A Critical Review and Analysis on the Recycling of Spent Lithium-Ion

Dec 13, 2017 - Dr. Yong sun is Technical Support Engineer within the School of Engineering's Technical Support team. He received his Ph.D. in biochemi...
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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 H.I. Sun ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03811 • Publication Date (Web): 13 Dec 2017 Downloaded from http://pubs.acs.org on December 14, 2017

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A critical review and analysis on the recycling of spent lithium-ion batteries W. Lva,b, Z. Wanga, H. Caoa, Y. Sunc, Y. Zhanga, Z. Suna*

2 a

3

National Engineering Laboratory for Hydrometallurgical Cleaner Production &

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Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190,

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China b

6 7

c

University of Chinese Academy of Sciences, Beijing 100190, China

Edith Cowan University School of Engineering, 270 Joondalup Drive Joondalup WA 6027

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Australia *Corresponding author: Z. Sun ([email protected])

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National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology

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Institute of Process Engineering, Chinese Academy of Sciences

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Tel: +86 10 82544844

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Fax: +86 10 82544845

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No. 1 Beierjie, Zhongguancun, Beijing, China

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ABSTRACT

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Recycling of spent lithium-ion-batteries (LIBs) has attracted significant attentions in recent

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years due to the increasing demand on corresponding critical metals/materials and growing

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pressure on environmental impact from solid waste disposal. A range of investigations have been

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carried out for recycling spent LIBs to obtain either battery materials or individual compounds. In

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order to enhance effective recovery of materials, physical pretreatment is usually applied to obtain

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different streams of waste materials ensuring efficient separation for further processing.

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Subsequently, a metallurgical process is used to extract metals or separate impurities from a

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specific waste stream so that the recycled materials or compounds can be further prepared by

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incorporating principles of materials engineering. In this review, the current status of spent LIBs

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recycling is summarized in view of the whole recycling process, especially focusing on the

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hydrometallurgy. In addition to understanding different hydrometallurgical technologies including

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acidic leaching, alkaline leaching, chemical precipitation and solvent extraction, the existing

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challenges for process optimization during the recycling are critically analyzed. Besides, the

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energy consumption of different processes is evaluated and discussed. It is expected that this

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research could provide a guideline for improvement of the spent LIBs recycling and this topic can

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be further stimulated for industrial realization.

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KEYWORDS: Spent LIBs; Pretreatment; Recycling; Environmental impact; Hydrometallurgy

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 INTRODUCITON

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The rapid growth of lithium-ion batteries (LIBs) used in portable electronic devices and

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electric vehicles requires significant amount of metal resources, especially lithium (Li) and cobalt

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(Co).1 According to the United States Geological Survey (USGS) and the China Industry

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Information Network, nearly 40% of Li and 42.46% Co were consumed in the production of

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batteries in 2014.2, 3 Specifically, the consumption of Co for power batteries has increased to 13.7%

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in 2016, and will hold the trend to 20.3% in 2018, because of the rapid development of electric

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vehicles.4 Meanwhile, the worldwide cobalt and lithium production only increase slightly in recent 2

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years. With current growth rate, a significant pressure is imposed on the supply side of cobalt and

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lithium.5 It is predicted that Co and Li will face serious shortage in the foreseeable future.

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Apart from the above-mentioned resource issues, the environmental and potential safety

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problems caused by spent LIBs are also substantial. If a spent LIB is directly discarded without

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proper treatment, the heavy metals like Co, Ni and Mn would contaminate soil and underground

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water. The electrolyte is easy to react with water to release harmful gas such as hydrogen fluoride

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(HF).6 Furthermore, during the cycle-life-period, Li tends to deposit on the anode due to

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overcharging or other improper usage. The deposited Li can react with water to release hydrogen

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gas (H2) and produce lithium hydroxide (LiOH). The residual electric power tends to cause

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explosion or fire accidents.7 Therefore, effective recycling of spent LIBs in view of the

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environmental and safety challenges is critical to ensure the sustainable development of this field.

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A single methodology is hard to be both cost-effective and environmental-friendly due to the

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complexity of raw materials. Therefore, a combination of physical and chemical approaches is

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widely adopted to recycle spent LIBs. Generally, physical methods are used to enhance the

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efficiency of recycling, and typically include dismantling, crushing, sieving, thermal and

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mechanochemical treatment.8 The chemical methods could be classified into pyrometallurgy and

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hydrometallurgy. In comparison with pyrometallurgical processes that usually undertook at high

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temperature, hydrometallurgical methods have obvious advantages, such as milder reaction

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conditions, more environmental-friendly, higher recovery efficiency of valuable metals especially

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Li.1,

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approaches to process spent LIBs.

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These advantages make hydrometallurgical methods as preferable and promising

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In this paper, the current status of lithium-ion batteries and recent developed strategies in

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pretreatment and metallurgical processes are systematically addressed, especially focusing on the

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hydrometallurgical processes. Furthermore, the challenges and deficiencies are analyzed and

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discussed. The regulations and legislation concerning spent LIBs management are also reviewed.

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The aim of review is to provide a general guideline of how spent LIBs recycling techniques can be

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improved.

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 DEVELOPMENT OF LITHIUM-ION BATTERIES

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At the beginning of 1990s, SONY manufactured the first ever commercial rechargeable LIBs

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in the world, consisting of a carbon anode and a LiCoO2 cathode.11 Since then, LIBs have been

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regarded as the most promising “green battery” for its high energy density, good design flexibility,

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and long lifespan in comparison with other types of batteries.12 To satisfy the further needs from

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the developing battery-powered devices, new type of LIBs have been extensively explored such as

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LiCoO2, LiNiO2, LiFePO4, the lithium nickel cobalt manganese (NCM) and the lithium nickel

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cobalt aluminum (NCA) in recent years. As seen in Figure 1 (a) and (b), the supply risk,

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circulability (CM) and market value of different cathode materials are evaluated based on the data

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from European Commission and Shanghai Metals Market.13-16 It demonstrates that (1) the

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recycling of LiCoO2 and NCM is slightly more important and profitable than other materials due

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to high cobalt content; (2) the high-cost and low circulability metals in the cathode materials are

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gradually replaced by low-cost and high circulability ones with lower supply risks in the last

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decades; (3) to decrease the pressure from supply risk, it is necessary to enhance the circulability

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of Co and research new cathode materials contain metals with little supply risk and high

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circulability. The production of LIBs from 2011 to 2016 remains a fast increase rate and is

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estimated to reach 169.09 GWh in 2018.

17-19

One of the reasons is the rapid development of

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electric vehicles, whose sales remain an excellent increasing in recent years.20 As important

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cathode materials of power battery, NCM, NCA and LiFePO4 will increase accordingly, resulting

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in a large amount of valuable metals such as Ni, Co, Li, awaiting being recycled through the waste

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stream.21 The components of LIBs waste will become much more complex without efficient

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classification and management. Nevertheless, data from the USGS indicated that at most 20% of

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the batteries available for recycling actually were recycled.22 Meanwhile, as the International

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Resources Panel reported that less than 1% lithium from spent LIBs was recycled in the world.23

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Contrast this with the increasing quantity of spent LIBs around the world, which is illustrated in

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Figure 1(c). Figure 1(c) also demonstrated the market revenue of LIBs in the USA from 2013 to

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2024. Besides, it is obvious that a positive correlation exists between the quantity of spent LIBs

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and the market size of LIBs. Therefore, from the market revenue of LIBs, the rising tendency of 4

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spent LIBs could be predicted.24, 25 The recycling of spent LIBs urgently need to be studied to

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establish a more economic and eco-friendly industrial process than current processes.

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Figure 1. Supply risk, (a) circulability (CM) and (b) market value of different cathode materials

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based on their metal content; (c) the estimation of spent LIBs in Canada, Mexico and the USA,

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2010-2030 and the market size in North America, USA, China and global world (The supply risk

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is based on the worldwide governance indicator, WGI; the quality of cathode materials only

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considers the quality of metals to evaluate the market value of cathode materials; the metal prices

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are the 1-month average price obtained from Shanghai Metals Market). 13-16, 25, 26

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 STATE-OF-THE-ART FOR SPENT LIBS RECYCLING

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The recycling processes of spent LIBs mainly include reuse, repair and recovery, among

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which the recovery process has drawn much attention, and will be introduced in detail in this

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section. In addition, the challenges of recycling processes will be analyzed in discussion aspect.

