Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li-Rich Layered Oxide

摘要

Li-rich layered metal oxides are one type of the most promising cathode materials in lithium-ion batteries but suffer from severe voltage decay during cycling because of the continuous transition metal (TM) migration into the Li layers. A Li-rich layered metal oxide Li1.2Ti0.26Ni0.18Co0.18Mn0.18O2 (LTR) is hereby designed, in which some of the Ti4+ cations are intrinsically present in the Li layers. The native Li-Ti cation mixing structure enhances the tolerance for structural distortion and inhibits the migration of the TM ions in the TMO2 slabs during (de)lithiation. Consequently, LTR exhibits a remarkable cycling stability of 97% capacity retention after 182 cycles, and the average discharge potential drops only 90 mV in 100 cycles. In-depth studies by electron energy loss spectroscopy and aberration-corrected scanning transmission electron microscopy demonstrate the Li-Ti mixing structure. The charge compensation mechanism is uncovered with X-ray absorption spectroscopy and explained with the density function theory calculations. These results show the superiority of introducing transition metal ions into the Li layers in reinforcing the structural stability of the Li-rich layered metal oxides. These findings shed light on a possible path to the development of Li-rich materials with better potential retention and a longer lifespan.