Investigation of carbon phase evolutions in titanium nitride-carbon nanocomposites prepared in supercritical benzene with respect to their lithium storage capacity

Document Type: Article

Authors

1 Department of Materials Science and Engineering, Sharif University of Technology, Azadi Ave., P.O.Box 11155-9466, Tehran, .Iran.

2 Department of Materials Science and Engineering, Sharif University of Technology, Azadi Ave., P.O.Box 11155-9466, Tehran, .Iran

3 Department of Chemistry and Bioengineering, Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan.

Abstract

Titanium nitride-carbon nanocomposites have been synthesized by the reaction of TiCl4 and NaN3 in supercritical benzene medium that also serves as a carbon source. The as-prepared precursor has been subjected to different heat treatments under ammonia and nitrogen atmospheres. The structure and chemical composition of the synthesized TiN-C nanocomposites are studied by X-ray diffraction (XRD) and CHN elemental analysis. Meanwhile, the nature of carbonaceous species and the respective carbon phase transitions during supercritical process and following heat treatments are further investigated by Raman spectroscopy, time of flight secondary ion mass spectrometry (ToF-SIMS), and their charge-discharge characteristics with respect to lithium storage. After 10 h NH3-treatment at 1000 ˚C carbonaceous phase transforms to graphene layered structure. The highly efficient mixed TiN conducting network and the internal defects between G layers induced by nitrogen doping improve rate capability and cycling performance of G sheets and provides a specific capacity of 381 mAh g-1 at charge/discharge (C/D) rate of 0.2 C. The enhanced electrochemical performance of the SIV nanocomposite is mainly due to improving the electronic/ionic conductivity and reducing charge transfer coefficient and increasing electrochemical surface area that are resulted from anchoring of TiN nanoparticles on graphene sheets.

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