NASICON-type TiNb(PO4)3 Anode with High-Energy-Density and Long Cycle Life Enables Aqueous alkaline-Ion Batteries.

High-energy-density aqueous alkaline-ion batteries have drawn significant attention due to their intrinsic high security and low cost. As suitable anode materials with satisfying capacity and proper operating potential in aqueous electrolyte are limited, it is urgent to find candidate materials to build aqueous alkaline-ion batteries for practical applications. For the first time, highly crystalline NASICON -type phase TiNb(PO4)3 (TNPO) was explored as alkali ion intercalation host in aqueous battery technology. The TNPO material manifests high specific capacity of 94 mAh g-1 at 5C rate together with superior cyclic stability and remarkable rate capacity in aqueous electrolytes, which is assigned to its super stable three-dimensional (3D) tunnel structure. Furthermore, the aqueous lithium-ion battery based on TNPO anode and LiMn2O4 (LMO) cathode delivers a high specific energy of 121 wh kg-1 and a specific power of 189 W kg-1 with an output voltage of 2.1 V, while it exhibits excellent cycling performance (82% capacity retention after 1000 times at 5C rate). The remarkably overall performances of TNPO anode have clearly suggested that TNPO can be used as a promising electrode material of aqueous alkaline-ion batteries with high-energy-density for energy storage in future.