鋰離子電池負極材料-矽/碳複合物之研究

Study on Anode Materials for Lithium Ion Batteries - Silicon/Carbon Composite

梁創閔(Chuang-Min Liang)

指導教授 ： 王朝弘

國立中正大學/工學院/化學工程學系/碩士(2013年)

摘要

碳系材料為目前商業化鋰離子電池之負極材料，其最高理論電容量僅372mAh/g，雖具備穩定性佳，循環壽命長等優勢，但受限於其能量密度太低，若要應用於高電容量要求之電池上仍嫌不足。矽負極材料理論電容量高達4200mAh/g，但其在充放電過程中體積劇烈的縮放，易造成電極結構損壞，進而使電池電容量快速衰退。
本研究為了提高鋰離子電池之電容量表現，使用矽材與石油焦炭、MCMB兩種碳材相混合，搭配黏著劑、助導劑，將其製備成矽/碳負極材料，做電化學相關測試。由實驗結果發現傳統的PVDF黏著劑，其無法承受矽材與鋰離子進行合金化反應所產生的巨大體積改變，造成電極結構碎裂，使電池電容量在充放電前三圈大量衰退。為了克服此難題，本研究使用新型黏著劑取代PVDF黏著劑進行測試。從實驗結果顯示以新型黏著劑當作黏著劑，其電池電容量能維持20圈循環而不衰退，展現優異的循環穩定性。
為了近一步增益電池性能，本研究也在漿料混合的過程中，分別添加不同之分散劑，包含漿料分散劑與奈米矽粉分散劑。實驗結果顯示在PVDF做為黏著劑條件下，添加漿料分散劑有助於電池第一圈不可逆電容量降低，而奈米矽粉分散劑提升了電池循環壽命。而本研究也使用新型黏著劑，搭配漿料分散劑，能得到最佳矽/碳複合材料之電池表現，其經過100圈充放電後，電容量存留率高達85.06%，且電池電容量也維持在528.97mAh/g，展現高電容量與高循環穩定性的電極結構。

關鍵字

鋰離子電池 ； 分散劑

並列摘要

Nowadays carbonaceous materials are widely used as anode materials in commercial lithium-ion batteries because of higher stability upon cycling. Due to the relatively low capacity (theoretical value: 372 mAh/g) of graphite, the development for alternative anode materials such as silicon has attracted much attention, which is one promising material because of its high theoretical capacity (4200 mAh/g). In this study, Si powders were added in both petroleum coke and MCMB to increase the energy density of LIBs. The Si/C composites as lithium ion battery anode material were made of PVDF or New binder as a binder and carbon black as a conductive, the electrochemical performance was discussed.
Si has the highest capacity among all potential anode materials but a huge volume expansion is accompanied by lithiation. In our study, PVDF binder was unable to accommodate large silicon volume expansion, which led to sever pulverization of Si/C composite electrode and capacity fading. Therefore, we demonstrate that New binder was used to replace the PVDF binder. The performance was significantly improved after replacing New binder as binder. Due to the carboxylic functional group in New binder can enhance the adhesion between the slurry and the copper foil. Furthermore, for better cycle performance of the Si/C composite electrode with addition of the slurry dispersant and nano-silicon powder dispersant in the slurry, the first-cycle irreversible capacity and the cycling performance is greatly improved. Our results showed that Si/C composites during 100 cycles, the capacity is higher than 528.97mAh/g, and the retention is up to 85.1%.

並列關鍵字

Lithium ion battery ； Dispersant

參考文獻

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