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

Abstract

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°.

Heteroatom-Doped Pillared Porous Carbon Architectures with Ultrafast Electron and Ion Transport Capabilities under High Mass Loadings for High-Rate Supercapacitors

“…To obtain fast electron and ion transport characteristics for carbon materials at commercial-level mass loadings, an ideal electrode material for supercapacitors needs the characteristics of (1) high electron conductivity, (2) short ion diffusion distance, and (3) high ion-accessible surface area. Recently, numerous studies have shown that various heteroatom (oxygen, sulfur, boron, phosphorus, and nitrogen) doping of carbon can enhance the electrochemical capacitive behaviors of carbon-based materials. − On the one hand, the favorable interactions of heteroatoms with ions can reduce the ionic resistance at the electrode/electrolyte interface and hence improve the wettability and the ion-accessible surface areas of carbon . On the other hand, heteroatom doping can improve electrical conductivity by enhancing the free charge-carrier density.…”