Nano tube-in-tube CNT@void@TiO2@C with excellent ultrahigh rate capability and long cycling stability for lithium ion storage

Abstract

Herein, we synthesize a unique nano tube-in-tube material with carbon nanotube as internal tube, TiO2 nanotube as external tube. A layer of amorphous carbon shell is further tightly coated on the surface of TiO2 nanotube. These structural features significantly improve structure stability and electronic conductivity of TiO2. Accordingly, CNT@void@TiO2@C exhibits the impressive electrochemical performance, including excellent ultrahigh rate capability (55 mAh g−1 at 300C), high reversible capacity (601–468 mAh g−1 at 0.5 C), and outstanding long-term cycling stability (180.3 mAh g−1 up to 3000 cycles with capacity loss rate of 0.013% per cycle at 10C). It is worth noting that after a series of ultrahigh rate tests, the discharge capacity may still recover to 90% of the initial 1C, confirming excellent structural stability and high reversibility. Kinetic analysis reveals the pseudocapacitive lithium storage behavior dominates lithium storage reaction of TiO2, which coincides well with large specific surface area (326 m2 g−1) of the nano tube-in-tube. The capacitive contribution to the total current is as high as 78.5% at scan rate of 2 mV S−1. This work provides a new perspective to understand and design high performance TiO2 composite for lithium ion batteries.