Preparation Of Manganese Dioxide And Its Composites And Study On The Performance Of Supercapacitor

With the development of energy rising to the national strategic level,the task of developing and designing high performance energy storage devices with economic efficiency is imminent.Therefore,supercapacitors are developing rapidly.Manganese dioxide has been widely used in energy storage systems with high energy and power density because of its high theoretical capacity and good affinity.However,MnO2 electrode materials also face some challenges,such as low conductivity,crystal structure collapse caused by ion intercalation and deintercalation.Therefore,it is necessary to improve its intrinsic activity from the perspective of its intrinsic characteristics,or to construct specific structures and introduce high conductivity active substances on the nanoscale.In this paper,the performance of manganese dioxide and its composite supercapacitor is studied.(1)Using manganese chloride as manganese source,the bulk manganese dioxide was stripped to form nanosheets with the assistance of tetramethylammonium hydroxide.In order to explore the effect of morphology on electrochemical performance,manganese dioxide nanorods,nanospheres and hollow nanospheres were prepared with manganese sulfate and potassium permanganate as manganese sources.The results show that the MnO2 nanosheets with unique layered structure have excellent electrochemical properties compared with other materials.The specific capacity of MnO2 nanosheets reaches 96.5 F g-1,and the capacity retention rate reaches 77.3%after 2000 cycles.(2)The manganese dioxide nanorods composite with mesoporous carbon layer was prepared by combining the manganese dioxide nanorods synthesized in last work with dopamine hydrochloride and block copolymer.Due to the existence of mesoporous carbon layer,the specific capacity of MnO2 nanorods increased from 20.3 F g-1 to 78.5 F g-1,and the capacity retention rate reached 83.3%after 2000 cycles.In order to explore the growth mechanism of carbon layer,we study the effects of ammonia and mesitylene on the growth process of mesoporous nano unit,in condition of using the amount of ammonia and mesitylene as parameters.We obtain the best experimental conditions and hope to develop a general method of growing carbon layer.