摘要
本文以FeSO_4、H_3PO_4和LiOH为原料,采用超临界水热过程制备了亚微米级LiFePO_4颗粒.在此基础上,为了提升制备的LiFePO_4正极材料的物理和电化学性能,对其进行了后续煅烧碳包覆改性研究.同时,通过XRD、SEM、充放电测试、CV和EIS测试手段,对LiFePO_4正极材料改性前后的结构、形貌和电化学性能进行了表征.结果表明:后续固相煅烧碳包覆改性能够显著改善LiFePO_4的结晶性能,减小颗粒粒径,降低电荷传递阻抗,以及大幅度地提升放电容量和循环性能;以PVP为模板剂、蔗糖为碳源,700℃煅烧1 h得到的LiFePO_4/C颗粒粒径小、分布均一,室温0.2 C倍率的首圈放电比容量为153.1 mAh/g,1 C倍率充放电时,放电比容量可保持在144.2 mAh/g,1 C循环50次,容量保持率达到97.1%.
Pure sub-micro LiFePO4 particles were prepared via supercritical hydrothermal process using FeSO4, H3PO4 and LiOH as raw materials, and as-prepared LiFePO4 was calcined and carbon-coated to further promote its physical and electrochemical properties. The structure, morphology and electrochemical performance of LiFePO4 were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, charge and discharge test, cyclic voltammetry （CV） and electrochemical impedance spectra （EIS）. The results show that calcination and carbon-coating can effectively improve the crystallization property, decrease the particles size, charge the transfer resistance, and enhance the electrochemical performance of LiFePO4. The LiFePO4/C composites with small particle size and uniform structure were obtained with polyvinyl pyrrolidone （PVP） as template and sucrose as carbon source under the conditions of 1 h calcination at 700 ℃. The initial discharge capacity was 153.1 mAh/g and 144.2 mAh/g at 0.2 C and 1 C, respectively. After 50 cycles, 97.1% of the initial discharge capacity was retained at 1 C rate.
出处
《材料科学与工艺》
EI
CAS
CSCD
北大核心
2017年第2期74-78,共5页
Materials Science and Technology
基金
国家自然科学基金资助项目(21106010
21376035)
关键词
超临界水热
磷酸铁锂
固相煅烧
碳包覆
supercritical hydrothermal
LiFePO4
calcination
carbon-coating
