process for recovery of metal values from spent lithium-ion secondary batteries. Hydrometallurgy 1998, 47 (2−3), 259−271. (80) Huang, Y.; Han, G.; Liu, J.; Chai, W.; Wang, W.; Yang, S.; Su, S. A stepwise recovery of metals from hybrid cathodes of spent Li-ion batteries with leaching-flotation-precipitation process. J. Power Sources 2016, 325, 555−564. (81) Swain, B.; Jeong, J.; Lee, J.-c.; Lee, G.-H.; Sohn, J.-S. Hydrometallurgical process for recovery of cobalt from waste cathodic active material generated during manufacturing of lithium ion batteries. J. Power Sources 2007, 167 (2), 536−544. (82) Gratz, E.; Sa, Q.; Apelian, D.; Wang, Y. A closed loop process for recycling spent lithium ion batteries. J. Power Sources 2014, 262, 255−262. (83) Meshram, P.; Pandey, B. D.; Mankhand, T. R. Hydrometallurgical processing of spent lithium ion batteries (LIBs) in the presence of a reducing agent with emphasis on kinetics of leaching. Chem. Eng. J. 2015, 281, 418−427. (84) Jha, M. K.; Kumari, A.; Jha, A. K.; Kumar, V.; Hait, J.; Pandey, B. D. Recovery of lithium and cobalt from waste lithium ion batteries of mobile phone. Waste Manage. 2013, 33 (9), 1890−1897. (85) Pinna, E. G.; Ruiz, M. C.; Ojeda, M. W.; Rodriguez, M. H. Cathodes of spent Li-ion batteries: Dissolution with phosphoric acid and recovery of lithium and cobalt from leach liquors. Hydrometallurgy 2017, 167, 66−71. (86) Chen, X.; Ma, H.; Luo, C.; Zhou, T. Recovery of valuable metals from waste cathode materials of spent lithium-ion batteries using mild phosphoric acid. J. Hazard. Mater. 2017, 326, 77−86. (87) Lee, C. K.; Rhee, K.-I. Preparation of LiCoO2 from spent lithium-ion batteries. J. Power Sources 2002, 109 (1), 17−21. (88) Sun, L.; Qiu, K. Organic oxalate as leachant and precipitant for the recovery of valuable metals from spent lithium-ion batteries. Waste Manage. 2012, 32 (8), 1575−1582.

(52) Nife, A. B. S.; Landskrona, S.; Melin, A. L.; Svensson, V. H. Process for the recovery of metals from the scrap from nickel− cadmium electric storage batteries. US Patent 4401463, 1983. (53) Espinosa, D. C. R.; Bernardes, A. M.; Tenório, J. A. S. An overview on the current processes for the recycling of batteries. J. Power Sources 2004, 135 (1−2), 311−319. (54) Meshram, P.; Pandey, B. D.; Mankhand, T. R. Recovery of valuable metals from cathodic active material of spent lithium ion batteries: Leaching and kinetic aspects. Waste Manage. 2015, 45, 306− 13. (55) Meshram, P.; Pandey, B. D.; Mankhand, T. R. Extraction of lithium from primary and secondary sources by pre-treatment, leaching and separation: A comprehensive review. Hydrometallurgy 2014, 150, 192−208. (56) Ren, G.; Xiao, S.; Xie, M.; Pan, B.; Fan, Y.; Wang, F.; Xia, X. Recovery of valuable metals from spent lithium ion batteries by smelting reduction based on MnO-SiO2-Al2O3 slag system. In Advances in Molten Slags, Fluxes, and Salts: Proceedings of the 10th International Conference on Molten Slags, Fluxes and Salts; Reddy, R. G.; Chaubal, P.; Chris Pistorius, P.; Pal, U., Eds.; Springer, Cham, 2016; pp 211−218. (57) Xiao, J.; Li, J.; Xu, Z. Novel Approach for in Situ Recovery of Lithium Carbonate from Spent Lithium Ion Batteries Using Vacuum Metallurgy. Environ. Sci. Technol. 2017, 51, 11960. (58) Xiao, J.; Li, J.; Xu, Z. Recycling metals from lithium ion battery by mechanical separation and vacuum metallurgy. J. Hazard. Mater. 