TiO₂ (B) anode for high-voltage aqueous Li-ion batteries

Aqueous Li-ion batteries (ALIBs) are regarded as promising large-scale energy storage technology because of their intrinsic safety and cost-effectiveness. However, because of the "cathodic challenge" encountered using aqueous electrolytes, the choice of anode material is restricted to candidates having relatively high redox potential and low capacity, thus resulting in low energy density. In this communication, we report a TiO2 B anode for ALIBs that has low lithiation potential (similar to 1.6 V in nonaqueous electrolytes and similar to 1.8 V in aqueous electrolytes), high capacity (similar to 200 mAh/g), and high structural stability. When the TiO2 B anode is paired with spinel LiMn2O4, the LiMn2O4//TiO2 B full cell can deliver high capacity (194.5 mAh/g, based on the anode mass) and high energy density (150 Wh/kg, based on the total electrode mass). Furthermore, a full cell employing this anode displays superior cycling performance with a high capacity retention of 76% after 400 cycles at 1 C, this is attributed to the structural stability of the TiO2 B nanowires and the wide electrochemical stability window of the Water-in-Salt (WIS) electrolyte. It is anticipated that the TiO2 B anode can provide a new option for constructing high-energy ALIBs.