Spiers Memorial Lecture: Lithium air batteries - tracking function and failure.

Area of Science:

• Electrochemistry
• Materials Science
• Analytical Chemistry

Background:

• Lithium-air batteries (LABs) offer the highest theoretical energy density but face significant commercialization challenges.
• Understanding LAB function and failure is crucial for developing practical, high-performance energy storage solutions.

Purpose of the Study:

• To elucidate the operational mechanisms and failure modes of lithium-oxygen batteries using advanced experimental techniques.
• To identify and characterize electrolyte decomposition products and their impact on battery performance.

Main Methods:

• Utilized Nuclear Magnetic Resonance (NMR) spectroscopy, including 17O magic angle spinning (MAS) NMR, to quantify dissolved oxygen and analyze electrode composition.
• Employed redox mediators to mitigate electrode clogging and studied their mechanisms with NMR and Electron Paramagnetic Resonance (EPR).
• Implemented in situ NMR coupled with electrochemical impedance spectroscopy (EIS) to investigate charge transport and identify transient shorts in lithium symmetric cells.

Main Results:

• Quantified dissolved oxygen concentrations and diffusivity using NMR.
• Identified electrolyte decomposition products like Li2CO3 and LiOH in dimethoxyethane (DME) solvent and monitored their removal during charging.
• Demonstrated the formation of transient shorts in lithium-oxygen electrolytes and showed that solid electrolyte interphases formed under oxygen stabilize the lithium anode.

Conclusions:

• Advanced NMR and EIS techniques provide critical insights into lithium-air battery function and degradation pathways.
• Understanding electrolyte decomposition and charge transport is key to improving LAB stability and cycle life.
• Stabilizing the lithium anode through protective interphases is essential for practical lithium-air battery applications.