Three‐Dimensional Graphene Network Decorated with Highly Symmetrical Cuboid Na 3 V 2 (PO 4 ) 2 F 3 Particles: High Rate Capability and Cycling Stability for Sodium‐Ion Batteries

Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) has captured significant heed for cathode materials of sodium‐ion battery (SIB), owing to its stable three‐dimensional (3D) structure channel that can accommodate Na + diffusion. However, NVPF is still facing with a major challenge in terms of the electrochemical performance, owing to its uncontrollable morphology. Hence, it was fabricated by using a two‐step hydrothermal method, whereby NVPF cuboid particles of homogenous morphology and highly structural symmetry could anchor on the three‐dimensional graphene network (GN) structure to form NVPF@GN. The affiliation between the morphology and performance of the NVPF@GN was further probed by manipulating the morphology of the NVPF under diverse heat treatment temperatures. When the temperature reaches 480 °C, NVPF@GN manifests prolonged cyclability (the capacity fading rate of 0.01 % cycle −1 at 0.5 C during 300 cycles) and it shows outstanding rate performance (when the rate is reset to 0.5 C, the capacity is 107 mAh g −1 and capacity retention is 99 %), which can be ascribed to the high structural symmetry of NVPF@GN. These results indicate that NVPF@GN cuboids can be used as a prospective cathode material for SIBs.