Photothermal Supercapacitors with Gel Polymer Electrolytes for Wide Temperature Range Operation

To deliver electrochemical energy over a wide range of temperatures, this work studies a new gel polymer electrolyte (GPE) for photothermal supercapacitors operating from −60 to 65 °C. The GPE consists of polyacrylonitrile mixed with an active filler sodium polystyrenesulfonate that simultaneously improves ionic conductivity and traps metal cation impurities. The self-discharge rate and impurity diffusion coefficients in the supercapacitors were lowered by the active filler to minimize energy loss in hot environments. For cold settings, the devices were packaged with a photothermal conversion layer that increased the internal cell temperature and raised the energy density to 94 μWh/cm2 at the output power density of 0.4 mW/cm2 in a −60 °C chamber. The combination of our improved GPE and photothermal conversion increased the stored energy and thereby extended the operational time of a motor driven from a cold start by a supercapacitor, demonstrating a high-performance design suitable for harsh environments.