| Supercapacitors have been recognized as unique energy storage devices which have higher energy density than conventional capacitors, and higher power density and longer cycle life than batteries, filling the gap between conventional dielectric capacitors and batteries. They can release large discharge current instantly. Based on the above, the promising application of supercapacitors in the fields such as mobile telecommunication, information technology, consumer electronics, electric vehicle, aviation&aerospace, and military force, have been attracting more and more attention throughout the world.Studies on supercapacitors are mainly focused on the preparation of high performance electrode material and electrode. Manganese oxides have drown much attention due to their low cost, abundance, wide electrochemical window, various oxidation value states and less harmful nature, which have been considered to be a promising electrode material for supercapacitors. Manganese oxides can be prepared by chemical and electrochemical methods. Some of methods, however, exist some disadvantages, such as high energy consumption, complicated reaction technology, rigorous to conditions, low productivity and selectivity, etc. Chemical precipitation method exhibits many advantages: low energy consumption, simple reaction technology, controllable to conditions, high productivity and selectivity and so on. This method has been established as effective in the preparation of manganese oxides. However, the studies on the aspect also exist some shortcomings, mainly embodying that the manganese oxides prepared by the method have low specific capacitance and are poor in cycle life, which limited their application on supercapacitors.In our work, we choosed manganese oxides as the object of studies, adopted chemical precipitation method to prepare manganese oxide based materials and characterized their structures and electrochemical properties and drawed a conclusion. The main results are as follows:Firstly, manganese oxide prepared by chemical precipitation method. We optimized the technology of the preparation and emphasized the influence of the pH value of the system and heat treatment on the structure and electrochemical performance of the products. SEM, XRD, TG-DTA, CV, EIS and galvanostatic charge/discharge measurements were employed to investigate the structure and electrochemical performance of the materials. It demonstrated that pH value of the system and heat treatment had large effect on the the structure and electrochemical performance of the products. The materials prepared in weak acidic system showed a better crystalline phase and electrochemical stability but smaller specific capacitance compared to a weaker crystalline phase and electrochemical stability but a bigger specific capacitance of the materials prepared in weak basic system. The heat treatment could promote the degree of crystallizing and electrochemical performance of the materials prepared in both system. Based on the results, the material prepared in weak acidic system with the heat treatment had a better electrochemical performance, which showed a maximum specific capacitance of 266F·g-1 in 6mol·L-1KOH electrolyte at the scan rate of 5mV·s-1, which is 10.4-77.3% higer than that of manganese oxide electrode (150-250F·g-1) prepared by the similar method reported in the literature. Moreover, the electrode showed high electrochemical stability and a long cycle life indicating a promising material for supercapacitors.Secondly, We prepared manganese oxide based composite materials by chemical precipitation method on the basis of manganese oxide. Also we optimized the technology of the preparation and emphasized the influence of the ratio on the structure and electrochemical performance of the products. SEM, XRD, CV, EIS and galvanostatic charge/discharge measurements were employed to investigate the structure and electrochemical performance of the materials. The results showed that the introduction of a proper proportion of either acetylene black or nickel oxide into manganese oxide could promote electrochemical performance of the composite electrodes. For the manganese oxide/acetylene black composite electrodes, when the loading amount of acetylene black was 30wt.%, the composite electrodes showed a promising specific capacitance of 240F·g-1 in 6mol·L-1KOH electrolyte at the scan rate of 5mV·s-1, which is 4.3-50.0% higer than that of most of the manganese oxide/carbon composite electrodes (160-230F·g-1) reported in the literature. Moreover, the composite electrodes exhibited high electrochemical stability and a long cycle life, the specific capacitance of the composite electrodes only had 2.1% loss after 500 cycles. For the manganese oxide/nickel oxide composite electrodes, when the loading amount of nickel oxide was 20wt.%, the highest specific capacitance of the composite electrodes was up to 465.8F·g-1 in 6mol·L-1 KOH electrolyte at the scan rate of 5mV·s-1, which is 17.0% higher than pure manganese oxide electrode (398.1F·g-1). Moreover, the composite electrodes showed high power density and stable electrochemical properties. The results indicated that the two kinds of composite materials are suitable for supercapacitors.
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