高纯纳米硅的规模化可控制备及其电化学性能

Controllable and Large-scale Preparation of High-purity Nanosilicon and Electrochemical Performance

摘要:

硅以具有已知元素中最高的嵌锂容量成为锂离子电池负极材料研究的热点之一。但是，硅在嵌脱锂过程中的巨大体积膨胀（~300%）制约了其在锂离子电池中的应用。纳米化是解决硅嵌脱锂体积膨胀的一种有效方案。本研究采用高能电子束和机械研磨两步法，以冶金硅为原料制得了可用于高储能锂离子电池的纳米硅。通过SEM分析，发现在高能电子束的作用下熔融硅蒸发后先沉积成线径在40nm左右的硅纳米纤维，进而成硅纳米线束状。对沉积硅机械研磨后纳米硅颗粒尺寸分布较为均匀。电化学分析表明，纳米硅在纯度达到99.96%以上的情况下，充放电密度为100mAh/g时，首圈可逆容量为1292.4mAh/g，电荷转移阻抗拟合值为51.36Ω。实验结果表明，此种方法可以较好的实现纳米硅的可控和规模化制备，为硅在锂离子电池未来工业化生产方面具有一定的指导意义。

Abstract:

Silicon（Si） has become one of the hot spots in the research of anode materials in lithium-ion batteries (LIBs) for its highest lithium intercalation capacity among known elements. However, the large volume expansion (~300%) of Si due to the lithium intercalation restricts its application in LIBs. Nano-crystalized is an effective solution to resolve the volume expansion. Nano-Si was prepared by high-energy electron beam and mechanical grinding method, using metallurgical Si. According to scanning electron microscopy (SEM) observation, the molten Si was deposited into Si nanofibers with a linear diameter of about 40nm after evaporation under the action of high-energy electron beam, and then gathered into Si nanobundles, and the size distribution of nano-Si particles after mechanical grinding is uniform. The results of electrochemical tests show that the first reversible capacity is 1292.4mAh/g, and the charge transfer impedance fitting value is 51.36Ω, under the condition of the nano-Si purity reaches more than 99.96% and the discharge density is 100mAh/g. The experimental results indicates that this method can be applied to controllable and large-scale prepare nano-Si, and gives a guidance that how to scalable use Si in LIBs industry.