Recovery of Lithium, Iron, and Phosphorus from Spent LiFePO4

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Recovery of lithium, iron and phosphorus from spent LiFePO batteries using stoichiometric sulfuric acid leaching system Huan Li, Shengzhou Xing, Yu Liu, Fujie Li, Hui Guo, and Ge Kuang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b01594 • Publication Date (Web): 10 Aug 2017 Downloaded from http://pubs.acs.org on August 11, 2017

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ACS Sustainable Chemistry & Engineering

Recovery of lithium, iron and phosphorus from spent LiFePO4 batteries using stoichiometric sulfuric acid leaching system Huan Li, Shengzhou Xing, Yu Liu, Fujie Li, Hui Guo, Ge Kuang* Institute of Chemical Engineering and Technology, Fuzhou University, Fuzhou 350108, China * Corresponding author (G. Kuang), e-mail address: [email protected]; Tel.: 86-13950286251. Mailing address: Room 218, Building No. 6, Xueyuan Road No. 2, Shangjie Town, Fuzhou City, Fujian Province, China 350108.

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ABSTRACT A selective leaching process is proposed to recover Li, Fe and P from the cathode materials of spent lithium iron phosphate (LiFePO4) batteries. It was found that using stoichiometric H2SO4 at low concentration as leachant and H2O2 as oxidant, Li could be selectively leached into solution while Fe and P could remain in leaching residue as FePO4, which is different from the traditional process of using excess mineral acid to leach all the elements into solution. Under the optimized conditions (0.3 M H2SO4, H2O2/Li molar ratio 2.07, H2SO4/Li molar ratio 0.57, 60 oC and 120 min), the leaching rates of 96.85 % for Li, 0.027 % for Fe and 1.95 % for P were recorded. The Li contained in solution was then recovered by introducing Na3PO4 as precipitant. Around 95.56 % Li was precipitated and recovered in the form of Li3PO4 under the experimental conditions. In addition, the FePO4 in the leaching residue was directly recovered by burning at 600 oC for 4 h to remove carbon slag. This study illustrates an effective process for the recycling of spent LiFePO4 batteries in a simple, efficient and cost-effective way, which makes it potential to be industrially applied.

KEYWORDS: Lithium iron phosphate batteries; Recovery; Stoichiometric; Sulfuric acid; Selective leaching; Lithium phosphate; Iron phosphate.

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INTRODUCTION For over a decade now, lithium-ion batteries (LIBs) have been considered the best power source for sustainable transport system that can operate at a higher voltage and achieve a higher energy density than the previously commercialized batteries and have been applied widely in electric vehicles (EVs) and hybrid electric vehicles (HEVs)1-3, with the annual production of LIBs increased by 800 % worldwide from 2000 to 20104. It is forecasted that there will be a huge growth for LIB industry with an estimated global market close to $32 billion by 20205. The olivine structured lithium iron phosphate (LiFePO4, LFP) first reported in the 1980s6-7, has been recognized as one of the most promising cathode material for LIB because of its advantages of high power capability, low cost, low toxicity, excellent thermal safety, and high reversibility8. Especially, LiFePO4 has been considered as a very safe cathode material because of its low electrochemical potential9. As a result, the LIB using LiFePO4 as cathode materials (abbreviated as LiFePO4 batteries) have been widely used in electronic equipment, large-scale energy storage devices, EVs and HEVs (particularly in electric bus) in recent years10-11. In 2014 alone, 12,500 tonnes of LiFePO4 were sold globally for using in LiFePO4 batteries12. As the major LiFePO4 production and consumption country, China’s shipment amount of LiFePO4 reached 32,400 tonnes in 2015, accounting for 65 % of the worldwide market. Driven by the rapid development of EVs and HEVs, the LiFePO4 battery market is expected to expand continuously with estimated increase rate of 20 % during 2016-202013. However, due to the huge usage and growing demand for LiFePO4 batteries, there will be plenty of spent LiFePO4 batteries obtained during production and after terminal lifespan that may soon bring serious problems14-16. For example, the organic electrolytes containing toxic LiPF6 and the metal ions will gradually transfer to soil and ground water when the spent LiFePO4 batteries are directly disposed by landfill or recycled in improper ways4. Moreover, the contents of some metals in spent LiFePO4 batteries are at fairly high levels and even greater than those in crude minerals17, which indicate considerable profitability for recycling. Particularly, the demand for lithium, a primary ingredient of LiFePO4 batteries, has experienced noticeable increase along with the development of EVs and HEVs. A lithium shortage may emerge in a few decades17. The recovery of lithium from spent LiFePO4 batteries, with the current recovery rate of less than 1 %18, would be an appropriate way to relieve the shortage of lithium resource and make the supply of lithium diversified18. Therefore, the recycling of spent LiFePO4 batteries is an important issue for both environmental protection and resource conservation. So far, there has been a large amount of literature published focusing on the recycling of LIBs containing

