Abstract
Mixed conductors—single phases that conduct electronically and ionically—enable stoichiometric variations in a material and, therefore, mass storage and redistribution, for example, in battery electrodes. We have considered how such properties may be achieved synergistically in solid two-phase systems, forming artificial mixed conductors. Previously investigated composites suffered from poor kinetics and did not allow for a clear determination of such stoichiometric variations. Here we show, using electrochemical and chemical methods, that a melt-processed composite of the ‘super-ionic’ conductor RbAg4I5 and the electronic conductor graphite exhibits both a remarkable silver excess and a silver deficiency, similar to those found in single-phase mixed conductors, even though such behaviour is not possible in the individual phases. Furthermore, the kinetics of silver uptake and release is very fast. Evaluating the upper limit of the relaxation time set by interfacial ambipolar diffusion reveals chemical diffusion coefficients that are even higher than those achieved for sodium chloride in bulk liquid water. These results could potentially stimulate systematic research into powerful, even mesoscopic, artificial mixed conductors.
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Change history
26 October 2016
A Correction to this paper has been published: https://doi.org/10.1038/nature20143
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Acknowledgements
We acknowledge technical support by A. Fuchs (N2 isotherms), J. Liu (SEM), H. Hoier (XRD), V. Duppel (TEM) and R. Merkle (TGA). We are grateful to C. Wu for discussions and B. Lotsch for reading the manuscript.
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The scientific conception is due to J.M. C.-C.C. designed and executed the experiments. L.F. assisted in experiments and discussions. C.-C.C. and J.M. analysed the data, are responsible for the theoretical treatment and wrote the manuscript.
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This file contains Supplementary Text, Supplementary Figures 1-10 and Supplementary References. This file was replaced on 26 October as the original file was corrupted. (PDF 7225 kb)
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Chen, CC., Fu, L. & Maier, J. Synergistic, ultrafast mass storage and removal in artificial mixed conductors. Nature 536, 159–164 (2016). https://doi.org/10.1038/nature19078
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DOI: https://doi.org/10.1038/nature19078
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