Molecular‑Geometry‑Guided Lithium Salt Initiator Strategy for High‑Performance Poly(1,3‑dioxolane) Electrolytes in Lithium Metal Batteries

Abstract

In-situ polymerized electrolytes represent a promising approach to enable safe and high-energy-density lithium metal batteries. Poly(1,3-dioxolane) (PDOL) has attracted considerable interest in this regard, with its performance strongly influenced by the choice of polymerization initiator. Here, we present a molecular-geometry-guided strategy for selecting lithium salt initiators by focusing on the structure and H₂O-binding affinity of the Lewis acid intermediates they produce. Density functional theory calculations reveal that near-planar intermediates such as PO₂F (derived from LiPO₂F₂) exhibit higher binding energy with H₂O than sterically hindered species like PF₅ (from LiPF₆), resulting in accelerated initiation kinetics. This leads to a PDOL matrix consisting of shorter polymer chains, which provides enhanced segmental mobility and improved Li⁺ transport. The corresponding F2-PDOL electrolyte demonstrates high ionic conductivity and maintains enough thermal stability. The F2-PDOL-assembled LiFePO₄/Li full cells enables outstanding rate performance (76 mAh g^-1 at 20 C), long-term cycling stability (96.21% capacity retention after 400 cycles at 1 C), and reliable operation at elevated temperatures. This work demonstrates a rational, geometry-directed initiator selection strategy that offers a useful design method for high-performance polymer electrolytes in lithium metal batteries.