Nb2O5/graphene nanocomposites for electrochemical energy storage

Abstract

The development of electrode materials for energy storage, with high energy and power densities along with good cyclic stability, still remains a big challenge. Here we report the synthesis of Nb₂O₅/graphene nanocomposites, through a simple hydrothermal method, with Nb₂O₅ nanoparticles anchored on reduced graphene oxide (RGO) sheets. The fabricated Nb₂O₅/graphene electrodes exhibited an excellent electrochemical performance when studied as anodes for lithium-ion batteries, with a superior reversible capacity and high power capability (192 mA h g⁻¹ under 0.1C rate over 50 cycles). Signature curve studies showed high power capability of the Nb₂O₅/graphene electrode with ∼80% of the total capacity retained at 16C rate compared to ∼30% retention for pristine Nb₂O₅ nanoparticles. To achieve further improvement in energy density and power capability, Li-ion hybrid electrochemical capacitors (Li-HECs) were fabricated with the Nb₂O₅/graphene nanocomposite as the anode and rice husk-derived activated porous carbon as the cathode, in non-aqueous electrolyte. The Li-HECs showed enhanced electrochemical performance with high energy density of 30 W h kg⁻¹, at a specific power density of 500 W kg⁻¹. The Nb₂O₅/graphene nanocomposites show promising results and hence have great potential for application in efficient electrochemical energy storage devices.