Composite Solid Electrolyte for Solid-State Lithium Batteries Workable at Room Temperature

Solid polymer electrolytes play a vital role in improving the safety of lithium batteries. However, low ionic conductivity and poor mechanical property limit their further applications. Herein, we fabricated a composite solid electrolyte (CSE) based on a polymer (polyvinylidene fluoride-hexafluoro propylene, PVDF-HFP) and an inorganic filler of porous graphitic carbon nitride (PGCN) nanosheets with a high specific surface area. The porous structure facilitated good distribution of PGCN in the PVDF-HFP matrix and offered abundant PVDF-HFP/PGCN interfaces, which might be beneficial for the Li+ transport. The CSE showed high ionic conductivity (2.3 × 10–4 S/cm at 30 °C), excellent cycling performance, and outstanding physical and chemical properties. Moreover, the correlation of the ionic conductivities of the CSEs and the specific surface of the PGCN fillers was discussed, and the results revealed that the ionic conductivity of the CSE was increased with the increase in the specific surface of PGCN, indirectly demonstrating that the transport of the Li+ was mainly conducted on the interfaces between the polymer and the inorganic fillers.