Study Of MnO₂and MnO₂/Graphene As Electrodes Material For Supercapacitor

Supercapacitor is a novel energy storage device between batteries and electrolyticcapacitors，which has higher energy density than that of electrolytic capacitor and higherpower density than that of batteries. They can meet the requirement of high powerout-put, such as electric vehicles starting-up or accelerating. According to the principle ofenergy-storage, there are two types of supercapacitors: electric double-layer capacitorand faradalc pseudocapacitor. Electrode material mainly includes carbon material,conducting polymer and metal oxide.In this paper manganese dioxide (MnO2), MnO2/graphene composite were producedas the supercapacitor electrode material by hydrothermal method. The physical andelectrochemical test methods such as XRD， SEM, BET, CV, constant currentcharge-discharge were employed to investigate their structure and electrochemicalperformance．The main results are the following:The optional conditions to produce MnO2reacting temperature140℃and reactingtime9hours. SEM image showed that the grain particle comes in form of diameter40~60nm. Its specific surface area as large as60.17m2/g. The specific capacity is90F/gand still reach82F/g though after50cycles. The capacity retention ratio is91.11%.The MnO2/graphene oxide composites synthesized by hydrothermal reactionbetwene oxidized graphene and KMnO4. SEM showed that the particle comes in shape ofmulti-hole honeycomb with diameter40nm and specific surface area70.91m2/g. Thespecific capacity of MnO2/graphene oxide is158.3F/g and still reach156F/g after50cycles. The capacity retention ratio is98.55％.The MnO2/graphene composites were produced by Modified Hummers method andhydrothermal method. SEM showed that the particle comes in shape of multi-holehoneycomb with diameter of10~20nm and specific surface area85.51m2/g. Thespecific capacity is192.5F/g and still reach190F/g after50cycles. The capacity retention ratio is98.70％.The composite material with porous structure and a largespecific surface area and good electrochemical properties. It can be used as electrodematerial for supercapacitor.