Based on the severe preparation conditions, large particle size and poor conductivity, a new method to prepare nano-flake sodium vanadyl phosphate is proposed. By the method of surface energy control technique under specific conditionsion, the controllable preparation of nano-flake sodium vanadyl phosphate was achieved. Through monitoring and analysis of the products under the different growth times, the formation process of nano-flake was studied, and the formation mechanism of sodium vanadyl phosphate was analyzed by density functional theory (DFT) simulation. The microstructure of sodium vanadyl phosphate is studied by adjusting the amount of sulfate radical, to verify the formation mechanism of unique nano-flake sodium vanadyl phosphate. The results show that the adsorption of $\text{SO}_{\text{4}}^{2}$ ions on different crystal faces changes the surface energy of different crystal faces, changes the dominant growth orientation of crystal nuclei, realizes directional growth and self-assembly, and finally gets the unique nano-flake sodium vanadyl phosphate. Because of the unique nano-flake micro-morphology, the prepared nano-flake sodium vanadyl phosphate has higher specific surface area and compaction density. The specific surface area of nano-flake sodium vanadyl phosphate is 16.2 m²/g, and the compaction density is 1.86 g/cm³, which is higher than that of the nano-particle sodium vanadyl phosphate, while 4.3 m²/g for the specific surface area and 1.77 g/cm³ for the compaction density of nano-particle sodium vanadyl phosphate. In addition, nano-flake sodium vanadyl phosphate also shows excellent sodium storage properties. Under the condition of current density at 0.1 C, the discharge specific capacity of nano-flake sodium vanadate phosphate reaches 93.76 mAh/g, which is larger than that of nano- particle sodium vanadyl phosphate (82.85 mAh/g) at the same discharge current density. At the same time, after 100 charge and discharge cycles at 10 C, 105% of the initial capacity can be maintained (in the same condition, only 92% of the initial capacity can be maintained for the nano-particle sodium vanadyl phosphate), showing good cycle stability.

Key words: nano-flake, sodium vanadyl phosphate, controllable preparation, surface energy, oriented growth