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Title: Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations

Abstract

A viable Li/O 2 battery will require the development of stable electrolytes that do not continuously decompose during cell operation. In some recent experiments it is suggested that reactions occurring at the interface between the liquid electrolyte and the solid lithium peroxide (Li 2O 2) discharge phase are a major contributor to these instabilities. To clarify the mechanisms associated with these reactions, a variety of atomistic simulation techniques, classical Monte Carlo, van der Waals-augmented density functional theory, ab initio molecular dynamics, and various solvation models, are used to study the initial decomposition of the common electrolyte solvent, dimethoxyethane (DME), on surfaces of Li 2O 2. Comparisons are made between the two predominant Li 2O 2 surface charge states by calculating decomposition pathways on peroxide-terminated (O 2 2–) and superoxide-terminated (O 2 1–) facets. For both terminations, DME decomposition proceeds exothermically via a two-step process comprised of hydrogen abstraction (H-abstraction) followed by nucleophilic attack. In the first step, abstracted H dissociates a surface O 2 dimer, and combines with a dissociated oxygen to form a hydroxide ion (OH ). In the remaining surface oxygen then attacks the DME, resulting in a DME fragment that is strongly bound to the Li 2Omore » 2 surface. DME decomposition is predicted to be more exothermic on the peroxide facet; nevertheless, the rate of DME decomposition is faster on the superoxide termination. The impact of solvation (explicit vs implicit) and an applied electric field on the reaction energetics are investigated. Finally, our calculations suggest that surface-mediated electrolyte decomposition should out-pace liquid-phase processes such as solvent auto-oxidation by dissolved O 2.« less

Authors:
 [1];  [2];  [3];  [3];  [4]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering
  2. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Physics
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering and Applied Physics Program
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1325870
Report Number(s):
LLNL-JRNL-666496
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 119; Journal Issue: 17; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 25 ENERGY STORAGE

Citation Formats

Kumar, Nitin, Radin, Maxwell D., Wood, Brandon C., Ogitsu, Tadashi, and Siegel, Donald J. Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations. United States: N. p., 2015. Web. doi:10.1021/acs.jpcc.5b00256.
Kumar, Nitin, Radin, Maxwell D., Wood, Brandon C., Ogitsu, Tadashi, & Siegel, Donald J. Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations. United States. doi:10.1021/acs.jpcc.5b00256.
Kumar, Nitin, Radin, Maxwell D., Wood, Brandon C., Ogitsu, Tadashi, and Siegel, Donald J. Mon . "Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations". United States. doi:10.1021/acs.jpcc.5b00256. https://www.osti.gov/servlets/purl/1325870.
@article{osti_1325870,
title = {Surface-Mediated Solvent Decomposition in Li–Air Batteries: Impact of Peroxide and Superoxide Surface Terminations},
author = {Kumar, Nitin and Radin, Maxwell D. and Wood, Brandon C. and Ogitsu, Tadashi and Siegel, Donald J.},
abstractNote = {A viable Li/O2 battery will require the development of stable electrolytes that do not continuously decompose during cell operation. In some recent experiments it is suggested that reactions occurring at the interface between the liquid electrolyte and the solid lithium peroxide (Li2O2) discharge phase are a major contributor to these instabilities. To clarify the mechanisms associated with these reactions, a variety of atomistic simulation techniques, classical Monte Carlo, van der Waals-augmented density functional theory, ab initio molecular dynamics, and various solvation models, are used to study the initial decomposition of the common electrolyte solvent, dimethoxyethane (DME), on surfaces of Li2O2. Comparisons are made between the two predominant Li2O2 surface charge states by calculating decomposition pathways on peroxide-terminated (O22–) and superoxide-terminated (O21–) facets. For both terminations, DME decomposition proceeds exothermically via a two-step process comprised of hydrogen abstraction (H-abstraction) followed by nucleophilic attack. In the first step, abstracted H dissociates a surface O2 dimer, and combines with a dissociated oxygen to form a hydroxide ion (OH–). In the remaining surface oxygen then attacks the DME, resulting in a DME fragment that is strongly bound to the Li2O2 surface. DME decomposition is predicted to be more exothermic on the peroxide facet; nevertheless, the rate of DME decomposition is faster on the superoxide termination. The impact of solvation (explicit vs implicit) and an applied electric field on the reaction energetics are investigated. Finally, our calculations suggest that surface-mediated electrolyte decomposition should out-pace liquid-phase processes such as solvent auto-oxidation by dissolved O2.},
doi = {10.1021/acs.jpcc.5b00256},
journal = {Journal of Physical Chemistry. C},
number = 17,
volume = 119,
place = {United States},
year = {Mon Apr 13 00:00:00 EDT 2015},
month = {Mon Apr 13 00:00:00 EDT 2015}
}

