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Recovery of lithium and cobalt from waste lithium-ion batteries through a selective isolation-suspension approach
Sustainable Materials and Technologies 23 (2020) e00139
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Sustainable Materials and Technologies journal homepage: www.elsevier.com/locate/susmat
Recovery of lithium and cobalt from waste lithium-ion batteries through a selective isolation-suspension approach Samane Maroufi ⁎, Mohammad Assefi, Rasoul Khayyam Nekouei, Veena Sahajwalla Centre for Sustainable Materials Research and Technology (SMaRT), School of Materials Science and Engineering, University of New South Wales, Sydney 2052, Australia
a r t i c l e
i n f o
Article history: Received 18 June 2019 Received in revised form 16 August 2019 Accepted 14 November 2019
Keywords: Lithium-ion batteries Recycling Lithium Cobalt Thermal isolation
a b s t r a c t This paper describes a selective thermal isolation-suspension process for the recovery of Li and Co from spent Lithium-Ion Batteries (LIBs). The cathodic part of LIBs, which are mainly composed of Li, Al and Co, sourced from electronic waste (e-waste) was first subjected to a suspension stage for removing Al. XRD analysis of the cathodic sample free of Al (C1) revealed that C1 was in the form of LiCoO2. Thermal behavior of C1 was also examined against time and temperature using Thermogravimetric Analysis (TGA). Thermal isolation of C1 was carried out via reduction in argon atmosphere using activated carbon at temperature in the range of 600 °C to 800 °C for 30 min. At 600 °C, no dissociation of the initial compound of LiCoO2 was observed. At 800 °C Li totally liberated from the sample in form of gas and cobalt oxide was reduced to the metallic cobalt. However, at 700 °C, Li was thermally isolated in form of solid lithium carbonate and separated from Co. Temperature of 700 °C was selected as the optimum temperature for thermal isolation of Li which resulted in dissociation of LiCoO2 into Co, CoO and Li2CO3. After thermal isolation at 700 °C, the resulting mixture (C2) was dispersed into distilled water, placed in a cold-water bath with temperature of 0 °C and was allowed to gradually dissolve in water for 1 h. After filtration and washing using a centrifuge, the solution was subjected to ICP analysis and the undissolved particles were dried in an oven overnight prior to further reduction at 700 °C for full reduction of cobalt oxide to metallic cobalt. The simple and environmentally friendly approach proposed in this work for the recovery of Li and Co from spent LIBs can potentially help in addressing the problems associated with waste LIBs and depletion of natural resources. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Batteries are a fast-growing and problematic waste stream in Australia, caused by our increasing reliance on electronic devices and our low recycling rates. In Australia, some 345 million handheld batteries are consumed annually. Only 6% of these by weight and 4% by count are currently recycled with the majority disposed of in landfills (around 183 million) or informally stockpiled [1]. This poses serious environmental and health risks as batteries can explode or degrade and are highly toxic. Additionally, 15% of Australia's large landfills and 65% of medium-sized landfills are unlined, where metals can leak and contaminate soil and groundwater [2]. The end-of-life batteries which cannot be reused in other energy supply-demands should be recycled so their constituent parts can be reformed for reuse as high-value materials. The complex mix of metals, non-metals and plastics in a typical battery means processing currently is challenging and costly, and this results in low battery recycling rates with the resultant recovered materials seen as being of low value. ⁎ Corresponding author. E-mail address: s.maroufi@unsw.edu.au (S. Maroufi).
https://doi.org/10.1016/j.susmat.2019.e00139 2214-9937/© 2019 Elsevier B.V. All rights reserved.
At the same time, batteries contain non-renewable resources in high demand such as lithium (Li), cobalt (Co) and nickel (Ni). Demand for these metals is being driven by growth in the development and sales of electric vehicles, consumer electronics and domestic energy storage devices [3]. Recently, the five-year historical average price of Co tripled and is now double that average, making it commercially attractive to find ways to recover and reuse Co [4,5]. Recovering resources from batteries will reduce pressure on the world's finite virgin resources. The high price and finite nature of the minerals containing such metals make recovery very attractive in terms of environmental, economic and social benefits. Lithium-Ion Batteries (LIBs) are a popular type of rechargeable batteries which are widely used in portable electronics. Such batteries are composed of several electrochemical cells in which lithium ions move between the anode and the cathode electrodes. LIBs are mainly composed of cathode, anode, electrolyte, and separator, which all are covered by a metal case and plastic cover. The cathode is commonly made of a lithium metal oxides such as lithium cobalt oxide (LiCoO2 or LCO), lithium nickel oxide (LiNiO2), lithium vanadium oxide (LiV2O3), lithium manganese oxides (LiMn2O4 or LMO), lithium iron phosphate
2
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
Fig. 2. XRD spectrum of the cathodic materials after removing Al (C1).
Fig. 1. Flow chart of the experimental procedure for the recycling of Li and Co from spent LIBs.
(LiFePO4 or LFP) or a complex compound like (LiNi0.33Mn0.33Co0.33O2 or NMC), and the anode is graphite [6]. Several pyrometallurgical and hydrometallurgical processes have been suggested by researchers across the globe for the recycling of different batteries [6–12]. In hydrometallurgical processes, multiple steps of leaching and separation are involved in the separation of different elements. Most of these reported recycling techniques are based on recovery of only a particular element from batteries, not all or most of the constituent parts, and these reported techniques [6] are in most cases very complex and not commercially viable. In general, hydrometallurgical process includes the steps of dismantling, crushing, leaching, purification, separation and product preparation among which leaching has been the center of attention [13–15]. Several researchers have worked on recovery of metals from cathode part of the LIBs such as LiCoO2 [16–20], NixCoyMn1-x-yO2 [15–21], Li NixCoyMn1-x-yO2 [22,23]. It is worth noting that some of the transition metal ions (i.e., Co3+, Mn4+) are present at high valence (+3/4) in aqueous solution and therefore it is important to use a reducing agent to reduce the valence to a low valence state (2+). Many works have reported the use of Na2SO3, H2O2 [16,17] and ascorbic acid as reducing agent in their leaching process. In the pyrometallurgical technique, batteries are pyrolyzed and the metallic components are reduced and smelted in large furnaces at 1500 °C. In research reported by [12], LIB cathode was decomposed to lithium carbonate and cobalt oxide via heat treatment at 600 °C using graphite for 2 h. Thermal processing reduced the valence value of Co from 3+ to 2+, which resulted in facile leaching in 2.25 M H2SO4.
