(65d) A Facile Microwave-Assisted Route to Co(OH)2 and Co3O4 Nanosheet for Li-Ion Battery

Cobalt hydroxide (Co(OH)₂), as one of the most important functional inorganic materials, can be used in the field of catalysis and electrochemical electrodes. The previous report revealed that Co(OH)₂ is a promising alternative conversion-based anode materials for lithium-ion batteries (LIBs) due to its high capacity. Unfortunately, like other conversion-based anode materials, the implementation in LIBs is greatly hampered by its poor cycling performance. One of the most promising strategies to tackle this obstacle is to make Co(OH)₂ into sheet-like structure to improve the structural stability in the electrochemical reactions. Compared with the bulk Co(OH)₂, Co(OH)₂nanosheet displays obvious advantages due to large surface area, highly oriented growth direction, tunable interlayer space for the de/insertion of lithium ions.

In this work, a facile microwave-assisted synthetic route has been successfully developed for preparing hexagonal Co(OH)₂ nanosheets with average width of 2 μm and thickness of 100 nm. Co(OH)₂ can further convert to porous Co₃O₄nanosheets via thermal decomposition. Their phases, structures and morphologies were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Both Co(OH)₂ and Co₃O₄ nanosheets can serve as potential candidates for anodes of Li-ion battery. The electrochemical study revealed that Co(OH)₂ and Co₃O₄ nanosheets delivered a reversible capacity of 600 and 700 mAh g^-1 after 40 cycles, respectively. Cyclic voltammetry (CV) curves also confirmed the relative stability of the as-synthesized electrode materials. This effective microwave-assisted route may be a promising approach for preparing other transition metal hydroxide/oxides for energy applications.