Solvothermal Fabrication of Hollow Nanobarrel-Like ZnCo2 O4 Towards Enhancing the Electrochemical Performance of Rechargeable Lithium-Ion Batteries

Synergistic effect between ZnCo2O4 and Co3O4 induces superior electrochemical performance as anodes for lithium-ion batteries

The current work describes a facile synthesis of spinel-type ZnCo2O4 along with an additional phase, Co3O4, by simply maintaining a non-stoichiometric ratio of Zn and Co precursors. Pure ZnCo2O4 and Co3O4 were also synthesized using the same method to compare results. The obtained morphologies of samples show that small-sized nanoparticles are interconnected and form a porous nanosheet-like structure. When used as anode materials for Li-ion batteries, the ZnCo2O4/Co3O4 nanocomposite electrode exhibits a highly stable charge capacity of 1146.2 mA h g-1 at 0.5C after 350 cycles, which is superior to those of other two pure electrodes, which can be attributed to its optimum porosity, synergistic effect of ZnCo2O4 and Co3O4, increased active sites for Li+ ion diffusion, and higher electrical conductivity. Although the pure Co3O4 electrode displayed a much higher rate capability than the ZnCo2O4/Co3O4 nanocomposite electrode at all investigated current rates, the Co3O4 morphology apparently could not withstand long-term cycling, and the electrode became pulverized due to the repeated volume expansion/contraction, resulting in a rapid decrease in the capacity.

Recent Advances of ZnCo2 O4 -based Anode Materials for Li-ion Batteries

ZnCo₂ O₄ has been attracted wide research attention as a promising anode material for lithium-ion batteries (LIBs) in recent years based on its high theoretical specific capacity, low toxicity as well as stable chemical properties. However, the further large-scale application of pristine ZnCo₂ O₄ anode have been impeded because of its undesirable Li⁺ ion conductivity, low electronic conductivity, and finite stability of electrolytes at high potentials. Recently, optimizing the micro/nano structure, modification with carbonaceous materials, incorporation with metal oxides and constructing a binder-free structure on conductive substrate for ZnCo₂ O₄ -based materials have been verified as promising effective routes for solving the above problems. In this review, the recent advances in underlying reaction mechanisms, synthetic methods and strategies for improving the performance of ZnCo₂ O₄ anodes are comprehensively summarized. The factors affecting the electrochemical properties of ZnCo₂ O₄ -based materials are mainly discussed, and paths to promote the specific capacity and cyclic stability are proposed. Finally, several insights into the future developments, challenges, and prospects of ZnCo₂ O₄ -based anode materials of LIBs are proposed.

Facile Synthesis of Porous ZnCo₂O₄ Nanosheets and the Superior Electrochemical Properties for Sodium Ion Batteries

ZnCo₂O₄ nanosheets with large surface area and mesoporous structure were synthesized using a facile hydrothermal method followed with a calcination process. When applied as the anode material in sodium ion batteries, the ZnCo₂O₄ nanosheets demonstrated a high initial charge capacity of 415.1 mAh/g at the current density of 100 mA/g. Even though the reversible capacity decreased in the first 20 cycles, it stayed relatively stable afterwards and retained 330 mAh/g after 100 cycles. This result was superior to those of many reported works of ZnO- and Co₃O₄-based anodes for sodium ion batteries, which might be due to the synergistic effect of both Zn and Co, and the refined porous nanosheet-like structure which facilitates electrochemical reactions by providing more reaction sites and ensures cycling stability by providing more space to accommodate the structural strains during cycles.