Free-Standing Si/Graphene Paper Using Si Nanoparticles Synthesized by Acid-Etching Al-Si Alloy Powder for High-Stability Li-Ion Battery Anodes

• Acid-etching Al-Si alloy powder approach was successfully applied to synthesize Si nanoparticles.
• A free-standing Si/graphene paper was further prepared using the as-synthesized Si nanoparticles for Li-ion battery anode.
• The Si/G paper delivered a high reversible discharge capacity of 1650 mAh g−1 and remained 1500 mAh g−1 even after 100 cycles.

Developing scalable, simple and low-cost synthesis approach for Si nanoparticles and fabricating Si/carbon composites with specific microstructure to improve the Li storage ability are of great significance for practical application of Si-based Li-ion battery anode. In this report, we employed a facile method to synthesize Si nanoparticles via acid-etching Al-Si alloy powder. The etching process was fully investigated. The as-synthesized Si nanoparticles (∼10 nm) were further embedded into graphene sheets to form a flexible, free-standing paper with “sandwich-like” structure. The Si/graphene paper was directly applied as anode for Li-ion batteries without adding any binder and conductive additive. The graphene sheets not only increase the conductivity of Si material, but also function as a flexible scaffold for strains/stresses release and volume expansion during charge/discharge cycling process, resulting in much higher cycling stability (1500 mAh g−1 after 100 cycles at a current density of 100 mA g−1 with Coulombic efficiency >99%) compared to the native Si nanoparticles. It provides a scalable Si nanoparticles synthesis approach and a promising high-performance Si/graphene anode material.

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