The structural transformations that occur during cycling in black P anodes for Na-ion batteries were tracked with solid-state NMR, XRD, and DFT calculations. We found new NaxP structures via a computational genetic algorithm that allowed the assignment of various P motifs present in amorphous NaxP (a-NaxP) intermediates. During the first sodiation, P atoms at the end of a chain are observed as early as 0.60 V (Na0.52P) showing that P−P cleavage begins at this composition. In a-NaxP, P motifs that correspond to both P helices and the terminal unit in phosphorus zig-zags are observed. Once the potential drops below 0.22 V, c-Na3P-P63cm, which was predicted to form a priori, appears and persists during desodiation until >0.60 V. We find that Na3P-P63cm is formed in both Na-ion batteries and solid-state synthesis, indicating that both routes access the thermodynamically favorable structure. Slight differences in P-containing environments in a-NaP during sodiation/desodiation may result from different pathways that form extended P structures from the pristine black P vs isolated P atoms in c-Na3P-P63cm, respectively. At the end of desodiation, we find that black P is not re-formed, which may contribute to the poor capacity retention in this material. The combined approach of analyzing both experimental and theoretical chemical shift anisotropy can be extended to understand other structural transformations on (de)lithiation/(de)sodiation in not only P-containing materials, but also systems, such as Si, where distinct structural motifs, such as clusters and chains, play an important role in the battery chemistry of these largely amorphous phases.
Dr. Marbella has also used her expertise to collaborate on other projects in Prof. Grey’s laboratory. One of the PhD students that Dr. Marbella supervises, Yanting Jin, studies the solid electrolyte interphase (SEI) that forms on silicon anodes for Li-ion batteries - anodes that show similar degradation issues to P, resulting in two publications. Dr. Marbella has measured 7Li diffusivities in novel niobium tungsten oxide electrode materials for use in high rate Li-ion batteries - materials that represent a new strategy to design electrodes, which was accepted for publication in Nature. Dr. Marbella used her expertise in pulse field gradient NMR to supervise PhD student Simon Engelke in Prof. Grey’s laboratory to study 1H and 7Li diffusion in anisotropic Si substrates. Dr. Marbella has also pushed the use of MRI techniques within the Grey group, and has supervised a PhD student, Anna Gunnarsdóttir, who focuses on using MRI to understand the role of the SEI in Li dendrite growth. In collaboration with Peter Bruce’s Group at Oxford, she has used MRI to monitor Li dendrite growth in garnet-type solid electrolytes for the first time – work that is currently being written up for publication.
Exploitation and dissemination:
Publications:
1. Jin, Y.; Kneusels, N.-J. H.; Marbella, L. E.; Castillo-Martínez, E.; Weatherup, R. S.; Magusin, P. C. M. M.; Paul, S.; Grey, C. P. J. Am. Chem. Soc., 2018, DOI: 10.1021/jacs.8b03408.
2. Griffith, K. J.; Wiaderek, K. M.; Cibin, G.; Marbella, L. E.; Grey, C. P. Nature, 2018, DOI: 10.1038/s41586-018-0347-0.
3. Marbella, L. E.; Evans, M. L.; Groh, M. F.; Nelson, J.; Griffith, K. J.; Morris, A. J.; Grey, C. P. J. Am. Chem. Soc., 2018, 140, 7794.
4. Deringer, V. L.; Bernstein, N.; Bartók, A. P.; Cliffe, M. J.; Kerber, R. N.; Marbella, L. E.; Grey, C. P.; Elliott, S. R.; Csányi, G. J. Phys. Chem. Lett., 2018, 9, 2879.
5. Jin, Y.; Kneusels, N.-J. H.; Magusin, P. C. M. M.; Kim, G.; Castillo-Martinez, E.; Marbella, L. E.; Kerber, R. N.; Howe, D.; Paul, S.; Liu, T.; Wright, D.; Grey, C. P. J. Am. Chem. Soc., 2017, 139, 14992.
Presentations:
1. WMG Battery School, April 12, 2018, University of Warwick, Coventry, UK (invited talk)
2. Gordon Research Conference: Batteries: February 25-March 2, 2018, Ventura, CA (poster)
3. Lunchtime Research Seminar, November 19, 2017, Darwin College, Cambridge, UK (invited talk)
4. 254th ACS National Meeting, August 20-24, 2017, Washington, DC (talk and Sci-Mix poster)
5. 21st International Conference on Solid State Ionics: June 19, 2017, Padua, Italy (talk)
In preparation/submitted:
1. Marbella, L. E.; Zekoll, S.; Kasemchainan, J.; Bruce, P. G.; Grey, C. P. in preparation.
2. Engelke, S.; Marbella, L. E.; Trease, N. M.; De Volder, M.; Grey, C. P. submitted.
