http://pubs.acs.org/journal/aelccp
Recycling Strategies for Spent Li-Ion Battery Mixed Cathodes (>1000 °C) recovers only the lesser proportion of metal alloys, such as Co, Fe, Ni, and Cu. The remaining slag that contains unrecovered Li is being sold as a road base to the construction industries. However, a small increase in the recovery of Li from that slag is not a strong economic incentive to the recycling unit. Most of the constituent materials (60−70%) of spent LIBs are volatilized or added to the slag, indicating another critical drawback of this process. In contrast, a hydrometallurgy process has the great benefits of low energy consumption, low concentration of chemical reagents, minimum secondary pollution, and easy separation of metals, making it an excellent choice for efficient recycling.1,6 The hindrances of low recovery efficiency; high intake of chemical reagents; and intricate recycling steps in the methods of chemical precipitation, ionexchange, or solvent extraction are impeding the large-scale metal recovery process in the industry. Additionally, the synthesis of cathode material using separated metals from the complex system (i.e., the mixture of cathode materials such as NMC, LCO, LMO, and LFP) is not a beneficial route in the real waste battery repository. Instead of employing a problematical separation process, cathode material has to be recovered efficiently in a facile approach with new methodologies that have shorter routes and are more economical and environmentally friendly than the prevailing industrial recycling process. A recent method, known as lixiviation-regeneration/leaching-resynthesis, seems to be a feasible tactic to regenerate the cathode materials directly by sol−gel or solid-state synthesis in an industrial scale process.11 This technique will have a great impact on the complex system because of the upcoming different types of manufactured LIBs. Unlike other conventional methods, the distinct advantages of good purity and high yield of regenerated cathode materials increase the prospect of scaling-up this process in the industry within one step from the lixiviate. Generally, this recycling and regeneration technology is composed of three major steps: (i) dismantling spent LIBs, (ii) organic/inorganic acid leaching to lixiviate the metals, and (iii) restoring cathode active materials (NMC, LCO, LMO, or LFP) via any one of the aforementioned methods (Figure 1). First and foremost, prior to dismantling, the spent LIBs are discharged by consuming saline-saturated solutions like Na2SO4 or NaCl to mitigate the potential risk of short circuiting or LIB blast. After dismantling, the common dissolution method uses organic solvents such as N-methyl2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide to detach the electrode material from current collector, succeeding in the removal of polyvinylidene fluoride
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S
ince the commercialization of lithium-ion batteries (LIBs) in 1991 by Sony Inc., the revolution of commercial electronic appliances has increased tremendously. Lithium-ion chemistry has dominated incalculable applications, ranging from portable electronics to electric vehicles (EVs). Its shape versatility resulted in its indispensable place in this era.1 Current research efforts seek to improve the LIB performance in zero-emission transportation applications as well as their intensive use for grid-storage. Except for commercial appliances, hybrid electric vehicles (HEVs) and EVs will be the next generation, bringing an additional burden to the researchers.2 While there is a rapid increase in demand for LIBs in the market, unpredictable increases of the price of raw materials will become an inevitable issue for future mass production. Global market experts forecast the global LIB market will grow at a compound and annual growth rate (CAGR) of 12% from 2017 to 2024. This growth is mainly attributable to the increasing demand for consumer electronic devices and EVs.3 Accordingly, LIB production could suffer by 2050 because of a global supply shortage of key elements (Li, Co, and Ni) and geographical conditions.4,5 Hence, recycling of spent LIBs is being considered as an optimistic approach to alleviate the unprecedented demand for raw materials for the synthesis of cathode materials, excluding the environmental benefits. The disposal of spent LIBs, with their rich metal resources, is challenging researchers to implement recycling processes effectively and efficiently. A few regions across the globe, like Europe and China, have initiated LIB recycling via stringent regulations. LIBs contain toxic metals that need to be recycled in order to address environmental concerns and avoid depletion of material resources.6 Because only ∼5% of LIBs are recycled today, there is a need to recycle the enormous amount of spent LIBs.7 The LIB recycling market was recently predicted to grow with a CAGR of 30.5% through the time period of 2017−2025. More than 11 million tonnes of spent LIB packs are expected to be discarded between 2017 and 2030.8,9 The worldwide emerging automobile industries and the ongoing technological advancements based on LIBs might increase the number of spent LIBs with new compositions and various configurations substantially in the near future. We are in immediate need of methods to recycle mixed types of spent LIBs in order to recover the most precious materials that are needed to produce cathodes, such as LiNi1/3Co1/3Mn1/3O2 (NMC), LiCoO2 (LCO), LiMn2O4 (LMO), and LiFePO4 (LFP). The recycling process should possess a closed loop technology with core aspects being scalable, eco-friendly, and cost-effective. Most of the current recycling processes are not profitable and could not recover the critical components like Li economically from spent LIBs.10 The existing industrial pyro-metallurgical recycling process (i.e., smelting) that involves a high-temperature sintering © XXXX American Chemical Society