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Cited by: 17works
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  • Superoxide reacts with carbonate solvents in Li–air batteries. Tris(pentafluorophenyl)borane is found to catalyze a more rapid superoxide (O 2 -) disproportionation reaction than the reaction between superoxide and propylene carbonate (PC). With this catalysis, the negative impact of the reaction between the electrolyte and O 2 -produced by the O 2 reduction can be minimized. A simple kinetic study using ESR spectroscopy was reported to determine reaction orders and rate constants for the reaction between PC and superoxide, and the disproportionation of superoxide catalyzed by Tris(pentafluorophenyl)borane and Li ions. As a result, the reactions are found to be first ordermore » and the rate constants are 0.033 s -1 M -1, 0.020 s -1 M -1and 0.67 s -1M -1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively.« less
  • In sodium–oxygen (Na–O2) batteries, multiple discharge products have been observed by different research groups. Given the fact that different materials, gas supplies, and cell configurations are used by different groups, it is a great challenge to draw a clear conclusion on the formation of the different products. Here, two different cell setups are used to investigate the cell chemistries of Na–O2 batteries. With the same materials and gas supplies, a peroxide-based product is observed in a glass chamber cell and a superoxide-based product is observed in a stainless-steel cell. Ex situ high-energy X-ray diffraction (HEXRD) and Raman spectroscopy are performedmore » to investigate the structure and composition of the product. In addition, in situ XRD is used to investigate the structure evolution of the peroxide-based product. The findings highlight the importance of the cell design and emphasize the critical environment of the formation of the discharge products of Na–O2 batteries.« less
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  • Derivatives of 1,4-naphthoquinone, 2-chloro-3-((2-(dimethylpropylammonio)ethyl)amino)-1,4-naphthoquinone bromide, Ia, and 2-chloro-3-((2-(dimethyl(3-(trimethoxysilyl)propyl)ammonio)ethyl)amino)-1,4-naphthoquinone bromide, Ib, have been synthesized and used as solution and surface-bound catalysts, respectively, for the electrochemical and photoelectrochemical reduction of O/sub 2/ to H/sub 2/O/sub 2/. The surface derivatizing reagent Ib having the -Si(OCH/sub 3/)/sub 3/ functionality can be used to functionalize a variety of surfaces including electrode materials and high surface area oxides. The surface reagent, (Q/QH/sub 2/)/sub surf/, has the same E/sup 0/' as Ia in solution, approx. -0.4 V vs. SCE at pH 7. The (QH/sub 2/)/sub surf/ reacts with O/sub 2/ in aqueous electrolyte at pH 7 withmore » a rate constant > 10/sup 5/ M/sup -1/s/sup -1/ to form H/sub 2/O/sub 2/ and (Q)/sub surf/. High surface area oxides functionalized with Ib yield (M/sub x/O/sub y/)-(Q) that can be electrochemically reduced to (M/sub x/O/sub y/)-(QH/sub 2/) via mediation by a low concentration of Ia in solution. The (M/sub x/O/sub y/)-(QH/sub 2/) can be isolated from the electrolyte solution by filtration and reacted with O/sub 2//H/sub 2/O to yield up to 0.1 M H/sub 2/O/sub 2/ in H/sub 2/O free of electrolyte. Study of the reduction of Ia at rotating-W-disk electrodes derivatized with Ib shows that the redox equilibration of the solution quinone and surface quinone is rapid. Reduction of (Q)/sub surf/ or Ia at visible light illuminated p-WS/sub 2/ can be effected at an electrode potential approx. 0.8 V more positive than at a metallic electode. The overall energetics are such that light can be used to effect the uphill formation of H/sub 2/O/sub 2/ via the quinone-mediated reduction of O/sub 2/. The onset of O/sub 2/ reduction is up to 0.6 V more positive than E/sup 0/'(O/sub 2//H/sub 2/O/sub 2/). The sustained photoassisted reduction of O/sub 2/ to H/sub 2/O/sub 2/ has been demonstrated. 15 references, 8 figures, 2 tables.« less