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采用磁控溅射法以不同的碳靶溅射功率在铜箔上制备了硅碳(Si/C)复合薄膜。通过实验和第一性原理计算相结合的方法研究了硅碳复合薄膜的电化学性能及在原子尺度下硅碳复合材料的储锂机理。实验研究发现，Si/C-100 W薄膜的首次放电比容量(2 981.2 mA·h/g)虽然最低，但多次循环后放电比容量保持率可以达到61.7%,同时，该样品具有最佳的倍率性能，在高电流密度(2 A/g)下表现出最高的放电比容量(约2 220.0 mA·h/g)。通过第一性原理计算不同硅碳原子数量比值(1.26、0.72和0.52)的Si/C结构来分析Si/C结构的储锂机理，结果发现，随着硅碳原子数量比值变化，其嵌入Li+后的体积变化率也有所改变，当硅碳原子数量比值为0.52时，Si/C结构的体积变化率为15.317%,同时其嵌入8个Li+后的形成能也最低，这说明碳硅原子数量比值降低，有利于较多Li+的嵌入，这也解释了Si/C-100 W具有较高稳定性和倍率性能的原因。
Abstract：Silicon-carbon(Si/C) composite films were prepared on the copper foil by magnetron sputtering with different carbon target sputtering powers. Through the combination of experiments and first-principles calculation, the electrochemical properties of the silicon-carbon composite films and the lithium storage mechanism of silicon-carbon composite materials at the atomic scale were studied. Through the experimental research, it is found that the first discharge specific capacity of Si/C-100 W film is the lowest(2 981.2 mA·h/g), but the discharge specific capacity retention rate after multiple cycles can reach 61.7%. Meanwhile, the film has the best rate performance, and exhibits the highest discharge specific capacity(about 2 220.0 mA·h/g) at a high current density of 2 A/g. The Si/C structures with different atomic numbers ratios of silicon to carbon(1.26, 0.72 and 0.52) were calculated by first principles to analyze the lithium storage mechanism of the Si/C structure. It is found that after embedding Li+, the volume change rate changes with the change of the atomic number ratio of silicon to carbon. When the atomic number ratio of silicon to carbon is 0.52, the volume change rate of Si/C structure is 15.317%, the formation energy of Si/C structure is the lowest after embedding 8 Li+, indicating that with the increase of the atomic number ratio of silicon to carbon, it is conducive to the embedding of more Li+, and explaining the reason that Si/C-100 W has higher stability and rate performance.
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基本信息:
DOI：10.13250/j.cnki.wndz.2022.11.007
中图分类号:TB383.2;TM912
引用信息:
[1]徐天齐,闫共芹,王康,等.硅碳复合薄膜作为锂离子电池负极材料的电化学性能及储锂机理[J].微纳电子技术,2022,59(11):1153-1161+1204.DOI:10.13250/j.cnki.wndz.2022.11.007.
基金信息:
广西自然科学基金资助项目(2020GXNSFAA159024); 柳州市科技计划项目(2018DH10507)