Table 1 ICP results of the cathodic part of LIB. Elements
Li
Co
Mn
Ni
Al
wt%
6.47
40.61
1.57
1.61
7.81
After leaching in H2SO4, Co and Li in the leaching liquor were further separated with 35% PC88 at the ratio of aqueous to organic (A:O) equalling 0.5, 25 °C and pH = 5.5. This study aims to address the challenges of achieving environmentally friendly recovery of Li and Co from LIBs via a novel two-step thermal isolation-suspension approach, using activated carbon as reducing agent and water as solvent. The thermal isolation step was performed via simple carbothermal reduction at temperatures in the range between 600 °C-800 °C in argon (Ar) using activated carbon as reducing agent. In the first process, LIB cathode powder was mixed with activated carbon and reduced in Ar which resulted in the formation of Co, cobalt oxide and lithium carbonate. This step was then followed by dissolution in cold water which led to the successful dissolution of Li2CO3 in water and residing cobalt oxide. The residual cobalt oxide was later reduced to metallic cobalt at 700 °C.The flow chart of the experimental procedure used in this work is shown in Fig. 1. 2. Characterization of materials and experimental procedure LIBs sourced from the Reverse E-waste Company, Sydney, Australia were discharged and then dismantled manually. The plastic cases were separated and the cell was cut longitudinally and the active components were separated from the plastic pieces. The cathode part which composed of aluminum (Al) foils coated by dioxide in double sides were separated. The separated foils were then pulverized into a fine powder using 30 s ring milling. 5 g of the resulting fine powder was dispersed into 50 ml of 2 M NaOH, then placed on a hot plate at temperature of 60 °C for 2 h. The powder was leached thoroughly and the resulting mixture was subsequently filtered to separate Al. The filtered powder was then dried in an oven overnight and then subjected to analysis using Inductively Coupled Plasma (ICP) technique. The analyzed composition of the separated oxide phase is listed in Table 1. The X-ray diffraction spectrum of the cathodic materials after removing Al (C1) is displayed in Fig. 2. From XRD pattern, strong characteristic peaks belong to lithium cobalt oxide (LiCoO2) can be observed while the peaks assigned to Al is not detectable, which is due to the detection limit of XRD. The thermal degradation behavior of the C1 sample was studied using Thermogravimetric Analysis (TGA); where the sample was heated from room temperature to 1000 °C at a heating rate of 20 °C.min−1 under nitrogen (N2) purge of 20 ml.min−1. TGA results are shown in. The initial observation from the mass loss versus temperature curve, Fig. 3a, indicates there is no change in the mass of the C1 up to 730 °C while at around 740 °C, a sharp decrease in the weight occurred which can be assigned to reduction of LiCoO2 to metallic cobalt, dissociation of Li from LiCoO2 and removal of oxygen, carbon and Li from the sample. The thermal-induced weight loss increases with temperature and around 65% of the sample remains at 1000 °C. The DTG curve provides visual evidence of the degradation process. Thermal degradation
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
3
Fig. 3. Thermogravimetric analysis of C1 at a heating rate of 20 °C.min−1 under nitrogen (N2) purge of 20 ml.min−1 a) weight loss and DTG curves versus temperature b) weight loss versus time.
of C1 sample against times was also examined while temperature was kept 600 °C, 700 °C and 800 °C and the results are displayed in Fig. 3b. As can be seen from Fig. 3b, the weight loss due to the heat treatment at 600 °C is negligible which indicates, LiCoO2 did not react with activated carbon and no decomposition took place at this temperature. With increasing temperature to 700 °C, at initial stages no trace of LiCoO2 decomposition can be found in weight loss versus time curve. With extending reaction time up to 40 min, the sample started to decompose and the mass of the sample continuously decreased over time. Although no degradation was detected when the sample was gradually heat treated from room temperature to 700 °C(Fig. 3a), however the result in Fig. 3b can confirm that thermal degradation behavior of the sample is affected by time. At 800 °C, a relatively sharp thermal decomposition can be conserved after 38 min of heat treatment.
X-ray diffraction spectrum of the samples after heat treatment at 600 °C, 700 °C and 800 °C are shown in Fig. 4a, b and c, respectively. XRD pattern of the sample after heat treatment at 600 °C (Fig. 4a) shows strong peaks assigning to LiCoO2 which indicate that LiCoO2 in the initial sample did not react with carbon and dissociation of Li from LiCoO2 did not occur at this temperature which agrees well with TGA result. With increasing temperature to 700 °C, the characteristic peaks of LiCoO2 completely disappeared and new peaks attributing to the phases of Co, cobalt oxide and lithium carbonate appeared. This shows that at 700 °C, LiCoO2 dissociated and carbothermal reduction of oxide phase occurred which resulted in the formation of the metallic cobalt. It has been proved that dissociation of LiCoO2 can occur according to the following equations [24]: Reaction. # Reaction
3. Results and discussions 3.1. Thermal isolation at low temperature After filtration, the C1 sample was mixed with activated carbon (Charcoal Norit supplied by Sigma) in a ratio of 5 to 1 (C1: AC). The resulting mixture was then placed in an alumina crucible inserted in a pre-heated tubular furnace (100 cm length × 5 cm diameter) at the target temperature (i.e., 600 °C, 700 °C, and 800 °C) under Ar purge (1 L. min−1) for a given period of time. The furnace was coupled with an Infrared gas analyzer (Advanced Optima AO2020, ABB Measurement and Analytics, Australia) for continuous measurement of non-condensable Syngas, e.g., CO, CO2 and CH4. The offgas was monitored to give an insight into the formation of lithium carbonate taking place at those temperatures and indicating the completion of the reaction. After heat treatment, the sample was kept in the cold zone of the furnace in Ar for 10 min. The resulting phases of the samples were further examined by XRD.
