Macroporous Nb$_2$O$_5$ as a binder-free anode for hybrid supercapacitor

Abstract

Hybrid supercapacitors with battery-type electrodes offer higher energy density. However, these electrodes suffer from slow kinetic response, resulting in reduced capacity retention at high charge-discharge rates. To address this, researchers directly oxidized niobium metal without binders to create niobium oxide, an active material. Anodic oxidation formed niobium oxide films with a macro-porous structure, followed by heat treatment to produce orthorhombic-Nb2O5. Electrochemical analysis showed that anodically oxidized cathodes exhibited the highest capacity and retention. The resulting oxide was amorphous, providing more defects and void spaces compared to crystalline structures, enabling increased capacity and fast diffusion of lithium ions. Thus, samples with only anodically oxidized electrodes demonstrated higher capacity and retention compared to heat-treated samples. Additionally, comparisons with other studies confirmed that anodically oxidized niobium oxide electrodes outperformed those with binders in terms of capacity retention.