物理化学学报 >> 2012, Vol. 28 >> Issue (12): 2885-2892.doi: 10.3866/PKU.WHXB201209271

电化学和新能源 上一篇    下一篇

微米橄榄石型LiFePO4的水热合成优化

孙孝飞1,2, 徐友龙1,2, 刘养浩3, 李璐1,2   

  1. 1 西安交通大学, 电子陶瓷与器件教育部重点实验室, 西安 710049;
    2 西安交通大学, 国际电介质研究中心, 西安 710049;
    3 西安交通大学化学系, 西安 710061
  • 收稿日期:2012-07-03 修回日期:2012-09-07 发布日期:2012-11-14
  • 通讯作者: 徐友龙 E-mail:ylxu@mail.xjtu.edu.cn

Optimizing the Hydrothermal Synthesis of Micro-Sized Olivine LiFePO4

SUN Xiao-Fei1,2, XU You-Long1,2, LIU Yang-Hao3, LI Lu1,2   

  1. 1 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049, P. R. China;
    2 International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, P. R. China;
    3 Department of Chemistry, Xi’an Jiaotong University, Xi’an 710061, P. R. China
  • Received:2012-07-03 Revised:2012-09-07 Published:2012-11-14

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摘要：

为深入研究大颗粒磷酸铁锂(LiFePO4)锂离子电池正极材料的性能衰退机理并据此改善其体积能量密度和功率密度, 进而切实推进该材料在电动汽车、混合动力汽车和电站储能等领域的高效广泛应用, 本文通过优化水热合成条件制备了粒径为2 μm的均匀微米LiFePO4颗粒粉末. 在未经任何改性(包覆或掺杂)的情况下,该材料表现出本征大颗粒LiFePO4典型的充放电和循环性能, 可作为后续研究的代表样品进一步考察大颗粒材料相对纳米材料性能衰退的机制和根本原因, 最终通过有的放矢地改性手段获得高密度、高能量和高功率的LiFePO4 正极材料. 实验结果表明, 增加反应物浓度、水热温度和保温时间以及降低溶液pH 值均有利于LiFePO4颗粒的长大. 通过比较不同粒径的LiFePO4的电化学性能确证了其随颗粒尺寸的增大而衰退. 当颗粒大小由0.7 μm增加到16.5 μm时, LiFePO4在0.1C倍率下的放电比容量由152 mAh·g-1下降至80 mAh·g-1.同时, 1C倍率下的循环测试结果表明, 颗粒尺寸越大, LiFePO4的容量衰减愈严重.

关键词: 磷酸铁锂, 水热合成, 微米颗粒, 性能衰退, 正极材料, 锂离子电池

Abstract:

The low tap density of LiFePO4 is hindering the energy and power density of lithium-ion batteries in portable electronics, electric vehicles, and stationary electricity storage applications. As part of our work to investigate the pathological mechanism of performance degradation in large particle LiFePO4, micro-sized pristine LiFePO4 without modifications, such as surface coating or bulk doping, was first prepared hydrothermally by optimizing the synthesis parameters in this work. The influences of precursor concentration, solution pH, hydrothermal temperature, and heating time on the phase structure, particle size, and morphology of the products were systematically investigated. It was found that the particle size of LiFePO4 increases with decreasing pH value, increasing precursor concentration, increasing hydrothermal temperature, and increasing heating time during hydrothermal synthesis. The performance degradation of large particle LiFePO4 was demonstrated by these intrinsic samples. The specific discharge capacity decreased from 152 to 80 mAh·g-1 at 0.1C rate when the particle size was increased from 0.7 to 16.5 μm. Moreover, less capacities were retained after 100 cycles at 1C rate for larger particle materials. Finally, the optimized LiFePO4 with a distorted diamond shape was prepared for later investigation of the plausible mechanism of performance degradation in large particle LiFePO4. Its electrochemical performance was preliminarily discussed, and will need to be improved in future to obtain practical high energy/power density LiFePO4 cathodes for lithium-ion batteries.

Key words: Lithium iron phosphate, Hydrothermal synthesis, Micro-sized particles, Performance degradation, Cathode material, Lithium-ion battery