The Influence Of Electrolyte On The Electrochemical Performance Of Manganese-based Electrode Materials

As well known,the basic structure of supercapacitors is mainly composed of electrode,electrolyte,diaphragm,collector and shell.Electrolyte,besides both electrode and diaphragm,is another important component in the basic structure because its behavior directly affects the electrochemical characteristics of supercapacitors.Therefore,nickel foam is regarded as the collector,electrochemical active MnO₂ as the basic material,and water-soluble electrolyte as the research object in our experiment.Manganese-based electrode materials for supercapacitor were prepared by mechanical cold pressing under 8 Mpa.Furthermore,the effects of Na₂SO₄ and KOH two electrolytes on the electrochemical properties of MnO₂ electrode materials were analyzed by the electrochemical workstation.Firstly,the electrochemical performance of Manganese-based electrode materials was measured in 1 M Na₂SO₄ neutral electrolyte.The energy storage mechanism and performance parameters of Manganese-based electrode materials were analyzed in the same electrolyte.The results indicate that the Manganese-based electrode materials show the coexistence of double-layer capacitance and continuous pseudo-constant rate redox reaction in 1 M Na₂SO₄ neutral electrolyte;the pseudo-capacitance AC impedance of the electrode materials has a frequency response characteristics;the specific capacitance of the electrode materials at current density of 2.5 mA/cm²is 121.08 F·g^-1,the energy density is 7.61 Wh·kg^-1,and the power density is 0.063 kW·kg^-1,respectively.Secondly,the electrochemical performance of Manganese-based electrode materials was also surveyed in 1 M KOH alkaline electrolyte.The energy storage mechanism of Manganese-based electrode materials in in the electrolyte was studied,and their performance parameters were calculated.The results indicate that Manganese-based electrode materials mainly exhibit the energy storage mechanism of continuous pseudo-constant rate redox reaction in 1 M KOH electrolyte,as well as the characteristics of double-layer capacitance;the AC impedance of pseudo-capacitance also has a specific frequency response characteristic;the specific capacitance of the electrode materials at current density of 2.5 mA/cm²is 96.35 F·g^-1,the energy density is 7.94 Wh·kg^-1,and the power density is 0.066 kW·kg^-1.Thirdly,based on the results of cyclic voltammetry,charge-discharge and AC impedance,the electrochemical properties of Manganese-based electrode materials were compared in 1 M Na₂SO₄ or KOH electrolytes.The results indicate that at different scanning rates,the specific capacitances of Manganese-based electrode materials in 1M KOH electrolyte are higher than those in 1 M Na₂SO₄ electrolyte;the specific energy density and specific power density at current density of 2.5 mA/cm²in 1 M KOH electrolyte are slightly higher than those in 1 M Na₂SO₄ electrolyte,while the specific capacitance in 1 M Na₂SO₄ electrolyte was higher than that in KOH electrolyte;The AC impedances of pseudocapacitor in 1 M Na₂SO₄ or 1 M KOH electrolytes have their specific frequency response characteristics.The pseudocapacitive AC impedance in the high frequency region is similar to the solution resistance R_S;the frequency pseudocapacitive impedance in the low frequency region in Na₂SO₄ electrolyte is slightly smaller than that in KOH electrolyte.