Lithiation of silicon via lithium Zintl-defect complexes

TL;DR

This study identifies a highly stable four-lithium-atom defect in silicon, resembling Zintl phases, which could influence silicon's behavior in lithium-ion batteries and aid its amorphization.

Contribution

It reveals a novel stable lithium defect complex in silicon using density-functional theory and AIRSS, providing insights into silicon lithiation mechanisms.

Findings

Four-lithium-atom defect is exceptionally stable in silicon.

The defect involves strong ionic bonds similar to Zintl phases.

Potential role in silicon amorphization and battery anode delithiation.

Abstract

An extensive search for low-energy lithium defects in crystalline silicon using density-functional-theory methods and the ab initio random structure searching (AIRSS) method shows that the four-lithium-atom substitutional point defect is exceptionally stable. This defect consists of four lithium atoms with strong ionic bonds to the four under-coordinated atoms of a silicon vacancy defect, similar to the bonding of metal ions in Zintl phases. This complex is stable over a range of silicon environments, indicating that it may aid amorphization of crystalline silicon and form upon delithiation of the silicon anode of a Li-ion rechargeable battery.