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The summary of current available treatment approaches is shown in Figure 2. Prior to processing,

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the spent LIBs should be firstly discharged to reduce the existence of Li metal and minimize the

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risk of explosion. A common method is using salt saturated solutions such as NaCl and Na2SO4 to

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discharge spent LIBs.27 The critical downside of this method is the emission of HF directly

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triggered by leakage of electrolyte into water, which is shown in Equation 1.

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LiPF6+H2 O→LiF+POF3+2HF↑

(0)

Spent LIBs Route 1 Route 2

Discharge

Pyrometallurgy

Pretreatment

Alloy(Co, Ni)

Cathode

Cu, Al foil, Plastic

Hydrometallurgy

Reuse

Hydrometallurgy

Recovery metal

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Route 3

Repair

Recovery cathode Recovery metal materials Recovery materials

Reusable products

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

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Afterwards, there are three recycling routes. Route 1 is the recycling or recovery process,

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which is composed of pretreatment (Sometimes, discharging process is also regarded as a

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pretreatment process), pyrometallurgical process and hydrometallurgical process. Route 2 is the

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repairing process. Route 3 is the reusing process, which mainly focuses on reusing Cu, Al foil and

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plastic that could be directly reused after disassembly. The profit of Route 3 largely depends on

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the efficiency of the disassembly process. As for Route 2, the advantage of it is shorting the 6

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recycling route to decrease the loss of valuable metals or materials and increase the profile of

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technologies. The general process is using NMP or other organic agent to separate cathode

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materials from Al foil and then achieves the repairing of spent cathode materials through

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calcination.28-30 It is not cost-effective to respectively recover Fe compounds or Li compounds

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from the spent LiFeO4 through conventional extraction technologies. Through repairing process, a

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green chemical and economic technology could be established.30-32 Additionally, the methods of

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reuse and repair are often ignored, though these processes could be very convenient and

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economical due to theirs short and effective flows.

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 Pretreatment method

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To enhance the efficiency of recycling materials, either mechanical or chemical pretreatment

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process is usually applied to make the different waste battery streams ready for subsequent

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processing. The more careful the pretreatment is applied, the more convenient the following

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process will be. The pretreatment processes mainly include dismantling, crushing, screening,

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thermal treatment, mechanochemical method, dissolution and so on. Some of valuable metals or

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materials, like Cu, Al and anode, are easy to recycle through pretreatment due to their significant

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different physical properties. Meanwhile, pretreatment methods play an important role in

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separating cathode materials from the Al foil and the organic binder, which will increase the

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complexity of leachate or make the waste hard to leach. For example, due to much better

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malleable properties of copper than graphite, the copper foils are easy to be separated from

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graphite carbon particles.33

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Shin et al.34 presented a single pretreatment technology, in which the spent LIBs were

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crushed directly into a suitable size and then a magnetic separation was conducted to collect the

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magnet. At the end of the process, a fine crushing and sieving were employed to eliminate Al foil,

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which will influence the leaching process. The removal of organic binder is important in

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pretreatment process. The common solutions are thermal treatment,35, 36 ultrasonic cleaning37 and

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organic reagent dissolution.38 Granata et al.35 used a two-rotors crushing and a splitter to achieve

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the separation of different materials. The organic binder was eliminated by thermal treatment at 7

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300 °C for 2 h. However, the decomposition of organic components like PVDF will release toxic

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and hazardous gases such as HF and heavy metal contaminated exhaust. Hence, using a system

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that consists of a cooler, a condensation chamber, carbon filters and bag filters as tail gas process

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plants to dispose gases appears to be necessary. Considering these disadvantages of the thermal

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treatment, researchers tried organic reagent to dissolve the organic binder. For example, the

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mixture of N,N-Dimethylformamide (DMF) and ethanol or N-methylpyrrolidone (NMP) is used as

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the dissolution reagent to dissolve PVDF, while the dissolution solvent itself is commonly known

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as toxicant.38 To offset the shortcoming of using toxic solvent, Pant and Dolker39 reported a green,

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non-toxic and environmental friendly solvent: citrus fruit juice (CFJ), as dissolution reagent.

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Nevertheless, the execution of the process involving CFJ normally requires a harsh condition

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(over 90 °C) to achieve effective dissolution.

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In addition to mechanical processing approaches, mechanochemical process is also an

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important technology which induces mechanically change of raw materials to influence their

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physical and chemical properties through high-energy ball-milling of materials.40-43 Meanwhile,

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some chemical reaction could be started during the grinding and rubbing accidentally. After that,

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the activity of materials will be improved. Therefore, meachaochemical technology is usually used

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in pretreatment processes to change or disrupt crystal structure of spent materials to enhance the

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leaching efficiency.

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methods, some technical hurdles and challenges still exist during the pretreatment, as summarized

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in Table 1. Furthermore, the disordered classification of spent batteries, complex disassembly

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processes and low efficiency of extracting valuable metals like lithium, still hinder the application

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of some pretreatment processes. Therefore, to meet the goal of recycling all valuable materials or

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metals in spent LIBs, pretreatment methods need to be combined with other physical and chemical

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processes.

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Though, many researches have been focused on the research of pretreatment

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Table 1

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The summary of advantages and disadvantages of different pretreatment methods Technology

Detail of methods

Advantages

Disadvantages

Ref.

Separate materials according to Mechanical separation

different physical properties, like

Simple and convenient

Cannot recycle all kinds of components in

density, conductivity, magnetic

operation

spent LIBs completely

44, 45

behavior, etc. Require high input of energy, cannot recover Remove organic additives and binders Thermal process via thermal treatment

Simple and convenient

organic compounds, and would cause serious

operation

exhaust pollution if no exhaust purification

46, 47

device is equipped Dissolve the adhesive substance using

Low energy consumption, and

High cost of organic solvent as well as device

process

special organic reagents

almost no exhaust emission

investment

Mechanochemical

Discording the structure of the

efficiency of valuable metal and

method

materials using grinding techniques

making the reaction condition

Dissolution

29, 48, 49

Enhancing the leaching High energy consumption and noise problems

become mild

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 Pyrometallurgical process

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Pyrometallurgical process is one branch of the extractive metallurgies to disposal ore and

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concentrates with thermal treatment through physical and chemical transformations to enable

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recovery of valuable metals. Pyrometallurgical methods have been widely investigated in

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recovering Zn, Ni, Cd and other heavy metals from spent Zn–Mn dry batteries or Ni-Cd

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batteries.52, 53 Generally, smelt slags were used in pyrometallurgical methods to separate metals, in

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which some metals go to the slag and target metals turn into alloy. Except for the Umicore

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technology,54,

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technologies. Ren et al.56 proposed a new slag system of MnO-SiO2-Al2O3 by adding CaO+SiO2,

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pyrolusite, and some Al shells into the pretreated spent LIBs. The mixture was then heated up to

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1475 °C for 30 minutes. A high purity alloy with Co (99.03%), Ni (99.30%), Cu (99.30%) and

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enriched slag with MnO (47.03%) and Li2O (2.63%) were achieved by this novel process.

55

pretreatment processes are unavoidable for most of the pyrometallurgical

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In a typical pyrometallurgical process, Li will end up into the slag phase, which has to be

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further extracted.15 Carbothermal reduction methods as a pyrometallurgical method to recycle Li

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and other metals have received attention in recent years.57 In this process, the mixed spent LIBs

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can be converted into metal oxide, pure metal or lithium carbonate. In one step, lithium carbonate

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is leached by water, while the graphite in the leaching slag burn and leave metal oxide as the final

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residue.58 In the subsequent step, pure metal, graphite and lithium carbonate are further separated

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by wet magnetic separation.59 However, the pyrometallurgical technologies also currently face the

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challenges on reducing energy consumption and match the rigorous requirements for the treatment

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equipment.

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 Hydrometallurgical process

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A hydrometallurgical process mainly consists of leaching and extraction. It has many

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advantages in comparison with the pyrometallurgical process, such as high extraction efficiency,

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low energy consumption, little hazardous gas emission and low capital cost. It has a huge potential

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in industrial realization. However, little adaptability for disposing raw materials is a great

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challenge. Figure 3 shows a comprehensive summary of hydrometallurgical process. The 10

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hydrometallurgical process mainly includes leaching, solvent extraction, precipitation, and

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electrochemical method. Among them, a very limited number of studies are reported on disposal

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of spent LIBs via the electrochemical process, due to its high energy consumption, even though

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prior arts do suggest its feasibility of obtaining pure Co metal or Co compounds.8, 60-62

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Figure 3. Hydrometallurgical processes for spent LIBs.

