Porous coral-like Na3V2(PO4)3 enabled by Si4+ doping and N-doped carbon coating for advanced sodium-ion batteries

The slow Na + diffusion and low intrinsic electrical conductivity of Na 3 V 2 (PO 4 ) 3 (NVP) limit its practical application in sodium-ion batteries (SIBs). A synergistic enhancement approach of Si 4+ substitution and N-doped carbon coating has been introduced in this paper to produce a porous coral-like Na 3.1 V 2 (PO 4 ) 2.9 (SiO 4 ) 0.1 @NC-2 (NVPS@NC-2) composite. Si 4+ incorporation into the NVP lattice expands the Na + migration channels and decreases the bandgap so that intrinsic electronic conductivity of NVP was enhanced as confirmed by density functional theory calculations. Additionally, the N-doped carbon coating forms numerous extrinsic defects and creates a novel porous coral-like morphology that boosts the specific surface area. The initial specific capacity of NVPS@NC-2 cathode achieves 115.7 mAh g −1 at a current density of 0.1C. And even at 60/120C, NVPS@NC-2 cathode still exhibits 98.9/66.2 mAh g −1 , maintaining 92.9% and 90.6% capacities after 5000/10000 cycles, respectively, showing its viability for advanced SIBs applications.