混合綴碳球Si/SiOz粉末作為鋰離子電池陽極之電化學性能研究

C/Si/SiOz@Graphite Composites as an Anode Material for Lithium-Ion Batteries

鄒易霖(Yi-Lin Tsou)

指導教授 ： 李紫原

國立清華大學/工學院/材料科學工程學系/碩士(2020年)

摘要

隨著科技逐漸的進步發展，人們對於儲能的需求也越來越大，並且致力於研究出更高能量密度的儲能裝置。在鋰離子陽極材料中，矽 (Si) 被認為是鋰離子電池 (LIB) 陽極材料的候選材料之一，這歸因於其高理論比容量和低成本的優勢。 但是低電導率循環中的大體積膨脹 (~300%) 以及由於體積反覆變化而引起的固體電解質界面 (SEI) 層的不穩定性，限制了將Si用作鋰離子電池中的陽極。
本研究將工業上取得的矽氧複合物SiOx原始粉末經過高溫熱處理、加入葡萄糖酒精溶液中以水熱法摻碳、高溫碳化等具工業化潛力的程序加工改良後，摻少量進入石墨材料中，探討其對比電容量等電性的影響。矽氧複合物具有高達1500 mAh/g以上的比電容量，其比電容量的貢獻主要來自複合物中分散的矽；然而，矽在儲鋰時會轉為鋰矽化合物，伴隨劇烈體積膨脹。本研究之所以採用「混合」的方式增進電池比電容量，希望能將具有緩衝體積膨脹性質的石墨與高比電容量的矽氧複合物搭配，達到相輔相成的效果。
結果的確如預期，包覆碳的SiOx的確不會因為結構崩塌而造成電性上的損失，另外組裝以C/Si/SiOz混合石墨為陽極和三元材料為陰極的全電池，以0.5 C速率進行充放電循環測試，首圈庫倫效率高達97.76%，經過1000圈後衰減率也僅有25%。

關鍵字

鋰離子電池 ； 碳 ； 陽極 ； 矽 ； 複合材料

並列摘要

Silicon (Si) has been regarded as one of the candidates for anode material in lithium-ion batteries (LIBs) attributing to the advantages of high theoretical specific capacity and low cost. However, low electrical conductivity, large volume expansion during cycling (~300%) , and instability of the solid electrolyte interface (SEI) layer caused by repeated volume changes limit the use of Si as anodes in LIBs.
To overcome the issues that cause poor capacity retention, it is believed that the uniformity and well mixing of Si and carbon could set as a buffer for volume expansion of Si and improve the electrical conductivity at the same time. In this research, industrially obtained SiOx was used as the Si source.
After high-temperature heat treatment and carbon coating by hydrothermal method, Si particles and carbon were uniformly mixed and well dispersed. Small quantities of the SiOz/ amorphous-Si/C composites were mixed into graphite and used as anodes in LIBs. The full-cell prepared from SiOz/amorphous-Si/C@graphite (5%:95%) composites demonstrates good cycle performance with little fading (75% after 1000cycles) .

並列關鍵字

Lithium-Ion Batteries ； Graphite ； anode ； silicon ； Composites

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