Received: July 14, 2018 Accepted: August 3, 2018
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DOI: 10.1021/acsenergylett.8b01233 ACS Energy Lett. 2018, 3, 2101−2103
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Cite This: ACS Energy Lett. 2018, 3, 2101−2103
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the single cathode components.6 Few such initiatives increase the hope of handling the impending bulk mixed composition of spent LIBs. In another report, Wang and co-workers12 recycled the mixed composition of spent cathode materials including NMC, LCO, LMO, and LFP to obtain the NCM via solid-state synthesis. The regenerated NCM examined by various electrochemical tests has shown admirable performance comparable to the commercial NCM. Furthermore, the estimated analysis indicates that the recycled materials could save $10 440/ton in chemicals without including the energy savings of the resynthesis of NCM. Also, the differential cost ($10 440/ton) between the use of recycled materials and commercial materials in the synthesis of NCM is prompting recyclers to commercialize this technology in the near future for the recycling of spent mixed-type cathode materials. Moreover, there is no assurance in the waste battery stream which metals will be present in high or low content. Occasionally, the battery warehouse may contain only LCO, LMO, or NMC or some other proportion. Recently, Sun and co-workers13 resynthesized 0.2Li2MnO3-0.8Li1/3Co1/3Mn1/3O2 from the mixed composition of LCO, LMO, and NCM materials after realizing that HEVs and EVs will generate a plethora of mixed-type cathode materials with high content of Mn (Figure 2). This Mn-rich cathode material retrieved from the lixiviation-regeneration process also has an outstanding electrochemical performance, eliminating the complex system concerns. In the two aforementioned reports (recycling of mixed-type cathode materials), H2SO4 has been used as a lixiviant to achieve high Li+ concentration at relatively high solid−liquid ratio that cannot be easily achieved with green organic acids. Meanwhile, some effort has been made to repair the cathode material with the goal of avoiding the acid-lixiviation approach. In one such approach, a simple method comprising ball milling, sieving, and heat-treatment was used to fabricate the material needed for LFP cathodes on a small scale (100 kg/ day). The LFP material was further subjected to the heat treatment at 650 °C under an Ar/H2 atmosphere to bring forth the high discharge capacity of the cathode material.14 Another recent study tried a green approach with facile separation and heat treatment processes for cathode material
Figure 1. Recycling and regeneration procedure for large-scale mixed-type cathode materials.
(PVdF) binder. The carbon that is present needs to be removed at a higher-temperature calcination process (usually 600−700 °C), which leads to the emission of off-gases that can be purified with special equipment. In some cases, Al foilbearing cathode material is treated in a lower concentration of alkaline solution like NaOH for separation, and then the PVdF impurities and carbon are eliminated through a calcination process.11 Furthermore, the dried cathode active material is subjected to the organic/inorganic acid-lixiviation process with the aid of chemical agents, for example H2O2, under adjusted experimental conditions. To get an exact ratio, the unbalanced molar lixiviate containing metal ions is altered with the requisite commercial metal salts solution in the sol−gel process.11 The solid-state synthesis12 is simply blending the heat-treated hydroxide/carbonate precursor with the recovered/commercial Li salt in the desired molar ratio. The resultant powder is sintered at a higher temperature to revamp the crystal structure of the cathode material (NMC, LCO, LMO, or LFP) easily. This lixiviation-regeneration approach mainly averts the loss of valuable materials, shortening the recycling trajectory and minimizing the labor cost from their respective steps. Recently, many researchers have focused on this approach, but only on the single cathode component as the item of concern. At present, two China-based industries, Green Eco-manufacture Hi-Tech Co. and Bangpu Ni/Co High-Tech Co., have adopted the lixiviation-regeneration process; even so, they recycle only
Figure 2. Regeneration process of mixed spent cathode materials. Reproduced with permission from ref 13. Copyright 2018 Elsevier. 2102
DOI: 10.1021/acsenergylett.8b01233 ACS Energy Lett. 2018, 3, 2101−2103
