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Combining electrochemistry (EC) and nuclear magnetic resonance (NMR) techniques has evolved from a challenging concept to an adaptable and versatile method for battery and electrolysis research. Continuous advancements in NMR hardware have fostered improved homogeneity of static magnetic field, B0, and radio frequency field, B1, yet fundamental challenges caused by introducing essential conductive components into the NMR sensitive volume remain. Cell designs in EC-NMR have largely been improved empirically, at times supported by magnetic field simulations.To propel systematic improvements of cell concepts, a workflow for a qualitative and semi-quantitative description of both B0 and B1 distortions is provided in this study. Three-dimensional Finite Element Method (FEM) simulations of both B0 and B1 fields were employed to investigate cell structures with electrodes oriented perpendicular to B0, which allow realistic EC-NMR measurements for battery as well as electrolysis applications. Particular attention is paid to field distributions in the immediate vicinity of electrodes, which is of prime interest for electrochemical processes. Using a cell with a small void outside the electrochemical active region, the relevance of design details and bubble formation is demonstrated. Moreover, B1 amplifications in coin cells provide an explanation for unexpectedly high sensitivity in previous EC-NMR studies, implying the potential for selective excitation of spins close to electrode surfaces. The correlation of this amplification effect with coin geometry is described by empirical expressions. The simulations were validated experimentally utilising frequency encoded 1H profile imaging and chemical shift imaging of 1H, 13C, and 23Na resonances of NaHCO3 electrolyte. Finally, the theoretical and experimental results are distilled into design guidelines for EC-NMR cells.

• B0_field_EchemCell: Replication data for figure 3 and A1.
• 'CSI_measurements' contains a .7z-archive with the NMR raw data of Chemical Shift Imaging (CSI) measurements acquired using the Bruker software TopSpin. Subfolders are named according the scheme: X_Y_Z
  X: Investigated Nucleus: either 1H, 13C or 23Na.
  Y: Experiment with or without Cu foil: either 'withCu' or 'withoutCu'
  Z: Notch under Cu foil filled with 'air' or 'electrolyte'.
• 'FEM_simulations' contains the results of B0 simulations in the form of histograms of B0 distortions relative to the bulk value that were calculated for all voxels in slices of 100 μm thickness in z-direction. The subfolders are named according the scheme: FEM_histograms_Y_Z
  Y: Experiment with or without Cu foil: either 'withCu' or 'withoutCu'
  Z: Notch under Cu foil filled with 'air' or 'water'.
• B1_field_EchemCell:< Replication data for figure 4./li>
  • '1H_profile' contains the NMR binary raw data of frequency encoded 1H profiling measurements acquired using the Bruker software TopSpin.
  • 'FEM_simulation' contains the results of three-dimensional B1 simulation of the electrochemical cell with a single Cu foil with 4 mm diameter and 50 µm thickness.
    hfieldxy_at-z0-1.dat represents the B1 field in the x-y plane at z = [0,1] mm for figure 4.b and 4.c.
    hfieldyz_at_x0.dat represents the B1 field in the y-z plane at x = 0 mm for figure 4.d.
• B1_field_CoinCell: Replication data for figure 5, 6, B1, B2 and B3.
• '1H_nutation' contains a .7z-archive with the NMR binary raw data of 1H nutation experiments acquired using the Bruker software TopSpin. Subfolders are named according the scheme X_Y_Z with thickness X in mm, distance Y in mm and coin material Z (PEEK or Cu).
• 'FEM_simulation' contains the results of three-dimensional B1 simulations of the coin cell setup with electrodes of 4 mm diameter.
  The subfolder 'hfieldy_at_x=0_z=0' contains the one-dimensional results with x = 0 mm and z = 0 mm with all investigated combinations of coin thickness and distance in the interval [0.05, 0.1, 0.5, 1, 2, 3, 4, 5].
  The subfolder 'hfieldyz_at_x=0' contains selected two-dimensional results with y = 0 mm with coins of (a) 1 mm distance and 1 mm thickness, (b) 0.1 mm distance and 1 mm thickness, (c) 1 mm distance and 5 mm thickness, (d) 0.1 mm distance and 5 mm thickness.
  In both folders, 'freespace.dat' represents the simulation without conductive Cu in the sample volume.
  The .dat-files are named according the scheme '2Coins_4dia_Xthick_Ydist.dat' with thickness X in mm and distance Y in mm.
• B1_field_CoinsExcitation: Replication data for figure C1.
  It contains the results of three-dimensional B1 simulations of the coin cell setup with electrodes of 3 mm diameter using the coins directly for RF excitation.
  The .dat-files are named according the scheme 'hyzdirect_3dia_Xthick_Ydist.dat' with thickness X in mm and distance Y in mm.