Enabling high-performance aqueous rechargeable Li-ion batteries through systematic optimization of TiS2/LiFePO4 full cell

Highlights: • An aqueous TiS₂/LiFePO₄ lithium-ion full cell is investigated. • Optimal operating voltage window of the aqueous full cell is found to be 0.01–1.6 V. • Addition of 0.1 wt% TMSB electrolyte additive enhances the capacity and kinetics. • Modulation of current collectors enhances cyclability and efficiency of the full cell. • The optimized cell displays stable cycling with a coulombic efficiency of ~99.9%. The conventional lithium-ion batteries (LIBs) have dominated the portable electronics markets; however, inherent limitations have raised concerns over their cost, safety, and greenness in large scale energy storage applications. Taking advantage of the recently developed "Water-in-Salt" electrolyte (WiSE), an aqueous lithium-ion battery of TiS₂/LiFePO₄ (LFP) is demonstrated. The effects of potential window, addition of tris(trimethylsilyl) borate (TMSB) salt, and the choice of current collector on cell performance are investigated. The aqueous TiS₂/LFP cell delivers an energy density of 65 Wh kg⁻¹, based on the total mass of electrodes. The presence of TMSB additive enhances the capacity, stability, and efficiency of the cell. Compared to the control cell, the capacity increases by 34%, SEI layer resistance decreases by 1.7 times, and the charge transfer resistance decreases by 7 times, yielding high coulombic efficiency of 99.9% and capacity retention of 70% after 100 cycles. A safe potential window of 0.01–1.6 V, 0.1 wt% TMSB in WiSE, and stainless-steel current collector on the cathode and titanium on the anode offer the most stable cycling. The combination of low-cost electrodes, safer and greener electrolyte, and high coulombic efficiency make this new aqueous battery promising for large scale energy storage systems.