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Kinetic Regulation of Anionic Redox Reaction Voltage by Metastable Over-Lithiated Surface Shells Formation for
Keqiang Li1, Yande Li2, Yiming Wang1
1College of Physics, Center For Marine Observation and Communications, Qingdao University, Qingdao, China.
Angewandte Chemie (International Ed. in English)
|June 25, 2026
Summary
Anionic redox reactions (ARR) in high-energy batteries are limited by low operating voltage. A metastable surface shell in Li-rich cathodes creates a barrier, hindering Li-ion transfer and reducing battery performance.
Area of Science:
- Materials Science
- Electrochemistry
- Battery Technology
Background:
- Anionic redox reactions (ARR) are crucial for high-energy-density batteries.
- ARR operating voltage and hysteresis are key limitations for practical battery applications.
- Understanding ARR voltage origins is vital for improving battery efficiency.
Purpose of the Study:
- Investigate factors influencing ARR operating voltage in Li1.17Ti0.58Ni0.25O2 (LTNO).
- Elucidate the role of surface phenomena and Li-ion kinetics in ARR voltage.
- Provide guidelines for optimizing ARR performance in next-generation batteries.
Main Methods:
- Utilized in situ XRD, TEM, sXAS, and RIXS to study kinetic regulation.
- Employed depth-resolved Li 1s XPS and Li-K sXAS to analyze Li distribution and sites.
- Investigated a unique LTNO model system with an isolated ARR plateau.
Main Results:
- Identified a metastable over-lithiated surface shell on LTNO with Li-ions in tetrahedral coordination.
- Demonstrated that this surface shell creates a significant energy barrier for Li-ion transfer, leading to a low ARR plateau.
- Validated kinetic regulation of transition metal redox and ARR voltages.
Conclusions:
- The surface shell's Li-ion transfer barrier is a primary cause of low ARR voltage.
- Kinetics significantly impact ARR voltage, potentially explaining voltage decay in Li-rich cathodes.
- Facilitating Li transfer kinetics offers a pathway to optimize ARR performance in advanced batteries.
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