Real-Time Imaging of Intercalation-Conversion Li Storage in MXenes for Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Two-dimensional transition metal carbides and nitrides (MXenes) are advanced electrode materials for next-generation energy storage devices.
• Understanding charge storage mechanisms in MXenes within solid-state systems is crucial for optimizing battery performance.

Purpose of the Study:

• To directly visualize and understand Li-ion intercalation and conversion reactions in Ti3C2Tx MXenes within sulfide-based solid-state Li batteries.
• To investigate the influence of surface terminations on Li-ion accommodation and redox activity.

Main Methods:

• Operando scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS).
• Real-time nanoscale observation of electrochemical reactions in solid-state Li batteries.

Main Results:

• Identified three distinct reaction pathways: Li (de)intercalation with Ti redox, reversible Li2O formation/decomposition on the surface, and sulfide electrolyte decomposition.
• Demonstrated that O-terminated MXenes facilitate efficient Li accommodation and room-temperature redox activity.
• Showed that F- and Cl-terminated MXenes require elevated temperatures for adequate Li penetration.

Conclusions:

• Provided direct nanoscale evidence of intercalation and conversion processes in MXenes for solid-state batteries.
• Highlighted surface-termination engineering as a key strategy to enhance Li accommodation and redox utilization in all-solid-state batteries.