Lithium Copper(I) Orthophosphates Li3–xCuxPO4: Synthesis, Crystal Structures, and Electrochemical Properties

Authors

  • Katharina Snyder,

    1. Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
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  • Branimir Raguž,

    1. Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
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  • Wilfried Hoffbauer,

    1. Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
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  • Robert Glaum,

    Corresponding author
    1. Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
    • Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany, Fax: +49-228-735353

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  • Hartmut Ehrenberg,

    1. Karlsruher Institut für Technologie (KIT), Institut für Angewandte Materialien (IAM), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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  • Markus Herklotz

    1. IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
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  • Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/zaac.201300606 or from the author.

Abstract

Along the quasi-binary section Li3PO4 - CuI3PO4 three different phases Li3–xCuIxPO4 each with extended homogeneity range occur under equilibrium conditions (650 ≤ ; ≤ 700 °C). According to single-crystal X-ray structure analyses Phase 1 (0 < x ≤ 0.7) adopts the HT- or β-Li3PO4 structure type [Li2.6CuI0.4PO4, Pnma (no. 62), Z = 4, a = 10.4612(2) Å, b = 6.1690(3) Å, c = 4.9854(2) Å, R1 = 0.023, wR2 = 0.062, Goof = 1.12] and Phase 2 (0.9 ≤ x ≤ 1.8) is isotypic to LT- or α-Li3PO4 [Li2.05CuI0.95PO4, Pnm21 (no. 31), Z = 2, a = 6.2113(8) Å, b = 5.2597(7) Å, c = 4.9904(5) Å, R1 = 0.040, wR2 = 0.108, Goof = 0.98]. A preliminary structure model for the copper-rich Phase 3 (2.1 ≤ x ≤ 2.8) [“Li0.6CuI2.4PO4”, Pequation image (no. 147), a = 6.223(1) Å, c = 5.3629(5) Å] could be refined to R1 = 0.07. Sharp 31P-MAS-NMR resonances observed in the spectra of Li2.6CuI0.4PO4 (δiso = 10.4 ppm), Li2.05CuI0.95PO4 (δiso = 12.4 ppm), and Li0.84CuI2.16PO4 (δiso = 10.9 ppm) provide evidence for the absence of paramagnetic Cu2+ ions. Pure copper(I) orthophosphate CuI3(PO4) exists as a homogeneous melt ( ≥ 800 °C) and can be obtained as thermodynamically metastable solid by quenching. It is isotypic to Phase 3 [a = 6.284(3) Å, c = 5.408(5) Å]. Electrochemical delithiation of Li2.05CuI0.95PO4 (C/10, C/30) indicates two partially reversible oxidation processes between 3.75 V and 4.80 V (vs. Li0/Li+).

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