(1) (2) (3) (4) (5) (6)
C + 12LiCoO2→6Li2O + 4Co3O4 + CO2 C + 4LiCoO2→2Li2O + 4CoO + CO2 2Co3O4 + C→6CoO + CO2 Li2O + CO2→Li2CO3 2CoO + C→2Co + CO2 CO2 + C↔2CO
ΔG (kJ.mol−1) 600 °C
700 °C
800 °C
62.3
356.7
349.5
−4.1 −187.3 −175.0 34.5 134.9
−17.9 −205.2 −178.2 37.4 133.2
−31.2 −221.6 −185.6 40.3 131.5
In reaction with solid carbon at 700 °C, LiCoO2 first decomposes to Li2O and cobalt oxide as shown in reactions (1) and (2). The produced Li2O in return reacts with CO2 which results in the formation of Li2CO3 (reaction (4)). XRD pattern of the sample after heat treatment at 700 °C shows that cobalt oxide was partially reduced to the metallic cobalt (reaction (5)) and strong peaks corresponding to metallic cobalt is detected. With further increasing temperature to 800 °C, all peaks belonging to cobalt oxide and lithium cobalt oxide disappeared. This indicates that lithium carbonate becomes unstable when temperature rises
Fig. 4. XRD spectra of C1‑carbon mixture after heat treatment in Ar atmosphere at a) 600 °C, b) 700 °C and c) 800 °C for 60 min.
4
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
Fig. 5. Concentration of CO/CO2 gases generated during heat treatment in Ar atmosphere at a) 600 °C, b) 700 °C and c) 800 °C for 60 min.
to 800 °C, and liberate from the system in the form of gas. The remaining cobalt oxides were reduced to the metallic cobalt and no trace of cobalt oxide is detected from XRD pattern. The concentrations of CO, CO2 gases evolved from the system was monitored using the IR-gas analyzer. Fig. 5 shows the concentration of gases generated during the heat treatment at temperatures in the range of 600 to 800 °C. At 600 °C, the concentration of the evolved CO and CO2 was found to be limited which can be justified by the result of XRD. XRD pattern of the sample after heat treatment at 600 °C reveals that no dissociation took place at this temperature and LiCoO2 remained unaffected. With increasing temperature to 700 °C, concentration of CO2 raised quickly and reached to its maximum value within 10 min. This can be attributed to the rapid decomposition of LiCoO2 to LiO and cobalt oxide based on reaction (1)–(3). The evolved CO2 in return reacted with Li2O to form Li2CO3 which resulted in dropping the concentration of CO2. With further rising temperature to 800 °C, at initial stages of the reaction, concentration of CO2 quickly soared in a few minutes, which can be assigned to the quick decomposition of LiCoO2 to LiO2 and cobalt oxide (reactions (1)–(3)). With extending the reaction time, the concentration of CO2 dropped which is most probably due to the reaction between CO2 and LiO2 and the formation of Li2CO3. This stage is followed with a second increase in the concentration of CO2 while concentration of CO started to rise. The sharp increase in the concentration of CO in the off-gases can be clearly observed, implying that carbothermal reduction of cobalt oxide to metallic cobalt occurred. As can be seen from reaction (5), reaction of cobalt oxide with solid carbon takes place through Boudouard reaction (6), which results in the formation of CO. The second peak in the concentration of CO2 can be assigned to the Reduction of cobalt oxide to metallic cobalt, as shown in reaction (5). 3.2. Suspension using cold water Carbothermal reaction at 700 °C resulted in successful dissociation of LiCoO2 into Li2CO3, CoO and metallic cobalt. For the final separation of Li and Co, a facile technique of dissolution in cold water was applied. Solubility of lithium carbonate in water at ambient temperature is not very high owing to the fact that the electrostatic attraction between the very small lithium cation and the carbonate anion overpowers the attraction Table 2 ICP results of the sample after suspension in different solvents.
between these ions and the water molecules. However, solubility can increase with decreasing temperature to zero. The decrease in solubility of lithium carbonate in water with increasing temperature points to an entropy phenomenon. In other words, the lithium cation and the carbonate anion decrease overall entropy (i.e., by imposing order upon solvation) in solution. After carbothermal reduction, the resulting mixture was dispersed into distilled water, placed in a cold-water bath with temperature of 0 °C and was allowed to gradually dissolve in water for 1 h. For comparison, the resulting mixture was also dispersed in 1M acid citric and 1M Na2SO4 solutions. After complete dissolution, the resulting solution was washed using a centrifuge and the undissolved particles were separated from the solution. The solution was subjected to ICP analysis. Results of ICP and also the percentage of element recovered are listed in Tables 2 and 3, respectively. As can be seen from Table 2, water exhibited the best behavior in terms of recovery of Li with dissolving the highest amount of Li and least amount of other impurities such as Al, Ni and Co. According to the efficiency of recovered elements, the selectivity of the separation for different elements is presented below: For Li recovery: cold waterNsodium sulfateNcitric acid. For Co recovery: citric acidNsodium sulfateNwater. As can be seen in Table 1, citric acid showed lower selectivity due to its molecular structure with three acidic groups behaving as strong chelating agents to coordinate with available elements including Co, Ni, and Mn. Although the efficiency of Li recovery by different solutions is quite similar, cold water was able to selectively extract Li. The undissolved particles were then dried in an oven at 100 °C overnight and mixed with carbon sourced from anodic part of LIBs prior to the second carbothermal reaction at 800 °C for 1 h. After heat treatment, the resulting product was subjected to XRD and SEM-EDS analysis. Strong peaks assigned with metallic cobalt are detected from XRD spectrum shown in Fig. 6a. SEM image, EDX elemental mapping and EDX quantitative analysis of the sample are displayed in Fig. 6b. EDX elemental and quantitative analysis (Fig. 6b) also confirm cobalt oxide was reduced to the metallic cobalt. From the ICP results, the recovery of cobalt was calculated which very high (N99%) indicating that from 1 kg LIBs, around 400 g Co can
Table 3 Element recovered using different solutions.
