Tuning Local Structural Configurations to Improve Oxygen-Redox Reversibility of Li-Rich Layered Oxides

Abstract

Li-rich layered oxides (LLOs) are regarded as one of the most desirable cathode materials due to their high specific capacity. Nevertheless, the irreversible oxygen release associated with low oxygen stability prevents their widespread application. Herein, an improved oxygen redox reversibility was achieved by constructing Ni 2+ −O 2− −Ni 2+ configurations. Superconducting Quantum Interference Device (SQUID) magnetometry measurements are used to track the evolution of the Ni 2+ −O 2− −Ni 2+ configuration during the electrochemical process. The strongest 180°s uperexchange interaction in the Ni 2+ −O 2− −Ni 2+ configuration, derived from the inevitable Li/Ni mixing in LLOs, regulates the local structure to form the ferrimagnetic (FiM) structural units. Consequently, the FiM structural units prevent the irreversible oxygen release and endow LLOs with high initial Coulombic efficiency (ICE). This work emphasizes the importance of the Ni 2+ −O 2− −Ni 2+ configuration for LLOs with high reversible capacity and proposes a synthesis approach to modulate the amount of FiM structural units.

Correlating concerted cations with oxygen redox in rechargeable batteries

“…Ni 2+ is the major electron-donating cation and has a long-term stable cationic redox capacity. So increasing Ni content can alter the redox center and positively affect the thermodynamics and kinetics of oxygen redox through the shielding effect 91,[124][125][126] (Fig. 11(h)).…”

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

“…At present, there is a lack of research on the source of the high specific capacity of layered Li-rich manganese-based materials. We generally explain the abnormal specific capacity of lithium-rich materials by the following mechanisms, such as the release of O 2 , , redox of Mn 2+ /Mn 3+ /Mn 4+ , insertion of protons, formation of peroxide ions, , and conversion of Mn 4+ to Mn 7+ . The main source of high specific capacity is the redox reaction of oxygen.…”