Constructing a Dielectric Fluorinated Solid Electrolyte for Practically Operated All-Solid-State Lithium-Metal Batteries

Abstract

The operation of all-solid-state lithium-metal batteries is primarily constrained by an inferior solid electrolyte. Here, we employ a porous dielectric fluorinated electrolyte to encapsulate a Li⁺ complex, achieving rapid and stable ion conduction throughout cycling. The electrolyte comprises a porous nanofiber (NF) skeleton made of dielectric fluorinated BaTiO₃ (F-BaTiO_3−δ) and all-trans block copolymer PVDF-b-PTFE, with an encapsulated poly(ethylene oxide) (PEO)-LiTFSI filler. The dielectric polarized NFs effectively dissociate LiTFSI to form a rapid conductive Li⁺ complex, while F-BaTiO_3−δ bonds with PVDF-b-PTFE and PEO to create stable cross-phase Li⁺-conduction paths. This results in an electrolyte with a high room-temperature conductivity of 5.64 × 10^–4 S cm^–1 and a low activation energy of 0.21 eV. Additionally, the polarized electrolyte achieves dynamic interface stability by eliminating the space charge layer on the cathode and internal stress on the anode. The all-solid-state LiFePO₄//Li batteries can cycle stably 1000 times at 0.5 C with a high capacity retention of 87.45%. Furthermore, the NCM811//Li and 30-Ah-pouch cells also demonstrate high cycling stability, showcasing potential commercial applications.