Abstract
Understanding the surface reactivity of the commercial cathode material LiMn2O4 towards the electrolyte is important to improve the cycling performance of secondary lithium-ion batteries and to prevent manganese dissolution. In this work, we have employed spin-polarized density functional theory calculations with on-site Coulomb interactions and long-range dispersion corrections [DFT+U-D3-(BJ)] to investigate the adsorption of the electrolyte component ethylene carbonate (EC) onto the (001), (011) and (111) surfaces of the fully lithiated and partially delithiated Li1-xMn2O4 spinel (0.000 < x < 0.375). The surface interactions were investigated by evaluating the adsorption energies of the EC molecule and the surface free energies. Furthermore, we analyzed the impact of EC adsorption on the Wulff crystal morphologies, the molecular vibrational frequencies and the adsorbate/surface charge transfers. The adsorption energies indicate that the EC molecule strongly adsorbs on the (111) facet, which is attributed to a bidentate binding configuration. We found that EC adsorption enhances the stability of the (111) facet, as shown by the Wulff crystal morphologies. Although a negligible charge transfer was calculated between the spinel surfaces and the EC molecule, a large charge rearrangement takes place within the surfactant upon adsorption. The wavenumbers of the CO stretching mode for the interacting EC molecule are red-shifted with respect to the isolated adsorbate, suggesting that this bond becomes weaker. The surface free energies show that both the fully lithiated and partially delithiated forms of the LiMn2O4 surfaces are stabilized by the EC molecule.
| Original language | English |
|---|---|
| Pages (from-to) | 6763-6771 |
| Number of pages | 9 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 22 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 28 Mar 2020 |
Funding
D. S.-C. is grateful to the Department of Science and Technology (DST) and the National Research Foundation (NRF) of South Africa for the provision of a Postdoctoral Fellowship for Early Career Researchers from the United Kingdom. P. E. N. acknowledges the financial support of the DST-NRF South African Research Chair Initiative. We also appreciate the support received from the DST Energy Storage Research Development and Innovation Initiative. We acknowledge the Engineering & Physical Sciences Research Council (EPSRC Grant No. EP/K009567/2 and No. EP/ K016288/1), the Economic and Social Research Council (ESRC Grant ES/N013867/1) and the National Research Foundation, South Africa, for funding of a grant for UK-SA PhD exchanges under the Newton programme. This work was performed using the computational facilities of the Advanced Research Computing @ Cardiff (ARCCA) Division, Cardiff University; the Centre for High Performance Computing (CHPC) of South Africa; and the Supercomputing Facilities at Cardiff University operated by ARCCA on behalf of the HPC Wales and Supercomputing Wales (SCW) projects. We acknowledge the support of the latter, which is part-funded by the European Regional Development Fund (ERDF) via the Welsh Government. All data collected during this research are openly available from the Cardiff University’s Research Portal at http://doi.org/10.17035/d.2019.0085116020.
