Preparation And Investigation Of MnOx As Electrode Material For Supercapacitor

Supercapacitors are promising energy storage devices that bridge the gap between batteries and conventional capacitors.They exhibit a promising set of features such as high power density,fast rates of charge-discharge,reliable cycling life,and safe operation.Supercapacitors can be divided into double layer capacitor（EDLC）and pseudocapacitor.Among various candidates for pseudocapacitive materials,manganese oxide（MnOx）,have gained much attention due to their low cost,environmental friendliness,natural abundance and high theoretical specific capacitance,which make it the most promising electrode material for next generation supercapacitors.It is still a challenge to design and synthesize high-performance MnOx electrode materials with high specific capacitance.In this work,MnO₂ and Mn₃O₄ electrode materials are successfully prepared by different methods.The main contents are as follows:（1）By applying potassium permanganate as the source of manganese,the flower likeδ-MnO₂ was successfully prepared by hydrothermal method,and then carried the following low temperature calcination to produce calcinedδ-MnO₂.The influence of hydrothermal reaction time on morphology,crystallinity,surface area and electrochemical properties of the products were systematically investigated.The experimental results revealed that the crystallinity of theδ-MnO₂increases with increase of the hydrothermal time.The sample obtained at 300°C showed the highest specific capacitance of 264 F/g at 0.1 A/g.Further increasing heat treatment temperature led to collapse of flower structure,which resulted in the decrease of the specific capacitance.（2）At first,by using glucose as carbon source,monodispersed carbon nanospheres were prepared by hydrothermal reaction method,which were then applied as the template to in-situ grow MnOx to produce core-shell CSs@MnOx structure.After heat treatment under air and argon atmosphere,hollow Mn₃O₄nanosphere and core-shell CSs@Mn₃O₄ nanospheres are prepared,respectively.The experimental results showed that core-shell C@Mn₃O₄ nanospheres exhibited the best electro-chemical performance.The specific capacitance of core-shell Mn₃O₄ nanospheres is as high as 307 F/g,and specific capacitance could remain at 92.8%after 5000 constant charge-discharge cycle.