Aqueous lithium-ion battery of dual electrolytes separated by cation-exchange membrane with enhanced rate capability for thick electrodes

Aqueous lithium-ion batteries (ALIBs) have received increasing attention because of their high safety. An aqueous electrolyte system compatible with a wider electrochemical window and high ionic conductivity is desired to increase the industrial potential of ALIBs. In this study, a dual-electrolyte system separated by a perfluorosulfonated cation-exchange membrane (CEM) was designed to demonstrate a 2 V-class ALIB. The specific compositions of the cathode and anode electrolytes to be stable in facing via the CEM were experimentally determined, where each electrolyte pH was adjusted for the lithiation/delithiation of LiMn2O4 and TiO2, together with a high ionic conductivity of >70 mS/cm. The pH difference successfully suppressed water splitting, which enabled stable battery operation in the 1.5-2.8 V range with >99 % Coulombic efficiency. The optimized cathode and anode electrolytes also exhibited better rate performances even in a thick electrode layer over 50 mg/cm(2) of the active material loading than a conventional concentrated electrolyte of 21 mol/kg LiTFSI (9 mS/cm). The present system, which employs the aqueous electrolytes with smaller lithium salts and favorable ionic conductivities should increase the industrial potential of low-cost aqueous lithium-ion batteries.