Preparation Of MnO₂ And CuO Micro/Nano-structureand Electrochemical Properties As Anode For Lithium-ion Battery

The working principle of lithium-ion battery, and the latest developments of cathode material and anode materials have briefly described in this paper. we summarize the working mechanism of the anode materials and figure out related issues of transition metal oxide as anode materials in lithium ion battery. Then, the relevant contact of morphology and electrochemical performance is studied after we obtain the core-shell materials.First of all, Two same type crystals with diffierent morphologies and particle size of Mn O2 are prepared by the hydrothermal method, and obtained the Cu O micro/nano material by oxidation reduction method, afterthat, we studied the influces on its electrochemical properties between different morphology and particle as electrode materials. Then, the conductive polymer polypyrrole(PPy) was prepared in the aqueous solution by chemical oxidation method, and explored polymerization conditions through the polymerization reaction temperature, concentration of oxidant and doping agent types and polymerization time and so on.Finally,core-shell structure composite materials was fabricated by using in situ polymerization under optimal conditions. for transition metal oxides Mn O2 coating processing(The transition metal oxides as the nuclear, conductive polymer polypyrrole as the shell). And the core-shell structure composite material was characterized and tested.In this study, Both the as-obtined α-Mn O2 exhibit promising electrochemical properties as the anode materials of rechargeable Li-ion batteries. In particular, the initial specific discharge capacity of caddice-clew-like and urchin-like Mn O2 are 1396 m Ah/g and 1407 m Ah/g at 0.2 C, respectively. After several cycles, the specific capacity are both more than 400 m Ah/g, which is more higher than that of graphite materials. As li-ion battery anode materials, the urchin-like Mn O2 micro/nano material has better electrochemical performance than caddice-clew-like Mn O2 material as a result of the relative high specific capacity and peak current in cyclic voltammetry. In addtion, the urchin-like Mn O2 material has lower impedance tested by electrochemical impedance spectroscopy. And the results indicate that the same crystal with different morphology of sample have different electrochemical properties, It means that the morphology of the sample have definitly effects on the electrochemical properties. the as-prepared three kinds of octahedral Cu O micro/nano particles by Oxidation-reduction method have different structures. All the three octahedral Cu O samples have high discharge specific capacity and good cycling stability from the 2nd to the 50 th cycling. The octahedral Cu O hollow crystals with 400 nm in size has the highest reversible capacity and the smallest resistance. So the electrochemical performances are partly related to their morphologies. The results show that the octahedral Cu O samples, especially the 400 nm Cu O crystals could be a promising material. The optimal preparation conditions of chemical oxidative polymerization of polypyrrole had been explored. To get the conductivity of polypyrrole material, the resistance of polypyrrole was measured by a multimeter. Research shows that that the influences on the conductivity of polypyrrole including the surfactant species, oxidants, polymerization time and polymerization temperature and so on. In this study, the optimal conditions for composite the conductive polypyrrole were as follows: using benzene sulfonic acid sodium as surfactant; Fe Cl3 as oxidant; the molar ratio of pyrrole monomer with surfactant was 3:1; the molar ratio of pyrrole monomer with oxidant was 1:3; and the reaction controlled during a ice-coldwater bathing(about 3~5 oC in Kunming) for 12 hours. Their discharge specific capacity and cycling stability of PPy/ Mn O2 indeed improved, When the Mn O2 materials coated with polypyrrole. The optimal volume of pyrrole coating for caddice-clew-like and urchin-like Mn O2 materails is respectively 75 u L and 30 u L. For 300 th times cycling of charge-discharge performance, the two PPy/Mn O2 materails have a significant improvement to the bare Mn O2 materails. It demonstates that the two PPy/Mn O2 materails can effectively improve the cycling stability. Before it, the electrochemical performance of urchin-like Mn O2 materails is better than caddice-clew-like Mn O2 materails in the 2nd to the 50 th cycling. But after coating with the polypyrrole, the caddice-clew-like material with PPy shell materials is more excellent.