Hollow NiO/NiCo2O4@carbon nanocages as anode materials for high-performance lithium-ion batteries

As a kind of binary metal oxide, NiCo₂O₄ has been widely studied as anode material for lithium ion batteries (LIBs) owing to its high theoretical capacity and environmental friendliness. However, the large volume changes during cycling and the semiconductive properties make it difficult to meet the commercial demands. In this paper, hollow carbon nanocages (HCNCs) are employed as substrates to prepare NiO/NiCo₂O₄@HCNCs composites by solvothermal synthesis. The combination of NiCo₂O₄ and NiO leads to improved electrochemical performance due to their synergistic effects. The existence of HCNCs overcomes the interfacial instability between NiCo₂O₄ and NiO, which facilitates the ion/electron transport. Moreover, the hollow structure not only increases the contact area between the material and the electrolyte, providing more active sites for electrochemical reactions, but also alleviates the structural strain caused by Li⁺ embedding and de-embedding during cycling. Therefore, NiO/NiCo₂O₄@HCNCs composites show improved rate capability and cycling performance. At a current density of 0.2 A g⁻¹, the specific capacity reaches 1051.91 mAh g⁻¹ after 200 cycles, with a remarkable Coulombic efficiency of 99.4 %. Even at a high current density of 5 A g⁻¹, the specific capacity still reaches 352.81 mAh g⁻¹.