Biomass-derived interconnected carbon nanoring electrochemical capacitors with high performance in both strongly acidic and alkaline electrolytes

Besides a lack of low-cost electrode materials, the match between the electrode materials and electrolytes is one of the top issues to achieve high-rate electrochemical supercapacitors. Herein, we report an environmentally friendly strategy to prepare three-dimensionally interconnected carbon nanorings (TDICNs) from biomass waste, batata leaves and stalks (BLS). The microstructure of TDICNs matches well with acidic and alkaline electrolytes, making them exhibit high specific capacitances of 532.5 F g−1 (1 A g−1) and 264.0 F g−1 (30 A g−1), excellent capacitance retention (95.1% and 91.7% after 1000 cycles at 1 A g−1 and 10 000 cycles at 30 A g−1, respectively) and a high energy density of 25.8–11.9 W h kg−1 with a power density of 249.5–13 068.0 W kg−1 in 1 mol L−1 H2SO4 aqueous electrolyte. In 6 mol L−1 KOH electrolyte, they still exhibit high specific capacitances of 350.0 F g−1 (1 A g−1) and 246.9 F g−1 (30 A g−1), excellent cycling stability (95.06% and 91.1% of capacitance retention after 1000 (1 A g−1) and 10 000 (30 A g−1) cycles, respectively), a high energy density of 24.5 W h kg−1 and a power density of 12 918.0 W kg−1.