Electronic phase diagram of LixCoO2 revisited with potentiostatically de-intercalated single crystals

TL;DR

This study revisits the electronic phase diagram of LixCoO2 using single crystals de-intercalated potentiostatically, identifying stable phases and magnetic properties, and clarifying the absence of superlattice ordering and the nature of magnetic anomalies.

Contribution

It provides a detailed phase diagram of LixCoO2 with stable phases and magnetic orderings, using a refined potentiostatic de-intercalation method on single crystals.

Findings

Identified stable phases at x ~ 0.87, 0.72, 0.53, 0.50, 0.43, 0.33.

Observed magnetic orderings similar to NaxCoO2 system.

Did not find Li vacancy superlattice ordering at x ~ 0.72.

Abstract

Electronic phase diagram of LixCoO2 has been re-examined using potentiostatically de-intercalated single crystal samples. Stable phases of x ~ 0.87, 0.72, 0.53, 0.50, 0.43, and 0.33 were found and isolated for physical property studies. A-type and chain-type antiferromagnetic orderings have been suggested from magnetic susceptibility measurement results in x ~ 0.87 and 0.50 below ~ 10 K and 200 K, respectively, similar to those found in NaxCoO2 system. There is no Li vacancy superlattice ordering observed at room temperature for the electronically stable phase Li0.72CoO2 as revealed by synchrotron X-ray Laue diffraction. The peculiar magnetic anomaly near ~ 175 K as often found in powder samples of x ~ 0.46-0.78 cannot be isolated through this single crystal potentiostatic method, which supports the previously proposed explanation to be surface stabilized phase of significant thermal hysteresis and aging character.