Study On Dropped Modification Of Layered LiMnO₂ As Cathode Materials

Layered LiMnO2 has been widely used owing to its high theoretical capacity of 285mAh/g and low cost compared with LiCoO2, but it can't meet the requirement of the practical use as its poor cycle stability, which is a result of the Jahn-Teller distortion effect causing by tervalent manganese ion. Thus, many research groups have focused on the feasible techniques of preparation and the methods to enhance the cycle stability of layered lithium manganese oxide.In allusion to the problem of poor stability, the synthesis and electrochemistry of layered LiMnO2 with the raw materials of acetate manganese, acetate lithium, acetate cobalt, acetate lanthanum, lithium hydroxide and so on, by sol-gel process and hydrothermal synthesis is investagated. The results of XRD, SEM and electrochemical test (Electrochemical Impedance Spectroscope EIS, Cyclic Voltammetry CV, charge-discharge) show that a good single layered structure by adding rare earth elements is built up, and electrochemical performance has been noticeably improved, especially the 4% of La-doped materials made by sol-gel process, while the layered structure of the single-component doped material might change to spinel structure nonreversibly, and the capacity also decayed rapidly.To solve this problem, multi-element systems, ie, Cr/La, Ni/La, Ni/Co/La and Ni/Co/Ce are together introduced into the layered LiMnO2, and the influence of the different doping on the performance of the structure and stability of Cathode Materials. The results show that doping elements played a "supporting" role, restraining phase change, resulted in the great improvement of the cycling stability. At the same time, it is of the less obvious that the improvement on the stability of the layered material introducing the three-element systems by Hydrothermal Synthesis.