2.4 MnO2/PPy复合电极材料电化学性能研究2.4.1 循环伏安

2.4 MnO2 / PPy composite electrode electrochemical properties study <br>2.4.1 cyclic voltammogram <br>MnO2 / cyclic voltammograms of PPy composite electrode material prepared under optimum conditions, a constant current charge-discharge curve and cycling stability electrochemical performance was tested. FIG 8 (a) of MnO2 and MnO2 / PPy at a scan rate of 10 mV • s-1 during the cyclic voltammogram, both rectangular and symmetrical curves showed type described having good characteristics and reversible pseudocapacitive oxide reductive. Further, the current area of MnO2 / PPy is significantly greater than single component of MnO2, i.e. MnO2 / PPy specific capacity of greater than MnO2. Analysis of its causes, on the one hand, of PPy is an electrically conductive polymer, effectively compensate for a poorly conductive MnO2 defects, so that it more accessible for electron MnO2, to improve the utilization of the active material. On the other hand, with PPy of MnO2 chemically (such as hydrogen bonding) interactions, electron transfer may be reduced to improve barrier MnO2 / PPy specific capacity [23]. <br>FIG 8 (b) is a cyclic voltammogram of MnO2 / PPy curves at different scan rates. As the scan rate increases, the class rectangular cyclic voltammogram deformation occurs gradually, because at higher scan rates, the electrolyte ions can not efficiently diffused into the active site region, and there is also such that the electrode polarization not completely charging and discharging, which are caused by some influence on the diffusion of the ions, resulting in reduced [24] specific capacity.

2.4 Study of electrochemical properties of MnO2/PPy composite electrode materials<br>2.4.1 Cycle Vauon Curve<br>The electrochemical properties such as the circular volte curve, constant current charge and discharge curve and circulation stability of MnO2/PPy composite electrode material prepared under the best process conditionwere were tested. Figure 8(a) is MnO2 and MnO2/PPy's circular volte curve at a scan speed of 10 mV-s-1, both of which are rectangular and symmetrical, indicating that they have good seamount capacitive properties and reversible redox ability. In addition, the current area of MnO2/PPy is significantly larger than the single component MnO2, i.e. the ratio capacity of MnO2/PPy is greater than MnO2. On the one hand, The analysis of its reasons, PPy is a conductive polymer, effectively make up for the MnO2 conductivity of poor defects, making electronics easier to reach MnO2, improve the utilization of active materials. On the other hand, the interaction between MnO2 and PPy chemical bonds (e.g. hydrogen bonds) can also reduce the barrier of electronic transfer to increase the MnO2/PPy ratio capacity.<br>Figure 8(b) is a circular volte curve for MnO2/PPy at different scan rates. With the increase of the scanning rate, the circular volt-security curve of the rectangle gradually morphs, because the high scanning rate, the electrolyte ions can not effectively diffuse to the active site area, and the existence of polarization phenomenon also makes the electrode will not be fully charged and discharged, which will have a certain impact on the diffusion of the ions, resulting in a decrease in the ratio of capacity.

Electrochemical properties of 2.4 MnO2 / PPy composite electrode materials<br>2.4.1 cyclic voltammetric curve<br>The electrochemical properties of MnO2 / PPy composite electrode, such as cyclic voltammetry, constant current charge discharge curve and cyclic stability, were tested. Figure 8 (a) shows the cyclic voltammetric curves of MnO2 and MnO2 / PPy at the scanning speed of 10 MV · s-1. Both curves are rectangular and symmetrical, indicating that they have good pseudo capacitance characteristics and reversible redox properties. In addition, the current area of MnO2 / PPy is larger than that of single component MnO2, that is, the specific capacity of MnO2 / PPy is larger than that of MnO2. On the one hand, PPy is a kind of conductive polymer, which effectively makes up for the poor conductivity of MnO2, makes it easier for electrons to reach MnO2, and improves the utilization rate of active materials. On the other hand, the interaction between MnO2 and PPy chemical bond (such as hydrogen bond) can also reduce the barrier of electron transfer and improve the specific capacity of MnO2 / PPy [23].<br>Figure 8 (b) shows the cyclic voltammetric curves of MnO2 / PPy at different scanning rates. With the increase of scanning rate, the rectangular like cyclic voltammetric curve gradually deforms, which is because the electrolyte ions can not effectively diffuse to the active site area at a higher scanning rate, and the existence of polarization phenomenon also makes the electrode not fully charge and discharge, which have a certain impact on the diffusion of ions, resulting in a reduction in specific capacity [24].<br>