Study of lithiation mechanisms of high performance carbon-coated Si anodes by in-situ microscopy
Study of lithiation mechanisms of high performance carbon-coated Si anodes by in-situ microscopy
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DOI：
10.1016/j.ensm.2016.01.003
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发表时间：
2016-04
影响因子：
20.4
通讯作者：
Zheng-Long Xu;Ke Cao;Sara Abouali;Mohammad Akbari Garakani;Jiaqiang Huang;Jian‐Qiu Huang;E. Heidari;Hongtao Wang;J. Kim
中科院分区：
文献类型：
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作者：
Zheng-Long Xu;Ke Cao;Sara Abouali;Mohammad Akbari Garakani;Jiaqiang Huang;Jian‐Qiu Huang;E. Heidari;Hongtao Wang;J. Kim
采用一锅碳化法制备了高硅含量（81wt%）的碳包覆硅（Si/C）复合材料。Si/C电极在0.5 A g− 1下50次循环后可提供2003 mA h g− 1的高循环容量，在4 A g− 1下超过200次循环后可提供约750 mA h g− 1的增强倍率容量。利用原位透射电镜（TEM）研究了碳包覆对硅颗粒锂化机理的影响。结果表明，碳包覆的Si颗粒在初始锂化过程中经历了各向同性到各向异性的转变，而未包覆的Si颗粒没有观察到这种转变。Si/C的锂化速率比具有相同直径的未涂覆Si的锂化速率快3-4.5倍，这证明了Si/C在真实的电池中的高倍率容量。柔性的无定形碳涂层有利地将Si颗粒的损伤模式从通过多个裂纹的粉碎改变为通过单个裂纹的断裂。上述研究结果为设计具有更高电化学性能的硅基电极碳涂层提供了理论依据和实践指导。
Carbon coated Si (Si/C) composites with a high Si content of 81 wt% are synthesized by one-pot carbonization of the mixture containing commercial Si particles and polyvinylidene fluoride (PVDF) at an optimized temperature. The Si/C electrodes deliver a high cyclic capacity of 2003 mA h g−1at 0.5 A g−1after 50 cycles and an enhanced rate capability of ~750 mA h g−1at 4 A g−1for over 200 cycles. The effect of ultrathin carbon coating on lithiation mechanisms of Si particles is evaluated using thein-situtransmission electron microscopy (TEM). It is revealed that the carbon-coated Si particles undergo an isotropic to anisotropic transition during the initial lithiation, whereas such transition is not observed for the uncoated Si particle. The lithiation rate of Si/C is 3–4.5 times faster than that of uncoated Si with the same diameter, a testament to high rate capacities of Si/C in real batteries. The flexible, amorphous carbon coating favorably alters the damage mode of Si particles from pulverization by multiple cracking to fracture by a single crack. The above findings offer fundamental understanding and practical guideline for designing carbon coatings of Si-based electrodes with much enhanced electrochemical performance.