Organic Ionic Plastic Crystal/Polymer Composite Electrolyte Prepared By Solution Casting Method for Solid-State Lithium Batteries

Solid-state electrolytes have been considered as a promising candidate to address the safety issues for next-generation lithium batteries. Organic ionic plastic crystals (OIPCs) are attracting increasing interests as solid electrolyte materials due to their unique advantages, such as plasticity, nonflammability, good thermal and electrochemical stability. In this study, an OIPC-based composite electrolyte consisting of the OIPC 1-ethyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr 12 TFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and the polymer polyvinylidene fluoride (PVDF) has been developed by a facile solution casting strategy. A free-standing and flexible OIPC/polymer composite membrane was fabricated by the solution casting method, which not only provides flexibility and better electrode/electrolyte contact, but also is more compatible with current battery processing methods. The composite membrane used in Li/Li symmetric cell was cycled stably over 900 h at a current density of 0.1 mA cm −2 at 50 °C, demonstrating that the OIPC/polymer composite electrolyte enabled the reversible and stable lithium plating and stripping behaviors. Further tests of the OIPC/polymer composite as solid electrolyte in LiFePO 4 /Li cell presented a high specific capacity of 149 mAh g −1 at 0.1 C and a long cycle life of over 440 cycles with capacity retention of 89% at 0.5 C at 50 °C, which showed improved rate capability and cycling stability in comparison with the composites with similar compositions but obtained by powder pressing method. This study demonstrated the potential of the OIPC/polymer composite solid electrolyte prepared by solution casting method and will promote the development of high-performance OIPC-based composite electrolytes for solid-state batteries.