Influence of reduction treatment for TiNb <sub>2</sub> O <sub>7</sub> nanoparticles on the electrochemical properties for Li‐ion batteries
Chang‐Ying Ou, Sudipta Som, Karan Kumar Gupta, Chun Yu, Chung‐Hsin Lu
Abstract
Abstract The discharge capacities and rate capability of TiNb 2 O 7 powders were enhanced through the additional postreduction treatment. X‐ray photoelectron spectroscopy and electron paramagnetic resonance results confirmed the formation of oxygen vacancies in TiNb 2 O 7 powders after a reduction treatment. The appearance of oxygen vacancies in TiNb 2 O 7 powders formed the impurity level in the forbidden gap and decreased the bandgap values of TiNb 2 O 7 . Compared with the pristine TiNb 2 O 7 powders, when TiNb 2 O 7 powders were reduced at 400°C for 40 min, the charge transfer resistance of prepared samples was reduced from 43.67 to 19.35 Ω, and the pseudocapacitive contribution of TiNb 2 O 7 was increased from 44% to 59%. In addition, the discharge capacities at 0.1 and 20 C of prepared batteries were increased by 10.84% and 105.85%, respectively. On the other hand, increasing the temperature in the reduction treatment caused the formation of Ti 4+ /Ti 3+ and Nb 5+ /Nb 4+ pairs and decreased the amounts of available redox couples, thereby deteriorating the electrochemical performance of prepared batteries. The results in the present study revealed that the discharge capacities and rate capability of TiNb 2 O 7 powders were enhanced through a postreduction treatment.