Carbon-coated hierarchical NaTi2(PO4)3 mesoporous microflowers with superior sodium storage performance

NASICON structured NaTi2(PO4)(3) with stable and open framework has become a promising electrode material for sodium-ion batteries. However, the intrinsic low electronic conductivity of NaTi2(PO4)(3) leads to inferior rate capability and poor active material utilization. Herein, we first report the synthesis of carbon-coated hierarchical NaTi2(PO4)(3) mesoporous microflowers (NTP/C-F), via a facile and controllable solvothermal method and subsequent annealing treatment. The unique structural features endow the NTP/C-F with excellent structural stability, enhanced charge transfer kinetics, and suppressed polarization. This architecture exhibits superior sodium storage performance: high initial capacity (125 mA h g(-1) at 1 degrees C), outstanding rate capability (95 mA h g(-1) at 100 degrees C), and ultra-long cycling stability (capacity retention of 77.3% after 10,000 cycles at 20 degrees C). Time-resolved in-situ X-ray diffraction study reveals a typical two-phase electrochemical reaction with reversible structure change. This work suggests the integration of hierarchical structure and carbon coating provides a promising approach for boosting the electrochemical performances of battery electrode materials. (C) 2016 Published by Elsevier Ltd.