Role‐Differentiated Solvation Directs Interfacial Chemistry in Wide‐Temperature Lithium Metal Batteries

ABSTRACT Wide‐temperature lithium metal batteries face intrinsic coupling between bulk transport and interfacial reactivity. Molecules enabling low viscosity and rapid Li + migration can enter the primary solvation sheath and undergo uncontrolled reduction on Li metal. Here, we establish solvation–reactivity decoupling through deliberate molecular role differentiation rather than empirical additive optimization. In the quaternary ester–ether (PADD) electrolyte, methyl propionate (MP) exhibits reduced primary Li + coordination and predominantly promotes fluidity, whereas DME/DOL and FSI − /TFSI − cooperatively reconstruct the reaction‐relevant solvation sheath. Systematic comparison reveals that MP exclusion alone is insufficient; a stable ether–anion network must compensate for the vacated coordination environment. This sheath redirects interfacial reduction toward DOL‐ and anion‐derived products, generating a spatially differentiated PDOL–LiF heteromatrix interphase with a compliant polymer‐rich outer region and a compact LiF‐rich inner framework. The interphase suppresses continuous ester decomposition, lowers nucleation and charge‐transfer barriers, and guides dense Li deposition. Consequently, Li||LiFePO4 cells operate from −30°C to 70°C, retaining 97.1% capacity after 1000 cycles at 25°C and 99.3% after 400 cycles at −30°C. These results identify functional differentiation across bulk electrolyte, solvation sheath, and interphase as a general route to resolve the transport–stability trade‐off in all‐climate lithium metal batteries.