模板法可控构筑锰酸锌负极材料及其电化学储锂性能研究

发布时间：2018-01-26 14:32

本文关键词： 锰酸锌模板法锂离子电池负极储锂性能　出处：《安徽工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：锂离子电池(LIBs)能量密度高,循环寿命好,工作电压高、能量密度高,是目前作为二次电池中应用最为广泛的产品。为了适应动力电池发展的需要,锂离子电池负极材料是LIBs重要的一个组成,目前受到了广泛的关注。锂离子电池负极材料过渡金属氧化物来源广泛,且具有很高的理论比容量,被众多研究人员所青睐。锰酸锌(ZnMn_2O_4)作为过渡金属氧化物中的一员,具有过渡金属氧化物所有优点,但是鉴于过渡金属氧化物的一些缺点,如导电性较差;在锂离子的嵌/脱出的过程中,易造成材料的体积发生一定改变,引起结构性坍塌;制约了其在锂离子电池的电化学性能的展现,本文通过对ZnMn_2O_4负极材料结构的优化设计,为离子,电子传输提供更为丰富的活性位点,提高了其导电性,优化了其结构稳定性,以此来获得高性能的LIBs负极材料。具体研究内容如下:(1)以氧化石墨烯(GO)为模板合成超薄MnO_2纳米片,在室温中利用一步快速还原生成超薄的ZnMn_2O_4纳米片,方法非常的简便,具有普适性。并探究了超薄ZnMn_2O_4的形成机理和电化学性能。超薄ZnMn_2O_4纳米片缩短了电子/离子的传输路径,提升了电极的离子导电性,对于应力具有很好的缓冲效果,有助于提高其材料的结构稳定性,使得超薄ZnMn_2O_4纳米片表现出了优秀的电化学储锂性能。通过电化学测试结果可以看出,在高倍率1 C(784 mA/g)条件下,该超薄ZnMn_2O_4纳米首次放电比容量高达1353mAh/g,经过100周循环后后,超薄的ZnMn_2O_4纳米片依然保有510 mAh/g的容量,表现出超薄ZnMn_2O_4纳米片非凡的循环稳定性、倍率性能和库伦效率。(2)利用生物质材料棉花为模板,通过浸渍,煅烧,成功合成了多层次ZnMn_2O_4微米带。由于棉花本身的特殊性能具有很强的吸附能力,在浸渍过程中大量锌锰离子均匀的被棉花纤维吸附。在随后煅烧的过程中随着有机物质和碳材料被慢慢氧化,棉花纤维状形貌很好的被保持,最终形成由大量带状结构交织于一起的独特三维网络结构。此种结构对应力具有很好的缓冲作用,能够有效的抵御结构的坍塌,增加电极电解液接触面积,有助于离/电子的传输,提高材料的导电性。通过对其物性表征以及电化学性能的表征可以看到其表现了优异的电化学性能,在200 mA/g电流密度下首次放电容量为1090 mAh/g,1000 mA/g大电流密度下,循环350圈之后容量依然可以保持在409 mAh/g远高于石墨负极材料的理论容量。表现出了十分优异的电化学性能。(3)以碳布为模板形成MnO_2@Carbon cloth(后文简称MnO_2@CC),再以此为基础进行牺牲模板法最终形成了一维管状中空ZnMn_2O_4,我们对此材料进行了各种物性及电化学性能表征。通过测试发现,一维管状中空ZnMn_2O_4微管是由很多纳米颗粒和纳米片相互交织,最终形成疏松多孔的管状结构。首先一维结构因其独特的形态有利于离/电子的传导,有助于提高材料的离电子导电性。其次中空结构具有一定的应力缓冲作用,可以一定程度的缓冲体积变化对结构带来的不利影响。而且结构中的纳米颗粒、片状结构缩短了电子传导路程,提高了材料的导电性。通过电化学测试结果可以看出,在电流密度100 mA/g条件下,其放电比容量为585 mAh/g。当电流密度达到2000 mA/g时,其放电容量仍可达到272 mAh/g,实验表明一维管状中空ZnMn_2O_4具有很好的电化学性能表现。除了对于其电化学性能的表征以外,我们还发现了一些有趣的现象。原本碳布纤维在很高温度下依然可以很好的保持它的形貌,在锰离子的加入后在较低的温度下碳布纤维就被煅烧去除了。说明锰离子对于石墨化程度很高的碳热解具有一定的催化效果。
[Abstract]:Lithium ion batteries (LIBs) high energy density, long cycle life, high working voltage, high energy density, is two times as the most widely used battery products. In order to meet the needs of the development of power battery, lithium ion battery anode material is an important component of LIBs, there has been widespread concern. Anode materials for lithium ion batteries of transition metal oxides originates widely, and has very high theoretical capacity, is favored by many researchers. Manganese zinc (ZnMn_2O_4) as a member of transition metal oxides, transition metal oxides has all the advantages, but because of some disadvantages of transition metal oxides, such as poor conductivity; lithium ion intercalation / extraction process, easy to cause the volume of the material changed, causing structural collapse; which show the electrochemical performance of lithium ion battery, based on ZnMn_2O_4 Optimization design of anode material structure for ion, electron transport provide more active sites for the rich, improve its conductivity, optimizing its structure stability, in order to obtain LIBs anode materials with high performance. The specific contents are as follows: (1) to graphene oxide (GO) template for synthesis of ultrathin MnO_2 nanosheets the use of ZnMn_2O_4, nano step fast reduction of generation ultra-thin at room temperature, the method is simple, it is universal. And to explore the formation mechanism and electrochemical properties of ultrathin ZnMn_2O_4. Ultrathin ZnMn_2O_4 nanosheets can shorten the transmission path from the electronic / sub, enhance the ionic conductivity of the electrode, the stress is a good cushioning effect, help to improve the structural stability of the material, the ultrathin ZnMn_2O_4 nanosheets exhibit excellent