Water/Ionic Liquid/Succinonitrile Hybrid Electrolytes for Aqueous Batteries

The water-in-salt concept has significantly improved the electrochemical stability of aqueous electrolytes, and hybridization with organic solvents or ionic liquids further enhanced their reductive stability, enabling cell chemistries up to 150 Wh kg−1 active material. Here, a large design space is opened by introducing succinonitrile as cosolvent in water/ionic liquid/succinonitrile hybrid electrolytes (WISHEs). By means addition, solubility limits can be fully circumvented, properties optimized for various metrics such highest maximum conductivity, lowest cost. While excessive nitrile fractions render mixtures flammable, careful selection component ratios yields highly performant, nonflammable that enable stable cycling Li4Ti5O12–LiNi0.8Mn0.1Co0.1O2 full cells over wide temperature range strong rate performance, facilitated fast conformational dynamics succinonitrile. WISHEs allow energy density ≈140 material, Coulombic efficiencies close 99.5% at 1C, capacity retention 53% 10C relative 1C.