PVDF/PVB composite polymer electrolyte membranes with high conductivity and excellent cycling performance for lithium‐ion batteries

Abstract

Polymer electrolytes, which eliminate the hazards of using liquid electrolytes, including electrolyte leakage, thereby showing high safety and stability, exhibit high potential for application in lithium‐ion batteries (LIBs). However, for applicability in high‐performance LIBs, improving the ionic conductivity of polymer electrolytes is vital. This study proposes a new scheme for fabricating polyvinylidene fluoride (PVDF)/polyvinyl butyral (PVB) composite polymer electrolyte membranes with high conductivity. As expected, the PVDF/PVB composite membranes synthesized in this study show a high porosity (48.8%) and liquid electrolyte uptake (110%) owing to low crystallinity; PVDF/PVB (9:1) gel polymer electrolytes (GPEs) exhibit an excellent ionic conductivity of 3.90 × 10−3 S/cm at 20 °C and a good Li+ transference number (0.62). Consequently, Li||LiFePO4 cells with PVDF/PVB (9:1) GPEs show excellent cycling performance, a high discharge capacity, which changes only slightly from 153.98 to 132.09 mAh/g over 100 cycles at 0.2 °C, thereby showing a capacity retention of 93.5%, and a high coulombic efficiency of 98.35%. Finally, a mechanism for Li‐ion transport in PVDF/PVB GPEs is proposed. Strong non‐bonded interactions between the anhydride polar groups in PVB and Li+ could facilitate Li+ migration via cationic Li+ conduction by fixing anions (PF6−), thereby improving the electrochemical performance of the system. Thus, this study confirms that PVDF/PVB GPEs, with excellent ionic conductivity and cycling performance, exhibit promising application prospects in the field of LIBs. Therefore, the results of this study could open new frontiers in the fabrication of high‐performance and stable LIBs.