Study On Preparation And Performance Of Conductive Polymers And Their Derivatives-based Electrodes

Due to the continuous high consumption resulted from and the the rapid development of science and technology and the limited supply of fossil fuels,mankind has to face the problem of energy scarcity.The increasing energy demand is also forcing scientists to develop new energy conversion and storage devices.Among various devices,supercapacitor,as a high-efficiency energy storage device,is a very promising energy device for the practical application,which can effectively make up for the shortage of secondary batteries and physical capacitors.Generally the performance of supercapacitors is largely influenced by the electrode materials.Therefore,it is crucial to develop electrode materials with high specific capacitance.Conductive polymer is a supercapacitor electrode material with high specific capacitance electrode and is expected to be commercialized.However,there are some problems with conductive polymers remained in capacitor applications.For example,the doping/de-doping process of ions occurs during the process of charging and discharge,resulting in irreversible changes in volume,which will affect the cycle stability of the supercapacitor.In addition,the dense surface structure of the conductive polymer film reduces the surface area of the electrode material involved in the redox reaction.Therefore,the conductive polymer is difficult to adapt to the rapid charging and discharge process under high-power demand,causing low specific capacitance and utilization of electrode materials.Therefore,developing different processes and technologies can be an effective way to increase the storage capacity of supercapacitors.But it is more important to explore the preparation of various electrode materials with better performance in terms of future development prospects.Based on this,this paper aims to increase the effective specific surface area of the capacitor electrode by constructing a mosaic structure composite material to improve the electrochemical performance of the supercapacitors.The details are as follows:1.The self-supported polypyrrole/prussian blue（PPy/PB-X:1,X:1 is the volume ratio of iron p-toluenesulfonate to potassium ferricyanide）composite electrode material was prepared by introducing Prussian blue（PB）,which was synthesized synchronously,into polypyrrole（PPy）thin film by a chemical precipitation method combined with a vapour phase polymerization（VPP）.The purpose of introducing Prussian blue is to enhance the specific capacity and specific surface area of the electrode material.The self-supporting structure of the thin film electrode can avoid problems such as reduced conductivity of the electrode material caused by the use of binder,and the smaller charge transfer impedance proves that the composite material has good conductivity.The porous structure generated after the introduction of PB can weaken the volume changes in the electrode material structure caused by changes in the volume of the electrode material during charge and discharge.Electrochemical studies showed that supercapacitors assembled with PPy/PB-2:1composites with an optimal structure have a specific capacitance as high as 447.6 F g^-1.The charge/discharge performance study showed that the specific capacity retention rate of PPy/PB-2:1 was 70.8%when the current density was increased from 1.0 A g^-1 to 10.0 A g^-1,proving the PPy/PB-2:1 was with excellent comprehensive performance.After 4,000 cycles of constant current charge and discharge,the capacity of PPy/PB-2:1 is attenuated by 23.1%,and the capacitance retention rate is 76.9%,which was higher than that of pure PPy electrode material,showing better capacitance performance.2.Poly 3,4-ethylenedioxythiophene（PEDOT）films doped with anatase titanium dioxide（Ti O₂）（PEDOT-X Ti O₂,X is the mass concentration）were synthesized as composite electrode materials using a modified VPP method.Titanium dioxide has relatively stable physical and chemical properties and good electrochemical performance,which can enhance the reversibility of electrode materials and provide additional pseudo-capacitance capacity.Meanwhile,the high specific surface area of anatase increases the specific surface area of the composite material,providing more doping/de-doping sites for the PEDOT redox reaction.The electrochemical performance of supercapacitors assembled with composite materials was investigated by a series of electrical measurements such as cyclic voltammetry and charge/discharge characterization.The test results in the three-electrode system demonstrated that the mass specific capacitance of PEDOT-2.0wt%Ti O₂ was 466 F g^-1 at a current density of 2.0 A g^-1,while the pure PEDOT film electrode was only 140 F g^-1.In the symmetric device,the mass ratio capacitance of PEDOT-2.0wt%Ti O₂ was 203.4 F g^-1 at 2.0A g^-1,and the capacity can be maintained up to 51.1%of the initial value with the current density increasing to 10.0 A g^-1,while the capacity of the pure PEDOT film electrode can only be maintained up to 41.1%of the initial value.The PEDOT-2.0wt%Ti O₂ symmetrical supercapacitor device achieved 76%capacity retention after 4000 charge/discharge cycles,which had better stability compared to the PEDOT symmetrical device.