Tracking Decomposition Layer Formation in Thin-Film Si Electrodes via Thermogalvanic Profiles

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Silicon anodes are promising for next-generation Li-ion batteries due to their high energy density.
• Electrolyte decomposition on silicon anodes leads to capacity fade and poor Coulombic efficiency, hindering their practical application.

Purpose of the Study:

• To investigate the influence of the electrolyte decomposition layer on silicon anodes' electrochemical performance.
• To understand the evolution and impact of the decomposition layer during battery cycling.

Main Methods:

• Utilized thermogalvanic profiling, a non-destructive in operando technique, to study silicon anodes.
• Compared uncoated silicon thin films with lithium phosphorus oxynitride (LiPON)-coated silicon to inhibit decomposition.
• Employed scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for physico-chemical analysis.

Main Results:

• Thermogalvanic profiles revealed signatures corresponding to the nature of the decomposition layer on silicon.
• The decomposition layer initially exhibited a passivating function during early electrochemical cycles.
• Later cycles showed a loss of this passivating behavior, correlating with observed capacity degradation.

Conclusions:

• The formation and eventual loss of a passivating layer on silicon anodes are critical factors in their electrochemical performance and capacity fade.
• Thermogalvanic profiling is a valuable tool for monitoring the state and evolution of decomposition layers in battery cells.
• Understanding these decomposition dynamics is essential for developing stable, high-capacity silicon-based Li-ion batteries.