Sponge‐Like Cathode Material Self‐Assembled from Two‐Dimensional V2O5 Nanosheets for Sodium‐Ion Batteries

A sponge‐like V2O5 nanomaterial is prepared by a freeze–drying method and evaluated as a cathode material for sodium‐ion batteries. The sponge‐like structure is self‐assembled from V2O5 nanosheets that can sustain high pressure (400 times their own weight), thus leading to a high structure stability. The numerous macropores in the spongy structure can effectively soak up the electrolyte. Moreover, the exposed (001) facet of the nanosheets is favorable for charge transfer at the electrolyte/electrode interface. The thin nanosheets along the [001] axis provide short diffusion pathways for sodium ions. Electrochemical experiments show that the material has a high discharge capacity of 216 mAh g−1 at a current density of 20 mA g−1. In addition, the material shows a good capacity retention of 73 % in 100 charge–discharge cycles at a current density of 100 mA g−1.