One-Step Synthesis of Carbon Supported Nb2O5 Particles for Electrochemical Capacitor Applications by Oxidation of Layered Nb2C

Tuesday, 7 October 2014: 15:40
Sunrise, 2nd Floor, Star Ballroom 1 (Moon Palace Resort)
M. Beidaghi (Drexel Nanomaterials institute, Department of Materials Science and Engineerring, Drexel University), C. Zhang, M. Lukatskaya (Drexel Nanomaterials Institute, Department of Materials Science and Engineerring, Drexel University), R. Maloney (2. Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA), B. Dunn (University of California - Los Angeles), and Y. Gogotsi (Dept of Mat. Sci. and Eng., Drexel University)
The crystalline network of orthorhombic niobium oxide (T-Nb2O5) offers two-dimensional transport pathways for fast intercalation of lithium ions, leading to its high and rate independent intercalation pseudocapacitance. Unlike many other lithium intercalation metal oxides, T-Nb2O5 can be charged in short periods of time, making it suitable as a supercapacitor electrode material. This is due to the fast solid-state diffusion and no structural change of T-Nb2O5 upon intercalation of Li ions. For practical applications of Nb2O5 and other metal oxides in supercapacitors, thick electrodes with large mass loadings are necessary. This, however, will result in ohmic losses and ion transport limitations due the relatively low electrical conductivity of the oxide and limited ion diffusion through the electrode thickness. To address these limitations, we have successfully prepared the layered Nb2O5/carbon hybrid materials through controlled oxidation of layered Nb2C (also called Nb2C-MXene). As-prepared Nb2O5/C well inherited the two dimensional structure of the precursor with Nb2O5 nanocrystals formed between the MXene layers. A detailed study of oxidation temperatures and durations was conducted to achieve nanostructured of T- Nb­­2O5 and XRD, SEM and TEM studies show the uniform formation T-phase of Nb2O5 on carbon sheets after oxidation at 850℃. The electrochemical characterization of thick electrodes of synthesized material show very promising performance, with specific capacitance of about 350 F/g in 1M LiClO4 /EC/DMC (1:1 in volume ratio) electrolyte. The performance of developed electrodes is believed to be highly dependent of layered two-dimensional structure of Nb­­2O5/carbon hybrid materials.

Acknowledgements: Authors acknowledge Dr. Mengqiang Zhao for his help with TEM studies. Support from DOE via Sandia National Laboratory is appreciated.