Biomimetic synthesis of craspedia globosa-shaped Na3V2(PO4)3 with high performance for sodium ion batteries

Na3V2(PO4)3 (NVP) possesses high capacity and structural stability to make it a research hotpot. Generally, traditional solid-state and sol-gel routes are explored to synthesize NVP. No detailed mechanism is proposed to illustrate the growth process of NVP grains in hydrothermal environment. In current work, we prepare the craspedia globosa-shaped NVP by a hydrothermal route adopting the methyl alcohol media. The growth mode of NVP crystal in hydrothermal environment is speculated and proposed. Summarily, vanadium pentoxide acts as the nucleating point, preferentially combining with phosphorus to form the crystal channels to accommodate the Na+, finally constructing the whole lattice framework. The precursor is tended to be the craspedia globosa-shaped material under the optimal hydrothermal condition (180 ℃). Essentially, the sheet structure in the grains’ interval is adsorbed and packaged on the surface to gradually form the globular particle in the force of surface tension. The unique craspedia globosa morphology covered by interlaced pathways on the surface efficiently increases the contact areas between active material and electrolyte, providing sufficient channels for the accelerated ionic and electronic transportation. Accordingly, the optimized craspedia globosa-shaped NVP sample (NVP-180) delivers a superior sodium storage property in both half and full cell.