Element
Suspension technique
Reagent
Al
Co
Li
Mn
Ni
Cold water (mg.l−1) Citric acid (mg.l−1) Sodium sulfate (mg.l−1)
1.10 113 1.44
0.18 1925 0.28
834 826 768
0.08 368 0.09
0.00 30.1 0.00
Cold water Citric acid (1M) Sodium sulphate (1M)
Elements recovered wt% Li
Co
Mn
Ni
Al
36.0 38.3 38.2
0.002 16.75 0.005
0.03 67.05 0.03
0.01 7.82 0.01
0.16 4.10 0.27
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
5
Fig. 6. a) XRD spectrum and b) SEM image EDS analysis of the recovered Co.
be recovered. The recovery of Li was 36% which is relatively high considering that water was used as solvent for the recovery. The techniques suggested in this work for the recycling of LIBs resulted in successful recovery of Li and Co. The recycling of LIBs via thermal processing is challenging owing to the presence of Li which can liberate from the system in form of gas. However, in this work we have established that by controlling temperature, Li can be safely isolated and trapped in solid form and separated from Co. Using cold water as solution, Li was selectively leached out of lithium carbonate which resulted in successful recovery of Li. 4. Conclusions Li and Co were recovered from LIBs via a novel approach of thermal isolation-suspension. The LIBs sourced from e-waste were discharged, dismantled and the separated cathodic part was pulverized into a fine powder using ring mill. The Al content of the resulting powder was leached out using 2 M NaOH. The Al free cathodic sample (C1) was then mixed with activated carbon. Thermal behavior of the mixture was examined at temperatures of 600 °C, 700 °C and 800 °C using TGA and horizontal tube furnace. From TGA and XRD analysis of the sample after reduction, it was found that at 700 °C Li was successfully isolated in form of solid lithium carbonate and separated from cobalt oxide while cobalt oxide was partially reduced to the metallic cobalt. At 600 °C, no decomposition in the structure of the initial sample was observed. At 800 °C, Li escaped from the sample in form of gas and cobalt oxide was completely reduced to the metallic cobalt. The optimum temperature of 700 °C was selected for thermal isolation of Li. After thermal isolation, the resulting sample (C2) was subjected to a stage of suspension at 0 °C using water as solvent. After filtration, the solution was sent to ICP analysis to measure the content of the extracted Li with 36% recovery, which is relatively high considering that water was used as solvent. The undissolved particles were mixed with carbon and heat treated at 700 °C for final reduction of cobalt oxide to the metallic cobalt. The novel technique of thermal isolation-suspension reported in this work resulted in successful recovery of Co and Li from LIBS. References [1] http://www.batteryrecycling.org.au/recycling/batteries-and-the-environment //.
[2] http://www.environment.gov.au/system/files/resources/2e8c76c3-0688-47efa425-5c89dffc9e04/files/biosolids-snapshot.pdf. [3] http://www.mining.com/lithium-demand-battery-makers-almost-double-2027. [4] http://www.infomine.com/investment/metal-prices/cobalt/5-year/. [5] https://www.smh.com.au/business/companies/electric-cars-open-new-doors-forclive-palmer-as-nickel-prices-boom-20180611-p4zkts.html. [6] D.C.R. Espinosa, A.M. Bernardes, Tenorio JAS. 135 (2004) 311–319. [7] P.W. Zhang, T. Yokoyama, O. Itabashi, Y. Wakui, T.M. Suzuki, K. Inoue, J. Power Sources 77 (1999) 116–122. [8] P.W. Zhang, T. Yokoyama, O. Itabashi, Y. Wakui, T.M. Suzuki, K. Inoue, Hydrometallurgy 50 (1998) 61–75. [9] A. Poscher, S. Luidold, H. Antrekowitsch, Seltener Erden (2011) 419–426. [10] P. Meshram, H. Somani, B.D. Pandey, T. Mankhand, H. Deveci, Abhilash, J. Clean. Prod. 157 (2017) 322–332. [11] A. Fernandes, J.C. Afonso, A.J.B. Dutra, Hydrometallurgy 133 (2013) 37–43. [12] Y. Yao, N.F. Farac, G. Azimi, ACS Sustainable Chem, Eng. 6 (1) (2018) 1417–1426. [13] Z. Sun, H. Cao, Y. Xiao, J. Sietsma, W. Jin, H. Agterhuis, Y. Yang, Toward sustainability for recovery of critical metals from electronic waste: the hydrochemistry processes, ACS Sustain. Chem. Eng. 5 (2017) 21–40. [14] Y. Yang, S.L. Song, F. Jiang, J.H. Zhou, W. Sun, Short process for regenerating Mn-rich cathode material with high voltage from mixed-type spent cathode materials via a facile approach, J. Clean. Prod. 186 (2018) 123–130. [15] Y. Weng, S. Xu, G. Huang, C. Jiang, Synthesis and performance of Li[(Ni1/3Co1/ 3Mn1/3)(1-x)Mgx]O2 prepared from spent lithium ion batteries, J. Hazard. Mater. 246–247 (2013) 163–172. [16] M.K. Jha, A. Kumari, A.K. Jha, V. Kumar, J. Hait, B.D. Pandey, Recovery of lithium and cobalt from waste lithium ion batteries of mobile phone, Waste Manag. 33 (2013) 1890–1897. [17] C.K. Lee, K.I. Rhee, Preparation of LiCoO2 from spent lithiumion batteries, J. Power Sources 109 (2002) 17–21. [18] J. Li, P. Shi, Z. Wang, Y. Chen, C.C. Chang, A combined recovery process of metals in spent lithium-ion batteries, Chemosphere 77 (2009) 1132–1136. [19] L. Li, W. Qu, X. Zhang, J. Lu, R. Chen, F. Wu, K. Amine, Succinic acid-based leaching system: a sustainable process for recovery of valuable metals from spent Li-ion batteries, J. Power Sources 282 (2015) 544–551. [20] X. Zeng, J. Li, B. Shen, Novel approach to recover cobalt and lithium from spent lithium-ion battery using oxalic acid, J. Hazard. Mater. 