Effect of Buffer Size around Nanosilicon Anode Particles for Lithium-Ion Batteries
Effect of Buffer Size around Nanosilicon Anode Particles for Lithium-Ion Batteries
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DOI：
10.1021/jp2093669
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发表时间：
2012-03-15
影响因子：
3.7
通讯作者：
Kyotani, Takashi
中科院分区：
文献类型：
--
作者：
Iwamura, Shinichiroh;Nishihara, Hirotomo;Kyotani, Takashi
通过新建立的硬模板途径合成了硅纳米颗粒/碳复合材料，其中每个硅纳米颗粒嵌入球形纳米空间中。制备了一系列具有不同纳米空间尺寸的复合材料，并检查了它们作为锂离子电池负极的锂嵌入/脱嵌行为。每个硅纳米粒子周围的纳米空间可以作为硅在锂化过程中膨胀的缓冲器。通过使用该系列复合材料，系统地研究了纳米硅周围缓冲尺寸的影响。随着缓冲器尺寸增加至Si体积的约3倍，即允许Si膨胀至其原始体积的4倍的尺寸，可循环性变得更好。事实上，即使在具有适当缓冲尺寸的硅/碳复合材料中经过20次充放电循环后，多孔碳基体的结构仍能很好地保留，而具有较小缓冲尺寸的复合材料则完全被破坏。然而，缓冲尺寸的进一步增加导致了充放电循环性能的下降，这可能是因为更大的缓冲空间使得Si纳米颗粒在循环过程中更容易从碳基体中脱落。此外，原则上缓冲尺寸过大会降低负极材料的体积能量密度。由此得出结论，Si所需的最小缓冲尺寸约为Si体积的3倍，这也是实现良好循环性能和高体积能量密度的最佳尺寸。
Si nanoparticle/carbon composites in which each Si nanoparticle was embedded in a spherical nanospace were synthesized by a newly established hard-template pathway. A series of composites having different nanospace sizes were prepared, and their lithium insertion/extraction behaviors as an anode for lithium-ion batteries were examined. The nanospace which surrounds each Si nanoparticle can be a buffer against the Si expansion during its lithiation. By using the series of composites, the effect of the buffer size around nanosilicon was systematically investigated. The cyclability became better with increasing the buffer size up to about 3 times larger than the Si volume, i.e., the size which allows Si to expand up to 4 times larger than its original volume. Indeed, the structure of the porous carbon matrix was well retained even after 20 charge-discharge cycles in the Si/carbon composite with this appropriate buffer size, whereas a composite with a smaller buffer size was totally destroyed. The further increase of the buffer size, however, gave rise to the decline of the charge-discharge cyclability, probably because a larger buffer space makes it easier for Si nanoparticles to drop out from the carbon matrix during cycling. In addition, too large a buffer size in principle lowers the volumetric energy density of anode materials. It is thus concluded that the minimum necessary buffer size for Si is about 3 times larger than the Si volume, and this is also the best size to achieve a good cyclability as well as a high volumetric energy density.