Revealing the influence of conversion-type CoO dimensionality on cyclic and rate performance for lithium storage.

Cobalt tetraoxide (CoO) is regarded as a promising anode material for Li-ion batteries owing to its high theoretical capacity (890 mAh g), simple preparation, and controllable morphology. Nanoengineering has been proven to be an effective method for producing high-performance electrode materials. However, systematic research on the influence of material dimensionality on battery performance is lacking. Herein, we prepared CoO with various dimensionalities (one-dimensional (1D) CoO nanorod (NR), two-dimensional (2D) CoO nanosheet (NS), three-dimensional (3D) CoO nanocluster (NC), and 3D CoO nanoflower (NF)) using a simple solvothermal heat treatment method, and their morphologies were controlled by varying the precipitator type and solvent composition. The 1D CoO NR and 3D samples (3D CoO NC and 3D CoO NF) exhibited poor cyclic and rate performances, respectively, while the 2D CoO NS exhibited the best electrochemical performance. The mechanism analysis revealed that the cyclic stability and rate performance of the CoO nanostructures are closely related to their intrinsic stability and interfacial contact performance, respectively, and the 2D thin-sheet structure can achieve an optimal balance between the two, resulting in the best performance. This work presents a comprehensive study on the effect of dimensionality on the electrochemical performance of CoO anodes, providing a new concept for the nanostructure design of conversion-type materials.