從二矽化鈣合成片狀矽在鋰電池負極的應用

隨著近年來電動車的崛起，鋰電池產業研究也變成最熱門的研究之一。而矽作為擁有石墨10倍以上的電容，被認為會成為下一世代鋰離子電池的負極材料，但矽在充放電過程中體積膨脹劇烈的問題仍需要解決。而二維結構的矽可以有效解決此問題，由於二維結構膨脹僅有厚度方向的上下膨脹，因此體積膨脹能降低一半以上。文獻中有多種合成二維矽的方法，其中矽化鈣的拓樸反應為一種簡單、低成本的方式，文獻中多使用低溫鹽酸水溶液的方式去合成低含氧的堆疊分層矽烯片，再透過震盪的方式去進行剝離來產生奈米矽烯片，最後經過鍛燒成為奈米片狀矽。雖說擁有好的形貌，但在長時間水溶劑反應下會造成氧化，導致電池表現變差，且大多論文多沒提及其產率，或提到產率小於3%[19]，也沒人將奈米矽烯片應用於鋰電池領域中。在此研究中，吾人先嘗試在不同水與乙醇的溶劑比例中，發現在純乙醇的溶劑下可以獲得最佳可剝離的形貌，取代文獻中所使用的低溫水溶劑。並發現在純乙醇下不同反應溫度，剝離後所獲得的片狀擁有不同的尺寸與厚度，另外吾人也發現到在不同起始固含量進行剝離所得到的產率有所不同，在低固含量剝離時甚至可達到10%，遠高於文獻中所提及的3%[19]。於無水乙醇溶劑中反應，最大的優勢在於即使反應時間拉長，由於沒有氧源，不會造成矽烯片的氧化，能得到良好形貌及低氧化的矽烯片。最後吾人將奈米矽片應用於鋰離子電池中，能夠得到1980 mA h/g的起始電容、59.8%首圈效率、並在250圈後仍有810 mA h/g的可逆電容、96.6%的電容保持率等良好循環性的表現，期望能應用於未來鋰電池市場之中。

關鍵字

矽化鈣；奈米片；二維矽；矽烯；負極材料；鋰離子電池

並列摘要

Silicon, as a capacity with more than 10 times that of graphite, is considered to be the anode material for the next generation of lithium-ion batteries, but the problem of severe volume expansion of silicon during charging and discharging still needs to be solved. The two-dimensional structure of silicon can effectively solve this problem. There are many methods for synthesizing 2D silicon in the literature. Among them, the topological reaction of calcium silicide is a simple and low-cost method. In the literature, low-temperature hydrochloric acid aqueous solution is often used to synthesize low-oxygen multi-layer silicene. The silicene nanosheet is produced by exfoliation by sonication. Although it has a good morphology, it has not mentioned its yield, or mentioned that the yield is less than 3%[19], and no one has applied silicene nanosheets in the field of lithium batteries. In this study, we first tried in different solvent ratios of water and ethanol, and found that the best morphology can be obtained in anhydrous ethanol solvent, replacing the low-temperature water solvent used in the literature. It was found that under different reaction temperatures in anhydrous ethanol, the sheets obtained after exfoliation had different diameters and thicknesses. In addition, we also found that the exfoliation yields at different initial solid contents were different. It can even reach 10% at low solid content, which is much higher than the 3% mentioned in the literature.[19] Finally, we apply silicene nanosheets to lithium-ion batteries, which can achieve high capacitance and good cycle performance, and hope to be applied to the future lithium battery market.

並列關鍵字

calcium silicide ； nanosheets ； 2D silicon ； silicene ； anode ； lithium-ion batteries

參考文獻

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