# Operando Dilatometry and GEIS Data for Symmetric Li|LLZO|Li, Na|NZSP|Na, and K|KBA|K Cells

## Dataset overview

This dataset contains time-aligned operando dilatometry and galvanostatic
electrochemical impedance spectroscopy (GEIS) data for symmetric Li|LLZO|Li,
Na|NZSP|Na, and K|KBA|K cells measured at current densities of 100 and
200 µA cm⁻² under an applied stack pressure of 0.07 MPa. It comprises six
experiments, corresponding to one measurement for each combination of cell
chemistry and current density.

Each experiment is represented by two files:

- `*_dilatometer_standardized_raw.csv`: standardized, unfiltered dilatometer data
- `*_GEIS_sanitized_raw.txt`: GEIS data with unchanged numerical measurement values and a sanitized metadata header

The filenames identify the cell chemistry and current density. Dilatometer
filenames additionally specify the instrument type (ECD3 or ECD4).

In the filenames, “raw” indicates that the numerical measurement values were
not filtered, averaged, resampled, interpolated, or baseline-corrected. The
files nevertheless underwent the structural and temporal standardization and
metadata sanitization described below.

## Relationship to the associated publications

The Li|LLZO|Li data are identical to the experimental data previously reported
by Schall et al. in *Small* 2025, 21, 2505053,
DOI: 10.1002/smll.202505053. No additional lithium measurements were performed
for the subsequent comparative study. The original lithium data were converted
to the standardized file format used in this dataset and analyzed together
with the sodium and potassium data.

The sodium and potassium data were obtained for the associated comparative
study "The Evolution of Pore Volume during
Stripping of Lithium, Sodium, and Potassium Metal Electrodes in Solid-State
Batteries" published in *ACS Electrochemistry*,
DOI: https://doi.org/10.1021/acselectrochem.6c00237.

## Dilatometer data

The standardized CSV files contain the following columns:

- `timestamp_utc`: ISO 8601 timestamp in UTC
- `timestamp_europe_berlin`: the corresponding timestamp in the Europe/Berlin time zone
- `unix_time_s`: Unix timestamp in seconds
- `time_from_geis_start_min`: elapsed time relative to the first GEIS data point, defined as 0 min
- `source_sample`: original sequential ECD3 measurement-point identifier; empty for ECD4 data
- `source_elapsed_time_s`: original ECD3 elapsed time in seconds; empty for ECD4 data
- `height_um`: measured height in µm

The Europe/Berlin timestamps correspond to the local timestamps recorded in
the GEIS files. Original ECD4 epoch timestamps were converted from milliseconds
to seconds.

For each experiment, the dilatometer data were restricted to the interval from
300 min before the first GEIS data point to 90 min after the last GEIS data
point. Measurement order and height values were retained. No filtering,
averaging, resampling, interpolation, or baseline correction was applied.

Some consecutive ECD3 records have identical absolute timestamps because of
the limited timestamp resolution of the original export. These timestamps were
not reconstructed or artificially distributed. The original record order and
the sequential ECD3 measurement-point identifiers (`source_sample`) were
retained.

## GEIS data

The GEIS measurement tables and numerical measurement values were retained
without modification. The metadata headers were sanitized by removing personal
information, local and network paths, network addresses, device serial numbers,
and empty or non-applicable sample metadata.

The GEIS timestamps remain in the Europe/Berlin local time used in the original
EC-Lab export.

## Instruments

ECD3 data were recorded using an EL-CELL ECD-3-nano at a nominal sampling rate
of 10 Hz.

ECD4 data were recorded using an EL-CELL ECD-4-nanocapa with a capaNCDT 6200
controller at a nominal sampling rate of 10.41666667 Hz. The instrument was
operated with a median-filter window width of 7 samples.

GEIS measurements were performed using a BioLogic SP-300 potentiostat.

## AI-assisted dataset preparation

Generative AI was used solely to assist with the development of processing
scripts and documentation for the data files provided in this dataset. All
processing steps, scripts, and exported files were reviewed and verified
against the source files by the dataset creator. This statement refers only
to the preparation of this dataset and not to the preparation of the
associated manuscripts or publications. Generative AI was not used to
generate, interpolate, or replace the recorded height or impedance values.

## Citation

Please cite this dataset using the citation information provided in the
JLUdata metadata record.