Electrochemical lithium intercalation in nanosized manganese oxides

TL;DR

This study investigates nanosized manganese oxides' ability to intercalate lithium electrochemically, revealing their nanostructure, redox behavior, and improved performance with cobalt doping, relevant for battery applications.

Contribution

It demonstrates lithium intercalation in nanostructured manganese oxides, characterizes their local structure during cycling, and shows cobalt doping enhances electrochemical performance.

Findings

Capacities up to 200 mAh/g at first cycle

Cobalt doping improves performance

Two-phase transformation in MnOx-C during discharge

Abstract

X-ray amorphous manganese oxides were prepared by reduction of sodium permanganate by lithium iodide in aqueous medium (MnOx-I) and by decomposition of manganese carbonate at moderate temperature (MnOx-C). TEM showed that these materials are not amorphous, but nanostructured, with a prominent spinel substructure in MnOx-C. These materials intercalate lithium with capacities up to 200 mAh/g at first cycle (potential window 1.8-4.3 V) and 175 mAh/g at 100th cycle. Best performances for MnOx-C are obtained with cobalt doping. Potential electrochemical spectroscopy shows that the initial discharge induces a 2-phase transformation in MnOx-C phases, but not in MnOx-I ones. EXAFS and XANES confirm the participation of manganese in the redox process, with variations in local structure much smaller than in known long-range crystallized manganese oxides. X-ray absorption spectroscopy also shows that cobalt in MnOx-C is divalent and does not participate in the electrochemical reaction.