A dielectric electrolyte composite with high lithium-ion conductivity for high-voltage solid-state lithium metal batteries

Abstract

The ionic conductivity of composite solid-state electrolytes does not meet the application requirements of solid-state lithium (Li) metal batteries owing to the harsh space charge layer of different phases and low concentration of movable Li⁺. Herein, we propose a robust strategy for creating high-throughput Li⁺ transport pathways by coupling the ceramic dielectric and electrolyte to overcome the low ionic conductivity challenge of composite solid-state electrolytes. A highly conductive and dielectric composite solid-state electrolyte is constructed by compositing the poly(vinylidene difluoride) matrix and the BaTiO₃-Li_0.33La_0.56TiO_3-x nanowires with a side-by-side heterojunction structure (PVBL). The polarized dielectric BaTiO₃ greatly promotes the dissociation of Li salt to produce more movable Li⁺, which locally and spontaneously transfers across the interface to coupled Li_0.33La_0.56TiO_3-x for highly efficient transport. The BaTiO₃-Li_0.33La_0.56TiO_3-x effectively restrains the formation of the space charge layer with poly(vinylidene difluoride). These coupling effects contribute to a quite high ionic conductivity (8.2 × 10^-4 S cm^-1) and lithium transference number (0.57) of the PVBL at 25 °C. The PVBL also homogenizes the interfacial electric field with electrodes. The LiNi_0.8Co_0.1Mn_0.1O₂/PVBL/Li solid-state batteries stably cycle 1,500 times at a current density of 180 mA g^-1, and pouch batteries also exhibit an excellent electrochemical and safety performance.