沉淀剂对纳米氢氧化钴形貌结构及电化学性能的影响

Effect of precipitants on morphology structure and electrochemical performance of nano cobalt hydroxides

以硝酸钴为原料,采用水热法考察不同沉淀剂对所合成氢氧化钴的形貌结构及其电化学性能的影响。借助扫描电镜、X射线衍射和红外光谱等对材料的形貌和结构进行表征。结果表明,采用尿素或氨水为沉淀剂时得到的样品CoU和CoA堆积、团聚现象较为严重,而以六次甲基四胺为沉淀剂合成的样品CoH呈片状结构、分散性良好。采用循环伏安、恒电流充放电及交流阻抗等对材料的电化学性能进行研究表明:样品的放电时间、比电容、比电容剩余率从大到小顺序依次为CoH>CoA>CoU,即以六次甲基四胺为沉淀剂得到的氢氧化钴具有较好的电化学性能,这种结构可以显著地提高离子的扩散速率、电子的运输效率以及材料的导电性能。

The nano cobalt hydroxides were synthesized via hydrothermal method using cobalt nitrate as cobalt precursor,and the effect of precipitation agents on the morphology and structure of the obtained cobalt hydroxides and their electrochemical properties were studied.The morphology and structure of the materials were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD)and IR spectra,respectively.The results showed that serious surface accumulation occurred for the cobalt hydroxides CoU and CoA using urea and ammonia as precipitants respectively,but the sample CoH with hexamethylenetetramine as precipitating agent had the sheet structure and high dispersion.The electrochemical performance of the samples was analyzed by electrochemical tests such as cyclic voltammetry,galvanostatic charge and discharge and AC impedance.It can be seen that the discharging time,specific capacitance and capacitance retention of the samples were in the order of CoH>CoA>CoU.The sample CoH had excellent electrochemical performance,which significantly improved the diffusion rate of ions,the transport efficiency of electrons and the rate performance of electrode materials.