High-Resolution Tracking Asymmetric Lithium Insertion and Extraction and Local Structure Ordering in SnS2

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Rechargeable lithium-ion batteries rely on efficient ion transport and phase transitions in electrodes for optimal performance.
• Understanding lithium insertion/extraction mechanisms at the atomic scale is crucial for improving battery function and longevity.

Purpose of the Study:

• To investigate the real-time, atomic-scale dynamics of lithium ion insertion and extraction in van der Waals-dominated SnS2 electrodes.
• To elucidate the phase transition pathways governing electrode behavior during battery cycling.

Main Methods:

• In situ high-resolution transmission electron microscopy (TEM) for real-time observation of lithium ion processes.
• Density functional theory (DFT) calculations to analyze the stability and favored pathways of intermediate lithium tin sulfide phases.

Main Results:

• Lithium insertion proceeds via a rapid two-phase reaction, forming expanded and defective LiSnS2.
• Lithium extraction initiates with heterogeneous nucleation of Li0.5SnS2 superstructure domains (1-4 nm).
• DFT confirms Li0.5SnS2 as kinetically favored and structurally stable.

Conclusions:

• The observed asymmetric reaction pathways provide mechanistic insights into the electrochemistry of layered electrode materials.
• These findings challenge existing explanations for voltage hysteresis in intercalation electrodes and suggest alternative mechanisms.