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MnO2 Prepared By Electrochemical Deposition For Supercapacitor Applications

Posted on:2019-06-12Degree:MasterType:Thesis
Country:ChinaCandidate:F QianFull Text:PDF
GTID:2382330566484277Subject:Energy and chemical
Abstract/Summary:PDF Full Text Request
With the rapid development of the economy,the environmental pollution and depletion of fossil energy have attracted a lot of public attention.The research and development of green,safe and efficient energy storage device is urgent.As a new type of energy storage device,supercapacitor has the advantages of long service life,short charging time and good temperature characteristics and so on.In general,the pseudo capacitor has a higher capacity than the double layer capacitor.As transition metal oxide MnO2 has a lot of advantages.Such as abundant reserves,low costs,no pollution to the environment and high theoretical specific capacity.So MnO2 is a valuable electrode material for supercapacitor.Due to its low electrical conductivity,the specific capacity of MnO2 can't be fully discharged in the electrochemical reaction.In order to improve the conductivity of MnO2electrode materials,in this paper,electrochemical deposition method was used to prepare MnO2electrodes directly,without using any binder,conductive additives,or slurry-coating procedures.After that,the utilization of MnO2 was improved and its capacitance behavior was optimized.The main contents and results of this paper are as follows:?1?Manganese sulfate was selected as manganese precursor.MnO2/carbon paper hybrid electrodes were prepared by anodic constant current density electrochemical deposition,and the influences of deposition time,deposition current density and deposition temperature were investigated.It is found that the shorter the deposition time is,the less the amount of deposition is,the better the conductivity and the specific capacity are.When the deposition current density is 5 mA cm-2,the dense lamellar MnO2 which is beneficial to the diffusion of electrolyte is obtained.The specific capacity of the electrode was decreased with the increase of deposition temperature,so 25?was selected as the optimal deposition temperature.Adding different support cations to the deposition solution can improve the two-dimensional tunneling structure of MnO2 and increase the amount of its pseudo capacitance active sites.We found that supporting cation--potassium ions can effectively improve the specific capacity of the electrode materials.MnO2/CNT/MnO2/CP,a kind of layer structure material was prepared by adding CNT to the pre-electrode material via the dipping-drying method,which effectively reduced the resistance of the electrode,and the highest specific capacity of the electrode can reach about327.5 F g-1.?2?A kind of high specific surface area mesoporous carbon with large pore volume was synthesized via hard template method.This kind of carbon was used as the deposition substrate for MnO2 electrochemical deposition.The electrochemical tests were working with three electrodes.The following results were obtained:Firstly,the longer the deposition time is,the higher the sediment quality and the lower the specific capacity of the electrode.Secondly,MnO2/CNT/MnO2/PC/FN,the layer structure material was made by dipping–drying method.The conductivity of the electrode was improved in a certain extent,but as for the electrolyte diffusion was blocked,the overall specific capacity of the hybrid electrode was not obviously improved.Doping Ni2+in MnO2 electrode can increase the electrical conductivity as well as the specific capacity.The specific capacity of the electrode can reach 497.5 F g-1.When the mass loading is about 0.75 mg cm-2.At last,different carbonization temperatures were used to prepare the high surface area,large pore volume mesoporous carbon.The maximum specific capacity of the electrode can get was 534.4 F g-1 as we used the porous carbon which was prepared by the carbonization temperature of 1200 centigrade to act as deposition substrate.
Keywords/Search Tags:Electrodeposition, MnO2, Carbon paper, Layer structure material, Supercapacitor
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