Toward the efficient direct regeneration of spent cathode materials through the effect of residual sodium ions analysis.

Recycling spent lithium-ion batteries is an important means for promoting sustainability within the energy industry. In this study, the effects of residual sodium on the regeneration process and the performance of spent LiNi0.5Co0.2Mn0.3O2 were explored. An appropriate amount of residual sodium was found to improve the properties of the regenerated material, with the best cycle performance and rate performance at a residual sodium of 3 mol %. The first-cycle and 100-cycle discharge capacities were 136.4 mA h g-1 and 120 mA h g-1, respectively, with a capacity retention rate of 87.98% after 100 cycles at a rate of 1 C. The electrochemical performance of the regenerated cathode materials was improved because sodium occupied the lithium sites in the crystal structure, providing a channel for lithium deintercalation. These results indicate that the residual sodium ions should be monitored in appropriate quantities to improve the efficiency of recycling spent lithium-ion batteries.