The Study Of Manganese/Nickel-based Metal Oxides As Anode Materials Of Lithium Ion Battery

With the ever-growing energy consumption and environmental pollution, there has been an ever increasing and urgent demand for environmentally friendly high-power energy resources. Lithium-ion batteries (LIBs) have become one of the most promising alternative sources due to many outstanding features including high energy density, no memory effect, long lifetime, and little self-discharge. LIBs have gained dominance in the market of many portable electronic devices. However, the demand for powering electric vehicles requires significant improvements in the high rate performance. The high reactivity and favorable charge transport due to the novel structure of nanomaterials make them suitable to effeetively improve the performance of lithium batteries. In this thesis, we synthesized several unique nanostructured metal oxides as the anode material of LIB. Their morphologies and electronic structure are characterized by XRD、SEM and TEM and their electrochemical properties as the anodes of LIBs were evaluated by charge-discharge test.MnO2 nanotubes were prepared by a hydrothermal method, which is a hollow tubular structure with a length of 1-2 um and diameter of around 100 nm. Then SnO2-MnO2-SnO2 composite was synthesized at room temperature, with SnO2 nanoparticles embedded in and decorated on MnO2 nanotubes. MnO2-Co3O4 composite was synthesized at elevated temperature, with CO3O4 nanoparticles dispersed on the surface of MnO2 nanotubes. Then three nanostructures as anode electrodes were cycled at 0.2C to evaluate their electrochemical properties. The results indicate that SnO2-MnO2 composite can delivery a capacity over twice that of pure MnO2. The capacity of MnO2-Co3O4 composite is a little higher than that of pure MnO2.Self-assembly flower-like nickel oxide nanostructure was synthesized by one-step hydrothermal method. The mechanism of the hierarchical structure was probed by changing reaction time. It is found that only the thickness of nanosheet increased with the increase of the reaction time and the morphology did not change. We also discovered that dispersive hexoganol NiO nanoplates can be obtained by grounding and dispersing the flower-like structure of NiO.NiO-Co3O4 nanocomposite was fabricated in a similar hydrothermal process, in which the 2D NiO nanoplates were synthesized firstly and then the OD CO3O4 nanoparticles were decorated on NiO nanoplates. It can be clearly seen that numerous CO3O4 nanoparticles are distributed uniformly on the surface of each NiO nanoplate. Cyclic voltammetry measurements and galvanostatic charge-discharge experiments were carried out to test the electrochemical performances of hierarchical MO-CO3O4 nanocomposite. The MO-CO3O4 composite exhibits a stable discharge capacity of about 633 mA h g-1 at a current density of 100 mA g-1 after 70 cycles, much higher than the building block alone. Even after charge-discharge at 1000 mA g-1, the NiO-CO3O4 electrode is still able to deliver a reversible capacity of～650 mA h g-1 at a current density of 100 mA g-1, indicating that the electrode has good cycling stability. The outstanding performance of the NiO/CO3O4 nanocomposite is attributed to the hierarchical structure and the synergistic effect of different components. This method perhaps open a new way for the fabrication of hierarchical structured materials with primary nanoscale building blocks and secondary architecture anode with good electrochemical performance for the next generation of LIBs.