铋改性二氧化锰在电化学电容器中的应用

Application of Bi_2O_3 coated MnO_2 in electrochemical capacitors

采用液相沉淀法合成二氧化锰并在其表面包覆氧化铋,以期改善二氧化锰的电容性能。X射线衍射(XRD)测试表明合成的二氧化锰为无定形结构,包覆Bi2O3后材料转变为结晶度较差的α-Mn O2;扫描电镜(SEM)和X射线能谱(EDX)测试结果显示其为无规则颗粒状且表面覆盖着疏松的Bi2O3。循环伏安、恒电流充放电和电化学阻抗谱测试表明包覆5%(质量分数)Bi2O3的二氧化锰具有最好的电容性能。在电流密度分别为200、400和600 m A/g时,电极比电容分别为352.8、307.2和277.2 F/g,相比未包覆Mn O2分别提高了17.1%、15.0%和9.5%。

In order to improve the capacitors performance of manganese dioxide, manganese dioxide was prepared by a liquid phase precipitation method and then Bi2O3 was coated on its surface. The results of X-ray diffraction test indicate that the synthesized manganese dioxide is amorphous; while being coated with Bi2O3, it is converted into poor crystal α-MnO2. The results of scanning electron microscope and X-ray energy dispersive test show that its particles are irregular and the surface is covered with loose Bi203. The results of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectrometry test indicate that manganese dioxide coated with 5wt% Bi2O3 has the best capacity; its specific capacitance reaches to 352.8, 307.2 and 277.2 F/g when charging/discharging at 200, 400 and 600 mA/g, respectively, increasing by 17.1%, 15.0% and 9.5% than the uncoated one, respectively.