Single-Crystal Materials Regenerated and Modified by Spent NCM523 as a High-Voltage Stable Cycling Cathode Material

In recent years, the direct regeneration of cathode materials has attracted the attention of a large number of researchers because of its advantages of a simple process and high metal utilization rate. The grain boundary cracking of secondary agglomeration particles will aggravate the degradation of batteries during cycling. In this work, we propose the idea of regenerating spent NCM523 from secondary agglomeration particles into micron single crystals. This approach combines mechanical activation and high-temperature annealing. The regenerated single-crystal materials not only recover the layered structure but also have the same electrochemical reaction kinetics as the single-crystal materials synthesized by the precursors. In addition, a simple and practical solution is proposed, in which LiAlO2 is coated on the surface of the material by hydrolysis and high-temperature annealing. The capacity retention rate of the 1 mol % LiAlO2-coated single-crystal material is 97.49% after 100 cycles of 0.2 C charge/1 C discharge cycling at 3.0–4.5 V. The high Li ionic conductivity of LiAlO2 reduces the charge transfer impedance of single-crystal particles at high voltage and alleviates surface side reactions, achieving cycling stability. This new method provides a feasible scheme for sustainable utilization of cathode materials.