Atomistic Simulation Derived Insight on the Irreversible Structural Changes of Si Electrode during Fast and Slow Delithiation

Kwang Jin Kim, James Wortman, Sung Yup Kim, Yue Qi

Research output: Research - peer-reviewArticle

  • 2 Citations

Abstract

Quantifying the irreversible chemical and structural changes of Si during cycling remains challenging. In this study, a continuous reactive molecular dynamics delithiation algorithm, with well-controlled potential gradient and delithiation rate, was developed and used to investigate the "natural" delithiation responses of an aluminum-oxide coated silicon thin-film. Fast delithiation led to the formation of dense Si network near the surface and nanoporosity inside the a-LixSi, resulting in 141% volume dilation and significant amount of Li trapped inside (a-Li1.2Si) at the end of delithiation process. In contrast, slow delithiation allowed the a-LixSi to shrink by near-equilibrium condition, demonstrating no permanent inner pore with nearly Li-free structure (a-Li0.2Si) and minimal volume dilation (44%). However, even without trapped Li, the delithiated a-LixSi still exhibited higher volume (lower density) than the equilibrium structure with the same Li concentration, despite delithiation rate. The origin of this excess volume is the loss of directly bonded Si-Si pairs, which made the subsequent relithiation faster. On the basis of the atomistic modeling and the quantified degradation mechanism, battery operating guidelines, including the delithiation rate and the depth of charge to avoid trapped Li and coating delamination, were suggested to improve the durability Si electrodes.

LanguageEnglish (US)
Pages4330-4338
Number of pages9
JournalNano Letters
Volume17
Issue number7
DOIs
StatePublished - Jul 12 2017

Profile

Delamination
Molecular dynamics
Durability
Aluminum
Degradation
Thin films
Silicon
Coatings
Electrodes
Oxides
Aluminum Oxide
electrodes
simulation
potential gradients
durability
electric batteries
aluminum oxides
degradation
molecular dynamics
porosity

Keywords

  • coating delamination
  • irreversible capacity loss
  • Lithium ion batteries
  • molecular dynamics
  • nanosized silicon

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Cite this

Atomistic Simulation Derived Insight on the Irreversible Structural Changes of Si Electrode during Fast and Slow Delithiation. / Kim, Kwang Jin; Wortman, James; Kim, Sung Yup; Qi, Yue.

In: Nano Letters, Vol. 17, No. 7, 12.07.2017, p. 4330-4338.

Research output: Research - peer-reviewArticle

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