Manipulating Local Chemistry and Coherent Structures for High-Rate and Long-Life Sodium-Ion Battery Cathodes
Haoji Wang, Hongyi Chen, Yu Mei, Jinqiang Gao, Lianshan Ni, Ningyun Hong, Baichao Zhang, Fangjun Zhu, Jiangnan Huang, Kai Wang, Wentao Deng, Debbie S. Silvester, Craig E. Banks, Sedat Yaşar, Bai Song, Guoqiang Zou, Hongshuai Hou, Xiaobo Ji
Abstract
Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na + transport kinetics, elucidated by density functional theory calculations. Elevated Jahn–Teller [Mn 3+ O 6 ] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na + diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn 2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g –1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.