Electrochemical characteristics of dense PVDF-PEGDME polymer electrolytes for solid state lithium-ion batteries

The objective of solid electrolyte lithium-ion battery (LIB) research is to alleviate the disadvantages (explosiveness) of liquid LIBs and improve the electrochemical properties of solid electrolyte LIBs. Previously reported solid polymer LIBs using a poly (ethylene glycol) dimethyl ether-based solid polymer electrolyte (P-SPE) exhibited excellent electrochemical properties, stability, and strong resistance to bending and cutting. A composite polymer electrolyte was prepared in this study by adding 5 and 7 wt% poly (vinylidene difluoride) (PVDF) to the P-SPE. The PVDF-added P-SPE (PFP-SPE) exhibited excellent thermal stability (250 °C), and ionic conductivity (7 wt% PFP-SPE; 1.14 × 10-4 s/cm at room temperature and 4.27 × 10-4 s/cm at 333 K). The charge/discharge characteristics of a solid LIB full-cell (3 × 4 cm2 pouch-type: cathode; LiFePO4, anode; graphite) using a PFP-SPE were evaluated as a function of the N/P ratio. The N/P ratio in the full-cell of the PFP-SPE battery exhibited a stable capacity value over a wide range. The full-cell batteries with 5 wt% PFP-SPE exhibited excellent retention rates of 81.4 % after 100 cycles and a high capacity of 104.9 mAh/g at 0.1C.