Modifications of cathode Material LiFePO4 for Lithium-ion Battery

• Main Authors: Yun-Man Lee, 李雲漫
• Other Authors: I-Shou Tsai
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/18680009138432293275

碩士 === 逢甲大學 === 纖維與複合材料學系 === 101 === Recently, the demand for energy is increasing due to advanced technology development. The energy density, output power, effective duration and safety of Li-ion battery is much better than those of tradition al battery. The production of Li-ion battery becomes the main trend of industry, from cumbrous to thin and light. Wherein the lithium-ion battery cathode materials of lithium iron phosphate (LiFePO4) has attracted much attention, because of its good thermal stability, affordability, safety, stability of functioning voltage, non-toxic and flat voltage profile, etc. These advantage have actually been used in electric vehicles. However, it still has a low ionic diffusivity and poor electronic conductivity, therefore many researchers add metal which decreases the particle size to improve its performance. In this study, particle size of lithium iron phosphate was reduced after milling, the surface thereon was coated with nano-silver. Here, we are explore and discuss the benefits of nanosilver on transferring electrics and Li-ion. A polyol method was used in this study, we added silver nitrate (AgNO3) in the Ethylene Glycol (EG) at 140 ℃, and then added polyvinyl pyrrolidone (PVP) as a protective agent. After that, we added glucose reaction for 2 hours. Finally the surface of lithium iron phosphate was coated with reduced silver particles. After drying, a slurry composition of powders in proportion of Lithium iron phosphate- silver: Carbon black: PVDF ratio is 75:15:10 wt% and coated to the cathode electrode for cyclic voltammetry tests. Experimental results showed that lithium iron phosphate powder was milled with zirconium beads 200 g in dimethyl sulfoxide (DMSO) solvent at 800 rpm for 1 hour. Its particle size was 234.7 nm that decreased 79.2 % compared with non-milled powder. As PVP protective agent was added, the uniformity of particle size and surface coating of lithium iron phosphate coated with nano silver was found in PVP of 10K. After 300 ℃ and 0.5 hr thermal treatment, the PVP polymer content with poor electric conductivity decreased 46.8 %. The capacity of capacitor was 84.24 mAh / g which increased capacitance of 15.80% compared to lithium iron phosphate without adding nano silver particles. Therefore, lithium iron phosphate coated with nano silver particles can improve the lithium ion diffusion and decrease electric conductivity.