Apparently Na + in the tunnels of NaNb7O18 is a minor but surmountable inconvenience. These results do not suggest that the tunnel defects are beneficial nor that NaNb7O18 is the best-inclass material, but, by comparison to other 1D diffusion phases such a LFP, they are strong evidence that the parallel tunnels in the Wadsley-Roth structure give rise to an inherent defect tolerance and that this could be considered as a unique and useful criterion when designing or engineering ion transport materials such as electrodes or solid electrolytes of the future. It is also worth noting that an additional challenge for electrode materials, relative to electrolytes, is that fast ion transport must be maintained over a wide state-of-charge range corresponding to large changes in composition, volume, and the nature of transition states along the diffusion pathway. NaNb7O18 is not only capable of high-rate transport at a single composition, e.g., dilute LixNaNb7O18, but it maintains this behavior over a range of a capacities, first-order phase transition(s), and a volume change of up to 5.9%.