AbstractPhase‐change materials (PCMs) are a unique and exciting class of materials with bright prospects in wide‐ranging sustainable technologies such as thermal and electrochemical energy storage. While impressive, the effect of gaseous species on PCMs remains largely unexplored hitherto. Here, a gaseous co‐solvent is reported that can facilitate melting and modulate physical properties such as viscosity and ion conduction of PCMs. Especially for the appealing application of PCMs as electrolytes, gaseous species also have a critical influence on both Li⁺‐electrolyte structure and resultant solid electrolyte interphase (SEI). Specifically, theoretical simulations and experimental analysis evidence that CO₂ can promote melting while reconfiguring the solvation structure of a succinonitrile (SCL)‐derived Li⁺ phase‐change electrolyte (Li⁺‐PCE) model system. Due to the enhanced interaction between Li⁺ cations and bis(trifluoromethanesulfonyl)imide (TFSI^‐) anions in the reconfigured solvation structure, more TFSI^‐‐derived F‐rich component and extra CO₂‐derived Li₂CO₃ form in the upgraded SEI layer, thereby endowing proof‐of‐concept Li‐metal batteries with prolonged cyclability. These findings may stimulate widespread interest in gas leverage to innovate electrolyte chemistry.