LiPF6 Induces Phosphorization of Garnet-Type Solid-State Electrolyte for Stable Lithium Metal Batteries

Garnet solid electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is an excellent inorganic ceramic-type solid electrolyte; however, the presence of Li2CO3 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 Li2CO3, herein, a straightforward "waste-to-treasure" strategy is proposed to transform Li2CO3 into Li3PO4 and LiF in LiPF6 solution under 60 degrees C. It is found that the formation of Li3PO4 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/LiFePO4 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.