Research On Manganese Oxide And Polyaniline Composite As Electrode Materials

Supercapacitor as a new type of energy storage device, is an electrochemicaldevice that energy storage through polarization electrolye. Manganese dioxideelectrode materials with high theoretical specific capacity, abundant reserves, lowprice, friendly to the environment, etc. become one of the research hotspots. In thispaper, MnO2powders were prepared by the liquid-phase coprecipitation method, andpolyaniline/MnO2composites were prepared to improve the performance of thematerials. The main results are as follows:Based on the ion response equation of2MnO4-+3Mn2++2H2Oâ†'5MnO2+4H+,MnO2powders have been synthesized by the liquid-phase coprecipitation method.The structure and electrochemical performance of MnO2powders under the conditionof different temperatures and various kinds of acid have been analyzed. Theexperimental results show that the higher temperature, the better crystallinity of MnO2powders. Under free acid and reaction temperature below85℃, crystalline manganeseoxide is γ-MnO2, while hollandite is generated at85℃. However,γ-MnO2phaseexists until at85℃, when strong acid were used. It result from strong acid inhibitedthe formation of hollandite. The electrochemical properties of MnO2powdersdecreases with increase of the reaction temperature, and the electrochemicalperformance of MnO2powders prepared in strongly acidic conditions is better thanthe MnO2powders prepared in no acid or acetic acidic conditions. The specificcapacitance of MnO2powders prepared in HCl and H2SO4at25℃achieved303F/gand308F/g, respectively.PANI/MnO2composites were synthesized via two-steps synthesis andsimultaneous-oxidation route, respectively. The electrochemical performance ofMnO2/PANI composites prepared by two-steps synthesis enhanced with the increaseof the content of MnO2. So MnO2plays an important role in the composite material.When the reaction concentration of KMnO4was30mmol/L, the specific capacitanceof the composites reached281F/g. The electrochemical performance of thecomposites was better than polyaniline’s, but poor than MnO2powders prepared byliquid-phase coprecipitation methods. Improvement of the preparation method,MnO2/PANI composites were synthesized via simultaneous-oxidation route. Theeffect of preparation condition on the MnO2/PANI composite was investigated. The results showed that MnO2/PANI composite exhibits more excellent electrochemicalperformance. The optimum processing conditions for MnO2/PANI composites were asfollow: the molar ratio of MnCl2and aniline2:1, the reaction time4h and the HClconcentration0.5mol/L. The specific capacitance of MnO2/PANI composite reaches415F/g, higher than the specific capacitance of pure MnO2electrode materials (313F/g)102F/g.