Electrode-electrolyte interface in Li-ion batteries: current understanding and new insights

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Electrode/electrolyte interface (EEI) reactions are critical for lithium battery performance, impacting cycle life and safety.
• Despite decades of research, the formation mechanisms and property influences of EEI components remain incompletely understood.
• Existing models, like the mosaic structure for the solid electrolyte interphase (SEI) on negative electrodes, lack comprehensive understanding for positive electrodes.

Purpose of the Study:

• To review current understanding of EEI formation and properties in lithium batteries.
• To highlight the challenges in understanding EEI layers for advanced positive electrodes, particularly Li-rich layered oxides.
• To discuss the potential of in situ characterization techniques for mechanistic insights and tailoring EEI properties.

Main Methods:

• Literature review of established EEI models, focusing on negative electrode materials (Li, graphite, Sn, Si).
• Analysis of recent research on advanced positive electrodes, including Li-rich layered oxides and their reactivity.
• Examination of in situ characterization techniques for probing EEI formation and properties.

Main Results:

• The mosaic structure model for SEI on negative electrodes is well-established but understanding of positive electrode EEI is limited.
• Li-rich layered oxides present unique challenges due to reactive species generated via oxygen anion redox.
• In situ characterization offers promising avenues for mechanistic understanding and EEI tailoring.

Conclusions:

• A deeper understanding of EEI reactions is crucial for improving lithium battery cycle life and safety.
• Further research is needed to elucidate EEI formation and properties on advanced positive electrode materials.
• Advanced in situ techniques are vital for developing strategies to control EEI composition and enhance battery performance.