Impact of Carbon Porosity on Sulfur Conversion in Li−S Battery Cathodes in a Sparingly Polysulfide Solvating Electrolyte

Abstract

Advancing the development of lithium‐sulfur (Li−S) technology is advantageous for next generation secondary batteries to improve gravimetric and volumetric energy of established energy storage devices. In this regard, a sparingly PS solvating electrolyte based on sulfolane and hydrofluoroether is known as a promising concept to enhance the volumetric energy density by increasing the cycling stability. So far, little is known about the impact of the carbon porosity on the electrochemical sulfur utilization. Herein, carbon materials with varying pore diameter and architecture (micropores, mesopores and hierarchical pores) are studied as scaffold for Li−S cathodes using TMS/TTE electrolyte to obtain more insights into the relationship between the carbon scaffold porosity and the modified conversion mechanism of sparingly solvating electrolytes. The electrochemical evaluation under lean conditions (5 μl mgS−1) revealed stable cycling performance for all Li−S cathodes. Using microporous electrodes, a reversible quasi‐solid‐state conversion is detected by an additional third discharge plateau being confirmed by cyclovoltammetry. GITT experiments give evidence that the carbon porosity impacts the reaction kinetics of the polysulfide conversion by using TMS/TTE electrolyte. Based on these findings, new mechanistic insights into the operation of Li−S batteries are provided by using sparingly solvating electrolytes.

Perspective of polymer-based solid-state Li-S batteries

“…Consequently, Cuisinier et al [100] , Lee et al [101] , Shyamsunder et al [102] proposed new different concepts of "sparingly solvating electrolytes", which consists of a low donor number solvent as a co-solvent or as a solo solvent when a low ion-pairing Li salt is used. Following this concept, other research groups, such as Nakanishi et al in Japan and Piwko et al in Germany, also actively contributed to this regard [103][104][105][106][107] . It is noteworthy that with the change from electrolytes with high PS solubility to such "sparingly solvating electrolytes", the whole cell chemistry is changed simultaneously.…”

Sulfur‐containing polymer cathode materials: From energy storage mechanism to energy density

“…In order to decrease the ohmic polarization, we can inhibit the formation of high-order polysulfides by employing sulfur-containing polymers as cathode materials. Besides, synthesizing multi-porous carbon as host materials [64][65][66] is also an effective way to ensure adequate contact area between active materials and electrolyte. Furthermore, the internal lithium ion transport path must be large enough for the fast charge transportation.…”

2D Graphitic Carbon Nitride for Energy Conversion and Storage

“…LSBs with elemental sulfur as the positive electrode store energy through the electrochemical reaction between lithium anode and elemental sulfur. [211][212][213] The theoretical energy density is calculated as 2600 Wh kg −1 based on the complete reaction between lithium and sulfur converted to lithium sulfide. In addition, the abundance, easy availability, and low Adapted with permission.…”