Surface stabilization for enhancing air/moisture resistance of layered Ni-rich oxide cathodes
Zhouliang Tan, Feng Xu, Ruizhuo Zhang, Yudai Huang, Xia Liu, Shupeng Yang, Yizhong Guo, Qingcui Liu, Tianlong Wu, Ying‐de Huang, Torsten Brezesinski, Yu Tang, Wengao Zhao
Abstract
Layered Ni-rich oxides (LiNi x Co y Mn z O 2 , with x ≥ 0.8 and x + y + z = 1) are promising cathode materials for high-energy-density lithium-ion batteries (LIBs) owing to their high specific capacity and high operating voltage. However, the Ni-rich cathode suffers from notorious deterioration when in contact with ambient air, primarily driven by nickel's multivalent (Ni 2 ⁺/Ni 3 ⁺/Ni 4 ⁺) reactions and humidity sensitivity. In this study, we report a novel surface modification strategy for LiNi 0.83 Co 0.12 Mn 0.05 O 2 (NCM83) via Li x SiO y coating, achieved through chemical grafting using the silane coupling agent, (3-aminopropyl) triethoxysilane (KH550), followed by thermal treatment. The modified NCM83 exhibits enhanced moisture resistance due to a superhydrophobic surface that suppresses detrimental reactions between residual lithium species (Li 2 O, LiOH, etc.) and water. Furthermore, the Li x SiO y coating mitigates mechanical degradation by facilitating strain relaxation. Notably, the modified NCM83 retains high electrochemical performance after 28 days of air exposure, delivering a specific capacity of 157 mAh g⁻ 1 after 100 cycles at 1C, compared to 108 mAh g⁻ 1 for the uncoated counterpart. Overall, these findings present an effective strategy for improving upon the surface stability of Ni-rich cathodes, facilitating their processing and paving the way for large-scale applications in high-energy LIBs.