1. Differential Thermal Analysis Methods
Sources:
Eric Weisstein
The differential thermal analysis comprise four main and generally used techniques, as well as several specific tests and analyses.
The most widely used one is the differential thermal analyse (DTA). In DTA the temperature of the sample and of a reference is controlled according to a pre-selected program (usually linear rise with time). At some temperatures, due to the phase transitions or other temperature depending processes occurring in the sample, a temperature difference appears between the sample and the reference, and heat is exchanged between the sample and the system. These differences in temperature and heat flows are recorded and analysed. As a simpliest DTA device we can imagine a set of two thermocouples connected by a voltmeter. By DTA specific temperatures of phase transitions and the correponding heat evolution and absorption can be measured.
Differential Scanning Calorimetry (DSC) is a versatile and powerful technique to determine very precisely specific temperatures and specific heat flows associated with thermal transitions like phase transitions/changes, dehydration, gas evolution, melting, crystallization, etc. Heats of fusion and of reactions, Arrhenius parameters (Ea, k and n), oxidation stability etc. can be also determined. Direct measurement of heat capacity is possible. The weight of the sample is estimated preliminary and specific values are calculated.
By the Thermogravimetric Analysis (TGA) and DTGA the weight changes (losses) as a function of temperature in a controlled atmosphere are measured. The evolution of moisture or volatiles, the thermal stability and the phase composition of the sample can be estimated. As a rule TGA of the same material is performed simultaneously with DSC.
The Dynamic Mechanical Analysis (DMA) are used to determine the mechanical properties of the sample as a function of time, temperature, and frequency. Material properties like dimension changes as a function of temperature or force, stress / strain, stress relaxation, creep etc are determined easily by this method.

2. Differential Thermal Analysis Methods
Differential Thermal Analysis DTA
difference in temperature and heat flows between the sample and a reference.
temperature control program, qualitative analyses of thermal processes.
Differential Scanning Calorimetry (DSC)
temperatures and heat flows associated with thermal transitions.
phase transitions/changes, dehydration, gas evolution, melting, crystallization.
heats of fusion and of reactions, Arrhenius parameters (E, k and n).
oxidation stability, direct measurement of heat capacity.
Thermogravimetric Analysis (TGA) and DTGA
weight changes (losses) as a function of temperature under a controlled atmosphere.
moisture or volatiles, thermal stability and composition, simultaneous DSC / TGA.
The differential thermal analysis comprise four main and generally used techniques, as well as several specific tests and analyses.
The most widely used one is the differential thermal analyse (DTA). In DTA the temperature of the sample and of a reference is controlled according to a pre-selected program (usually linear rise with time). At some temperatures, due to the phase transitions or other temperature depending processes occurring in the sample, a temperature difference appears between the sample and the reference, and heat is exchanged between the sample and the system. These differences in temperature and heat flows are recorded and analysed. As a simpliest DTA device we can imagine a set of two thermocouples connected by a voltmeter. By DTA specific temperatures of phase transitions and the correponding heat evolution and absorption can be measured.
Differential Scanning Calorimetry (DSC) is a versatile and powerful technique to determine very precisely specific temperatures and specific heat flows associated with thermal transitions like phase transitions/changes, dehydration, gas evolution, melting, crystallization, etc. Heats of fusion and of reactions, Arrhenius parameters (Ea, k and n), oxidation stability etc. can be also determined. Direct measurement of heat capacity is possible. The weight of the sample is estimated preliminary and specific values are calculated.
By the Thermogravimetric Analysis (TGA) and DTGA the weight changes (losses) as a function of temperature in a controlled atmosphere are measured. The evolution of moisture or volatiles, the thermal stability and the phase composition of the sample can be estimated. As a rule TGA of the same material is performed simultaneously with DSC.
The Dynamic Mechanical Analysis (DMA) are used to determine the mechanical properties of the sample as a function of time, temperature, and frequency. Material properties like dimension changes as a function of temperature or force, stress / strain, stress relaxation, creep etc are determined easily by this method.
Dynamic Mechanical Analysis (DMA)
mechanical properties as a function of time, temperature, and frequency.
dimension change measurements as a function of temperature or force.
stress / strain, stress relaxation, creep.
Sources: Eric Weisstein,

