All-cellulose-based quasi-solid-state supercapacitor with nitrogen and boron dual-doped carbon electrodes exhibiting high energy density and excellent cyclic stability

The key to construct high-energy supercapacitors is to maximize the capacitance of electrode and the voltage of the device. Realizing this purpose by utilizing sustainable and low-cost resources is still a big challenge. Herein, N, B co-doped carbon nanosheets are obtained through the proposed dual-template assisted approach by using methyl cellulose as the precursor. Due to the synergistic effects form the high surface area with the hierarchical porous structure, N/B dual doping, and a high degree of graphitization, the resultant carbon electrode exhibits a high capacitance of 572 F g-1 at 0.5 A g-1 and retains 281 F g-1 at 50 A g-1 in an acidic electrolyte. Furthermore, the symmetric device assembled using bacterial cellulose-based gel polymer electrolyte can deliver high energy density of 43 W h kg-1 and excellent cyclability with 97.8% capacity retention after 20 000 cycles in "water in salt" electrolyte. This work successfully realizes the fabrication of high-performance allcellulose-based quasi-solid-state supercapacitors, which brings a cost-effective insight into jointly designing electrodes and electrolytes for supporting highly efficient energy storage.& COPY; 2022 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).