碳包囊过渡金属氧化物的制备及储锂性能研究

发布时间：2018-04-20 22:08

本文选题：锂离子电池 + 负极材料　；参考：《天津工业大学》2017年硕士论文

【摘要】：由于氧化钴和三氧化二铁具有高的理论比容量、丰富的来源和环境友好等特点已成为锂离子电池负极材料研究的热点。但是由于它们的导电性差,首次库伦效率低,循环性能差等缺点,限制了其广泛的应用。因此,在保持高容量的条件下,提高氧化钴和三氧化二铁材料的导电性,抑制其在充放电过程中出现的体积膨胀、颗粒团聚以及活性材料粉化等问题是解决上述缺陷的有效途径。本文以EDTA-2Na为碳源和氮源,合成出具有良好的循环性能和倍率性能的锂离子电池负极材料。具体的研究内容如下:采用EDTA-Fe为前驱体制备出碳包囊纳米尺度γ-Fe2O3纳米粒子(Fe2O3@NC)。研究结果表明,尺寸大小约23nm的γ-Fe2O3晶粒均匀分散在碳基质中。电化学测试结果显示,该复合电极材料在100 mA/g的电流密度下,经过50次循环,库仑效率高达98%,可逆比容量保持为487 mAh/g,容量保持率为71%;在1600 mA/g的电流密度下,可逆比容量保持有100 mAh/g,当电流密度恢复至50 mA/g时,放电比容量仍然可以快速恢复至585 mAh/g。Fe2O3@NC复合材料表现出如此优异的电化学性能可归因于Fe2O3@NC复合材料的介孔结构以及氮掺杂的碳材料,这可以提高锂离子脱嵌过程中γ-Fe2O3的导电性和结构稳定性。采用EDTA-Co为前驱体制备出碳包囊金属钴及氧化钴复合材料(CoOx@C)。电化学测试结果表明,该复合电极材料在100 mA/g的电流密度下,经过50次循环,库仑效率高达99%,可逆比容量保持为407 mAh/g,容量保持率为86%;在1600mA/g的电流密度下,复合电极的可逆比容量高达120 mAh/g,当电流密度恢复至50 mA/g时,放电比容量仍然可以迅速恢复至411 mAh/g。CoOx@C表现出如此优异的电化学性能,这可以归因于以下特性:一、高导电性金属Co颗粒不仅作为导电剂增加复合材料的导电性,也作为有效催化剂促使SEI膜组分可逆转化,从而提高复合电极的储锂能力和倍率性能。二、氮掺杂的碳材料增大了复合材料的导电性,抑制了氧化钴纳米颗粒的团聚,从而提高了复合材料的循环性能。
[Abstract]:Due to its high theoretical specific capacity, abundant source and environment-friendly characteristics, cobalt oxide and iron trioxide have become a hot spot in the research of cathode materials for lithium ion batteries. However, due to their poor conductivity, low efficiency of the first Coulomb and poor cycle performance, their wide applications are limited. Therefore, under the condition of maintaining high capacity, the electrical conductivity of cobalt oxide and ferric oxide is improved, and the volume expansion of cobalt oxide and ferric oxide is restrained in the process of charging and discharging. The agglomeration of particles and the pulverization of active materials are effective ways to solve these defects. In this paper, EDTA-2Na is used as carbon source and nitrogen source to synthesize cathode materials for lithium ion batteries with good cycling performance and rate performance. The main contents of this study are as follows: using EDTA-Fe as precursor, nano-sized 纬 -Fe _ 2O _ 3 nanoparticles were prepared. The results show that 纬 -Fe _ 2O _ 3 grains of about 23nm size are uniformly dispersed in carbon matrix. The electrochemical test results show that the Coulomb efficiency is up to 98 at 100 mA/g current density, the reversible specific capacity is 1600 mg / g, the capacity retention is 71%, and at 1600 mA/g current density, the Coulomb efficiency is as high as 98%, and the reversible specific capacity is 487mAh-1 路g, and the capacity retention is 71g at the current density of 1600 mA/g. The reversible specific capacity remains at 100mAh / g, and when the current density returns to 50 mA/g, The discharge specific capacity can still be rapidly recovered to 585 mAh/g.Fe2O3@NC composites. The excellent electrochemical performance can be attributed to the mesoporous structure of Fe2O3@NC composites and nitrogen doped carbon materials. This can improve the conductivity and structural stability of 纬 -Fe _ 2O _ 3 in the process of lithium ion deintercalation. Carbon capsule cobalt and cobalt oxide composites were prepared by using EDTA-Co as precursor. The electrochemical test results show that the Coulomb efficiency is as high as 99mh / g, the reversible specific capacity is 407mAh/ g and the capacity retention rate is 86g under the current density of 100 mA/g, and at the current density of 1600mA/g, the Coulomb efficiency is as high as 99mg / g, and the reversible specific capacity is 407mAh/ g. The reversible specific capacity of the composite electrode is as high as 120mAh/ g. When the current density is restored to 50 mA/g, the discharge specific capacity can still be rapidly recovered to 411 mAh/g.CoOx@C, showing such excellent electrochemical performance, which can be attributed to the following characteristics: 1. High conductivity Co particles not only increase the conductivity of composite materials as conductive agents, but also promote the reversible conversion of SEI film components as effective catalysts, thus improving the lithium-storage capacity and the performance of the composite electrodes. Secondly, nitrogen doped carbon increases the electrical conductivity of the composites and inhibits the agglomeration of cobalt oxide nanoparticles, thus improving the cyclic properties of the composites.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332;TM912

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