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Traditional leaching

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To recycle spent LIBs, the cathode materials are usually dissolved in leaching reagents,

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followed by separation and extraction as main steps, which are similar to other metallurgical

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processes. In early research, inorganic acid reagents, such as HCl, HNO3 and H2SO4 were widely

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used as leaching agents, and were proven to be feasible and effective, while the disadvantages, e.g.,

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the emission of secondary pollutants and the complexity of separation and purification steps also

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appeared.47, 63, 64 The chemical reaction of leaching using HCl can be described as:

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8HCl+2LiCoO2→2CoCl2 +Cl2 ↑+2LiCl+5H2 O

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The reaction using other monatomic acid or ployatomic acid for leaching is similar. The leaching 11

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efficiency of Co without reductants follows the order of HCl > HNO3 ≈ H2SO4. The relatively high

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reducibility of HCl mainly contribute to this different leaching performance.65 Therefore, the

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leaching efficiency of most reagents would be unsatisfying unless H2O2 or other reductants are

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added. The mechanism of reduction reaction can be described as (take LCoO2 as an example):

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3H2 SO4 +2LiCoO2 +2H2 O2 →Li2 SO4+5H2 O+1.5O2 ↑+2CoSO4

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The reason that reductants like H2O2 or ascorbic acid can facilitate leaching can be explained by

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Figure 4(a). Although Co2+ is much easier to be dissolved than Co3+ at the room temperature, Co3+

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is predominately rich in spent materials. Hence when the Co3+ is converted to Co2+, the leaching

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efficiency and reaction kinetics will be improved obviously. Furthermore, the shadow in Figure

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4(a) may be a favorable area to separate Co3+ from Cu2+, Mn2+ and other metal ions because of its

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significantly different solubility constant among these metal ions. With increasing in reductant

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concentrations, the leaching efficiency and reaction rate would firstly increase accordingly, then

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reach a plateau, at which leaching efficiency and reaction rate will not vary appreciably.66

(2)

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Except for adding reductant, many organic leaching reagents, such as citric acid,67 aspartic

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acid,67 malic acid,67 oxalic acid,68 ascorbic acid,69 and glycine,70 are extensively investigated to

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solve those problems associated when using the inorganic leaching regents. The reaction

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mechanism of leaching by citric acid could be described as following71 : 18LiNi1/3 Co1/3 Mn1/3 O2 +18H3 Cit+C6 H12 O6 →

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6Li3 Cit+2Ni3 (Cit)2+2Co3 (Cit)2 +2Mn3 (Cit)2+33H2 O+6CO2 ↑

(3)

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According to Li et al.,72 the leaching efficiency of Co using citric acid is higher than that when

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using HCl or H2SO4, while Li leaching efficiency remains similar among those different leaching

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media. Most of organic acid presents a similar reaction mechanism to critic acid with some

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exceptions such as oxalic acid. The oxalic acid could act both as reductant and leachant, and the

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leaching efficiencies of Co and Li could achieve 97 and 98%, with the reaction described as68

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4H2 C2 O4+2LiCoO2→CoC2 O4 ↓+LiHC2 O4 +2CO2 ↑+4H2 O

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Figure 4. (a) The connections between pH and the equilibrium concentration of metal ions in

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aqueous solution (25 °C); (b) The E-pH diagram for the Co−H2O and Ni−H2O systems (25 °C,

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Co=0.2 mol L-1, Ni=0.2 mol L-1).

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In addition to the acid leaching system, alkaline system such as ammonia is also investigated.

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Zheng et al.73 introduced an ammonia-ammonium sulphate system as leaching system with a

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selectivity of metals during leaching. Ku et al.9 used a similar system including ammonia,

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ammonia sulfite and ammonia carbonate to leach. It was easy to separate Cu from Co, Ni in

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ammonia system, because Co and Ni in spent LIBs were in high valence state, making them hard

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to dissolve. Ammonia carbonate acted as a pH buffer to stabilize the pH of leaching solution.

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Ammonia sulfite was added as reductant to increase the leaching efficiencies of Co and Ni.

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In addition, the widely employed supercritical fluid in extracting metals offers a potential

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opportunity in leaching spent batteries. Bertuol et al.74 investigated the leaching of cobalt from the

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spent LIBs under a supercritical CO2 atmosphere with sulfuric acid and H2O2. The results showed

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that the reduction duration and the consumption of H2O2 could respectively drop from 60 min and

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8 vol. % to 5 min and 4 vol. %, with achieving the same leaching performance (95.5% Co). Liu et

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al.75 used subcritical water to accelerate the dechlorination of PVC, which was regarded as acid

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source in this experiment. Over 95% Co and closely 98% Li were leached under the conditions:

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PVC/LiCoO2 ratio 3:1, solid/liquid ratio (S/L) 16:1 (g/L), and temperature 350 °C. However, the

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rigorous requirements of the equipment, high temperature, and high pressure atmosphere increase 13

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the capital cost and the complexity of operation. All of those above-mentioned technical hurdles

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make the passion of applying supercritical fluid in recycling batteries becoming calm down.

293

As given in Table 2, the details of leaching processes of spent LIBs are summarized. Though

294

there are many reports about leaching process, few of them focus on explaining the leaching

295

mechanism based on crystallographic method, at molecular or atomic level. Takacova et al.76

296

explored the change of spent LIBs in HCl leaching process depending on the change of d(003). It

297

could be a good choice for further investigations of the leaching process in the future. The more

298

mechanisms we know about leaching process, the more conveniences we obtain to enhance

299

efficiency of leaching process.

300

For achieving the visualization of pros and cons of using different leaching reagents,

301

quantifying method for leaching rates of Li and Co are proposed in this work. The leaching rate of

302

metal is defined as:

303

rM =WM ×a×R/t

(5)

304

where rM represents the leaching rate of metal, WM (w/w %) represents weight percentage of metal

305

in raw materials (spent LIB), a (%) is the leaching efficiency of metal, R (g/L) is the S/L, whereas

306

t is the leaching time. This equation allows us to compare the leaching performance among

307

different reagents. In general, the leaching efficiency of valuable metals can reach more than 90%.

308

However, some of them use a low S/L or long leaching time. Assume 1kg of Co is leached from

309

spent LIBs by different leaching processes, Green House Gas (GHG) emissions, energy

310

consumption, and cost are also calculated with stoichiometric consumption of materials to

311

evaluate recycling. The relative data are gathered from the Greenhouse gases, Regulated

312

Emissions, and Energy use in Transportation (GREET) model proposed by Argonne National

313

Laboratory.77 As given in Figure 5, the GHG emission, energy consumption, and cost of organic

314

reagent are much higher than inorganic reagent. However, considering the biodegradability of

315

leaching reagent and reducing flue gas of productive process, the advantages of organic reagent is

316

quite obvious.67 Besides, we don’t give the relevant data about GHG emission and energy

317

consumption of H2SO4. The leaching rate of valuable metal in H2SO4 is much better than other

318

reagents for a large S/L and a short reaction time. However, H2SO4 are usually obtained as 14

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319

by-product of other technologies in many companies i.e., copper smelting. Therefore, there is no

320

data about GHG emission and energy consumption of H2SO4 production.77

321

In summary, leaching time, agitation speed, solid-to-liquid ratio, temperature, and

322

concentration of leachant and reductant were found to be the most influential factors on the

323

leaching performance. The leaching process would be enhanced with increasing in temperature,

324

leaching time, agitation speed, as well as concentrations of leachant and reductant, whereas the

325

leaching efficiency and rate both decrease obviously as solid-liquid ratio increases. It should be

326

noted that plateaus would show up when the above-mentioned factors increase to a certain value.

327

These will guide future efforts in optimization of leaching processes upon processing different

328

types of LIBs using different leaching media. MJ/kg 2300 1800 1500 1200

4 0.0 0.0 0.0

0 0.1

6 0.0 75

9

5

3

750

450

150

0.3

300

15 0.0

0.0

600

9

105 0 900

15

12

3

0.6 0.9 1.2 1.5 1.8

5

2.1

rLi((g/min⋅L))

rCo((g/min⋅L))

329

Emission CO2 kg/kg

6

300 0

21

900 600

18

Cost ¥

)

(

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Succinic acid

HCl

Citric acid

H3PO4

330

Figure 5. The spider chart for relative evaluation index of leaching spent LIBs with typical

331

leaching reagents.

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332

Table 2

333

The cases of leaching spent LIBs using different leaching reagents Raw material

Reagent

Page 16 of 53

Leaching efficiency (%)

Temp.

