Building Lithiophilic Ion‐Conduction Highways on Garnet‐Type Solid‐State Li<sup>+</sup> Conductors
Zhangyuan Cheng, Maoling Xie, Yayun Mao, Jianxin Ou, Sijing Zhang, Zhao Zheng, Jinlin Li, Fang Fu, Jihuai Wu, Yanbin Shen, Derong Lu, Hongwei Chen
Abstract
Abstract The integration of highly conductive solid‐state electrolytes (SSEs) into solid‐state cells is still a challenge mainly due to the high impedance existing at the electrolyte/electrode interface. Although solid‐state garnet‐based batteries have been successfully assembled with the assistance of an intermediate layer between the garnet and the Li metal anode, the slow discharging/charging rates of the batteries inhibits practical applications, which require much higher power densities. Here, a crystalline sulfonated‐covalent organic framework (COF) thin layer is grown on the garnet surface via a simple solution process. It not only significantly improves the lithiophilicity of garnet electrolytes via the lithiation of the COF layer with molten Li, but also creates effective Li + diffusion “highways” between the garnet and the Li metal anode. As a result, the interfacial impedance of symmetric solid‐state Li cells is significantly decreased and the cells can be operated at high current densities up to 3 mA cm −2 , which is difficult to achieve with current interfacial modification technologies for SSEs. The solid‐state Li‐ion batteries using LiFePO 4 cathodes, Li anodes, and COF‐modified garnet electrolytes thus exhibit a significantly improved rate capability.