295 (2015) 112–118. [21] L.P. He, S.Y. Sun, X.F. Song, J.G. Yu, Leaching process for recovering valuable metals from the LiNi1/3Co1/3Mn1/3O2 cathode of lithium-ion batteries, Waste Manag. 64 (2017) 171–181. [22] M. Joulie, R. Laucournet, E. Billy, Hydrometallurgical process ́ for the recovery of high value metals from spent lithium nickel cobalt aluminum oxide based lithium-ion batteries, J. Power Sources 247 (2014) 551–555. [23] P. Meshram, B.D. Pandey, T.R. Mankhand, Hydrometallurgical processing of spent lithium ion batteries (LIBs) in the presence of a reducing agent with emphasis on kinetics of leaching, Chem. Eng. J. 281 (2015) 418–427. [24] Y. Yue, S. Wei, B. Yongjie, Zh. Chenyang, S. Shaole, H. Yuehua, Recovering valuable metals from spent lithium ion battery via combination of reduction thermal treatment and facile acid leaching, ACS Sustain. Chem. Eng. 6 (2018) 10445–10453.
Contents lists available at ScienceDirect
Sustainable Materials and Technologies journal homepage: www.elsevier.com/locate/susmat
Recovery of lithium and cobalt from waste lithium-ion batteries through a selective isolation-suspension approach Samane Maroufi ⁎, Mohammad Assefi, Rasoul Khayyam Nekouei, Veena Sahajwalla Centre for Sustainable Materials Research and Technology (SMaRT), School of Materials Science and Engineering, University of New South Wales, Sydney 2052, Australia
a r t i c l e
i n f o
Article history: Received 18 June 2019 Received in revised form 16 August 2019 Accepted 14 November 2019
Keywords: Lithium-ion batteries Recycling Lithium Cobalt Thermal isolation
a b s t r a c t This paper describes a selective thermal isolation-suspension process for the recovery of Li and Co from spent Lithium-Ion Batteries (LIBs). The cathodic part of LIBs, which are mainly composed of Li, Al and Co, sourced from electronic waste (e-waste) was first subjected to a suspension stage for removing Al. XRD analysis of the cathodic sample free of Al (C1) revealed that C1 was in the form of LiCoO2. Thermal behavior of C1 was also examined against time and temperature using Thermogravimetric Analysis (TGA). Thermal isolation of C1 was carried out via reduction in argon atmosphere using activated carbon at temperature in the range of 600 °C to 800 °C for 30 min. At 600 °C, no dissociation of the initial compound of LiCoO2 was observed. At 800 °C Li totally liberated from the sample in form of gas and cobalt oxide was reduced to the metallic cobalt. However, at 700 °C, Li was thermally isolated in form of solid lithium carbonate and separated from Co. Temperature of 700 °C was selected as the optimum temperature for thermal isolation of Li which resulted in dissociation of LiCoO2 into Co, CoO and Li2CO3. After thermal isolation at 700 °C, the resulting mixture (C2) was dispersed into distilled water, placed in a cold-water bath with temperature of 0 °C and was allowed to gradually dissolve in water for 1 h. After filtration and washing using a centrifuge, the solution was subjected to ICP analysis and the undissolved particles were dried in an oven overnight prior to further reduction at 700 °C for full reduction of cobalt oxide to metallic cobalt. The simple and environmentally friendly approach proposed in this work for the recovery of Li and Co from spent LIBs can potentially help in addressing the problems associated with waste LIBs and depletion of natural resources. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Batteries are a fast-growing and problematic waste stream in Australia, caused by our increasing reliance on electronic devices and our low recycling rates. In Australia, some 345 million handheld batteries are consumed annually. Only 6% of these by weight and 4% by count are currently recycled with the majority disposed of in landfills (around 183 million) or informally stockpiled [1]. This poses serious environmental and health risks as batteries can explode or degrade and are highly toxic. Additionally, 15% of Australia's large landfills and 65% of medium-sized landfills are unlined, where metals can leak and contaminate soil and groundwater [2]. The end-of-life batteries which cannot be reused in other energy supply-demands should be recycled so their constituent parts can be reformed for reuse as high-value materials. The complex mix of metals, non-metals and plastics in a typical battery means processing currently is challenging and costly, and this results in low battery recycling rates with the resultant recovered materials seen as being of low value. ⁎ Corresponding author. E-mail address: s.maroufi@unsw.edu.au (S. Maroufi).
https://doi.org/10.1016/j.susmat.2019.e00139 2214-9937/© 2019 Elsevier B.V. All rights reserved.
