Flexible thermotolerant Zn-ion hybrid supercapacitors enabled by heat-resistant polymer electrolyte

Hydrogel electrolytes often fail at high temperatures and thus common Zn-ion energy storage devices are rarely employed under high temperature conditions. Herein, a flexible heat-resistant nonflammable polymer electrolyte membrane has been prepared and employed in the fabrication of Zn-ion energy storage devices. The optimum electrolyte membrane exhibits a high room-temperature ionic-conductivity (∼1.52 × 10^-3 S cm⁻¹) along with a wide window of electrochemical stability (∼2.5 V). The membrane also shows a high tensile strength (4.3 MPa) and good flame-retardant performance. Moreover, it can effectively restrain the parasitic hydrogen evolution reaction as well as the Zn-dendrite formation. The Zn-ion hybrid supercapacitor (Zn-HS) fabricated with the membrane demonstrates good flexibility and thermotolerant performance. At a current density of 1 A/g, the device possesses a specific capacitance of 162.6 F/g at room temperature, 362.6 F/g at 80 °C, and 404.2 F/g at 100 °C. It also exhibits a long-term cycling capability (up to 30,000 cycles) even at 80 °C. Conclusively, the present work offers a promising way in designing heat-resistant nonflammable polymer electrolytes for flexible energy storage devices suitable for high-temperature applications.