3. Differential Thermal Analysis Methods
Differential Scanning Calorimetry (DSC)
time
Ttmper.
In this slide two schemes of DSC devices are shown which produce comparable data – Power compensated and Heat flux plate. They comprise two pans with volumes of some ml which are in contact to heaters and thermo sensors. The sample is colored in red, the empty pan is the reference. The sample weight is measured very precisely. The temperature program is a simple linear rise with time, the maximum temperatures can exceed 1200oC, and sample cooling is possible. Using high sweep rates a higher sensitivity but lower resolution is achieved, and vice versa. The specific heats of the occurring endothermic / exothermic processes or the changes in heat capacity can be determined for some mg of sample only. No special sample preparation is required, the sample can be a in a form of powder, granules, paste or a liquid. The sample pan can be hermetically closed during the test, or an inert, oxidative or reductive atmosphere can be ensured. A routine analysis takes only about 30 minutes.
Two designs of DSC instruments produce comparable data .
endothermic / exothermic processes or changes in heat capacity.
minimal sample amounts (liquids / solids), 30 min analysis, easy sample preparation.
wide range of temperatures, hermetically closed or in an atmosphere.
linear heating ramp, faster heating = higher sensitivity but lower resolution.
Source:

4. Differential Thermal Analysis Methods
Differential Scanning Calorimetry (DSC)
The two schemes of DSC devices produce comparable data – Power compensated and Heat flux plate. They comprise two pans with volumes of some ml which are in contact to heaters and thermo sensors. The sample is colored in red on the figure, the empty pan is the reference. The sample weight is measured precisely.
The temperature program is a simple linear rise with time, the maximum temperatures can exceed 1200oC and sample cooling is possible. Using high sweep rates, a higher sensitivity, but lower resolution is achieved and vice versa. The specific heats of the occurring endothermic/exothermic processes or the changes in heat capacity can be determined for some mg of sample only.
No special sample preparation is required, the sample can be in a form of powder, granules, paste or a liquid. The sample pan can be hermetically closed during the test, or an inert oxidative or reductive atmosphere can be ensured. A routine analysis takes only about 30 min.
In this slide two schemes of DSC devices are shown which produce comparable data – Power compensated and Heat flux plate. They comprise two pans with volumes of some ml which are in contact to heaters and thermo sensors. The sample is colored in red, the empty pan is the reference. The sample weight is measured very precisely. The temperature program is a simple linear rise with time, the maximum temperatures can exceed 1200oC, and sample cooling is possible. Using high sweep rates a higher sensitivity but lower resolution is achieved, and vice versa. The specific heats of the occurring endothermic / exothermic processes or the changes in heat capacity can be determined for some mg of sample only. No special sample preparation is required, the sample can be a in a form of powder, granules, paste or a liquid. The sample pan can be hermetically closed during the test, or an inert, oxidative or reductive atmosphere can be ensured. A routine analysis takes only about 30 minutes.
Source:

5. Differential Thermal Analysis Methods
Temperature modulated DSC (TMDSC)
The Temperature modulated DSC (TMDSC) is a modification of DSC.
A fast sinusoidal modulation is applied over the slower linear heating ramp. The modulation is of low amplitude (about one degree). The output signal is processed by FFT analysis. The slow linear sweep ensures a high resolution combined by the high sensitivity provided by the fast modulation.
The method is perfect for differentiation of overlapping transitions. It allows to separate heat capacity related (reversible - crystal melting) from kinetic (non-reversible – evaporation, decomposition) heat flows. Blends of two or more materials can be studied. The thermal conductivity of insulating materials can be determined.
By TMDSC determination of heat capacity along with changes in heat capacity during transitions is also possible.
A modification of DSC is the so called Temperature modulated DSC (TMDSC). Here a fast sinusoidal modulation is applied over the slower linear heating ramp. The modulation is of low amplitude (about one degree). The output signal is processed by FFT analysis. The slow linear sweep ensures a high resolution combined by the high sensitivity provided by the fast modulation. The method is perfect for differentiation of overlapping transitions. It allows to separate heat capacity related (reversible - crystal melting) from kinetic (non-reversible – evaporation, decomposition) heat flows. Blends of two or more materials can be studied. The thermal conductivity of insulating materials can be determined.
By TMDSC determination of heat capacity along with changes in heat capacity during transitions is also possible.
Source:

