Ultrafast Nano-Crystalline and Highly-Dispersed-TiO2 (B) /CNF Composites for Negative Electrode of ‘Nanohybrid Capacitor’

Tuesday, 7 October 2014: 09:10
Sunrise, 2nd Floor, Star Ballroom 1 (Moon Palace Resort)
E. Iwama, M. Abe, T. Furuhashi, Y. Abe, J. Miyamoto, W. Naoi, and K. Naoi (Tokyo University of Agriculture and Technology)
We have been applying our original in-situ material processing technology called ‘Ultra-Centrifuging (UC) Treatment’ to prepare a novel ultrafast nano-crystalline Li4Ti5O12 (nc-LTO) /carbon nano fiber (CNF) composite electrode for the generation-II capacitive energy storage device of ‘Nanohybrid Capacitor’ producing more than triple  
energy density of a conventional electrochemical capacitor.[1] For the further improvement in the energy density of ‘Nanohybrid Capacitor’, LTO alternatives are needed. Among different candidates, TiO2 (B) possesses several advantages such as its 2-folds theoretical capacity (335 mAh g-1) of LTO  (175 mAh g-1) and the comparable redox potential (1.6 V vs. Li/Li+). In addition, TiO2 (B) is an industrially attractive material because of its inexpensive raw materials and its environmentally benign synthesis using only aqueous solution (e.g., water-soluble complexes [2]) without any Li-sources.[2-4] However, TiO2 (B) has intrinsic problems; its low electronic conductivity and Li+ diffusivity due to the b-axis oriented growth of TiO2 (B) [3]. In this report, we successfully synthesized b-axis shortened and hyper-dispersed nc-TiO2 (B)/CNF composites, which has a potential to substitute nc-LTO/CNF as a negative electrode of ‘Nanohybrid capacitor’. Inhibition of b-axis growth and hyper dispersion of TiO2 (B) into the carbon matrix were simultaneously achieved by the UC treatment and the subsequent hydrothermal method [4]. The prepared nc-TiO2/CNF exhibited 236 mAh g-1 (active material) at high rate of 300 C, which even exceeds that of nc-LTO/CNF composites. A significant decrease of peak intensity corresponding to the C-site intercalation around 2 V vs. Li/Li+ indicates that the Li+ was directly accommodated into A1 and A2 site of TiO2 (B) owing to the limitation of b-axis growth. Furthermore, the combined analysis of the N2 adsorption experiment and electochemical characterization suggests that the "dispersibility" of nc-TiO2 (B) on CNF matrix correlates closely with its electrochemical performance.     


[1] K. Naoi, et al., Energy & Environ. Sci., RSC, 5, (2012) 9363.

[2] a) M. Kobayashi, et al., Chem. Mater., 19, (2007) 5373.

[3] A. R. Armstrong et al., Chem. Mater., 22, (2010), 6426.

[4] Y. Ren, et al., Angewandte. Chem. Int. Ed, 51, (2012) 2164.