Electrochemical Synthesis And Performance Of Thiophene-based Conducting Polymers And Their Application In MLPC

Polythiophene-based conductive polymers are widely used in many fields because of their good electrical conductivity,processing performance and environmental stability.Currently,the MLPC manufacturing process in China is usually based on chemical polymerization of the conductive polymer cathode layer,and the resulting MLPCs have to be improved in terms of capacity and ESR.To address these issues,in this paper,poly（3,4-ethylenedioxythiophene）（PEDOT）and poly（thiophene）（PTh）conductive polymer films were prepared based on electrochemical oxidative polymerization,and the properties of both films were investigated and their applications in MLPCs were explored.The main results are as follows.（1）PEDOT films were prepared on the conductive substrates by the constant current method,and the conductivity of the films was systematically investigated under different polymerization parameters.The results showed that the conductivity of PEDOT films reached a maximum of 9.64 S/cm with p-toluenesulfonic acid as the dopant(M_{（p-toluenesulfonic acid）}/M_（EDOT）=10:1)and the p H of the polymerization solution was adjusted to 2,and electrochemical polymerization at 0.5m A/cm² polymerization current density and 20℃polymerization temperature.The thermal stability requirements of MLPC for conducting polymer cathode layer were met;however,the films had poor structural uniformity,poor mechanical properties and showed brittleness.The film achieves higher denseness when the p H value of polymerization solution,polymerization current density and polymerization temperature decrease,and can significantly reduce the roughness at high polymerization current density and low polymerization temperature.（2）PTh films were prepared on the conductive substrates by the constant current method,and the surface morphology and conductivity of the films were systematically investigated under different polymerization parameters.The results showed that the PTh films achieved higher densification when the polymerization current density and polymerization temperature decreased,and the roughness decreased significantly when M_{（sodium p-toluenesulfonate）}/M_{（thiophene）}increased.The PTh films with sodium p-toluenesulfonate as dopant(M_{（sodium p-toluenesulfonate）}/M_{（thiophene）}=1:2.5)were electrochemically polymerized at 0.5 m A/cm² polymerization current density and 10℃polymerization temperature,and the conductivity of PTh films reached up to 3.53 S/cm;the starting thermal decomposition temperature of PTh films prepared under this condition was similar to that of PEDOT films,but the mechanical properties of PTh films were better than those of PEDOT films.However,the mechanical properties of PTh films were better than those of PEDOT films,showing stronger toughness.（3）The technical route of"two-step polymerization method"was designed,in which PEDOT first cathode layer was prepared on aluminum foil by chemical polymerization firstly,and then the second cathode layer was prepared by electrochemical oxidation polymerization using the first cathode layer as the conductive substrate;according to this technical route and combining the best polymerization conditions of the two films,DLP（Double-Layer PEDOT）and PP（PEDOT-PTh）MLPCs were fabricated based on this technical route and combined with the optimal polymerization conditions of the two films,and the performance was compared with that of the original PEDOT MLPC.The results show that the DLP MLPC based on 12-turn chemical polymerization foil has the best performance,with the capacity increased by 11.8%compared with the original PEDOT MLPC,reaching 305.7μF,the equivalent series resistance of 2.1 mΩ,a decrease of 66.1%,and the loss factor reduced to1.3%,which is a significant improvement in overall performance.