An interfacially self-reinforced polymer electrolyte enables long-cycle 5.35 V dual-ion batteries

Abstract

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.