Preparation And Studies On Capacitance Performance Of Manganites And Doped Manganites

Supercapacitors, regarded as energy storage components developed in the 1970′s, when work with batteries, could meet the high power output need of electric vehicles when starting-up or speeding up because their power density could be ten times higher than that of batteries and their energy density could be ten times higher than that of electrostatic capacitors, and it had exhibited some special features, such as the speed of charging-discharging was quickly, it did not pollute our environment, the cycle life was long, so it was hopeful to become the new green energy in the 21th century. In the development process of supercapacitor, the choice of electrode materials was regarded to be one of the most important parts. In recent years, the researcher gradually paid their attention to the research of complex oxides and hydroxides of Ni, Co and Mn and had obtained some good research results. In our research , K_0.27MnO₂·0.6H₂O was synthesized by sol-gel method and high temperature solid phase method, and through the method of doping, the potassiumion was doped into the complex hydroxides of Ni, Co and Mn and the doped complex oxides of Ni, Co and Mn was obtained. Main points of our research are listed as below:(1) Synthesis of K_0.27MnO₂·0.6H₂O and the characteristic of the structure and the performance of K_0.27MnO₂·0.6H₂O: K_0.27MnO₂·0.6H₂O was synthesized by sol-gel method and high temperature solid phase method, XRD and SEM techniques were used to characterize the morphology and the structure of the as-prepared samples. The results indicated that the both samples synthesized by sol-gel method and high temperature solid phase method exhibited layer structure and the diameter of particles of the samples synthesized by sol-gel method was smaller than the diameter of particles of the samples synthesized by high temperature solid phase method. The electrochemical performance of the as-prepared samples was characterized by cyclic voltammetry and galvanostatic charge/discharge test. The results showed that the both samples had the typical capacitance performance and could be regarded as the ideal electrode materials of supercapacitors. The discharge specific capacitance of the samples synthesized by sol-gel method was higher and the cycle performance of the samples synthesized by sol-gel method was better.(2) The study on electrochemical capacitance performance of the electrode materials synthesized by potassiumion doped 1/2MnOOH·1/2Ni(OH)₂ and Ni_1/3Co_1/3Mn_1/3OOH: the precursor 1/2MnOOH·1/2Ni(OH)₂ and Ni_1/3Co_1/3Mn_1/3OOH were synthesized by co-precipitation method. The doped complex oxides of Ni, Co and Mn was prepared by mixing 1/2MnOOH·1/2Ni(OH)₂ and Ni_1/3Co_1/3Mn_1/3OOH and K2CO3 according to certain mixing ratio respectively, following by calcining at high temperature, then washing the materials several times with water to remove residual K2CO3 and drying. XRD and SEM techniques were used to characterize the morphology and the structure of the two kinds of as-prepared samples. The results indicated that the structure of the two kinds of samples resembled to the layer structure of K_0.27MnO₂·0.6H₂O. The results of cyclic voltammetry and galvanostatic charge/discharge test showed that the two kinds of samples had the capacitance performance and the CV curves obtained at low scan rates showed good rectangular features.