Enhanced pseudocapacitive energy storage properties of Nb2O5/C core‐shell structures with the surface modification

Summary Pseudocapacitive energy storage is an attractive technology as it can achieve high energy density at high rate conditions. However, its practical application has been an issue because of low electrical conductivity of nanoscale electrode materials. Surface coating is an effective way to enhance the electrochemical properties of the electrochemical energy storage system by helping electron transfer between the electrode material and current collector. In order for surface coating technologies to be applied to pseudocapacitive energy storage field, providing fast ions and electrolyte transport through the coating layer as well as high electrical conductivity is essential because pseudocapacitors aim for high rate charge/discharge capability. In this paper, the Nb2O5/carbon core‐shell structure is developed to meet these requirements. Simple microwave‐assisted method is applied to create nanoscale (approximately 5 nm) conductive carbon layer on the surface of bare Nb2O5 nanoparticles, and the high power capability of Nb2O5/carbon core‐shell is improved further by oxidation process providing open structure for electrolyte and ion diffusion. Thick electrode architecture containing oxidized Nb2O5/carbon core‐shell shows superior high rate performance as capacities of 215 C g−1 are obtained at a 50 mV s−1 scan rate. Nanoscale carbon layer is evenly coated onto the surface of T‐Nb2O5 using simple microwave‐assisted hydrothermal process for the pseudocapacitive energy storage applications. Ion conducting channel is formed by activation process through the carbon layer, thus enhancing the high power characteristics of Nb2O5/carbon core‐shell structure. Electrochemical analysis on Nb2O5/carbon core‐shell electrodes shows that over 90% of current response is associated with the capacitive contribution.