N-modified carbon-coated NaTi2(PO4)3 as an anode with high capacity and long lifetime for sodium-ion batteries.

ABSTRACT

NASICON-type NaTi2(PO4)3 is recognized as a promising energy storage anode due to its high ionic conductivity and low cost. In this work, N-modified carbon-coated sodium titanium phosphate (NTPGN) composites were prepared by the sol-gel method by using sodium glutamate as a source of nitrogen and partial carbons. The addition of sodium glutamate forms a loose structure of nano-spherical flowers on the surface of sodium titanium phosphate, which shows a higher specific capacity, better rate performance, and excellent cycling performance compared to the carbon-coated titanium phosphate derived only from citric acid. The discharge capacities of NTPGN at 0.1 C, 5 C, 10 C, 20 C, and 30 C are 132.8, 132, 131.4, 105.9, and 98.2 mA h g-1, respectively. In particular, after 1000 cycles at 20 C, the discharge capacity is 102.6 mA h g-1 with a capacity retention rate of 96%. This work reveals that the combination of carbon coating and nitrogen doping using sodium glutamate improves the electrochemical performance of electrode materials.