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Title: A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid

Abstract

Fundamental characterization of battery electrolyte is crucial for rechargeable batteries. This work reports the chemical stability of sodium hexafluorophosphate (NaPF6)-based non-aqueous electrolytes containing different solvent mixtures (e.g., cyclic and acyclic carbonates) in the presence of water for Na-ion batteries. A degradation study is conducted using NaPF 6-based electrolytes, highlighting the effect of two electrolyte additives, 2,2,2-trifluoroethoxy-2,2,2-ethoxy phosphazene (FM2) and fluoroethylene carbonate (FEC), on degradation and cell performance of full-cell Na-ion batteries. Hydrolysis of this salt in acidic condition is particularly prone to form hydrofluoric acid (HF), and can be observed in electrolytes made with battery grade carbonate solvents (<20 ppm of water). Here, degradation mechanisms of NaPF 6-based electrolytes are studied using liquid nuclear magnetic resonance (NMR). Noticeable degradation takes place in high purity electrolytes with the presence of moisture to form HF and organophosphates in timeframes below the current shelf-life of the Na electrolytes. FEC is not efficient to protect the electrodes from being exposed to HF. On the other hand, FM2 is revealed as a “scavenger” of HF, which helps stabilize the shelf life of electrolytes that might contain or become exposed to water. Our study underscores the importance to understanding the degradation of electrolyte and improving stabilitymore » toward better shelf life for sodium ion batteries.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Boise State Univ., ID (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE); National Science Foundation (NSF)
OSTI Identifier:
1593898
Alternate Identifier(s):
OSTI ID: 1573271
Report Number(s):
INL/JOU-19-55306-Rev000
Journal ID: ISSN 0378-7753
Grant/Contract Number:  
AC07-05ID14517
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Power Sources
Additional Journal Information:
Journal Volume: 447; Journal Issue: C; Journal ID: ISSN 0378-7753
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; Sodium-ion battery; NaPF6 salt; Electrolyte; Degradation; Mitigation of HF; HF scavenger

Citation Formats

Barnes, Pete, Smith, Kassiopeia, Parrish, Riley, Jones, Chris, Skinner, Paige, Storch, Erik, White, Quinn, Deng, Changjian, Karsann, Devan, Lau, Miu Lun, Dumais, Joseph J., Dufek, Eric J., and Xiong, Hui. A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid. United States: N. p., 2019. Web. doi:10.1016/j.jpowsour.2019.227363.
Barnes, Pete, Smith, Kassiopeia, Parrish, Riley, Jones, Chris, Skinner, Paige, Storch, Erik, White, Quinn, Deng, Changjian, Karsann, Devan, Lau, Miu Lun, Dumais, Joseph J., Dufek, Eric J., & Xiong, Hui. A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid. United States. doi:10.1016/j.jpowsour.2019.227363.
Barnes, Pete, Smith, Kassiopeia, Parrish, Riley, Jones, Chris, Skinner, Paige, Storch, Erik, White, Quinn, Deng, Changjian, Karsann, Devan, Lau, Miu Lun, Dumais, Joseph J., Dufek, Eric J., and Xiong, Hui. Wed . "A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid". United States. doi:10.1016/j.jpowsour.2019.227363.
@article{osti_1593898,
title = {A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid},
author = {Barnes, Pete and Smith, Kassiopeia and Parrish, Riley and Jones, Chris and Skinner, Paige and Storch, Erik and White, Quinn and Deng, Changjian and Karsann, Devan and Lau, Miu Lun and Dumais, Joseph J. and Dufek, Eric J. and Xiong, Hui},
abstractNote = {Fundamental characterization of battery electrolyte is crucial for rechargeable batteries. This work reports the chemical stability of sodium hexafluorophosphate (NaPF6)-based non-aqueous electrolytes containing different solvent mixtures (e.g., cyclic and acyclic carbonates) in the presence of water for Na-ion batteries. A degradation study is conducted using NaPF6-based electrolytes, highlighting the effect of two electrolyte additives, 2,2,2-trifluoroethoxy-2,2,2-ethoxy phosphazene (FM2) and fluoroethylene carbonate (FEC), on degradation and cell performance of full-cell Na-ion batteries. Hydrolysis of this salt in acidic condition is particularly prone to form hydrofluoric acid (HF), and can be observed in electrolytes made with battery grade carbonate solvents (<20 ppm of water). Here, degradation mechanisms of NaPF6-based electrolytes are studied using liquid nuclear magnetic resonance (NMR). Noticeable degradation takes place in high purity electrolytes with the presence of moisture to form HF and organophosphates in timeframes below the current shelf-life of the Na electrolytes. FEC is not efficient to protect the electrodes from being exposed to HF. On the other hand, FM2 is revealed as a “scavenger” of HF, which helps stabilize the shelf life of electrolytes that might contain or become exposed to water. Our study underscores the importance to understanding the degradation of electrolyte and improving stability toward better shelf life for sodium ion batteries.},
doi = {10.1016/j.jpowsour.2019.227363},
journal = {Journal of Power Sources},
number = C,
volume = 447,
place = {United States},
year = {2019},
month = {11}
}

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This content will become publicly available on November 6, 2020
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