LiPF<sub>6</sub> Induces Phosphorization of Garnet‐Type Solid‐State Electrolyte for Stable Lithium Metal Batteries
Nan Chen, Boshun Gui, Binbin Yang, Chenglong Deng, Yaohui Liang, Fengling Zhang, Bohua Li, Wen Sun, Feng Wu, Renjie Chen
Abstract
Abstract Garnet solid electrolyte Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) is an excellent inorganic ceramic‐type solid electrolyte; however, the presence of Li 2 CO 3 impurities on its surface hinders Li‐ion transport and increases the interface impedance. In contrast to traditional methods of mechanical polishing, acid corrosion, and high‐temperature reduction for removing Li 2 CO 3 , herein, a straightforward “waste‐to‐treasure” strategy is proposed to transform Li 2 CO 3 into Li 3 PO 4 and LiF in LiPF 6 solution under 60 °C. It is found that the formation of Li 3 PO 4 during LLZTO pretreatment facilitates rapid Li‐ion transport and enhances ionic conductivity, and the LLZTO/PAN composite polymer electrolyte shows the highest Li‐ion transference number of 0.63. Additionally, the dense LiF layer serves to safeguard the internal garnet solid electrolyte against solvent decomposition‐induced chemical adsorption. Symmetric Li/Li cells assembled with treated LLZTO/PAN composite electrolyte exhibit a critical current density of 1.1 mA cm −2 and a long lifespan of up to 700 h at a current density of 0.2 mA cm −2 . The Li/LiFePO 4 solid‐state cells demonstrate stable cycling performances for 141 mAh g −1 at 0.5 C, with capacity retention of 93.6% after 190 cycles. This work presents a novel approach to converting waste into valuable resources, offering the advantages of simple processes, and minimal side reactions.