Time

(°C)

(min)

Co

Li

Ref.

Inorganic acid leaching Spent LIBs

1.75 mol/L HCl

50

90

99.0

100.0

78

Spent LIBs (LiCoO2)

4 mol/L HCl

80

30

90.6

93.1

79

LiFePO4 and LiMn2O4

6.5 mol/LHCl +5 vol. % H2O2

30

60

74.1

80

LIB industry waste (LiCoO2)

2 mol/L H2SO4+5 vol. % H2O2

75

30

94.0

95.0

81

LiNixMnyCozO compounds

4 mol/L H2SO4 +5 vol. % H2O2

65-70

120

96.0

Spent LIBs (mixture)

1 mol/L H2SO4 +0.075 M NaHSO3

95

240

91.6

96.7

83

2 mol/L H2SO4 +5 vol. % H2O2

75

60

70.0

99.1

84

2% H3PO4 +2 vol. % H2O2

90

60

99.0

88.0

85

Spent LIBs (LiCoO2)

0.7mol/L H3PO4 +4 vol. % H2O2

40

60

99.0

100.0

86

Spend LIBs (LiCoO2)

1 mol/L HNO3 +1.7 vol. % H2O2

75

60

95.0

95.0

87

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

80

300

80.7

95.3

73

Spent LIBs (LiCoO2) (from laptop computers) Spent LIBs (LiCoO2) (from mobile phones)

82

Alkaline leaching Spent LIBs (Li(Ni1/3Co1/3Mn1/3)O2)

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Raw material

Reagent

Leaching efficiency (%)

Temp.

Time

(°C)

(min)

Co

Li

80

60

93.0

95.0

80

120

96.7

70

80

96.0

98.0

89

95

150

97.0

98.0

68

80

120

99.0

90.0

66

Ref.

Na2SO4 Organic acid leaching Spent LIBs (LiCoO2) Spent LiCoO2 and CoO Spent LIBs (LiCoO2) Spent LIBs (LiCoO2) Spent LIBs (LiCoO2)

0.4 mol/L Tartaric acid +0.02 mol/L Ascorbic acid 1 mol/L Oxalate +5 vol. % H2O2 2 mol/L Citric acid + 0.6g/g H2O2 (H2O2/spent LIBs) 1 mol/L Oxalic acid 1 mol/L Iminodiacetic acid +0.02 M ascorbic acid

69

88

Spent LIBs (LiCoO2)

1 mol/L Maleic acid +0.02 M ascorbic acid

80

120

99.0

96.0

66

Spent LIBs (LiCoO2)

0.5 mol/L Glycine +0.02 M ascorbic acid

80

120

91.0



70

Spent LIBs (LiCoO2)

1.5 mol/L Succinic acid +4 vol. % H2O2

70

40

100.0

96.0

90

2 mol/L L-tartaric acid +4 vol. % H2O2

70

30

98.6

99.1

37

Spent LIBs (LiCoO2 and LiNi0.5Co0.2Mn0.3O2)

334

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335

Bio-metallurgical process

336

The performance of bio-metallurgical process primarily depends on the ability of

337

microorganisms to convert insoluble solid compounds into soluble and extractable forms.91 Mishra

338

et al.92 used chemolithotrophic and acidophilic bacteria acidithiobacillus ferrooxidans as leaching

339

bacteria. The reaction could be maintained at 30 °C with pH of 2.5, while the leaching efficiencies

340

of Co and Li both were quite low, even with a long leaching time and Fe2+ as catalyst. However,

341

according to the reports from Zeng et al. and Chen et al.93, 94, the leaching efficiency of Co could

342

reach 98.4% within 7 days in acidithiobacillus ferrooxidans with 0.02 g/L Ag+. Similarly, Cu2+

343

could also be used as catalyst during the acidithiobacillus ferrooxidans leaching process.95 The

344

result showed that the leaching efficiency of Co could reach 99.9% in 6 days with 0.75 g/L Cu2+

345

added into solution. Using mixed culture of different bacteria in one system was trialed, such as

346

the system mixed with acidophilic sulfur-oxidizing bacteria (SOB) and iron-oxidizing bacteria

347

(IOB).96, 97 Fungal leaching is a favorable technology compared with bacterial leaching.98 It has

348

many advantages, like growing over a wide range of pH, tolerating toxic materials and conducting

349

with a high leaching rate. There were various organic acids in fungi metabolite to achieve the

350

leaching process.98, 99

351

Compared to the conventional methods, bio-metallurgical process occurs in a mild condition

352

with less energy consumption, making it an eco-friendly technology.100 Nevertheless, the slow

353

kinetics and low pulp density are the fatal weaknesses of bio-metallurgical process when it is

354

applied to industrial production. In one research,101 the bioleaching efficiency decreased from 52%

355

to 10% for Co and from 80% to 37% for Li, when pulp density rose from 1% to 4%. Even though

356

high leaching efficiencies of Co and Li may be achieved with a high pulp density by controlling

357

reaction temperature, increasing the dose of mixed energy substrates, and adjusting the pH,101 the

358

leaching process are still be very time-consuming. Hence, the bio-metallurgical methods of

359

disposing spent LIBs are still far from industrial application, whereas they have significant

360

advantages in energy-saving.

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361 362

Solvent extraction

363

One of the main targets for recycling process is to obtain pure metal or metal compounds.

364

However, co-existing of various metal ions in the leachate will inevitably suppress the recycling of

365

pure metal or metal compounds. In addition, the overlap of pH range for precipitation of different

366

metals makes the attempt of single step precipitation ineffective in obtaining pure metals. Hence,

367

the leaching solution must undergo numerous steps of separation and extraction e.g., solvent

368

extraction, selective precipitation and electrochemical method, in order to achieve satisfied levels

369

of purity.

370

Solvent extraction is a liquid-liquid extraction method that utilizes the different relative

371

solubility of compounds in two immiscible liquid to separate them from each other. Although

372

facing the challenges of separating compounds with similar functional groups, it remains as

373

reliable and is widely adopted in the extraction of tungsten and molybdenum, copper from

374

minerals, nuclear reprocessing, and the production of fine organic compounds.

375

Effect of equilibrium pH on extraction of different metals is significant solvent extraction.

376

For example, the di-(2-ethylhexyl) phosphoric acid (D2EHPA) is good at extracting copper and

377

manganese ions, while its selectivity in extracting Co is poor at pH 2.2~3.0.102 When the pH of

378

leachate increases, the extraction efficiency of Co with cationic extractant D2EHPA is improved

379

accordingly.103 The extraction reaction follows the mechanism63, 104: -

380 381

(6)

-

(7)

or 2(HA)2Org +MOH+(Aq)+AOrg→MሺOHሻA·3HAሺOrgሻ+H+(Aq)

382 383

+ M2+ Aq +AOrg +2(HA)2Org →MA2 ·3HAOrg +HAq

-

where AOrg+ 2(HA)2Org represents the saponification reaction as:

384

Na+Aq +1/2(HA)2Org →NaAOrg +H+Aq

385

The extractant PC-88A can effectively separate Co and Ni ions from other metal ions at pH

386

4.5, while it has no extraction efficiency when pH is less than 3.102 Cyanex272 has been widely

387

investigated as extractant due to its excellent selectivity. Swain et al.81 used Cyanex 272 as 19

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388

extractant, 5 vol. % tributyl phosphate (TBP) as phase modifier and kerosene as diluent to extract

389

85.42% Co from the leachate at pH 5. Jha et al.105 also reported a similar system, except that

390

isodecanol was used as phase modifier. The extraction efficiency of Co reached 99.9% at pH 5.0.

391

The suitable scale of pH of different extraction reagents are summarized in Figure 6.79, 103, 106-108 It

392

is obvious that the suitable pH to separate Co and Ni of some reagents distributes in the pH range

393

between 3 and 5, which requires a good performance in corrosion resistance for reactor. For this

394

reason, Cynaex 272, Cynaex 302 and P507 may be a good choice. The additive can change the

395

optimal pH of solvent extraction. For example, in Figure 6, when the PC-88A is used alone to

396

selectively extract Co, the suitable pH range falls between 3.5 and 4. The extraction efficiency of

397

Ni is low in this range. When TOA is added as phase modifier, the suitable pH scale will shift

398

between 3.5 and 5, which is higher than its previous one and leaves more room for operational

399

parameters to adjust.

