| Facing the pressures of oil crisis and environmental pollution, People has strong desire for new energies and new energy materials. As a new energy storage device, supercapacitor has drawn great attention by academic circles and industrial circles. In recent years, the research of electrode materials for supercapacitor becomes a new research hotspot. In this paper, Our study mainly focuses on seeking new synthetic methods, developing special microstructure and excellent performance electrode materials for supercapacitor with the idea of composite material. The materials are analyzed by SEM (scanning electron microscope), XRD (X-ray diffraction), IR (infrared spectroscopy), CV (cyclic voltammetry), EIS (impedance testing) and constant current charge-discharge, and other modern methods. The discharged specific capacifor of materials make from the three methods this paper invent are 179.6 F/g?197.2 F/g and 214.OF/g respectively, much higher than that of MnO2(129.3 F/g). This paper studies conducting polymers, carbon materials and metal oxides, three major types of electrode materials for supercapacitors.(1) we used MnO2 and APS as the oxidant, respectively, through oxidation polymerization to prepare conductive PANI (PANI) electrode material, using formic acids with different concentrations as the dopant through interfacial polymerization to prepare PANI electrode material, using MnO2 as the oxidant, through in-situ oxidation polymerization to synthesize conductive PANI-CNT electrode material. The structure and morphology of the these electrode materials were analyzed by XRD and SEM. Assembled 2032 experimental button supercapacitors with H2SO4 aqueous solution as electrolyte to test the electrochemical performances of the electrode materials. The results showed that:?PANIs which obtained by oxidation polymerization, using MnO2 and APS as the oxidant respectively, had the same molecular structure, but different micro-morphologies and electrochemical performances. The first discharge specific capacities of M-PANI (MnO2 as the oxidant) was 259.4 F/g, which obviously higher than 165.7 F/g of A-PANI (APS as the oxidant). After 500 cycles, the specific capacity retention of M-PANT was 72.6%, while it of A-PANI was only 57.8%. Therefore, by optimizing oxidant we can prepare well performed PANI electrode material for supercapacitor through oxidation polymerization.?The concentrations of dopant had little effect on molecular structure of PANI, but had great influence on its micro-morphology and electrochemical properties when prepare it through oxidation polymerization. In this study, PANI nanoparticles changed into nanofibers with the increase of HCOOH concentration. The first discharge specific capacity of PANI-1.8 was 291.8 F/g. So by optimizing of the concentration of dopant we can obtain better performance of PANI electrode material for supercapacitor through oxidation polymerization.?PANI-CNT (M-PC) electrode material could synthesize by in-situ oxidation polymerization, using MnO2 as the oxidant. PANI and the CNT form M-PC by mixing and bonding. The first specific capacitance of the M-PC was about 354.8 F/g at a current density of 5mA/cm2. After 500 charge-discharge cycles the specific capacitance of the M-PC remained 305.7 F/g, the capacitance holding rate was up to 86.2%. The results show that conductive PANI-CNT electrode materials with excellent properties could be prepared by in-situ oxidation polymerization, using MnO2 as the oxidant. This would promote the practical application of PANI.(2) The a-MCMB (activated mesocarbon microbead) was prepared through KOH activated method, and its electrochemical performance has been tested. An and a-MCMB as main raw materials, APS as the oxidant, through in-situ oxidation polymerization, we synthesize PANI-(a-MCMB) composite materials, and the micro-morphology and electrochemical performance of PANI-(a-MCMB) were investigated.?a-MCMB with excellent sphericity, modest activating rate, high specific surface area, high mesopore volume and high total pore volume could be prepared when activation temperature was 950?.The specific surface area, the mesopore volume and the total pore volume was 3290 