Insights into the Li Intercalation and SEI Formation on LiSi Nanoclusters. Issue 11 (21st June 2017)

• Record Type: Journal Article
• Authors: Hankins, Kie; Soto, Fernando A.; Balbuena, Perla B.
• Is Part Of: Journal of the Electrochemical Society. Volume 164:Issue 11(2017)
• Page Start: E3457
• Page End: E3464
• Publication Date: 2017-06-21
• Subjects: ab initio molecular dynamics -- density functional theory -- irreversible capacity -- lithiation -- SEI -- silicon anodes; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0311711jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : We report a first-principles atomic level assessment of the lithiation and reactivity of pre-lithiated Si clusters. Density functional theory formation energy calculations reveal that the pre-lithiated Li16 Si16 cluster exposed to two different Li fluxes can store Li between the concentrations of Li2.5 Si and Li3.5 Si. This increase in storage capacity is attributed to the start of an amorphization process in the cluster, and more importantly these results show that the intercalation reaction can be controlled by the flux of the Li-ions. However, in a real battery, the lithiation of the anode occurs simultaneously to the electrode-electrolyte reactions. Here we simulate the solid-electrolyte interphase (SEI) formation and simultaneous lithiation of a Li16 Si16 cluster in contact with two different electrolyte solutions: one with pure ethylene carbonate (EC), and another with a 0.6 M solution of LiPF6 in EC. Our ab initio molecular dynamics simulations show that the solvent and salt are decomposed leading to the initial stages of the SEI layer formation and large part of the added Li becomes part of the SEI. Interestingly, the pure EC solution results in lower storage capacity and higher reactivity, whereas the presence of the salt causes the opposite effect: higher lithiation and reduced reactivity.