Fabrication and evaluation of high-performance cylindrical supercapacitors using double-layered Ni-based electrodes

Cylindrical supercapacitors were fabricated using Ni₂(CO₃)(OH)₂-based transition metal electrodes synthesized via a hydrothermal method, and the electrochemical performances of single-layer and double-layer electrode configurations were systematically compared. Both devices were designed to maintain the same total electrode area, with a graphite anode inserted at the core to ensure stable electron transport and mechanical robustness. Electrochemical evaluations revealed that the single-electrode device exhibited a specific capacity of 112.4 mAh g⁻¹ at a current density of 2 A g⁻¹, while the double-layered device showed 101.7 mAh g⁻¹ under the same conditions. Moreover, the single-layer electrode delivered an energy density of 30.4 Wh kg⁻¹ and a power density of 406.4 W kg⁻¹, whereas the double-layered electrode achieved improved values of 49.3 Wh kg⁻¹ and 548.3 W kg⁻¹, respectively. These results demonstrate that the cylindrical structure fabricated by rolling double-layered electrodes effectively mimics the architecture of commercial energy storage systems, providing a practical approach for evaluating real-world applicability.