Porous film host-derived 3D composite polymer electrolyte for high-voltage solid state lithium batteries

Abstract

Conventional lithium-ion batteries with liquid organic electrolytes generally suffer potential security risks concerning volatilization, flammability and explosion. Nonflammable and thin solid-state electrolytes particularly composite solid electrolytes (CSEs) that integrate the merits of different electrolyte systems have attracted increasing attention for advanced lithium batteries with improved energy density and high safety. In this work, a three-dimensional (3D) fiber-network-reinforced CSE, which consists of a mechanically robust, porous polyimide (PI) film as a host, Li6.75La3Zr1.75Ta0.25O12 (LLZTO) nanoparticles and poly (vinylidene fluoride) (PVDF) polymer matrix with bis-trifluoromethanesulfonimide lithium salt as electrolyte filler, is designed and fabricated. Such unique 3D CSE films with PI fiber network holding for uniform dispersion of LLZTO in PVDF show continuous lithium ion transfer pathways and effective prevention for lithium dendrite growth, consequently exhibiting improved mechanical property (high tensile strength of 11.5 ​MPa) and high cyclic stability (more than 1000 ​h of cycling for Li symmetric batteries). Furthermore, solid-state LiNi0.5Co0.2Mn0.3O2/Li pouch cells with the PI-PVDF/LLZTO CSE exhibit excellent cyclic stability (152.6 ​mA ​h ​g−1 with capacity retention of 94.9% at 0.1C after 80 cycles) at room temperature, and high functionality and safety (withstand harsh environments such as folding, cutting and nail penetration) in practical applications.