High-performance aqueous symmetric sodium-ion battery using NASICON-structured Na2VTi(PO4)3

A high-safety and low-cost route is important in the development of sodium-ion batteries, especially for large-scale stationary battery systems. An aqueous sodium-ion battery is demonstrated using a single NASICON-structured Na 2 VTi(PO 4 ) 3 material with the redox couples of V 4+ /V 3+ and Ti 4+ /Ti 3+ working on the cathode and anode, respectively. The symmetric full cell fabricated based on the bi-functional electrode material exhibits a well-defined voltage plateau at ∼1.2 V and an impressive cycling stability with capacity retention of 70% exceeding 1,000 cycles at 10C (1C = 62 mA·g –1 ). This study provides a feasible strategy for obtaining high-safety and low-cost rechargeable batteries using a single active material in aqueous media.