Understanding and suppressing gas evolution in lithium metal batteries with ether-based electrolytes

Understanding and suppressing gas evolution is critical to enabling high-energy-density lithium metal batteries (LMBs). Yet, comprehensive investigations in ether-based systems remain limited. Here we quantify gas generation in ether-based LMBs and elucidate the underlying mechanisms. We link CO and CO2 production to the cathode, and CH4 evolution to the anode. Notably, CO and CO2 are consumed at the Li anode to form Li-containing species such as Li2CO3. Although CH4 ultimately dominates the gaseous products, its evolution during cycling is delayed until a distinct onset point. We show that in a high-concentration ether electrolyte, anode activation improves Li deposition morphology and suppresses interfacial reactions, extending the number of cycles to gas onset and cell failure by an order of magnitude. Achieving these gains without altering the electrolyte enables the reconsideration of seemingly impractical electrolytes, highlighting a practical strategy to enhance the safety and performance of commercial LMBs. Gas evolution compromises the safety and commercial viability of high-energy lithium metal batteries. Now it has been shown that CH4 generated by ether-based electrolyte decomposition at the Li anode dominates gas evolution. A facile anode activation strategy suppresses CH4-forming interfacial reactions, dramatically reducing gas evolution and extending cycle life.