高電容量且可快速充電的二硫化鐵天然礦石應用在鈉離子電池的陽極

Abstract

二硫化鐵(天然黃鐵礦)是近年來被廣泛研究並認為是極具潛力應用在鋰離子電池的陽極材料，因為二硫化鐵本身的一些良好性質及優點，例如高理論電容量、無毒性對於環境影響低和低成本。但是由於鋰金屬是非常昂貴的材料，最近二次電池之發展著重低成本電池之開發。鈉離子電池被認為是相當符合的一種選擇，因為鈉金屬的成本價格低、高理論電容量等優點，能夠完全取代性質相似的鋰金屬。但實際上，低能量密度、低輸出電位和電容量的限制是目前鈉離子電池遇到的問題，所以本篇論文，以尋找適合的電極材料來改善目前的鈉離子電池之問題。

所以本研究是將天然礦石二硫化鐵材料應用在鈉離子電池之陽極。我們發現二硫化鐵材料應用在鈉離子電池陽極上以電流密度約50mAg-1其第一圈放電電容量約為730mAhg-1而第一圈可逆電容量約為584 mAhg-1，其不可逆電容量約為20%。到了第50圈其電容量約還有400 mAhg-1。在第二次之後的充放電過程中可以發現不可逆電容量非常低。並且在快速充放電的測試過程中，我們以電流密度約8920 mAg-1的大電流充放電於二硫化鐵之鈉離子電池，其電容量約還有相當高之電容量280 mAhg-1。最後，我們發現單純以二硫化鐵應用在鈉離子電池的陽極上，有較好的循環表現、良好的庫倫效率和在快速充放電下可保持一定之電容量。In recent years, FeS2 (natural pyrite) has been widely studied and considered to be potential electrode in the anode material for lithium-ion batteries, because some of the iron disulfide itself good properties and advantages, such as high theoretical capacity, no toxicity for low environmental impact and low cost. However, due to the lithium metal is very expensive material, secondary battery focuses on the development of low-cost battery. Sodium-ion battery is considered to be quite consistent with a choice, because of the low cost price of the sodium metal, high theoretical capacity, etc. It is possible to completely replace the similar properties of the lithium metal. But in fact, the low energy density, low output potential and capacity restriction are the problems encountered by the sodium-ion battery. In this thesis, we find a suitable electrode material to improve cycle stability and high capacity at high charge-discharge rate of the sodium-ion batteries.

Therefore, this study focused on the natural iron disulfide material used in the sodium-ion battery anode. We found that iron disulfide as anodic materials of sodium-ion battery (FeS2-NIB) has demonstrated the first discharge and charge capacity of 730 mAh g-1 and 584 mAh g-1 at a current density of 50 mA g-1. The irreversible capacity of first cycle is approximately 20%. Especially, the irreversible capacity of charge-discharge process after second cycle is much less. The capacity of FeS2-NIB still remained 400 mAh g-1 after 50th cycles. During rapid charge-discharge test, FeS2-NIB have high capacity of 280 mAh g-1 at a current density of 8920 mA g-1. Overall results showed that the pure iron disulfide as anodic materials of sodium-ion battery demonstrated long cycle performance, high coulombic efficiency and good capacity retention at high charge-discharge rate. The results indicate that earth-abundant FeS2 is an extremely interesting candidate as anode materials of sodium-ion battery with a suitable electrolyte for fast intercalate/deintercalate Na ion reversibly.