400

401 402

Figure 6. Effect of suitable pH on the solvent extraction of different extraction reagent. (The pH

403

scale of different extractants is summarized under the same conditions like 25 ºC and A:O=1, 20

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404

except the Mextral 5640H (A:O=2)).

405 406

Precipitation

407

The selective precipitation is a single chemical process, which has been widely investigated

408

and applied in extracting metals from complex system. Sometimes, it is hard to precipitate only

409

one ion from solution. From the E-pH diagram shown in Figure 4(b), the overlap between stable

410

areas of Co(OH)2 and Ni(OH)2 is so large that Ni2+ and Co2+ is prone to be co-precipitated via

411

neutralization reaction. However, Figure 4(b) also indicates that the stable areas of Ni2+ and

412

Co(OH)3 have a small overlap. Thus, it is a possible approach to transform Co2+ to Co3+ to achieve

413

selective precipitation of Co3+ in this small area. The above-described strategy was proven to be

414

feasible and effective by Joulié et al.

415

and Ni both were nearly 100%. The reaction mechanism can be expressed as:

65

With NaClO as oxidant, the recovery efficiencies of Co

416

Co2+ +ClO- +2H3 O+ →2Co3+ +Cl- +3H2 O

(9)

417

Co3+ +6HO-→Co2O3+3H2 O

(10)

418

It should be noted that no Mn exists in the system reported by Joulié et al.65 When Mn2+ is

419

oxidized to Mn4+ at pH of 2, it will form MnO2 or manganese hydroxide according to the reaction

420

described as follow:

421

3Mn2+ +2MnO4 +2H2O→5MnO2 +4H+

(11)

422

The dimethylglyoxime reagent (DMG, C4H8N2O2) is widely used to precipitate Ni2+ as nickle

423

dimethylglyoxime chelating precipitate from Co, Ni, and Mn mixed solutions. As reported by

424

Chen et al.109, nearly 96% of Ni2+ could be precipitated within 20 minutes at room temperature

425

(Equation 13). The values of pKsp for Co2+, Ni2+ and Li+ are in the order of

426

NiC2O4≈CoC2O4>>Li2C2O4.39 After removing Ni2+ and Co2+, the main metal ion in leachate is Li+,

427

which can be precipitated efficiently as Li2CO3 or Li3PO4 (Equation 16).71

428

6C4 H8 N2 O2 +Ni3 (Cit)2 →3Ni(C4 H6N2 O2)2+2H3 Cit

(12)

429

ሺNH4 ሻ2 C2 O4 +Co2+ +2OH-→CoC2O4 ·2H2 O+2NH3

(13)

430

Co3 ሺCitሻ2 +3H2 C2 O4 →3CoC2O4 +2H3 Cit

(14)

431

Li3 Cit+H3 PO4 →Li3 PO4 +H3 Cit

(15)

21

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432 433

Method of leaching-re-synthesis

434

Traditional separation and extraction technologies, e.g., solvent extraction, precipitation, and

435

ion-exchange are usually not economically justifiable to be applied in industrial production due to

436

their significant disadvantages, e.g., complicated recycling routes, high chemical reagent

437

consumption, and high waste emission. Therefore, the short and efficient route for the recycling of

438

spent LIBs is the potential process and need to be researched. In order to shorten the route, avoid

439

the problems in separating metal ions from each other, reduce secondary pollution, and enhance

440

the recycling efficiencies of valuable metals, material synthesis methods to achieve one-step

441

fabrication from leachate to regenerate materials were researched recently, like the

442

leaching-re-synthesis method.110-112 The leaching-re-synthesis method, which belongs to

443

regeneration methods, is focused on the synthesizing the regenerated materials in short steps

444

through sol-gel or coprecipitation technologies.

445

In recent researches, Sa et al.111 used the leachate as the raw liquor to regenerate

446

LiNi1/3Mn1/3Co1/3O2 in N2 atmosphere at room temperature using a typical co-precipitation method.

447

After 50 cycles, the capacity of regenerated material decreases to 80% (120 mA h g-1) with the

448

first cycle.111 With previous experience of using ascorbic acid for leaching, Lu et al.113 adjusted the

449

metal ions ratio and pH of the leachate to obtain regenerated cathode material LiCo1/3Ni1/3Mn1./3O2

450

through a sol-gel process. Zou et al.114 used similar technology to dispose the mixed raw cathode

451

materials and obtained regenerated cathode materials as products with well electric performance.

452

Some information of the leaching-re-synthesis approaches are provided in Table 3. It can be seen

453

that the regenerated cathode materials present similar characteristics to the commercial batteries in

454

terms of rate capacity and cycle life. Among them, the electrochemical properties of regenerated

455

cathode materials from ascorbic acid leaching system are much better than those prepared from

456

other systems. Other than that, the available data suggest that little difference of electrochemical

457

properties exists in cathode material from different leachates.

458

Except for cathode materials, synthesizing other reactive materials from the spent LIBs is

459

also a good alternative and has been widely developed by many researchers. Yao et al.115 used a 22

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460

simple technology, including pretreatment, sulfuric acid leaching, filtering, sol-gel, and calcination

461

method, to obtain sintered or hydrothermal cobalt ferrite precursor (S-CoFe2O4 or H-CoFe2O4).

462

The products have excellent characteristics in term of magnetostriction coefficient (-158.5 ppm)

463

and train derivative coefficient (-1.69×10-9 A-1).115

23

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464

Table 3

465

Summary of regeneration approach of cathode materials from spent LIBs in literature Final production

Leaching reagent

Addition reagent

Precipitant

H2SO4 (+H2O2)

Sulfate salts

Ammonia solution

LiNixCoyMn1-x-yO2 (LiNi0.8Co0.1Mn0.1O2 LiNi0.5Co0.2Mn0.3O2

Page 24 of 53

Initial discharge capacity mA h g−1(2.7-4.3 V 0.1 C)

Ref.

197.7 174.3

110

168.3

LiNi1/3Co1/3Mn1/3O2) LiNi1/3Mn1/3Co1/3O2

H2SO4 (+H2O2)

Sulfate salts

NaOH and NH3·H2O

139.0

111

LiNi1/3Mn1/3Co1/3O2

D,L-malic acid

Solution

Metal nitrate

147.2 (0.5 C)

113

LiNi1/3Co1/3Mn1/3O2

Citric acid (+H2O2)

Nitrate salts

Ammonia solution

154.2(0.2 C)

116

LiNixMnyCozO2

H2SO4 (+H2O2)

Sulfate salts

NaOH and NH3·H2O

155.0

117

Li[(Ni1/3Co1/3Mn1/3)1−xMgx]O2

H2SO4 (+H2O2)

Sulfate salts

152.7(0.2 C)

118

LiNi1/3Mn1/3Co1/3O2

H2SO4 (+H2O2)

Sulfate salts

NaOH

160.0

114

Li1.2Co0.13Ni0.13Mn0.54O2

Ascorbic acid

Acetate salts

Oxalic acid

258.8

119

Controlled Crystallization

466 467

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468

 CURRENT RESEARCH FOR THE RECYCLING OF ANODE AND

469

ELECTROLYTE

470

The recycling of anode and electrolyte are also important to establish a comprehensive

471

recovery technology of the spent LIBs as well as to release the environmental pollution and

472

potential safety risks. While due to their relatively low value, only a little attention has been paid

473

to this area. In Umicore process, the electrolyte is removed and pyrolyzed under 300 ºC and 600

474

ºC, respectively.120 In hydrometallurgical processes, the electrolyte can be reclaimed by using

475

organic or supercritical solvent.121 Liu et al.122 developed a process for the recycling of spent LIBs

476

electrolyte including supercritical CO2 extraction, weakly basic anion exchange resin

477

deacidification, molecular sieve dehydration, and components supplement. The electrochemical

478

performance of the reclaimed electrolyte was acceptable compared to the commercial one. The

479

high-cost and low-process-capacity are the key factors limiting further promotion of supercritical

480

solvent.

481

As for the anode, it is usually separated form spent LIBs through physical methods, like

482

dismantling, crushing, screening and other mechanical processes. Guo et al.123 indicated that 30.07

483

mg/g Li existed in the anode active materials. Therefore, a traditional acid leaching method was

484

used to recover Li from anode active materials. Besides, the graphite obtained from spent anode

485

showed a large surface area and a stable crystal structure. After removing the organic binder and

486

other organic impurities under high temperature, it could be used as porous supporting material to

487

synthesize new function materials, like sorbents. 124, 125

488

 CURRENT INDUSTRIAL RECYCLING PROCESS

489

The recovery of spent LIBs are relatively new in comparison with the recycling of Ni-Cd and

490

Pb-acid batteries, and many of the technologies are still in lab- or small-scale pilot stages. The first

491

commercial production line was established by TOXCO in 1994. 126 After that, with the increased

492

attention, more and more technologies have been applied in commercial production and many

493

companies have established a complete line to recycle spent LIBs around the world. Current 25

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494

industrial processes for the recycling of spent LIBs are summarized in Table 4. The percentage and

495

annual processing capacity of spent LIBs recycled by different technology is shown in Figure 7, in

496

which the data is mainly based on thirty companies and twelve companies, respectively.

