Hollow TiNb2 O7 @C Spheres with Superior Rate Capability and Excellent Cycle Performance as Anode Material for Lithium-Ion Batteries.

TiNb2 O7 , with high charge/discharge voltage (1.65 V), long life span, and excellent reversibility has become a new anode material for lithium ion batteries in recent years. However, the inherent poor electronic conductivity strictly limits its practical applications. Herein, we report for the first time hollow TiNb2 O7 @C spheres, with carbon spheres as sacrificial template. The special hollow structure can effectively relieve the volume expansion during the repeated process of charging/discharging. The conductivity of hollow TiNb2 O7 spheres can be greatly improved by the carbon layers uniformly coated outside the surface of TiNb2 O7 spheres. Besides, the particle aggregation can be conspicuously suppressed by the uniformly coated carbon layers. As a result, hollow TiNb2 O7 @C spheres show a prominent charge/discharge capacity of 282.6/283.8 mAh g-1 after 100 cycles at 0.25 C (1 C=388 mA g-1 ), revealing the excellent cycle performance and high reversible capacity. Meanwhile, the charge/discharge capacity of 157.5 and 157.9 mAh g-1 can be maintained at 10 C after 10 cycles. The facial synthetic method can be extended to prepare various materials with volume expansion during repeated charging/discharging process.