Preparation And Properties Of TiO₂/MoS₂ Composite Anode Materials For Lithium Ion Batteries

With the development of the electric vehicle market, lithium-ion batteries are required for higher performances. Carbonaceous anode materials cannot meet the needs of the market because of its serious safety problems and rate capability. In contrast, TiO₂ anode materials get attention for their superior safety performance, cycle stability and rate capacity due to their higher work voltage and stable structures. In this thesis, to further improve the electrochemical properties of TiO₂ anode materials, the nanotechnology and composite technology are utilized. First, three kinds of different structures of nano TiO₂ were prepared. Then, the TiO₂/MoS₂ anode materials composited with the three kinds of TiO₂ and MoS₂ nanosheet are studied. The main contents and results are as follows:（1） Preparation and electrochemical properties of TiO₂ nanoparticles/MoS₂ nanosheets composite materials.First of all, MoS₂ nanosheets and TiO₂ nanoparticles were prepared by lithium ion intercalation and hydrothermal method, respectively. Then, through disperse agitating, the two nanometerials were recombined due to van der Waals forces. Next, the phase, morphology and electrochemical properties of the TiO₂/MoS₂ composite and pure TiO₂ nanoparticles were characterized. The results show that the discharge specific capacity of the composite material （mass ratio is 2:1） is 149.5 mAh/g at 500 mA/g after 50 cycles, which is increased 20.6% compared to pure TiO₂. Its discharge specific capacity is 62.3 mAh/g in the ultrahigh current density of 8 A/g which is 1.56 times of pure TiO₂.（2） Preparation and electrochemical properties of TiO₂ nanowires/MoS₂ nanosheets composite materials.First of all, TiO₂ nanowires were prepared by electrospinning. Then, MoS₂ nanosheets were prepared by hydrothermal method on TiO₂ nanowires surface to obtain TiO₂ nano wires/Mo S₂ nanosheets composites. Next, the phase, morphology and electrochemical properties of the TiO₂/MoS₂ composite （mass ratio is 1:1） and pure TiO₂ nanowires were characterized. The results show that discharge specific capacity of the composite material at 500 mA/g after 50 cycles is 1.28 times of the pure TiO₂; in the rate performance tests, the discharge specific capacity is 43.5 mAh/g at 4 A/g, which is 1.23 times of pure TiO₂.（3） Preparation and electrochemical properties of TiO₂ nanowire arrays/MoS₂ nanosheets composite materials.First of all, TiO₂ nanowire arrays were prepared by hydrothermal method with different annealing temperature on titanium foil surface. Then, MoS₂ nanosheets in TiO₂ nanowire arrays were prepared through hydrothermal method. And TiO₂ nanowire arrays/MoS₂ nanosheets composites were obtained, finally. The phase, morphology and electrochemical properties of TiO₂ nanowire arrays and TiO₂/MoS₂ composites materials were characterized. The results show that discharge specific capacity retention of TiO₂-700℃/MoS₂ at 100 mA/g after 100 cycles is 2.76 times of the TiO₂-700℃ under the same condition, and the discharge specific capacity of TiO₂-700℃/MoS₂ is increased 100% at 4 A/g. Moreover, TiO₂ nanowires array/MoS₂ nanosheets composites has the most excellent electrochemical performance compared with TiO₂ nanoparticles/MoS₂ nanosheets and TiO₂ nanowires/MoS₂ nanosheets composite materials, the discharge specific capacity of TiO₂-500oC/MoS₂ is 223.4 mAh/g at 100 mA/g after 100 cycles, and the discharge specific capacity is 76.2 mAh/g at 8 A/g.