Minimizing the interfacial resistance for a solid-state lithium battery running at room temperature

A ceramic solid electrolyte of Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) with high ionic conductivity (4.28 × 10⁻⁴ S cm⁻¹ at 30 °C) and low activation energy (0.25 eV) is prepared by a three-step method, and the interfacial properties of the ceramic solid electrolyte are further modified by an in-situ polymerization strategy with the formation of a gel-polymer electrolyte with the thickness of 8.85 μm on the surface of LAGP. The presence of the gel-polymer electrolyte on the surface of LAGP inhibits the side reactions and the growth of lithium dendrites, as evidenced by the stable cycling of the lithium symmetric cells with the modified LAGP solid electrolyte for 1000 h at 25 °C. In addition, the high ionic conductivity and the stable interface of the modified LAGP solid electrolyte enable the solid-state lithium battery with a LiFePO₄ cathode, exhibiting superior electrochemical performances which can run stably at 25 °C with initial discharge specific capacity of 159.8 mAh g⁻¹ at 0.1C.