Sulfolane-Based Gel Polymer Electrolytes Enhanced by 2D Boron Nitride Nanosheets for Optimized Ion Dynamics and Stability in Lithium Metal Batteries

Lithium metal batteries (LMBs) offer tremendous potential due to their high energy density, but practical applications are limited by challenges such as dendrite formation, safety risks, and interfacial instability. This study introduces a composite gel polymer electrolyte (GPE) that systematically integrates sulfolane-based highly concentrated electrolytes (HCEs) with two-dimensional hexagonal boron nitride nanosheets (BNNs). Through advanced experimental characterizations, electrochemical measurements, and theoretical calculations, the composite GPE is shown to achieve enhanced mechanical strength, thermal stability, and superior Li ion transport properties. The incorporation of BNNs not only reinforces the electrolyte matrix but also facilitates selective Li ion transport via strong interactions between Li ions and the filler, as validated by theoretical studies. The optimized composite GPE demonstrates outstanding electrochemical performance, achieving a high ionic conductivity of 0.7 × 10–3 S cm–1 at 30 °C and stable cycling for over 1000 h in Li/Li symmetric cells and more than 300 cycles in Li/LiFePO4 cells, along with excellent rate capabilities. This work provides a comprehensive strategy for addressing the critical limitations of LMBs and establishes a robust framework for developing next-generation high-performance solid-state battery systems.