Capturing dynamic ligand-to-metal charge transfer with a long-lived cationic intermediate for anionic redox
Biao Li1,2, Khagesh Kumar3, Indrani Roy3
1Chimie du Solide-Energie, UMR 8260, Collège de France, Paris, France.
Nature Materials
|June 21, 2022
Summary
Reversible anionic redox reactions in Li-ion batteries are activated by ligand-to-metal charge transfer (LMCT). This study experimentally validates LMCT in a disordered rock-salt material, revealing a Ni3+/4+ intermediate crucial for high-energy-density electrodes.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-State Chemistry
Background:
- Reversible anionic redox reactions are key for high-energy-density lithium-ion battery cathodes.
- Ligand-to-metal charge transfer (LMCT) is hypothesized as the activation mechanism but lacks experimental validation.
- Developing suitable model materials is essential for understanding anionic redox.
Purpose of the Study:
- To experimentally validate the ligand-to-metal charge transfer (LMCT) mechanism in anionic redox reactions.
- To investigate the role of intermediate nickel species in the activation of anionic redox.
- To provide insights into designing advanced high-capacity battery electrodes.
Main Methods:
- Electrochemical analysis of Li1.17Ti0.58Ni0.25O2.
- Spectroscopic techniques to identify reaction intermediates.
- Quantitative analysis of charge transfer processes.
Main Results:
- Experimental evidence for a long-lived Ni3+/4+ intermediate species during anionic redox activation.
- Quantitative identification of a dynamic LMCT process (Ni3+/4+-O2- → Ni2+-On-) during reduction.
- Validation of theoretical hypotheses regarding anionic redox mechanisms.
Conclusions:
- The study provides the first experimental validation of LMCT in anionic redox activation.
- Findings rationalize phenomena like redox inversion and voltage hysteresis in Li-ion batteries.
- Results guide the design of novel high-capacity electrode materials by selecting appropriate cationic species for LMCT mediation.
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