Fast Sodium‐Ion Conductivity in Supertetrahedral Phosphidosilicates |
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Authors: | M?Sc Arthur Haffner M?Sc Anna‐Katharina Hatz Dr Igor Moudrakovski Prof?Dr Bettina V Lotsch Prof?Dr Dirk Johrendt |
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Institution: | 1. Department of Chemistry, Ludwig-Maximilians-Universit?t München, München, Germany;2. Department of Nanochemistry, Max Planck Institute for Solid State Research, Stuttgart, Germany |
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Abstract: | Fast sodium‐ion conductors are key components of Na‐based all‐solid‐state batteries which hold promise for large‐scale storage of electrical power. We report the synthesis, crystal‐structure determination, and Na+‐ion conductivities of six new Na‐ion conductors, the phosphidosilicates Na19Si13P25, Na23Si19P33, Na23Si28P45, Na23Si37P57, LT‐NaSi2P3 and HT‐NaSi2P3, based entirely on earth‐abundant elements. They have SiP4 tetrahedra assembled interpenetrating networks of T3 to T5 supertetrahedral clusters and can be hierarchically assigned to sphalerite‐ or diamond‐type structures. 23Na solid‐state NMR spectra and geometrical pathway analysis show Na+‐ion mobility between the supertetrahedral cluster networks. Electrochemical impedance spectroscopy shows Na+‐ion conductivities up to σ (Na+)=4×10?4 S cm?1. The conductivities increase with the size of the supertetrahedral clusters through dilution of Na+‐ions as the charge density of the anionic networks decreases. |
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Keywords: | crystal structures ion conductivity phosphidosilicates sodium supertetrahedra |
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