A Flexible Dual‐Ion Battery Based on PVDF‐HFP‐Modified Gel Polymer Electrolyte with Excellent Cycling Performance and Superior Rate Capability

Abstract Dual‐ion batteries (DIBs) have attracted increasing attention owing to their merits of high working voltage, low cost, and especially environmental friendliness. However, the cycling stability of most DIBs is still unsatisfying due to the decomposition of conventional liquid carbonate electrolytes under high working voltages. Exploration of gel polymer electrolytes (GPEs) with good electrochemical stability at high voltage is a possible strategy to optimize their cycling stability. A high‐performance flexible DIB based on a poly(vinylidene fluoride‐hexafluoro propylene) GPE codoped with poly(ethylene oxide) and graphene oxide via weak bond interactions is herein reported for the first time. The prepared polymer electrolyte shows a 3D porous network with significantly improved ionic conductivity up to 2.1 × 10 −3 S cm −1 , which is favorable for fast ionic transportation of both cations and anions. As a result, this DIB exhibits excellent cycling stability with a capacity retention of 92% after 2000 cycles at a high current rate of 5C (1C is corresponding to 100 mA g −1 ), which is among the best performances of DIBs. Moreover, good flexibility and thermal stability (up to 90 °C) are also achieved for this battery, indicating its potential applications for high‐performance flexible energy storage devices.