497

498 499

Figure 7. The percentage of spent lithium-ion batteries recycled by different technology based on

500

the (a) quantity of companies (thirty companies) and (b) annual processing capacity of some of

501

these companies (seven companies); (c) flow-sheet of main processes used in industries.

502 503

Flow-sheet of main processes is shown in Figure 7(c). Most of the commercial processes

504

used pyrometallurgical methods as secondary technologies. 127 The reason is that most of them are

505

not a LIB dedicated recycling process in their original design, like Xstrata, Batrec AG, Akkuser,

506

etc. Only Co, Ni and Cu could be recovered effectively through pyrometallurgical methods. Li and

507

Al are lost in the slag. Besides, alloy of Cobalt and Nickel also need to be processed through

508

hydrometallurgical methods, like electrolyzing. Therefore, most of these companies establish a

509

process combining pyrometallurgical and hydrometallurgical methods. In Umicore process, the

510

discharging phase is omitted and pretreatment of spent LIBs is unnecessary, which are the

511

important technologies in other processes. Comparing to other processes, it is simple and effective.

512

Complex mechanical methods are used to separate materials from each other. The Cu foil, Al foil,

513

and steel are separated from other components and reused directly in new batteries through 26

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514

mechanical methods in other processes. However, they need to be further recovered to obtain

515

production in Umicore process. Toxco and Sumitomo-Sony processes face the issues of gas

516

emissions in pyrometallurgical methods and H2 emissions in wet crushing. The processes include

517

similar methods also have these issues. Recupyl Valibat process conducts recycling process under

518

a low-temperature making it easy to disposal flue gas and H2. Handling spent LIBs under CO2

519

atmosphere also reduce the risk of mechanical treatment with discharged LIBs. Many of

520

hydrometallurgical methods have also been achieved in industrial application, like Recupyl

521

Valibat process, Toxco process, Accurec, etc. In Recupyl process, the slag from mechanical

522

treatment is dissolved in H2SO4. Cobalt in solution is oxidized by NaClO to obtain cobalt

523

hydroxide. Lithium remained in the solution is precipitated by CO2 gas. In other companies, the

524

hydrometallurgical processes included similar technologies, like leaching, solvent extraction,

525

precipitation, etc. The long routes of them are the main drawback, which will result in the loss of

526

valuable metal and pollution. Bangpu establishes a closed-loop for the recycling of spent LIBs

527

from waste to regenerated cathode materials or other valuable materials, which could achieve the

528

recycling of spent LIBs in a short route. The details of these hydrometallurgical processes are not

529

available. But, they could be similar to the processes we introduced in “hydrometallurgical

530

process”.

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Table 4 Summary of current LIB recycling industrial technologies throughout the world120, 128, 129 Company/Process

Location (s)

Annual capacity

Details of technology

(tonnes/year) TM

Umicore (VAL’EAS )

USA

7000

Main end products

It combines pyrometallurgical and hydrometallurgical technologies.

CoCl2

Spent LIBs are fed to a single shaft furnace. The alloy containing Co, Ni from furnace are further processed through leaching process. Li and Al mainly existed in the slag and need to be further treated through hydrometallurgical technologies. S.N.A.M

France

300

First stage is sortation techniques. Then the rough crushed products are disposed by pyrolysis pretreatment, crushing, and sieving.

Batrec AG

Switzerland

200

The spent LIBs are stored and shredded under CO2 atmosphere. Then, the scrap is neutralized by moist air and further treated with hydrometallurgical process.

Inmetco

USA

6000

The scarp is processed in a rotary hearth furnace and further refined

Alloy(Co/Ni/Fe)

in an electric arc furnace. Sumitomo-Sony

Japan

150

Electrolyte and plastics are removed through calcination. A

CoO

pyrometallurgical process is used to recover an alloy containing Co-Ni-Fe. A hydrometallurgical process is conducted to recover Co. AkkuSer Ltd

Finland

4000

A two-phase crushing line is designed. Magnetic separation and

Metal poeder

other separation methods follow it. Then, the scrap is delivered to smelting plants and leaching. Toxco

Canada

4500

It combines mechanical methods, like shredding, milling and 28

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CoO,

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Table 4 Summary of current LIB recycling industrial technologies throughout the world120, 128, 129 screening and hydrometallurgical methods, like leaching, and

Li2CO3

precipitation. Recupyl Valibat

France

110

Mechanical methods are used as first stage. Then, hydrometallurgical

Co(OH)2, Li3PO4.

methods are used to obtain Co(OH)2 and Li3PO4. Accurec GmbH

Germany

6000

A vacuum furnace is used first. Then, mechanical methods are used

Co alloy, Li2CO3

to separate different materials. After that, scrap is fed to an electric furnace. Slag is disposed through hydrometallurgical methods. AEA

UK

-

The first stage is using organic solvent to remove electrolyte, solvent

LiOH, CoO

and binder. Leaching of cathode is carried by electrolyzing. Glencore plc.

Canada/Norway

7000

USA

-

It combines pyrometallurgical and hydrometallurgical methods.

Alloy(Co/Ni/Cu)

Preliminary

Cathode powder

(former Xstrata) Onto process

step

involves

discharge,

electrolyte

recovery,

refurbishing, and ball mill. Supercritical fluid is used to separate different materials. LithoRec proces

Germany

-

It combines similar mechanical methods and hydrometallurgical

CoO, Li salt

methods. Green Eco-manufacture

China

20000

Hi-Tech Co Bangpu Ni/Co High-Tech Co

Hydrometallurgical methods including leaching, purifying and

Co powder

leaching- resynthesize is used. China

3600

Hydrometallurgical methods including leaching, purifying and leaching- resynthesize is used.

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Cathode material, Co3O4

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531

 DISCUSSION

532

Firstly, it is very interesting to notice that in comparison with the inorganic leachants, organic

533

leachants are relatively few to be chosen as leaching media to conduct the extraction process

534

recently, even though they are regarded as green reagents. In most of reports about solvent

535

extraction, precipitation or regeneration technology, the leaching liquids are from inorganic

536

leaching process. Among them, H2SO4 is the most frequent leachant. Organic reagents can avoid

537

the problems associated with inorganic leachants, such as triggering air pollution, rigorous

538

requirements of equipment and difficulty in recycling leaching reagents. However, the research

539

results have shown that the organic leaching can only conduct well with a low solid-to-liquid ratio,

540

which decreases the concentration of Li+ in leachate and limits the treatment capacity for

541

industrial production. A leachate with low concentration of Li+ is difficult to product high-purity

542

lithium compounds and needs to be concentrated. Besides, all of these leaching processes need to

543

be followed by solvent extraction or precipitation, in which the loss of Li is serious, to obtain the

544

pure production of Ni/Co/Mn or compounds. For example, when the D2EHPA is used to extract

545

Ni and Co, 20% Li will be co-extracted.130 The loss of Li is nearly 17% in removing Ca and Mg

546

by NaF.118 Therefore, all of these leaching reagents have their own limitations to recover valuable

547

metals from spent LIBs both cost-effectively and environmental friendly. Selectively extracting

548

target metals with a hydrometallurgical process from mines or electronic wastes has been proved

549

to be feasible in many prior researches. It is regarded as a promising approach to change the

550

current situation in recycling spent LIBs.131 Gao et al.132 achieved the selective extraction of Al

551

and Li from LiNi1/3Co1/3Mn1/3O2 cathode scrap by using formic acid as leaching reagent. It was

552

found that the selectivity of Al was more than 95% with no Al(OH)3 phase existing in Ni/Co/Mn

553

hydroxide precipitate. Meanwhile, the relatively low solubility of Co(COOH)2, Ni(COOH)2, and

554

Mn(COOH)2 comparing with Li(COOH)2 contributes to the spontaneous separation of Ni/Co/Mn

555

and Li. As Zheng et al.73 reported, the ammonia-ammonium sulphate solution with reductant could

556

also achieve the selective leaching of Li, Ni and Co from Li(Ni1/3Co1/3Mn1/3)O2 cathode scraps.

