Niobium pentoxide based materials for high rate rechargeable electrochemical energy storage.

The demand for high rate energy storage systems is continuously increasing driven by portable electronics, hybrid/electric vehicles and the need for balancing the smart grid. Accordingly, NbO based materials have gained great attention because of their fast cation intercalation faradaic charge storage that endows them with high rate energy storage performance. In this review, we describe the crystalline features of the five main phases of NbO and analyze their specific electrochemical characteristics with an emphasis on the intrinsic ion intercalation pseudocapacitive behavior of T-NbO. The charge storage mechanisms, electrochemical performance and state-of-the-art characterization techniques for NbO anodes are summarized. Next, we review recent progress in developing various types of NbO based fast charging electrode materials, including NbO based mixed metal oxides and composites. Finally, we highlight the major challenges for NbO based materials in the realm of high rate rechargeable energy storage and provide perspectives for future research.