Studies on the lithium ion diffusion coefficients of electrospun Nb 2O5 nanostructures using galvanostatic intermittent titration and electrochemical impedance spectroscopy

Abstract

We have studied the Li-diffusion coefficient values of electrospun Nb 2O5 nanofibers and nanonuggets for lithium batteries. In brief, Nb2O5 nanofibers were prepared by electrospinning followed by sintering at temperatures range 500-1100 °C for 1 h in air to obtain pseudo-hexagonal, orthorhombic (O), and monoclinic (M) Nb 2O5 phases. Electrochemical properties were evaluated by galvanostatic technique at room temperature. The H-, O- and M-Nb 2O5 polymorphs delivered discharge capacities (at second cycle) of 152, 189 and 242 (±5) mA h g-1, respectively. The lithium diffusion coefficients (DLi) are calculated using galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) techniques carried at room temperature. The evaluated DLi values by GITT for H-, O-, and M-Nb2O 5 phases are in the range 10-17-10-16, 10 -15-10-14, and 10-13-10-12 cm 2 s-1, respectively, in the voltage range 1.0-2.6 V vs. Li. DLi evaluated by EIS gave similar trend in the values but with a difference of one order higher magnitude. © 2013 Elsevier Ltd.