Work

Site-Selective Fluorination for Decoupling Oxidative Stability and Ionic Transport of Oxychloride Solid Electrolytes

Year: 2026

Type: preprint

Abstract: Fluorination in solid electrolytes is widely used to enhance oxidative stability owing to fluorine's high electronegativity, yet strong Li–F interactions hinder Li-ion transport. Here we show that this anodic stability–ionic conductivity trade-off can be largely decoupled through lattice-level anion design in the highly Li-ion-conductive LiTaOCl4. By distinguishing oxygen's framework-linking role from chloride's transport-defining role, we targeted fluorination at framework-linking O-sites to minimize perturbation of the Li-ion conduction network. The fluorinated oxychlorides retain ~10 mS cm–1-class ionic conductivity while raising the oxidation onset from 4.08 to 4.27 V versus Li+/Li, improving capacity retention as catholytes cycled to 4.5 V. First-principles calculations reveal that fluorination stabilizes oxidation-prone O- and Cl-derived electronic states through an inductive effect, while transport-network topology and correlated lattice dynamics preserve fast Li-ion transport. These results establish site-selective anion occupation as a design principle for decoupling oxidative stabilization from fast ion transport in mixed-anion solid electrolytes.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15011034/v1