Preparation, Characterization And Electrochemical Performance Of Anode Material For MnO₂-based

Energy and environment is not only a major issue of common concern all over theworld but also an important problem in the social and economic development of ourcountry. The development of human society depends on the emergence ofhigh-quality energy and advanced energy technologies, which will make thedevelopment of low carbon economy and clean renewable energy to become a hotissue in the world. Such as solar energy and wind energy, which are new types ofrenewable energy sources, are today’s hot topic of each country. However, the outputof these energy is strongly dependent on the natural conditions, and the demand of theenergy do not match in some cases, so we need such a energy storage system: Whenenergy superfluous, store it up and When demand, it can be released.This research work is focused on the synthesis of nanomaterials with high specificsurface area and upgrading the capacity to improve the energy density.The results of this paper include the following several parts:(1) The rod-like Na0.95MnO2was prepared by a simple and low energyconsumption solid-state reaction. It uses metallic Zn as the negative electrode,a rod-like Na0.95MnO2fromtraditional solid-state reaction as the positiveelectrode, and an aqueous solution of0.5mol L-1Zn(CH3COO)2and0.5molL-1CH3COONa as the electrolyte. Its average discharge voltage is1.4V andthe energy density can have values of up to78Wh kg-1based on the twoelectrode materials. The system shows only8%capacity loss after1000fullcycles at a current rate of4C between1and2V.(2) Nanowire Na0.35MnO2was prepared by a simple and low energy consumptionhydrothermal method. When it is assembled into an asymmetric aqueoussupercapacitor, which average discharge voltage is0-1.8V, using activatedcarbon as the counter electrode and aqueous0.5molL-1Na2SO4electrolytesolution, the nanowire Na0.35MnO2shows an energy density of42.8Wh kg-1at apower density of108W kg-1based on the total weight of the two electrodematerial, higher than those for the rod-like Na0.95MnO2, with an energy densityof26Wh kg-1at a power density of84W kg-1. The new material presentsexcellent cycling behavior even when dissolved oxygen is not removed fromthe electrolyte solution and only4%after5000cycles.(3) Na0.35MnO2/CNT nanocomposite was prepared by a simple and low energy consumption hydrothermal method. When it is assembled into an asymmetricaqueous supercapacitor, which average discharge voltage is0-1.8V, usingactivated carbon as the counter electrode and aqueous0.5mol L-1Na2SO4electrolyte solution,. Na0.35MnO2/CNT shows an energy density of33.5Whkg-1at a power density of3kW kg-1based on the total weight of the twoelectrode material, higher than those for the Na0.35MnO2, with an energydensity of28.7Wh kg-1at a power density of3kW kg-1. The Na0.35MnO2/CNTnanocomposite presents excellent cycling behavior even when dissolved oxy-gen is not removed from the electrolyte solution after1000cycles.(4) Nanowire K0.19MnO2·0.2H2O was prepared by a hydrothermal method. Thesupercapacitor, which average discharge voltage is0-1.8V, based on activatedcarbon and nanowire K0.19MnO2·0.2H2O delivers an energy density41.3Whkg-1(based on the total mass of the active electrode materials) at a powerdensity of156.8W kg-1, higher than that based on activated carbon andK0.45MnO2·0.3H2O,28.4W h kg-1at a power density of115.1W kg-1. It pre-sents excellent cycling performance even when the oxygen in the aqueouselectrolyte is not removed, and there is less than5%fading after2500cycles.