Preparation And Electrochemical Properties Of Nano-Cobalt-Iron Composites

With the increasingly important position of energy in modern society,the development and progress of energy storage technology have been highly valued by governments and enterprises in various countries.Some traditional energy storage technologies are no longer suitable for the current high-capacity and large-scale energy storage demand.As a new energy storage device with high safety,high stability,high specific capacity,and high specific power,supercapacitors occupy an important position in various energy storage related fields.Electrode materials are the core components of supercapacitors,and only by developing electrode materials with better performance and easier preparation can we satisfy the increasing energy demand.The cobalt-based and iron-based oxide materials in metal oxide electrode materials have become the focus of researchers in recent years due to their excellent electrochemical performance potential,low cost,and other advantages.In this thesis,the composite materials of cobalt-based and iron-based oxide materials and reduced graphene oxide（rGO）were studied respectively.On this basis,the composite material formed by Co₃O₄ nanowires and Fe₂O₃ nanospheres based on rGO substrate was successfully prepared,and its morphology and electrochemical performance were tested and analyzed.The final product of this thesis is rGO/Co₃O₄@Fe₂O₃ material,and the contents are divided into three parts shown as follows.1.Graphene oxide（GO）was prepared by the modified Hummers method,and the subsequently required rGO was prepared by thermal reduction modification using PSS.The cobalt-based rGO/Co₃O₄ nanowire materials were prepared by hydrothermal synthesis method,and the effects of different cobalt chloride dosage ratios on the material properties were comparatively investigated.It was found that the obtained materials with1 mmol of cobalt chloride dosage showed the optimal performance,with the specific capacity of 672.31 F/g at 1 A/g current density,and the rate performance was also higher than the materials with other dosages.2.Iron-based rGO/Fe₂O₃ nanospheres were prepared by hydrothermal synthesis method.The effects of different ratios of ferric chloride on the performance of the materials were investigated comparatively.It was found that the specific capacitance of the materials obtained with 1 mmol and 1.5 mmol ferric chloride at the current density of1 A/g was close,but the material with 1 mmol ferric chloride had higher rate performance.3.The rGO/Co₃O₄@Fe₂O₃ composite material was prepared by in-situ hydrothermal synthesis method with the rGO/Co₃O₄ material prepared by the optimal amount of cobalt chloride as the precursor and the optimal amount of ferric chloride as the additive.The performance of the rGO/Co₃O₄@Fe₂O₃ composite material was compared with those of single cobalt-based and iron-based nanomaterials alone,and the mixture material prepared by directly mixing cobalt chloride and ferric chloride without using precursor material.The rGO/Co₃O₄@Fe₂O₃ composite material exhibited the highest specific capacitance of 784.31 F/g at the current density of 1 A/g,and the specific capacitance could still reach 661.54 F/g when the current density was increased to 10 A/g.The rate performance of the rGO/Co₃O₄@Fe₂O₃ composite material was much higher than the other three materials,and the capacity retention rate of 84.7%after 1000 cycles of charge and discharge was also better than others.The overall electrochemical performance of the composite material had been significantly improved.