m2/g?64% and 1.52cm3/g, respectively.?At a current density of 5mA/cm2, the first specific capacitance of a-MCMB (prepared at 950?) was 253.6 F/g and 171.9 F/g, respectively, in 30% KOH water electrolyte and 1 mol/L LiPF6/ (DMC+EC) organic electrolyte. The a-MCMB had good electrochemical performance both in water electrolyte and organic electrolyte.?PANI-(a-MCMB) was microspheres with its diameter at about 15?25?m. Nanofibrous PANI (diameter of 35?50 nm, length of 150?350 nm) coated on the surface of microspheres. It owned the advantages of PANI and a-MCMB. The first specific capacitance of PANI-(a-MCMB) reached 288.5 F/g. PANI-(a-MCMB) was easily synthesized, and even a practical and novel electrode material for supercapacitor.(3) MnO2 electrode material was prepared by two-step hydrothermal method, which included Ultrasonic chemical pre-reaction and Hydrothermal Synthesis in acidic solution. And studied its electrochemical properties in 1 mol/L LiPF6/(DMC+EC) organic electrolyte; Three preparation methods which were prospects-room-temperature liquid phase redox, liquid chemical precipitation and low-temperature solid phase synthesis, were applied to prepare three novel spherical MnO2-(a-MCMB) composites (M-a-M 1, M-a-M2 and M-a-M3) with different morphologies. And we studied their electrochemical properties. The results showed that:?MnCO3 as main raw material, KClO3 as the oxidant, An interesting MnO2 nano wire-sphere with diameter of 5?25?m had been obtain through a hydrothermal method. The diameter of nanowire was about 80 nm. MnO2 nano wire-sphere Showed good electrochemical properties at 0 V-2.5 V in 1 mol/L LiPF6/(DMC+EC) organic electrolyte. The first specific capacitance and energy density of MnO2 was 129.3 F/g and 45.7Wh/kg at a current density of 2mA/cm2, respectively. ?M-a-M1, M-a-M2 and M-a-M3 had different morphologies. In M-a-M1, granular MnO2 with size of 80?250 nm, uniformly distributed on the surface of a-MCMB; In M-a-M2, Flake-like MnO2 about 100?220 nm long and 70?80 nm wide, equally distributed on the surface and in the Cracks of a-MCMB; In M-a-M3, needle-like MnO2 evenly spread on the surface of a-MCMB sphere, its length was about 1.5?3.0?m and diameter was about 20-30 nm.?M-a-M1, M-a-M2 and M-a-M3 showed good electrochemical performance in 1 mol/L LiPF6/(DMC+EC). M-a-M1 showed excellent reversible charge-discharge performance, its first specific capacitance and energy density was 179.6 F/g and 99.1Wh/kg at a current density of 2mA/cm2. After 1000 charge-discharge cycles the specific capacitance retained 130.8 F/g, which still higher than the first specific capacitance of MnO2 (129.3 F/g). The first specific capacitance and energy density of M-a-M2 was 197.2 F/g and 106.3Wh/kg at a current density of 2mA/cm2. Even after 2000 charge-discharge cycles in the current density of 8mA/cm2, it still had a higher capacity, so M-a-M2 owned excellent conductivity and wonderful power characteristics. M-a-M3 showed even better capacitance performance and higher power characteristics than M-a-M1 and M-a-M2. The first specific capacitance and energy density of M-a-M3 was 214.0 F/g and 127.4Wh/kg at a current density of 2mA/cm2. Therefore, M-a-M1, M-a-M2 and M-a-M3 were all demonstrated the advantages of the carbon materials and metal oxide compound. To some extents, they overcome the disadvantages of pure MnO2, such as poor power characteristics, poor conductivity, low capacitance and low energy density, etc.(4) PANI-CNT (M-PC) electrode material was synthesized through in-situ oxidation polymerization, using MnO2 as the oxidant. Using An and a-MCMB as main raw material, APS as the oxidant, through in-situ oxidation polymerization one can synthesize PANI-(a-MCMB) composite materials. MnO2 electrode material was prepared by two-step hydrothermal method. And three preparation methods, prospects-room-temperature liquid phase redox, liquid chemical precipitation and low-temperature solid phase synthesis, were applied to prepare three novel spherical MnO2-(a-MCMB) composites (M-a-M1, M-a-M2 and M-a-M3) with different morphologies. No individual or academic team had report all of these yet. |
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