Conversion of Surface Residual Alkali to Solid Electrolyte to Enable Na‐Ion Full Cells with Robust Interfaces

作者：Wei-Liang Xu, Rongbin Dang, Lin Zhou, Yang Yang, Ting Lin, Qiubo Guo, Fei Xie, Zilin Hu, Feixiang Ding, Yunpeng Liu, Yuan Liu, Huican Mao, Juan Hong, Zhanchun Zuo, Xiaoqi Wang, Rui Yang, Xu Jin, Xueyan Hou, Yaxiang Lu, Xiaohui Rong, Ning Xu, Yong‐Sheng Hu · 发表于：Advanced Materials · 年份：2023 · DOI：10.1002/adma.202301314 · 被引用次数：113 · 研究领域：Advancements in Battery Materials、Advanced Battery Materials and Technologies、Advanced battery technologies research

Abstract The deposition of volatilized Na+ on the surface of the cathode during sintering results in the formation of surface residual alkali (NaOH/Na2CO3NaHCO3) in layered cathode materials, leading to serious interfacial reactions and performance degradation. This phenomenon is particularly evident in O3‐NaNi0.4Cu0.1Mn0.4Ti0.1O2 (NCMT). In this study, a strategy is proposed to transform waste into treasure by converting residual alkali into a solid electrolyte. Mg(CH3COO)2 and H3PO4 are reacted with surface residual alkali to generate the solid electrolyte NaMgPO4 on the surface of NCMT, which can be labeled as NaMgPO4@NaNi0.4Cu0.1Mn0.4Ti0.1O2‐X (NMP@NCMT‐X, where X indicates the different amounts of Mg2+ and PO43−). NaMgPO4 acts as a special ionic conductivity channel on the surface to improve the kinetics of the electrode reactions, remarkably improving the rate capability of the modified cathode at a high current density in the half‐cell. Additionally, NMP@NCMT‐2 enables a reversible phase transition from the P3 to OP2 phase in the charge–discharge process above 4.2 V and achieves a high specific capacity of 157.3 mAh g−1 and outstanding capacity retention in the full cell. The strategy can effectively and reliably stabilize the interface and improve the performance of layered cathodes for Na‐ion batteries (NIBs).