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Increasing the conductivity of crystalline polymer electrolytes

Nature volume 433, pages 50–53 (2005)Cite this article

Abstract

Polymer electrolytes consist of salts dissolved in polymers (for example, polyethylene oxide, PEO), and represent a unique class of solid coordination compounds. They have potential applications in a diverse range of all-solid-state devices, such as rechargeable lithium batteries, flexible electrochromic displays and smart windows1,2,3,4,5. For 30 years, attention was focused on amorphous polymer electrolytes in the belief that crystalline polymer:salt complexes were insulators. This view has been overturned recently by demonstrating ionic conductivity in the crystalline complexes PEO6:LiXF6 (X = P, As, Sb); however, the conductivities were relatively low6,7. Here we demonstrate an increase of 1.5 orders of magnitude in the conductivity of these materials by replacing a small proportion of the XF6- anions in the crystal structure with isovalent N(SO2CF3)2- ions. We suggest that the larger and more irregularly shaped anions disrupt the potential around the Li+ ions, thus enhancing the ionic conductivity in a manner somewhat analogous to the AgBr1-xIx ionic conductors8. The demonstration that doping strategies can enhance the conductivity of crystalline polymer electrolytes represents a significant advance towards the technological exploitation of such materials.

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Figure 1: Conductivity of PEO6:(LiAsF6)1-x(LiTFSI)x.
Figure 2: X-ray powder diffraction patterns of PEO6:(LiAsF6)1-x(LiTFSI)x.
Figure 3: DSC of PEO6:(LiAsF6)1-x(LiTFSI)x.
Figure 4: Fragment of the crystal structure of PEO6:(LiAsF6)1-x(LiTFSI)x.

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Acknowledgements

P.G.B. is indebted to The Royal Society, the EU and the EPSRC for financial support.

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Authors and Affiliations

  1. School of Chemistry, University of St Andrews, UK, St Andrews, KY16 9ST

    Alasdair M. Christie, Scott J. Lilley, Edward Staunton, Yuri G. Andreev & Peter G. Bruce

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  1. Alasdair M. Christie
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  2. Scott J. Lilley
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  3. Edward Staunton
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  4. Yuri G. Andreev
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  5. Peter G. Bruce
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Correspondence to Peter G. Bruce.

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Christie, A., Lilley, S., Staunton, E. et al. Increasing the conductivity of crystalline polymer electrolytes. Nature 433, 50–53 (2005). https://doi.org/10.1038/nature03186

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