Research Of The Preparation And Electrochemical Properties Of The Transition Metal Oxides

The two of major energy storage equipments are lithium ion batteries and supercapacitors, which property strongly depend on the continuously improve and explore of their electrode materials performance. Carbon materials are the main anode materials in the common commercialized energy storage equipments, especially the lithium ion batteries. But the theoretical specific capacity of carbon materials is very low, can’t meet the need of equipments for high energy and power density. It’s necessary seriously to seek for new-type anode candidates as substitution of carbon materials. Due to the theoretical specific capacity is quite high, the safety is very well, the cycle ability is fairly stable, the transition metal oxides, especially NiO and CoO, obtain more and more attention from the researchers. However, the metal oxide anode materials for lithium ion batteries and supercapacitors suffer from poor conductivity and instability structure in the process of charging and discharging. In this thesis, we synthesis NiO and CoO. Then we make the target materials into anode materials of lithium ion batteries and supercapacitors respectively. Our main aim is to enhance its conductivity and volume deformation resistance by changing the structure and morphology of anode materials, which could improve the cycle stability performance, rate performance and capacitance performance of the electrode material, further increase the energy density and power density of anode materials for lithium ion batteries and supercapacitors. Do the main work is as follows:(1) Through a simple hydrothermal method and the subsequent calcination process, we synthesis NiO nanosheets by using of Ni(CHO3CO)2·4H2O, CO(NH2)2,(HOCH2CH2)3N as raw material. The electrochemical tests demonstrate the superior electrochemical performance of the NiO nanosheets. The good performance, including large specific capacitance (the initial discharge and charge capacities are1827.7mAh/g and1267.5mAh/g respectively), high reversible capacity(the reversible capacity is about560.0mAh/g after50cycles at400mA/g) and excellent cycle ability (the specific capacitances are as high as1092.8F/g and804.8F/g at4A/g and8A/g, and the specific capacitance retention ratio is about70.8%after3000cycles at16A/g) has been measured.(2) Through a simple hydrothermal method and the subsequent calcination process, we synthesis urchin-like micro/nano NiO pheres by using of Ni(CHO3CO)2·4H2O, C12H25SO3Na,(CH2OH)2as raw material. When applied as the anode materials of lithium ion batteries, the urchin-like NiO micro/nano spheres demonstrate superior electrochemical performance, with high capacitance, superior rate performance and enhanced cycle performance. On the other hand, when applied as the anode materials of supercapacitors, the urchin-like NiO micro/nano spheres demonstrate superior electrochemical performance, with superior rate performance, enhanced cycle performance. At the current density of12F/g, the corresponding specific capacity of the urchin-like NiO micro/nano spheres is347.4F/g, the capacity retention of the3000th cycle is75.9%(relative to the capacitythe of1600th’).(3) We have synthesized micro-/nano-structured CoO powders with different morphologies (cube, sphere and spindle). By heating treatment, they exhibit highly-porous structures. By testing with electrochemical measurements, all of them possess excellent initial discharge capacities (1194.4mAh/g,1208.5mAh/g and1248.7mAh/g at0.8A/g), meanwhile the spindle CoO electrode exhibits the best rate capability (the discharge capacity retention ratios at0.8A/g after50cycles and at1.6A/g after30cycles are87.3%and77.7%).