Sodiation and Desodiation via Helical Phosphorus Intermediates in High-Capacity Anodes for Sodium-Ion Batteries.

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Groh, Matthias F 
Nelson, Joseph 

Na-ion batteries are promising alternatives to Li-ion systems for electrochemical energy storage because of the higher natural abundance and widespread distribution of Na compared to Li. High capacity anode materials, such as phosphorus, have been explored to realize Na-ion battery technologies that offer comparable performances to their Li-ion counterparts. While P anodes provide unparalleled capacities, the mechanism of sodiation and desodiation is not well-understood, limiting further optimization. Here, we use a combined experimental and theoretical approach to provide molecular-level insight into the (de)sodiation pathways in black P anodes for sodium-ion batteries. A determination of the P binding in these materials was achieved by comparing to structure models created via species swapping, ab initio random structure searching, and a genetic algorithm. During sodiation, analysis of 31P chemical shift anisotropies in NMR data reveals P helices and P at the end of chains as the primary structural components in amorphous Na xP phases. X-ray diffraction data in conjunction with variable field 23Na magic-angle spinning NMR support the formation of a new Na3P crystal structure (predicted using density-functional theory) on sodiation. During desodiation, P helices are re-formed in the amorphous intermediates, albeit with increased disorder, yet emphasizing the pervasive nature of this motif. The pristine material is not re-formed at the end of desodiation and may be linked to the irreversibility observed in the Na-P system.

0306 Physical Chemistry (incl. Structural)
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J Am Chem Soc
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American Chemical Society (ACS)
Engineering and Physical Sciences Research Council (EP/P003532/1)
EPSRC (1644461)
Engineering and Physical Sciences Research Council (EP/L015552/1)
Engineering and Physical Sciences Research Council (EP/K014560/1)
Engineering and Physical Sciences Research Council (EP/P022596/1)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (750294)
Isaac Newton Trust (16.24(q))
L.E.M. acknowledges funding from the European Union’s Horizon 2020 – European Union research and innovation program under the Marie Skłodowska-Curie grant agreement No. 750294, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, of the U.S. DOE under Contract no. DE-AC02-05CH11231, under the Batteries for Advanced Transportation Technologies (BATT) Program subcontract no. 7057154, and the Charles and Katharine Darwin Research Fellowship for support. K.J.G. gratefully acknowledges funding from the Winston Churchill Foundation of the United States and the Herchel Smith Schol-arship. M.F.G. is grateful to the Engineering and Physical Sci-ences Research Council (EPSRC Grant No: EP/P003532/1). M.E. would like to acknowledge the EPSRC Centre for Doc-toral Training in Computational Methods for Materials Science for funding under grant number EP/L015552/1. A.J.M. and J.N. acknowledge the Winton Programme for the Physics of Sustainability. J.N. also acknowledges support from the Isaac Newton Fund. L.E.M. thanks Dr. Derrick Kaseman for provid-ing the Matlab script used to process 2D PASS data. We acknowledge Josh Stratford, Dr. Elizabeth Castillo-Martínez, Dr. Michael Gaultois, Dr. Pieter Magusin, and Prof. Michael Ruck (TU Dresden) for helpful discussions. NMR calculations were performed using the Cambridge Service for Data Driven Discovery (CSD3) operated by the University of Cambridge Research Computing Service (, provided by Dell EMC and Intel using Tier-2 funding from the Engineering and Physical Sciences Research Council, and Di-RAC funding from the Science and Technology Facilities Council ( Structure prediction calculations were performed using the resources of the Center for Function-al Nanomaterials, which is a U.S. DOE Office of Science Facil-ity, at Brookhaven National Laboratory under Contract No. DE-SC0012704 and the Thomas Tier 2 facility of the UK na-tional high performance computing service, for which access was obtained via the UKCP consortium and funded by EPSRC grant no. EP/K014560/1. Charles and Katharine Darwin Research Fellowship Winston Churchill Foundation of the United States Herchel Smith Scholarship (University of Cambridge) Winton Programme for the Physics of Sustainability Isaac Newton Fund