electrochemical lithium storage performance. The electrochemical test results showed that, in the high rate of 1 C (78 4 mA/g) under the condition of the ultra-thin nano ZnMn_2O_4 the first discharge capacity is up to 1353mAh/g, after 100 cycles, nano ZnMn_2O_4 thin still retains a capacity of 510 mAh/g, showing ultrathin ZnMn_2O_4 nanosheets extraordinary rate performance and cycle stability, Kulun efficiency. (2) the use of biomass materials of cotton as template and through the impregnation, calcination, successfully synthesized hierarchical ZnMn_2O_4 microbelts. Due to the special properties of cotton itself has a strong adsorption capacity, in the impregnation process of large quantities of zinc manganese ion by uniform cotton fiber adsorption. In the subsequent calcination process with organic matter and carbon materials are slowly oxidized cotton fiber like morphology good is maintained, eventually formed a unique three-dimensional network structure composed of a large number of banded structure interwoven together to. The structure stress has good buffer function, can effectively resist structure collapse Collapse, increasing the electrode electrolyte contact area, help from / electronic transmission, improve the conductivity of the material. By the characterization and electrochemical characterization see demonstrates its excellent electrochemical performance, under the current density of 200 mA/g the first discharge capacity of 1090 mAh/g, 1000 mA/g high current density, after 350 cycles the capacity can still maintain a theoretical capacity of 409 mAh/g is much higher than that of graphite electrode. Exhibit excellent electrochemical performance. (3) with carbon cloth as template form MnO_2@Carbon cloth (hereinafter referred to as the MnO_2@CC), and then as a basis for the sacrifice template eventually formed a one-dimensional tubular hollow ZnMn_2O_4, we this material has a variety of characterization and electrochemical performance. Through the test found that the one-dimensional tubular hollow ZnMn_2O_4 microtubules are composed of many nano particles and nano films are intertwined, eventually forming The tubular porous structure. Firstly, one-dimensional structure because of its unique form to leave / electron transfer, help to improve the material from the electronic conductivity. Secondly the hollow structure has certain stress buffering effect, can buffer the volume change of a certain degree of structure caused by the adverse effects of nanoparticles and structure. The lamellar structure reduces the electron conduction distance, improve the conductivity of the material. The electrochemical test results show that the current density of 100 mA/g, the discharge capacity is 585 mAh/g. when the current density reaches 2000 mA/g, the discharge capacity can reach 272 mAh/g, experiments show that the one-dimensional tubular hollow ZnMn_2O_4 with electrochemical properties a very good performance. In addition to the characterization of its electrochemical performance, we also found some interesting phenomena. The original carbon fiber cloth under very high temperature can still very OK, keep its shape. When the manganese ion is added, the carbon fiber will be calcined and removed at lower temperature. This indicates that manganese ion has certain catalytic effect for carbon pyrolysis with high graphitization degree.

【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB383.1

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