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precious and toxic metals, such as the previously commercialized LiCoO2 batteries and the ternary materials based LiNixCoyMn1-x-yO2 batteries, but largely neglected LiFePO4 batteries19. Overall, the existing methods for the recycling of spent LIBs can be divided into pyrometallurgical20-21, bio-hydrometallurgucal22-23 and hydrometallurgical10, 19, 24-32 methods, and the method of direct regeneration. Some recycling processes combine the above methods for recovering different materials and often involve some pretreatment steps to obtain individual components of spent LIBs. For the recycling of spent LiFePO4 batteries, as concluded in Table 1, the hydrometallurgical method and direct regeneration have been reported so far. The pyrometallurgical method, with heavy investments for smelting at high temperature and disposing of dangerous gases, has already been adopted by various industries for recovering Co, Ni, Fe and Cu from spent LIBs, but the lithium recovery is very limited since it is always oxidized and goes into the slag14, 18. The newly reported bio-hydrometallurgical method has attracted much attention due to its lower operational costs, high safety and environmental friendliness. However, its bottleneck is the very low leaching efficiency (ranging from several hours to days22) which almost makes it impossible to be industrially developed at current stage. The hydrometallurgical method, as a traditional method for the recycling of spent LIBs, involves the leaching of cathode materials obtained in pretreatment step and selectively separating the metals from the leaching solution which is then purified to obtain different products. In the reported leaching process of recycling spent LiFePO4 batteries (Table 1), the mineral acids of H2SO4 (mostly associated with H2O2), HCl and H3PO4 were used to leach all the elements from cathode materials into solution and followed with complicated separation process by chemical precipitation (using NaOH or NH3·H2O). However, in order to ensure all the metals are leached into a solution for recovery, the acid additions were largely excess and at high concentration (ranging from 2 to 6 M), which makes the following separation process require significant amount of alkali for neutralization19, 24, 27. Cai et al.27 optimized the H2SO4 leaching and alkali separation processes with LiFePO4: H2SO4: NaOH molar ratio of 1:8:15, which indicates the H2SO4 addition was 16 times higher than its stoichiometric value and brings high costs of both acid and alkali. However, there seems to be no discussion in the publications of leaching with less mineral acid. In addition, to simplify the process for separating metals after leaching, some organic acids as alternatives to mineral acids, such as citric acid25, 33, ascorbic acid25, lactic acid34, L-tartaric acid29 and formic acid26, have been reported for recycling LiCoO2 or LiNixCoyMn1-x-yO2 batteries in recent years. Nevertheless, the costs for those organic acids are inevitably higher than that of common mineral acids. Considering the recycling of spent LiFePO4 batteries is not as profitable as that of spent LIBs containing valuable metals (e.g. Co, Ni), achieving a reasonable cost in the above hydrometallurgical methods may be challenging. The method of direct regeneration

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refers to the recovery of cathode materials by some simple steps for direct reuse in battery fabrication. In the case of recycling spent LiFePO4 batteries, LiFePO4 powders were directly seperated and recovered from cathodes by heating at high temperature or soaking in organic solvent (Table 1). However, the recovered cathode materials easily contain impurities, and their structure is usually destroyed after numerous charging and discharging cycles, resulting in poor electrochemical performance in its direct reuse27,

35-36

. Overall, if an

industrially feasible process for the recycling of spent LiFePO4 batteries is to be developed, it is essential to make the process more simple, high-efficient, cost-effective and eco-friendly. Table 1 The reported methods for the recycling of spent LiFePO4 batteries Recycling method

Reagents/Process

Products

Ref.

Hydrometallurgical

H2SO4 and H2O2 as leaching agents, NaOH as precipitant, with

Fe(OH)3, FePO4·2H2O

27

method

LiFePO4: H2SO4: NaOH molar ratio of 1:8:15

and Li3PO4

6 M HCl as leaching agent, 6.25 % NH3·H2O as precipitant

FePO4·2H2O

24

H3PO4 as leaching agent with LiFePO4: H3PO4 molar ratio of

FePO4·2H2O and

10

1:3.16

LiH2PO4

2.5 M H2SO4 as leaching agent, NH3·H2O and Na2CO3 as

FePO4·2H2O and

precipitants

Li2CO3

Heating cathode scraps at 400-600 oC for 30 min under N2

LiFePO4

37

Heating cathode powders at 650 oC for 1 h

LiFePO4

35

Soaking cathode plates in DMAC solvent at 30 oC for 30 min

LiFePO4

36

Direct regeneration

19

Different from the traditional process of using excess and high concentration mineral acid to leach all the elements into solution and separate them subsequently, in this study, near stoichiometric H2SO4 at low concentration associating with H2O2 were used to selectively leach Li into solution from the cathode materials of spent LiFePO4 batteries and, simultaneously, Fe and P could be remained in the leaching residue, which means both leaching and separation were achieved in one step of leaching. As a result, the recycling process was largely simplified. This study uses common reagents and simple process to recover Li, Fe and P from spent LiFePO4 batteries, which could be promising to be industrially applied.

