Relationship between Voltage Hysteresis and Voltage Decay in Lithium-Rich Layered Oxide Cathodes

Voltage decay and voltage hysteresis are important limitations in the commercial application of Li-rich Mn-based layered oxide (LRO) as a cathode material in the next-generation high-energy-density Li-ion batteries. Although significant progress in studies on the voltage decay mechanism has been made, the evolution of voltage decay and its relationship with voltage hysteresis need to be further understood. Herein, a detailed investigation of the evolution of voltage decay and its relationship with voltage hysteresis for LRO is performed via spherical aberration-corrected transmission electron microscopy, in situ X-ray powder diffraction, ex situ X-ray absorption spectroscopy, and galvanostatic intermittent titration technique. The results reveal that the initial voltage hysteresis is mainly related to the anionic redox process. Due to the surface structural change, the kinetic process of surface deintercalation of lithium slows down, and the voltage hysteresis becomes more and more serious during charge and discharge, which is shown by the continuous increase of voltage decay. This finding can open up a new pathway for developing a strategy for suppressing voltage decay in high-capacity Li-rich Mn-based layered materials.