Title: Effect of Water Concentration in LiPF₆-Based Electrolytes on the Formation, Evolution, and Properties of the Solid Electrolyte Interphase on Si Anodes

Abstract

A trace amount of water in an electrolyte is one of the factors detrimental to the electrochemical performance of silicon (Si)-based lithium-ion batteries that adversely affect the formation and evolution of the solid electrolyte interphase (SEI) on Si-based anodes and change its properties. Thus far, a lack of fundamental and mechanistic understanding of SEI formation, evolution, and properties in the presence of water has inhibited efforts to stabilize the SEI for improved electrochemical performance. As such, we investigated the SEI formed in a Gen2 electrolyte (1.2 M LiPF6 in ethylene carbonate/ethyl methyl carbonate, 3:7 wt %, water content: <10 ppm) with and without additional water (50 ppm) at varying potentials (1.0, 0.5, 0.2, and 0.01 V vs Li/Li⁺). The impact of additional water on the morphological, (electro)chemical, and structural properties of SEI was studied using microscopic (atomic force microscopy and scanning spreading resistance microscopy) and spectroscopic (X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry) techniques. The SEI exhibits both potential- and water concentration-dependent trends in its morphology and chemical composition. The presence of additional water in the electrolyte causes parasitic reactions, which onset at ~1.0 V, resulting in a reduction of electrolyte componentsmore » and result in the formation of an insulating, fluorophosphate-rich SEI. In addition, hydrolysis of LiPF₆ creates hydrofluoric acid, which reacts with the surface oxide layer on the Si electrode, leading to a pitted and inhomogeneous SEI structure.« less

Authors:

Ha, Yeyoung  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-2679-2539"

Stetson, Caleb  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-0729-1261"

Harvey, Steven P.  ^[1];

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Teeter, Glenn ^[1]; Tremolet de Villers, Bertrand J.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-8685-539X"

Jiang, Chun-Sheng  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0230-7500"

Schnabel, Manuel ^[1]; Stradins, Paul ^[1]; Burrell, Anthony ^[1]; Han, Sang-Don  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-2931-659X"

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+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)

Publication Date:

Fri Oct 23 00:00:00 EDT 2020

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office

OSTI Identifier:

1726072

Report Number(s):

NREL/JA-5900-77016
Journal ID: ISSN 1944-8244; MainId:24979;UUID:9ef75457-3dff-41b8-8003-ce44d483289e;MainAdminID:18902

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 12; Journal Issue: 44; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; silicon-electrolyte interphase (SiEI); electrolyte water concentration; hydrolysis of LiPF6; fluorophosphates; surface pitting