EXPERIMENTAL SECTION Materials and reagents. The spent LiFePO4 batteries used in this study (supplied by Shenzhen Just Real Power Tech Co., Ltd, Shenzhen, China) is a kind of spent power LIBs using LiFePO4/C as cathode materials. All the chemicals, including H2SO4, H2O2, Na3PO4·12H2O, NaOH, were of analytical grade purchased from Fuzhou Guangda Chemical Co., Ltd, Fuzhou, China. All the solutions used in this study were prepared with ultrapure 5



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water (electrical conductivity < 0.055 µs/cm, UPH-ΙΙ-5/10/20T, Ulupure Technology Co., Ltd). To obtain cathode materials for the leaching process, the spent LiFePO4 batteries were first subjected to a pretreatment process. (SI, page S2). The obtained cathode material was found to be LiFePO4 (Fig. S1) and its major elemental contents (wt. %) were 30.80 % Fe, 3.85 % Li and 17.05 % P, respectively (SI, page S2). Selective leaching of cathode materials. 5 g cathode materials were mixed with a different amount of H2SO4 and H2O2 in a three-neck flask to conduct each leaching experiment. Among all the leaching experiments, the stirring speed was fixed at 200 r/min. The oxidation-reduction theory was used to leach and separate Li and Fe from the cathode materials. During the leaching process, the Fe2+ in LiFePO4 would be oxidized to Fe3+ by H2O2 and then react with PO43- to form FePO4 precipitation. The Li was expected to leach out from cathode materials and report to solution. Therefore, Li and Fe would be separated during the selective leaching process. After vacuum filtration and drying at 120 oC for 4 h, the obtained residue was weighted by analytical balance (BS 224S, Sartotius). A certain amount of leaching residue (dissolved in aqua regia solution, HNO3/HCl = 1:3, v/v) and leaching solution were sampled from each experiment to measure the Li and Fe contents by inductively coupled plasma-optical emission spectrometry (ICP-OES, ICPE-9000, Shimadzu Co., Ltd). The reactions during leaching process can be represented as: 2LiFePO4 + H2SO4 + H2O2 → Li2SO4 + 2FePO4↓ + 2H2O

(1)

In order to establish the technical feasibility of the leaching of cathode materials and separation of Li and Fe during leaching process, the effects of different variables on the leaching rates of Li and Fe were evaluated. The pH of the filtrate of leaching solution, as an important parameter for FePO4 precipitation, was also measured by pH meter (PHS-3C, Shanghai INESA Scientific Instrument Co., Ltd). Recovery of Li from leaching solution. After selective leaching, the Li was expected to be separated with Fe and present in solution for further recovery. Before recovering Li, the leaching solution was first treated by adding NaOH to remove minor impurities, resulting in a small number of residues generated. To avoid possible Li loss by co-precipitation, the residues can be recycled to the next cycle of leaching process. Afterwards, the leaching solution was heated to concentrate, and stoichiometric sodium phosphate dodecahydrate (Na3PO4·12H2O) was then introduced for the precipitation and recovery of Li3PO417. The precipitation reaction can be represented as: 3Li2SO4 + 2Na3PO4 → 3Na2SO4 + 2Li3PO4↓

(2)

The precipitation experiment was conducted at 65 oC for 2 h with stirring speed of 250 r/min and was repeated 5 times. Since the solubility of Li3PO4 decreases with temperature increasing, a higher temperature can

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make more Li be precipitated. The precipitated Li3PO4 was then collected through filtrating and washed with 80 o

C deionized water to eliminate the excess Na3PO4. The Li contents before and after precipitation were

measured by ICP-OES for the calculation of Li3PO4 precipitation %. The crystal structure of the Li3PO4 product was measured by X-ray diffraction (XRD, MiniFlex II, Rigaku Co., Ltd). Its surface characteristic and particle size were also characterized by scanning electron micrometer (SEM, Nova NanoSEM 230, FEI Technologies Inc) and laser particle size analyzer (Mastersizer 2000, Malvern Instruments Co., Ltd), respectively. Analysis of leaching residue. During leaching step, the Fe2+ in the cathode materials could be easily oxidized to Fe3+ by H2O2 and was then expected to be precipitated as FePO4 at a proper pH range. After filtration, the FePO4 would accordingly be contained in leaching residue. Also, the carbon slag from the coating layer on LiFePO4 would be present in the residue. In order to confirm the form of the precipitation of Fe, the leaching residue was treated by burning at 600 oC for 4 h to remove carbon slag and was then tested by XRD.