6. Differential Thermal Analysis Methods
Temperature modulated DSC (TMDSC)
time
Temper.
sinusoidal modulation over the linear heating ramp, differentiation of overlapping transitions
(fast) (slow) (FTA)
A modification of DSC is the so called Temperature modulated DSC (TMDSC). Here a fast sinusoidal modulation is applied over the slower linear heating ramp. The modulation is of low amplitude (about one degree). The output signal is processed by FFT analysis. The slow linear sweep ensures a high resolution combined by the high sensitivity provided by the fast modulation. The method is perfect for differentiation of overlapping transitions. It allows to separate heat capacity related (reversible - crystal melting) from kinetic (non-reversible – evaporation, decomposition) heat flows. Blends of two or more materials can be studied. The thermal conductivity of insulating materials can be determined.
By TMDSC determination of heat capacity along with changes in heat capacity during transitions is also possible.
separates heat capacity related (reversible - crystal melting) and kinetic (non-reversible – evaporation, decomposition) heat flows.
blends of two or more materials, determine thermal conductivity of insulating materials.
determination of heat capacity along with changes in heat capacity during transitions.
Source:

7. DSC curves for non cured and cured positive platesPb
dehydration
Let us now see some examples of DTA applied to battery materials. In this slide DSC curves (specific heat flows vs. temperature) for non cured and cured positive plates are shown. Four broad endothermic peaks are observed in the thermograms along with a sharp endothermic peak due to metallic lead melting at 327oC. The two overlapping peaks at oC are related to the dehydration of the paste, and the peaks at 360oC and above – to the destruction of lead hydrocarbonates. After curing the shape of the thermogram changes significantly. The amount of crystalline water and the type of its bonds are important for the properties of the paste.
200 – 300oC: dehydration
327oC: metalic Pb melting
360oC: hydrocarbonates
420oC: hydrocarbonates
410oC: hydrocarbonates
Source: G. Papazov, M. Matrakova, to be published

8. DSC curves for non cured and cured positive plates
Four broad endothermic peaks are observed in the thermograms along with a sharp endothermic peak due to metallic lead melting at 327oC.
The couple of overlapping peaks at oC are related to the dehydration of the paste and the peaks at 360oC and above – to the destruction of lead hydrocarbonates.
After curing, the shape of the thermogram changes significantly. The amount of crystalline water and the type of its bonds are important for the properties of the paste.
Let us now see some examples of DTA applied to battery materials. In this slide DSC curves (specific heat flows vs. temperature) for non cured and cured positive plates are shown. Four broad endothermic peaks are observed in the thermograms along with a sharp endothermic peak due to metallic lead melting at 327oC. The two overlapping peaks at oC are related to the dehydration of the paste, and the peaks at 360oC and above – to the destruction of lead hydrocarbonates. After curing the shape of the thermogram changes significantly. The amount of crystalline water and the type of its bonds are important for the properties of the paste.
Source: G. Papazov, M. Matrakova, to be published

9. CThermogravimetric (TGA) and DTGA analysis
non cured
TGA and DTG curves for a non cured positive plate
up to 200oC: moisture
270oC: dehydration
340oC: hydrocarbonate
370oC: hydrocarbonate
dehydration
cured
TGA and DTG curves for a cured positive plate
In this slide TGA (weight loss in % vs temperature) and DTG (rate of loosing weight vs. temperature) curves are shown. The samples are the same as for the above DSC curves (non cured and cured positive plates). Up to 200oC the moisture from the sample is evolved. The main weight loss is due to dehydration occurring at 270oC. Smaller weight losses are observed due to the destruction of hydrocarbonates at 340oC and 370oC.
up to 200oC: moisture
260oC: dehydration
340oC: hydrocarbonate
370oC: hydrocarbonate
dehydration
Source: G. Papazov, M. Matrakova, to be published

