Honeycomb-like amorphous VPO4/C spheres with improved sodium storage performance as anode materials for sodium-ion batteries

Abstract

In this article, honeycomb-like amorphous VPO4/C spheres were successfully synthesized via a sol-gel combined hydrothermal route and then tested as anode materials for sodium-ion batteries. After characterized by structure analysis, morphological observation, and composition determination, the prepared VPO4/C materials exhibit amorphous structure and spherical morphology with honeycomb-like core framework shielded by compact out-layer shell when compared with its crystalline counterpart. As anode material for sodium storage performance, the amorphous VPO4/C delivers a high discharge capacity of 421.1 mAh g−1 at a current density of 100 mA g−1 and exhibits a good cycling stability upon 100 cycles under 500 mA g−1. The enhancement of electrochemical sodium storage performances can be attributed to the honeycomb-like inner structure facilitating the diffusion of sodium ion and the observable compact out-layer buffering the large volume strains in cycling. Meanwhile, the observed channel-like caves can provide wealthy space for storing richer sodium ion, leading to higher capacity. The proposed viewpoint points out that the synthesis of amorphous architecture is a new strategy to break through the limitation of anode materials for sodium-ion batteries.