Effects of carbon coating and iron phosphides on the electrochemical properties of LiFePO4/C
Effects of carbon coating and iron phosphides on the electrochemical properties of LiFePO4/C
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DOI：
10.1016/j.jpowsour.2008.03.026
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发表时间：
2008-10-01
影响因子：
9.2
通讯作者：
Pan, H. G.
中科院分区：
文献类型：
--
作者：
Lin, Y.;Gao, M. X.;Pan, H. G.
采用水溶胶-凝胶法在还原气氛下制备了不同含量的高电子导电磷化铁相的碳包覆LiFePO 4（LiFePO 4/C）。采用不同的合成工艺参数来调整产物的显微结构和相组成。通过0.1 ~ 5C（1C= 170 mAh g（-1））放电容量测试和循环伏安曲线分析，研究了碳包覆和磷化铁对LiFePO 4/C电极电化学性能的影响。结果表明，碳涂层的含量为1.5wt.%，以乙二醇为碳源，使LiFePO 4的粒径在比表面积上大幅度减小一个数量级，显著提高了LiFePO 4的倍率性能。在不同的放电速率下，FeP含量对碳包覆LiFePO 4的容量影响不同。将FeP的含量从1.2重量%增加到3.7重量%在低倍率（0.1C和1C）放电时，LiFePO_4/C的容量略有降低，但当放电倍率提高到5C时，LiFePO_4/C的容量明显增加。对于无碳样品，即使它也具有1.8重量%的FeP，但由于LiFePO 4的大颗粒尺寸和缺乏导电性，它仍然具有较差的容量。并且太多的磷化铁降低了电极的放电容量，因为它们对于锂离子的脱嵌/插入是惰性的。(c)2008 Elsevier B. V.保留所有权利。
Carbon coated LiFePO4 (LiFePO4/C) with different contents of high electron conductive iron phosphide phase was synthesized by an aqueous sol-gel method in a reductive sintering atmosphere. Different synthesis parameters were used for adjusting the microstructure and phase compositions of the products. The effects of the carbon coating and iron phosphides on the electrochemical properties of the LiFePO4/C electrodes were studied by means of testing the discharge capacities at rates of 0.1-5C(1C= 170mAh g(-1)) and analyzing the CV curves. The results show that carbon coating in a content of 1.5 wt.% derived from the carbon source of ethylene glycol greatly decreases the particle size of LiFePO4 in one order in the specific surface area, and significantly improves the rate capability of LiFePO4. The effect of the content of FeP on the capacity of the carbon coated LiFePO4 was different at different discharge rates. Increasing the content of FeP from 1.2 to 3.7 wt.% slightly decreases the capacity of LiFePO4/C at low discharge rate (0.1 C and 1C), but obviously increases the capacity of LiFePO4/C when the discharge rate is increased to 5C. For the carbon free sample, even it also has 1.8 wt.% FeP, it still possesses poor capacity due to the large particle size of LiFePO4 and the lack of conductivity. And too much iron phosphides lowers the discharge capacity of the electrode since they are inert for the deinsertion/insertion of lithium ion. (c) 2008 Elsevier B.V. All rights reserved.