Dataset DOI: 10.5061/dryad.x3ffbg7t2

Description of the data and file structure

This zip file contains all main text data for the publication "A formal Fe^III/V redox couple in an intercalation electrode".

Replication data for Main Text Figures 1-4 associated with the mansucript, "A Formal Fe^III/V Redox Couple in an Intercalation Electrode". All files are zipped as 'Main_Text_Figures_Data.zip'. Copied below are the figure captions for each figure.

Figure 1: Two-phase crystallography is associated with two spectroscopic species.

a, Slow galvanostatic cycling behavior of sol-gel LFSO. The shading along the voltage curve corresponds to the state of (de)lithiation, which is used in the following subfigures as a legend for the state of (de)lithiation at which samples were harvested for ex-situ characterization. Inset: Pristine and delithiated LFSO crystal structures, viewed in the ac plane, showing the O3-O1 phase transition. Lithium and oxygen atoms are represented as light green and red spheres, respectively, and iron and antimony atoms are represented as light brown and dark blue octahedra, respectively. b, Ex-situ X-ray diffraction patterns collected for pristine and c, fully delithiated LFSO (with a constant voltage hold at 4.3 V). d, Ex-situ synchrotron X-ray diffraction patterns, with the (001) layering peak displayed to highlight the crystallographic phase transformation that occurs during delithiation and lithiation. Dashed grey lines indicate the positions of pristine and delithiated phases and are guides for the eye. e, ⁵⁷Fe Mössbauer spectra collected on ex-situ samples across the voltage plateau, measured at 95 K. The data is represented by dots. Pristine and delithiated components are represented with orange and blue shading, respectively, and the total fit is shown with colored solid lines which represent the state of (de)lithiation. A vertical bar indicates 1% absorption for each sample. f, Fe L_III-edge inverse partial fluorescence yield (iPFY) X-ray absorption spectra (XAS), collected on ex-situ samples across the voltage plateau. The data is represented by dots. Pristine and delithiated components are modelled with orange and blue shading, respectively, and the fit is shown with colored solid lines.

Figure 2: Delithiated LFSO adopts a formal Fe^V oxidation state.

The Fe L_III-edge iPFY XAS spectrum of delithiated end member shows good agreement with that of La₂LiFeO₆ (a) and is distinct from that of SrFeO₃ (d). We also observe this behavior using ⁵⁷Fe Mössbauer spectroscopy – the comparison with La₂LiFeO₆ shown in b and SrFeO₃ in e (reproduced with permission³⁹). The O K-edge XAS spectra of the delithiated component, La₂LiFeO₆ (c) and SrFeO₃ (f) all show a prominent peak at 528 eV. Note that the peak at 532 eV in the delithiated end member stems from SbV-O bonding, and the spectrum of Sb₂O₅ is overlaid (grey dashed trace) to highlight this.

Figure 3: Electronic ground states of Fe^III and Fe^V end members are modelled through RIXS and XAS calculations.

a, Experimental O K-edge RIXS of lithiated LFSO. b, OCEAN calculation of the O K-edge of pristine LFSO. c, Integrated and experimental and simulated O K-edge XAS of pristine LFSO. d, Experimental O K-edge RIXS of delithiated LFSO. e, OCEAN calculation of the O K-edge RIXS of delithiated LFSO. f, Integrated experimental and simulated O K-edge XAS of delithiated LFSO. g, Experimental Fe L_III-edge RIXS of pristine LFSO. h, Calculated Fe L_III-edge RIXS using hybridized multiplets in a 5-hole cluster, with a Fe^III (3d⁵) majority ground state. i, Integrated experimental and simulated Fe L_III-edge XAS of pristine LFSO. j, Experimental Fe L_III-edge RIXS of La₂LiFeO₆. k, Calculated Fe L_III-edge RIXS of La₂LiFeO₆ using hybridized multiplets in a 7-hole cluster, with a hybridized majority Fe^V (3d⁵L²) ground state. l, Integrated experimental and simulated Fe L_III-edge XAS of La₂LiFeO₆. In all subfigures, the incident energy is denoted Ein.

Figure 4: Introducing defects in LFSO suppresses Fe^III/V redox and engages O-O dimerization.

