Surfactant-assisted synthesis of self-assembled Na3V2(PO4)2F3@C microspheres as the cathode for Na-ion batteries

Structurally stable Na3V2(PO4)2F3 (NVPF) is regarded as a promising cathode due to its large theoretical specific capacity. However, the poor electrical conductivity of NVPF results in poor rate capability. Herein, the tNVPF with dense textured microsphere structure was prepared by sodium dodecyl benzene sulfonate (SDBS)-assisted solvothermal method. The unique microstructure assembled by ∼100 nm nanorods provides massive active sites and promotes the fast transmission of Na + carriers. The electronic conductivity of tNVPF is further improved through coating by carbonizing polyacrylamide (PAM) to form tNVPF@C with great Na+ storage performance. Textured carbon-coated Na3V2(PO4)2F3(tNVPF@C) microspheres deliver a highly specific capacity (113.6/74.7 mAh·g−1 at 0.2/10 C) and better long-term cycling performance with capacity retention ratio of 80.1% after 300 cycles at 5 C. Remarkably, the Na-ion full cell, which is assembled by commercial hard carbon as anode and tNVPF@C as cathode, can achieve a high capacity of 118.9 mAh·g−1 and energy density of 322.6 W h·kg−1.