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 all-cellulose-based quasi-solid-state supercapacitors, which brings a cost-effective insight into jointly designing electrodes and electrolytes for supporting highly efficient energy storage.

构建高能超级电容器的关键是最大化电极电容和器件电压。通过利用可持续且低成本的资源来实现这一目的仍然是一个巨大的挑战。在此，使用甲基纤维素作为前体，通过所提出的双模板辅助方法获得了N、B共掺杂碳纳米片。由于高表面积与分级多孔结构、N/B双重掺杂和高度石墨化的协同效应，所得碳电极在0.5 A g -1 和0.5 A g -1 下表现出572 F g -1的^高电容和在 50 A g ⁻¹时保留 281 F g ⁻¹在酸性电解质中。此外，使用细菌纤维素基凝胶聚合物电解质组装的对称装置可以提供43 W h kg ^-1的高能量密度和优异的循环性能，在“盐包水”电解质中循环20 000次后容量保持率为97.8%。这项工作成功实现了高性能全纤维素基准固态超级电容器的制造，为联合设计电极和电解质以支持高效储能提供了具有成本效益的见解。