Environmentally Friendly Recycling of Lithium Ion Batteries
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Recycling lithium ion batteries (LIBs) and using their recovered materials to make new ones has many economic, social, and environmental benefits. The greatest benefits come from recycling metals from cathode active materials (CAMs), for example Li, Ni, Co, and Mn from NCM111 (a common electric vehicle CAM). Hydrometallurgical recycling processes, in which CAMs are leached and metals are extracted from the pregnant leach solution (PLS), are favoured because they can recover all metals. Due to the hazards of leaching with strong acids, organic acids are becoming preferred lixiviants; however, they are expensive. In this work, two green chemistry hydrometallurgy processes were developed to recycle CAMs from LIBs. Both processes regenerate organic acid lixiviant, have high Li, Ni, Co, and Mn recoveries, and produce sodium-free Li2CO3. In the first process, Donnan Dialysis is used to extract Li, then Ni, Co, and Mn, as well as to reprotonate organic acid in PLS. Donnan Dialysis combined with bicarbonation and decarbonation is used to produce Li2CO3 from the Li extract. Heating is not required in the process. Mass balances, charge balances, and mass flux equations were developed. Experiments were performed to obtain mass transfer coefficients. The process was simulated and the results were: recoveries of 94.1% for Li and 99.4% for Ni, Co, and Mn and 98.9% of organic acid reprotonated. In the second process, formic acid was used to leach NCM111 while simultaneously precipitating Ni, Co, and Mn formate salts. These salts were reacted with sulphuric acid to yield mixed Ni, Co, and Mn sulphate salts and formic acid, which was evaporated. The PLS was saturated with Li2CO3, which precipitated residual Ni, Co, and Mn, and was filtered then dewatered. The LiCOOH salts obtained were thermally decomposed in air to 99.97 wt% Li2CO3. Recoveries of Li, Ni, Co, and Mn were 100%. The process produces neither solid nor liquid waste. By condensing vapours from dewatering and evaporation steps, 66% of the water and 57% of the formic acid needed for leaching can be recovered for reuse. Mixed Ni, Co, and Mn sulphate salts and Li2CO3 can be used to make new LIBs.