Affordable energy storage is crucial for a variety of technologies. One option is sodium-ion batteries (NIBS) for which, however, suitable anode materials are still a problem. We report on the application of a promising new class of materials, polyoxometalates (POMs), as an anode in NIBs. Specifically, Na-6[V10O28]center dot 16H(2)O is being synthesized and characterized. Galvanostatic tests reveal a reversible capacity of approximately 276 mA h g(-1) with an average discharge potential of 0.4 V vs. Na/Na+, as well as a high cycling stability. The underlying mechanism is rationalized to be an insertion of Na+ in between the [V10O28](6-) anions rather than an intercalation into a crystal structure; the accompanying reduction of V+v to V+IV is confirmed by X-ray Photoelectron Spectroscopy. Finally, a working full-cell set-up is presented with the POM as the anode, substantiating the claim that Na-6[V10O28]center dot 16H(2)O is a promising option for future high-performing sodium-ion batteries. (c) 2015 Elsevier B.V. All rights reserved.