Electrochemical properties of bare and Ta-substituted Nb2O5 nanostructures

In this work, bare and Ta-substituted Nb2O5 nanofibers are prepared by electrospinning followed by sintering at temperatures in the 800–1100 °C range for 1 h in air. Obtained bare and Ta-substituted Nb2O5 polymorphs are characterized by X-ray diffraction, scanning electron microscopy, density measurement, and Brunauer, Emmett and Teller surface area. Electrochemical properties are evaluated by cyclic voltammetry and galvanostatic techniques. Cycling performance of Nb2O5 structures prepared at temperature 800 °C, 900 °C, and 1100 °C shows following discharge capacity at the end of 10th cycle: 123, 140, and 164 (±3) mAh g−1, respectively, in the voltage range 1.2–3.0 V and at current rate of 150 mA g−1 (1.5 C rate). Heat treated composite electrode based on M-Nb2O5 (1100 °C) in argon atmosphere at 220 °C, shows an improved discharge capacity of 192 (±3) mAh g−1 at the end of 10th cycle. The discharge capacity of Ta-substituted Nb2O5 prepared at 900 °C and 1100 °C showed a reversible capacity of 150, 202 (±3) mAh g−1, respectively, in the voltage range 1.2–3.0 V and at current rate of 150 mA g−1. Anodic electrochemical properties of M-Nb2O5 deliver a reversible capacity of 382 (±5) mAh g−1 at the end of 25th cycle and Ta-substituted Nb2O5 prepared at 900 °C, 1000 °C and 1100 °C shows a reversible capacity of 205, 130 and 200 (±3) mAh g−1 (at 25th cycle) in the range, 0.005–2.6 V, at current rate of 100 mA g−1.