Ultraconcentrated Sodium Bis(fluorosulfonyl)imide-Based Electrolytes for High-Performance Sodium Metal Batteries

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• 作者：Jaegi Lee ; Yongwon Lee ; Jeongmin Lee ; Sang-Min Lee ; Jeong-Hee Choi ; Hyungsub Kim ; Mi-Sook Kwon ; Kisuk KangKyu Tae Lee ; Nam-Soon Choi
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：February 1, 2017
• 年：2017
• 卷：9
• 期：4
• 页码：3723-3732
• 全文大小：651K
• ISSN：1944-8252

文摘

We present an ultraconcentrated electrolyte composed of 5 M sodium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane for Na metal anodes coupled with high-voltage cathodes. Using this electrolyte, a very high Coulombic efficiency of 99.3% at the 120th cycle for Na plating/stripping is obtained in Na/stainless steel (SS) cells with highly reduced corrosivity toward Na metal and high oxidation durability (over 4.9 V versus Na/Na<sup>+sup>) without corrosion of the aluminum cathode current collector. Importantly, the use of this ultraconcentrated electrolyte results in substantially improved rate capability in Na/SS cells and excellent cycling performance in Na/Na symmetric cells without the increase of polarization. Moreover, this ultraconcentrated electrolyte exhibits good compatibility with high-voltage Na<sub>4sub>Fe<sub>3sub>(PO<sub>4sub>)<sub>2sub>(P<sub>2sub>O<sub>7sub>) and Na<sub>0.7sub>(Fe<sub>0.5sub>Mn<sub>0.5sub>)O<sub>2sub> cathodes charged to high voltages (>4.2 V versus Na/Na<sup>+sup>), resulting in outstanding cycling stability (high reversible capacity of 109 mAh g<sup>–1sup> over 300 cycles for the Na/Na<sub>4sub>Fe<sub>3sub>(PO<sub>4sub>)<sub>2sub>(P<sub>2sub>O<sub>7sub>) cell) compared with the conventional dilute electrolyte, 1 M NaPF<sub>6sub> in ethylene carbonate/propylene carbonate (5/5, v/v).