Constructing VS4/Nb2O5/GO composite to facilitate rapid Na+ transport with internal and external synergy

Abstract

Transition metal polysulfides/oxides typically perform high reversible capacities in sodium-ion batteries/capacitors (SIBs/SICs), but low conductivity and slow redox reaction kinetics are still the main challenges for achieveing fast kinetics. Here, we construct the VS4/Nb2O5/GO composite structure, which can promote the overall conductivity and structural stability through the GO and VS4 bonding (V-C and S-C) on the surface. Meanwhile, the chain-like VS4 and Nb2O5 connected with the V-O chemical bond can accelerate the electron and ion transfer internally, thus enabling the internal structure exposed during the activation process. Additionally, the bonding of VS4 and Nb2O5 is calculated by density functional theory (DFT), indicating that the strong metallic properties of the composite. When as the anode material of SIBs, the specific capacity of 268.8 mA h g−1 can be maintained after 2000 cycles at a current density of 10 A g−1. After that, SICs are assembled using activated carbon (AC) as the cathode, which exhibit 58.01 Wh kg−1 at high power density of 3800 W kg−1. This unique composite structure design can provide a reference for achieving fast electron and ion transport both internally and externally to the electrode material.