Self-generated hollow NaTi2(PO4)3 nanocubes decorated with graphene as a large capacity and long lifetime anode for sodium-ion batteries

NaTi2(PO4)(3) is a promising anode material for sodium-ion batteries due to its sodium-super-ion-conductor type structure. However, the inherent low conductivity of the NaTi2(PO4)(3) limits its cyclability and rate capability. Herein, to overcome these shortcomings, an electrode material that combines the hollow NaTi2(PO4)(3) nanocubes with the reduced graphene oxide is synthesized by a simple hydrothermal method. The as-synthesized products demonstrate a high specific capacity of 128 mA h g(-1), nearly achieving its theoretical capacity of the NaTi2(PO4)(3) electrode at 0.1C; even when the discharging rate reached 50C, it still achieved a capacity retention of 60%. Simultaneously, the sample also shows stable cycling performance with a discharge capacity of 60 mA h g(-1) after 500 cycles at a high rate of 20C. This excellent electrochemical performance of the NaTi2(PO4)(3)@rGO is attributed to the large surface area of the hollow structure and high conductivity of the three-dimensional reduced graphene oxide that facilitate the electrolyte to soak in, increase the contact area between the nanocubes and electrolyte, and speed up Na+/e(-) transfer in the nanocomposites. In addition, the unique hollow structure and the combination with the graphene could effectively accommodate the volume variation during repeated sodiation/desodiation processes.