Preparation And Energy Storage Performance Of RGO/PANI Homogeneous Composite Flexible Self-Supported Electrode

Flexible supercapacitors have important application value in the field of portable electronic devices due to their excellent energy storage and deformability.As an indispensable part of flexible supercapacitor,flexible electrode should have good energy storage performance and excellent mechanical properties.But how to realize flexible electrode with both excellent energy storage and flexibility is one of the problems must be solved urgently.In this thesis,the reduced graphene oxide/polyaniline（RGO/PANI）composite electrodes with homogeneous structure are designed.The homogeneous structure can improve the PANI loading mass on the free-standing electrode,and thus can modify the energy storage performance of the electrode.At the same time,the homogeneous structure can avoid the excessive stacking and agglomeration of graphene sheets,which are beneficial for assembling the uniform composite into flexible electrodes with good mechanical properties.In this thesis,the morphology and energy storage performance of the homogeneous composite flexible electrode are systematically adjusted and researched,it includes the following aspects:（1）Preparation and tuning of GO/PANI composite gel.GO is synthesized by the improved Hummers method and PANI is mixed with GO dispersion to form the GO/PANI gel through the interaction between PANI and GO.Subsequently,the free-standing RGO/PANI composite gel electrode is obtained after the reduction and shaping processes.The influence of PANI hydrogel content on the structure and performance of the RGO/PANI gel electrode is investigated.The results show that the introduction of PANI can improve the specific capacitance（C_s）of graphene electrode,When the content of PANI hydrogel is too high,the agglomeration occurred and thus deducted the energy storage performance of gel electrode.When the content of PANI hydrogel is 11%,the composite gel electrode exhibits best energy storage performance with the C_s reaching 229.98 F g^-1 at 1 A g^-1.After being assembled into a symmetrical supercapacitor,the C_s reaches 154.91 F g^-1 at 0.50 A g^-1,it also has a good cycle stability,and the C_s still remains 87.10%after 10,000 cycles.（2）Preparation and tuning of GO/PGO/GO sandwich-like homogeneous structure composites.In order to increase the mass loading of PANI,the strategy of pre-compounding and then assembling is adopted to prepare G/PG/G free-standing composite electrodes with homogeneous structure.Firstly,the GO/PANI composite sheet（PGO）is prepared by in-situ growing PANI array on the surface of GO sheet by chemical polymerization.The PGO is stacked with additional GO（marked as GO2）to form a sandwich-like structured GO/PGO/GO.Then,the GO/PGO/GO sandwich-like composite sheets is assembled into a uniform flexible free-standing film electrode by vacuum filtration method,and the G/PG/G free-standing composite electrodes with good flexibility can be obtained by reduction processes.The effects of in-situ growth temperature,in-situ growth time and concentration of PANI monomer on PANI morphology are studied.The results show that PANI is suitable to be synthesized at 3℃for 24 h,and the height of PANI array reaches about 53.40 nm when the concentration of aniline is 0.09 M.Different contents of PGO in G/PG/G free-standing composite electrode are adjusted to prepare electrode with excellent electrochemical performance.When PGO content reaches 70%,the PANI loading mass in the free-standing electrode reaches 38.5%and the C_s reaches 345.60 F g^-1 at 0.20 A g^-1,but the C_s decreases rapidly with the increase of current density.（3）Preparation and tuning of homogeneous RGO/PGO/RGO composite fibers.On the basis of above GO/PGO/GO sandwich-like homogeneous structure composite sheets,the homogeneous composite fiber electrode is prepared by hydrothermal method,which makes the sheets stacked more tightly,and the homogeneous composite electrode is endowed with good stitchability while further increasing the mass loading of PANI.The effects of the content of reducing agent and PGO sheet on the morphology and performance of PGR homogeneous composite fiber electrode are studied,and a PGR homogeneous composite fiber electrode with good electrochemical performance is obtained.The PANI loading mass of the PGR homogeneous composite fiber electrode reaches 41.6%,which is obviously higher than reported works on RGO/PANI composite fiber electrodes.The C_s of PGR-41.6%homogeneous composite fiber electrode（VC/GO2=2/1）reaches 638.52 F g^-1 at 1 A g^-1 and 375.90 F g^-1 at 10 A g^-1.The C_s of the PGR fiber electrode in symmetric supercapacitor maintains 353.25 F g^-1at 0.20 A g^-1 and 69.45 F g^-1 at 2 A g^-1.The energy density reaches 2.56 m Wh cm^-3 with the power density achieving 271.88 k W cm^-3.The PGR fiber also exhibits excellent flexibility with C_s retention reaching 90.55%after 10,000 bending cycles.