Improving the oxidative stability of gel polymer electrolytes for lithium metal batteries

Abstract

Currently, commercial lithium (Li) ion batteries (LIBs) do not meet the energy density (>350 W h kg⁻¹) required for vehicle electrification; therefore, alternative materials are required. Lithium metal batteries (LMBs) are promising secondary battery candidates for next-generation, eco-friendly energy conversion given their high theoretical gravimetric capacities (3862 mA h g⁻¹). However, strong reduction by Li metal electrochemically decomposes the electrolytes, reducing battery performance, safety, and stability. To overcome these potential issues, the LMB electrolyte must be very resistant to oxidation. Here, we used leakage current tests to investigate the oxidation stability of organic electrolytes for LMBs. We performed quantum and molecular dynamics simulations to clarify the effects of gel polymers added to the electrolyte. We focused on changes in the behaviors of free organic molecules after the addition of polymers, and the highest/lowest occupied molecular orbital energy levels of various molecular configurations. The leakage current tests revealed improvements to the oxidation stability of an organic-based electrolyte. In addition, polymer addition resulted in a decrease in free organic molecule levels, improving the oxidation stability of the entire system as revealed by the highest occupied molecular orbital energy values of the various molecular configurations.