Reversible silicon anodes enabled by fluorinated inorganic-organic hybrid coating

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon anodes offer higher energy density than graphite anodes for advanced batteries.
• Key challenges include silicon's volume expansion and unstable interfaces, limiting cycle life and practical use.
• Current industrial Si/C composites use limited silicon content (<30 wt%) due to these issues.

Purpose of the Study:

• To enhance the stability and performance of silicon anodes for high-energy-density batteries.
• To develop a novel surface modification strategy for silicon electrodes.
• To investigate the formation and properties of a protective interphase layer.

Main Methods:

• Utilized molecular layer deposition (MLD) to apply a fluorine-rich inorganic-organic hybrid alucone (AlFHQ) shell onto silicon electrodes.
• Characterized the AlFHQ film using ex situ X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).
• Fabricated and tested Si@AlFHQ-20 anodes and full cells (Si@AlFHQ-20//LiCoO2@Al2O3).

Main Results:

• A mechanically-chemically robust, LiF-rich hybrid solid electrolyte interphase (SEI) was formed on the Si anode.
• The optimized 5 nm AlFHQ coating (Si@AlFHQ-20) improved interfacial stability and Li+ transport kinetics.
• Achieved stable cycling of Si anode with high initial Coulombic efficiency (ICE) of 92.3% and capacity of ~3.8 mAh cm-2.
• Demonstrated enhanced rate capability (1468 mAh/g at 2.0 A/g) and good cycling performance.
• The full cell operated stably for over 100 cycles under demanding cathode conditions (2.68 mAh cm-2, 4.55 V cutoff).

Conclusions:

• The fluorine-rich hybrid modification technique effectively stabilizes silicon anodes.
• This approach overcomes critical limitations of silicon anodes, enabling high-performance energy storage.
• The developed method paves the way for next-generation high-energy-density lithium-ion batteries.