2017, 338, 124−131. (59) Li, J.; Wang, G.; Xu, Z. Environmentally-friendly oxygen-free roasting/wet magnetic separation technology for in situ recycling cobalt, lithium carbonate and graphite from spent LiCoO2/graphite lithium batteries. J. Hazard. Mater. 2016, 302, 97−104. (60) Garcia, E. M.; Tarôco, H. A.; Matencio, T.; Domingues, R. Z.; dos Santos, J. A. F.; Ferreira, R. V.; Lorençon, E.; Lima, D. Q.; de Freitas, M. B. J. G. Electrochemical recycling of cobalt from spent cathodes of lithium-ion batteries: its application as supercapacitor. J. Appl. Electrochem. 2012, 42 (6), 361−366. (61) Garcia, E. M.; Tarôco, H. A.; Matencio, T.; Domingues, R. Z.; dos Santos, J. A. F.; de Freitas, M. B. J. G. Electrochemical recycling of cobalt from spent cathodes of lithium−ion batteries: its application as coating on SOFC interconnects. J. Appl. Electrochem. 2011, 41 (11), 1373−1379. (62) Garcia, E. M.; Santos, J. S.; Pereira, E. C.; Freitas, M. B. J. G. Electrodeposition of cobalt from spent Li-ion battery cathodes by the electrochemistry quartz crystal microbalance technique. J. Power Sources 2008, 185 (1), 549−553. (63) Granata, G.; Moscardini, E.; Pagnanelli, F.; Trabucco, F.; Toro, L. Product recovery from Li-ion battery wastes coming from an industrial pre-treatment plant: Lab scale tests and process simulations. J. Power Sources 2012, 206, 393−401. (64) Ferreira, D. A.; Prados, L. M. Z.; Majuste, D.; Mansur, M. B. Hydrometallurgical separation of aluminium, cobalt, copper and lithium from spent Li-ion batteries. J. Power Sources 2009, 187 (1), 238−246. (65) Joulié, M.; Laucournet, R.; Billy, E. Hydrometallurgical process for the recovery of high value metals from spent lithium nickel cobalt aluminum oxide based lithium-ion batteries. J. Power Sources 2014, 247, 551−555. (66) Nayaka, G. P.; Pai, K. V.; Manjanna, J.; Keny, S. J. Use of mild organic acid reagents to recover the Co and Li from spent Li-ion batteries. Waste Manage. 2016, 51, 234−238. (67) Li, L.; Dunn, J. B.; Zhang, X. X.; Gaines, L.; Chen, R. J.; Wu, F.; Amine, K. Recovery of metals from spent lithium-ion batteries with organic acids as leaching reagents and environmental assessment. J. Power Sources 2013, 233, 180−189. (68) Zeng, X.; Li, J.; Shen, B. Novel approach to recover cobalt and lithium from spent lithium-ion battery using oxalic acid. J. Hazard. Mater. 2015, 295, 112−118. (69) Nayaka, G. P.; Pai, K. V.; Santhosh, G.; Manjanna, J. Dissolution of cathode active material of spent Li-ion batteries using tartaric acid 1519


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ACS Sustainable Chemistry & Engineering (89) Chen, X.; Luo, C.; Zhang, J.; Kong, J.; Zhou, T. Sustainable recovery of metals from spent lithium-ion batteries: a green process. ACS Sustainable Chem. Eng. 2015, 3 (12), 3104−3113. (90) Li, L.; Qu, W.; Zhang, X.; Lu, J.; Chen, R.; Wu, F.; Amine, K. Succinic acid-based leaching system: A sustainable process for recovery of valuable metals from spent Li-ion batteries. J. Power Sources 2015, 282, 544−551. (91) Ijadi Bajestani, M.; Mousavi, S. M.; Shojaosadati, S. A. Bioleaching of heavy metals from spent household batteries using Acidithiobacillus ferrooxidans: Statistical evaluation and optimization. Sep. Purif. Technol. 2014, 132, 309−316. (92) Mishra, D.; Kim, D. J.; Ralph, D. E.; Ahn, J. G.; Rhee, Y. H. Bioleaching of metals from spent lithium ion secondary batteries using Acidithiobacillus ferrooxidans. Waste Manage. 