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Title: Ion-Pair Dissociation on α-MoO 3 Surfaces: Focus on the Electrolyte–Cathode Compatibility Issue in Mg Batteries

Abstract

Nanosizing has been explored as one option to enhance typically sluggish Mg ion mobility in cathode materials. Here, we explore the effects of the surfaces of α-MoO3 in facilitating or hindering Mg ion desolvation at the electrolyte–cathode interface. It is well-known in the Mg battery community that Mg–anion contact ion pairs may form in the electrolyte and thus the insertion of Mg into the cathode must involve desolvation and dissociation, where Mg is detached from the counterion at the cathode surface. Here we compare two representative Mg–anion pairs, i.e., (Mg–Cl)+ and (Mg–TFSI)+ (TFSI–, bis(trifluoromethanesulfonyl)imide), differentiated according to the size and polarizability of the anion, and examine their dissociations on different α-MoO3 surfaces. We find that (Mg–Cl)+ requires a higher dissociation energy than (Mg–TFSI)+, which implies that the Mg–TFSI-type electrolyte is more suitable to be integrated with the MoO3 cathode when creating an electrochemical cell. The dissociation of (Mg–TFSI)+ occurs, however, not on the lowest energy (010) surface where the van der Waals (vdW) gap opens, but on the hydroxyl-terminated (001) surface. Therefore, to optimize the performance of α-MoO3 toward (Mg–TFSI)+ dissociation, preferential growth of the hydroxyl-terminated (001) surface is required.

Authors:
ORCiD logo [1];  [1]
  1. The Molecular Foundry and Joint Center for Energy Storage Research (JCESR), Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1483642
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 1; Journal ID: ISSN 1932-7447
Country of Publication:
United States
Language:
English

Citation Formats

Wan, Liwen F., and Prendergast, David. Ion-Pair Dissociation on α-MoO 3 Surfaces: Focus on the Electrolyte–Cathode Compatibility Issue in Mg Batteries. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.7b09124.
Wan, Liwen F., & Prendergast, David. Ion-Pair Dissociation on α-MoO 3 Surfaces: Focus on the Electrolyte–Cathode Compatibility Issue in Mg Batteries. United States. doi:10.1021/acs.jpcc.7b09124.
Wan, Liwen F., and Prendergast, David. Wed . "Ion-Pair Dissociation on α-MoO 3 Surfaces: Focus on the Electrolyte–Cathode Compatibility Issue in Mg Batteries". United States. doi:10.1021/acs.jpcc.7b09124.
@article{osti_1483642,
title = {Ion-Pair Dissociation on α-MoO 3 Surfaces: Focus on the Electrolyte–Cathode Compatibility Issue in Mg Batteries},
author = {Wan, Liwen F. and Prendergast, David},
abstractNote = {Nanosizing has been explored as one option to enhance typically sluggish Mg ion mobility in cathode materials. Here, we explore the effects of the surfaces of α-MoO3 in facilitating or hindering Mg ion desolvation at the electrolyte–cathode interface. It is well-known in the Mg battery community that Mg–anion contact ion pairs may form in the electrolyte and thus the insertion of Mg into the cathode must involve desolvation and dissociation, where Mg is detached from the counterion at the cathode surface. Here we compare two representative Mg–anion pairs, i.e., (Mg–Cl)+ and (Mg–TFSI)+ (TFSI–, bis(trifluoromethanesulfonyl)imide), differentiated according to the size and polarizability of the anion, and examine their dissociations on different α-MoO3 surfaces. We find that (Mg–Cl)+ requires a higher dissociation energy than (Mg–TFSI)+, which implies that the Mg–TFSI-type electrolyte is more suitable to be integrated with the MoO3 cathode when creating an electrochemical cell. The dissociation of (Mg–TFSI)+ occurs, however, not on the lowest energy (010) surface where the van der Waals (vdW) gap opens, but on the hydroxyl-terminated (001) surface. Therefore, to optimize the performance of α-MoO3 toward (Mg–TFSI)+ dissociation, preferential growth of the hydroxyl-terminated (001) surface is required.},
doi = {10.1021/acs.jpcc.7b09124},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 1,
volume = 122,
place = {United States},
year = {2017},
month = {12}
}