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production of lithium-ion batteries. ACS Sustainable Chem. Eng. 2016, 4, 7041−7049. (3) Global Demand for Lithium Batteries are Expected to Grow. https://www.prnewswire.com/news-releases/global-demand-forlithium-batteries-are-expected-to-grow-678280603.html. (4) Bad News for Batteries: Cobalt and Lithium Supplies ‘Critical’ by 2050. https://eandt.theiet.org/content/articles/2018/03/badnews-for-batteries-cobalt-and-lithium-supplies-critical-by-2050/. (5) Global Nickel Demand Could More than Double by 2050 Due to the Rise in Popularity of Electric Vehicles. http://minexforum. com/en/global-nickel-demand-could-more-than-double-by-2050-dueto-the-rise-in-popularity-of-electric-vehicles/. (6) Lv, W.; Wang, Z.; Cao, H.; Sun, Y.; Zhang, Y.; Sun, Z. A critical review and analysis on the recycling of spent lithium-ion batteries. ACS Sustainable Chem. Eng. 2018, 6, 1504−1521. (7) Lithium. http://www.foeeurope.org/sites/default/files/ publications/13_factsheet-lithium-gb.pdf. (8) Lithium-ion Battery Recycling Market By Type (NMC, LFP, LMO, Li-TO, NCA, Li-CO ), By Application (Automotive, Power, Marine, Industrial ), Industry Trends, Estimation & Forecast, 20172025. https://www.esticastresearch.com/market-reports/lithium-ionbattery-recycling-market. (9) The World of Lithium-Ion Batteries and Battery Recycling. https://www.li-cycle.com/blog. (10) Rothermel, S.; Evertz, M.; Kasnatscheew, J.; Qi, X.; Grutzke, M.; Winter, M.; Nowak, S. Graphite recycling from spent lithium-ion batteries. ChemSusChem 2016, 9, 3473−3484. (11) 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 Sustainable Chem. Eng. 2017, 5, 5224−5233. (12) Zou, H.; Gratz, E.; Apelian, D.; Wang, Y. A novel method to recycle mixed cathode materials for lithium ion batteries. Green Chem. 2013, 15, 1183−1191. (13) Yang, Y.; Song, S.; Jiang, F.; Zhou, J.; Sun, W. Short process for regenerating Mn-rich cathode material with high voltage from mixedtype spent cathode materials via a facile approach. J. Cleaner Prod. 2018, 186, 123−130. (14) 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, 2500− 2506. (15) The Rise of Electric Cars Could Leave Us with a Big Battery Waste Problem. https://www.theguardian.com/sustainable-business/ 2017/aug/10/electric-cars-big-battery-waste-problem-lithiumrecycling. (16) With 220mn Users, India is Now World’s Second-Biggest Smartphone Market.https://www.thehindu.com/news/cities/ mumbai/business/with-220mn-users-india-is-now-worldssecondbiggest-smartphone-market/article8186543.ece. (17) 37 Mobile Manufacturing Plants Set Up in India in Last Year: Prasad. https://gadgets.ndtv.com/mobiles/news/37-mobilemanufacturing-plants-set-up-in-india-in-last-year-prasad-1451588.
restoration. In this method, 50 g of NMC scraps were applied separately in three different processes such as direct calcination, NMP dissolution, and NaOH solution treatment to isolate the active material from Al foil. After drying, the obtained materials are calcined at various temperatures to renovate the NCM effectively.2 These regenerating processes have very simple steps and an acid-free approach, exhibit less energy consumption, and are eco-friendly. These kinds of economic technologies should be industrialized soon to process the existing and upcoming colossal supply of mixedtype cathode materials. Lastly, we would like to illustrate the severity of the problem with a few examples. Last year, the British and French governments decided to restrict the sale of petrol and diesel cars by 2040 because of the increasing rise of CO2 emissions. Accordingly, Volvo agreed to sell only HEVs or EVs from next year onward.15 The International Energy Agency determined that the number of electric cars will increase to 140 million by 2030 if countries achieve the targets of the Paris climate agreement, whereas the number surpassed 1 million electric cars in 2015 globally. Consequently, there is a need to recycle 11 million tonnes of spent LIBs during the period of 2017− 2030.15 India is the second-biggest smartphone consumer with 220 million users, followed by the United States. In 2015− 2016, 37 manufacturing companies established production plants for mobile phones in India.16,17 This undeniably creates a great impact on the LIB market and brings the massive waste generation worldwide. The LIB material market currently predominantly depends on the mixed-cathode material, and the increasing application of mixed-type cathode materials in EVs as well as in other commercial appliances is prompting researchers to establish novel economical technology sooner by using shorter and greener routes.
Subramanian Natarajan Vanchiappan Aravindan*
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Department of Chemistry, Indian Institute of Science Education and Research (IISER), Tirupati-517507, India
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Subramanian Natarajan: 0000-0002-1753-1188 Vanchiappan Aravindan: 0000-0003-1357-7717 Notes
Views expressed in this Viewpoint are those of the authors and not necessarily the views of the ACS. The authors declare no competing financial interest.
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ACKNOWLEDGMENTS V.A. acknowledges the financial support from the Science & Engineering Research Board (SERB), a statutory body of the Department of Science & Technology, Govt. of India through Ramanujan Fellowship (SB/S2/RJN-088/2016).
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REFERENCES
(1) Zhang, X.; Bian, Y.; Xu, S.; Fan, E.; Xue, Q.; Guan, Y.; Wu, F.; Li, L.; Chen, R. Innovative application of acid leaching to regenerate Li(Ni1/3Co1/3Mn1/3)O2 cathodes from spent lithium-ion batteries. ACS Sustainable Chem. Eng. 2018, 6, 5959−5968. (2) Zhang, X.; Xue, Q.; Li, L.; Fan, E.; Wu, F.; Chen, R. Sustainable recycling and regeneration of cathode scraps from industrial 2103
DOI: 10.1021/acsenergylett.8b01233 ACS Energy Lett. 2018, 3, 2101−2103
