Secondary Doping Effect for Practical Capacity Jumping of Layered Co-Based Lithium Ion Batteries Cathodes

摘要

Although LiCoO2 has high theoretical capapcity of 280 mAh/g, only a very limited amount of practical capacity of LiCoO2 has been realized, due to its irreversible deterioration when more than 0.6 mol of lithium ions are extracted. In this study, we applied new atomic control into the LiCoO2 to extend electrochemical reversibility. This material engineering alleviates the structural collapse caused by electrostatic repulsion between oxygen ions during the charge process. By applying substitution of Na ion into Li site, which produces a screen effect of cations in the 3b-Li site, the phase distortion of LiCoO2 is successfully delayed which in turn expands its electrochemical reversibility. As the result, modified LiCoO2 shows practical capacity of~190 mAh/g (4.5V) with good cycle performance. This study elucidates structural deterioaration mechanism of LiCoO2 and points out an alternative research direction by means of introducing fixed cations into the lithium sites of cobalt-based layered materials.