At the same time, batteries contain non-renewable resources in high demand such as lithium (Li), cobalt (Co) and nickel (Ni). Demand for these metals is being driven by growth in the development and sales of electric vehicles, consumer electronics and domestic energy storage devices [3]. Recently, the five-year historical average price of Co tripled and is now double that average, making it commercially attractive to find ways to recover and reuse Co [4,5]. Recovering resources from batteries will reduce pressure on the world's finite virgin resources. The high price and finite nature of the minerals containing such metals make recovery very attractive in terms of environmental, economic and social benefits. Lithium-Ion Batteries (LIBs) are a popular type of rechargeable batteries which are widely used in portable electronics. Such batteries are composed of several electrochemical cells in which lithium ions move between the anode and the cathode electrodes. LIBs are mainly composed of cathode, anode, electrolyte, and separator, which all are covered by a metal case and plastic cover. The cathode is commonly made of a lithium metal oxides such as lithium cobalt oxide (LiCoO2 or LCO), lithium nickel oxide (LiNiO2), lithium vanadium oxide (LiV2O3), lithium manganese oxides (LiMn2O4 or LMO), lithium iron phosphate
2
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
Fig. 2. XRD spectrum of the cathodic materials after removing Al (C1).
Fig. 1. Flow chart of the experimental procedure for the recycling of Li and Co from spent LIBs.
(LiFePO4 or LFP) or a complex compound like (LiNi0.33Mn0.33Co0.33O2 or NMC), and the anode is graphite [6]. Several pyrometallurgical and hydrometallurgical processes have been suggested by researchers across the globe for the recycling of different batteries [6–12]. In hydrometallurgical processes, multiple steps of leaching and separation are involved in the separation of different elements. Most of these reported recycling techniques are based on recovery of only a particular element from batteries, not all or most of the constituent parts, and these reported techniques [6] are in most cases very complex and not commercially viable. In general, hydrometallurgical process includes the steps of dismantling, crushing, leaching, purification, separation and product preparation among which leaching has been the center of attention [13–15]. Several researchers have worked on recovery of metals from cathode part of the LIBs such as LiCoO2 [16–20], NixCoyMn1-x-yO2 [15–21], Li NixCoyMn1-x-yO2 [22,23]. It is worth noting that some of the transition metal ions (i.e., Co3+, Mn4+) are present at high valence (+3/4) in aqueous solution and therefore it is important to use a reducing agent to reduce the valence to a low valence state (2+). Many works have reported the use of Na2SO3, H2O2 [16,17] and ascorbic acid as reducing agent in their leaching process. In the pyrometallurgical technique, batteries are pyrolyzed and the metallic components are reduced and smelted in large furnaces at 1500 °C. In research reported by [12], LIB cathode was decomposed to lithium carbonate and cobalt oxide via heat treatment at 600 °C using graphite for 2 h. Thermal processing reduced the valence value of Co from 3+ to 2+, which resulted in facile leaching in 2.25 M H2SO4.
Table 1 ICP results of the cathodic part of LIB. Elements
Li
Co
Mn
Ni
Al
wt%
6.47
40.61
1.57
1.61
7.81
After leaching in H2SO4, Co and Li in the leaching liquor were further separated with 35% PC88 at the ratio of aqueous to organic (A:O) equalling 0.5, 25 °C and pH = 5.5. This study aims to address the challenges of achieving environmentally friendly recovery of Li and Co from LIBs via a novel two-step thermal isolation-suspension approach, using activated carbon as reducing agent and water as solvent. The thermal isolation step was performed via simple carbothermal reduction at temperatures in the range between 600 °C-800 °C in argon (Ar) using activated carbon as reducing agent. In the first process, LIB cathode powder was mixed with activated carbon and reduced in Ar which resulted in the formation of Co, cobalt oxide and lithium carbonate. This step was then followed by dissolution in cold water which led to the successful dissolution of Li2CO3 in water and residing cobalt oxide. The residual cobalt oxide was later reduced to metallic cobalt at 700 °C.The flow chart of the experimental procedure used in this work is shown in Fig. 1. 2. Characterization of materials and experimental procedure LIBs sourced from the Reverse E-waste Company, Sydney, Australia were discharged and then dismantled manually. The plastic cases were separated and the cell was cut longitudinally and the active components were separated from the plastic pieces. The cathode part which composed of aluminum (Al) foils coated by dioxide in double sides were separated. The separated foils were then pulverized into a fine powder using 30 s ring milling. 5 g of the resulting fine powder was dispersed into 50 ml of 2 M NaOH, then placed on a hot plate at temperature of 60 °C for 2 h. The powder was leached thoroughly and the resulting mixture was subsequently filtered to separate Al. The filtered powder was then dried in an oven overnight and then subjected to analysis using Inductively Coupled Plasma (ICP) technique. The analyzed composition of the separated oxide phase is listed in Table 1. The X-ray diffraction spectrum of the cathodic materials after removing Al (C1) is displayed in Fig. 2. From XRD pattern, strong characteristic peaks belong to lithium cobalt oxide (LiCoO2) can be observed while the peaks assigned to Al is not detectable, which is due to the detection limit of XRD. The thermal degradation behavior of the C1 sample was studied using Thermogravimetric Analysis (TGA); where the sample was heated from room temperature to 1000 °C at a heating rate of 20 °C.min−1 under nitrogen (N2) purge of 20 ml.min−1. TGA results are shown in. The initial observation from the mass loss versus temperature curve, Fig. 3a, indicates there is no change in the mass of the C1 up to 730 °C while at around 740 °C, a sharp decrease in the weight occurred which can be assigned to reduction of LiCoO2 to metallic cobalt, dissociation of Li from LiCoO2 and removal of oxygen, carbon and Li from the sample. The thermal-induced weight loss increases with temperature and around 65% of the sample remains at 1000 °C. The DTG curve provides visual evidence of the degradation process. Thermal degradation
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
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Fig. 3. Thermogravimetric analysis of C1 at a heating rate of 20 °C.min−1 under nitrogen (N2) purge of 20 ml.min−1 a) weight loss and DTG curves versus temperature b) weight loss versus time.
