Reversible anionic redox chemistry in high-capacity layered-oxide electrodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Classical lithium-ion battery positive electrodes rely on insertion-deinsertion redox mechanisms.
• Li-rich layered oxides exhibit high capacities but possess complex structures and compositions.
• Existing mechanisms are insufficient to explain the high performance of advanced Li-ion materials.

Purpose of the Study:

• To design and investigate novel Li-ion battery materials with enhanced capacity.
• To elucidate the redox mechanisms responsible for high reversible capacities in new materials.
• To explore the potential of Li₂MO₃ compounds for next-generation energy storage.

Main Methods:

• Synthesis of structurally related Li₂Ru(1-y)Sn(y)O₃ materials.
• Electrochemical characterization to assess reversible capacities and cycling behavior.
• Multiple characterization techniques to unambiguously determine the redox processes involved.

Main Results:

• Li₂Ru(1-y)Sn(y)O₃ materials exhibit sustainable reversible capacities up to 230 mA h g⁻¹.
• These materials demonstrate good cycling stability with minimal voltage decay and irreversible capacity.
• Reactivity involves cumulative cationic (M(n+)→M((n+1)+)) and anionic (O(2-)→O₂(2-)) redox processes.

Conclusions:

• The novel redox mechanism, involving d-sp hybridization and reductive coupling, explains the high capacity.
• Li₂MO₃ compounds represent a vast family with significant potential for high-capacity battery materials.
• This research paves the way for developing advanced materials for electric transportation and portable electronics.