Improving the Structure Stability of LiNi_0.8Co_0.15Al_0.05O₂ by Double Modification of Tantalum Surface Coating and Doping

Abstract

The structural instability of high-nickel materials severely limits their commercial applications. In this article, a one-step high-temperature solid-phase sintering method is applied to form a Ta2O5 protective layer on the surface of LiNi0.8Co0.15Al0.05O2 (NCA) with Ta5+ entering the lattice, which achieves the double-effect of coating and doping. The Ta2O5 protective coating can inhibit the side reaction between the electrode material and electrolyte, and Ta5+ doping can relieve the Li+/Ni2+ disorder ratio. These significantly enhance the structural stability of NCA. The obtained NCA-Ta2O5 displays an excellent capacity retention rate (94.46%, at 1C after 200 cycles), which is much better than that (60.97%) of the pristine NCA. The exploration of structural evolution reveals that NCA-Ta2O5 can maintain a good spherical structure without obvious cracks after 200 cycles at 1C, while the original NCA has a serious structural collapse. Besides, NCA-Ta2O5 presents outstanding discharge capacity (151.02 mAh g–1 vs NCA: 131.70 mAh g–1) at a high rate of 10C. This work provides ideas for improving the performance of high-nickel materials, which is of great significance to the optimization of the cathode material for lithium-ion batteries.