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

Abstract

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.