Molecular-Level Cleavage and Kinetics Optimization in PVDF Electrolytes for Anode-Lean Ultrastable Solid-State Sodium Batteries

Polymer-based solid-state electrolytes are promising for safe and high-energy batteries but are fundamentally constrained by low ionic conductivity and unstable electrode interfaces. Here, we propose a molecular-level design using Na3P as a dual-function nanofiller in poly(vinylidene fluoride) (PVDF) electrolytes. The nucleophilic P3- selectively cleaves C-F bonds, reducing polymer crystallinity and releasing F- species, while Na3P simultaneously serves as a built-in fast-ion conductor. Theoretical simulations reveal that Na3P remodels the solvation structure, lowers the desolvation barrier from 9.96 to 2.84 eV, facilitates salt dissociation and reduces F- migration barrier from 4.23 to 3.0 eV, collectively promoting Na+ mobility and raising bulk conductivity to 6.93 × 10-4 S cm-1. The released F- promotes in situ formation of a dense, NaF-rich solid-electrolyte interphase, enabling homogeneous Na plating. Consequently, an anode-lean solid-state sodium battery exhibits exceptional stability, with only 0.002% capacity fade per cycle over 1000 cycles at 5C and >5700 cycles at 10C. A high-loading pouch cell (12 mg cm-2) also maintains stable performance for more than 100 cycles, underscoring the practical potential of this kinetics-optimized electrolyte system for high-energy-density solid-state batteries.