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

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.