A novel mixed ether-based electrolyte for lithium–sulfur batteries with Li anode protection by dual salts

Lithium–sulfur batteries (LSB) are regarded as one of the next-generation energy storage systems with a high energy density. However, the shuttle effect of lithium polysulfides (LiPSs) and irreversible consumption of the Li anode prevent the practical application of Li–S batteries. In this work, a mixed tetrahydrofuran (THF) and dipropyl ether (DPE) based electrolyte has been optimized for Li–S batteries. Due to the common-ion effect, the LiPS solubility has been significantly inhibited when the sulfur cathode is operating in a concentrated electrolyte containing an optimized solvent system with weak dissolving power. And no self-discharge effect occurred in the cells with these electrolytes during a 10 day storage. Besides, the coulombic efficiency (CE) for Li deposition/stripping has been improved by optimizing the ratio of dual lithium salts. Impressively, Li‖Cu half-cells can run stably for more than 500 cycles with a high CE (>99.3%). For these reasons, a Li–SeSPAN cell with a L1L2TE-1382 electrolyte demonstrates an excellent capacity retention (>94% after 500 cycles) with an ultrathin (50 μm) Li metal anode. With a good compatibility of the optimized electrolyte for both the Li metal anode and sulfur cathode, this work provides a new design strategy for the electrolyte for lithium–sulfur batteries.