Sparingly Solvating Electrolyte with Hofmeister Selectivity for Practical Long-Lived Li-Se Batteries

The excessive solvation of lithium polyselenides (LiPSe), which are highly nucleophilic, in organic electrolytes is one of the most critical challenges hindering the practical applications of lithium‒selenium (Li‒Se) batteries. Conventional electrolytes fail to simultaneously ensure the chemical stability with LiPSe, suppress its dissolution, and maintain compatibility with the lithium-metal anode. To address the above challenges, we report a rationally designed sulfonamide-based electrolyte with sparingly solvating characteristics, utilizing lithium bis(pentafluoroethylsulfonyl)- imide (LiBETI) as the lithium salt. An anion-specific effect analogous to the classical Hofmeister series was identified, in which bulkier and more chaotropic anions suppress the solvation and dissolution of LiPSe. Leveraging this principle, the LiBETI‒sulfonamide electrolyte enables stable cycling of selenium cathodes, delivering a high capacity of ‌∼656.7 mAh g^-1 and an average Coulombic efficiency of ∼99.5%‌ over 200 cycles, along with facilitated kinetics and rate performance. In contrast to conventional carbonate- and ether-based electrolytes, the sulfonamide-based electrolyte not only effectively suppresses LiPSe dissolution but also supports highly reversible Li-metal anodes. Benefiting both electrodes, our sulfonamide-based electrolyte enables Li‒Se batteries with high cathode loading (6.9 mg cm^-2 and lean electrolyte (∼2.9 µL mg^-1), retaining 89.9% of its initial capacity after 100 cycles. The work highlights the importance of electrolyte design-particularly anion-specific effect in achieving long-lived practical Li-Se batteries.