RESULTS AND DISCUSSION Effects of various variables on the leaching rates of Li and Fe Effect of H2SO4 concentration. To study the effect of acid concentration on the Li and Fe leaching rates, experiments with different H2SO4 concentrations were conducted at H2O2/Li molar ratio (molar ratio between the H2O2 added and Li contained in the experimented cathode materials) of 2.96, leaching temperature of 60 oC, liquor to solid (L/S) ratio of 10 mL/g and leaching time of 120 min. The results are shown in Fig. 1a. In order to clearly reveal the change of H2SO4/Li molar ratio (molar ratio between the H2SO4 added and Li contained in the experimented cathode materials) with the increase of H2SO4 concentration, additional x axis of H2SO4/Li molar ratio is also added in Fig. 1a. With the H2SO4 concentration increasing from 0.1 to 0.3 M, the leaching rate of Li increased significantly from 35.19 to 95.74 % and the pH of filtrate decreased from 7.15 to 3.66, while the Fe always remained at a low leaching rate (less than 0.012 %). However, when the H2SO4 concentration continuously rose from 0.3 to 1.0 M resulting in the H2SO4/Li molar ratio rising from 0.55 to 1.82, the Fe was leached significantly with leaching rate increasing from 0.0027 to 78.39 % and the leaching rate of Li increased slightly (from 95.74 to 99.88 %). This means that the precipitated Fe was gradually becoming soluble with pH decreasing. In order to achieve the maximum separation of Li and Fe and, simultaneously, make more Li leach into solution, 0.3 M H2SO4 was chosen in further experiments. Under this concentration, the H2SO4/Li molar ratio was 0.55.

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Figure 1 Effects of various variables on the leaching rates of Li and Fe. (a) H2SO4 concentration; (b) H2O2/Li molar ratio; (c) temperature; (d) H2SO4/Li molar ratio; (e) time.

Effect of H2O2/Li molar ratio. H2O2, used as oxidant or reductant, has been shown to enhance the dissolution of Li, Co, Mn, Ni and Cu from spent LiCoO2 and LiNixCoyMn1-x-yO2 batteries30, 38-41. In order to investigate the effect of H2O2 addition on the extraction rates of Li and Fe, some experiments with different H2O2/Li molar ratio were performed. The leaching experiments were conducted for 120 min at 60 oC with H2SO4 concentration 0.3 M, L/S ratio 10 mL/g (H2SO4/Li molar ratio 0.55) and stirring speed 200 r/min. The results (Fig. 1b) indicate that when associating with H2O2, the leaching of Li was enhanced considerably and that of Fe was inhibited accordingly. The reasonable explanation is H2O2 served as oxidant transferring Fe from bivalent to trivalent state 8


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which favored the formation of FePO4 precipitate and hence made the structure of LiFePO4 easily decompose in H2SO4 solution (eq. (1)). When the H2O2/Li molar ratio increased from 0 (no H2O2 added) to 2.07, the Li leaching rate rose by around 45 % (from 49.25 to 96.08 %) and the leaching rate of Fe decreased from 36.75 to 0.0024 %. Meanwhile, the pH of leaching solution experienced an upward trend which is because the oxidation-reduction reaction between H2O2 and Fe2+ consume H+ (eq. (3)). However, when the H2O2/Li molar ratio was greater than 2.07, both the leaching rates of Li and Fe remained relatively stable indicating that the leaching reaction nearly reached equilibrium. Considering the more addition of H2O2 make the reaction more intense and easily produce a large amount of foam overflowing the reactor, the H2O2/Li molar ratio of 2.07 was recommended for the following experiments. At this ratio, the volume fraction of H2O2 added was 2.02 vol. % and the pH of filtrate was 3.74. As can be seen from eq. (1), the theoretical H2O2/Li molar ratio is 0.5, which means the proper addition amount of H2O2 was about 4 times as high as its theoretical value. 2Fe2++H2O2+2H+ → 2Fe3++2H2O

(3)

