“Water‐in‐Salt” Electrolyte Makes Aqueous Sodium‐Ion Battery Safe, Green, and Long‐Lasting

Journal Article · Fri Jul 21 00:00:00 EDT 2017 · Advanced Energy Materials

DOI:https://doi.org/10.1002/aenm.201701189· OSTI ID:1401814

Suo, Liumin ^[1]; Borodin, Oleg ^[2]; Wang, Yuesheng ^[3]; Rong, Xiaohui ^[3]; Sun, Wei ^[1]; Fan, Xiiulin ^[1]; Xu, Shuyin ^[3]; Schroeder, Marshall A. ^[2]; Cresce, Arthur V. ^[2]; Wang, Fei ^[1]; Yang, Chongyin ^[1]; Hu, Yong‐Sheng ^[3]; Xu, Kang ^[2]; Wang, Chunsheng ^[1]

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1. Department of Chemical and Biomolecular Engineering University of Maryland College Park MD 20740 USA
2. Electrochemistry Branch, Sensor and Electron Devices Directorate Power and Energy Division U.S. Army Research Laboratory Adelphi MD 20783 USA
3. Key Laboratory for Renewable Energy Beijing Key Laboratory for New Energy Materials and Devices Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China

Abstract Narrow electrochemical stability window (1.23 V) of aqueous electrolytes is always considered the key obstacle preventing aqueous sodium‐ion chemistry of practical energy density and cycle life. The sodium‐ion water‐in‐salt electrolyte (NaWiSE) eliminates this barrier by offering a 2.5 V window through suppressing hydrogen evolution on anode with the formation of a Na ⁺ ‐conducting solid‐electrolyte interphase (SEI) and reducing the overall electrochemical activity of water on cathode. A full aqueous Na‐ion battery constructed on Na _0.66 [Mn _0.66 Ti _0.34 ]O ₂ as cathode and NaTi ₂ (PO ₄ ) ₃ as anode exhibits superior performance at both low and high rates, as exemplified by extraordinarily high Coulombic efficiency (>99.2%) at a low rate (0.2 C) for >350 cycles, and excellent cycling stability with negligible capacity losses (0.006% per cycle) at a high rate (1 C) for >1200 cycles. Molecular modeling reveals some key differences between Li‐ion and Na‐ion WiSE, and identifies a more pronounced ion aggregation with frequent contacts between the sodium cation and fluorine of anion in the latter as one main factor responsible for the formation of a dense SEI at lower salt concentration than its Li cousin.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DEAR0000389
• OSTI ID: 1401814
• Journal Information: Advanced Energy Materials, Journal Name: Advanced Energy Materials Vol. 7 Journal Issue: 21; ISSN 1614-6832
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: Germany
• Language: English