Design of porous calcium phosphate based gel polymer electrolyte for Quasi-solid state sodium ion battery

Abstract

The design of a suitable separator is an effective approach to enhance the performance as well as the safety of a rechargeable battery. The conventional glass fiber separator has electrolyte leakage due to the random distribution of pores in the structure. The design of a gel polymer electrolyte with phosphorus containing compound is considered to be safer for the operation of a rechargeable sodium ion battery. Hence, we have developed a gel polymer using hydroxyapatite, a calcium phosphate-based compound in poly (vinylidene fluoride-hexafluoropropylene)-poly (butyl methacrylate) blend membrane by a simple solution casting technique. The developed membrane has an ionic conductivity of 1.086 × 10−3 S cm−1 with an electrochemical stability of up to 4.9 V, good porosity and electrolyte uptake, thereby making it a promising electrolyte to be used in a rechargeable sodium ion battery. To demonstrate its feasibility, the electrochemical properties of Na3V2(PO4)3/C are investigated using the prepared gel polymer electrolyte. The sodium ion cell using gel polymer electrolyte exhibits a specific capacity of 97 mAh g−1 at 4 C which is about 33.5% enhancement in specific capacity when compared to the cell with the conventional glass fiber membrane. This study illustrates the feasibility of using gel polymer electrolyte as a replacement to the existing glass fiber separator.