Restoration of Degraded Nickel-Rich Cathode Materials for Long-Life Lithium-Ion Batteries

The sensitive surface of nickel-rich layered oxides often suffers from the erosion of CO₂ and H₂O in air. The results of erosion, including formation of impurities such as Li₂CO₃ and LiOH, degradation of layered structures and disproportionation of trivalent nickel, would cause cation mixing and structural instability. In order to overcome these inherent drawbacks, we present a targeted solvothermal followed by re-oxidation approach to restore the structural stability and electrochemical performances of degraded Ni-rich layered cathode materials. Owing to this unique approach, the resultant LiNi_0.8Co_0.15Al_0.05O₂ (NCA) demonstrate improved layered structure, a stable nanoscale coating shell and enhanced surface stability. The revived NCA enables higher reversible capacity and longer cycle life than that of degraded NCA. Specifically, the restored NCA can retain 82 % initial capacity after 200 cycles under 1 C at room temperature, and 87 % and 55 % initial capacity after 100 and 500 cycles under 1 C at 55 °C, respectively. This approach could be applied to improve the structural stability and electrochemical properties of degraded Ni-rich layered oxides and suggests great potential in industrial applications.