Study Of Some Lithium Fast Ion Conductors And Cathode Materials Of Lithium Ion Batteries

Lithium-ion battery has drawn great attention due to its high voltage, high energy density, long cycle life, low self-discharge, non-memory effect and environmental friendliness. According to the development tendency of lithium-ion batteries and electrode materials, this thesis deals with the synthesis and characterization of a promising cathode material LiMn2O4 and solid electrolyte Li3x-yLa0.67-xTiO3 and LiTi2(PO4)3 that possesses high ionic conductivity together with a wide electrochemical window.A new lithium ion solid electrolytes of (Li3x-yLa0.67-x)1+z/2AlzTi1-zO3-yFy (x=0.11;0≤y≤0.05;0≤z≤0.05) prepared by high temperature (1200℃) solid state reaction and sol-gel method were characterized by several methods. Compared with those prepared by solid-state reaction, the reaction of sol-gel method will decrease the reaction temperature, cut down the reacting time. The results showed that the Al3+ and F- co-doped samples have a better conductivities and higher decomposition voltage compared with their parent materials. The maximum conductivity is 5.96×10-4s/cm at room temperature and 2.74×10-2s/cm at 573K for the initial composition of x=0.11, y=0.02 in (Li3x-yLa0.67-x)1+z/2AlzTi1-zO3-yFy (x=0.11 ;0≤y≤0.05;0≤z≤0.05) system, and its decomposition voltage reaches up to 2.65V.The preparation and characterization of Li1.3Al0.3Ti1.7(PO4)3 powders and sintered pellets derived by sol-gel method and solid-state reaction were carried out and comparatively studied. Compared with that prepared by solid-state reaction, the pellet prepared by sol-gel possesses higher ionic conductivity and lower activation energy.In order to stabilize the structure of spinal LiMn2O4 and improve its electro- chemical performance, a series of Li-ion battery cathode materials Li1+2x-yCoxNixMn2-2xO4-yFy (multi-doped by Co3+, Ni2+, F-) were prepared through co-precipitation technique, adulterating both Co3+ and Ni2+ ions and meantime introducing F-. The result indicated that the samples multi-doped by Co3+, Ni2+, F- kept the origin spinal structure. At a current density of 100mA/g...