混合价态锰氧化物(MnO_x)的合成及其电容性能研究

Synthesis and Capacitive Properties of Manganese Oxides (MnO_x)

本文以高锰酸钾和尿素为原料,在pH=1的酸性条件下,采用水热法和沉淀法分别合成了混合价态的1#MnOx和2#MnOx.利用XRD、SEM和XPS对样品的结构、形貌和锰元素价态进行了分析.以MnOx电极为正极,活性炭(AC)电极为负极,组装成模拟非对称超级电容器AC/MnOx,通过循环伏安法和恒流充放电法测试其电容性能.电化学测试结果表明,1#MnOx的电容性能优于2#MnOx.在1 mol·L-1Li2SO4电解液中,电流密度为200 mA·g-1和工作电压为(0～1.5)V时,AC/1#MnOx和AC/2#MnOx非对称电容器的初始比电容分别为30.96和26.56F·g-1.1000次循环之后,AC/1#MnOx和AC/2#MnOx的比电容都只下降了6.5%.

1#MnO, and 2#MnOx samples with hybrid valences were synthesized by hydrothermal method and precipitation method respectively, with starting materials of KMnO4 and urea. Their structure, morphology and valence state of Mn were analyzed by X-ray diffraction （ XRD）, scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. The MnOx and activated carbon （AC） electrode were used as the positive and negative electrode in asymmetric supercapacitors＇ whose capacitive properties were determined by cyclic vohammetry and galvanostatic charge-discharge test in 1 mol · L -1 Li2SO4 aqueous solution. The results showed the capacitive performance of 1#MnOx was better than that of 2#MnOx. In the potential range of （0 - 1.5） V, the AC/1#MnOx and AC/2#MnO, asymmetric capacitors delivered the initial specific capacitance of 30.96 and 26.56 F · g-1 （ based on the total active mass of two electrodes）, respectively, at a current density of 200 mA · g-1 in Li2SO4 solution. After 1000 cycles, the specific capacitance of both AC/1#MnOx and AC/2#MnOx declined about 6.5%.