【作者】 王晓芳；

【导师】 刘伟；

【作者基本信息】 大连理工大学 ， 化学工程， 2012， 硕士

【摘要】 贵金属Ru02作为超级电容器电极材料,电化学性能良好,比容量高。但由于其价格昂贵,准电容器的应用受到了很大限制。MnO2资源丰富,价格低廉且其电容性能与Ru02等贵金属相似,是最有可能取代RuO2的廉价金属氧化物。本文采用XRD、 SEM和电化学测试等方法对合成的镍/碳复合体和改性MnO2材料进行表征,主要内容如下：共沉淀法合成镍/碳前驱体,在600℃下热处理得到镍/碳复合体,其电化学稳定性能比较好,比容量较大,可逆性好。在25.5°时出现石墨峰,随着温度的升高,峰变得尖锐,复合体颗粒的尺寸在0.5-2μm之间,分散性良好。随着K2CO3量的变化,复合体的比容量呈现先增加后减小的趋势；在量为0.5g时,循环伏安曲线的感应电流较大,扫描面积最大,比容量较大。恒电流充放电过程中,随着电流密度的增大,比容量呈减小趋势,材料充放电性能好,内阻较小,在电流密度为0.5A/g时,电极比容量仍可达90F/g。羧甲基纤维素可以使前驱体溶液分散均匀,反应充分接触,有利于电极材料保持高比容量、循环稳定性和良好的电化学性。以KMnO4和MnCl2-4H2O为前驱体,采用共沉淀法合成纳米结构MnO2电极材料。添加一定量的FeCl3-6H2O对Mn02进行改性。通过X射线衍射(XRD)、扫描电子显微镜(SEM)等方法对MnO2的结构和形貌进行表征；利用循环伏安法、恒流充放电等测试方法研究了Mn02电极材料在lmol/L KOH电解液中的电化学行为。结果表明,FeCl3-6H2O大大影响Mn02的结构和形貌。随着Fe:Mn摩尔比的增加,MnO2从7-Mn02晶型转变为层状结构,形貌由片状转变为直径约100nm的球形,并且Fe改性MnO：的电化学性能明显提高。当添加FeCl3-6H2O的量为5%(Fe与Mn的摩尔比)时,在1A/g电流密度下,Mn02电极的比容量为279F/g。通过液相共沉淀反应,添加硫酸亚铁铵[Fe(NH4)2(SO4)2-6H2O]改性合成MnO2材料。随着硫酸亚铁铵添加量的增加,XRD和SEM测试表明,材料的晶型由y-MnO2变为a-Mno2；形貌由片状和棒状的混合结构逐渐变为纳米棒状,平均粒径为75nm左右,长度为0.8-2μm。电化学测试表明,随着反应时间的变化,材料比容量先增大后减小,以样品添加量为10%,回流时间1h时的比容量最大,在电流密度为1A/g下,比容量仍可达247F/g。更多还原

【Abstract】 As supercapacitor electrode material, RuO2has high capacity and good electrochemical performance. For its high cost, the application of supercapacitor is extremely restricted. In view of rich resource and extremely similar capacitance to noble metals such as RuO2, MnO2is the cheapest metal oxides to replace RuO2. In this thesis, nickel/carbon composites and Fe-modified MnO2were characterized by XRD and SEM, their electrochemical performance was also investigated. The main results are as follows:Nickel/carbon composites with large capacity and good electrochemical reversibility were prepared by heat treatment of the composite precursors at the temperature of600°C. Graphite peak occurred at25.5°, and became more and more intense with the increase of temperature. The Ni particles with good dispersion have the sizes of0.5~2μm. With increasing the amount of K2CO3, the specific capacitance of the composites increased first and then decreased. In the case of using0.5g of K2CO3, the prepared sample showed the largest inductive current-voltage curve and scanning area, suggesting the highest specific capacitance. In the process of constant current charging and discharging, the specific capacitance showed the trend of decrease with the increase of current density. The capacitance of electrode can reach to90F/g at the current density of0.5A/g. The use of carboxymethyl cellulose could make the composite precursor well dispersed, which is helpful to improve the electrochemical capacity and stability.Nanostructured manganese dioxide (MnO2) was synthesized using a simple co-precipitation method wherein potassium permanganate and tetrahydrate manganese chloride were used as precursors. Certain amount of FeCL3-6H2O was introduced during the preparation process for the modification of MnO2. The structure and morphology of MNO2were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The capacitive behaviors of MnO2were studied by cyclic voltammetry (CV) and galvanostatic charge-diacharge in1mol/L KOH electrolyte. The results showed that the addition of FeCl3-6H2O significantly influenced the structure and morphology of MnO2. With increasing the molar ratio of Fe to Mn, MnO2changed from y-phase into layered structure. And the morphology of MnO2changed from flake into sphere whose diameter is about100nm. Significant enhancement of electrochemical performance was observed for the Fe-modified MnO2. The MnO2which was obtained with5%(the molar ratio of Fe to Mn) FeCl3-6H2O showed the specific capacitance of279F/g at a current density of1A/g.Ammonium ferrous sulphate was also used to modify MnO2through the liquid precipitation reaction. With increasing the amount of ammonium ferrous sulphate, XRD and SEM results showed that the crystal changed from y-MnO2into a-MnO2. And the morphology changed from the mixed structure of sheets and nanorods into nanorods, the average particle size is about75nm, length is0.8~2μm. Electrochemical tests showed that the specific capacitance increased first and then decreased along with the reaction time. When the amount is10%and the reaction time is1h, the specific capacitance still could reach to247F/g at a current density of1A/g.更多还原