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.