| Rechargeable lithium-ion batteries (LIBs), as one of important electrical energy storage technologies, have attracted extensive attention for large-scale applications in electric vehicles, portable electronic devices (such as mobile phones, cameras, and laptops) and etc. Carbonaceous material graphite, as the main commercialized anode material for LIBs, has low lithium storage capacity (372 mAh g-1) and is far from the demands of high energy storage devices. Transition metal oxides (MxOy,) have been investigated as desired candidates for anode materials, because they deliver significantly higher electrochemical capacities compared with graphite anodes. Among of them, Mn-based oxide and hematite Fe2O3 (a-Fe2O3) have been defined as promising LIB anode materials due to their advantages of natural abundance, low toxicity, low cost and low operating voltage. However, the implementation of transition metal oxides in rechargeable LIBs is still largely hampered by some practical problems, such as poor electronic conductivity and poor cycling performance. The electrochemical performance of the electrode materials could be enhanced by combination of single metal oxides or lattice doping using other transition metal ions. This dissertation mainly deals with two aspects, shown as below.(1) Pure-phase ZnMnO3 have been prepared through the thermal decomposition of Zn-Mn binary carbonate precursors facilely co-precipitated at room temperature, possessing spherical shape with an average diameter of 1.2±0.3 μmn and acquiring porosity with a specific surface area of 24.3 m2 g-1. When applied as lithium-ion battery anodes for the first time, these porous spherulites deliver an initial discharge capacity of 1294 mAh g-1 at 500 mA g-1 and retain an reversible value of 879 mAh g-1 over 150 cycles. By comparison, the lithium storage capability of the equimolar powder mixture of nano-sized ZnO and MnO2 synergistically is higher than that of the two unary transition metal oxides, but lower than which of the as-prepared anode material ZnMnO3. The superior electrochemical performance of well-crystallized ZnMnO3 can be ascribed to its nanostructured characteristics and an inner atomic synergistic effect within the cubic lattices.(2) Initial oxalate co-precipitation at room temperature and subsequent thermal decomposition were combinedly used for the controlling syntheses of various levels of Mn-doped α-Fe2O3 possessing a shape of hollow quadrangular prism with porous shell. When applied as lithium-ion battery anodes, Mn-doped α-Fe2O3 exhibits an improved electrochemical performance compared with undoped α-Fe2O3 and the Mn-doped product of Fe1.7Mno.3O3 is superior. At a current density of 200 mA g-1, pure α-Fe2O3 electrode delivers an initial discharge capacity of～1280 mAh g-1 and the capacity decrease to ～178 mAh g-1 over 80 cycles, while the Mn-doped product of rhombohedral Fe1.7Mn0.3O3 delivers a relatively low initial value of～1190 mAh g-1 and retains the 80th reversible capacity of～1000 mAh g-1. Apparently, the introduction of manganese is conductive to improving the electrochemical cycling stability of iron oxide. |
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