Role of conductive binder to direct solid-electrolyte interphase formation over silicon anodes

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Amorphous silicon (a-Si) anodes offer high capacity for lithium-ion batteries.
• Solid-electrolyte interphase (SEI) formation is critical for anode stability and battery life.
• Understanding SEI evolution is key to improving battery performance.

Purpose of the Study:

• To investigate the role of a conductive polymeric binder, PEFM, in SEI formation on a-Si anodes.
• To analyze the impact of state-of-charge on SEI composition and structure.
• To elucidate the mechanism by which PEFM mediates SEI evolution.

Main Methods:

• In situ neutron reflectometry (NR) was employed to monitor SEI formation in real-time.
• Amorphous silicon (a-Si) electrodes were used in conjunction with a PEFM binder and electrolyte.
• Electrode polarization was performed at various potentials (0.8 V to 0.05 V vs. Li/Li+).

Main Results:

• A Li-rich layer formed initially, followed by an organic SEI layer at 0.8 V with PEFM swelling due to solvent uptake.
• At lower potentials (0.4 V, 0.15 V), a thick, diffuse interfacial layer formed with electrolyte-rich PEFM and SEI intermixing.
• At 0.05 V, a condensed Li-rich SEI formed with an intermixed layer containing LiF and Li-C-O species.

Conclusions:

• The conductive binder PEFM actively mediates SEI formation and composition on a-Si anodes.
• PEFM's interaction with the electrolyte and SEI influences solvent uptake and layer morphology.
• The observed SEI evolution suggests a mechanism that may hinder a-Si lithiation, requiring further investigation for battery optimization.