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Issue 9, 2020
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“Water-in-salt” polymer electrolyte for Li-ion batteries

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Recent success in extending the electrochemical stability window of aqueous electrolytes to 3.0 V by using 21 mol kg-1 “water-in-salt” (WiS) has raised a high expectation for developing safe aqueous Li-ion batteries. However, the most compatible Li4Ti5O12 anodes still cannot use WiS electrolyte due to the cathodic limit (1.9 V vs. Li/Li+). Herein, a UV-curable hydrophilic polymer is introduced to further extend the cathodic limit of WiS electrolytes and replace the separator. In addition, a localized strongly basic solid polymer electrolyte (SPE) layer is coated on the anode to promote the formation of an LiF-rich SEI. The synthetic impacts of UV-crosslinking and local alkaline SPE on the anodes extend the electrochemical stability window of the solid-state aqueous polymer electrolyte to ∼3.86 V even at a reduced salt concentration of 12 mol kg−1. It enables a separator-free LiMn2O4//Li4Ti5O12 aqueous full cell with a practical capacity ratio (P/N = 1.14) of the cathode and anode to deliver a steady energy density of 151 W h kg−1 at 0.5C with an initial Coulombic efficiency of 90.50% and cycled for over 600 cycles with an average Coulombic efficiency of 99.97%, which has never been reported before for an aqueous LiMn2O4//Li4Ti5O12 full cell. This flexible and long-duration aqueous Li-ion battery with hydrogel WiSE can be widely used as a power source in wearable devices and electrical transportations where both energy density and battery safety are of high priority. An ultra-thick LTO electrode with UV-curable polymer electrolyte as the binder is demonstrated as a solid state battery electrode. And a high-voltage (7.4 V) solid-state bipolar cell is assembled with a solid-state UV-curable polymer as the electrolyte.

Graphical abstract: “Water-in-salt” polymer electrolyte for Li-ion batteries

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Article information

13 May 2020
30 Jul 2020
First published
30 Jul 2020

Energy Environ. Sci., 2020,13, 2878-2887
Article type

“Water-in-salt” polymer electrolyte for Li-ion batteries

J. Zhang, C. Cui, P. Wang, Q. Li, L. Chen, F. Han, T. Jin, S. Liu, H. Choudhary, S. R. Raghavan, N. Eidson, A. von Cresce, L. Ma, J. Uddin, D. Addison, C. Yang and C. Wang, Energy Environ. Sci., 2020, 13, 2878
DOI: 10.1039/D0EE01510E

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