of C1 sample against times was also examined while temperature was kept 600 °C, 700 °C and 800 °C and the results are displayed in Fig. 3b. As can be seen from Fig. 3b, the weight loss due to the heat treatment at 600 °C is negligible which indicates, LiCoO2 did not react with activated carbon and no decomposition took place at this temperature. With increasing temperature to 700 °C, at initial stages no trace of LiCoO2 decomposition can be found in weight loss versus time curve. With extending reaction time up to 40 min, the sample started to decompose and the mass of the sample continuously decreased over time. Although no degradation was detected when the sample was gradually heat treated from room temperature to 700 °C(Fig. 3a), however the result in Fig. 3b can confirm that thermal degradation behavior of the sample is affected by time. At 800 °C, a relatively sharp thermal decomposition can be conserved after 38 min of heat treatment.
X-ray diffraction spectrum of the samples after heat treatment at 600 °C, 700 °C and 800 °C are shown in Fig. 4a, b and c, respectively. XRD pattern of the sample after heat treatment at 600 °C (Fig. 4a) shows strong peaks assigning to LiCoO2 which indicate that LiCoO2 in the initial sample did not react with carbon and dissociation of Li from LiCoO2 did not occur at this temperature which agrees well with TGA result. With increasing temperature to 700 °C, the characteristic peaks of LiCoO2 completely disappeared and new peaks attributing to the phases of Co, cobalt oxide and lithium carbonate appeared. This shows that at 700 °C, LiCoO2 dissociated and carbothermal reduction of oxide phase occurred which resulted in the formation of the metallic cobalt. It has been proved that dissociation of LiCoO2 can occur according to the following equations [24]: Reaction. # Reaction
3. Results and discussions 3.1. Thermal isolation at low temperature After filtration, the C1 sample was mixed with activated carbon (Charcoal Norit supplied by Sigma) in a ratio of 5 to 1 (C1: AC). The resulting mixture was then placed in an alumina crucible inserted in a pre-heated tubular furnace (100 cm length × 5 cm diameter) at the target temperature (i.e., 600 °C, 700 °C, and 800 °C) under Ar purge (1 L. min−1) for a given period of time. The furnace was coupled with an Infrared gas analyzer (Advanced Optima AO2020, ABB Measurement and Analytics, Australia) for continuous measurement of non-condensable Syngas, e.g., CO, CO2 and CH4. The offgas was monitored to give an insight into the formation of lithium carbonate taking place at those temperatures and indicating the completion of the reaction. After heat treatment, the sample was kept in the cold zone of the furnace in Ar for 10 min. The resulting phases of the samples were further examined by XRD.
(1) (2) (3) (4) (5) (6)
C + 12LiCoO2→6Li2O + 4Co3O4 + CO2 C + 4LiCoO2→2Li2O + 4CoO + CO2 2Co3O4 + C→6CoO + CO2 Li2O + CO2→Li2CO3 2CoO + C→2Co + CO2 CO2 + C↔2CO
ΔG (kJ.mol−1) 600 °C
700 °C
800 °C
62.3
356.7
349.5
−4.1 −187.3 −175.0 34.5 134.9
−17.9 −205.2 −178.2 37.4 133.2
−31.2 −221.6 −185.6 40.3 131.5
In reaction with solid carbon at 700 °C, LiCoO2 first decomposes to Li2O and cobalt oxide as shown in reactions (1) and (2). The produced Li2O in return reacts with CO2 which results in the formation of Li2CO3 (reaction (4)). XRD pattern of the sample after heat treatment at 700 °C shows that cobalt oxide was partially reduced to the metallic cobalt (reaction (5)) and strong peaks corresponding to metallic cobalt is detected. With further increasing temperature to 800 °C, all peaks belonging to cobalt oxide and lithium cobalt oxide disappeared. This indicates that lithium carbonate becomes unstable when temperature rises
Fig. 4. XRD spectra of C1‑carbon mixture after heat treatment in Ar atmosphere at a) 600 °C, b) 700 °C and c) 800 °C for 60 min.
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S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
Fig. 5. Concentration of CO/CO2 gases generated during heat treatment in Ar atmosphere at a) 600 °C, b) 700 °C and c) 800 °C for 60 min.
to 800 °C, and liberate from the system in the form of gas. The remaining cobalt oxides were reduced to the metallic cobalt and no trace of cobalt oxide is detected from XRD pattern. The concentrations of CO, CO2 gases evolved from the system was monitored using the IR-gas analyzer. Fig. 5 shows the concentration of gases generated during the heat treatment at temperatures in the range of 600 to 800 °C. At 600 °C, the concentration of the evolved CO and CO2 was found to be limited which can be justified by the result of XRD. XRD pattern of the sample after heat treatment at 600 °C reveals that no dissociation took place at this temperature and LiCoO2 remained unaffected. With increasing temperature to 700 °C, concentration of CO2 raised quickly and reached to its maximum value within 10 min. This can be attributed to the rapid decomposition of LiCoO2 to LiO and cobalt oxide based on reaction (1)–(3). The evolved CO2 in return reacted with Li2O to form Li2CO3 which resulted in dropping the concentration of CO2. With further rising temperature to 800 °C, at initial stages of the reaction, concentration of CO2 quickly soared in a few minutes, which can be assigned to the quick decomposition of LiCoO2 to LiO2 and cobalt oxide (reactions (1)–(3)). With extending the reaction time, the concentration of CO2 dropped which is most probably due to the reaction between CO2 and LiO2 and the formation of Li2CO3. This stage is followed with a second increase in the concentration of CO2 while concentration of CO started to rise. The sharp increase in the concentration of CO in the off-gases can be clearly observed, implying that carbothermal reduction of cobalt oxide to metallic cobalt occurred. As can be seen from reaction (5), reaction of cobalt oxide with solid carbon takes place through Boudouard reaction (6), which results in the formation of CO. The second peak in the concentration of CO2 can be assigned to the Reduction of cobalt oxide to metallic cobalt, as shown in reaction (5). 3.2. Suspension using cold water Carbothermal reaction at 700 °C resulted in successful dissociation of LiCoO2 into Li2CO3, CoO and metallic cobalt. For the final separation of Li and Co, a facile technique of dissolution in cold water was applied. Solubility of lithium carbonate in water at ambient temperature is not very high owing to the fact that the electrostatic attraction between the very small lithium cation and the carbonate anion overpowers the attraction Table 2 ICP results of the sample after suspension in different solvents.
