Cao Yanbing

微波合成法制备锂离子电池正极材料Li 2 FeSiO 4

We report a novel synthetic route for the preparation of the Li2FeSiO4 cathode material by microwave processing. The Li2FeSiO4 material was synthesized using mechanical ball-milling and subsequent microwave processing. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical methods. Properties of the prepared materials and electrochemical characteristics of the samples were investigated and compared to samples prepared by the conventional solid-state reaction. The obtained results indicated that highly pure Li2FeSiO4 material with uniform and fine particle size was quickly and successfully synthesized by microwave (MW) heating at 650 ℃ for 12 min. This compound showed high specific capacity and good cycle ability. The initial discharge capacity of the sample obtained by MW heating delivered 119.5 mAh•g^(-1) at 60 ℃ at a current density of C/20 rate (1C=160 mA•g^(-1)). After 10 cycles the discharge capacity maintained 116.2 mAh•g^(-1). The Li2FeSiO4 material displayed higher phase purity, better microstructure, and better electrochemical properties than the sample prepared by the conventional solid-state method.

微波辅助固相法合成锂离子电池正极复合材料Li 2 FeSiO 4 /C

以Na 2 SiO 3 ·9H 2 O和FeCl 2 ·4H 2 O为原料, 采用低热固相反应获得了分散均匀的β-FeOOH/SiO 2 前驱体; 再以Li 2 CO 3 为锂源、聚乙烯醇和超导电炭黑为复合碳源, 通过微波辅助固相法合成了Li 2 FeSiO 4 /C材料. 通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和恒电流充放电测试等方法对材料的结构、微观形貌及电化学性能进行表征. 650℃下微波处理12 min可获得结晶好、晶粒细小均匀的Li 2 FeSiO 4 /C材料; 在选用的微波合成体系下, 超导碳和聚乙烯醇热分解的无定形碳不仅利于合成反应的顺利进行, 而且提高了Li 2 FeSiO 4 的整体导电性能. 制备的复合正极材料在60 ℃下0.05 C 倍率首次放电容量为129.6 mAh/g, 0.5 C 倍率下为107.5 mAh/g, 0.5 C 下15次循环后保持为104.8 mAh/g, 具有较好的放电比容量和良好的循环稳定性能. 结果表明, 微波辅助固相合成工艺是制备Li 2 FeSiO 4 /C复合材料的一种很有前景的方法.以Na 2 SiO 3 ·9H 2 O和FeCl 2 ·4H 2 O为原料, 采用低热固相反应获得了分散均匀的β-FeOOH/SiO 2 前驱体; 再以Li 2 CO 3 为锂源、聚乙烯醇和超导电炭黑为复合碳源, 通过微波辅助固相法合成了Li 2 FeSiO 4 /C材料. 通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和恒电流充放电测试等方法对材料的结构、微观形貌及电化学性能进行表征. 650℃下微波处理12 min可获得结晶好、晶粒细小均匀的Li 2 FeSiO 4 /C材料; 在选用的微波合成体系下, 超导碳和聚乙烯醇热分解的无定形碳不仅利于合成反应的顺利进行, 而且提高了Li 2 FeSiO 4 的整体导电性能. 制备的复合正极材料在60 ℃下0.05 C 倍率首次放电容量为129.6 mAh/g, 0.5 C 倍率下为107.5 mAh/g, 0.5 C 下15次循环后保持为104.8 mAh/g, 具有较好的放电比容量和良好的循环稳定性能. 结果表明, 微波辅助固相合成工艺是制备Li 2 FeSiO 4 /C复合材料的一种很有前景的方法.

Synthesis of LiFePO 4 Cathode Materials by Mechanical-Activation-Assisted Polyol Processing

A low-temperature approach for efficient preparation of LiFePO4 was developed. The rod-shaped [Fe3(PO4)2·8H2O + Li3PO4] precursor was prepared, using a mechanochemical liquid-phase activation technique, from LiH2PO4 and reduction iron powder. Pure LiFePO4 was then synthesized in boiling tetra(ethylene glycol) (TEG) by polyol processing with the as-prepared precursor. In order to improve the electrical conductivity, carbon coating of the pure LiFePO4 was carried out, using poly(vinyl alcohol) (PVA) as the carbon source. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS). The results show that well-crystallized LiFePO4 was successfully synthesized by polyol processing at low temperature. Carbon coating significantly improves the conductive properties of LiFePO4 and reduces charge-transfer impedance. The obtained LiFePO4/C composite delivers specific discharge capacities of 139.8 and 129.5 mAh·g-1 at 1C and 2C rates, respectively, displaying good cycling performance and rate capability.