Understanding the Electrolyte Chemistry Induced Enhanced Stability of Si Anodes in Li-Ion Batteries based on Physico-Chemical Changes, Impedance, and Stress Evolution during SEI Formation
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Published:2023-09-01
Issue:9
Volume:170
Page:090544
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ISSN:0013-4651
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Container-title:Journal of The Electrochemical Society
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language:
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Short-container-title:J. Electrochem. Soc.
Author:
Tripathi Rashmi,
Yesilbas GöktugORCID,
Lamprecht Xaver,
Gandharapu Pranay,
Bandarenka Aliaksandr S.,
Dusane Rajiv O.,
Mukhopadhyay AmartyaORCID
Abstract
The volume expansion/contraction of Si-based anodes during electrochemical lithiation/delithiation cycles causes a loss in mechanical integrity and accrued instability of the solid electrolyte interphase (SEI) layer, culminating into capacity fade. Electrolyte additives like fluoroethylene carbonate (FEC) improve SEI stability, but the associated causes still under debate. This work reveals some of the roles of FEC via post-mortem observations/analyses, operando stress measurements and a comprehensive study of the impedance associated with the formation/evolution of SEI during lithiation/delithiation. Usage of 10 vol.% FEC as electrolyte additive leads to significant improvements in cyclic stability, Coulombic efficiency and facilitates smoother/compact/crack-free surface/SEI, in contrast to the cracked/pitted/uneven surface upon non-usage of FEC. Operando stress measurements during SEI formation reveal compressive stress development, followed by loss in mechanical integrity, upon non-usage of electrolyte additive, in contrast to insignificant stress development associated with SEI formation upon usage of FEC. The EIS model proposed here facilitates good fit with the impedance data at all states-of-charges, with the SEI resistance and capacitance exhibiting expected variations with cycling and the SEI resistance progressively decreasing with cycle number in the presence of FEC. By contrast, in the absence of FEC, severe fluctuations observed with the SEI resistance and capacitance indicate instability.
Funder
UGC-DAAD Programme for the Indo-German Partnership in Higher Education Programme
Department of Science and Technology, Gov. of India
German Research Foundation (DFG) under Germany’s Excellence Strategy
Publisher
The Electrochemical Society
Subject
Materials Chemistry,Electrochemistry,Surfaces, Coatings and Films,Condensed Matter Physics,Renewable Energy, Sustainability and the Environment,Electronic, Optical and Magnetic Materials