Sol-gel synthesis of Li₂CoPO₄F/C nanocomposite as a high power cathode material for lithium ion batteries

详细信息    查看全文

• 作者：Xiaobiao Wu ; Zhengliang Gong ; Shi Tan ; Yong Yang
• 关键词：Lithium cobalt fluorophosphate ; Lithium ion batteries ; Sol&ndash ; gel method ; High power density
• 刊名：Journal of Power Sources
• 出版年：2012
• 出版时间：15 December, 2012
• 年：2012
• 卷：220
• 期：Complete
• 页码：122-129
• 全文大小：2081 K

文摘

Li₂CoPO₄F cathode materials are successfully synthesized by solid state (SS) and sol-gel (SG) methods. The XRD results show that Li₂CoPO₄F samples prepared by two methods are both indexed as orthorhombic structure with space group Pnma. The particles of Li₂CoPO₄F (SS) are micron grade. However, the particle of Li₂CoPO₄F (SG) is only tens of nanometers with an amorphous carbon uniformly coated. A high reversible capacity of 138?mAh?g^?1 is achieved for Li₂CoPO₄F/C (SG) at 1?C, which is much higher than that of 106?mAh?g^?1 prepared by solid state method. Also, Li₂CoPO₄F/C (SG) shows excellent rate performance, a capacity of 119?mAh?g^?1, 86 % retention of that at 1?C, is achieved at 20?C. The excellent rate capacity of the material is attributed to nanosized particles and uniform carbon coating that reduce ion diffusion length and enhance electronic conductivity. Furthermore, the preliminary performance characteristics of Li₂CoPO₄F/Li₄Ti₅O₁₂ full cells are presented. The cell shows a high voltage plateau around 3.4?V with excellent rate capacity. The impressive electrochemical properties indicate that Li₂CoPO₄F can be a promising high power cathode material for lithium ion batteries. The capacity fading mechanism of Li₂CoPO₄F is also briefly investigated.