Urea solvothermal regeneration of spent LiNi0.5Co0.2Mn0.3O2: Performance and environmental benefits

With the large-scale application of power batteries, a large number of spent lithium-ion batteries (LIBs) will be formed in recent years. The improper disposal of spent LIBs will pose significant environmental pollution. LiNi0.5Co0.2Mn0.3O2 (NCM), as a typical type of LIBs cathodes material, are widely used and can be highly recycled. However, the existing hydrometallurgical and pyrometallurgical recycling processes consume large amounts of energy and introduce serious secondary pollution. This work presents a simple straightforward direct regeneration process that uses urea solvothermal treatment followed by calcination to obtain urea-regenerated spent NCM (UR-S-NCM). Surprisingly, the specific capacity of the regenerated NCM of UR-S-NCM recovers completely and reaches 166 mAh/g, higher than that of fresh NCM (F-NCM) at 156 mAh/g. After 100 charge/ discharge cycles, the specific capacity of UR-S-NCM is 37 % higher than that of F-NCM at the same condition. Additionally, the CO2 emissions per kilogram of the regenerated UR-S-NCM are only 1.79 kg, about 31 % of pyrometallurgy and 48 % of hydrometallurgy, respectively. The surface smoothness, grain boundaries and layered structure of UR-S-NCM are recovered from S-NCM to the same situation of F-NCM. Smooth surface facilitates Li+ migration into and out of UR-S-NCM, grain boundaries reduction diminishes electrolyte corrosion, and the layered structure accommodates more Li+ compared to the spinel structure of S-NCM. This work provides an eco-friendly direct regeneration process and offers a new insight for LIBs regeneration.