Promoting the performances of NaTi2(PO4)3 electrode for sodium ion battery by reasonable crystal design and surface modification

Abstract

Sodium-ion battery as an attractive energy storage system is acknowledged as alternative to lithium-ion battery on account of their extensive resources and low price. NaTi2(PO4)3 is considered as an excellent electrode material in sodium-ion battery due to open three-dimensional crystal channels for ion diffusion. In this work, reasonable crystal design of Zr doping and surface modification of carbon coating strategy was employed to promote the sodium storage performances of NaTi2(PO4)3 electrode. A series of NaTi2-xZrx(PO4)3/C (x = 0.05, 0.1, 0.15) composites with core@shell structure were synthesized through an easy sol-gel route, and were applied as electrode for sodium ion battery. The result shows that the crystal type of all samples is relatively pure. However, the dispersion of Zr doped samples are significantly improved compared to the blank sample. Among all the samples, NTP-Zr-0.1 (NaTi1.9Zr0.1(PO4)3/C) demonstrates the best charge/discharge performances. It delivers the discharge capacities of 206.3 mA h g-1 at 40 mA g-1 and 79.2 mA h g-1 at 2000 mA g-1, while those of NTP are 116.2 and 26.9 mA h g-1, severally. Superior electrochemical performance of NTP-Zr-0.1 is probably ascribed to the carbon coating structure, good dispersion, and lattice volume increase, further accelerating the transfer of electron and sodium ion. This study implies that carbon coating and Zr doping are facile and efficient strategy for promoting performances of NaTi2(PO4)3/C composite.