Investigating the influence of synthesis route on the crystallinity and rate capability of niobium pentoxide for energy storage

• Published in: Electrochimica acta Vol. 392; p. 138964
• Main Authors: Wheeler-Jones, Evangeline C., Loveridge, Melanie J., Walton, Richard I.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2021
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.138964

•High surface area nano-structured Nb2O5 created via a simple hydrothermal method.•Anisotropically crystalline Nb2O5 related to T-structure characterised electrochemically.•Anisotropically crystalline, T and H- Nb2O5 capable of cycling to rates of 100 C.•H-Nb2O5 presented as a high rate anode without the need for carbon integration.•All materials have high current stability tested at 20C over 200 cycles. Orthorhombic niobium pentoxide (T-Nb2O5) is known to be an effective anode material for Li-ion batteries (LIBs) with very high rate capability, but the other Nb2O5 polymorphs and non-crystalline phases have lacked thorough exploration. A simple hydrothermal mechanism is used to produce an anisotropically crystalline ‘as-synthesised material’, which has not previously been characterised electrochemically. The as-synthesised material is heat-treated to produce T-Nb2O5 at 600°C and monoclinic (H-) Nb2O5 at 1000°C. We present electrochemical properties for all of these materials. Collectively we report rate sweeps and demonstrate high current stability (20 C-rate capability) and a long life span, up to 200 cycles. We propose the H-phase as a high rate anode when prepared via an anisotropically crystalline precursor, as it is able to demonstrate 60 % capacity retention after 200 cycles at a notably high current flux of 20 C. Such high rates results are rare for this material without integration with carbon materials. For the anisotropically crystalline Nb2O5 material, we achieve cycling rates up to 100 C with 80% capacity recovery upon current reduction, representing an important discovery in the development of very high rate anode materials. [Display omitted]