Heterojunction‐Accelerating Lithium Salt Dissociation in Polymer Solid Electrolytes

Abstract The practical application of solid‐state lithium‐metal batteries (SSLMBs) based on polymer solid electrolytes has been hampered by their low ion conductivity and lithium‐dendrite‐induced short circuits. This study innovatively introduces 1D ferroelectric ceramic‐based Bi 4 Ti 3 O 12 ‐BiOBr heterojunction nanofibers (BIT‐BOB HNFs) into poly(ethylene oxide) (PEO) matrix, constructing lithium‐ion conduction highways with “dissociators” and “accelerating regions.” BIT‐BOB HNFs, as 1D ceramic fillers, not only can construct long‐range organic/inorganic interfaces as ion transport pathways, but also install “dissociators” and “accelerating regions” for these pathways through the electric dipole layer and built‐in electric field of BIT‐BOB HNFs, promoting the dissociation of lithium salts and the transfer of lithium ions. The working mechanisms of BIT‐BOB HNFs in the polymer matrix are verified by experimental tests and density functional theory calculations. The obtained composite solid electrolytes exhibit excellent lithium‐ion conductivity and migration number (6.67 × 10 −4 S cm −1 and 0.54 at 50 °C, respectively). The assembled lithium symmetric battery achieves good cycling stability of over 4500 h. The LiFePO 4 ||Li full battery delivers a high Coulombic efficiency (>99.9%) and discharge capacity retention rate (>87%) after 2200 cycles. In addition, the prepared composite polymer solid electrolyte demonstrates good practical application potential in flexible pouch batteries.