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Title: The lithiation process and Li diffusion in amorphous SiO 2 and Si from first-principles

Abstract

Silicon is considered the next-generation, high-capacity anode for Li-ion energy storage applications, however, despite significant effort, there are still uncertainties regarding the bulk Si and surface SiO2 structural and chemical evolution as it undergoes lithiation and amorphization. In this paper, we present first-principles calculations of the evolution of the amorphous Si anode, including its oxide surface layer, as a function of Li concentration. We benchmark our methodology by comparing the results for the Si bulk to existing experimental evidence of local structure evolution, ionic diffusivity as well as electrochemical activity. Recognizing the important role of the surface Si oxide (either native or artificially grown), we undertake the same calculations for amorphous SiO2, analyzing its potential impact on the activity of Si anode materials. Derived voltage curves for the amorphous phases compare well to experimental results, highlighting that SiO2 lithiates at approximately 0.7 V higher than Si in the low Li concentration regime, which provides an important electrochemical fingerprint. The combined evidence suggests that i) the inherent diffusivity of amorphous Si is high (in the order 10-9cm2s-1 - 10-7cm2s-1), ii) SiO2 is thermodynamically driven to lithiate, such that Li–O local environments are increasingly favored as compared to Si–O bonding, iii) themore » ionic diffusivity of Li in LiySiO2 is initially two orders of magnitude lower than that of LiySi at low Li concentrations but increases rapidly with increasing Li content and iv) the final lithiation product of SiO2 is Li2O and highly lithiated silicides. Hence, this work suggests that - excluding explicit interactions with the electrolyte - the SiO2 surface layer presents a kinetic impediment for the lithiation of Si and a sink for Li inventory, resulting in non-reversible capacity loss through strong local Li–O bond formation.« less

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1576700
Alternate Identifier(s):
OSTI ID: 1599839
Grant/Contract Number:  
SC0014607; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Electrochimica Acta
Additional Journal Information:
Journal Name: Electrochimica Acta Journal Volume: 331 Journal Issue: C; Journal ID: ISSN 0013-4686
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English
Subject:
25 ENERGY STORAGE; Li-Ion batteries; Alloy anodes; Silicon anode; Density functional theory calculations; Ab-initio molecular dynamics

Citation Formats

Sivonxay, Eric, Aykol, Muratahan, and Persson, Kristin A. The lithiation process and Li diffusion in amorphous SiO 2 and Si from first-principles. United Kingdom: N. p., 2020. Web. doi:10.1016/j.electacta.2019.135344.
Sivonxay, Eric, Aykol, Muratahan, & Persson, Kristin A. The lithiation process and Li diffusion in amorphous SiO 2 and Si from first-principles. United Kingdom. doi:10.1016/j.electacta.2019.135344.
Sivonxay, Eric, Aykol, Muratahan, and Persson, Kristin A. Wed . "The lithiation process and Li diffusion in amorphous SiO 2 and Si from first-principles". United Kingdom. doi:10.1016/j.electacta.2019.135344.
@article{osti_1576700,
title = {The lithiation process and Li diffusion in amorphous SiO 2 and Si from first-principles},
author = {Sivonxay, Eric and Aykol, Muratahan and Persson, Kristin A.},
abstractNote = {Silicon is considered the next-generation, high-capacity anode for Li-ion energy storage applications, however, despite significant effort, there are still uncertainties regarding the bulk Si and surface SiO2 structural and chemical evolution as it undergoes lithiation and amorphization. In this paper, we present first-principles calculations of the evolution of the amorphous Si anode, including its oxide surface layer, as a function of Li concentration. We benchmark our methodology by comparing the results for the Si bulk to existing experimental evidence of local structure evolution, ionic diffusivity as well as electrochemical activity. Recognizing the important role of the surface Si oxide (either native or artificially grown), we undertake the same calculations for amorphous SiO2, analyzing its potential impact on the activity of Si anode materials. Derived voltage curves for the amorphous phases compare well to experimental results, highlighting that SiO2 lithiates at approximately 0.7 V higher than Si in the low Li concentration regime, which provides an important electrochemical fingerprint. The combined evidence suggests that i) the inherent diffusivity of amorphous Si is high (in the order 10-9cm2s-1 - 10-7cm2s-1), ii) SiO2 is thermodynamically driven to lithiate, such that Li–O local environments are increasingly favored as compared to Si–O bonding, iii) the ionic diffusivity of Li in LiySiO2 is initially two orders of magnitude lower than that of LiySi at low Li concentrations but increases rapidly with increasing Li content and iv) the final lithiation product of SiO2 is Li2O and highly lithiated silicides. Hence, this work suggests that - excluding explicit interactions with the electrolyte - the SiO2 surface layer presents a kinetic impediment for the lithiation of Si and a sink for Li inventory, resulting in non-reversible capacity loss through strong local Li–O bond formation.},
doi = {10.1016/j.electacta.2019.135344},
journal = {Electrochimica Acta},
number = C,
volume = 331,
place = {United Kingdom},
year = {2020},
month = {1}
}

Journal Article:
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DOI: 10.1016/j.electacta.2019.135344

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