Locally graphitized biomass-derived porous carbon nanosheets with encapsulated Fe3O4 nanoparticles for supercapacitor applications

Waste biomass-derived porous carbons offer significant application prospects, especially in the field of carbon-based supercapacitors, while simultaneously reducing carbon emissions. However, their relatively low conductivity and charge storage capacity have resulted in a low energy density for supercapacitor applications, thereby significantly impeding their large-scale commercial application. At present, comprehensively enhancing the performance of biomass-derived carbon-based supercapacitors (BC-SCs), including energy density, power density, cyclic stability, and rate capability, remains a challenge. To overcome this challenge, Fe3O4 nanoparticles with high conductivity are successfully encapsulated within biomass-derived carbon nanosheets. In conjunction with a localized graphitization strategy, a novel electrode material, locally graphitized biomass-derived hierarchical porous carbon nanosheets with encapsulated Fe3O4 nanoparticles, possessing high specific surface area and conductivity, is successfully prepared. Coupled with TFA electrolyte featuring a high working voltage of 1.4 V, a significant enhancement in the energy density is achieved for BC-SCs, along with ultra-long cyclic durability and excellent fast-charging capabilities. The BC-SCs assembled achieves a high energy density of 15.80 kW kg−1 at a power density of 483 W kg−1. Even at a high power density of 16.40 kW kg−1, the energy density remains at 11.4 Wh kg−1. After 100,000 cycles, the capacitance retention remains remarkably high at 99.6 %. By utilizing hydroquinone as a redox additive, the energy density can be further improved to 32.0 Wh kg−1. This work would pave the way for the large-scale commercialization of BC-SCs.