Hollow TiNb2O7@C Spheres with Superior Rate Capability and Excellent Cycle Performance as Anode Material for Lithium-Ion Batteries

Graphical On the ball : The high charge/discharge voltage (1.65 V), long life span, and excellent reversibility of TiNb 2 O 7 have led to its use as an anode for lithium ion batteries. In order to overcome its inherent poor electronic conductivity, it is herein formed as hollow spheres, and coated with carbon, resulting in a much-improved anode performance. TiNb 2 O 7 , 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 TiNb 2 O 7 @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 TiNb 2 O 7 spheres can be greatly improved by the carbon layers uniformly coated outside the surface of TiNb 2 O 7 spheres. Besides, the particle aggregation can be conspicuously suppressed by the uniformly coated carbon layers. As a result, hollow TiNb 2 O 7 @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.