Boron Nitride Nanosheet-Based Gel Polymer Electrolytes for Stable Lithium Metal Batteries

Abstract

In order to address the safety concerns of conventional carbonate liquid electrolytes in lithium (Li) batteries, porous gel polymer electrolytes (GPEs) can encapsulate the solution while providing good electrolyte–electrode contact. In this work, a GPE is designed and fabricated with multifunctional exfoliated two-dimensional (2D) hexagonal boron nitride nanosheets (BNs), leading to improved thermal stability, ionic conductivity, Li+ transference number, mechanical strength, and dendrite-suppressing properties for Li metal batteries. Through phase inversion, a high porosity and electrolyte uptake are achieved while maintaining a stable film structure. Utilizing a binary polymer mixture of polyvinylidene fluoride (PVDF) and poly(ethylene oxide) (PEO) doped with exfoliated BN flakes, the final BN-GPE at 3.6 wt % BN can effectively suppress dendrite growth through multiple charge/discharge cycles with a high ionic conductivity of 3.03 × 10–3 S/cm at ambient conditions while showing a high Li transference number of 0.60. The Li metal battery cell performance with this GPE demonstrates a strong initial capacity at 82.9 mAh/g at 0.5C and improves capacity over the undoped GPE by 22% after 45 cycles.