Water or Anion? Uncovering the Zn2+ Solvation Environment in Mixed Zn(TFSI)2 and LiTFSI Water-in-Salt Electrolytes,ACS Energy Letters

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Water or Anion? Uncovering the Zn2+ Solvation Environment in Mixed Zn(TFSI)2 and LiTFSI Water-in-Salt Electrolytes
ACS Energy Letters ( IF 19.3 ) Pub Date : 2021-09-08 , DOI: 10.1021/acsenergylett.1c01624
Yong Zhang _{1,

2} , Gang Wan _{2,

3} , Nicholas H. C. Lewis _{2,

4} , Julian Mars _{2,

5} , Sharon E. Bone ₃ , Hans-Georg Steinrück ₆ , Maria R. Lukatskaya ₇ , Nicholas J. Weadock ₅ , Michal Bajdich ₈ , Oleg Borodin _{2,

9} , Andrei Tokmakoff _{2,

4} , Michael F. Toney _{2,

5} , Edward J. Maginn _{1,

2}

Affiliation

Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
Department of Chemistry, Paderborn University, Paderborn 33098, Germany
Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland
SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
Electrochemistry Branch, Senior and Electron Devices Directorate, Power and Energy Division, U.S. Army Research Laboratory, Adelphi, Maryland 20783, United States

Applications of aqueous zinc batteries for grid-scale energy storage are limited by their poor reversibility and the competing water splitting reaction. The recent invention of a water-in-salt (WIS) electrolyte concept provides a new route enabling a stable and highly reversible aqueous zinc battery chemistry. In the present work, a mixed zinc bis(trifluoromethane sulfonyl)imide (Zn(TFSI)₂) and LiTFSI WIS electrolyte was studied using X-ray total scattering, X-ray absorption, and Fourier transform infrared spectroscopy in conjunction with classical molecular dynamics simulations. It was found that, in the highly concentrated WIS electrolyte consisting of 1 m Zn(TFSI)₂ and 20 m LiTFSI, Zn²⁺ cations are mainly solvated by six waters in their first solvation shell, while the TFSI^– anions are completely excluded. This ion solvation picture is fundamentally different from the previous understandings. The results suggest that additional studies are needed to fully understand the unusual stability and reversibility of zinc-WIS electrolyte-based batteries.

中文翻译：

水还是阴离子？揭示混合 Zn(TFSI)2 和 LiTFSI 盐包水电解质中的 Zn2+ 溶剂化环境

水性锌电池在电网规模储能方面的应用受到其较差的可逆性和竞争性水分解反应的限制。最近发明的盐包水 (WIS) 电解质概念提供了一条新途径，可实现稳定且高度可逆的水性锌电池化学。在目前的工作中，使用 X 射线全散射、X 射线吸收和傅里叶变换红外光谱结合经典分子动力学研究了混合锌双（三氟甲烷磺酰基）亚胺（Zn(TFSI) ₂）和 LiTFSI WIS 电解质模拟。结果表明，在由 1 m Zn(TFSI) ₂和 20 m LiTFSI组成的高浓度 WIS 电解质中，Zn ²⁺阳离子主要在其第一个溶剂化壳中被六种水溶剂化，而 TFSI ^–阴离子则完全被排除在外。这种离子溶剂化图片与之前的理解有着根本的不同。结果表明，需要更多的研究来充分了解锌-WIS 电解质电池的异常稳定性和可逆性。

更新日期：2021-10-08

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