2008, 28 (2), 333−338. (93) Zeng, G.; Luo, S.; Deng, X.; Li, L.; Au, C. Influence of silver ions on bioleaching of cobalt from spent lithium batteries. Miner. Eng. 2013, 49, 40−44. (94) Chen, S.; Lin, J. Enhancement of metal bioleaching from contaminated sediment using silver ion. J. Hazard. Mater. 2009, 161 (2−3), 893−899. (95) Zeng, G.; Deng, X.; Luo, S.; Luo, X.; Zou, J. A copper-catalyzed bioleaching process for enhancement of cobalt dissolution from spent lithium-ion batteries. J. Hazard. Mater. 2012, 199−200, 164−169. (96) Xin, B.; Zhang, D.; Zhang, X.; Xia, Y.; Wu, F.; Chen, S.; Li, L. Bioleaching mechanism of Co and Li from spent lithium-ion battery by the mixed culture of acidophilic sulfur-oxidizing and iron-oxidizing bacteria. Bioresour. Technol. 2009, 100 (24), 6163−6169. (97) Xin, Y.; Guo, X.; Chen, S.; Wang, J.; Wu, F.; Xin, B. Bioleaching of valuable metals Li, Co, Ni and Mn from spent electric vehicle Li-ion batteries for the purpose of recovery. J. Cleaner Prod. 2016, 116, 249− 258. (98) Ren, W.; Li, P.; Geng, Y.; Li, X. Biological leaching of heavy metals from a contaminated soil by Aspergillus niger. J. Hazard. Mater. 2009, 167 (1−3), 164−169. (99) Bahaloo-Horeh, N.; Mousavi, S. M. Enhanced recovery of valuable metals from spent lithium-ion batteries through optimization of organic acids produced by Aspergillus niger. Waste Manage. 2017, 60, 666−679. (100) Horeh, N. B.; Mousavi, S. M.; Shojaosadati, S. A. Bioleaching of valuable metals from spent lithium-ion mobile phone batteries using Aspergillus niger. J. Power Sources 2016, 320, 257−266. (101) Niu, Z.; Zou, Y.; Xin, B.; Chen, S.; Liu, C.; Li, Y. Process controls for improving bioleaching performance of both Li and Co from spent lithium ion batteries at high pulp density and its thermodynamics and kinetics exploration. Chemosphere 2014, 109, 92−98. (102) Wang, F.; Sun, R.; Xu, J.; Chen, Z.; Kang, M. Recovery of cobalt from spent lithium ion batteries using sulphuric acid leaching followed by solid−liquid separation and solvent extraction. RSC Adv. 2016, 6 (88), 85303−85311. (103) Joo, S.-H.; Shin, D.; Oh, C.; Wang, J.-P.; Shin, S. M. Extraction of manganese by alkyl monocarboxylic acid in a mixed extractant from a leaching solution of spent lithium-ion battery ternary cathodic material. J. Power Sources 2016, 305, 175−181. (104) Zhao, J. M.; Shen, X. Y.; Deng, F. L.; Wang, F. C.; Wu, Y.; Liu, H. Z. Synergistic extraction and separation of valuable metals from waste cathodic material of lithium ion batteries using Cyanex272 and PC-88A. Sep. Purif. Technol. 2011, 78 (3), 345−351. (105) Jha, A. K.; Jha, M. K.; Kumari, A.; Sahu, S. K.; Kumar, V.; Pandey, B. D. Selective separation and recovery of cobalt from leach liquor of discarded Li-ion batteries using thiophosphinic extractant. Sep. Purif. Technol. 2013, 104, 160−166. (106) Darvishi, D.; Haghshenas, D. F.; Alamdari, E. K.; Sadrnezhaad, S. K.; Halali, M. Synergistic effect of Cyanex 272 and Cyanex 302 on separation of cobalt and nickel by D2EHPA. Hydrometallurgy 2005, 77 (3−4), 227−238. (107) Joo, S.-H.; Shin, D. j.; Oh, C.; Wang, J.-P.; Senanayake, G.; Shin, S. M. Selective extraction and separation of nickel from cobalt, manganese and lithium in pre-treated leach liquors of ternary cathode

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