| 摘要: | 在過去的半個世紀以來，對於高功率和高效能量儲存裝置的需求日益增加。矽由於其優異的特性而被視為相當有潛力的鋰電池負極材料，例如低工作電壓，高理論比容量，低成本和大量地球。 不幸的是，矽負極在鋰化過程中嚴重地體積膨脹，這對容量衰減和循環性能影響很大。 因此，為了控制矽的體積膨脹，在矽表面上進行碳披覆及粒徑優化被認為是有潛力的方法。
在碳披覆的過程中，利用矽粉與葡萄糖/煤不同比例混合，並在熱處理後分別達到碳含量10 wt％，20 wt％，和30 wt％ (煤焦油40 wt％)。 葡萄糖作為碳源似乎比煤焦油具有更好的性能。 此外，我們在最佳碳塗層含量20 wt％ (GL20樣品) 獲得最佳循環性能。 並在GL20樣品中顯示出最高的首次充電容量為2689.8 mAh/g，並且高速保留率為31.4％，甚至在200次循環後仍具有1278.4 mAh/g。 此外，我們研究了粒徑對於碳披覆矽影響。 我們發現在20 wt％碳塗層中有最小粒徑 (〜100 nm) 的樣品 (SC100) 顯示出比較大粒徑尺寸的 (>400nm) 有更佳的首次充電容量 (2808.1 mAh/g) 的驚人表現和以及200次循環後仍能達到1751.5 mAh/g。 此外，添加石墨形成複合材料將會是一個較佳的手法來增益高速維持率及循環壽命。 最後一小節的研究結果證實添加 45-60 wt% KS6的石墨比起添加30 wt% 石墨時在高速維持率多了更高 增益，並且在100圈後依舊可以保持55% 的第一圈電容值。;Demand for high power and efficiency energy storage in this past half-century is tremendous high. Silicon, as a promising anode material for LIBs, has a various benefit, such as low working voltage, high theoretical specific capacity, low-cost, and earth abundance. Unfortunately, silicon anode has a big challenge in serious volume expansion during lithiation process, which affected in capacity fading and poor cycle performance. Thus, in order to control volume expansion in silicon, carbon coating and silicon particle size optimizing method lead to be promising ways.
During carbon coating process, the silicon powder mixed with glucose/coal tar at different ratios to reach 10 wt%, 20 wt%, and 30 wt% (40 wt% for coal tar) carbon contents after heat-treatment, respectively. It seems that glucose as a precursor has a better performance than coal tar. Furthermore, we got the best cycle performance at the optimum carbon content at 20 wt% (GL20 sample). GL20 sample shows high first charge capacity 2689.8 mAh/g with 31.4% in high rate retention and even after 200 cycles still stand in 1278.4 mAh/g. In addition, we investigated the particle size effect in carbon-coated silicon. Expectedly, we found that the smallest particle size (~100nm) with 20 wt% carbon coated silicon (SC100 sample) shown a breathtaking results with higher first cycle charge capacity (2838.1 mAh/g) than larger size of particle size (>400 nm) and it still can stand for 1751.5 mAh/g after 200 cycles. Moreover, additional KS6 graphite as a composite can be a good choice in increasing high rate retention and cycle performance. Based on the latest experiments of this study, it has proven that the addition of 45-60 wt% KS6 graphite can increase the high rate retention, and after 100 cycles the capacity still stand for more than 55% from its first charge capacity. |
