新型磷酸盐类钠离子电池正极材料的研究

发布时间：2018-02-08 23:51

本文关键词： 能源存储钠离子电池正极材料电化学性能　出处：《华中科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：在众多储能技术中，二次电池在能源存储和转化方面具有重要意义。锂离子电池目前占据了便携式移动电子设备的主要市场，而且正在向混合电动汽车市场方向飞速发展，这将导致锂的需求量将大大增加，然而地球上锂的资源非常有限，基于这种现状和需求，储量丰富的钠进入了人们的视野，钠与锂位于同一主族，具有相似的化学性质，Na+/Na电对具有-2.71V的标准电极电势，其理论比容量为1166mAh/g。钠元素在地壳中的含量远远高于锂，，而且海洋中含有大量的钠，钠的提炼比较简单。所以，钠离子电池是一种非常有前景的新型储能技术。本文主要以Na4Co3(PO4)2P2O7和Na3V2(PO4)3两种钠离子电池正极材料为研究对象，用溶胶凝胶法制备了Na4Co3(PO4)2P2O7/CNTs，并对其作为钠离子电池正极材料时的电化学性能进行了表征。结果表明碳纳米管能够在活性材料中能够形成一种连续导电网络大大增加了Na4Co3(PO4)2P2O7的导电性，其可逆容量分别为1C时,80mAh/g；5C，60mAh/g；10C，40mAh/g；20C，30mAh/g，且有较好的循环性能。分别用固相法和模板法合成了Na3V2(PO4)3/C复合材料，并研究了合成条件对材料结构和形貌的影响。通过X-射线衍射(XRD)和场发射扫描电子显微镜(FESEM)对结构和形貌表征，结果表明在固相法合成中，800oC保温10h可以得到结晶性好的Na3V2(PO4)3/C复合材料，而降低合成温度，或缩短保温时间，得到的材料不纯或结晶度较差；在模板法合成中，650oC保温12h可以得到具有多孔的三维碳骨架结构的Na3V2(PO4)3/C复合材料，而延长保温时间到14h或提高处理温度到800oC得到的材料三维骨架结构坍塌。模板法合成了Na3V2(PO4)3/C复合材料，并通过热失重分析(TG)，拉曼光谱，场发射扫描电子显微镜(SEM)，透射电镜(TEM)，X射线衍射(XRD)，循环伏安测试，恒流充放电等测试手段对其结构和性能进行了表征。结果表明：Na3V2(PO4)3/C复合材料在1C,2C,5C,10C,20C和50C不同放电倍率下进行恒流充放电测试,放电容量分别达到113mAh/g,100mAh/g,77mAh/g,70mAh/g，62mAh/g和58mAh/g，同时库伦效率接近100%，而且以1C和2C放电倍率循环100圈，容量基本没有衰减，表现出了极佳的循环稳定性。
[Abstract]:Among many energy storage technologies, secondary batteries play an important role in energy storage and conversion. Lithium ion batteries occupy the main market of portable mobile electronic devices, and are developing rapidly towards hybrid electric vehicle market. This will lead to a huge increase in the demand for lithium, but the resources of lithium on Earth are very limited, and because of this status quo and demand, the abundant sodium has come into view, and sodium and lithium are in the same dominant group. The Na / Na pair has a standard electrode potential of -2.71V with a theoretical specific capacity of 1166mAh / g. The content of sodium in the earth's crust is much higher than that of lithium, and the ocean contains a lot of sodium, so the extraction of sodium is relatively simple. Sodium ion battery is a promising new energy storage technology. In this paper, two kinds of cathode materials of sodium ion battery, Na4Co3(PO4)2P2O7 and Na3V2(PO4)3, are studied. Na4Co3P2O2P2O7 / CNTswere prepared by sol-gel method, and their electrochemical properties were characterized when they were used as cathode materials for sodium ion batteries. The results show that carbon nanotubes can form a continuous conductive network in the active materials, which greatly increases the conductivity of Na4Co3(PO4)2P2O7. Its reversible capacity is 80mAh/ g ~ (5) C ~ (60) mg / g ~ (10) C ~ (10) C ~ (10) C ~ (10) C ~ (20) C ~ (20) C ~ (20) C ~ (20) C ~ (-) ~ (30) mg / g ~ (-1), and it has good cycling performance. Na3V2(PO4)3/C composites were synthesized by solid phase method and template method, respectively. The effects of synthesis conditions on the structure and morphology of the composites were studied. The structure and morphology of the composites were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results show that Na3V2(PO4)3/C composites with good crystallinity can be obtained by holding for 10 h in the solid phase synthesis process. However, when the synthesis temperature is reduced or the holding time is shortened, the obtained materials are impure or poor in crystallinity. The Na3V2(PO4)3/C composites with porous three-dimensional carbon skeleton structure can be obtained by template method, and the three-dimensional skeleton structure of the composites with porous three-dimensional carbon skeleton structure collapses by prolonging the holding time to 14 h or increasing the treatment temperature to 800oC. The Na3V2(PO4)3/C composites were synthesized by template method and were characterized by thermogravimetric analysis, Raman spectroscopy, field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV). The structure and properties of the composite were characterized by constant current charge-discharge method. The results showed that the constant current charge-discharge tests were carried out at different discharge rates of 1Cn2C5C5C10Cn20C and 50C at different discharge rates, the results showed that: Na3V2PO4PO4 / C composite material was tested by constant current charge and discharge at different discharge rates. The discharge capacity is 113mAh/ g, 100mAh/ g, 77mAh/ g, 70mAh/ g, 62mAh/ g and 58mAh/ g, respectively. At the same time, the Coulomb efficiency is close to 100, and the discharge rate is 100 cycles at 1C and 2C discharge rate, the capacity is basically unattenuated, showing excellent cyclic stability.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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