Study On The Novel Cathode Materials For Li-Ion Batteries And The Trial-Assembling Of High-Power Li-Ion Batteries

The main content of this thesis includes three parts: Preparation, studies on the structure and electrochemical performance of spinel LiMn2O4 doped with Al; Preparation of LiNi_xCo_yMn_1-x-yO₂ with co-deposition and high temperature solid reaction, influence by Co,Mn content variety; the trial-assembling of 18650 Li-ion batteries for high-power with LiMn_2-xAl_xO₄ as cathode materials, test its cycle, rate abilities and safety.In order to improve its electrochemical performance,we prepare LiMn₂O₄ doped with Al. SEM show that LiMn_2-xAl_xO₄ has integrity spinel crystal. Its grain diameter d50=12.5μm, surface area=0.3 m2/g. Powder X-ray diffraction (XRD) indicates that spinel is the only detected phase in Al-debased LiMn₂O₄.ICP datas testify that the content of Al is accurate. Compared with pristine spinel LiMn₂O₄, modification improves the cycling stability and rate capability of the material. The improved electrochemical performance of spinel LiMn2-xAlxO4is attributed to the entrance of Al³⁺ into the spinel crystalline structure.Layered LiNi_xCo_yMn_1-x-yO₂ cathode materials have gradually been the studying focus as cathode materials used in new generation lithium ion batteries since Ohzuku and J. R. Dahn first put forward the compounds as cathode materials for lithium ion batteries. These materials with standard layered structure and excellent electrochemical performance have been prepared by microemulsion and high temperature solid reaction. The structures and appearance of the layered materials have been characterized by XRD and SEM et. al. The materials with different properties may be prepared by changing the proportion of Ni, Mn and Co.The capacity and rate capability of materials can be improved by increasing the content of Co. The ratio of Mn can influence the charge voltage.We assemble high-power 18650 Li-ion batteries with LiMn2-xAlxO4 as cathode and MCMB as anode. The batteries pass all the safe tests and show good rate capability.