N-doped hard/soft double-carbon-coated Na3V2(PO4)3 hybrid-porous microspheres with pseudocapacitive behaviour for ultrahigh power sodium-ion batteries

Abstract The development of sodium-ion batteries with high power density is highly challenging yet critically important in many applications. Herein, we develop sodium-ion batteries with ultrahigh power density by using N-doped hard/soft double-carbon-coated Na3V2(PO4)3 hybrid-porous microspheres as a cathode. A higher working potential of 3.4 V, superior rate capability (93 mA h g−1 at 10C, 81 mA h g−1 at 30C) as well as stable cycling performance (72.9% capacity retention at 10C after 1000 cycle) are simultaneously achieved. Very impressively, it can deliver pseudocapacitive behavior and a practical energy density of 317 W h kg−1 at a power density of 194 W kg−1, which also remains 73.5 W h kg−1 even at an ultrahigh power density of 12600 W kg−1. The superior performances can be ascribed to the hybrid-porous microsphere structure, which provide favorable kinetics for bath electron and Na+, large cathode-electrolyte contact area, as well as robust structural integrity. This design provides a promising pathway for developing low-cost sodium-ion batteries with high energy density as well as high power density.