以回收矽粒子與碳黑製備鋰離子電池負極材料及含添加劑之電解液電化學特性研究

Abstract

本論文利用碳黑殘餘物搭配光電產業的切削矽粒子碎片，製備高效能的鋰離子電池負極材料。首先碳黑與矽粒子會先在聚丙烯酸水溶液中進行分散混和，再進入氦氣高溫燒結程序形成碳包覆良好的碳/矽複合材料。透過聚丙烯酸的黏合作用，碳黑與矽粒子會被緻密的黏合，可以有效的提升複合材料的電容量循環表現以及電容量保持率。 此外本研究也對於電解液改質進行探討，透過碳酸亞乙烯酯及順丁烯二酸酐兩種添加劑的使用，可使得鋰鹽在電解液中表現出更佳的鋰離子導電度、鋰離子遷移數以及有效擴散係數，其歸因於兩種添加劑會在電極介面上生成聚合物形式的固態電解質介面膜(SEI)膜，可以阻擋電解液進一步在與矽粒子生成副反應，並提升電容量表現。而相較於順丁烯二酸酐在電池內部所生成的多孔洞性SEI膜，碳酸亞乙烯酯則會表現出更緊實、更穩定的鈍化保護層，因此在電池循環表現上顯得更加出色，更有效的提升電池壽命。 本研究製備1.5 mg/cm2重的負極材料，搭配具有碳酸亞乙烯酯的電解液，在進行51圈的充放電測試後可提供1923.0 mAh/gSi的第51圈比電容量，以及65.5%的51圈電容量保持率。經由適當的添加試劑，廢棄的回收物也能改造成為高價值的商品，是循環經濟的最佳體現。本論文透過回收廢棄的碳黑與矽粒子，製備成為高效能碳/矽複合材料，期待為鋰離子電池提供一個新的矽碳負極材料。

High capacity silicon-carbon composite materials have been prepared and investigated from carbon black residues and recycled silicon powders. The carbon black residues and recycled silicon particles are well blended in the appropriate particle dispersing solution, DI water containing dispersant, and are then pyrolyzed to prepare high performance Si-C composite materials. Such solution can provide spectacular carbon binding capability on silicon powders, thus enhancing overall capacity and capacity retention of the electrodes. Electrolyte additives vinylene carbonate (VC) and maleic anhydride (MA) are employed for improving cells performances. Electrolytes of Lithium hexafluorophosphate (LiPF6) in ethylene carbonate/diethyl carbonate (EC/DEC) with VC or MA additives are used to form polymeric solid electrolyte interface (SEI) around silicon particles surface, which can prevent recycled silicon electrodes from excess pulverization and improve cell performances. Instead of highly porous SEI structures with MA additive, VC would construct denser and more sturdy protection layers on silicon anodes, thereby further promoting LIBs cycle performances. The negative electrode prepared in this study at mass loading of 1.5 mg/cm2 with 1.2 M LiPF6 in EC/DEC containing 8 wt.% of VC as electrolyte solution delivers 51st cycle delithiation specific capacity 1923.0 mAh/gSi and 51st cycle retention as 65.5% at current rate of 1000 mAh/g. With appropriate additives, the low-cost recycled materials can contribute to high performance, and provide new ground for lithium ion batteries.