Creating ionic channels in single-ion conducting solid polymer electrolyte by manipulating phase separation structure

Abstract

Single-ion conducting solid polymer electrolytes (SICSPEs) with high ionic conductivity are vital for next-generation electrochemical devices. Herein, we presented a novel method to manipulate the phase separation structure of SICSPEs, leading to the construction of long-range conducting ionic channels for rapid ion transport. Ionic nanowires were first fabricated by anchoring numerous lithium sulfonyl(trifluoromethanesulfonyl)imide groups on poly(ether ether ketone) backbones. Then, the ionic nanowires were dispersed in a well-designed hyperbranched polymer, poly(polyethylene glycol methyl ether methacrylate), to fabricate a blend membrane. Intertwined and continuous ionic channels were observed in the blend membrane by transmission electron microscopy. The blend membrane exhibited high conductivity of 0.17 × 10⁻³ to 1.01 × 10⁻³ S cm⁻¹ and an outstanding lithium ion transference number of 0.898–0.936. A half-cell using LiFePO₄ and the blend membrane exhibited discharge capacities (0.2C) of 121.7 and 152.7 mA h g⁻¹ at 25 and 60 °C, respectively. This study revealed a facile strategy to design high-performance ion-conducting membranes that are attractive for use in lithium ion batteries.