CNTs embedded in layered Zn-doped Co₃O₄ nano-architectures as an efficient hybrid anode material for SIBs

Advantageous utilization of sodium-ion batteries (SIBs) requires superior performance, enriched with cost-effective anode materials, having excellent storage capability, high conductivity, and structural stability. Hybrid structures based on inorganic metal oxides and organic nano-carbons are evolving as satisfactory electrode materials for the next-generation SIBs owing to their exceptional properties. In this study, Co_2.98Zn_0.02O₄/CNTs hybrid is synthesized using a facile hydrothermal followed by a solvothermal route. As prepared hybrid has been utilized as an anode in a Na half cell and the results are compared with Co_2.98Zn_0.02O₄ and bare Co₃O₄ anodes. Galvanostatic charge-discharge profiles revealed a high reversible capacity of 721 mAh g⁻¹ for the electrode containing carbon nanotubes (CNTs) i.e. Co_2.98Zn_0.02O₄/CNTs exhibiting remarkable coulombic efficiency of 99% as compared to the other two electrodes. The hybrid anode showed improved capacity retention (289 mAh g⁻¹) after 100 cycles as computed from the cyclic test which is much higher than bare Co₃O₄. The rate capability test of Co_2.98Zn_0.02O₄/CNTs showed that specific capacity retained as high as 138 mAh g⁻¹@10 C which is an outstanding rate performance, whereas bare Co₃O₄ couldn't perform even after 0.5 C. Sodium insertion/extraction is also improved for Co_2.98Zn_0.02O₄/CNTs, as revealed by electrochemical impedance and diffusion coefficient. From these findings, it is inferred that carbon-based Zn-doped Co₃O₄ hybrid electrode materials can be a superior combination for high-performance and fast charging future SIBs.