Synthesis and characterics of benzimidazole lithium salts containing fluorine functional group and its application as an electrolyte additive of lithium-ion battery

• Main Authors: Chung-suei Liou, 劉鐘穗
• Other Authors: Fu-ming Wang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/96678099469868210724

碩士 === 國立臺灣科技大學 === 應用科技研究所 === 102 === Electrolyte plays a critical role in initiating electrochemical reactions of Li-ion battery, which is used to diffuse ions between the anode and cathode. LiPF6 is the most popular salt into lithium ion battery; however, it’s not safe enough for widely applications. This study synthesizes a new compound, constructed by benzimidazole structure, and is used to an electrolyte additive for maintainy the chemical stability of LiPF6. Prior research shows the solubility of benzimidazole lithium salt is not perfect enough in common carbonate solvents. This study synthesis a novel benzimidazole lithium salt containing fluorine functional group to solve the solubility problem. According to the results, the electrolyte containing fluoro-benzimidazole salt increases the ionic conductivity of electrolyte. Owing to the molar concentration of Li ion was increased. From cyclic voltammetry measurement of the electrolyte, the addition of fluoro-benzimidazole salt eliminates the polarization of the electrochemical reaction and shows good reversible ratio. The irreversible ratio of the electrolyte with fluoro- benzimidazole was decreased from 80% to 61%. The anode half cell shows the addition of fluoro-benzimidazole maintain the battery performance (~300mAh/g) at 60℃ after several cycles, compared to the common electrolyte(~200mAh/g). The impedance test shows that the Rct has decreased to 55 while the electrolyte contains fluoro-benzimidazole, and the common electrolyte shows 76.3. It is because the benzimidazole lithium salt interacts with PF5 and generates pentafluorophosphate benzimidazole, inhibiting the PF5 side reactions. The electrolyte containing fluoro-benzimidazole lithium salt performs a good performance, and can be used into lithium ion battery.