Facile Li+ Transport in Interpenetrating O‐ and F‐Containing Polymer Networks for Solid‐State Lithium Batteries

Abstract Solid polymer electrolytes (SPEs) provide an intimate contact with electrodes and accommodate volume changes in the Li‐anode, making them ideal for all‐solid‐state batteries (ASSBs); however, confined chain swing, poor ion‐complex dissociation, and barricaded Li+‐transport pathways limit the ionic conductivity of SPEs. This study develops an interpenetrating polymer network electrolyte (IPNE) comprising poly(ethylene oxide)‐ and poly(vinylidene fluoride)‐based networked SPEs (O‐NSPE and F‐NSPE, respectively) and lithium bis(fluorosulfonyl) imide (LiFSI) to address these challenges. The CF2/CF3 segments of the F‐NSPE segregate FSI− to form connected Li+‐diffusion domains, and COC segments of the O‐NSPE dissociate the complexed ions to expedite Li+ transport. The synergy between O‐NSPE and F‐NSPE gives IPNE high ionic conductivity (≈1 mS cm−1) and a high Li‐transference number (≈0.7) at 30 °C. FSI− aggregation prevents the formation of a space‐charge zone on the Li‐anode surface to enable uniform Li deposition. In Li||Li cells, the proposed IPNE exhibits an exchange current density exceeding that of liquid electrolytes (LEs). A Li|IPNE|LiFePO4 ASSB achieves charge–discharge performance superior to that of LE‐based batteries and delivers a high rate of 7 mA cm−2. Exploiting the synergy between polymer networks to construct speedy Li+‐transport pathways is a promising approach to the further development of SPEs.