TiO2@LiTi2(PO4)3 enabling fast and stable lithium storage for high voltage aqueous lithium-ion batteries

Anatase TiO2 is recognized as a promising negative electrode material when employing “water-in-salt” electrolytes in high voltage aqueous lithium-ion batteries. However, the catalytic property of water splitting aggravates the hydrogen evolution reaction, which hinders the formation of a stable solid electrolyte interphase (SEI) on the electrode surface and therefore results in poor cycling performance. To address this issue, nanostructured anatase TiO2 with amorphous LiTi2(PO4)3 as an artificial SEI coating layer is introduced. Amorphous LiTi2(PO4)3 layer enhances the ionic conductivity of TiO2, suppresses side reactions between electrode and electrolyte, and enables the formation of an effective SEI layer during the cycling. Thus, the TiO2@LiTi2(PO4)3 composite shows low polarization and high interface stability in an aqueous lithium-ion battery. As a result, a full cell LiMn2O4 |21 mol kg–1 LiTFSI in water |TiO2@LiTi2(PO4)3 demonstrates a high rate capability (60 mAh g−1 at 20 C) and a good cycling stability (capacity decay of 0.24% per cycle within 100 cycles). Systemic studies prove that TiO2@LiTi2(PO4)3 nanocomposite is an ideal negative electrode material candidate with low redox potential and high capacity for high voltage aqueous lithium-ion batteries.