Carbon Nanotubes And Metal Hydroxide Composite As Electrode Material For Electrochemical Supercapacitor

Electrochemical supercapacitor (ES) is a promising new energy storage device. It has great potential application in aerospace; defense technology; digital communications system; electric vehicles; smart grid and so on. However, the furtherance of ES technologies still suffers from some challenges-including low energy density. high production cost and a higher self-discharge. It is great significance of studying the electrode materials, which is a key factor influencing the performance of supercapacitor. The various electrode materials developed can be categorized into three types:carbon materials, metal oxides/hydroxides and conducting polymer. Commercial ES today often use carbon materials and oxides/hydroxides as electrode materials because of the materials drawn rich, green and special motor storage management. At present, the researchers mainly put their efforts into improving the performance of electrode materials for supercapacitors In this paper, carbon nanotubes and Ni1/3Co1/3Mn1/3(OH)2composite electrode material as the research objects, Specific studies are as follows:(1) There are two effective methods to improve specific capacitance of carbon nanotubes. In the firstly method, A chemically CNTs were pretreated by purifying and introducing the surface functional groups to increase the capacitance performance.In this method. three different acid oxidation reagents were discussed.(HNO3-H2SO4(1:3,V/V); HNO3; H2O2-H2SO4(1:3,V/V)), The SEM, FT-IR, and electrochemical tests were indicated that HNO3-H2SO4(1:3,V/V) is the best oxidation reagents, the specific capacitances of carbon nanotubes was improved from28F g-1to85F g-1.Useing a redox-active electrolytes is another alternative route to improve the specific capacitance of CNTs. Which can induce the pseudocapacitance by the redox reaction of Q(quinone)/HQ(hydroquinone). In this paper the reaction mechanisms between redox-active and CNTs was established, and the effects of HQ concentration on carbon nanotubes electrode specific capacitances was also investigated, The results show that when the amount of HQ in1M H2SO4is0.075M, the specific capacitance increased as high as3199F g-1, and after500cycles, the specific capacitance can still be maintained at above76%. These indicate that the redox electrolyte displays a good cycle stability and a strong pseudo-capacitance characteristics. Thus, the above two methods may be great potential for improving the specific capacitance of CNTs.(2) In order to make full use of the advantages of nickel, cobalt, manganese hydroxide, Ni1/3Co1/3Mn1/3(OH)2was synthesized by chemical precipitation method for supercapacitors electrode material. Physical characterizations using XRD, EDX, and SEM show that Ni1/3Co1/3Mn1/3(OH)2possesses an amorphous structure and higher specific surface area (268.5m2g-1), which lead to high initial specific capacitance of1403F g-1, at the scan rate of1.0mV s-1. this material was more friendly to environment and economical than Ni0.37Co0.63(OH), but it showed poor cycling stability and rate performance due to the limited reaction rate concerned with manganese, the irreversibility and unstability of manganese redox reaction. For practical use of the composite Ni1/3Co1/3Mn1/3(OH)2material, further studies will be necessary to address the cycling stability and rate performance.