提升微米矽陽極鋰離子電池之 循環穩定性之研究

Abstract

矽是近年來鋰離子電池中備受矚目的陽極材料，因為矽擁有很高的理論電容量(4200 mAh/g)，然而在和鋰離子反應時會造成材料膨脹而造成電池的負面效果，雖然奈米級的矽材料已經能克服這項缺點，但奈米矽材料的生產成本十分高昂也難以大量製造。而微米級的矽材料成本就相對低廉許多。 本篇使用簡單但有效的方法來穩定微米矽粒子（325 mesh）所造成的劇烈膨脹，利用蔗糖為碳源製作碳矽複合結構，以碳做為穩定矽粒子的基質與增加導電度的角色，微米矽做為主要的儲存鋰離子的材料。其結果為: Si : Sucrose= 1:6的條件中第1圈放電電容量1928 mAh/g到了第30圈仍然保有第1圈電容量的87%(電流密度400mA/g)。Silicon (Si) appears to be an attractive candidate for lithium-ion batteries because it delivers greater theoretical capacity(∼4200 mAh/g). However, the widespread application of silicon materials has remained a significant challenge because of the large volume changes during lithium insertion and extraction processes. Nanostructured Si materials showed superior performance because of their ability to alleviate mechanical strain induced by volume change. However nano-sized silicon is very expensive, and not easier to scale up for mass manufacturing compared to micron-sized Si. To address the significant challenges associated with large volume change of micron-sized Si (325 mesh) particles for lithium-ion batteries, we demonstrated a simple but effective strategy: using sucrose carbon as a matrix and conductive material, and micron-sized Si as the main lithium-ion storage material. The sucrose carobon provide structure stability for the electrode. The resulting electrode (Si : Sucrose= 1:6) showed the first cycle capacity of 1928 mAh/g, and retained 87% capacity after 30 cycles at current density 400 mA/g.