Research Projects

Metal ion batteries (MIBs) are a popular choice in consumer electronics due to their high specific capacity, power density, longer life, and stable cycling performance. However, their use in electric vehicles and grid storage is limited due to their high flammability. Non-flammable aqueous electrolytes have emerged as potential alternatives, but their lower electrochemical stability window (ESW) of 1.23 V limits their energy density. A new class of water-in-salt electrolytes (WiSEs) has significantly expanded the ESW of aqueous electrolytes, with high concentrations of LiTFSI salt in water resulting in LIBs with an open circuit voltage of around 2.3 V and ~100% Coulombic efficiency for multiple charging-discharging cycles. Reducing the amount of water in the solvation shell of Li ions is an effective strategy to widen the electrochemical stability window of WiSEs. LiTFSI solubility in water can be increased to 55-60 m in the presence of ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EmimTFSI). The addition of non-volatile ILs further improves the safety of WiSEs. Mixing another salt, lithium trifluoromethane sulfonate (LiOTf), with LiTFSI leads to better solubility and wider ESW of the resulting water-in-bisalt electrolyte/solution (WiBSE). This study proposes investigating key interactions and microscopic structural ordering in different WiSEs, WiBSEs, and aqueous-salt-IL based hybrid electrolytes, which have wider ESW and better transport properties.

0