Mechanistic understanding of pore evolution enables high performance mesoporous silicon production for lithium-ion batteries
Mechanistic understanding of pore evolution enables high performance mesoporous silicon production for lithium-ion batteries
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DOI：
10.1039/c9ta13633a
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发表时间：
2020-03-07
影响因子：
11.9
通讯作者：
Patwardhan, Siddharth, V
中科院分区：
文献类型：
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作者：
Entwistle, Jake E.;Beaucage, Gregory;Patwardhan, Siddharth, V
锂离子电池（LIB）内部硅阳极的循环会导致硅体积变化280%，从而导致电池性能退化和容量衰减。人们已经探索了许多硅合成方法来生产能够承受这种体积变化的纳米结构。在制备多孔硅纳米结构方面，镁热还原（MgTR）在可扩展性、经济性和环保性方面都比其他合成方法有更大的前景。MgTR的问题是缺乏对基于还原参数和前驱体材料的多孔硅孔隙演化的理解，这反过来又限制了预期应用的预测设计。研究表明，多孔硅的孔隙结构与硅晶体的连通性密切相关。我们发现MgTR是一个热力学驱动的平衡，它决定了硅产品的纯度。较高的温度也会导致硅纳米晶体的烧结。我们发现这些晶体的相互连接决定了多孔硅的孔径和分布。这些发现适用于各种多孔二氧化硅前驱体，我们表明这种机制适用于MgTR后将孔隙引入无孔石英中。此外，我们表明，通过利用这一机制，可以生产介孔硅，这种介孔硅在100次循环后的容量为2170 mA h g(-1)，在LIB应用中具有良好的前景。本文的研究结果可以用于设计LIB应用的最佳材料。这些结果有力地支持了在经济和环境方面降低lib硅成本的潜力，以及逆向工程方法来设计特定多孔硅的期望应用，甚至超出lib。
The cycling of silicon anodes within a lithium-ion battery (LIB) leads to degradation and capacity fade due to the 280% volume change of silicon. Many methods of silicon synthesis have been explored to produce nanostructures which can withstand this change in volume. Magnesiothermic Reduction (MgTR) shows significant promise over other syntheses in scalability, economic and environmental aspects for producing porous silicon nanostructures. The problem with MgTR is a lack of understanding regarding the pore evolution of porous silicon based on reduction parameters and precursor materials, which in turn limits predictive design for desired applications. Here we show that the pore structure of porous silicon is strongly related to the interconnectivity of silicon crystallites. We show that MgTR is a thermodynamically driven equilibrium which determines the purity of the silicon product. Higher temperatures also cause sintering of silicon nanocrystallites. We show that it is the interconnectivity of these crystallites that determines the pore size and distribution within porous silicon. These findings apply to a wide variety of porous silica precursors and we show that this mechanism is true for the introduction of pores into nonporous quartz after MgTR. Furthermore, we show that by exploiting this mechanism, mesoporous silicon can be produced which has excellent promise for LIB applications with a capacity of 2170 mA h g(-1) after 100 cycles. The findings herein can be taken forward to design optimal materials for LIB applications. These results strongly support the potential for reduction in silicon costs for LIBs in both economic and environmental terms as well as for a reverse engineering approach to design specific porous silicon for desired applications even beyond LIBs.