(a) Fe-Li disorder, quantified through refinement of neutron scattering data shows that as synthesized sol-gel LFSO has a low defect concentration compared to mechanically milled, solid state LFSO. Error bars represent uncertainties from Rietveld refinement of neutron scattering data are shown in black. (b) First cycle galvanostatic cycling at a current density of ≈3.55 mA/g (“≈C/50”) of sol-gel LFSO and the milled solid-state LFSO shows that milling decreases the charge and discharge capacities and increases voltage hysteresis. (c) Super partial fluorescence yield XAS shows that milling causes a reduction in the intensity of the Fe^V-O peak at 528 eV, and a simultaneous increase in the intensity of the O-O dimer peak at 531 eV. Arrows are added as guides for the eye. (d) Quantification of capacity from Fe^III/V redox using Mössbauer spectroscopy during the first charging cycle shows that the milled samples have excess capacity that cannot be accounted for by Fe^III/V redox alone. The dots were obtained from phase fractions obtained from fitting Mössbauer spectra, and the dashed lines represent lines of best fit to the dots. The excess capacity region, representing the region where the observed capacity is greater than that from Fe^III/V conversion, is shaded yellow.

Files and variables

Figure 1.

• All data is presented as .txt files, and an .ipynb Jupyter notebook is provided that generates a Matplotlib version of the final figure utilizing these .txt files.
• Fig1a_Echem.txt.
  • Galvanostatic cycling data includes the following columns: time/h, (Q-Qo)/mA.h/g, I/mA, Ewe/V, Ns. These correspond to the elapsed time after measurement, gravimetric capacity, current, voltage, and step number.
• Fig1b_Pristine_APS_XRD.txt.
  • Refined synchrotron X-ray diffraction data from the Advanced Photon Source, measured on pristine sample. Columns include: d(Å), 14A_Pri.xye, SigmaYobs, Ycalc, Diff, Q(Å⁻¹), which correspond to the d-spacing, the data, the observed intensity, the calculated intensity, the difference. between observed and calculated intensity, and the scattering vector.
• Fig1c_DelithiatedwCVhold_APS_XRD.txt
  • Refined synchrotron X-ray diffraction data from the Advanced Photon Source, measured on sample delithiated to 4.3 V with a voltage hold. Columns include: d(Å), 14A_Pri.xye, SigmaYobs, Ycalc, Diff, Q(Å⁻¹), which correspond to the d-spacing, the data, the observed intensity, the calculated intensity, the difference. between observed and calculated intensity, and the scattering vector.
• Fig. 1d. X-ray diffraction data from the Stanford Synchrotron Lightsource. Each consists of columns: Q(Å⁻¹), Sqrt. Intensity, which correspond to the scattering vector and the square root of observed intensity at a different state of charge.
  • Fig1d_Pri_SSRL_XRD.txt
    • Ex-situ XRD of pristine material.
  • Fig1d_1ov3Delith_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 1/3 capacity.
  • Fig1d_2ov3Delith_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 2/3 capacity.
  • Fig1d_Delith4p3V_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 4.3 V.
  • Fig1d_1ov3Lith_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 4.3 V, then lithiated to 1/3 capacity.
  • Fig1d_2ov3Lith_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 4.3 V, then lithiated to 2/3 capacity.
  • Fig1d_Lith3p2V_SSRL_XRD.txt
    • Ex-situ XRD of material delithiated to 4.3 V, then lithiated to 3.2 V.
• Fig. 1e. Mössbauer spectra collected at 95 K. Columns may include: Velocity (mm/s), Data, Total Fit, Delithiated Component, Pristine Component.
  • Fig1e_Mossbauer_Pristine.txt
    • Ex-situ Mössbauer spectrum of pristine material.
  • Fig1e_Mossbauer_HalfDelith.txt
    • Ex-situ Mössbauer spectrum of material delithiated to 1/2 capacity.
  • Fig1e_Mossbauer_Delith4p3V.txt
    • Ex-situ Mössbauer spectrum of material delithiated to 4.3 V.
  • Fig1e_Mossbauer_Halflith.txt
    • Ex-situ Mössbauer spectrum of material delithiated to 4.3 V, then lithiated to 1/2 capacity.
  • Fig1e_Mossbauer_Lith3p2V.txt
    • Ex-situ Mössbauer spectrum of material delithiated to 4.3 V, then lithiated to 3.2 V.
• Fig. 1f. Fe L-edge XAS data collected in the inverse partial fluorescence mode (iPFY). Columns may include: Energy (eV), Intensity, Pri_Comp, Delith_Comp, Total_Fit. Pri_Comp corresponds to the pristine component, Delith_Comp to the delithiated compoenent, and Total_Fit to the total fit.
  • Fig1f_FeLXAS_Pristine.txt
    • Ex-situ Fe L-edge spectrum of pristine material.
  • Fig1f_FeLXAS_1ov3Delith.txt
    • Ex-situ Fe L-edge spectrum of delithiated to 1/3 capacity.
  • Fig1f_FeLXAS_2ov3Delith.txt
    • Ex-situ Fe L-edge spectrum of delithiated to 2/3 capacity.
  • Fig1f_FeLXAS_Delith4p3V.txt
    • Ex-situ Fe L-edge spectrum of material delithiated to 4.3 V.
  • Fig1f_FeLXAS_1ov3Lith.txt
    • Ex-situ Fe L-edge spectrum of material delithiated to 4.3 V, then lithiated to 1/3 capacity.
  • Fig1f_FeLXAS_2ov3Lith.txt
    • Ex-situ Fe L-edge spectrum of material delithiated to 4.3 V, then lithiated to 2/3 capacity.
  • Fig1f_FeLXAS_Lith3p2V.txt
    • Ex-situ Fe L-edge spectrum of material delithiated to 4.3 V, then lithiated to 3.2 V.

