Operando structural study of non-aqueous Li-air batteries using synchrotron-based X-ray diffraction

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Non-aqueous lithium-air batteries (LABs) are promising for next-generation energy storage.
• Understanding lithium peroxide (Li₂O₂) formation and decomposition is key to improving LAB cycle performance and reducing charge voltage.

Purpose of the Study:

• To investigate the real-time formation and decomposition mechanisms of crystalline Li₂O₂ during the operation of non-aqueous LABs.
• To elucidate the Li-O₂ electrochemical reaction pathways involving Li₂O₂.

Main Methods:

• Utilized *operando* X-ray diffraction (XRD) with high-brilliant X-rays in transmission mode.
• Real-time observation of intensity and structural changes of crystalline Li₂O₂ in an operating non-aqueous LAB.

Main Results:

• Clearly demonstrated the Li-O₂ electrochemical reaction involving Li₂O₂ formation and decomposition.
• Observed anisotropic growth of electrochemically formed Li₂O₂ domains (10 nm in c-direction, 40-70 nm in ab-plane) during discharge.
• Identified accelerated decomposition of Li₂O₂ domains with shape and lattice changes above 4 V during charge, with no crystalline LiOH detected.

Conclusions:

• The study provides direct real-time insights into Li₂O₂ dynamics in non-aqueous LABs.
• Understanding Li₂O₂ domain evolution is critical for optimizing LAB charge/discharge processes and enhancing battery longevity.