Evaluation of Glyoxal-Based Electrolytes for Lithium-Sulfur Batteries

Abstract

Lithium-sulfur batteries (LSBs) are among the most promising next generation battery technologies. First prototype cells show higher specific energies than conventional Li-ion batteries (LIBs) and the active material is cost-effective and ubiquitously abundant. However, Li-S batteries still suffer from several limitations, mainly the cycle life, inflation of cells, and also the lack of a component production value chain. As this battery system is based on a complex conversion mechanism, the electrolyte plays a key role, not only for specific energy, but also for rate capability, cycle stability and costs. Herein, we report on electrolytes based on glyoxylic-acetal based solvents, Tetraethoxyglyoxal (TEG) and Tetramethoxyglyoxal (TMG). These solvents have been examined before for supercapacitors and LIBs, but never for LSBs, although they exhibit some beneficial properties, and the production value chain has already been well established as they are precursors for several chemicals. A specially adapted electrolyte composition is established by adjusting solvent ratio and LiTFSI concentration in a TXG:DOL solvent blend. The obtained electrolytes show long cycle life as well as high coulombic efficiencies without the use of LiNO3, a component leading normally to cell inflation and safety issues. In addition, a successful evaluation in a multilayer Li-S-pouch cell was performed. The electrolytes were thoroughly characterized, and their sulfur conversion mechanism is discussed.

Keywords

• lithium-sulfur
• electrolyte
• glyoxal
• polysulfide solubility
• pouch cell