Unusual Capacity Boost in Li/TiF3 Cells Enabled by a Li+ /Na+ Mixed Solid Electrolyte with High-Voltage Stability

Abstract

TiF₃ exhibits an anomalously large capacity when paired with a Li⁺/Na⁺ mixed NaI–NaBH₄–LiI electrolyte. TiF₃ shows no Ti³⁺ redox during operation, indicating interfacial Li⁺ storage as the dominant process. The Li⁺/Na⁺ mixed electrolyte provides superior high voltage stability, offering a mechanistic basis for the unusual capacity and highlighting its promise for solid state batteries.