MnO2電化學電容製程與特性研究

Abstract

本研究係以CMD(chemical manganese dioxide)及EMD（electrolytic manganese dioxide）兩種方法，製作MnO2電化學電容的電極，並藉CV（cyclic voltammetry）及CCD（constant current discharge）等測試方式，驗證電極的電容特性與比電容的大小。 實驗結果顯示：以EMD方式形成的電極具較佳的電容特性與比電容大小，在0.1M的Na2SO4水溶液中，操作電壓為0.0-0.7V（AgCl），最高比電容為465.6F/g，於測試1500次後，電極仍展現很好的穩定性，其衰退率不超過4.7﹪。 在製程的討論中，導入陽離子空位（cation vacancy）的理論，由此一理論可合理地解釋EMD製程中，主要影響電容特性的控制因子是結晶水含量。在其他與結晶結構無關的條件固定下（如粒徑分佈、孔隙等因子），適當的結晶水含量會產生最佳的電容表現。

In this study the MnO2 electrodes were prepared by CMD（chemical manganese dioxide）and EMD（electrolytic manganese dioxide）.The performance of these electrodes as electrochemical-capacitor was studied by cyclic voltammetry（CV）and by constant current discharge（CCD）. The electrodes prepared by EMD exhibited better capacitive characteristics and specific capacitance than these prepared by CMD.The working voltage was in the range 0.0-0.7V（AgCl）in 0.1M Na2SO4 solution. The specific capacitance was 465.6F/g and exhibited good cycling stability.After 1500 cycles,the specific capacitance lost not more than 4.7﹪. Cation vacancies model may interpret reasonably the water content is the main factor in the EMD process,which influence the electrochemical reactivity. An optimum water content of EMD exhibited a better capacitive performance when other factors ,such as particle size distribution,porosity..etc.,was the same