557

However, the optimal solid-to-liquid ratio in alkali system was so small that the subsequent 30

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558

extraction approaches were hard to conduct. Li et al.133 reported the selective leaching of Li from

559

spent LiFePO4 through H2SO4 at a low concentration, which was much better than the traditional

560

leaching with a high concentration of H2SO4 and a large consumption of H2O2. In consideration of

561

the rising price of lithium carbonate in recent years, it is a quite significant direction to research

562

the selective extraction of Li. Of course, the best outcome is that we can achieve recovery of

563

single metal element from spent LIBs or other waste, and leave the other metals in solid waste.15

564

Secondly, in the aspect of energy consumption, data of hydrometallurgical process,

565

intermediate physical method from Toxco, direct physical process from OnTo Technology, and

566

pyrometallurgical process from Umicore introduced by Dunn et al.134, 135, have also been estimated.

567

For simplicity, Figure 8 and Figure 9 only summarize the results of energy consumption from

568

Dunn et al.134, 135, in which the estimate is based on the GREET model proposed by Argonne

569

National Laboratory.77 Note that the energy consumption of recycling LiCoO2 through some

570

processes is not directly shown in article. The estimate of missing data follows the mechanism

571

introduced by Dunn et al.135 For example, the production of intermediate recycling process is

572

Li2CO3. We estimate the energy consumption of LiCoO2 of intermediate recycling process by

573

adding the energy consumption of producing virgin Co3O4 and recycling Li2CO3 following the

574

chemical reaction of producing LiCoO2. Figure 8 illustrates that the energy intensities of recycling

575

materials are less than producing virgin materials. With the consumption of citric acid and

576

hydrogen peroxide included in the overall process, the energy consumption of hydrometallurgical

577

process is tremendous, while the process itself is not energy intensive. Besides, an external

578

process of hydrometallurgical method, adding Mn2O3 to react with Li2CO3 to form LiMn2O4 in the

579

end, also makes the energy consumption of hydrometallurgical process more than other processes.

580

Figure 9 contains estimates of the energy consumption and Green House Gas (GHG) in total

581

LiMn2O4 production with different recycled materials. It indicates that the more recycled materials

582

are used in production, the less energy will be need in the overall process. Therefore, the reduction

583

of energy consumption and GHG emissions in the whole process to produce LiMn2O4 may be

584

possible when recycled LiMn2O4, Al and Cu are used as raw materials as shown in Figure 9.134

585

Furthermore, a reduction in total energy consumption could be foreseeable, if a closed-loop 31

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586

recycling scenario of LIBs is achieved. Because of the lack of relevant data, literatures seldom

587

report the energy consumption of other methods, such as regenerated method and

588

bio-metallurgical method. Whereas, it is important to estimate the energy consumption, which will

589

make a difference in future work.

590 591

Figure 8. Estimated energy consumption for LiCoO2 and LiMn2O4 production via different

592

automotive battery recycling processes. (The energy consumption during virgin LiMn2O4

593

production in Nevada and Chile is from Dunn et al.134 The energy consumption during virgin

594

LiCoO2 production is from Kushnir and Sandén.136).

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GHG emissions without reycling

5000

Hydrometallurgical Intermediate Physical Direct Physical

4000 3000 2000 1000

Energy consumption (MJ/kg battery)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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80

0

Energy consumption without reycling

GHG emissions (g CO2e/kg battery)

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70 60 50 40 30 20 10 0 All

Al

Cu

LiMn2O4

Recycled Component

595 596

Figure 9. The energy consumption (MJ/kg battery) of using recycled aluminum, copper, cathode

597

materials, or all of them to fabricate batteries used in electric vehicles (The solid back line is the

598

consumption of using virgin materials).

599 600

Thirdly, the “3R” principles in green chemistry should be emphasized in recycling processes.

601

Though the current researches mainly focus on the recovery and regeneration, which are the last

602

principle of “3R”, it is still hard to implement recent developed technologies in industrial

603

production because of low economic benefit and secondary pollution. For easiness of

604

implementing proposed process in industrial production, how simple the process or the route it is

605

plays pivotal role. It is widely known that a loss coefficient needs to be considered during

606

industrial production. The longer and more complex a technology is, the more valuable metal will

607

be lost, and will result in less economic benefit, such as the loss of Li in organic phase.130

608

Therefore, the best method is to observe “reuse” principle, which requires the waste should be

609

reused as its original purpose or reused as component to fulfill a different function. In this

610

principle, the waste is directly recycled or undergoes repairing process before being recycled. The

611

reuse method or regeneration methods are all short routes to recycle materials with little loss and

612

low energy consumption. 33

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613

In the aspect of legislation, successfully making “3R” ideology into integrated utilization and

614

recycling the valuable components in spent LIBs not only rely on technical breakthrough made

615

from industry and research organizations, but also rely on government support, public awareness

616

of environmental protection, innovation of manufacture and management of LIBs from cradle to

617

grave. The recycling efficiency and the complexity of technology mainly depend on the

618

complexity of spent materials. With excellent collection system and well known classification

619

method, the recycling process will become much simpler. As a result, the simplified process will

620

lead to an improved efficiency of recovery, a reduction of cost, and an increased profit margin. To

621

establish a good collection system, both collection mechanism itself and enforcement of

622

legislative policies are important. Fortunately, with the problem of spent LIBs gaining more and

623

more public awareness, governments realize the importance of setting up a comprehensive

624

collection system. The relevant laws and policies have been established to encourage the

625

development of recycling spent LIBs. As seen in Table 5, laws relevant to the collection and

626

disposal of spent batteries are constantly increasing from 2000 to now. In the early years, the

627

regulations of recycling spent LIBs were covered in the laws of disposing solid waste, as a small

628

aspect. Afterwards, some comprehensive policies about spent batteries, mainly pointing to lead

629

acid battery, are established. In recent years, special laws for spent LIBs have been established, as

630

the severity pollution caused by batteries leakage is spreading quickly and widely. Given these

631

legislative policies have already been nailed in, the public are less prone to ignore pollution caused

632

by battery leakage.

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Table 5 Regulations relevant to spent batteries in China Regulations title Policy on pollution prevention techniques from municipal solid waste

Year

Main related content

2000

Lead the development and improvement of managing and disposing municipal solid waste.

Policy on pollution prevention techniques from hazardous wastes

2001

Lead the development and improvement of managing and disposing hazardous wastes.

Policy on pollution prevention techniques from waste batteries

2003

Require manufacturers to collect spent batteries; Aim to encourage the development of managing and recycling technology of spent batteries and reduce the pollution.

Discarded household appliances and electronic products pollution control technology 2006

Aim to reduce the pollution of electric waste.

policy Auto product recovery and usage technology policy

2006

Require the automobile production enterprises to establish the collection and treatment of power batteries produced by them, or send the spent power batteries to the special company, who can dispose them.

Measures for the control of environmental pollution of electronic waste

2008

Cover the stipulations about collecting, disposing, managing

Emission standard of pollutants for battery industry

2013

Stipulate the quantity of waste water and gas from industry.

Technical requirement for environmental labeling products Battery

2013

Add the requirements about design, product and recycle

of electric waste.

process. The policy on recycling technology of electric vehicle power battery (ask for comment)

2015

Lead the development of managing and disposing spent electric vehicles power batteries.

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Regulations title The policy on recycling technology of electric vehicle power battery (2015)

Page 36 of 53

Year

Main related content

2016

Emphasize the fact that the responsibility of recycling spent power batteries belongs to the battery manufacturers.

The industry norms of utilizing waste power battery from new energy vehicles

2016

The interim measures for managing industry norms of utilizing waste power battery from

Give the requirements about the factory size, equipment, technology, energy consumption of recycling industries.

new energy vehicles Policy on pollution prevention techniques from waste batteries (ask for comment)

2016

Enlarge the managing scope of spent batteries. Encourage establishing collecting system and researching new recycling technology.

634

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635

 CONCLUSIONS AND OUTLOOK

636

Globally, several companies, such as AEA Technology (U.K.), SNAM (France), Toxco

637

(Canada), and Umicore (Belgium), have established complete production lines to recycle metals

638

from spent LIBs.55 They are mainly focusing on employing the pyrometallurgical methods,

639

hydrometallurgical methods or combined methods of them. Concerning economic benefit,

640

traditional metallurgical processes (a long process including pretreatment, leaching, and purifying)

641

have little competitiveness in comparison with newly short processes, such as selective extraction,

642

regeneration and repairing processes. Though many reports researched the recycling technologies

643

of metals from spent LIBs, few of them have achieved cost-effectiveness on an industrial scale.

