HELENA

Detailed formulations, molecular structures, and measurement conditions of Li||Ce Coulombic Efficiency (CE) and Viscosity of lithium metal battery (LMB) electrolytes.

Collection	File	Configuration	Rows
CE measurements	LMB_HELENA_CE.csv	ce	1,000
CE molecules	LMB_HELENA_CE_Molecules.csv	ce_molecules	294
Viscosity measurements	LMB_HELENA_Viscosity.csv	viscosity	5,570
Viscosity molecules	LMB_HELENA_Viscosity_Molecules.csv	viscosity_molecules	271

Measurement tables

Both collections share these formulation and source fields:

Column	Description
Row_ID	Original record identifier. Viscosity IDs retain gaps from source selection.
Electrolyte	Human-readable electrolyte formulation.
Solvent_1 … Solvent_5	Up to five solvent, additive, or diluent components, encoded as SMILES:value.
Salt_1 … Salt_3	Up to three salt components, encoded as SMILES:value.
Method	CE protocol (Aurbach or Cycle), or the viscosity measurement-method description.
Reference	Source DOI; unpublished CE measurements use Rok_Private_Data.

In CE, component values retain the original molar amounts or ratios. In viscosity, component values are mole fractions summing to 1 across each formulation. Empty component cells indicate unused slots.

Coulombic efficiency

Column	Description / units
CE	Coulombic efficiency, %.
LCE	Original logarithmic target, −log10(1 − CE/100). It may differ from recomputation using rounded CE.
Current	Current density, mA cm⁻².
Capacity	Areal capacity, mAh cm⁻².
Cycle	Recorded cycle count; blank when unavailable.

The collection contains 616 Aurbach and 384 cycling records, with CE ranging from 72.00 to 99.82%.

Viscosity

Column	Description / units
Viscosity_mPa_s	Dynamic viscosity, mPa·s, numerically equal to cP.
Log10_Viscosity	log10(Viscosity_mPa_s).
Temperature	Temperature, °C.

Viscosity ranges from 0.348405 to 106,680 mPa·s, at temperatures from −85.094 to 120 °C. The source assigns 25 °C to 85 records reported at unspecified room temperature.

Molecule tables

Both molecule files use the same six columns:

Column	Description / units
Molecule	Molecule name or abbreviation.
Type	Solvent or Salt; ionic liquids are classified as Salt.
SMILES	Molecular structure string, including counterions for salts.
MW	Molar mass, g mol⁻¹.
Density	Reference density, g cm⁻³, when available.
mol/L	Reference neat-component molarity, when available.

The CE lookup retains name aliases and supplied physical properties; 15 missing molecular weights were calculated from SMILES with RDKit. The viscosity lookup contains one entry per structure, with calculated molecular weights and blank Density and mol/L fields.

Sources and release information

CE includes 979 literature records linked to 224 distinct DOIs and 21 unpublished records, Row_ID 624–644, labeled Rok_Private_Data. Viscosity measurements come from 346 distinct DOIs and extend the HELENA approach to viscosity prediction.

Both collections include related formulations and measurements from the same publications. Evaluation splits can group by publication and formulation to account for these relationships.

CE corrections · Source checks · File checksums

Citation and license

HELENA paper: Hierarchical Moiety Insights Drive Rational Design of High-Efficiency Lithium-Metal Electrolyte Formulations, accepted in Nature Energy. The publication DOI will be added when available.

@misc{HELENA,
  title = {HELENA},
  year = {2026},
  howpublished = {Hugging Face Datasets},
  url = {https://huggingface.co/datasets/JerrySuSuSu/HELENA}
}

Released under CC BY 4.0. Please cite the dataset and associated paper, retain source attribution, and indicate changes to redistributed versions. Machine-readable citation metadata are in CITATION.cff.