Study On The Effect Of Material Matching On Voltage Window Of Asymmetric Supercapacitor

Supercapacitors can provide ultra-high power and is widely used in various fields.Although it can meet the power requirements of hybrid vehicles,portable power tools,etc.as a green and environmentally friendly energy storage device,its relatively low energy density is still an important factor hindering its further development.Specific capacitance and potential window are important parameters for supercapacitors that directly affect the energy density and have received extensive attention,in recent years.In order to widening the voltage window,three aspects need to be focused:electrolyte solution,electrode materials and the matching of electrode materials.Among them,the research on the matching of electrode materials,especially for pesudocapacitor materials,is less studied.This paper intends to match the different pseudocapacitor negative electrodes with the prepared positive electrode material and explore the matching effect in voltage window.In addition,related research was conducted on the effect of work function difference on the potential window of the supercapacitor during the matching process.Following work were carried out for the above research purposes,in this thesis:Firstly,a high-performance nano-carbon@K_0.5Mn₂O₄ positive electrode was prepared by a simple in-situ redox method,Mo O₃,Fe₂O₃,V₂O₅,and WO₃ were selected as the matching negative electrode materials.The electrochemical test showed that the specific capacitance of positive electrode was about 300 F g^-1in a 1 M Na₂SO₄electrolyte solution(1 A g^-1).Meanwhile,the positive electrode also demonstrated a stable voltage window of up to 1.2 V.The four metal oxide anodes showed an approximate single-electrode potential window,about-0.2-0.9 V.Secondly,we assembled four asymmetric supercapacitor device by the nano-carbon@K_0.5Mn₂O₄ as positive electrode and four metal oxide as negative electrode respectively and investigated the energy storage performance.In the 1 M Na₂SO₄ electrolyte solution,carbon@K_0.5Mn₂O₄//Mo O3 presented the best performance,it’s power density achieved 66.7 Wh kg^-1 when the power density was5.95 k W kg^-1,and it showed the highest voltage window of 2.42 V.Finally,the influence of the work function difference between the two electrode materials on the potential window of the asymmetric supercapacitor during the matching process was also studied.We used the Kelvin probe force microscope to measure the work function difference between two materials.The study found that the greater the difference of the work function of the two pseudocapacitive electrodes,the larger the voltage window of the resulting device.