Figure 2.

• Fig. 2a and d. Fe L-edge XAS in iPFY mode.
  • Fe_L3_XAS_LFSO_Delithiated_component_xaxis.npy
    • NumPy binary file which includes the x-axis (Energy / eV) data for the delithiated component spectrum.
  • Fe_L3_XAS_LFSO_Delithiated_component_yaxis.npy
    • NumPy binary file which includes the y-axis (Intensity / a.u.) data for the delithiated component spectrum.
  • Fe_L3_RIXS_La2LiFeO6
    • Folder which contains the raw scan files for a RIXS scan on La₂LiFeO₆.
    • LLFO_FeL3_fullHR_15687-AI.txt
      • This is a "legend" for the X-ray emission scans located in the "Andor" folder. Columns include, Time, Frame #, BL 8 Energy, Izero, Izero 2, TFY, TEY, Sample Current, Beam Current, Total Flux, Counts, Background, Filename. The "BL 8 Energy" columns.
    • Andor
      • This folder contains emission raw data files (ending in "-1D.txt") that can be plotted together to visualize the RIXS map. The iPFY data is processed from this data.
  • Fe_L3_RIXS_SrFeO3
    • Folder which contains the raw scan files for a RIXS scan on SrFeO₃, as for La₂LiFeO₆.
    • HR_SFO_HT_FeL3_6302-AI.txt
      • This is a "legend" for the X-ray emission scans located in the "Andor" folder. Columns include, Time, Frame #, BL 8 Energy, Izero, Izero 2, TFY, TEY, Sample Current, Beam Current, Total Flux, Counts, Background, Filename. The "BL 8 Energy" columns.
    • Andor
      • This folder contains emission raw data files (ending in "-1D.txt") that can be plotted together to visualize the RIXS map. The iPFY data is processed from this data.
• Fig. 2b and e. Mössbauer spectra.
  • Mossbauer_SrFeO3.csv
    • This is a .csv file with two columns: Absorption (%) versus Velocity (mm/s), for SrFeO₃, reproduced with permission from Gallagher, P. K., MacChesney, J. B. & Buchanan, D. N. E. Mössbauer Effect in the System SrFeO2.5–3.0. J. Chem. Phys. 41, 2429–2434 (1964).
  • Mossbauer_LFSO_Delithiated_component.txt
    • This is a .txt file with two columns: Absorption (%) versus Velocity (mm/s), for Mössbauer data of the delithiated component of LFSO (determined from the fits of charged LFSO spectra).
  • Mossbauer_La2LiFeO6.txt
    • This is a .txt file with two columns: Absorption (%) versus Velocity (mm/s), for Mössbauer data collected on La₂LiFeO₆.
• Fig. 2c and f. O K-edge XAS.
  • OK_XAS_Sb2O5.csv.csv
    • This is a .csv file with two columns: Energy (eV) and Intensity (a.u.) for O K-edge XAS collected on Sb₂O₅.
  • OK_RIXS_Intensities_LFSO_delithiated_component.npy
    • This is the npy file that contains a 2 dimensional array of the raw O K-edge RIXS intensities (in arbitary units) of the delithiated sample of LFSO. The 2 dimensions consist of Excitation energies and emission energies (see below).
  • OK_RIXS_Excitation_energies_LFSO_delithiated_component.npy
    • This is a 1 dimensional array of the excitation energies (incident energies) in eV used to collect O K-edge RIXS measurements on delithiated LFSO.
  • OK_RIXS_Emission_energies_LFSO_delithiated_component.npy
    • This is a 1 dimensional array of the emission energies (incident energies) in eV used to collect O K-edge RIXS measurements on delithiated LFSO.
  • OK_RIXS_SrFeO3
    • This folder contains emission raw data files (ending in "-1D.txt") that can be plotted together to visualize the O K-edge RIXS map, from which the O K-edge PFY XAS can be integrated, for SrFeO₃.
  • OK_RIXS_La2LiFeO6
    • This folder contains emission raw data files (ending in "-1D.txt") that can be plotted together to visualize the O K-edge RIXS map, from which the O K-edge PFY XAS can be integrated, for La₂LiFeO₆.

