An optimized Al₂O₃ layer for enhancing the anode performance of NiCo₂O₄ nanosheets for sodium-ion batteries

Herein, an ultrathin Al₂O₃ layer was coated onto NiCo₂O₄ nanosheets via an atomic layer deposition (ALD) method, and the NiCo₂O₄ coated with an ALD-derived Al₂O₃ material was successfully used as an anode material for sodium-ion batteries (SIBs). This kind of electrode exhibited enhanced cycling performance with a reversible capacity of 395 mA h g⁻¹ after 50 cycles, and good rate capability with the discharge capacities of 350, 320, and 294 mA h g⁻¹ at the various current densities of 100, 200, and 400 mA g⁻¹, respectively. Interestingly, remarkable prevention of the reactions between the electrode and electrolyte was observed. The performance improvement is due to the protection of the NiCo₂O₄ coated with an ALD-derived Al₂O₃ layer from the electrochemical active materials. These results demonstrate the great potential of NiCo₂O₄ coated with an ALD-derived Al₂O₃ material as anodes in SIBs.