改性锰氧化物作为锂离子电池负极材料的研究

发布时间：2018-03-06 22:04

  本文选题：二氧化锰　切入点：二氧化钛　出处：《南京大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,随着石油、天然气等传统化石能源日渐枯竭,太阳能、风能等新能源受到越来越多的关注。这些替代能源的高效利用仰赖于高性能化学电源的发展。而锂离子电池是目前研究和应用最广泛的化学电源之一。与其它化学电源相比而言,锂离子电池具有能量密度高、使用寿命长、循环性能好、安全性能好等优点,现已经广泛应用于笔记本电脑、数码相机、移动电话等移动设备中。然而目前锂离子电池的电化学性能还不能满足纯电动汽车(EVs)或混合动力汽车(HEVs)等大功率设备的需求。作为锂离子电池三大基本要素(正极、负极、电解质)之一的负极材料一直是锂离子电池研究的关键课题。锰的氧化物由于具有较高的比容量,很早就将其作为储锂负极材料进行研究。然而,由于其电子传导率和锂离子扩散速率较低,且充放电过程中体积易发生不可逆的变化,导致材料的粉化,使得容量衰减较快,循环能力和快速充放电能力差,因此制约了锰氧化物在锂离子电池负极材料领域中的应用。本论文的研究内容是针对锰氧化物的上述不足,利用二氧化钛修饰及掺氮等手段对锰氧化物进行改性,以提高材料的导电性和锂离子在材料中的扩散速率,减缓材料因体积变化造成的粉化现象,达到提升电化学性能的目的。1.通过水热方法制备MnCO_3自组装微球,在空气气氛中400 ℃焙烧4 h后氧化为MnO_2,然后加入钛酸四丁酯水解,通过后期再烧结过程后生成TiO2/MnOx复合材料。与二氧化锰相比,复合材料容量衰减较慢,循环能力大幅提升,在100 mA/g下经过250次循环后比容量保持在1032 mAh/g。性能的提高可能源于二氧化钛结构的稳定性部分缓解了锰氧化物的体积膨胀,Mn~(3+)的存在使得导电性提高,以及二氧化钛和氧化锰间的协同作用。7Li核磁共振的结果证明了复合物中二氧化钛储锂的嵌入机理及锰氧化物储锂的转化机理。2.通过硝酸锰和乙醇的水热反应在三聚氰胺泡棉上生成三氧化二锰颗粒,管式炉下烧结后泡棉分解为碳氮网络结构,三氧化二锰还原为低价态的一氧化锰。由于碳氮网络结构的存在,提高了充放电过程中材料结构的稳定性及电子的传输效率,烧结后产生了电荷传输的孔道结构,材料的比容量和循环稳定性大大提高。经500℃处理后的MnO-MF-500材料在160次循环后仍然保留590 mAh/g的比容量,达到一氧化锰理论容量755 mAh/g的78%。
[Abstract]:In recent years, with oil, natural gas and other traditional fossil energy increasingly depleted, solar energy, New energy sources, such as wind energy, have attracted more and more attention. The efficient use of these alternative sources depends on the development of high performance chemical power sources. Lithium ion batteries are one of the most widely studied and widely used chemical power sources. In comparison with power supply, Li-ion batteries have the advantages of high energy density, long service life, good cycle performance, good safety performance, and have been widely used in notebook computers, digital cameras, etc. However, the electrochemical performance of lithium-ion battery can not meet the demand of high-power equipment such as pure electric vehicle (EVs) or hybrid electric vehicle (HEVs) at present. As the three basic elements of lithium-ion battery (positive electrode, negative electrode, and so on), the electrochemical performance of lithium-ion battery can not meet the demand of high-power equipment such as pure electric vehicle or hybrid electric vehicle. Because of its high specific capacity, manganese oxide has been used as a cathode material for lithium storage in a long time. However, because of its high specific capacity, manganese oxide has been used as a cathode material for lithium-ion batteries. Due to the low electron conductivity and lithium ion diffusion rate, and the irreversible change of the volume during charge and discharge, the material becomes powdered, which makes the capacity decay faster, and the cycling ability and rapid charge and discharge ability are poor. Therefore, the application of manganese oxide in the field of anode materials for lithium ion batteries is restricted. In order to improve the conductivity of the material and the diffusion rate of lithium ion in the material, to reduce the powder phenomenon caused by the volume change of the material and to improve the electrochemical performance. 1. The MnCO_3 self-assembled microspheres were prepared by hydrothermal method. After calcined at 400 鈩，

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