between these ions and the water molecules. However, solubility can increase with decreasing temperature to zero. The decrease in solubility of lithium carbonate in water with increasing temperature points to an entropy phenomenon. In other words, the lithium cation and the carbonate anion decrease overall entropy (i.e., by imposing order upon solvation) in solution. After carbothermal reduction, the resulting mixture was dispersed into distilled water, placed in a cold-water bath with temperature of 0 °C and was allowed to gradually dissolve in water for 1 h. For comparison, the resulting mixture was also dispersed in 1M acid citric and 1M Na2SO4 solutions. After complete dissolution, the resulting solution was washed using a centrifuge and the undissolved particles were separated from the solution. The solution was subjected to ICP analysis. Results of ICP and also the percentage of element recovered are listed in Tables 2 and 3, respectively. As can be seen from Table 2, water exhibited the best behavior in terms of recovery of Li with dissolving the highest amount of Li and least amount of other impurities such as Al, Ni and Co. According to the efficiency of recovered elements, the selectivity of the separation for different elements is presented below: For Li recovery: cold waterNsodium sulfateNcitric acid. For Co recovery: citric acidNsodium sulfateNwater. As can be seen in Table 1, citric acid showed lower selectivity due to its molecular structure with three acidic groups behaving as strong chelating agents to coordinate with available elements including Co, Ni, and Mn. Although the efficiency of Li recovery by different solutions is quite similar, cold water was able to selectively extract Li. The undissolved particles were then dried in an oven at 100 °C overnight and mixed with carbon sourced from anodic part of LIBs prior to the second carbothermal reaction at 800 °C for 1 h. After heat treatment, the resulting product was subjected to XRD and SEM-EDS analysis. Strong peaks assigned with metallic cobalt are detected from XRD spectrum shown in Fig. 6a. SEM image, EDX elemental mapping and EDX quantitative analysis of the sample are displayed in Fig. 6b. EDX elemental and quantitative analysis (Fig. 6b) also confirm cobalt oxide was reduced to the metallic cobalt. From the ICP results, the recovery of cobalt was calculated which very high (N99%) indicating that from 1 kg LIBs, around 400 g Co can
Table 3 Element recovered using different solutions.
Element
Suspension technique
Reagent
Al
Co
Li
Mn
Ni
Cold water (mg.l−1) Citric acid (mg.l−1) Sodium sulfate (mg.l−1)
1.10 113 1.44
0.18 1925 0.28
834 826 768
0.08 368 0.09
0.00 30.1 0.00
Cold water Citric acid (1M) Sodium sulphate (1M)
Elements recovered wt% Li
Co
Mn
Ni
Al
36.0 38.3 38.2
0.002 16.75 0.005
0.03 67.05 0.03
0.01 7.82 0.01
0.16 4.10 0.27
S. Maroufi et al. / Sustainable Materials and Technologies 23 (2020) e00139
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Fig. 6. a) XRD spectrum and b) SEM image EDS analysis of the recovered Co.
be recovered. The recovery of Li was 36% which is relatively high considering that water was used as solvent for the recovery. The techniques suggested in this work for the recycling of LIBs resulted in successful recovery of Li and Co. The recycling of LIBs via thermal processing is challenging owing to the presence of Li which can liberate from the system in form of gas. However, in this work we have established that by controlling temperature, Li can be safely isolated and trapped in solid form and separated from Co. Using cold water as solution, Li was selectively leached out of lithium carbonate which resulted in successful recovery of Li. 4. Conclusions Li and Co were recovered from LIBs via a novel approach of thermal isolation-suspension. The LIBs sourced from e-waste were discharged, dismantled and the separated cathodic part was pulverized into a fine powder using ring mill. The Al content of the resulting powder was leached out using 2 M NaOH. The Al free cathodic sample (C1) was then mixed with activated carbon. Thermal behavior of the mixture was examined at temperatures of 600 °C, 700 °C and 800 °C using TGA and horizontal tube furnace. From TGA and XRD analysis of the sample after reduction, it was found that at 700 °C Li was successfully isolated in form of solid lithium carbonate and separated from cobalt oxide while cobalt oxide was partially reduced to the metallic cobalt. At 600 °C, no decomposition in the structure of the initial sample was observed. At 800 °C, Li escaped from the sample in form of gas and cobalt oxide was completely reduced to the metallic cobalt. The optimum temperature of 700 °C was selected for thermal isolation of Li. After thermal isolation, the resulting sample (C2) was subjected to a stage of suspension at 0 °C using water as solvent. After filtration, the solution was sent to ICP analysis to measure the content of the extracted Li with 36% recovery, which is relatively high considering that water was used as solvent. The undissolved particles were mixed with carbon and heat treated at 700 °C for final reduction of cobalt oxide to the metallic cobalt. The novel technique of thermal isolation-suspension reported in this work resulted in successful recovery of Co and Li from LIBS. References [1] http://www.batteryrecycling.org.au/recycling/batteries-and-the-environment //.
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