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Purpose Dataset of half-cell Open Circuit Voltage (OCV) measurements from several lithium-ion battery active materials. The dataset was created to compare OCVs measured with pseudo-OCV protocols vs measured with Galvanostatic Intermittent Titration Technique (GITT). While the primary outcome of the dataset is to highlight the differences between measurement protocols, the OCVs will also support a variety of electrochemical methods and analyses that rely on half-cell measurements. As examples, half cell OCVs can be used to: Balance electrodes before assembling cells. Balancing with half cell OCVs ensures that for a given N/P ratio, the half cell OCVs of both electrodes align into a safe operating full cell voltage range, where no electrode is exposed to deleterious half-cell voltages (e.g. avoid lithium plating). Deconvolute a full-cell differential curve into individual electrode contributions. These contributions can be tracked during cycling to quantify degradation modes (LLI, LAM) as the cell ages. Parametrize electrochemical models. Physics-based and equivalent circuit frameworks require accurate half-cell OCVs of each electrode to compute the full cell OCV. Scope The dataset consists of 95 tabular files with electrochemical time series of the half-cell OCV measurements, and a metadata file with descriptions of each cell and measurement. The experimental design aimed at obtaining two identical measurements per unique combination of electrode batch (12) and measurement protocol (4), amounting to 2*12*4 = 96 measurements. All cycling protocols targeted 5 cycles. Failed cells were replaced with new ones when possible. File Name convention Each dataset was named with the following convention: "dataOwner__manufacturer-chemistry-factor-batchID-6characterID__TestStart__Test__Conditions.bdf.parquet" Dataset Schema 95 tabular files serialized in the Apache Parquet format. Column label Data Type Units Description Test Time / s float s Elapsed time since the start of the test Unix Time / s float s Timestamp in Unix time format (seconds since 1970-01-01 UTC) Current / A float A Instantaneous current Voltage / V float V Instantaneous voltage Cumulative Capacity / Ah float Ah Total capacity accumulated over a half cycle Cycle Count / 1 integer Monotonically increasing index of test cycles Step Index / 1 integer Index indicating the instantaneous step type within the measurement protocol (e.g. constant current, rest, etc.) Metadata Schema One tabular file serialized in CSV format. Name Data type Units Description BDF name string File name of the electrochemical time series, following the conventions of the BDF format. Active material type string Label representing the chemical composition of the active material. Start Date YYYYMMDD integer Start date of the test as integer in YYYYMMDD format Public label string Label identifying the electrode (chemical composition and manufacturing route), used in the research publication. Cycling Programme name string Label identifying the cycling program. Mass of Active Material / mg float mg Mass of Active Material in the electrode Weight percentage of Active Material / % float % Weight percentage of Active Material in the electrode Theoretical Capacity / mAh g-1 float mAh g-1 Theoretical specific capacity of the active material. Electrode Diameter / cm float cm Diameter of the coin-shaped electrode. Dry Thickness / um integer um Thickness of the electrode after drying Nominal Areal Capacity / mAh cm-2 float mAh cm-2 Areal capacity of electrode. For custom made electrodes, calculated as the product of the electrode loading (g cm-2) and theoretical specific capacity (mAh g-1). For commercial electrodes, values provided by manufacturer. Electrode Loading / g cm-2 float g cm-2 Mass of active material per electrode area, calculated for custom made electrodes. Electrode batches The "Public label" column in metadata.csv describes the chemical composition and manufacturing route of each electrode batch. Each electrode is cycled between voltage cutoffs: Public Label Active Material Voltage Cutoffs / V Gr-AQ-1 Graphite (aqueous processed) 1.00 - 0.01 Si-AQ-1 Silicon (aqueous processed) 1.00 - 0.01 SiGr-AQ-1 Lower Si % Silicon-Graphite composite (aqueous processed) 1.00 - 0.01 SiGr-AQ-2 Higher Si % Silicon-Graphite composite (aqueous processed) 1.00 - 0.01 SiGr-AQ-3 Higher Si % Silicon-Graphite composite (aqueous processed) 1.00 - 0.01 LNMO-AQ-1 LiNi0.5Mn1.5O4 (aqueous processed) 3.50 - 4.80 LNMO-NMP-1 LiNi0.5Mn1.5O4 (organic solvent processed) 3.50 - 4.80 LNMO-AQ-2 LiNi0.5Mn1.5O4 (aqueous processed) 3.50 - 4.80 LNMO-NMP-2 LiNi0.5Mn1.5O4 (organic solvent processed) 3.50 - 4.80 LFP-NMP-1 LiFePO4 (commercial electrode) 2.50 - 3.65 NMC111-NMP-1 LiNi0.33Mn0.33Co0.33O2 (commercial electrode) 3.00 - 4.30 NMC532-NMP-1 LiNi0.5Mn0.3Co0.2O2 (commercial electrode) 3.00 - 4.30 Cycling Programmes The "Cycling Programme name" column in metadata.csvdescribes the electrochemical protocols to determine the half-cell OCV of active materials. All protocols were set to run for 5 cycles and at room temperature. Cycling Programme name Description p-OCV Constant current cycling at C/50. A rest period of 8 h is applied upon reaching the upper and lower voltage cutoffs. p-OCV hold Constant current cycling at C/50. The voltage as held for 6 h under potentiostatic control upon reaching the upper and lower voltage cutoffs. GITT Sequence of current pulses (C/50) followed by a period of rest (150 minutes). A rest period of 6 h is applied upon reaching the upper and lower voltage cutoffs. GITT hold Sequence of current pulses (C/50) followed by a period of rest (150 minutes). The voltage as held for 6 h under potentiostatic control upon reaching the upper and lower voltage cutoffs. Usage Notes Data processing The electrochemical time series have been processed from their original format to the Battery Data Format (BDF) promoted by the Battery Data Alliance (Linux Foundation). Processing into BDF involved simple transformations of dates format, units and column labels. No additional cleaning or imputation has been performed. The datasets are compressed in Apache parquet format from their original size, and readily usable with traditional Python data analysis packages such as Pandas and Polars. Materials OCVs from Si-containing electrodes might exhibit large variations depending on material properties, such as particle size, crystallinity, surface chemistry, percentage of silicon in Si-Graphite blends, etc. None of these material and electrode properties are available from the suppliers. Therefore these OCVs in the dataset should not be considered as representative for all Si-containing electrodes. The OCVs from LiNi0.5Mn1.5O4 (LNMO) electrodes vary depending on the degree of Mn/Ni disorder (see Sun et al.). The LNMO material used in this study targeted high Mn/Ni disorder, therefore the OCVs is a highly disordered spinel Unavailable metadata Electrodes that were not manufactured in the lab but instead supplied by vendors (LFP. NMC111, NMC532) lack metadata on the weight percentage of active material, needed to calculate specific capacities. Instead, commercial electrodes only report nominal areal capacities, which are provided as part of the metadata.csv file. Known issues All electrochemical time series were plotted to visually inspect for prominent issues during cycling. Cells that were completely unable to cycle were replaced with new measurements when possible. Cells that failed after few cycles or exhibited anomalies were kept in the published dataset; below we list the known issues, also described in the "Knwon Issues" column in metadata.csv: File Name Known Issues sintef__sintef-lnmo-R2032-intelligent1-b3d963__20250424__gitt__RT.bdf Cell failed at end of 3rd cycle sintef__sintef-lnmo-R2032-intelligent1-ee5c27__20250625__gitt__RT.bdf Cell failed at the end of 1st cycle sintef__sintef-lnmo-R2032-intelligent1-f46602__20250625__gitthold__RT.bdf Cell failed during the 2nd cycle sintef__sintef-lnmo-R2032-intelligent2-dd8a76__20250424__gitthold__RT.bdf Anomalously high voltage measurements during the pulse step sintef__sintef-lnmo-R2032-intelligent2-e5b4f3__20250424__gitthold__RT.bdf Anomalously high voltage measurements during the pulse step sintef__sintef-lnmo-R2032-intelligent2-fa5db1__20250424__gitt__RT.bdf Anomalously high voltage measurements during the pulse step sintef__sintef-nmc111-R2032-customcells-000b13__20250720__gitthold__RT.bdf Cycling stopped unexpectedly during cycle 4 sintef__sintef-nmc111-R2032-customcells-85cad7__20250720__gitt__RT.bdf Anomalously high voltage measurements during the pulse step. Cycling stopped unexpectedly during cycle 2 sintef__sintef-nmc111-R2032-customcells-e5a00e__20251015__gitthold__RT.bdf Cycling stopped unexpectedly during cycle 4 sintef__sintef-nmc532-R2032-gelon-1765db__20250706__gitt__RT.bdf Anomalously high voltage measurements during the pulse step sintef__sintef-silicongraphite-R2032-intelligent1-175ef2__20250514__gitt__RT.bdf Anomalously high voltage measurements during the pulse step