具有微纳结构的铁基负极材料的制备及其储锂性能研究

发布时间：2018-04-11 14:12

本文选题：花状铁醇盐 + 微纳结构　；参考：《河南师范大学》2017年硕士论文

【摘要】：锂离子电池铁基负极材料以其理论比容量高、储量大、环境友好、成本较低等特点受到广泛地关注。但是,其自身电导率不高以及在充放电过程中体积变化较大使得材料的倍率性能较差并且长期循环时容量衰减严重。纳米材料具有较大的比表面积,因而具有特异的化学和物理性能,一直是研究的焦点之一。用作负极的纳米材料可以有效缩短质荷传输距离,提高电化学反应以及缓冲锂离子嵌/脱时产生的应力,因而使得纳米负极材料成为研究热点。为了改善铁基负极材料的电化学性能,人们合成了一些具有特殊形貌的纳米材料,包括纳米线、纳米针、纳米棒、空心纳米球、纳米管等。但是这些材料的后期加工性能不如微米材料好(如制备负极浆料);另外作为负极材料充放电时表面形成电子绝缘的固体电解质界面膜(SEI膜),使得孤岛状的颗粒之间的导电性能不佳。本文以具有花状微纳结构的铁醇盐为反应中间体,在一定气氛下烧结制备相应形貌的铁基负极材料(FeS2、Fe2O3、Fe3O4)。一方面,铁醇盐的纳米片可以降低烧结温度,从而使得产物保持中间体的形貌;另一方面,具有微纳结构的负极材料,既拥有纳米材料的优点,同时具有微米颗粒的良好加工性能。因此,所制备的材料表现出较大的比容量和良好的循环性能。具体研究内容如下:(1)具有微纳结构的FeS2合成及其储锂性能研究:将具有花状微纳结构的铁醇盐放入管式炉中,在N2和H2S混合气氛下分别在300、450和800 oC热处理得到产物。结构和形貌结果表明300 oC热处理得到的样品是FeS2并能够充分保持铁醇盐中间体的形貌,结晶度较高。450 oC热处理得到的样品也是FeS2,但表面变成多孔状结构,结晶度更高。800 oC热处理得到的样品却是Fe9S10,并且不再具有铁醇盐的形貌,XRD图谱的信噪比明显下降。电化学测试结果显示,在200 mA g-1放电倍率下300 oC时的产物具有1484.3 mAh g-1的放电比容量,高于450和800 oC的产物(1326.7 and 934 mAh g-1);另外,100次充放电循环后(200 mA g-1)300 oC产物的放电比容量为480.8 mA h g-1,远高于另外两个样品放电比容量(215.8和89.7 mAh g-1)。(2)具有微纳结构的Fe2O3合成及其储锂性能研究:将具有花状微纳结构的铁醇盐放入马弗炉中,空气气氛下分别在300、450和800 oC热处理,得到Fe2O3负极材料。结构与形貌结果表明300 oC热处理时产物能够充分地保持铁醇盐中间体的形貌,结晶度较高。450 oC热处理的产物表面形成多孔状结构,结晶性更好,但信噪比稍微降低;800 oC的产物不再具有铁醇盐中体间的形貌,XRD的信噪比明显下降。电化学测试结果表明,200 mA g-1的电流密度下300 oC热处理产物的首次放电比容量为1360.2 mAh g-1,稍低于450和800 oC热处理的产物(1411.6和1429.8 mAh g-1);但是100次充放电循环后300 oC的产物放电比容量为515.6 mAh g-1(200 mA g-1),远高于另外两个样品的放电比容量(247.6和206.7 mA h g-1),表现出了较好的循环性能。(3)具有微纳结构的Fe3O4合成及其储锂性能:将具有花状微纳结构的铁醇盐放入管式炉中,氮气气氛下分别在300、450和800 oC热处理,得到铁的氧化物。结构表征结果显示300 oC热处理的产物为Fe2O3,而450和800 oC热处理的产物为Fe3O4。450 oC热处理的产物能够充分地保持铁醇盐中间体的形貌,结晶度较高。800 oC热处理得到的Fe3O4不再保持铁醇盐中间体的形貌。电化学测试结果表明,虽然200 mA g-1倍率下450oC产物的首次放电比容量(1050.7 mAh g-1)稍低于800 oC产物的(1159.3 mAh g-1),但是100次充放电循环后放电比容量为505.2 mA h g-1(200 mA g-1),远高于800 oC产物的比容量(140.3 mAh g-1),表现出较好的循环性能。
[Abstract]:In order to improve the electrochemical properties of iron - based negative electrode materials , nano - materials with special morphology have been synthesized , including nanowires , nano - needles , nanorods , hollow nano - spheres , nanotubes , etc . The results show that the samples obtained by heat treatment at 300 oC are FeS2 and have good processability . The results show that the samples prepared by heat treatment at 300 oC are FeS2 , and the results show that the samples obtained by heat treatment at 300 oC have higher specific capacity and good cycle performance . The results show that the samples obtained by heat treatment at 300 oC are FeS2 , and have higher crystallinity . The discharge specific capacity of the products at 300 oC is 480.8 mA h g - 1 after 100 charge / discharge cycles , which is much higher than that of the other two samples ( 215.8 and 89.7 mAh g - 1 ) . ( 2 ) Fe _ 2O _ 3 synthesis with micro - nano structure and its lithium storage performance : The iron alkoxide with flower - like micro - nano structure was put into muffle furnace and heat treated at 300 , 450 and 800 oC in air atmosphere to obtain Fe2O3 negative electrode material . The results showed that the first discharge specific capacity of the product was 1360 . 2 mAh g - 1 , slightly lower than 450 and 800 oC ( 1429 . 8 mAh g - 1 ) . However , the discharge specific capacity of the product at 300 oC after 100 charge / discharge cycles was 515.6 mAh g - 1 ( 200 mA g - 1 ) , which was much higher than that of the other two samples ( 247.6 and 206.7 mA h g - 1 ) . ( 3 ) Fe3O4 synthesis with micro - nano structure and its lithium storage performance : The iron alkoxide with flower - like micro - nano structure was put into a tubular furnace . The iron oxide was obtained by heat treatment at 300 , 450 and 800 oC in nitrogen atmosphere . The results showed that the first discharge specific capacity ( 105.7 mAh g - 1 ) of 450 and 800 oC heat treatment was slightly lower than that of 800 oC product ( 1159.3 mAh g - 1 ) , but the discharge specific capacity after 100 charge / discharge cycles was 505.2 mA h g - 1 ( 200 mA g - 1 ) , which was much higher than that of 800 oC product ( 140.3 mAh g - 1 ) .

【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;O646

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