Figure 3.

• plot_figure_3_L_edge.py
  • Plotting script to plot Fe L-edge RIXS map, uses python3 and relevant libraries.
• plot_figure_3_K_edge.py
  • Plotting script to plot O K-edge RIXS map, uses python3 and relevant libraries.
• pristine_ocean
  • This directory contains the XAS and RIXS OCEAN calculation results for the O K-edge. For the XAS, it includes all the absspct files from OCEAN corresponding to the oxygen atoms in the calculation. The first column is the incident energy and second column the intensity. For the RIXS, the full map was calculated in different batches (absspct_X and rxsspct_X, for X = 0, 1, 2, ...). For each incident energy in any of the absspct files in absspct_X, there is a corresponding rxsspct file in rxsspct_X, showing the RIXS at that incident energy. The second to last index in the rxsspct file corresponds to the index of the incident energy in the absspct file. The first column in rxsspct is the energy loss, and the third column is the RIXS cross-section.
• pristine_multiplet
  • This directory contains the XAS and RIXS files for the multiplet calculations, as well as other output from the code. The XAS files have two columns: incident energy and intensity. The RIXS files contains three columns, the first is the incident energy, the second is the energy loss, and the third is the intensity. This is true for both the Fe L-edge and O K-edge.
• pristine_experiment
  • These are the raw experimental data files, where the first column are the incident energies, the first row are the emitted photon energies, and the cell blocks tying an incident energy to an emitted energy is the intensity for that particular transition.
• charged_ocean
  • Same structure as pristine_ocean.
• charged_multiplet
  • Same structure as pristine_multiplet.
• charged_experiment
  • Same structure as pristine_experiment.

Figure 4.

• O K-edge XAS measured in the super partial fluorescence yield (sPFY) mode. The following three files contain the sPFY XAS data for the LFSO without ball milling (sPFY_0h_Ball_milling.npy), with 1 h of milling (sPFY_1h_Ball_milling.npy) and 20 h of milling (sPFY_20h.npy). These are obtained from integrating the RIXS emissions for these samples (shown in the SI) between the emission energies of 522-524 eV.
  • sPFY_20h.npy
  • sPFY_1h_Ball_milling.npy
  • sPFY_0h_Ball_milling.npy
• Electrochemical Data_BallMilling.xlsx
  • Includes galvanostatic cycling data for the sol-gel sample ("SG"), solid-state synthesized ball-milled for 1 h ("1h"), and solid-state synthesized ball-milled for 20 h ("20 h") samples. Each contains a column for gravimetric capacity "(Q-Qo)/mA.h/g" and voltage "Ecell/V".

All data files in this dataset can be read using Python, Numpy, and Pandas. Jupyter notebooks are included to read and process the data.