LiFePO 4C体相复合正极材料的制备与性研究.docx

ABSTRACTOlivine—type ABSTRACT Olivine—type LiFeP04 has been attracted particular attention due to the high safety，the inexpensive price and the relative lace of toxicity．The olivine LiFeP04 was prepared from(NH4)2Fe(S04)2‘6H20、LiOH·H20 and H3P04 by low temperature CO—precipitation process followed by heat treatment． The theory of low temperature co-precipitation has been studied in this work．The results showed that the LiFeP04 precursor synthesized iS comprised of amorphors LiFeP04，Fe3(P04h。8H20，Li3P04’2H20，Li2S04 and(NH4)aS04．The reactions of co-precipitation are as follows： (NH4)2Fe(S04)2+3LiOH+H3P04=Li2S04+(NH4hS04+ 1／3 Fe3(P04)2,L+1／3Li3P04,[ H3P04+Li十+30H一+Fe2十=LiFeP04I+3H20 The effects of washing conditions on synthesizing the LiFeP04 precursor were researched．The results showed that．the saturated Li3P04 solution can prevent the Li3P04 contained in the precursor from dissolving． The effect of heattreatment temperature、time on the electrochemical performance of the layered materials was investigated．The sample prepared at 700。C for 1 5h has small particle sizes and exhibited a good initial discharge specific capacity． Based on the LiFeP04 problems of of low electronic conductivity and low lithium diffusivity,the effects of the addition of different carbon sources and different methods were studied to synthesize LiFeP04／C powders．The results showed that：1)the samples synthesized with several different methods were all pure olivine—type LiFeP04；2)the sample synthesized from C12H1206 or C12H2201 1 has excellent electrochemical performance；3)the sample synthesized by adding C6H l 206 during CO—precipitation has the smallest particle size and the best electrochemical performance with initial discharge specific capacity of 1 52 mAh·g。1 at current density of 0．1 C． Key words：cathode material；LiFeP04；carbon—coated 原创性声明本人声明，所呈交的学位论文是本人在导师指导下进行的研究 原创性声明 本人声明，所呈交的学位论文是本人在导师指导下进行的研究 工作及取得的研究成果。尽我所知，除了论文中特别加以标注和致谢 的地方外，论文中不包含其他人已经发表或撰写过的研究成果，也不 包含为获得中南大学或其他单位