Effect of reaction temperature. The effect of reaction temperature on the Li and Fe leaching rates was investigated in the range of 25 to 80 oC. The other conditions were as follows: H2SO4 concentration 0.3 M, H2O2/Li molar ratio 2.07, L/S ratio of 10 mL/g (H2SO4/Li molar ratio 0.55) and leaching time of 120 min. The results (Fig. 1c) show that the reaction temperature had no obvious influence on the leaching rates of Li and Fe. Even when the reaction temperature was at 25 oC, the leaching rate of Li could reach 92.60 % and that of Fe could be as low as 0.00013 %. In the studied range of temperature, the pH of leaching solution always remained between 3.63 and 3.82, which made Fe be precipitated and separated with Li almost completely. Since leaching rate of Li peaked at 96.08 % at the temperature of 60 oC, this temperature was chosen for the further experiments. However, as the temperature has a slight influence on the leaching of Li and Fe, the temperature lower than 60 oC is also feasible, particularly when the costs for heating energy are firstly considered in the industrial application. Effect of H2SO4/Li molar ratio. In order to clearly reveal the relationship between the amounts of H2SO4 and LiFePO4, experiments with different H2SO4/Li molar ratio instead of L/S ratio was conducted under the following conditions: H2SO4 concentration of 0.3 M, H2O2/Li molar ratio of 2.07, leaching temperature of 60 oC and leaching time of 120 min. Since both the mass of LiFePO4 used for each experiment and the concentration of H2SO4 were fixed, the higher H2SO4/Li molar ratio means the more H2SO4 added and the more total volume of the leaching solution. As shown in Fig. 1d, the H2SO4/Li molar ratio could obviously affect the leaching of Li. With the molar ratio increasing in the whole selected range, Li leaching rate rose from 67.84 to 98.40 %. While,

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when the molar ratio was in the range from 0.33 to 0.57, there was no obvious change in the leaching rate of Fe. However, with the range continuously extending, more Fe was leached to be soluble in solution. When the molar ratio was 0.65, the leaching rate of Fe reached 0.22 %. To make the volume of leaching solution as less as possible to reduce the following evaporation costs and decrease the addition amount of H2SO4, the H2SO4/Li molar ratio of 0.57 (equivalent to L/S ratio of 10.5 mL/g) was selected for the further experiments. At this ratio, the pH of filtrate was at 3.24. From eq. (1), we can know the appropriate addition amount of H2SO4 was very close to its theoretical value (experimental ratio of 0.57 vs. theoretical ratio of 0.50), which indicates near stoichiometric amount of H2SO4 could already achieve expected effect for the leaching process. As a result, the addition amount of alkali in the following step of impurities removal can be reduced. Effect of leaching time. The effect of leaching time was investigated in the range from 60 to 150 min. The other conditions were as follows: H2SO4 concentration of 0.3 M, H2O2/Li molar ratio of 2.07, leaching temperature of 60 oC and H2SO4/Li molar ratio of 0.57. As can be seen from Fig.1e, when the leaching time rose from 60 to 80 min, the leaching rate of Li increased from 76.48 to 95.20 % and that of Fe dropped marginally from 3.95 to 0.0084 %. With the leaching time further going up, the Li leaching rate remained at a stable level and peaked at 96.85 % at 120 min. In the meantime, there was no obvious change of Fe leaching rate and the pH of filtrate was always remaining from 3.62 to 3.87. The detailed results of selected experiments (t = 80, 100 and 120 min) with relatively stable data have been listed in Table 2. From the table, we can know that around 99.98 % Fe together with 98.03 % P were precipitated and 95.75 % Li was leached during the selective leaching process of the selected experiments. The concentrations of Fe and P in the leaching solution were around 1.387 mg/L and 0.319 g/L, respectively. In order to achieve a maximum leaching rate of Li, 120 min (with filtrate pH of 3.66) was considered as optimized leaching time. Table 2 Experimental results with different leaching time. [H2SO4] = 0.3 M; H2O2/Li molar ratio = 2.07; T = 60 oC and H2SO4/Li molar ratio = 0.57. Time (min) 80 100 120 Mean

Leaching solution obtained after filtration Li (g/L) Fe (mg/L) 3.497 1.228 3.504 1.216 3.546 1.717 3.516 1.387

P (g/L) 0.324 0.323 0.312 0.319

pH 3.72 3.87 3.66 3.75

Leaching rate (%) Li Fe 95.09 0.013 95.30 0.011 96.85 0.027 95.75 0.017

P 1.98 1.97 1.95 1.97

Recovery of Li from the leaching solution The results obtained by repeating the experimental procedures five times are listed in Table S1. They reveal that the Li3PO4 precipitation reached around 95.56 % in the first cycle of recycling process under the experimental conditions. The obtained Li3PO4 can also be further purified to meet the requirement of

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battery-grade materials. The XRD pattern (Fig. 2a) of the precipitated Li3PO4 indicates that its characteristic peaks agree well with the standard Li3PO4 pattern. The SEM image (Fig. 2b) illustrates that the obtained Li3PO4 was composed of agglomerated globules. The particle size distribution (Fig. 2c) of the Li3PO4 is measured to be 18.964 µm.

