Self-assembled nickel-cobalt oxide microspheres from rods with enhanced electrochemical performance for sodium ion battery

Exploring new anode materials with promising electrochemical capacity is essential for rechargeable sodium-ion batteries. The selection and structural design of electrode materials play key role in the development of a viable battery with high specific capacity and cycle retention. Herein, self-assembled NiCo₂O₄ microspheres comprised of numerous sub-micron sized rods are prepared for the first time by a simple co-precipitation method. The synthesized microspheres have homogeneous morphology and a multimodal porosity. The resulting sodium ion storage properties demonstrate that the NiCo₂O₄ microsphere anode offers excellent electrochemical performance, with a high reversible capacity of 620 mAh g⁻¹ at a current density of 0.05 A g⁻¹. It also shows an exceptionally high rate capability up to 10 A g⁻¹ equivalent to 11 C-rate, which can be attributed to the existence of capacitive behavior. Notably, the rate performance and cycling stability are significantly higher than most previously reported results of NiCo₂O₄ nanostructures for sodium-ion batteries (SIBs).