【作者】 黄卫；

【导师】 司鹏超；

【作者基本信息】 山东大学 ， 材料加工工程， 2017， 硕士

【摘要】 锂离子电池作为一种能源存储和转换装置,是新能源开发和可持续利用的重要组成部分之一,极大地促进了人民生产生活方式的改变和社会的发展。然而,随着经济和社会的不断发展,当前对锂离子电池的能量密度、循环性能、倍率性能以及安全性提出了更高的要求。因此研发新型电极材料,寻找具有高功率密度和高能量密度的新型锂离子电池电极材料是迫不及待的。过渡金属化合物具有优秀的储锂潜能,从而具有实际应用的重要研究价值,其中以过渡金属元素铁组成的化合物得到了广泛的研究。然而到目前为止,铁基化合物电极材料并没有得到大规模的实际应用,主要原因是其材料本身导电性差以及充放电过程体积膨胀过大造成材料的破坏。所以纳米工程化当前的铁基化合物或者加入一些导电性强的物质形成复合材料能改善铁基化合物本身的导电性,缓解电极材料的体积膨胀,从而增强其电化学性能。本论文中通过有目的地设计和表征,控制合成了两种铁基化合物碳纳米复合材料,深入研究了两种纳米复合材料制备过程中的反应机理、复合材料的物相结构和微观形貌。通过恒电流充放电测试、循环伏安测试等手段对其电化学性能进行了测试考察并优化实验方案,最终获得了高比容量、循环倍率性能优秀的新型电极材料。具体研究内容如下:1.石墨烯包覆Fe₃O₄纳米棒自组装介孔杂化复合物作为高性能锂离子电池负极材料。通过一种两步法简单合成含有75%Fe₃O₄纳米棒和25%rGO介孔杂化复合物,这种复合材料通过表征确定在rGO和金属氧化物之间存在共价键作用,金属氧化物纳米棒被rGO所包裹,同时自组装成一种整体的层状连续介孔结构。这种材料已经作为锂离子电池负极通过系统地测试,循环250圈之后在500 mAg^-1下放电比容量达到1053 mAh g-1,在1000-5000 mAg^-1高电流密度下具有788-541mAhg^-1的优秀的倍率性能。2.金属有机框架衍生硫化铁-碳核壳纳米棒作为转换型电池材料。通过使用温和的一步固相法硫化一种铁基金属有机框架前驱体合成核壳纳米结构的C@Fe₇S₈纳米棒复合物。该复合物由13%的碳和87%的Fe₇S₈形成层状连续多孔结构。当用于组装转换型锂离子电池时,这种复合物材料在500mAg^-1的电流密度下循环170圈后放电比容量为1148mAhg^-1,同时在2000 mAg^-1高电流密度下放电比容量为657mAhg^-1。更多还原

【Abstract】 Lithium-ion battery is one of the important components as energy storage and conversion devices for new energy development and sustainable utilization,which has been greatly promoted the transformation of life style and social development.However,with the rapid development of economy and society,higher requirements are necessary for the current lithium-ion battery,such as energy density,cycle performance,rate performance and safety and so on.Therefore,it is essential to develop new electrode materials for lithium-ion battery with high power and energy density.Transition metal compounds have superior potential for lithium-ion storage for practical application.Among the compounds of transition metal elements,iron based composites have been widely studied.However,iron-based electrode materials have not been large-scale practically applied due to its own poor conductivity and crack from volume expansion during cycling process.So nanoengineering of the current iron-based compounds or adding some strong conductive materials to improve the conductivity of iron-based composites and buffer the volume expansion of materials for enhanced electrochemical performance.Herein,two iron-based carbon nanocomposites were designed and synthesized.We have carefully investigated the reaction mechanism,morphology and microstructure of iron-based carbon nanocomposites.We also investigated the electrochemical performance by galvanostatic charge/discharge and cyclic voltammetry test.Finally,we fabricated new electrode materials with high specific capacity,superior cycle and rate performance by optimizing the experimental procedures.Detailed contents are as follows:1.In this work,we have demonstrated a two-step procedure for the facile synthesis of mesoporous hybrids comprised of 75%Fe₃O₄a nanorods and 25%reduced graphene oxide.The structural features of this composite are characterized by the covalent bonding between the rGO sheets and metal oxide,wrapping metal oxide nanorods by rGO sheets and hierarchical self-assembly into robust mesoporous ensembles.The material has been systematically tested as an lithium-ion battery anode component.A high reversible capacity of 1053mAhg^-1 subjected to 250 charge-discharge cycles at 500mAg^-1 was achieved,accompanied by an excellent rate capability with the deliverable energy of 788-541 mAhg^-1 upon the application of high current densities of 1000-5000mAg^-1.2.In this work,we have successfully synthesized the core-shell nanostructured C@Fe₇S₈ nanorods using a facile one-pot process by exploiting solid-state chemical sulfurizing of an iron-based MOF precursor.The resulting core-shell nanorod is composed of approximately 13%carbon and 87%Fe₇S₈ with a hierarchically porous structure.When assembled redox conversion-type lithium-ion battery,this composite material has demonstrated high lithium-ion storage capacity of 1148 mAhg^-1 under the current rate of 500mAg^-1 for 170 cycles and an impressive retention capacity of 657 mAhg^-1 with a current density of 2000 mAg^-1.更多还原