Figure 2 XRD pattern (a), SEM image (b), and particle size distribution (c) of the precipitated Li3PO4.

The analysis of leaching residue After treating by burning, the residue was measured by XRD. As shown in the Fig. 3, the XRD pattern is in good coincidence with the standard pattern of FePO4, which proves that the Fe was precipitated as FePO4 and reported to leaching residue. Therefore, the Fe was recovered in the form of FePO4. This result agrees well with the previous publication27, in which indicates that Fe3+ would be precipitated as FePO4 rather than Fe(OH)3 at the pH of around 3.40 in the presence of PO43- in a sulfate solution.

Figure 3 XRD pattern of leaching residue 11



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Development of a novel recycling process for spent LiFePO4 batteries Based on the above results and analyses, a novel recycling process for spent LiFePO4 batteries under the leaching with H2SO4 and H2O2 is presented in Fig. 4. The spent LiFePO4 batteries were first subjected to a pretreatment step to obtain the cathode materials for the leaching process, which has been well studied by previous researchers. After pretreatment, the cathode materials obtained from the spent LiFePO4 batteries were then leached with stoichiometric H2SO4. The H2O2 was introduced for enhancing leaching effect and oxidizing Fe2+ in LiFePO4 to Fe3+ which will favor the subsequent precipitation of FePO4. The optimized leaching conditions are as follows: 0.3 M H2SO4, H2O2/Li molar ratio 2.07, H2SO4/Li molar ratio 0.57, 60 oC and 120 min. After filtration, the solution containing Li and the leaching residue containing FePO4 and C were obtained, respectively. The residue was then treated by calcination at 600 oC for 4 h to remove carbon slag and recover FePO4. While, the leaching solution was purified by adding alkali (NaOH) solution and concentrated by evaporation. After that, Na3PO4 was introduced to the leaching solution for the precipitation and recovery of Li as Li3PO4 product. Finally, the mother solution was recycled to commence the next cycle of the alkali leaching of cathode plates.

Spent LiFePO4 batteries Pretreatment Discharing & disassembling Anode plates

Cathode plates

Ultrasonic leaching

Dilute alkali leaching

Anode materials

Cu-foils

Cathode materials

NaOH Solution

Al-foils

Acid leaching Liquor

Solid

Purifying

FePO4/C 600 oC

Liquor

FePO4

Solution

NaOH Solution Solid

Residue (trace)

Concentrating Concentration solution Solid

Crude Li3PO4 Washing

Na3PO4

Liquor

Mother solution Water

Drying Li3PO4

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Figure 4 Flow chart for the leaching and recovery process.

SUPPORTING INFORMATION Details about the pretreatment process, XRD analysis of cathode materials and detailed data of the Li precipitation.

REFERENCES 1.

Tarascon, J.-M., Is lithium the new gold? Nat. Chem. 2010, 2 (6), 510-510. DOI: 10.1038/nchem.680.

2.

Wang, J.; Sun, X., Understanding and recent development of carbon coating on LiFePO 4 cathode

materials for lithium-ion batteries. Energ. Environ. Sci. 2012, 5 (1), 5163-5185. DOI: 10.1039/C1EE01263K. 3.

Palacín, M. R.; de Guibert, A., Why do batteries fail? Science 2016, 351 (6273), 1253292. DOI:

10.1126/science.1253292. 4.

Zeng, X.; Li, J.; Singh, N., Recycling of Spent Lithium-Ion Battery: A Critical Review. Crit. Rew. Env. Sci.

Tec. 2013, 44 (10), 1129-1165. DOI: 10.1080/10643389.2013.763578. 5.

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 Sustain. Chem. Eng. 2016, 4 (12), 7041-7049. DOI: 10.1021/acssuschemeng.6b01948. 6.

Manthiram, A.; Goodenough, J., Lithium insertion into Fe2(MO4)3 frameworks: Comparison of M = W

with M = Mo. J. Solid State Chem. 1987, 71 (2), 349-360. 7.

NADIRI, A.; Delmas, C.; Salmon, R.; Hagenmuller, P., Chemical and electrochemical alkali metal

intercalation in the 3D-framework of Fe2(MoO4)3. Revue de chimie minérale 1984, 21 (4), 537-544. 8.

