Economical recycling process for spent lithium-ion batteries and macro- and micro-scale mechanistic study

An economical effective method is developed for recycling spent LiNi_1/3Co_1/3Mn_1/3O₂ cathodes, where more than 98% Li, Co, Ni and Mn can be leached out with different organic acids, and resynthesized to LiNi_1/3Co_1/3Mn_1/3O₂. The leaching mechanism is investigated at macro- and micro-scales. The particles undergo a loosening-breaking-shrinking change for two acids, while the FTIR and UV-vis spectra indicate different coordination reactions. The performance of LiNi_1/3Co_1/3Mn_1/3O₂ resynthesized from the leachate of the acetic acid leaching (NCM-Ac) and maleic acid leaching (NCM-Ma) are compared. The first discharge capacity of NCM-Ma and NCM-Ac at 0.2C are 151.6 and 115.0 mA h g⁻¹, respectively. The much better performance of NCM-Ma than NCM-Ac results from the different coordination of the two acids in the sol-gel process, where the maleic acid can esterify to establish a stable network to chelate metal ions, while the weak chelation of acetic acid leads to the formation of impurities. The economics analysis including the cost of leaching acid and energy consumption shows that the price of organic acids and reducing agents, short leaching time, low temperature and high-valued products are the effective way to increase recycling and environmental benefits, which shows advantages in terms of resources cost and added value.