Polysulfide Shuttle Suppression by Electrolytes with Low‐Density for High‐Energy Lithium–Sulfur Batteries

Abstract

A low‐density electrolyte composition is introduced for lithium–sulfur (Li–S) batteries with intrinsic and effective polysulfide shuttle suppression. Hexyl methyl ether (HME) is used in combination with 1,3‐dioxolane (DOL) as a solvent for the Li–S battery electrolyte. The choice of solvent limits the dissolution of polysulfides, leading to successful suppression of the parasitic polysulfide shuttle. Hence, high coulombic efficiencies of 98% can be obtained in coin cells for over 50 cycles. The impact of the specifically adapted electrolyte solvent is studied systematically by varying solvent combinations in order to enable the development of light innovative shuttle suppressing electrolytes. In contrast to concepts relying on hydrofluoro ether dilution, the presented electrolyte features a significantly reduced mass density at 2 m lithium bis(trifluoromethanesulfonylimide) (LiTFSI) conductive salt enabling significant weight reduction on the Li–S prototype cell level, thus, allowing energy densities up to 400 Wh kg−1.

Lithium–Sulfur Batteries under Lean Electrolyte Conditions: Challenges and Opportunities

“…[119] Selective non-solvating electrolyte demonstrates the solvating power strong enough to dissolve the supporting salt but too weak to solvate the polysulfide. [120] Fluorination of some ether solvent molecules in standard electrolyte is an effective strategy to obtain such a selective non-solvating electrolyte under a low E/S ratio of 6.5 mL mg S À1 . [121] Except for leanelectrolyte operability, a mixture of hydrofluoro ether and sulfolane also inhibited the gas-producing behavior of pouch cells benefiting from their low volatility.…”

A Micelle Electrolyte Enabled by Fluorinated Ether Additives for Polysulfide Suppression and Li Metal Stabilization in Li-S Battery

“…As a result, high-concentration electrolytes i.e., room-temperature ionic liquids, (Park et al, 2013a,b;Song et al, 2013b) solvent-in-salt, (Suo et al, 2013), and solvate ionic liquids (Dokko et al, 2013;Ueno et al, 2013;Zhang et al, 2016) have all proven quite effective at discouraging polysulfide dissolution, despite their high viscosity and subsequent poor lithium transport properties. More recently, several researchers have addressed this problem through dilution of concentrated electrolytes with poorly-coordinating solvents; work reported by Weller et al demonstrated a low-density electrolyte with high lithium salt concentration to suppress polysulfide dissolution using hexyl methyl ether in combination with DOL (Weller et al, 2019). The Wang group has recently reported good Li-S cell performance achieved from developing a "localized high concentration electrolyte" using a fluoroalkyl ether additive blended with DME electrolyte (Zheng et al, 2019).…”

Recent Progress and Emerging Application Areas for Lithium–Sulfur Battery Technology

“…[29] Within the battery research community, significant efforts have been made to improve the performance of the cell components and materials used within Li-S batteries. [25,40,[48][49][50] The selected examples are briefly summarized below.…”

“…To tackle the issue of a low volumetric energy density (in Wh L À1 ), the mass density of the electrolyte is less important than for gravimetric energy density (in Wh kg À1 ). [49] Reducing the content of electrolyte from 3 to 1.5 μL or per mg of S active material [24] will decrease the weight of the electrolyte and the free volume required for its uptake. This is of importance, as in all known Li-S cell concepts, the electrolyte may take a large fraction of the cell (>40 % of the cell weight and volume [23,52] ).…”