An aqueous, wide-voltage window and biodegradable all-solid-state supercapacitor with an ultrahigh energy density

The growing demand for energy, coupled with the environmental pollution induced by traditional energy production, is pushing to find solutions for renewable energy storage. Herein, hierarchical porous carbon with a high specific surface area (2449.6 m(2)/g) has been synthesized from poplar wood chips by the molten salt activation. Simultaneously, a gel polymer electrolyte with excellent mechanical properties, thermal stability and biodegradability was prepared from alpha-cellulose. A simple all-solid-state supercapacitor was fabricated via hierarchical porous structure carbon electrodes and a gel polymer electrolyte, and the resultant device exhibited a high specific capacitance (133.0 F/g at 0.5 A/g) and an ideal capacitance retention rate (90.4% after 10,000 cycles). In addition, the device presented superior energy density (18.5 Wh/kg) and power density (500.0 W/kg) as compared with other supercapacitors. Interestingly, the gel polymer electrolyte showed a favorable natural degradation rate under aerobic sludge condition. Therefore, this fabricated electric double layer capacitor is expected to be used as a green and sustainable electronic device with amiable economic availability and environmental friendliness.