Exceptional interfacial conduction and LiF interphase for ultralong life PEO-based all-solid-state batteries

Abstract

Composite electrolytes, with large ionic conductivity and stable seamless interfaces, are recognized as potential ones for solid-state batteries (SSBs). Herein, a flexible all-solid-state composite electrolyte composed of TiO2 (Bronze) nanotubes and poly(ethylene oxide) was synthesized. The composite electrolyte was found to be able to offer an exceptional interfacial conduction and a reasonable electrode compatibility in the SSBs. The interfacial phase between TiO2(B) and polymer formed a new lithium-ion transport pathway, which enhanced the interfacial conduction. Moreover, DFT and MD simulation showed that TiO2(B) can promote the dissociation of lithium salts and produce more free lithium ions, thereby enhancing the ionic conductivity. Furthermore, the incorporations of TiO2(B) can achieve a rich LiF interphase layer, realizing a rapid lithium-ion transport and uniform Li deposition, as was revealed by the results of TOF-SIMS, Cryo-TEM, and COMSOL Multiphysics. Consequently, the symmetric lithium cell obtained an excellent electrochemical performance of more than 2350 h and a high critical current density of 1.6 mA cm−2. The as-prepared LiFePO4/Li SSBs exhibited an impressive ultralong cycle lifespan of over 3100 cycles at 1 C. This work is regarded as opening a new avenue for designing reasonably the ultralong life of PEO-based SSBs.