Study On Synthesis And Performance Of The Novel LiMBO₃（M=Fe、Mn） Cathode Material For Lithium-ion Batteries

At first structural features, electrochemical performances and research status ofthe current hot lithium ion battery cathode materials were briefly introduced. Then theresearch focused on borate cathode materials, preliminary explorations of two-stepmethod, solvothermal method and polymer decomposition method were used in pre-paration of LiMBO3(M=Fe、Mn) cathode materials. And also on the basis of theLiFeBO3/C cathode material prepared by sol-gel method, LiFeBO3/LBO compositematerial was synthesized to improve their electrochemical properties. These experi-ments were prepared by differential thermal analysis (TG-DTA) to selecting appro-priate experimental temperature, using X-ray diffraction (XRD), scanning electronmicroscopy (SEM) measurements to characterizing the material structure and morpho-logy, and the charge-discharge test, cyclic voltammtry (CV), AC impedance methodto testing electrochemical properties of materials.Results showed that synthesis of LiFeBO3cathode material by two-step method,of which electrochemical performance was not ideal, the first discharge capacity ofthe material was only27mAh·g-1. Then LiFeBO3cathode material was synthesized bysolvothermal method, which showed that the results were also not satisfactory, thepreparation of the product contained many impurities. Synthesis of LiFeBO3/C andLiMnBO3/C cathode materials by polymer decomposition method, respectively ob-tained130mAh g-1and72mAh g-1of the first discharge capacity at C/20rate, butboth had a great capacity fade, after30cycles, respectively remained40mAh g-1and55mAh g-1of discharge capacity. Synthesis of LiMnBO3/C cathode materials by sol-gel method, obtained78mAh g-1of the first discharge capacity under the voltage of1.7~4.7V at C/20rate, but cycling performance was not satisfactory.Results showed that synthesis of LiFeBO3/LBO cathode material by sol-gel me-thod, within the voltage of1.5~4.5V at C/20rate charge-discharge test,115.5mAh g-1of the first discharge capacity had obtained, and cycling performance wasgood. when the LBO conductor material was doped with15.1wt%, which obtainedabout200mAh g-1of the first discharge capacity within the voltage of1.5~4.5V atC/20rate, and after30cycles, the discharge capacity remained at140mAh g-1. TheCV curve of the sample appeared on two obvious oxidation-reduction peak, illu-strated that Li+of LiFeBO3embedded emergence response in two steps maybe. Conductivity of the complex joined LBO had been improved significantly by ACimpedance testing. Ultimately have been improved the electrochemical properties ofthe material.