Organic Ionic Plastic Crystal-Based Composite Electrolyte with Surface Enhanced Ion Transport and Its Use in All-Solid-State Lithium Batteries

Solid-state electrolytes have been identified as one of the most attractive materials for the fabrication of reliable and safe lithium batteries. This work demonstrates a facile strategy to prepare highly conductive organic ionic plastic crystal (OIPC) composites by combination of a low weight fraction of Li+ doped OIPC (N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide, [C2mpyr][FSI]) with commercial poly(vinylidene difluoride) (PVDF) powder. Benefiting from the enhancement of lithium ion dynamics, as evidenced by the solid-state NMR measurements, the composite electrolyte shows an order of magnitude higher conductivity than that of the bulk material. Lithium metal/LiFePO4 cells incorporating the prepared composite electrolytes show impressively high specific capacity and good cycling stability (99.8% coulombic efficiency after 1200 cycles at 2 C, room temperature), which is the first demonstration of long-term cycling performance at such high rate for an OIPC-based electrolyte. The high voltage cathode, LiCo1/3Ni1/3Mn1/3O2 was tested and good rate performance and stable capacities have been achieved.