N‑Doped Hierarchical Continuous Hollow Thin Porous Carbon Nanostructure for High-Performance Flexible Gel-Type Symmetric Supercapacitors

A N-doped hierarchical porous carbon nanostructure (NHPCN) was created on a carbon cloth (CC), through a templating process using self-assembled mesoporous silica spheres as the template, to fabricate high-performance flexible gel-type symmetric supercapacitors (NHPCN@CC//NHPCN@CC). The NHPCN@CC//NHPCN@CC cell exhibited outstanding capacitive performances, giving a decent energy density of 10.3 W h kg^–1 at a high power density of 10 kW kg^–1 and reaching a high energy density of 24.3 W h kg^–1 at a power density of 0.5 kW kg^–1, outperforming most carbon-based gel-type, symmetric supercapacitors. This success may be attributed to the continuous hollow, thin features of the NHPCN, with the hollow structure enabling local, fast adsorption/desorption of electrolyte ions for generation of electric double-layer capacitances and the thin carbon shells offering large amounts of exposed surface areas for accommodation of electric double-layer capacitances and pseudo-capacitances. The NHPCN@CC//NHPCN@CC cell exhibited a high specific capacitance retention rate of 85% after 8000 cycle operations at 10 A g^–1, showing its good cycling stability. The mechanical robustness of the NHPCN@CC//NHPCN@CC cell was also excellent, with the energy and power densities well-maintained even under a large bending angle of 135°.