Structural Designs And Electrochemical Performances Of Several Ternary Metal Oxides For Anode Materials Of Lithium Ion Batteries

Lithium-ion batteries have drawn considerable attention for researchers all around the world owing to their fascinating properties of high energy density, memory-free effect and long lifespan. In the last few decades, these energy systems have witnessed their significant advances and great potential in many applications, including smart grids, portable electronics, hybrid/pure electric vehicles, and other rechargeable eco-friendly electronic devices. The Cost, safety and energy density are some of the major issues in successfully adopting the lithium ion technology for transportation and stationary electrical energy storage, and these parameters are in turn linked to the electrode(anode and cathode) materials used. As one of the most important components in commercial LIBs, graphite is insufficient to serve as a next-generation anode material, due to its low capacities of 372 m A h g-1 and safety problems caused by the operation potential very close to that of a Li metal. Benefiting from their remarkable electrochemical properties, ternary metal oxides play significant roles for low-cost and environmentally-friendly energy storage/conversion technologies. However, its structural instability caused by huge volume changes during repetitive cycling has become a crucial obstacle for their further applications in lithium-ion batteries(LIBs). In this thesis, it is focused on the design and fabrication of ternary metal oxide with higher complexity in terms of structure and composition, hoping to achieve optimized physical/chemical properties for anode materials. The main work is divided into the following three parts.(1) Hierarchical hollow microflowers constructed from mesoprous single crystalline Co Mn2O4 nanosheets were synthesized by a solvothermal route followed by calcination in air. It was found that the amount of deionized water played a key role in the formation of the well-defined hierarchical hollow structures. Hierarchical hollow structures could be harvested with adding an appropriate amount of deionized water, however, lamellar morphology could be obtained in the absence of deionized water. In addition, a possible formation mechanism of the hierarchical hollow microflowers was proposed based on the time-dependent experimental results. In virtue of the unique structural advantages, these Co Mn2O4 hierarchical hollow microflowers show an excellent capacity of 915 m A h g-1 at a rate of 100 m A g-1. More significantly, Co Mn2O4 microflowers exibit superior electrochemical performances with a initial discharge specific capacity of 1024 m A h g-1 at 1000 m A g-1 and remain at 650 m A h g-1 with a coulombic efficiency of 98.7% after 500 cycles.(2) This article employes Zn(CH3COO)2·2H2O, Ge O2 and deionized water as raw materials, EDA and CTAB handononoas chelating agents and surfactant respectively, to prepare hierarchical Zn2 Ge O4 micro/nano materials via an one-step hydrothermal method. The crystalline phase and the morphology were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM), respectively. It was found that the concentration of ethylene diamine and CTAB had an important influence on the morphology of Zn2 Ge O4. The Zn2 Ge O4 microbundles could be obtained only with an appropriate concentration of ethylene diamine(0.16 mol) and CTAB(0.109 g). The electrochemical properties of Zn2 Ge O4 microbundles were evaluated by the LAND testing system. The samples exhibit a reversible specific capacity of 776 m A h g-1 after 60 cycles at a current density of 100 m A g-1 with a discharge/charge capacity of 1774/1107 m A h g-1.(3) Hollow Ni Co2O4 nanospheres were synthesized via a solvothermal route followed by calcination in air. The crystalline structures and morphology features were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, respectively. The hollow Ni Co2O4 nanospheres have a high crystallinity with an average diameter of 300 nm and the size of outer shell is about 30 nm. The hollow Ni Co2O4 nanospheres, when applied as a LIB anode material, possess a high discharge capacity of 1360 m A h g-1 and exhibit a long cycle life(585 m A h g-1after 250 cycles) at a rate of 1000 m A h g-1, corresponding to a high coulombic efficiency of 99%.