LiF doped β-PbSnF4 with improved ionic conductivity toward high-performance all-solid-state fluoride-ion batteries

Abstract

All-solid-state fluoride ion batteries (ASSFIBs), which operate through anion shuttling without alkali metal anodes, represent an emerging energy storage technology offering cost-effectiveness, enhanced safety, and high energy density. In this work, a novel fluoride conductor of LiF doped β-PbSnF₄ (PbSnF₄@LiF) with a high F-ion conductivity of 7.9 × 10⁻⁴ S cm⁻¹ at room temperature was synthesized via a simple and facile method. The substitution of Pb atoms with Li dopants alters the c-axis length of the β-PbSnF₄ unit cell and generates F-ion site vacancies, enhancing F-ion mobility. As a result, the full cell, assembled with a CuF₂ cathode and Pb/PbF₂ anode, demonstrated an ultra-stable cycling life, maintaining a capacity of 300 mA h g⁻¹ for over 350 cycles when operated at a high current density of 75 mA g⁻¹. Notably, this is the most stable ASSFIB reported so far.