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

Jaegi Lee; Yongwon Lee; Jeongmin Lee; Sang-Min Lee; Jeong-Hee Choi; Hyungsub Kim; Mi-Sook Kwon; Kisuk Kang; Kyu Tae Lee; Nam-Soon Choi

doi:10.1021/acsami.6b14878

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

ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3723-3732. doi: 10.1021/acsami.6b14878. Epub 2017 Jan 19.

Authors

Affiliations

¹ School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50 UNIST-gil, Ulsan 44919, South Korea.
² Battery Research Center, Korea Electrotechnology Research Institute , Changwon 642-120, South Korea.
³ Department of Materials Science and Engineering, Seoul National University , Seoul 151-742, South Korea.
⁴ Department of Chemical and Biological Engineering, Seoul National University , Seoul 151-742, South Korea.

PMID: 28067499
DOI: 10.1021/acsami.6b14878

Abstract

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 Na₄Fe₃(PO₄)₂(P₂O₇) and Na_0.7(Fe_0.5Mn_0.5)O₂ cathodes charged to high voltages (>4.2 V versus Na/Na⁺), resulting in outstanding cycling stability (high reversible capacity of 109 mAh g^-1 over 300 cycles for the Na/Na₄Fe₃(PO₄)₂(P₂O₇) cell) compared with the conventional dilute electrolyte, 1 M NaPF₆ in ethylene carbonate/propylene carbonate (5/5, v/v).

Keywords: high-voltage cathodes; interfaces; liquid electrolytes; sodium bis(fluorosulfonyl)imide; sodium metal batteries.