Unsymmetric design of self-supported sheet electrode: Breaking the tradeoff between electrical conduction and surface wetting for fast energy storage and excellent cycling stability

Biomass-derived porous carbon materials are suitable candidates for energy storage due to their rich pore structure, high specific area, and tunable surface functionality. Carbon electrodes are often required to have both excellent conductivity and wettability, while one needs to be compromised for optimized outcomes. Herein, we constructed a self-supported Carbonized Wood@Graphene Nanosheets (CW@GNs) composite electrode by growing GNs on one side of the CW surface with a plasma-enhanced chemical vapor deposition technology. Both electrical conductivity and interfacial wettability can be obtained simultaneously in CW@GNs electrodes. The CW@GNs-1h showed a satisfactory specific capacitance of 210.2F g⁻¹, while the value of pure CW was 177.2F g⁻¹. Furthermore, a symmetrical supercapacitor assembled with two CW@GNs-1h monoliths performed an excellent energy density of 7.8 Wh kg⁻¹ at 250.8 W kg⁻¹, retaining attractive cycling stability (99.02%) after 50,000 cycles. These results demonstrated the effectiveness of the unsymmetric design in a double-sided sheet electrode that breakthrough the tradeoff of electrical conductivity and surface wettability, and thus enhanced energy storage capacity and cycling stability were achieved.