Study On Electrochemical Energy Storage Of Transition Metal Surface-Interface Coordinated Polyaniline

Polyaniline(PANI)is considered as one of most promising electrodes due to its good flexibility,easy synthesis,high theoretical capacitance and environmental friendliness.The applications of PANI-based electrodes in supercapacitor have been widely concerned and reported.However,it is well known that the volume of PANI inevitably expands and contracts in the process of charge and discharge.The repeated volume changes lead to the fracture of PANI molecular chain,which result in poor cycle stability of PANI.In this paper,the strategies of surface coordination,interface coordination,and surface-interface coordination are designed to improve the cyclic stability and electronic conductivity of PANI.The coordination mechanism between transition metal and PANI,the electronic structure and polymer molecular stability of transition metal coordinated PANI are analyzed by experimental characterization and theoretical simulation.The energy storage performance of transition metal surface-interface coordinated is investigated by electrochemical test method.The works of the paper mainly include three parts:(1)Study on electrochemical energy storage of cobalt coordinated polyanilinePANI-Co electrode is synthesized by electropolymerization and hydrothermal methods.Co-N coordination bond is formed between polyaniline surface and cobalt ion.The morphology and structure are characterized by SEM,UV-Vis and Raman.The R_o value of PANI-Co(0.69?)is lower than PANI(0.83?).PANI-Co achieves higher capacitance of 653F g^-1 at 1 A g^-1 than PANI of 459 F g^-1,and maintains high capacitance retention of 85.60%from 1 to 10 A g^-1.The DFT calculations show that the N(E)value of PANI-Co(11.2electron/e V)is evidently higher than that of PANI(5.8 electron/e V),suggesting transition metal ions coodination can effectively improve the electronic conductivity of PANI.PANI-Co electrode is also assembled into symmetrical supercapacitor.When the output voltage is 1.8 V and the current density is 1 A g^-1,the specific capacitance of PANI-Co supercapacitor is 133 F g^-1.The energy density of PANI-Co supercapacitor is 60.1 W h kg^-1 at the power density of900 W kg^-1.PANI-Co supercapacitor exhibits high capacitance retention of 83.8%after 1000cycles at 5 A g^-1.The surface coordination bond of cobalt ion can improve the electronic conductivity,capacitance and cycle stability of PANI.(2)Study on electrochemical energy storage of interface Mo-N bonding MoS_xN_y@PANIMoS₂ is synthesized by hydrothermal method.After treatment for MoS₂ by nitrogen atmosphere(MoS_xN_y),PANI is deposited on MoS_xN_y(MoS_xN_y@PANI).Interface Mo-N coordination bond is formed between MoS_xN_y and PANI.The morphology and structure of the MoS_xN_y@PANI are characterized by SEM,Raman and XPS.MoS_xN_y@PANI electrode has higher capacitance of 577 F g^-1 at 1 A g^-1 than MoS₂ of 193 F g^-1 and PANI of 459 F g^-1.The capacitance retention of MoS_xN_y@PANI is 85.3%at 5 A g^-1 for 3000 cycles,while PANI is only 57.1%.In DFT calculations,the bandgap of MoS_xN_y(0.65 e V)is lower than MoS₂(1.45 e V).The interface coordination between PANI and MoS_xN_y is studied by population analysis and single atom density of states.The MoS_xN_y@PANI electrode is also assembled into symmetrical supercapacitor.When the output voltage is 1.6 V and the current density is 1A g^-1,the specific capacitance of MoS_xN_y@PANI supercapacitor is 90 F g^-1.The energy density of MoS_xN_y@PANI supercapacitor is 32.1 W h kg^-1 at the power density of 800 W kg^-1.The capacitance retention of this supercapacitor is 87.5%for 2000 cycles at 3 A g^-1.Interface Mo-N coordination bond can improve the capacitance and cycle stability of PANI.(3)Study on electrochemical energy storage of surface-interface coordinated polyanilineTransition metal ions surface-interface coordinated polyaniline(MoS_xN_y@PANI-M(M=Co,Cu and Zn))is synthesized by hydrothermal and electropolymerization methods.The morphology and structure of the MoS_xN_y@PANI-M are characterized by SEM,Raman and XRD.The specific capacitances of MoS_xN_y@PANI and MoS_xN_y@PANI-M(M=Co,Cu and Zn)are 497,583.6,873.8 and 697.5 F g^-1 at 1 A g^-1,respectively.The capacitance retention of MoS_xN_y@PANI and MoS_xN_y@PANI-M(M=Co,Cu and Zn)achieve 85.3%?88.5%?87.8%and 93.6%after 3000 cycles at 5A g^-1.The R_o value of MoS_xN_y@PANI-M(M=Co,Cu and Zn)(0.83,0.85?1.04?)is lower than MoS_xN_y@PANI(1.08?).DFT calculations show that the N(E)value of MoS_xN_y@PANI-M(M=Co,Cu and Zn)(10.6,13.2 and 5.9 electron/e V)is higher than H-PANI(5.4 electron/e V).MoS_xN_y@PANI-Cu electrode is assembled into symmetrical supercapacitor.When the output voltage is 1.6 V and the current density is 1 A g^-1,the specific capacitance of MoS_xN_y@PANI-Cu supercapacitor is 179 F g^-1.The energy density of MoS_xN_y@PANI-Cu supercapacitor is 63.9 W h kg^-1 at 800 W kg^-1.The capacitance retention of this supercapacitor is 83.5%for 2000 cycles at 3 A g^-1.Transition metal ions surface-interface coordination can further improve electronic conductivity,capacitance and cycle stability of PANI.