Preparation and Application of MnO2 in Electrochemical Capacitors
MnO2的制备及其在电化学电容器中的应用

Two chemical manganese oxides were synthesized by oxidation of Mn(NO3)2 salts with KMnO4 under different pH values. The crystal structure and crystal pattern were characterized by mean of X-ray diffraction and X-ray scan microscope, which demonstrated that pH values determined the formation of crystal structure. The electrochemical performance of the two materials was studied by cycling voltammetry in the range -0.3-0.6 V (Hg/HgO), which indicated their capacitive behaviors. Comparison of capacitor with activated carbon as electrode material constructing asymmetric configuration to that with MnO2 constructing symmetric configuration, showed that both working voltage and specific capacitance of hybrid capacitors were increased. Galvanostatic charge/ discharge indicated that the specific capacitance of symmetry structure of electrochemical capacitor were 262 and 302 F/g, respectively, and those of asymmetry structure of electrochemical capacitor were 348 and 342 F/g, respectively. These materials possess better capability of high current discharge and cyclicity.