Facile in situ polymerization synthesis of poly(ionic liquid)-based polymer electrolyte for high-performance solid-state batteries

The rational one-step design of poly(ionic liquid) solid polymer electrolyte (PIL-SPE) with outstanding ionic conductivity and inferior interfacial resistance with Li-electrode to preclude the Li-dendrite growth and interfacial instability of solid-state lithium metal batteries (ASLMBs) remains a grand challenge. Herein, we provide a s facile, one-step, and productive approach for the synthesis of PIL-SPE via the in situ polymerization of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfony)imide ([VBIm][TFSI]) in the presence of bis(trifluoromethane) sulfonamide lithium salt (LiTFSI) using azodiisobutyronitrile (AIBN) as initiator. This approach endows a compact and compatible interface between Li-electrode and PIL-SPE with an excellent ionic conductivity that depends on the Li-salt concentration. Thereby, in situ polymerization of monomer with 40 wt% LiTFSI (PIL-SPE-LiTFSI-40) revealed the highest ionic conductivity of 1.35 × 10-3 S cm−1 at 303 K and 6.16 × 10-3 S cm−1 at 353 K, besides excellent lithium transference number (0.54), oxidative stability up to 5.3 V, and constant current plating/stripping cycles for 1000 h at 0.15 mA cm−2. Meanwhile, ASLMBs composed of PIL-SPE with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes delivered discharge capacities of 164.3 mA h g−1 and 155.3 mA h g−1 at 0.1C, respectively, along with 92 % capacity retention after 100 cycles. This study may revolutionize the synthesis of PIL-SPE electrolytes for the next generation of efficient and durable ASLMBs.