Cation disorder dominates the defect chemistry of high-voltage LiMn1.5Ni0.5O4 (LMNO) spinel cathodes

Jiayi Cen; Bonan Zhu; Seán R. Kavanagh; Alexander G. Squires; David O. Scanlon

doi:10.1039/D3TA00532A

Cation disorder dominates the defect chemistry of high-voltage LiMn_1.5Ni_0.5O₄ (LMNO) spinel cathodes†

Jiayi Cen,

^ab Bonan Zhu,

^ab Seán R. Kavanagh,

^ac Alexander G. Squires

^ab and David O. Scanlon

*^ab

Author affiliations

* Corresponding authors

^a Department of Chemistry and Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, UK
E-mail: d.scanlon@ucl.ac.uk

^b The Faraday Institution, Quad One, Harwell Science and Innovation Campus, Didcot OX11 0RA, UK

^c Department of Materials and Thomas Young Centre, Imperial College London, Exhibition Road, London SW7 2AZ, UK

Abstract

High-voltage spinel LiMn_1.5Ni_0.5O₄ (LMNO) can exist in a Mn/Ni ordered P4₃32 or disordered Fd [3 with combining macron] m arrangement with a majority of literature studies reporting improved electrochemical performance for the disordered phase. Through modifying synthesis conditions, the Mn/Ni ordering can be tuned, however oxygen and Mn³⁺ stoichiometries are also affected, making it difficult to decouple these responses and optimise performance. Here, we investigate all intrinsic defects in P4₃32 LMNO under various growth conditions, using density functional theory (DFT) calculations. We find that the majority of defects are deep and associated with small polarons (Mn³⁺, Mn²⁺ and Ni³⁺) formation. The tendency for cation disorder can be explained by the low formation energy of the antisite defects and their stoichiometric complexes. The intrinsic Fermi level of LMNO varies from moderately n-type under oxygen-poor conditions to weakly p-type under oxygen-rich conditions. Our work explains experimental observations (e.g. the Mn/Ni disorder) and provides guidelines for defect-controlled synthesis.

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Article information

DOI: https://doi.org/10.1039/D3TA00532A
Article type: Paper
Submitted: 30 Jan 2023
Accepted: 12 Apr 2023
First published: 12 Apr 2023
This article is Open Access

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J. Mater. Chem. A, 2023,11, 13353-13370

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Cation disorder dominates the defect chemistry of high-voltage LiMn_1.5Ni_0.5O₄ (LMNO) spinel cathodes

J. Cen, B. Zhu, S. R. Kavanagh, A. G. Squires and D. O. Scanlon, J. Mater. Chem. A, 2023, 11, 13353 DOI: 10.1039/D3TA00532A

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