<p>Rechargeable Li | |Cl₂ batteries hold promise for low temperature storage but suffer from interfacial instability due to electrolyte decomposition, particularly at cryogenic temperatures. We identify the failure mechanism as a complex solvation chemistry involving Li⁺, reactive SOCl₂, and coordinating chloroaluminates that drives parasitic reactions. Here, we demonstrate a Ternary Solvation Sheath Reconfiguration strategy using lithium trifluoromethanesulfonate to engineer the solvation structure. By leveraging strong anion-cation interactions, this approach reconfigures the coordination environment to displace solvent molecules and directs the in-situ formation of a robust, bilayered positive electrode electrolyte interphase featuring an inorganic-rich inner layer. This engineered interphase effectively suppresses electrolyte degradation and enhances charge-transfer kinetics by lowering the Li⁺ desolvation barrier. Consequently, cells employing the Ternary Solvation Sheath Reconfiguration electrolyte sustain stable cycling at –40 °C (1000 mA g⁻¹), maintaining capacity retention of 99.2% and Coulombic efficiency of 99.2% after 1100 cycles, while enabling reliable operation even at –80 °C. This work establishes a systematic framework for designing functional interphases via solvation chemistry for sustainable energy storage.</p>