LiFePO_4的制备及其充放电过程中的结构演变和性能研究  

Preparation of LiFePO_4 and Its Structure Change and Performance Study in the Charge-discharge Cycles

作　　者：陈召勇[1] 张建利[1] 朱华丽[1] 邓雅平[1] 朱伟[1] 

机构地区：[1]长沙理工大学物理与电子科学学院,湖南长沙410114

出　　处：《合成化学》2009年第4期422-427,共6页Chinese Journal of Synthetic Chemistry

基　　金：湖南省教育厅青年基金资助项目(06B002);湖南省科技计划资助项目(2008FJ3008);长沙理工大学青年基金资助项目(1004085)

摘　　要：分别以FeC2O4.2H2O(a),Fe2O3(b)和Fe3O4(c)为铁源,采用高温固相法制备了3种LiFePO4(LFP)(简称LFPa,LFPb和LFPc)。采用碳包覆法制备了LFPa～LFPc的锂离子电池正极片(LFPA～LFPC)。用X-射线衍射仪(XRD)分析了铁源对其结构的影响和充放电过程中的结构演变;用循环伏安法(CV)和交流阻抗法(EIS)对锂离子脱嵌动力学作了初步探讨。XRD分析结果表明,LFPa～LFPc均具有单一的橄榄石结构。LFP在循环过程中结构基本稳定,结晶度有所降低。充放电测试表明,LFPA～LFPC在0.2C倍率下首次放电比容量分别为130mA.h.g-1,147mA·h·g-1和152mA·h·g-1。其中LFPA拥有较好的倍率性能;CV和EIS研究发现,LFPA在充放电过程中极化小,可逆性好。Three LiFePO4 （LFP） （ LFP^a- LFP^c ） were prepared by high temperature solid state method using FeC2O4 - 2H2O（a） , Fe2O3 （b） and Fe3O4 （c） as the iron sources, respectively. Lithium ion battery positive materials （ LFP^A - LFP^C ） were prepared from LFP^a - LFP^c by carbon-coated method. The structures were characterized by X-ray diffraction （XRD）, and the diffusion dynamic character of lithium ion was analyzed by means of cyclic voltammetry （CV） and electrochemical impedance spectroscopy（EIS）. XRD results indicated that LFP^a -LFP^c had the single olivine phase. During the course of continuous charging and discharging, the structure of LFP was basically stable, but the crystallinity declined. The charge-discharge tests showed that the initial discharge capacity of LFP^A -LFP^C were 130 mA· h · g^-1, 147 mA ·h · g^-1 and 152 mA · h· g^-1, respectively at the rate of 0.2C. And LFPA had a better rate performance. CV and EIS studies showed that LFPA had smaller polarization and better reversibility in the process of charge-discharge.

关 键 词：磷酸铁锂 正极材料 锂离子电池 交流阻抗 

分 类 号：O614[理学—无机化学]