Formulating Local Environment of Oxygen Mitigates Voltage Hysteresis in Li-rich Materials.

Li-rich cathode materials have emerged as one of the most prospective options for Li-ion batteries owing to their remarkable energy density (> 900 Wh kg -1 ). However, voltage hysteresis during charge and discharge process lowers the energy conversion efficiency, which hinders their application in practical devices. Herein, we unveil the fundamental reason for voltage hysteresis through investigating the O redox behavior under different (de)lithiation states and successfully address it by formulating the local environment of O 2- . In Li-rich Mn-based materials, we have confirmed that there exists reaction activity of oxygen ions at low discharge voltage (< 3.6 V) in the presence of TM-TM-Li ordered arrangement, generating massive amount of voltage hysteresis and resulting in a decreased energy efficiency (80.95%). Moreover, in the case where Li 2b sites are numerously occupied by TM ions, the local environment of O 2- evolves, the reactivity of oxygen ions at low voltage is significantly inhibited, thus giving rise to the large energy conversion efficiency (89.07%). This study unveils the structure-activity relationship between the local environment around O 2- and voltage hysteresis, which provides guidance in designing next-generation high-performance cathode materials. This article is protected by copyright. All rights reserved.