644

Meanwhile, there is no commercial technology to achieve the recycling of waste mixed with

645

different cathodes. Many mechanisms of physical and chemical changes in the recycling process

646

need to be deeply explored. A complete system of recycling LIBs need to be discussed and

647

established. For future research in the recycling of spent LIBs, we believe that it should focus on

648

the following aspects:

649



650 651

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. Lots of works still

652

need to be done to guide the selection of leaching reagent and operating conditions.

653

For example, the changes of crystal structure in leaching process need to be deeply

654

researched. It will be very helpful in shedding insightful lights on reaction

655

mechanism during leaching

656



657 658

Selective leaching of most valuable metals from the spent LIBs has not been achieved yet. The relative researches should be strengthened in the future.



Most studies of disposing spent LIBs only focused on the kinetics and the

659

influence of operational parameters on leaching performance, while more efforts

660

need to be paid for establishing a complete evaluation system, in which more

661

critical factors, such as energy consumption of the whole process, could be 37

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662

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considered.

663



Furthermore, efforts also need to be concentrated on enhancing the collecting

664

efficiency and reducing the landfill of spent LIBs, which are hazardous for soil,

665

water and living organism on Earth.

666



Not restricting to the recycling process of spent LIBs, the comprehensive and

667

holistic view from cradle to grave in designing, manufacturing and recycling LIBs

668

needs to be addressed.

669

Last but not the least, a global homogenized mechanism in manufacturing, classification,

670

collection and recycling will significantly reduce the complexity of raw material, which in turn

671

minimizes the energy consumption of recycling process. All of these aspects have lasting

672

influence on achieving the economic and eco-friendly recycling of spent LIBs.

673 674

 ACKNOWLEDGEMENTS

675 676

This work was financially supported by the National Key Research and Development Program of

677

China (2017YFB0403300/2017YFB043305), Beijing Science and Technology Program (No.

678

Z171100002217028), the National Natural Science Foundation of China (No. 51425405 and

679

L1624051) and National Science and technology Support Plan Project (2015BAB02B05).

680 681 682

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683 684 685 686 687 688 689 690 691 692

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(110) Yang, Y.; Huang, G.; Xie, M.; Xu, S.; He, Y., Synthesis and performance of spherical LiNixCoyMn1-x-yO2 regenerated from nickel and cobalt scraps. Hydrometallurgy. 2016, 165, 358-369. DOI: 10.1016/j.hydromet.2015.11.015. (111) Sa, Q.; Gratz, E.; He, M.; Lu, W.; Apelian, D.; Wang, Y., Synthesis of high performance LiNi1/3Mn1/3Co1/3O2 from lithium ion battery recovery stream. J. Power Sources. 2015, 282, 140-145. DOI: 10.1016/j.jpowsour.2015.02.046. (112) Yang, Y.; Huang, G.; Xu, S.; He, Y.; Liu, X., Thermal treatment process for the recovery of valuable metals from spent lithium-ion batteries. Hydrometallurgy. 2016, 165, 390-396. DOI: 10.1016/j.hydromet.2015.09.025. (113) Yao, L.; Yao, H.; Xi, G.; Feng, Y., Recycling and synthesis of LiNi1/3Co1/3Mn1/3O2from waste lithium ion batteries usingd,l-malic acid. RSC Advances. 2016, 6 (22), 17947-17954. DOI: 10.1039/c5ra25079j. (114) Zou, H.; Gratz, E.; Apelian, D.; Wang, Y., A novel method to recycle mixed cathode materials

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(119) Li, L.; Zhang, X.; Chen, R.; Zhao, T.; Lu, J.; Wu, F.; Amine, K., Synthesis and electrochemical performance of cathode material Li1.2Co0.13Ni0.13Mn0.54O2 from spent lithium-ion batteries. J. Power Sources. 2014, 249, 28-34. DOI: 10.1016/j.jpowsour.2013.10.092. (120) Marinos, D. An approach to beneficiation of spent lithium-ion batteries for recovery of 46

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TOC/Abstract Art

1103

For Table of Contents Use Only

1104 1105

Synopsis

1106

A critical review and analysis for the recycling of valuable metals and materials from spent

1107

lithium-ion batteries is demonstrated.

1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 49

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1122

Author information

1123

Corresponding Authors

1124

*Z. Sun. E-mail: [email protected]; Tel: +86 10 82544844

1125

Fax: +86 10 82544845.

1126

Notes

1127

The authors declare no competing financial interest.

1128

Biographies

1129 1130

Weiguang Lv is a doctoral student in the Institute of Process Engineering, Chinese Academy of

1131

Sciences. He received B.Sc. degree in metallurgical engineering (Central South University). His

1132

current research focuses on efficient recovery of valuable metal from spent LIBs.

1133 1134

Dr. Zhonghang Wang is a postdoctoral researcher in the Institute of Process Engineering, Chinese

1135

Academy of Sciences (IPE, CAS). He received the B.Sc. degree in chemical engineering and

1136

technology (Central South University), and the Ph. D. in chemical technology (University of

1137

Chinese Academy of Sciences). He has been working on electrometallurgy and molten salt

1138

electrochemistry for many years. His current research focuses on efficient recovery of valuable 50

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1139

metals from the e-waste, and the electro-conversion of e-waste to high-value products.

1140 1141

Dr. Hongbin Cao is a professor in Institute of Process Engineering, Chinese Academy of Sciences,

1142

deputy director of the National Engineering Laboratory for Hydrometallurgical Cleaner

1143

Production Technology and director of Beijing Engineering Research Center of Process Pollution

1144

Control. His research interest is the whole process control of industrial pollution: theory,

1145

technology and application. Dr. Cao has published over 100 papers, and applied over 60 patents

1146

including 5 international patents. He won the second prize of State Technological Innovation

1147

Award (2013), the first prize of Environmental protection science and Technology Award (2012)

1148

and the first prizes of Science and Technology Invention Award of Liaoning province (2011). He is

1149

also the holder of National High-level personnel of special support program (2013) and the holder

1150

of the National Science Fund for Distinguished Young Scholars of China (2014).

1151 1152

Dr. Yong sun is Technical Support Engineer within the School of Engineering's Technical Support

1153

team. He received Ph.D. of Biochemical Engineering in China and M.Sc degree of Engineering

1154

Science in Monash University. His current research focuses on expertise in fischer-tropsch

1155

synthesis, heterogeneous catalysis, hydrometallurgy, gas separation and storage, fluidization. Dr. 51

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1156

Sun has coauthored more than 50 publications.

1157

1158 1159

Professor Zhang, working in the Institute of Process Engineering, Chinese Academy of Sciences

1160

(CAS), is one of the chief scientists firstly entering the field of green process engineering in China

1161

and is currently engaged in the fundamental and application research on green process engineering

1162

and environmental control technology. As the chief scientist, she had presided the first National

1163

Sci-Tech Project and the first 863 Project on cleaner process research. Furthermore, she proposed

1164

a revolutionary green process for highly efficient and clean conversion of mineral resources with

1165

sub-molten salt medium. Professor Zhang has achieved the second and third prizes of National

1166

Technical Invention Awards, the second and third prize of National Sci-Tech Progress Awards, and

1167

the first prize of Sci-Tech Progress Awards of CAS (3 times). Professor Zhang has published more

1168

than 170 papers and edited 9 books. She has also submitted 34 China invention patent applications

1169

with 10 granted. Under her directing, 48 graduates has obtained their master's or Ph. D. degrees

1170

since 1990.

1171 1172 1173

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1174 1175

Dr. Zhi Sun is a professor in the Institute of Process Engineering, Chinese Academy of Sciences.

1176

He received B.Sc. degree in metallurgical engineering (University of Science and Technology

1177

Beijing), M.Sc. degree in chemical engineering (Chinese Acadamy of Sciences) and Ph.D. in

1178

materials engineering (KU Leuven, Belgium). He has been working as a postdoctoral researcher in

1179

University of Queensland, Australia and senior researcher in Delft University of Technology, The

1180

Netherlands. His current research focuses on electronic waste treatment, sustainable process

1181

design for metal recycling and green design of electronic products. He is member of the Chinese

1182

association of waste battery treatment. Dr. Sun has coauthored more than 50 publications and 5

1183

patents. He is also editorial board member of two international journals.

1184

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