Origin of manganese activity in LiCoMnO4

Determine the relative contributions of defect-driven effects, including oxygen non-stoichiometry and cation disorder, and intrinsic electronic redistribution to the residual electrochemical activity of manganese in LiCoMnO4 spinels.

Background

LiCoMnO4 is nominally expected to contain manganese predominantly in the Mn4+ oxidation state, with charge compensation occurring mainly through the Co4+/Co3+ redox couple. However, the operando XANES data reveal a residual low-voltage manganese redox contribution. The paper attributes this behavior potentially to oxygen vacancies, cation disorder, and other defects that partially reduce Mn4+ toward Mn3+, while also noting that an intrinsic redistribution of electronic charge could produce a similar effect.

The unresolved problem is to distinguish these defect-driven mechanisms from intrinsic electronic redistribution and thereby establish the precise origin of manganese electrochemical activity in fully Co-substituted LiCoMnO4. Resolving this issue would clarify the charge-compensation mechanism and the relationship between defects, local electronic structure, and electrochemical behavior in high-voltage spinel cathodes.