Study On Manganese Dioxide As Electrode Material For Electrochemical Capacitor In Organic Electrolyte

Manganese dioxide has been considered to be a promising electrode material for electrochemical supercapacitors in terms of its low cost , natural abundance, environmental friendliness and superior electrochemica1 performance. In this article, manganese dioxide was studied as electrode material for electrochemical supercapacitors in organic electrolyte. The reaction mechanism and their battery electrochemical performances were confirmed by the experiment of charge/discharge, CV and impedance analysis.Three samplesα-MnO₂ was synthesized by low temperature solidstate reaction, coprecipitation and sol-gel synthesis respectively. The special capacitance of each sample was 2.7Wh/kg , 4.7Wh/kg, 7.0 Wh/kg (500mA/g current density) in the electrolyte of 1mol/L LiPF₆/(EC+DEC+DMC)(1:1:1 Vol). After 200 cycles, the residual capacitance of each sample was 1.69 Wh/kg, 2.16 Wh/kg, 5.84 Wh/kg.The MnO₂ electrode prepared by coprecipitation showed high special capacitance and great cycle performance in the electrolyte of 1mol/L LiPF₆/(EC+DEC+DMC)(1:1:1 Vol). The electrochemical performance of MnO₂ electrode prepared by coprecipitation in the electrolyte of 1mol/L Et4NBF4/PC was not as good as expectation.The CV curves and charge-discharge curves showed graphite/nickel modified manganese dioxide can improve the electrochemical performance of capacitors.The special capacitance of each capacitor were 10.7 Wh/kg ,10.4Wh/kg(500mA/g current density), and after 1000 cycles the capacitance can keep 41%,56% respectively.The electrode polarization of the unsymmetrical supercapacitors was smaller than symmetrical ones, accordingly, the inner resistance of the unsymmetrical supercapacitors was smaller than symmetrical ones. The electrochemical performance of unsymmetrical supercapacitors was greatly improved, the special capacitance of unsymmetrical supercapacitor of graphite modified manganese dioxide can reach 31.3 Wh/kg. After 1000 cycles the capacitance can keep 77%.