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Abstract
K-ion batteries (KIBs) have the potential to offer a cheaper alternative to Li-ion batteries (LIBs) using widely abundant materials. Conversion/alloying anodes have high theoretical capacities in KIBs, but it is believed that electrode damage from volume expansion and phase segregation by the accommodation of large K-ions leads to capacity loss during electrochemical cycling. To date, the exact phase transformations that occur during potassiation and depotassiation of conversion/alloying anodes are relatively unexplored. In this work, we synthesize two distinct compositions of tin phosphides, Sn4P3 and SnP3, and compare their conversion/alloying mechanisms with solid-state nuclear magnetic resonance (SSNMR) spectroscopy, powder X-ray diffraction (XRD), and density functional theory (DFT) calculations. Ex situ31P and 119Sn SSNMR analyses reveal that while both Sn4P3 and SnP3 exhibit phase separation of elemental P and the formation of KSnP-type environments (which are predicted to be stable based on DFT calculations) during potassiation, only Sn4P3 produces metallic Sn as a byproduct. In both anode materials, K reacts with elemental P to form K-rich compounds containing isolated P sites that resemble K3P but K does not alloy with Sn during potassiation of Sn4P3. During charge, K is only fully removed from the K3P-type structures, suggesting that the formation of ternary regions in the anode and phase separation contribute to capacity loss upon reaction of K with tin phosphides.
Original language | English |
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Pages (from-to) | 7460-7467 |
Number of pages | 8 |
Journal | Chemistry of Materials |
Volume | 34 |
Issue number | 16 |
Early online date | 1 Aug 2022 |
DOIs | |
Publication status | Published - 23 Aug 2022 |
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Dive into the research topics of 'Phase transformations and phase segregation during potassiation of SnxPy anodes'. Together they form a unique fingerprint.Projects
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Collaborative Computational Project in NMR Crystallography
Morris, A. (Principal Investigator)
Engineering & Physical Science Research Council
6/05/20 → 5/05/25
Project: Research Councils