Preparation Of Polyaniline Composite Electrode Material And Research On Supercapacitor Performance

Supercapacitors are a new type of energy storage device with excellent performance between traditional capacitors and chemical batteries.Supercapacitors can effectively improve the low energy density and power density of secondary batteries and become a research hotspot in the field of electrochemical energy storage devices.The choice of electrode material plays a decisive role in the performance of supercapacitors.It determines the main performance indicators of energy storage devices,such as energy density,power density and cycle stability.Conductive polymer polyaniline(PANI)has become the first choice for supercapacitor electrode materials due to its good electrical conductivity and high pseudo-capacitance storage.However,PANI complex and changeable microstructure and polymer chains swell and shrink during charging and discharging.This phenomenon will seriously affect PANI pseudocapacitance and cycle stability.This thesis mainly focuses on the design and synthesis of PANI composite electrode materials in order to obtain electrode materials with excellent electrochemical performance.The research work combines PANI with?-crystalline manganese dioxide(?-MnO₂),carbon fiber(CF)and carbon cloth(CC)to form binary or ternary composite materials to enhance the interaction and construction of composite materials.Flexible supercapacitors provide new research ideas for the practical application of high-performance supercapacitors.The main research contents are as follows:(1)The?and?crystalline MnO₂ was prepared by hydrothermal method,and ?-MnO₂,?-MnO₂ and aniline were prepared by in-situ polymerization to synthesize?-MnO₂/PANI and ?-MnO₂/PANI composite electrode materials.The ?-MnO₂/PANI composite electrode material exhibits excellent electrochemical performance.The microstructure and electrochemical performance of the ?-MnO₂/PANI composite electrode material in different electrolytes were tested.The results show that ?-MnO₂ has certain stability in acidic electrolyte,and its introduction significantly improves the specific capacity and cycle stability of polyaniline.At a current density is 1 A g^-1,its specific capacity can reach 580.2 Fg^-1 in 0.5 M H₂SO₄electrolyte.When the current density increased from 1 Ag^-1 to 5 Ag^-1,its rate performance is 70.5%.The ?-MnO₂/PANI composite electrode and activated carbon(AC)assembled into an asymmetric capacitor.At a current density of 1 Ag^-1,the energy density is 66.4 Wh kg^-1 and the power density is 350.1 W kg^-1.The specific capacitance remains 78.65% after 3000 cycles when the current density is 5 Ag^-1.(2)The ?-MnO₂ nanoparticles were loaded on the surface of CF by hydrothermal reaction,and then chemically in situ polymerized with aniline at low temperature to prepare CF/MnO₂/PANI composite materials.The CF/MnO₂/PANI composite electrode material of the microstructure and electrochemical performance were tested.The results show that the electrochemical performance of the CF/MnO₂/PANI composite electrode material is significantly better than that of CF/PANI and PANI.At a current density of 1 Ag^-1,CF/MnO₂/PANI composite electrode material shows a specific capacitance of 654.3 Fg^-1,When the current density increased from 1 Ag^-1 to 10 Ag^-1,its rate performance is 78.1%.The flake and granular ?-MnO₂ supported on the surface of CF and coated by PANI,which effectively improve the utilization rate of MnO₂ and PANI.The CF/MnO₂/PANI electrode material and AC are assembled an asymmetric capacitor.When power density is 750 W kg^-1 at a current density of 1 Ag^-1,its energy density can reach 30.9 Wh kg^-1,and the specific capacitance remains 73.2%at a current density of 5 Ag^-1 after 5000 cycles.(3)The CC/MnO₂/PANI composite electrode material was prepared by using hydrothermal reaction to loadg-MnO₂ on the surface of CC and coating PANI on the surface by electropolymerization.The microstructure and electrochemical performance of CC/MnO₂/PANI composite electrode materials were tested.The results show that the CC/MnO₂/PANI composite electrode material exhibits significantly better electrochemical performance than CC/PANI and CC.It shows a specific capacitance of 1105 mF cm^-2 at a current density of 1 mA cm^-2,.When the current density increased from 1 mA cm^-2 to 10 mA cm^-2,its rate performance is 72.3%.The CC/MnO₂/PANI composite electrode material and CC/MnO₂ assembled as asymmetric two electrodes,and the voltage window can be expanded to 1.5 V.When the energy density is 1.5 m Wh cm^-3,the power density is 10.4 mW cm^-3 at a current density of 1mA cm^-2.The specific capacitance remains 87.1% at a current density of 5mA cm^-2 after 2000 cycles.