Upcycling of waste battery separators for energy storage applications

The recycling of spent batteries has primarily focused on the recovery of cathode and anode materials, as well as electrolytes, while little attention has been paid to the reuse of battery separators. In this study, a urea-assisted pyrolysis strategy involving gradient heating and isothermal treatment was proposed to achieve efficient recycling and value-added utilization of spent battery separators. By tailoring the pyrolysis protocol, the separators were successfully converted into carbon materials with a hierarchically porous structure and a high specific surface area of up to 2083 m² g⁻¹. Electrochemical measurements revealed that the carbon electrode exhibited an excellent specific capacitance of 321.1 F g⁻¹ at a current density of 0.5 A g⁻¹, and maintained nearly unchanged capacitance after 10,000 cycles at a high rate of 3 A g⁻¹. The symmetric supercapacitor assembled from the obtained carbon material delivered an energy density of 9.1 Wh kg⁻¹ at a power density of 250 W kg⁻¹. This work not only provided a novel pathway for the resource utilization of battery separators but also offered technical support for the development of green and sustainable energy storage devices, balancing both environmental and economic benefits.