Polymer-Modulated Solvation Chemistry via Compatibilizing-Solvent Plasticization for Stable High-Energy Lithium Metal Batteries

Poly(vinylidene fluoride) (PVDF)-based polymer electrolytes plasticized with residual solvent are promising for high-energy and high-safety lithium metal batteries. However, their practical realization is constrained by the reliance on miscible yet electrochemically unstable plasticizers (such as N,N-dimethylformamide), which compromise both lithium reversibility and high-voltage compatibility. Guided by a descriptor-informed screening, we identify several electrochemically favorable plasticizers, but their thermodynamic immiscibility with polymers precludes homogeneous plasticization. Here, we propose a compatibilizing-solvent-enabled plasticization strategy that leverages a transient solvent to lower the effective Flory–Huggins interaction parameter, thereby enabling the homogeneous plasticization of poly(vinylidene fluoride-co-hexafluoropropylene) with immiscible plasticizers. Using sulfolane as a representative plasticizer, the resulting polymer–sulfolane (Fδ−–Hδ+) interactions suppress sulfolane migration and modulate an anion-aggregate solvation structure, leading to anion-derived fluorine-rich solid–electrolyte interphases. Consequently, the polymer electrolyte delivers an average lithium plating/stripping Coulombic efficiency of 99.1% over 1400 cycles, supports stable cycling of 4.7 V Ni-rich cathodes at 20C (7.1 mA cm–2), and achieves an energy density of 451.5 Wh kg–1 in Ah-scale pouch cells. More broadly, this work establishes a general route for expanding the plasticizer design space of PVDF-based polymer electrolytes, offering a promising direction toward practical lithium metal batteries.