Xu, Z.; Gao, L.; Liu, Y.; Li, L., Review - Recent Developments in the Doped LiFePO4 Cathode Materials

for Power

Lithium Ion Batteries. J. Electrochem. Soc. 2016, 163 (13), A2600-A2610. DOI:

10.1149/2.0411613jes. 9.

Goodenough, J. B.; Kim, Y., Challenges for Rechargeable Li Batteries. Chem. Mater. 2010, 22 (3),

587-603. DOI: 10.1021/cm901452z. 10. Bian, D.; Sun, Y.; Li, S.; Tian, Y.; Yang, Z.; Fan, X.; Zhang, W., A novel process to recycle spent LiFePO4 for synthesizing LiFePO4/C hierarchical microflowers. Electrochim. Acta 2016, 190, 134-140. DOI: 10.1016/j.electacta.2015.12.114. 11. Wang, S.; Yang, H.; Feng, L.; Sun, S.; Guo, J.; Yang, Y.; Wei, H., A simple and inexpensive synthesis route for

LiFePO4/C

nanoparticles

by

co-precipitation.

J.

Power

Sources

10.1016/j.jpowsour.2013.01.124.

13


2013,

233,

43-46.

DOI:


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

Page 14 of 17

12. Global and China Lithium Iron Phosphate (LiFePO4) Material and Battery Industry Report, 2015-2018; Research In China: Beijing, China, July 2015, 2015. 13. Global and China Lithium Iron Phosphate (LiFePO4) and Battery Industry Report, 2016-2020; Research In China: Beijing, China, December 2016, 2016. 14. 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. DOI: 10.1016/j.jpowsour.2012.01.152. 15. 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.

DOI:

10.1080/21622515.2013.853105. 16. Ramoni, M. O.; Zhang, H.-C., End-of-life (EOL) issues and options for electric vehicle batteries. Clean Technol. Envir. Policy 2013, 15 (6), 881-891. DOI: 10.1007/s10098-013-0588-4. 17. Kuang, G.; Li, H.; Hu, S.; Jin, R.; Liu, S.; Guo, H., Recovery of aluminium and lithium from gypsum residue obtained in the process of lithium extraction from lepidolite. Hydrometallurgy 2015, 157, 214-218. DOI: 10.1016/j.hydromet.2015.08.020. 18. Swain, B., Recovery and recycling of lithium: A review. Sep. Purif. Technol. 2017, 172, 388-403. DOI: 10.1016/j.seppur.2016.08.031. 19. Zheng, R.; Zhao, L.; Wang, W.; Liu, Y.; Ma, Q.; Mu, D.; Li, R.; Dai, C., Optimized Li and Fe recovery from spent lithium-ion batteries via solution-precipitation method. Rsc Adv. 2016, 6 (49), 43613-43625. DOI: 10.1039/C6RA05477C. 20. Kim, D.-S.; Sohn, J.-S.; Lee, C.-K.; Lee, J.-H.; Han, K.-S.; Lee, Y.-I., Simultaneous separation and renovation of lithium cobalt oxide from the cathode of spent lithium ion rechargeable batteries. J. Power Sources 2004, 132 (1–2), 145-149. DOI: 10.1016/j.jpowsour.2003.09.046. 21. Träger, T.; Friedrich, B.; Weyhe, R., Recovery Concept of Value Metals from Automotive Lithium‐Ion Batteries. Chem. Ing. Tech. 2015, 87 (11), 1550-1557. DOI: 10.1002/cite.201500066. 22. 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. Clean. Prod. 2016, 116, 249-258. DOI: 10.1016/j.jclepro.2016.01.001. 23. 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. DOI: 10.1016/j.wasman.2016.10.034.

