化学学报 ›› 2012, Vol. 70 ›› Issue (03): 223-228.DOI: 10.6023/A1107201 上一篇    下一篇

研究论文

Na 掺杂对LiFePO4/C 复合正极材料的结构和倍率性能的影响

陆晓挺, 李东林, 樊小勇, 赵鹏, 苟蕾, 李严, 李倩, 王静   

  1. 长安大学材料科学与工程学院 长安大学能源材料与器件研究所 西安 710064
  • 投稿日期:2011-07-20 修回日期:2011-09-28 发布日期:2011-10-27
  • 通讯作者: 李东林 E-mail:dlli@chd.edu.cn
  • 基金资助:

    国家自然科学基金(Nos. 20903016, 21073021, 21103013)、教育部高等学校科学技术重大项目培育资金项目(No. 708084)和中央高校基本科研业务费专项资金(Nos. CHD2010ZD008, CHD2010JC006, CHD2011ZD007)资助项目.

Study on Structure and Rate Performance of LiFePO4/C Composite Cathode Material via Na Doping

Lu Xiaoting, Li Donglin, Fan Xiaoyong, Zhao Peng, Gou Lei, Li Yan, Li Qian, Wang Jing   

  1. Laboratory of Energy Materials and Devices, School of Materials and Engineering, Chang’an University, Xi’an 710064
  • Received:2011-07-20 Revised:2011-09-28 Published:2011-10-27
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 20903016, 21073021, 21103013), Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (No. 708084), Fundamental Research Funds for the Central Universities (Nos. CHD2010ZD008, CHD2010JC006, CHD2011ZD007).

以Fe(NO3)3, LiNO3, NH4H2PO4 和NaNO3 为原料, 采用简单的液相-碳热还原法合成Li0.97Na0.03FePO4/C 复合正极材料. 使用X 射线衍射(XRD)、扫描电子显微镜(SEM)和充放电等测试技术研究了材料的结构及倍率充放电性能. 通过循环伏安(CV)曲线和电化学阻抗谱(EIS)研究电极反应过程中的动力学特点. 结果表明, Na 掺杂形成了具有橄榄石结构的Li0.97Na0.03FePO4 固溶体, 并增大了晶格中Li+一维扩散通道, 使LiFePO4/C 的电荷转移电阻减小了约2/3, Li+扩散系数提高了3~4 倍. 因此, Li0.97Na0.03FePO4/C 首次放电比容量在0.1 C 和2 C 倍率下分别达到152 mAh·g-1 和109 mAh·g-1,比未掺杂的LiFePO4/C 的放电比容量分别提高了4.83%和62.69%.

关键词: 锂离子电池, LiFePO4, Na 掺杂, 锂离子扩散系数, 倍率充放电

Li0.97Na0.03FePO4/C composite cathode material was prepared by a simple wet chemistrycarbothermal reduction method using Fe(NO3)3, LiNO3, NH4H2PO4 and NaNO3 as starting materials. The structure and charging-discharging rate properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and charge-discharge test. Furthermore, the kinetics of lithium-ion extraction and insertion at LiFePO4/C were evaluated from cyclic voltammetry (CV) curves and electrochemical impedance spectroscopy (EIS). The results indicate that the Li0.97Na0.03FePO4 solid-solution with olivine structure is obtained. Na-doping enlarges one-dimensional lithium-ion diffusion pathway in the olivine structure. Consequently, the materials exhibit a decrease in the charge transfer resistance by 67% and an increase in the lithium-ion diffusion coefficient by 3 ~ 4 times. The initial discharge capacities of Li0.97Na0.03FePO4/C sample at the rate of 0.1 C and 2 C are 152 mAh·g-1 and 109 mAh·g-1, respectively, which increase 4.83% and 62.69% compared with that of un-doped LiFePO4/C.

Key words: lithium-ion battery, LiFePO4, Na doping, lithium-ion diffusion coefficient, rate charge-discharge