In Situ Construction of Specific SEI Layer Affords Effective Prelithiation

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon-based anodes offer high theoretical capacity for lithium-ion batteries.
• Low initial Coulombic efficiency (ICE) and volume expansion limit their commercial use.
• Direct contact prelithiation is a promising strategy to address these limitations.

Purpose of the Study:

• To investigate the effectiveness of direct contact prelithiation in enhancing silicon-based anodes.
• To understand the role of the solid electrolyte interphase (SEI) formed during prelithiation.
• To improve the cycling stability and initial Coulombic efficiency (ICE) of SiO/C composite anodes.

Main Methods:

• Direct contact prelithiation of SiO/C composite anodes.
• Electrolyte formulation using LiTFSI as the main component.
• Surface analysis using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS).
• Electrochemical performance testing of full cells with NCM111 cathodes.

Main Results:

• A stable SEI layer, primarily composed of LiF, was constructed using LiTFSI-based electrolyte.
• Prelithiation process was slowed, reducing local current and side reactions.
• Volume expansion of the SiO/C anode during prelithiation was effectively inhibited.
• Full cells demonstrated 83.5% capacity retention after 500 cycles at 1 C.

Conclusions:

• Direct contact prelithiation with LiTFSI-based electrolyte successfully forms a protective LiF-rich SEI layer.
• This strategy mitigates volume expansion and side reactions, enhancing anode performance.
• The approach offers a viable pathway for developing high-performance silicon-based anodes for next-generation batteries.