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采用真空气雾化与高能机械球磨法结合,制备SnCoC复合材料作为锂离子电池负极材料,操作简单,时间短,易于实现工业化。采用X射线衍射(XRD)和扫描电子显微镜(SEM)检测合金粉末及复合材料的相结构和表面形貌,结果发现碳的引入不会对合金相结构产生影响,它以无定形碳形式存在,随着球磨时间的增加,合金由晶态向非晶态转变,且颗粒变得均匀,部分颗粒尺寸甚至达到纳米级。将制得材料组装成模拟电池,测试其电化学特性,结果表明:球磨20 h的Sn-Co合金比未球磨的合金负极的比容量高且循环更稳定,而将合金与石墨球磨后,所得复合材料的电化学性能进一步提高,首次库仑效率最高达90.6%,50次循环后容量保持率66.7%。分析可知:通过将锡钴合金弥散在无定形碳中,获得非晶纳米晶双相结构的SnCoC复合材料。非晶材料的各向同性,能够缓冲Li-Sn在合金化-去合金化过程中产生的结构和电场应力;纳米级尺寸的材料内部空隙多,有利于锂离子的扩散;碳材料除了稳定的结构外还可以提供一定的容量。这些有利因素结合起来,极大改善了材料的电化学性能。
Using vacuum gas atomization combined with high-energy mechanical ball milling, the SnCoC composite material is prepared as a negative electrode material of a lithium ion battery, which has the advantages of simple operation, short time and easy realization of industrialization. The phase structure and surface morphology of the alloy powders and composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the introduction of carbon did not affect the phase structure of the alloy, and existed in the form of amorphous carbon. With the increase of ball milling time, the alloy changes from crystalline state to amorphous state, and the particles become even, and the particle size reaches some nanometer level. The obtained material was assembled into a simulated battery and its electrochemical properties were tested. The results show that the specific capacity of the Sn-Co alloy after 20 h milling is higher than that of the un-milled alloy negative electrode and the cycle is more stable. When the alloy and graphite are ball milled, The electrochemical performance of the composites is further improved. The first coulombic efficiency is up to 90.6% and the capacity retention rate is 66.7% after 50 cycles. Analysis shows that SnCoC composites with amorphous nanocrystal dual phase structure can be obtained by dispersing tin-cobalt alloy in amorphous carbon. The isotropy of amorphous materials can buffer the structure and electric field stress of Li-Sn during the alloying-de-alloying process. The nanoscale-sized material has many internal voids that are favorable for the diffusion of lithium ions. In addition to the stable Structure can also provide some capacity. Together, these positive factors greatly improve the electrochemical performance of the material.