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High-Voltage Aqueous Na-Ion Battery Enabled by Inert-Cation-Assisted Water-in-Salt Electrolyte |
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| Authors: | Liwei Jiang Lilu Liu Jinming Yue Qiangqiang Zhang Anxing Zhou Oleg Borodin Liumin Suo Hong Li Liquan Chen Kang Xu Yong-Sheng Hu |
| Affiliation: | 1. 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, Beijing, 100190 China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049 China;2. Electrochemistry Branch, Sensor and Electron Devices Directorate, Combat Capabilities Development Command 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, Beijing, 100190 China;4. 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, Beijing, 100190 China Yangtze River Delta Physics Research Center Co. Ltd, Liyang, 213300 China |
| Abstract: | Water-in-salt (WiS) electrolytes provide a new pathway to widen the electrochemical window of aqueous electrolytes. However, their formulation strongly depends on the solubility of the chosen salts, imposing a stringent restriction on the number of possible WiS systems. This issue becomes more severe for aqueous Na-ion batteries (ANIBs) owing to the relatively lower solubility of sodium salts compared to its alkaline cousins (Li, K, and Cs). A new class of the inert-cation-assisted WiS (IC-WiS) electrolytes containing the tetraethylammonium (TEA+) inert cation is reported. The Na IC-WiS electrolyte at a superhigh concentration of 31 mol kg–1 exhibits a wide electrochemical window of 3.3 V, suppresses transition metal dissolution from the cathode, and ensures singular intercalation of Na into both cathode and anode electrodes during cycling, which is often problematic in mixed alkali cation systems such as K–Na and Li–Na. Owing to these unique advantages of the IC-WiS electrolyte, the NaTiOPO4 anode and Prussian blue analog Na1.88Mn[Fe(CN)6]0.97·1.35H2O cathode can be coupled to construct a full ANIB, delivering an average voltage of 1.74 V and a high energy density of 71 Wh kg−1 with a capacity retention of 90% after 200 cycles at 0.25C and of 76% over 800 cycles at 1C. |
| Keywords: | aqueous Na-ion batteries inert cations water-in-salt electrolytes |