First-principles molecular dynamics study on ultrafast potassium ion transport in silicon anode

Sangjin Lee, Sung Chul Jung, Young Kyu Han

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

Si is widely known as a high-capacity alloying anode material for lithium-ion batteries. However, Si is electrochemically inactive in potassium-ion batteries that attract considerable interest as cost-effective alternatives to lithium-ion batteries. Herein, we report that, unlike crystalline Si showing an inert nature toward K ions, amorphous Si is available as an alloying anode material for potassium-ion batteries. Amorphous Si can store 1.1 K ions per Si atom while offering a high capacity of 1049 mA h g−1. The K ions in amorphous Si can diffuse very rapidly. Their diffusivity is almost two orders of magnitude higher than that for Na ions in amorphous Si and is even three times higher than that for Li ions in amorphous Si. The fast K ion transport in amorphous Si is ascribed to the weak electrostatic K–Si attraction, fairly high carrier ion concentration, and the formation of isolated Sin (n = 3–5) clusters during the potassiation process. This work suggests that, despite alloying with large K ions, amorphous Si anodes can show high performance in both capacity and rate capability.

Original languageEnglish
Pages (from-to)119-125
Number of pages7
JournalJournal of Power Sources
Volume415
DOIs
StatePublished - 1 Mar 2019

Keywords

  • Alloying mechanism
  • Amorphous silicon
  • Anode
  • First-principles calculation
  • Ion transport
  • Potassium ion battery

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