14


Page 15 of 17

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


24. Shin, E. J.; Kim, S.; Noh, J.-K.; Byun, D.; Chung, K. Y.; Kim, H. S.; Cho, B. W., A Green Recycling Process Designed for LiFePO4 Cathode Materials for Li-ion Batteries. J. Mater. Chem. A 2015, 3 (21), 11493-11502. DOI: 10.1039/C5TA02540K. 25. Nayaka, G. P.; Manjanna, J.; Pai, K. V.; Vadavi, R.; Keny, S. J.; Tripathi, V. S., Recovery of valuable metal ions from the spent lithium-ion battery using aqueous mixture of mild organic acids as alternative to mineral acids. Hydrometallurgy 2015, 151, 73-77. DOI: 10.1016/j.hydromet.2014.11.006. 26. Gao, W.; Zhang, X.; Zheng, X.; Lin, X.; Cao, H.; Zhang, Y.; Sun, Z., Lithium Carbonate Recovery from Cathode Scrap of Spent Lithium-Ion Battery: A Closed-Loop Process. Environ. Sci. Technol. 2017, 51 (3), 1662-1669. DOI: 10.1021/acs.est.6b03320. 27. Cai, G.; Fung, K. Y.; Ng, K. M.; Wibowo, C., Process Development for the Recycle of Spent Lithium Ion Batteries by Chemical Precipitation. Ind. Eng. Chem. Res. 2014, 53 (47), 18245-18259. DOI: 10.1021/ie5025326. 28. Hwang, S. O.; Chae, B. M.; Kim, D. H.; Park, K. S.; Go, A. R.; Lee, S. W. Recovery of Nickel from Waste Lithium Ion Secondary Battery and Fabrication of Nickel Nanopowder, Key Eng. Mat. 2017, 733, 22-26. DOI: 10.4028/www.scientific.net/KEM.733.22. 29. He, L.-P.; Sun, S.-Y.; Mu, Y.-Y.; Song, X.-F.; Yu, J.-G., Recovery of lithium, nickel, cobalt, and manganese from spent lithium-ion batteries using L-tartaric acid as a leachant. ACS Sustain. Chem. Eng. 2016. DOI: 10.1021/acssuschemeng.6b02056. 30. Zou, H.; Gratz, E.; Apelian, D.; Wang, Y., A novel method to recycle mixed cathode materials for lithium ion batteries. Green Chem. 2013, 15 (5), 1183-1191. DOI: 10.1039/C3GC40182K. 31. Pranolo, Y.; Zhang, W.; Cheng, C. Y., Recovery of metals from spent lithium-ion battery leach solutions with

a

mixed

solvent

extractant

system.

Hydrometallurgy

2010,

102

(1–4),

37-42.

DOI:

10.1016/j.hydromet.2010.01.007. 32. Chen, L.; Tang, X.; Zhang, Y.; Li, L.; Zeng, Z.; Zhang, Y., Process for the recovery of cobalt oxalate from spent lithium-ion batteries. Hydrometallurgy 2011, 108 (1), 80-86. DOI: 10.1016/j.hydromet.2011.02.010. 33. Yao, L.; Feng, Y.; Xi, G., A new method for the synthesis of LiNi1/3Co1/3Mn1/3O2 from waste lithium ion batteries. Rsc Adv. 2015, 5 (55), 44107-44114. DOI: 10.1039/c4ra16390g. 34. Li, L.; Fan, E.; Guan, Y.; Zhang, X.; Xue, Q.; Wei, L.; Wu, F.; Chen, R., Sustainable Recovery of Cathode Materials from Spent Lithium-Ion Batteries Using Lactic Acid Leaching System. ACS Sustain. Chem. Eng. 2017. DOI: 10.1021/acssuschemeng.7b00571.

15



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

Page 16 of 17

35. 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. DOI: 2500-2506. 10.1039/C5GC02650D. 36. Song, X.; Hu, T.; Liang, C.; Long, H.; Zhou, L.; Song, W.; You, L.; Wu, Z.; Liu, J., Direct regeneration of cathode materials from spent lithium iron phosphate batteries using a solid phase sintering method. RSC Adv. 2017, 7 (8), 4783-4790. DOI: 10.1039/C6RA27210J. 37. Kim, H. S.; Shin, E. J., Re-synthesis and Electrochemical Characteristics of LiFePO4 Cathode Materials Recycled

from

Scrap

Electrodes.

B.

Korean

Chem.

Soc.

2013,

34

(3),

851-855.

DOI:

10.5012/bkcs.2013.34.3.851. 38. Dorella, G.; Mansur, M. B., A study of the separation of cobalt from spent Li-ion battery residues. J. Power Sources 2007, 170 (1), 210-215. DOI: 10.1016/j.jpowsour.2007.04.025. 39. Wang, H.; Friedrich, B., Development of a Highly Efficient Hydrometallurgical Recycling Process for Automotive Li-ion Batteries. J. Sustain. Metall. 2015, 1 (2), 168-178. DOI: 10.1007/s40831-015-0016-6. 40. 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. DOI: 10.1016/j.jhazmat.2015.02.064. 41. Meshram, P.; Abhilash; Pandey, B. D.; Mankhand, T. R.; Deveci, H., Comparision of Different Reductants in Leaching of Spent Lithium Ion Batteries. JOM 2016, 68 (10), 1-11. DOI: 10.1007/s11837-016-2032-9.

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TOC/Abstract Art For Table of Contents Use Only

Synopsis: A green and simple process was developed to recover Li, Fe and P from spent LiFePO4 batteries with near stoichiometric H2SO4 leaching system.

17


Recovery of Lithium, Iron, and Phosphorus from Spent LiFePO4

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