Microwave-Assisted Synthesis of NiCo2O4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries

The ternary transitional metal oxide NiCo 2 O 4 is a promising anode material for sodium ion batteries due to its high theoretical capacity and superior electrical conductivity. However, its sodium storage capability is severely limited by the sluggish sodiation/desodiation reaction kinetics. Herein, NiCo 2 O 4 double-shelled hollow spheres were synthesized via a microwave-assisted, fast solvothermal synthetic procedure in a mixture of isopropanol and glycerol, followed by annealing. Isopropanol played a vital role in the precipitation of nickel and cobalt, and the shrinkage of the glycerol quasi-emulsion under heat treatment was responsible for the formation of the double-shelled nanostructure. The as-synthesized product was tested as an anode material in a sodium ion battery, was found to exhibit a high reversible specific capacity of 511 mAh g −1 at 100 mA g −1 , and deliver high capacity retention after 100 cycles.