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Enhanced Lithiation Cycle Stability of ALD-Coated Confined a-Si Microstructures Determined Using In Situ AFM
Collin R Becker1, S M Prokes2, Corey T Love3
1Electrochemistry Branch, US Army Research Laboratory , 2800 Powder Mill Road, Adelphi, Maryland 20783, United States.
ACS Applied Materials & Interfaces
|December 18, 2015
Summary
Partially confined amorphous silicon (a-Si) structures with 3 nm aluminum oxide (Al2O3) coatings show improved battery performance. These advanced materials offer higher capacity, longer cycle life, and enhanced stability for next-generation energy storage.
Area of Science:
- Materials Science
- Electrochemistry
- Nanotechnology
Background:
- Amorphous silicon (a-Si) is a promising anode material for lithium-ion batteries due to its high theoretical capacity.
- Volume expansion during lithiation/delithiation leads to material degradation and poor cycle life in a-Si anodes.
- Confinement strategies and protective coatings are crucial for improving the stability and performance of a-Si anodes.
Purpose of the Study:
- To investigate the effect of partial confinement and aluminum oxide (Al2O3) atomic layer deposition (ALD) coatings on the electrochemical performance of amorphous silicon (a-Si) anodes.
- To evaluate the morphology evolution and solid electrolyte interphase (SEI) formation during cycling.
- To compare performance in different electrolyte formulations.
Main Methods:
- Fabrication of microfabricated a-Si pits (partially confined) and pillars (unconfined) on nickel current collectors.
- Coating of samples with varying thicknesses (1.5, 3, or 6 nm) of Al2O3 via ALD.
- Electrochemical cycling in various electrolytes (EC:EMC with LiPF6, with/without FEC, and pure FEC with LiPF6).
- In-situ atomic force microscopy (AFM) for morphology and SEI analysis during cycling.
Main Results:
- Partially confined a-Si structures exhibited superior cycle efficiency compared to unconfined a-Si pillars.
- The 3 nm Al2O3 ALD coating significantly enhanced charge capacity and cycle life.
- Samples with 3 nm Al2O3 ALD showed thinner SEI formation, maintained structural integrity, and even reduced in diameter after cycling.
- The 3 nm Al2O3 ALD coated samples demonstrated better capacity retention in the baseline EC:EMC electrolyte than in FEC-containing electrolytes.
Conclusions:
- Partial confinement and Al2O3 ALD coatings effectively mitigate the degradation issues associated with amorphous silicon anodes.
- A 3 nm Al2O3 ALD coating provides an optimal balance for enhancing electrochemical performance, stability, and SEI properties.
- The choice of electrolyte composition plays a role in the overall performance and capacity retention of the coated a-Si anodes.
