Achieving Fast and Reversible Sulfur Redox by Proper Interaction of Electrolyte in Potassium Batteries

Abstract

Potassium−sulfur batteries have potential for low-cost and high-energy density energy storage. However, it is a challenge to find suitable electrolytes affording liquid environment for intermediate sulfur species to convert at high voltages. In this study, a series of ether/potassium salt systems were systematically studied to investigate the electrochemical stability and function of the electrolytes in sulfur electrochemistry by using in situ ultraviolet−visible and Fouriertransform infrared spectroscopies. Interactions of soluble polysulfides with the electrolyte were critical to the electrochemical performance. Under optimized conditions, the bis-(trifluoromethanesulfonyl)imide anion demonstrated moderate interaction and reversible solvation/desolvation of polysulfides. Polar carboxyl groups in poly(acrylic acid) were effective for binding polysulfide in electrodes, enabling reversible sulfur conversions at high working voltages and improved initial Coulombic efficiency. This enhanced battery performance was achieved even using a conventional carbon host with a high sulfur loading of ∼69 wt %, i.e., ∼49 wt % in the cathode.

Probing the effect of ethylene carbonate on optimizing the halogen-free electrolyte performance for Mg sulfur batteries

“…However, the cell with modified electrolyte (HFE_X 4 ) possessed clear semicircles before discharge and open semicircle after discharge and significantly lower resistances before discharge and higher resistance after discharge compared with the cell with the pristine electrolyte which confirms that the modified electrolyte decomposed to a resistive SEI. 20,21 Fig. 3d shows the plating/stripping voltage profiles of symmetrical Mg/Mg cells using the HFE and HFE_X 4 at 0.2 mA cm −2 .…”

Optimizing potassium polysulfides for high performance potassium-sulfur batteries

“…As shown in Fig. 3e and Supplementary Table 3, KSBs employing SPAN cathodes [15][16][17] , small-molecular sulfur cathodes 8,9,50 , polysulfide catholyte 51 and cyclo-S 8 cathodes 18,26,27,[52][53][54] are all included for comprehensive comparison. Remarkably, W SA -W 2 C@NC/S cathode reaches the highest sulfur utilization and best rate performance.…”

Electropolymerisation Technologies for Next-Generation Lithium–Sulphur Batteries

“…In LiSBs, ethers, including DOL and DME, are considered suitable solvents owing to their compatibility with LPSs [56][57][58]. Binary mixtures of electrolyte (1 M LiTFSI in DME/DOL, 1/1, v/v) are typically utilised to achieve LiSBs of low viscosity, high ionic conductivity, and favourable electrochemical performance [54,56].…”

“…In LiSBs, ethers, including DOL and DME, are considered suitable solvents owing to their compatibility with LPSs [56][57][58]. Binary mixtures of electrolyte (1 M LiTFSI in DME/DOL, 1/1, v/v) are typically utilised to achieve LiSBs of low viscosity, high ionic conductivity, and favourable electrochemical performance [54,56]. However, LPS shuttles remain during battery cycling because of the high solubility of highly ordered Li 2 S x (x ≥ 4), resulting from the Lewis basicity of the oxygen lone pair electrons of ethers and the Lewis acidity of the Li atoms of Li 2 S x [56].…”

“…Binary mixtures of electrolyte (1 M LiTFSI in DME/DOL, 1/1, v/v) are typically utilised to achieve LiSBs of low viscosity, high ionic conductivity, and favourable electrochemical performance [54,56]. However, LPS shuttles remain during battery cycling because of the high solubility of highly ordered Li 2 S x (x ≥ 4), resulting from the Lewis basicity of the oxygen lone pair electrons of ethers and the Lewis acidity of the Li atoms of Li 2 S x [56]. Therefore, a few methods have been proposed to control LPSs in electrolytes, such as the development of new Li salts and new mixtures of electrolyte solvents, the use of organic/inorganic additives, and the design of solid/quasi-solid-state electrolytes [57,[59][60][61].…”