熔盐法合成MnO2粉体及其超级电容性能

采用熔盐法在不同温度下制备了MnO2粉体.X射线衍射仪分析表明:粉体样品为α-MnO2和γ-MnO2晶混合物,反应温度越高样品的结晶程度越好.将MnO2粉体与石墨、乙炔黑、聚四氟乙烯、羧甲基纤维素按质量比为75:10:10:2:3进行混合,在10 MPa压力下压制成电极.在2 mol/L (NH4)2SO4溶液中,用三电极体系对MnO2电极样品进行电化学性能测试.结果表明:制备粉体的反应温度是影响MnO2粉体制备的电极的电化学性能的重要因素,反应温度为450 ℃的粉体制备的电极样品电容性能最好.循环伏安测试表明该样品在0～1.0 V电位窗口范围内具有较好的矩形特征;交流阻抗测试结果显示样品具有典型的电容阻抗特性,其等效串联电阻和电极反应电阻分别为0.064 Ω和2.825 Ω.在电流密度为2 mA/cm2,恒流充放电时测得其放电比容量可达246.46 F/g.

SYNTHESIS OF MnO2 POWDER BY MOLTEN SALT METHOD AND ITS SUPERCAPACITOR

MnO2 powders were prepared by the molten salt method at different temperatures. X-ray diffraction results indicate that the MnO2 powders consist of α-MnO2 and γ-MnO2. Moreover, the crystallinity of MnO2 powder becomes higher with the increasing of reaction temperature. An experimental electrode was prepared by mixing MnO2 with graphite, acetylene black, polytetrafluoroethylene and carboxymethyl cellulose at a mass ratio of 75:10:10:2:3, and pressed under 10 MPa. The electrochemical properties of the electrode were measured by a three-electrode system in 2 mol/L (NH4)2SO4 solution. The results show that the supercapacitor performance of the electrode sample with MnO2 powder is greatly affected by the reaction temperature of MnO2 preparation. The sample with the MnO2 powder prepared at 450 ℃ has the best supercapacitor performance. The results of cyclic voltampere curves show that the sample represents rectangular shape performance in the potential range of 0-1.0 V. Alternating current impedance measurement shows that the sample has typical capacity impedance characterization; its equivalent series resistance is 0.064 Ω and the electrode reaction resistance is 2.825 Ω. When charged and discharged at a constant current of 2 mA/cm2, the discharge specific capacity of the MnO2 electrode sample can reach 246.46 F/g.