Delithiation Mechanisms in Acid of Spinel LiMn 2-x M x O 4 (M = Cr, Fe, Co, and Ni) Cathodes

Abstract

© The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. The products formed by the chemical extraction of lithium from LiMn 2-x M x O 4 (M = Cr, Fe, Co, and Ni) with aqueous sulfuric acid have been structurally and chemically characterized. The amount of lithium extracted is found to be proportional to the initial Mn 3+ content, confirming the reaction mechanism, LiMn 3+ Mn 4+ O4 → 0.75 Mn 2 O 4 + 0.5 Li 2 O + 0.5 MnO. Thus, no lithium is extracted from LiMn 1.5 4+ Ni 0.5 2+ O4 as there is no Mn 3+ , while complete delithiation occurs in LiMn 3+ Mn 4+ O4 to give Mn 2 O 4 . The amount of lithium extracted from the other samples is in good agreement with that calculated from the Mn 3+ content. The XRD data confirm the maintenance of the spinel structure for the delithiated samples, while the redox titration confirmed the maintenance of oxygen content at 4.0, indicating that no protons were inserted into the lattice during delithiation. The findings could provide more insight on the problem of metal dissolution from cathode materials in lithium-ion batteries.