Valence evaluation of LiMnO2 and related battery materials by x-ray absorption spectroscopy

TL;DR

This study uses x-ray absorption spectroscopy to analyze the oxidation states of transition metals in LiMnO2 and related cathode materials, revealing effects of element substitution on lithium content and valence states.

Contribution

It provides detailed insights into the valence states and lithium deficiencies in LiMnO2 with different elemental substitutions, informing battery material optimization.

Findings

Mn3+ in LiMnO2 is a mixture of high-spin and low-spin states

Li deficiencies occur with Cr substitution but not with Ni substitution

Charge-transfer-type Ni or Cu substitution is effective for battery performance

Abstract

We present an x-ray absorption study of the oxidation states of transition-metal-ions of LiMnO2 and its related materials, widely used as cathodes in Li-ion batteries. The comparison between the obtained spectrum and the configuration-interaction cluster-model calculations showed that the Mn3+ in LiMnO2 is a mixture of the high-spin and low-spin states. We found that Li deficiencies occur in the case of Cr substitution, whereas there are no Li deficiencies in the case of Ni substitution. We conclude that the substitution of charge-transfer-type Ni or Cu is effective for LiMnO2 battery materials.