School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50 UNIST-gil, Ulsan 44919, South Korea.
Battery Research Center, Korea Electrotechnology Research Institute , Changwon 642-120, South Korea.
ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3723-3732. doi: 10.1021/acsami.6b14878. Epub 2017 Jan 19.
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) 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 NaFe(PO)(PO) and Na(FeMn)O cathodes charged to high voltages (>4.2 V versus Na/Na), resulting in outstanding cycling stability (high reversible capacity of 109 mAh g over 300 cycles for the Na/NaFe(PO)(PO) cell) compared with the conventional dilute electrolyte, 1 M NaPF in ethylene carbonate/propylene carbonate (5/5, v/v).
我们提出了一种由 5 M 双（氟磺酰基）亚胺钠盐和 1,2-二甲氧基乙烷组成的超高浓度电解质，用于与高压阴极配合的钠金属阳极。使用这种电解质，在钠/不锈钢（SS）电池中，钠电镀/剥离的库仑效率在第 120 次循环时高达 99.3%，对钠金属的腐蚀性大大降低，氧化稳定性高（相对于钠/钠超过 4.9 V），且铝阴极集流器不会腐蚀。重要的是，这种超高浓度电解质可显著提高钠/SS 电池的倍率性能，并在不增加极化的情况下改善钠/对称电池的循环性能。此外，这种超高浓度电解质与高压 NaFe(PO)(PO)和 Na(FeMn)O 阴极具有良好的相容性，这些阴极可充电至高电压（相对于钠/钠超过 4.2 V），与传统稀电解质相比，具有出色的循环稳定性（对于钠/NaFe(PO)(PO)电池，300 次循环后具有 109 mAh g 的高可逆容量），1 M NaPF 在碳酸乙烯酯/碳酸丙烯酯（5/5，v/v）中。
