Novel chemistry of lithium oxides and superconducting low-pressure LiO4

TL;DR

This study predicts new lithium-oxygen compounds, including a superconducting LiO4 phase stable at low pressure, highlighting potential for novel superconductors and chemical insights into oxygen and lithium interactions.

Contribution

The paper introduces the prediction of novel Li-O compounds, especially LiO4, which is superconducting at low pressure, expanding understanding of lithium-oxygen chemistry and superconductivity.

Findings

LiO4 is stable at 6 GPa and superconducts up to 12.2 K.

LiO4 is formed by -O8 accepting electrons from lithium.

New stable compounds Li5O3 and Li6O identified at high pressures.

Abstract

We study the stability of Li-O compounds as a function of pressure, with Li ion battery applications and fundamental chemical interest in mind. Using the ab initio evolutionary algorithm, we predict stability of novel compounds LiO4, Li5O3 and Li6O under pressure. LiO4, formed at the pressure of just 6 GPa, can be seen as {\epsilon}-O8 accepting two electrons from two Li atoms. This phase is superconducting, with Tc up to 12.2 K at 10 GPa. This is remarkable, because elemental oxygen becomes superconducting at much higher pressure (96 GPa) and has much lower Tc (<0.6 K), and suggests that chemical alloying with other elements has the potential of not only decreasing metallization pressure, but also of increasing Tc. Since {\epsilon}-O8 is called red oxygen, LiO4 can be identified "lithium red-oxid", and is distinct from superoxide. Additionally, Li5O3 is stable at pressures above 70 GPa and can be represented as a hybrid structure 4Li2O {\cdot} Li2O2, and electride suboxide Li6O is stable above 62 GPa.