In situ nickel/carbon coated lithium titanium oxide anode material with improved electrochemical properties

In situ nickel/carbon coated Li4Ti5O12 has been synthesized successfully via a facile sol-gel method with chitosan serving as chelating agent and carbon source. The as-prepared samples are tested by different physical and electrochemical methods. The results of SEM and TEM indicate that the Ni/C layer was successfully coated on the surface of Li4Ti5O12 with the thickness of 2-3 nm. Furthermore, the Li4Ti5O12@Ni/C composite shows excellent rate capability and cycling stability. A large charge capacity of 237.3 mAh g(-1) can be remained after 100 cycles with the current of 0.1 A g(-1) between 0.02-3.0 V, which is close to its theoretical capacity (similar to 262 mAh g(-1)). Even at the current of 4.0 A g(-1), it still delivers a quite high charge capacity of 186.5 mAh g(-1) after 100 cycles, with no significant capacity fading. Additionally, the results of EIS reveal that the Li4Ti5O12@Ni/C electrode has faster lithium-ion diffusivity and less resistance compared with pure Li4Ti5O12. The remarkable improvement of the electrochemical properties should be attributed to the Ni/C coating layer, which acts as an effective conductor and a protective material against side reactions with electrolyte. (C) 2014 Elsevier Ltd. All rights reserved.