The Synthesis And Electrochemical Researches Of Li-ion Cathode Materials Via Liquid Crystal Template Pathway

LiMnPO4 and LiMnPO4/C were successfully synthesized with a facile hydrothermal process via cholesteryl caprylate(C35H60O2)liquid crystal-assisted routine in this dissertation.The structures and morphologies were characterized through X-ray diffraction,X-ray photoelectron spectroscopy,scanning electron microscopy and transmission electron microscopy.The electrochemical performances of LiMnPO4 and LiMnPO4/C were investigated by cyclic voltammetry,charge-discharge and alternating current impedance test.As-prepared orthorhombic LiMnPO4 presents a large number of selectively exposed(020)planes and minimizes the paths for Li diffusion.The ordered LiMnPO4/C possess the higher rate and cycling performances with a specific discharge capacity of 156 mAh g-1 at 0.1 C,and the remained capacity of 145 mAh g-1 after 100 cycles.These excellent results show that cholesteryl caprylate liquid crystal plays a crucial role in forming the structure with more active(020)planes for efficient Li+ extraction and insertion.The agaric-like structured LiNii/3Co1/3Mni/3O2 cathode material with the selectively exposed {010} planes is prepared via liquid crystal structure-template pathway.The agaric-like structured LiNii/3Coi/3Mni/3O2 exhibits stable performances and fast kinetics for Li transmission.According to the EIS and electrochemical performance tests' results,the agaric-like structured LiN1/3Co1/3Mn1/3O2 has better ionic conductivity and electrochemical performances.As-prepared LiNi1/3Co1/3Mn1/3O2 delivers high discharge capacity(187.3 mAh g-1)at 0.1 C and 132 mAh g-1 at a rate of 5 C,which indicates that the agaric-like structure improves the charge-discharge,cycling and rate performances.In conclusion,cholesteryl caprylate involves the preparation and growth of those composites,which presents the modulation of structure as the template.Slight additive amount benefits the growth of(020)and {010} planes for LiMnPO4 and LiNi1/3Coi/3Mni/3O2,respectively.This novel method provides a feasible way to the synthesis,modification and research of the lithium-ion battery cathode material in the future.