Preparation And Properties Of Electrochemical Capacitor Electrode Material Manganese Oxide And Its Composites

Supercapacitors also known as electrochemical capacitors.Electrochemical capacitors has excellent properties for next-generation power devices such as fast charge-discharge rate,high power density and long cycle life.Electrochemical capacitors can be categorized as electric double layer capacitor and pseudocapacitor on the basis of their charge storage mechanisms,electric double layer capacitors using carbon-active materials and pseudocapacitors using redox-active materials.The electrode materials are important to electrochemical capacitors,carbon-active materials are promising electrode materials for electric double layer capacitors,which have outstanding electrical conductivity and long cycle life but suffer from relatively low energy-density.Transition metal oxides,for pseudocapacitors electrode materials has been extensive interest in developing commercial attractive because of their much higher theoretical capacitance,however,they have intrinsically low electrical conductivity.In this reports,MnO₂ nanaorods deposited on carbon nanospheres?MnO₂/C?and three-dimensional?3D?structure Mn-active mixed transition metal oxides materials?MTMOs?as electrode materials of electrochemical capacitors have been synthesized via a hydrothermal synthesis and electrochemical deposition,improving the electrochemical properties of materials by synergism.The main points of this dissertation are summarized as follows:1.Melamine formaldehyde resin balls were prepared by using cheap and easily available melamine as raw materials,nitrogen rich carbon nanospheres were obtained by carbonization under nitrogen atmosphere.2.MnO₂/C as electrode materials has been synthesized by reduction of KMnO₄ with carbon nanospheres via a hydrothermal synthesis,and the optimal performance of the nanorod MnO₂/carbon sphere composites was obtained by adjusting the reaction conditions.At a current density of 0.1A g-1,using 1mol L-1Na2SO₄ as electrolyte,the as-prepared MnO₂/C exhibit excellent specific capacitance of 305.6F g-1,and the electrode material has good cycling stability,88.04% retention after 1000 cycles.3.MnCo₂O_4.5 as electrode materials has been synthesized via a hydrothermal synthesis,and a novel three-dimensional structure of MnCo₂O_4.5@MnCo₂O_4.5electrode material was obtained by electrochemical deposition.And an extensive study of the electrode properties with respect to changes of the deposition time of 20,50 and80 cycles has been carried out.At a current density of 1A g-1,the as-prepared MnCo₂O_4.5@MnCo₂O_4.5 exhibit excellent specific capacitance of 1580 F g-1observed at 50 cycles,far larger than 20 cycles and 80 cycles.Also,this electrode demonstrated a good rate capability with 52.2% retention even the current density increasing to 10 times.The specific capacitance of three-dimensional structure MnCo₂O_4.5@MnCo₂O_4.5-50 electrode material has 98.2% retention after 2000 cycles,the results show that the synthesized 3D structure material has a long service life.