水系电化学储能体系锰氧化物电极材料的制备及性能

发布时间：2019-06-04 09:09

【摘要】：随着智能电网的发展和清洁可再生能源的并网,大型电化学储能技术变得日益重要。它是改善和稳定电力系统平稳运行的有效方法。可以根据电网的运行起到调整频率、平滑负荷、冷启动、电力应急和削峰填谷的作用。此外,还能提供局部电力供应和无功功率支持等服务。水系钠离子电池具有绿色环保、安全、成本低廉、钠离子资源丰富等特点,在大型电化学储能方面有很大的应用前景。 水钠锰矿类锰氧化物,是一类具有Mn06八面体共边组成二维层状结构的材料,层与层之间的距离约为7A,允许层间区域的阳离子快速迁移,同时为离子在电解液和电极界面的快速动力学移动提供可能。因此,这类层状材料也可以作为水系钠离子电池的正极材料来进行使用。同样,材料的结晶性,形貌和结构对其电化学性能有很大的影响。在本文中,我们主要通过形貌和结构的设计来提高这类材料作为水系钠离子电池正极材料的电化学性能。主要研究内容和结果如下： 采用简单的局部化学法制备具有分级结构的花状K0.27MnO2通过)RD (X-ray powder diffraction)、FE-SEM (Field emission scanning electron microscope)、TEM (Transmission electron microscopy)等手段,考察热处理温度对得到材料形貌和结构的影响。研究表明材料的层状结构在700℃时依然能够保持。但是,花状形貌则会遭到破坏。三电极体系测试表明,花状分级结构的样品KMO-500具有优异的电化学性能。以K0.27MnO2作为正极,商业化的活性碳作为负极,考察材料作为水系二次电池的电化学性能。研究表明在能量密度为418W h kg-1,电池的功率密度可以达到180.0Wkg1。此外,经过1000次充放电循环以后其结构和形貌仍然得到很好的保持。这些结果表明,这种材料具有稳定的层状结构,可以用在大型电化学储能器件上。 分级花状K0.27MnO2具有层状结构,可以作为水系钠电池正极材料。同样,采用局部化学法经过500℃热处理2h得到这种材料。以花状的K0.27MnO2作为正极,NaTi2(PO4)3作为负极,在200mAg-1的电流密度下,经过100次充放电循环,电池的比容量还有68.5mA h g-1。将这种材料用作水系钠离子电池正极材料表现出很好的可逆容量、循环稳定性和倍率性能。同时,通过对充放电循环前后的材料结构和表面化学态进行研究,分析钠离子可能存在的脱嵌机制。经过首次充电过程,钾离子从电极材料中脱出,后面的充放电循环主要是钠离子进行嵌入和脱出反应。可以说这种廉价,环境友好的电极材料作为水系钠离子电池在大型电化学储能上具有实际应用前景。 采用乳液聚合得至PS (Polystyrene,聚苯乙烯)球,将其作为前驱体模版,通过水热法得到核壳结构的PS@K-δ-MnO2,通过热处理除去样品内部的PS球,得到具有中空结构的K0.27MnO2。在三电极体系中,对材料K0.27MnO2的电化学性能进行测试。在充放电电流密度为200mAg1时,经过100次充放电循环,其放电比容量还有40.6mAhg-1,容量保持率几乎为100%,具有很好的循环稳定性。此外,以中空K0.27MnO2作为正极,NaTi2(PO4)3作为负极,组装水系钠离子电池,其中电压范围设为0～1.8V,对其电化学性能进行研究。在600mAg1条件下,经过10次充放电循环,其放电比容量还在50mA hg1以上。说明这种中空结构能够有效的减少材料粒径,增加电极材料和电解液的接触面积,缩短离子或者电子的传输距离,有利于钠离子的快速嵌入和脱出。 通过水热法和离子交换反应制备含有不同碱金属离子的层状MnO2(A-8-MnO2, A:K, Na)。将含有不同碱金属离子的材料作为正极,NaTi2(PO4)3作为负极组装成全电池。研究材料的形貌、结构和组成对电化学性能的影响。与无规则的颗粒相比较来说,花状结构的材料具有优异的电化学性能。其中,样品K, Na-8-MnO2作为正极材料表现出很好的循环和倍率性能,在200mAg1时,经过200次充放电循环,其可逆比容量还有-59.6mA h g-1,在电流密度为600mAg1,其放电比容量还有46.6mA h g-1。研究分析经过一次充放电循环后电极材料的化学态和化学成分,探讨和揭示电化学反应过程。对经过200次充放电循环后的K,Na-δ-MnO2电极片,进行结构和形貌分析,表明材料的结构比较稳定。
[Abstract]:The technology of large-scale electrochemical energy storage is becoming more and more important with the development of the smart grid and the grid of clean and renewable energy sources. It is an effective method to improve and stabilize the stable operation of the power system. The function of adjusting frequency, smoothing load, cold start, electric power emergency and peak clipping can be achieved according to the operation of the power grid. In addition, services such as local power supply and reactive power support can also be provided. The water system sodium ion battery has the characteristics of being green, environment-friendly, safe, low in cost, rich in sodium ion resource and the like, and has great application prospect in large-scale electrochemical energy storage. The manganese oxide of the water-sodium manganese ore is a material with a two-dimensional layered structure composed of a common edge of the Mn06 octahedron, the distance between the layer and the layer is about 7A, the cation of the interlayer area is allowed to be rapidly migrated, and meanwhile, the rapid kinetic movement of the ions in the electrolyte and the electrode interface can be provided. Thus, such a layered material can also be made as a positive electrode material of an aqueous sodium ion battery, In the same way, the crystallinity, morphology and structure of the material have a great shadow on its electrochemical performance. In this paper, we mainly improve the electrochemical property of this kind of material as the cathode material of the water-based sodium ion battery by the design of the shape and structure. Energy. Main research content and results such as In this paper, a simple partial chemical method was used to prepare the flower-like K0.27 MnO2 with a graded structure. The morphology and structure of the obtained material were investigated by means of RD (X-ray power diffractions), FE-SEM (Field emensable electron microscope), and TEM (Transmission electron microcopy). The study shows that the layered structure of the material can still be at 700 鈩，

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