Fabricating a carbon-encapsulated NaTi2(PO4)3 framework as a robust anode material for aqueous sodium-ion batteries

Abstract

Rechargeable sodium-ion batteries with aqueous electrolytes (aqueous SIBs) are highly desirable as low cost technologies for effective storage of intermittent sustainable energies because of their low cost and high safety. Polyanionic NaTi2(PO4)3 compound is particularly regarded as a promising anode material for aqueous SIBs, but suffering from low reaction kinetics and insufficient cycling stability in aqueous electrolytes. Herein, a carbon-encapsulated NaTi2(PO4)3 framework is fabricated as a high performance material for aqueous SIBs. Based on investigations of X-ray diffraction technique, elemental analysis and electrochemical measurements, it is found that the carbon encapsulation plays an important role in enhancing reaction kinetics of the material and suppressing dissolution of active NaTi2(PO4)3 component in aqueous electrolytes, therefore leading to improved structural stability and electrochemical reversibility. As a result, the material exhibits an impressive high-rate capability with a reversible capacity of 84mAhg−1 at 1000mAg−1, and ultra-long cycling lifetime with 96% capacity retention after 1000cycles. The finding in this study suggests that designing functional carbon-encapsulation structure can progress the NaTi2(PO4)3 anode material for long-lifespan aqueous SIBs.