A Theoretical Study of Growth of Solid-Electrolyte-Interphase Films in Lithium-Ion Batteries with Organosilicon Compound
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.78
A Theoretical Study of Growth of Solid-ElectrolyteInterphase Films in Lithium-Ion Batteries with Organosilicon Compounds Suguru Ueda1, Kumpei Yamada1, Kaoru Konno1, Minoru Hoshino1, Katsunori Kojima1, Naotaka Tanaka1 1
Advanced Technology Research & Development Center, Hitachi Chemical Co., Ltd., Ibaraki, Japan
ABSTRACT
We attempt to reveal how electrolyte additives affect the structural evolution of the solid electrolyte interphase (SEI) film on the anode surface of a lithium-ion secondary battery. Employing the hybrid Monte-Carlo/molecular-dynamics method, we theoretically investigate the SEI film structures in organic liquid-electrolyte systems with and without an organosilicon additive. The results show that the excessive growth of the SEI film is suppressed by introducing the organosilicon additives. It is further elucidated that the decomposition products of the organosilicon molecules are stably aggregated in the vicinity of the anode surface, and protect the electrolyte solvents and the lithium salts from the further reductive decomposition. These findings imply that the organosilicon additive possibly improves the cycle performance of LIBs owing to the formation of the effective SEI film.
INTRODUCTION For a past decade, a great deal of attention has been put toward the study of lithium-ion secondary batteries (LIB) owing to social demands for developing a new power source for electric vehicles and various portable electric devices. The performance of LIBs with organic liquid electrolytes is closely related to the formation of the solid electrolyte interphase (SEI) film on the anode surfaces, which is essentially composed from the decomposition products of the electrolyte solvents and the electrolyte additives [1]. Although this film essentially protects the electrolyte from further reductive decomposition during the charge-discharge cycles, it also increases the irreversible loss of the LIB capacity and the cell resistance as the SEI film thickness is excessively increased [2]. Therefore, controlling the SEI film structure is crucial for designing the long-lasting LIBs.
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It is widely accepted that electrolyte additives have a significant influence on the microscopic properties of the resulting SEI film structure. The variety of additives has been investigated, including organic and fluorinated carbonates [3]. The organosilicon (OS) compound have attracted recent attentions as a new candidate for electrolyte additives [4,5]. It has been reported in Ref. [4] that the added OS compound enhances the thermal and electrochemical stability of the electrolyte. However, since it is still difficult to experimentally observe the transient process of the SEI growth on the anode surface, atomistic simul
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