Conductive Polymer Based Graphene Hydrogel For Energy Strorage Performance

The high mechanical stability and electrochemical performance of flexible supercapacitors can be adapted to the rapid development of flexible electronic devices.In order to solve these problems,the research work presented in this thesis are focused on self-supporting electrodes,rationally constructing the graphene-based conductive polymer hydrogels system.These electrode materials have to overcome the problems of low graphene capacity and capacity attenuation caused by the volume expansion of conductive polymers.The main research contents and conclusions are presented as follows:（1）polyaniline/multiwall carbon nanotubes/graphene（PCR）composite hydrogels.In this work,the pre-synthesized eigenstate polyaniline powder was successfully loaded on the three-dimensional porous framework of graphene through a self-assembly strategy,and thus producing the polyaniline based graphene（PR-4）hydrogels.Likewise,based on the similar fabricated strategy of PR-4 hydrogel,a polyaniline/multi-wall carbon nanotube/graphene（PCR-5）composite hydrogel with a sandwich structure was prepared by introducing high conductivity MWCNTs into this carbon skeleton.Due to the addition of MWCNTs,the specific surface area of PCR-5hydrogel is increased by 36.8%compared with PR-4,and the conductivity is increased by 32.2%.In addition,PCR-5 also exhibits excellent electrochemical performance,showing an ultra-high specific capacitance of 917 F g^-1 when the current density is 1 A g^-1,which is higher than that of PR-4(751 F g^-1).Even when the current density is increased to 20 A g^-1,PCR-5 still has a high rate capability（about84%）,which is also higher than PR-4（77%）.The asymmetric flexible all-solid-state supercapacitor based on PCR-5（RGO is the negative electrode,PCR-5 is the positive electrode）shows good mechanical and electrochemical stability.The device can provide the highest energy density of about 31.32 Wh kg^-1 when the power density is364.93 W kg^-1;after 1000 cycles of charging and discharging,it can still maintain87.6%of the specific capacitance;even if the FAASSC device is repeatedly folded in half for 1000 times,the capacitance retention rate is still as high as 94%.（2）polypyrrole based graphene（PGR）hydrogels.In this work,a very simple and efficient synthesi zed strategy is proposed to solve the dispersibility problem of polypyrrole by in situ polymerizing pyrrole in GO solutions,producing the polypyrrole@graphene oxide（PPy@GO）powder with high dispersibility.Then,the highly dispersible PPy@GO powder was ultrasonically dispersed in the GO aqueous solution,and a simple chemical reduction was used to prepare a highly uniform polypyrrole/reduced graphene oxide（PGR-4）composite hydrogel.The PGR-4 hydrogel synthesized based on this strategy has excellent electrochemical properties,with an ultra-high specific capacitance as high as 631 F g^-1 when the current density is 1 A g^-1;even if the current density is increased to 20 A g^-1,still maintaining a capacitance retention rate of 84%.Furthermore,PGR-4 and RGO hydrogels were used as positive and negative electrodes to assemble flexible all-solid supercapacitors（FASC）,which showed excel lent electrochemical performance.FASC can provide an energy density as high as 19.32 Wh kg^-1 when the power density is 593.29 W kg^-1;it maintains a specific capacitance of 91%after 3000cycles of charging and discharging.In addition,FASC also exhibit s excellent mechanical stability,and still retains 93.8%of the specific capacitance after being repeatedly folded 2000 times.As a result,the conductive polymer/graphene composite hydrogel electrode based on the sandwich structure exhibits excellent el ectrochemical performance,and the assembled flexible all-solid-state supercapacitor exhibits excellent mechanical and electrochemical properties under bending and folding conditions.Stability,thus showing broad application prospects in the field of flex ible energy storage.