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–Li0.33La0.56TiO3–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 Li0.33La0.56TiO3–x for highly efficient transport. The BaTiO3–Li0.33La0.56TiO3–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 LiNi0.8Co0.1Mn0.1O2/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. The authors developed a highly conductive and dielectric composite solid-state electrolyte by coupling BaTiO3 and Li0.33La0.56TiO3–x nanowires with a side-by-side heterojunction structure in a polyvinylidene difluoride matrix, which simultaneously promotes the dissociation of lithium salts to produce more movable Li ions and efficiently transports the generated movable Li ions.