Differential Scanning Calorimeter (DSC) of Batteries
Differential Scanning Calorimetry (DSC) is a technique used to measure changes in material heat generation as a function of time and temperature. These heat changes are often associated with reactions or transitions in materials.
The DSC is used primarily to determine glass transition temperatures, melting and boiling points, heat of fusion and specific heat. This data can be used directly in process optimization and in kinetic studies of reactive chemicals, to predict product performance and chemical degradation characteristics.
The data measurements from the equipment provide quantitative and qualitative information about physical and chemical changes that involve exothermic or endothermic processes, or changes in heat capacity. DSC test provides
- Onset temperature
- Heat flow rate
- Heat of melt
- Latent heat of evaporation
- Melting/boiling temperature
- Enthalpy of endotherm
- Enthalpy of exotherm
In battery research and safety testing, DSC is used to evaluate the thermal stability and reaction energetics of individual components such as:
- Electrolytes – solvent decomposition, salt stability.
- Electrodes (anode/cathode materials) – exothermic decomposition, SEI (solid electrolyte interphase) stability.
- Separators – melting or shrinkage temperatures.
- Binder and additives – degradation profiles.
This information helps predict the onset of thermal runaway and the relative safety of battery chemistries under abuse conditions.
Standards / References:
ASTM E537 “Standard Test Method for the Thermal Stability of Chemicals by Differential Scanning Calorimetry”
Equipment used:
- DSC 204 F1 Phoenix (Differential Scanning Calorimeter manufactured by Netzsch™ Group of Selb, Germany)
- DSC 2910 Modulated by TA Instrument
- High pressure sample crucible
DSC
High pressure sample crucible
Test details:
Different techniques are employed depending on whether an open or closed test is desired. For closed tests, approximately 5-20 mg of the reaction mixture is introduced into a high-pressure stainless-steel crucible (110 bar), material of construction could be titanium and stainless-steel, All the battery material samples are prepared under argon environment. The cell is placed into the instrument alongside an empty reference crucible. Temperature vs. time is recorded for both systems. Temperature differences between them indicate exotherm or endothermic behavior.
The DSC most frequently operates in a scanning mode, ranging from 1-20 °C/min. Operator skill ensures proper calibration. The instrument is fully automated; once operating, it needs minimal to no operator intervention. Various atmospheres can be imposed during open tests.
Some details on the DSC include:
- Test cell material options include aluminum (open), stainless steel, and gold plated
- Operating test cell temperature range: room temperature to 500°C
- Temperature Accuracy: +/-0.1°C
- Scanning operating mode: ranging from 1-20 °C/min (10 °C/min)
- Operating test cell pressure range: 0 to 110 bar
- Sample size: 10 mg standard
- Data recorded is generally in heat flow (W/g) vs. temperature (°C)
Example Test:
Graphite and graphite fiber anode samples recovered from multiple coin cell at fully charged state were tested in a high-pressure crucible. Scan heat mode of 10 °C/min were used. The test results of DSC tests are summarized in Table and comparative plots are shown in figure. Test results indicate that both the samples had three exothermic reactions between 100°C and 400C. First exotherm was of interest for this study and results are summarized in table.
Table 1: DSC Test Results of Lithiated Anode Sample
| Parameter | Description | Results | |
|---|---|---|---|
| Lithiated Graphite | Lithiated Graphite Fiber | ||
| To | Onset temperature of enthalpy change, °C | 110 | 112 |
| Tp | Peak temperature, °C | 133 | 135 |
| Te | Peak end temperature, °C | 152 | 160 |
| ΔE | Change in enthalpy, J/g | 136 | 292 |
DSC Test Results of Lithiated Anode Sample
Comparative DSC Plot of two Lithiated Anode Samples
FAQ:
1. What are the key insights from DSC for batteries?
- Exothermic decomposition temperature → onset of material breakdown.
- Endothermic events → separator melting, phase changes.
- Heat release (ΔH) → total energy that could accelerate thermal runaway.
- Compatibility of components → interaction between electrolyte and electrode materials.
2. What are the applications of DSC in Battery Testing?
- Safety Evaluation: Identifies critical temperatures where hazardous reactions begin.
- Material Screening: Compares thermal stability of new electrolytes, binders, separator materials, anode and cathode material as a raw material as well as charged state
- Failure Analysis: Studies degraded cells to understand reaction pathways.
- R&D: Guides formulation of safer battery chemistries.
3. What are the advantages of DSC for Battery Studies?
- Requires small size (mg level) → safe and efficient.
- Provides precise onset temperatures for decomposition.
- Can distinguish endothermic vs. exothermic processes, critical in runaway analysis.
- Often used in combination with ARC (Accelerating Rate Calorimetry) or TGA (Thermogravimetric Analysis) for a full safety profile.
For Example: In Li-ion batteries, DSC can detect when the SEI on the graphite anode decomposes (~80–120 °C), electrolyte breakdown (~150–200 °C), and cathode oxygen release (130-200 °C). These reactions are precursors to thermal runaway.
4. How does DSC differ from TGA (Thermogravimetric Analysis)?
DSC measures heat flow associated with transitions, while TGA measures weight changes with temperature (e.g., due to evaporation or decomposition).