Regulation of 3d‐Transition Metal Interlayered Disorder by Appropriate Lithium Depletion for Li‐Rich Layered Oxide with Remarkably Enhanced Initial Coulombic Efficiency and Stability

Abstract

AbstractLi‐rich materials are among the most promising cathode materials for lithium‐ion batteries thanks to their high specific capacity. However, they exhibit poor structural stability, resulting in low initial Coulombic efficiency and limited cycle stability. Herein, a long‐neglected Li‐deficient state is realized for a Co‐free lithium‐rich cathode through a facile calcination medium‐induced surface‐corrosion (CMISC) strategy for alleviating the aforementioned drawbacks. The as‐constructed Li‐deficient lithium‐rich cathode of Li1.2‐σMn0.6Ni0.2O2 (d‐LMNO) exhibits an enhanced capacity of 272 mAh g−1, improved initial efficiency of 84.5%, and cycle stability with 82.0% retention over 200 cycles. In addition, multiple in situ and ex situ investigations confirm the appropriate lithium depletion regulated 3d‐transition metal interlayered disorder, resulting in excellent structural reversibility of d‐LMNO. Also, theory simulations suggest that the crystal structure with Li‐defects has lower energy and Li‐diffusion energy barrier when the coordination interlayer 3d‐metal has more Ni closer to the diffused Li, meaning less interlayered disorder. And the migration of Li close to the vacancy is dominated by a tetrahedral site hopping path in the presence of additional vacancies around the Li vacancy, which has a low migration energy barrier. Moreover, similar results achieved in Co‐containing Li‐rich cathodes further demonstrate the universality of this simple CMISC strategy, exhibiting great potential for performance improvement and applicability.