Fast Intercalation Reaction of Pseudocapacitive T-Nb2O5 Anode Material at Low Potentials

Pseudocapacitive materials such as transition metal oxides can exhibit electrochemical capacitive properties through Faradaic redox reactions. These materials feature increased specific capacity in comparison to activated carbon materials which have limited charge storage through double layer capacitance. Pseudocapacitive materials can also maintain high power and long cycle performance, thus making them promising supercapacitor materials. T-Nb2O5 has demonstrated capacitive properties showing square shapes in cyclic voltammetries (CV) at high scan rates [1,2]. The CVs are typically measured in the potential range of 1V - 3V (vs. Li/Li+). In this work, we studied T-Nb2O5 material as anode material in the low potential region, pseudocapacitive behavior was observed with high rate charge and discharge and long cycle life. Below 1V, fast intercalation of Li+ still occurs in the T-Nb2O5 without going through conversion reaction. Fig.1 showS the CV of T-Nb2O5 in Li+ electrolyte in the potential range of 0.1V - 2.5V (vs. Li/Li+), in situ XRD measurements also confirm the unchanged crystal structure of T-Nb2O5 below 1V. This pseudocapacitive property enables wider voltage window for a supercapacitor full cell using T-Nb2O5 anode. [1] V. Augustyn, J. Come, M.A. Lowe, J.W. Kim, P.-L. Taberna, S.H. Tolbert, H.D. Abruna, P. Simon, B. Dunn, “High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance”. Nature Mater., 12, 518-522 (2013). [2] X. Wang, G. Li, Z. Chen, V. Augustyn, X. Ma, G. Wang, B. Dunn, Y. Lu, “High Performance Supercapacitors Based on Nanocomposites of Nb2O5 Nanocrystals and Carbon Nanotubes. Adv. Energy Mater., 1, 1089-1093 (2011). Figure 1