Architecting with a flexible and modified polyethylene oxide coating for ambient-temperature solid-state Li metal batteries

Abstract

Sodium superionic conductor (NASICON)-type conducting ceramic Li1+xAlxTi2−x(PO4)3 (LATP) has been regarded as one of the most promising candidates for high-safety and high-energy density solid-state Li metal batteries (SSLMBs) because of its high ionic conductivity and good chemical stability. However, the large interfacial impedance and instability between the solid electrode and LATP electrolyte severely hinder its practical application in solid-state batteries. To overcome this technical challenge, we demonstrate a polymer–ceramic–polymer composite electrolytes (PCPCEs) prepared through drop casting, which ameliorates the interfacial stability between the solid electrolyte and the electrode. PCPCEs with an ideal ambient-temperature ionic conductivity can drastically reduce the interfacial resistance between the LATP and solid electrodes and effectively avoid a direct reaction and contact between them. As a result, the interfacial impedance decreases from 30,000 to 280 Ω for the Li–LATP interfaces and from 40,000 to 800 Ω for the LATP–LiFePO4 (LFP) interfaces. Meanwhile, the polarization voltage of the Li||PCPCEs||Li symmetric cell reduces from 1.5 V to 100 mV. The solid-state Li metal batteries assembled with a Li metal anode, LFP cathode, and PCPCEs exhibit a desired initial discharge capacity of 152.5 mAh g−1 and a good cycling performance at 0.1 C for 25 °C. This study provides a prospective insight to improve the poor interface between the solid electrode and inorganic conducting ceramic.