Multiprobe Study of the Solid Electrolyte Interphase on Silicon-Based Electrodes in Full-Cell Configuration.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Silicon-based electrodes are promising for high-capacity lithium-ion cells.
• Previous studies on silicon electrode failure mechanisms were limited to half-cell configurations.
• Understanding failure in full cells is crucial for practical battery development.

Purpose of the Study:

• To investigate the failure mechanism of silicon-based electrodes in a full Li-ion cell configuration.
• To characterize the solid electrolyte interphase (SEI) formation and evolution on silicon anodes.
• To compare failure modes in full cells versus traditional half-cells.

Main Methods:

• Utilized a combination of advanced characterization techniques: 7Li, 19F MAS NMR, XPS, TOF-SIMS, and STEM-EELS.
• Analyzed SEI formation on silicon anodes paired with LiNi1/3Mn1/3Co1/3O2 cathodes in a full cell.
• Examined electrode and SEI evolution during aging and cycling.

Main Results:

• SEI formation in full cells shares similarities with half-cells during early cycling stages, with inorganic SEI development and continuous organic electrolyte degradation.
• Extended cycling leads to parasitic reactions consuming all cyclable lithium, trapping it within the SEI or electrolyte.
• Lithium depletion, not physical clogging or disconnection, is identified as the primary failure cause in full cells.

Conclusions:

• The failure mechanism of silicon-based anodes in full Li-ion cells differs significantly from half-cell configurations.
• Parasitic reactions leading to lithium loss are the dominant failure mode, preceding physical degradation of electrode structure.
• The study highlights the critical role of cyclable lithium availability in full cell performance and longevity.