尖晶石锰酸锂正极材料的合成条件的探索及其掺杂改性研究
发布时间：2018-08-20 08:31
【摘要】：尖晶石型LiMn2O4正极材料由于其环保程度、成本、原料来源、性能等多方面都具有一定优势而受到了科研工作者的广泛关注。然而,LiMn2O4材料本身存在Li+扩散速率小、电子电导率低与循环性能差等缺陷,其中循环性能差是限制其应用领域和范围的主要原因。为了进一步改善LiMn2O4正极材料的性能,本文在水热法结合高温固相法的基础上,采用阴阳离子协同掺杂的方法,制备出高性能材料,为促进LiMn2O4正极材料在工业化生产提供一些技术支持。1.采用水热法合成由细长棒状结构组成的球形MnO2。然后以MnO2作为前驱体,采用两步烧结方式合成球形形貌的LiMn2O4,研究温度和Li/Mn对材料微观形貌,晶体结构以及电化学性能的影响,确定最佳煅烧温度为500℃下煅烧6h,然后在750℃下煅烧18 h。2.通过扫描电镜(SEM)对MnO2进行了形貌分析,通过SEM、X射线衍射分析(XRD)、循环伏安测试(CV)和充放电测试对LiMn2O4和LiFe0.08Mn1.92O3.9F0.1进行了表征。结果表明Fe、F复合掺杂的Li Fe0.06Mn1.94O3.88F0.12材料具备规整的形貌、更稳定的晶体结构、良好的循环性能和倍率性能。0.2 C时LiFe0.06Mn1.94O3.88F0.12材料的首次放电比容量为133.6 mAh/g,电化学性能较好,而LiMn2O4仅为128.8 mAh/g。在0.5 C倍率下,LiFe0.06Mn1.94O3.88F0.12材料的首次放电比容量为121.6 mAh/g,而Li Mn2O4仅为117.7mAh/g,循环80次后,容量保持率分别为83.06%和77.57%。3.以水热合成的纳米球形MnO2作为模板,采用高温固相法合成球形形貌的LiMn2O4,LiMn1.94Fe0.06O4和LiNa0.06Mn1.94Fe0.06O4,通过X射线衍射分析(XRD)、SEM、EDS对三种材料进行物理表征。结果表明Na、Fe复合掺杂的LiNa0.06Mn1.94Fe0.06O4材料较稳定的晶体结构、颗粒尺寸较小(约160nm),掺杂的离子成功进入到晶格内。在0.5 C倍率下循环100次后,LiNa0.06Mn1.94Fe0.06O4放电比容量为108.0 mAh/g,而LiMn2O4仅为92.2 m Ah/g,容量保持率分别为74.12%和90.91%,在10 C时,LiNa0.06Mn1.94Fe0.06O4放电比容量比LiMn2O4高34.3mAh/g。进一步研究表明,Na、Fe复合掺杂对材料的锂离子扩散系数和电荷转移阻抗有着积极的影响。4.采取Zn单独掺杂和Zn、F双元素复合掺杂的方式,通过不同掺杂量的优化,得出最佳单一掺杂材料为LiMn1.97Zn0.03O4,其电化学性能与之前LiMn2O4材料相比有较明显的提高,具有更好的电化学可逆性与结构稳定性。LiMn1.97Zn0.03O3.92F0.08具有最佳的循环稳定性和倍率性能,其锂离子扩散系数高于纯LiMn2O4样品电极以及LiMn1.97Zn0.03O4材料。
[Abstract]:Spinel LiMn2O4 cathode materials have been widely concerned by researchers because of their advantages in environmental protection, cost, source of raw materials and properties. However, LiMn2O4 material has some defects such as low Li diffusion rate, low electronic conductivity and poor cycling performance, among which poor cycling performance is the main reason for limiting its application field and scope. In order to further improve the properties of LiMn2O4 cathode materials, based on hydrothermal method and high temperature solid state method, high performance materials were prepared by co-doping of anions and anions. In order to promote the LiMn2O4 cathode materials in industrial production to provide some technical support. 1. Spherical MNO _ 2 with slender rod structure was synthesized by hydrothermal method. Using MnO2 as precursor, limn _ 2O _ 4 with spherical morphology was synthesized by two-step sintering. The effects of temperature and Li/Mn on the microstructure, crystal structure and electrochemical properties of the material were investigated. The optimum calcination temperature is 500 鈩，
本文编号：2193024
[Abstract]:Spinel LiMn2O4 cathode materials have been widely concerned by researchers because of their advantages in environmental protection, cost, source of raw materials and properties. However, LiMn2O4 material has some defects such as low Li diffusion rate, low electronic conductivity and poor cycling performance, among which poor cycling performance is the main reason for limiting its application field and scope. In order to further improve the properties of LiMn2O4 cathode materials, based on hydrothermal method and high temperature solid state method, high performance materials were prepared by co-doping of anions and anions. In order to promote the LiMn2O4 cathode materials in industrial production to provide some technical support. 1. Spherical MNO _ 2 with slender rod structure was synthesized by hydrothermal method. Using MnO2 as precursor, limn _ 2O _ 4 with spherical morphology was synthesized by two-step sintering. The effects of temperature and Li/Mn on the microstructure, crystal structure and electrochemical properties of the material were investigated. The optimum calcination temperature is 500 鈩，
本文编号：2193024
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