物理化学学报 >> 2013, Vol. 29 >> Issue (07): 1507-1514.doi: 10.3866/PKU.WHXB201304231

电化学和新能源 上一篇    下一篇

两步固相法合成LiFe1-xNbxPO4/C复合正极材料及其电化学性能

曹雁冰1,2, 罗亮1, 杜柯1, 彭忠东1, 胡国荣1, 姜锋2   

  1. 1 中南大学冶金科学与工程学院, 长沙 410083;
    2 中南大学材料科学与工程学院, 长沙 410083
  • 收稿日期:2013-01-18 修回日期:2013-04-19 发布日期:2013-06-14
  • 通讯作者: 彭忠东 E-mail:cybcsu@csu.edu.cn
  • 基金资助:

    国家科技支撑计划(2007BAE12B01); 中央高校基本科研业务费(2012QNZT018); 中国博士后科学基金(2012M521546)和中南大学博士后基金资助项目

Synthesis and Electrochemical Properties of LiFe1-xNbxPO4/C Composite Cathode Material by Two-Step Synthesis Route

CAO Yan-Bing1,2, LUO Liang1, DU Ke1, PENG Zhong-Dong1, HU Guo-Rong1, JIANG Feng2   

  1. 1 School of Metallurgical Science and Engineering, Central South University, Changsha 410083;
    2 School of Materials Science and Engineering, Central South University, Changsha 410083
  • Received:2013-01-18 Revised:2013-04-19 Published:2013-06-14
  • Contact: PENG Zhong-Dong E-mail:cybcsu@csu.edu.cn
  • Supported by:

    The project was supported by the National Key Technology R&D Program of China (2007BAE12B01), Fundamental Research Funds for the Central Universities, China (2012QNZT018), China Postdoctoral Science Foundation (2012M521546), and Postdoctoral Science Foundation of Central South University, China.

摘要:

以LiH2PO4和FeC2O4·2H2O为原料, 采用分步添加聚乙烯醇和葡萄糖两种碳源的方式, 通过两步固相法合成了碳包覆的LiFePO4材料. 700℃下处理的产物结晶良好, 颗粒分布均匀, 具有良好的电化学性能, 0.1C和1C倍率下放电比容量分别为157.3 和138.3 mAh·g-1. 在碳包覆的基础上, 选择高价Nb5+进行铁位取代获得了复合改性的LiFe1-xNbxPO4/C (x=0.005, 0.01, 0.015, 0.02)材料. 优化的LiFe0.99Nb0.01PO4/C 材料显示了良好的倍率充放电能力和循环稳定性, 0.1C和5C倍率下放电比容量分别为160.5 和136.0 mAh·g-1, 5C倍率下循环50 次后比容量保持在134.8 mAh·g-1, 容量保持率为99.1%. 循环伏安测试结果表明, Nb5+离子掺杂减少了锂离子扩散阻力, 降低了充放电过程中的动力学限制, 提高了电极的可逆性.

关键词: 聚阴离子型正极材料, LiFePO4, 两步固相法合成, Nb掺杂

Abstract:

LiFePO4/C composite was prepared by two-step synthesis route, with LiH2PO4 and FeC2O4· 2H2O as starting materials. In the process, the carbon sources polyvinyl alcohol (PVA) and glucose were added in a stepwise fashion. The well-crystallized LiFePO4/C composite with homogeneous small particles was obtained after reacting at 700℃ for 4 h. This composite had a discharge specific capacity of 157.3 mAh·g-1 at 0.1C rate and 138.4 mAh·g-1 at 1C rate. On the basis of carbon coating modification, Nb-ion-doped LiFe1-xNbxPO4/C (x=0.005, 0.01, 0.015, 0.02) composites were prepared. The optimized LiFe0.99Nb0.01PO4/C cathode displayed a discharge specific capacity 160.5 mAh·g-1 at 0.1C discharge rate, 136.0 mAh·g-1 at 5C and maintained 134.8 mAh·g-1 after 50 cycles, showing good rate properties and cycling stability. Cyclic voltammetry (CV) measurements indicated that aliovalent dopant substituting on the Fe sites can reduce the resistance of Li ion diffusion in the electrode process, increase phase transformation kinetics during cycling, and enhance the reversibility of LiFePO4 electrodes.

Key words: Polyanion cathode material, LiFePO4, Two-step synthesis, Nb doping

MSC2000: 

  • O646