Issue 35, 2021

Energy storage mechanisms in vacancy-ordered Wadsley–Roth layered niobates


Wadsley–Roth (WR) crystallographic shear structures demonstrate high energy and power densities as Li-ion battery anode materials. We report the (de)lithiation behavior of two WR-derived layered niobates: NaNb3O8 and KNb3O8. Both demonstrate multi-electron (Nb5+/Nb3+) redox on the first discharge, reacting with ≈5 mol Li per mol ANb3O8. Li intercalation in NaNb3O8 is dominated by Li-diffusion kinetics and evolution of the interlayer structure, with Li initially filling octahedral sites near the interlayer space to draw the layers together to form a (2 × 2) WR structure. This average structure change pushes Na ions into the square channels, blocking fast Li diffusion down the square channels that provide the fast Li-ion conduction in most WR materials. Upon charge, Li ions incorporated into the octahedral WR sites (ordered vacancies in the layered structure) are extracted, revealing a new, reversible Li site for additional capacity in WR-like materials. The behavior of KNb3O8 is similar, but has additional hysteresis associated with its larger counter-cation. While neither layered niobate matches the demonstrated performance of WR materials, by studying them, we identify a route for increased capacity in WR-like frameworks. Additionally, we identify the important role of Li diffusion kinetics and counter-cations in the cycling behavior of WR-derived structures.

Graphical abstract: Energy storage mechanisms in vacancy-ordered Wadsley–Roth layered niobates

Supplementary files

Article information

Article type
09 Apr 2021
01 Jul 2021
First published
11 Aug 2021
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2021,9, 20006-20023

Energy storage mechanisms in vacancy-ordered Wadsley–Roth layered niobates

K. McColl, K. J. Griffith, R. L. Dally, R. Li, J. E. Douglas, K. R. Poeppelmeier, F. Corà, I. Levin and M. M. Butala, J. Mater. Chem. A, 2021, 9, 20006 DOI: 10.1039/D1TA02992D

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