Multidimensional operando analysis of macroscopic structure evolution in lithium sulfur cells by X-ray radiography

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium sulfur (Li-S) batteries are leading post-lithium-ion technology.
• Rapid capacity fading in Li-S cells stems from poorly understood electrochemical processes.

Purpose of the Study:

• To investigate the precise electrochemical mechanisms causing capacity fading in Li-S cells.
• To correlate dynamic structural changes with electrochemical performance.

Main Methods:

• Operando X-ray radiography combined with impedance spectroscopy during galvanostatic cycling.
• Simultaneous electrochemical and structural analysis of Li-S cells in action.

Main Results:

• Direct visualization of macroscopic α-sulfur and β-sulfur crystal formation (>1 mm) during charging.
• Identification of growing non-wetted, electrochemically inactive areas on the cathode during discharge.
• Correlation of crystal formation and dissolution with impedance spectroscopy signals.

Conclusions:

• Macroscopic sulfur crystal dynamics and cathode wetting issues are key factors in Li-S battery capacity fading.
• Operando techniques provide critical insights into complex Li-S battery degradation mechanisms.