An interfacially self-reinforced polymer electrolyte enables long-cycle 5.35 V dual-ion batteries†
Dual-ion batteries (DIBs) have grand prospects for use in electric vehicles owing to their high voltage and low cost. However, the electrochemically catalyzed electrolyte decomposition arises from incompatible cathode/electrolyte interfaces at high voltages, which can hinder their extensive applications. The adoption of polymer electrolytes provides a feasible strategy to address such a critical issue. Herein, an interfacially self-reinforced polymer electrolyte of polyvinylidene fluoride/polyvinyl acetate (PVDF/PVAc) is proposed to enhance the electrochemical performance of DIBs. It is found that PVAc can trap poisonous POF3, forming PVAc derivatives with superior oxidation resistance and mitigating the autocatalytic electrolyte decomposition. Meanwhile, these derivatives along with PVDF construct an F-rich cathode/electrolyte interface, which remarkably restrains carbonate decomposition. By virtue of this self-reinforcement strategy, the polymer electrolyte DIB (PDIB) exhibits improved average coulombic efficiency of 96% even under a high cut-off voltage of 5.35 V vs. Li/Li+ and achieves outstanding cyclability with 92% capacity retention after 2000 cycles. Moreover, PDIB is applicable in a wide temperature range between −10 °C and 60 °C. This polymer chemistry reinforcement strategy will boost the development of low-cost DIBs and enlighten other related high-voltage batteries.