Template-based Construction Of Highly Stable Fiber-based Supercapacitors And Their Performance Study

In recent years,flexible energy storage devices have developed rapidly.Among them,in the research of textile-based flexible energy storage devices,the combination of conductive layer and active materials needs to be solved first,so the high material-fiber bonding stability is particularly important for the application of flexible electrodes.In order to solve this problem,at present,the material is loaded on the fabric surface mainly by physical coating or chemical deposition.However,the physical coating method takes time to produce,and the material-fiber bonding is relatively weak and uneven,which greatly reduces the electrochemical performance and service life of the devices.Compared with the physical coating method,the chemical deposition method solves the problem of weak interfacial bonding between material and cellulose fiber,but the electrochemical cycle stability is lower.Therefore,it is of great significance for further practical application to find ways to improve the stability of fabric-material.Conductive polymers（CP）are widely used as conductive layers and active materials because of their high conductivity and good interfacial compatibility with cellulose fibers.At present,researchers mainly prepare conductive energy storage fabrics by traditional liquid phase polymerization.However,the CP layer prepared by this method has a stacked structure of nanoparticles,which will lead to unstable bonding and uneven load between the material and the fabric.Adjusting the shape of CP can solve the problem of structural stability.Two-dimensional（2D）CP has high flexibility and high specific surface area,which can be stably and firmly wrapped on the surface of cellulose fibers.At present,2D CP is mainly realized by electrochemical deposition.However,the 2D CP prepared by this method generally has a vertical growth structure and has low structural stability in the bending process.Therefore,there is still a lack of effective and feasible methods to produce cellulose-based CP fabrics with stable performance on a large scale.Based on the above discussion,this paper uses a salt template-assisted vapor phase polymerization method to stably wrap 2D CP on the fabric to construct a high stable fiber-based supercapacitor.On the one hand,by making use of the growth force provided by the interface direction,the template is uniformly inserted into the surface of the cellulose fiber,and the material grows along the interface of the template.Finally,the 2D CP will be uniformly wrapped along the interface of the cellulose fiber,which makes it possible for the continuous preparation of high strength flexible energy storage electrode.On the other hand,the two-dimensional morphology of PPY and cotton fiber can be combined by more hydrogen bonds,so it is more firmly coated on the surface of cellulose fiber,which greatly improves the bonding stability between material and fiber and provides good energy storage performance.The specific research contents are as follows:1.Using CuCl₂ as salt template,2D PPY conductive layer was loaded on the surface of cotton fiber by salt template-assisted vapor phase polymerization.First of all,through the microscopic characterization of the material,the load of the prepared 2D conductive layer on the fiber surface was observed.Secondly,the chemical composition and structure of the material were analyzed to verify the structural properties of the material.Finally,the effect of the 2DPPY coating on its electrochemical stability was verified by relevant electrochemical performance tests.The results show that the electrode prepared by this method shows excellent cyclic stability（the capacity retention is 86.5%after 12000 cycles）,and the capacitance retention of the assembled single flexible device is 88.73%after bending 1000 cycles at a bending angle of 180°,and still maintains a good CV shape during the bending process.2.This method is compared with the traditional liquid phase polymerization method from the aspects of morphology characterization,electrical conductivity and mechanical stability,and the reason for the high stability of the electrode structure is analyzed.Then,the solid interface bonding mechanism constructed by this method is analyzed,and the bonding mechanism is verified by different experiments.The results show that the coating process of2D CP on fiber is mainly affected by the concentration of salt template,but has nothing to do with the surface properties of cellulose fiber.The higher the uniformity of the template loaded on the fabric,the easier it is to realize the stable structure of the fiber-material interface.According to the analysis results,we have successfully applied it on different fiber substrates.This paper provides a new idea for the design of flexible electrode with high stability and has great practical application potential in the future production.