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

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 NaTi 2 (PO 4) 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 NaTi 2 (PO 4) 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 NaTi 2 (PO 4) 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 84 mAh g−1 at 1000 mA g−1, and ultra-long cycling lifetime with 96% capacity retention after 1000 cycles. The finding in this study suggests that designing functional carbon-encapsulation structure can progress the NaTi 2 (PO 4) 3 anode material for long-lifespan aqueous SIBs. Unlabelled Image • A carbon-encapsulated NaTi 2 (PO 4) 3 framework is fabricated. • It exhibits excellent cycling performance with 96% retention after 1000 cycles. • Functional roles of the carbon encapsulation are carefully understood. [ABSTRACT FROM AUTHOR]