Reversible Hydration Enabling High-Rate Aqueous Li-Ion Batteries

High Resolution Image Download MS PowerPoint Slide Layered TiS 2 has been proposed as a versatile host material for various battery chemistries. Nevertheless, its compatibility with aqueous electrolytes has not been thoroughly understood. Herein, we report on a reversible hydration process to account for the electrochemical activity and structural evolution of TiS 2 in a relatively dilute electrolyte for sustainable aqueous Li-ion batteries. Solvated water molecules intercalate in TiS 2 layers together with Li + cations, forming a hydrated phase with a nominal formula unit of Li 0.38 (H 2 O) 2−δ TiS 2 as the end-product. We unambiguously confirm the presence of two layers of intercalated water by complementary electrochemical cycling, operando structural characterization, and computational simulation. Such a process is fast and reversible, delivering 60 mAh g –1 discharge capacity at a current density of 1250 mA g –1 . Our work provides further design principles for high-rate aqueous Li-ion batteries based on reversible water cointercalation.