Improving the Structure Stability of LiNi<sub>0.8</sub>Co<sub>0.15</sub>Al<sub>0.05</sub>O<sub>2</sub> by Double Modification of Tantalum Surface Coating and Doping
Xiaoyun Zhang, Panpan Zhang, Tianyi Zeng, Zhenlu Yu, Xingyu Qu, Xiaoqi Peng, Yu Zhou, Xiaoguang Duan, Aichun Dou, Mingru Su, Yunjian Liu
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.