Inhibiting phase conversion and improving cyclic stability of Ni-rich layered oxide by high-valence element concentration gradient doping

Nickel (Ni)-rich layered oxide cathodes are believed to be one of the crucial materials for the development of high-energy density power batteries. However, accompanied by the Ni content of layered cathodes increases, it encounters some awkward issues such as sensitivity to moisture, side reactions, and gas production. Herein, by using a high-valency elements Tellurium (Te) doping strategy, we successfully design and fabricate the layered oxide cathode material Li[(Ni0.90Co0.10)0.99Te0.01]O2 (1.0 Te-NC90) with a high capacity of 231.36 mAh g−1 at 0.1C, which has high cycling stability of 95.01 % after 100 cycles at 0.5C, good thermal stability of 205 °C and high Li+ diffusion rate of 8.12 × 10−10 cm2 s−1. It has been found that the (0 0 3) interplanar spacing of 1.0 Te-NC90 cathode will increase from 0.472 nm to 0.491 nm due to the concentration gradient Te-doping strategy, which can promote Li+ diffusion. Besides, it can refine the grain structure and transform the primary particles from bulk-grained to rod-grained morphology, and these elongated and closely packed particles radiate from the center to the surface with a spoke-like arrangement, which effectively dissipates lattice strain generated during deeply charging states and suppresses the abrupt lattice transformation associated with the H2 → H3 phase, thereby avoiding the development of microcracks during cycling. In the meantime, robust Te-O bonds can keep the material lattice stable to prevent oxygen loss and TM ion movement. Therefore, this study reveals the significant role of trace Te-doping in enhancing crystal structure and electrochemical stability through microstructural engineering for the control of primary particle morphology.