2008-01-012024-05-15https://scholars.lib.ntu.edu.tw/handle/123456789/665872摘要：在以表層披覆碳並降低電解液阻抗後，許多研究證實LiFePO4具有10C以上充放電的能力。尤其在實際電動車應用中高溫(40~55oC) 條件下，充放電能力更大為提昇。有別於其他正極材料的地方在於，LiFePO4在鋰離子嵌入或嵌出時，理論上牽涉LiFePO4與FePO4的相轉換。對於一個固態相轉換反應來說，何以如此的兩相反應竟然能提供如此高速的充放電性能，是有待澄清的一個議題。另者，文獻亦指出LiFePO4在高溫充放電時，鐵離子(Fe+2)易於溶出，當其還原析出於負極表面時造成提高阻抗，電容量衰退的問題。本研究擬以兩年的時間，探討相關議題，以提昇該材料在高功率電池之實際應用價值。第一年預定完成： LiFePO4正極充放電過程臨場(in situ)同步輻射X光繞射的研究分析，剖析高速率充放電中相轉換的機制，及完成Fe2+離子收集層以提升循環壽命之設計與最適化的探討。第二年預定完成LiFePO4正極粉體結構表徵設計，以提高充放電速率的研發，並研發電解質添加劑以降低Fe2+離子自LiFePO4正極溶出之機制。<br> Abstract: By carbon coating and reducing electrolyte resistance, LiFePO4 cathode has been shown in several studies to exhibit 10C rate capability. In particular, when subjected to elevated temperature environment for EV application, the rate capability can further be enhanced. Unlike other intercalation cathode materials, charge/discharge between LiFePO4/FePO4 involves structural transformation. Therefore, how such a transformation process responds to the high rate electrochemical process remains unclear. Furthermore, it has also been pointed out that, upon C/D at elevated temperatures, Fe+2 ions tend to be dissolved into the electrolyte and subsequently reduced at anode, causing serious capacity fading. This project is designed to investigate the subjects pertain to the high-temperature performance of the LiFePO4 cathode. For the first year, we will investigate, by using in-situ synchrotron XRD, the structural transformation process under high rate conditions, and also develop a mechanism that can collect the Fe+2 in the electrolyte to prevent it to be reduced at the graphite anode surface in order to enhance the cycle stability. For the second year, we will focus on the modification of the particle microstructure of the olivine particles in order to enhance the rate capability, and develop electrolyte additive for reducing Fe+2 dissolution.鋰離子電池鋰鐵磷鹽正極材料高速充放電循環壽命高溫充放電性能Li-ion batteryLiFePO4high rate capabilityhigh-temperaturecycling stability