Molecular Design of Competitive Solvation Electrolytes for Practical High-Energy and Long-Cycling Lithium-Metal Batteries

Electrolytes with high stability against both Li anode and high-voltage cathode are critical for high-energy and long-cycling lithium metal batteries (LMBs). However, the free active solvents in common electrolytes are susceptible to decomposition at both Li anode and high-voltage cathode. Although recently developed locally high-concentration electrolytes (LHCEs) have largely restricted active solvents via Li⁺ coordination, the free molecules are still released upon the desolvation of Li⁺ at the surface of electrodes, causing continuous decomposition during long-cycling processes. Here, a molecule competitive solvation electrolyte (MCE) is shown to stabilize high-voltage LMBs by introducing a well-designed and newly synthetic bipolar solvent molecule with one ion-dissociative polar head and the other highly fluorinated nonpolar tail. The bipolar molecules competitively dissociate Li⁺ via weak coordination interactions, drastically reducing the ratio of active solvents in electrolytes and the detrimental decomposition at electrodes during the desolvation processes. Consequently, the MCE enables a 1.4-Ah Li metal pouch cell with a stack energy density of 450 Wh kg⁻¹ along with exceptional operation stability over 400 cycles (retention: 81%). Furthermore, the MCE also maintains the stable operation of a 2.5-Ah Li-S pouch cell with an excellent energy density of 417 Wh kg⁻¹ for 70 cycles under practical conditions.