10. CThermogravimetric (TGA) and DTGA analysis
The presented curves correspond to TGA (weight loss in % vs temperature) and DTG (rate of loosing weight vs. temperature).
The samples are the same as for the above DSC curves (non cured and cured positive plates).
Up to 200oC the moisture from the sample is evolved.
The main weight loss is due to dehydration occurring at 270oC.
Smaller weight losses are observed due to the destruction of hydrocarbonates at 340oC and 370oC.
In this slide TGA (weight loss in % vs temperature) and DTG (rate of loosing weight vs. temperature) curves are shown. The samples are the same as for the above DSC curves (non cured and cured positive plates). Up to 200oC the moisture from the sample is evolved. The main weight loss is due to dehydration occurring at 270oC. Smaller weight losses are observed due to the destruction of hydrocarbonates at 340oC and 370oC.
Source: G. Papazov, M. Matrakova, to be published

11. TGA and DTG curves for a positive plate
TGA and DTG curves for a cured positive plate
260oC: dehydration
340oC: hydrocarbonate
380oC: hydrocarbonate
TGA and DTG curves for a formed positive plate
Here the TGA and DTG curves for a formed and for a cured positive plate are shown. The cured plate (containing 4PbO.PbSO4) looses weight due to dehydration at about 260oC and due to the destruction of hydrocarbonates at 340 and 380oC.
The curves for the formed positive plate (containing PbO2) are rather different. Weight losses due to dehydration are observed at 350, 510 and 570oC.
Up to 350oC: dehydration
510oC:
570oC:
Source: G. Papazov, M. Matrakova, to be published

12. TGA and DTG curves for a positive plate
The cured plate (containing 4PbO.PbSO4) looses weight due to dehydration at about 260oC and due to the destruction of hydrocarbonates at 340 and 380oC.
The curves for the positive plate after formation (containing PbO2) are rather different. Weight losses due to dehydration are observed at 350oC.
Here the TGA and DTG curves for a formed and for a cured positive plate are shown. The cured plate (containing 4PbO.PbSO4) looses weight due to dehydration at about 260oC and due to the destruction of hydrocarbonates at 340 and 380oC.
The curves for the formed positive plate (containing PbO2) are rather different. Weight losses due to dehydration are observed at 350, 510 and 570oC.
Source: G. Papazov, M. Matrakova, to be published

13. Thermograms of various PbO2 types obtained by DSC
DSC is a powerful method to investigate the phase composition and the properties of PbO2. In combination with XRD and SEM it provides unique information.
The thermal spectra of four PbO2 samples are shown on the next figure. The red curve is for chemical b-PbO2 (Merck), the black one for a mixture of b-PbO2 with few % of a-PbO2, and the green and the blue curves are for electrochemically prepared PbO2 – freshly prepared PAM (green) and PAM at the end of cycle life (blue).
Two exothermic peaks are observed on the figure at about 200 and 280oC. They are due to crystallization processes occurring in the partially hydrated zones of their particles. Amorphous PbO2 is observed mainly in electrochemically obtained PbO2.
Six endothermal peaks are observed at higher temperatures. First, between 300 and 400 oC chemically bound water contained in the PbO2 PAM particles is evolved. At temperatures above 400oC a-PbO2 and b-PbO2 are thermally decomposed to a variety of non stoichiometric lead oxides.

14. 8 1 7 6 5 4 3 2 Thermograms of various PbO2 types obtained by DSC
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peaks 3, 4 (endo) oC - PbO(OH)2  PbO2
Peaks 5, 6, (endo) oC - b-PbO2  PbOx (A)
Peaks 7, 8 (endo)- above 480oC - PbOx (A)  PbOx (B)

15. Thermograms of PbO2 samples from PAM sublayers (SGTP)
On the next figure thermal spectra of PbO2 PAM samples from a SGTP are shown. The samples are taken from one electrode at different distances from the current collector in the middle.
The area of Peak 6 which is related to b-PbO2 decomposition decreases slowly from the surface towards the current collector.
On the red curve for the sample in the AMCL a new hump is observed (in white). The shape of the curve changes completely in the corrosion layer what is an indication about phase composition changes.

16. 1 2 4 6 4A 4B Thermograms of PbO2 samples from PAM sublayers (SGTP)
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peak 4 (endo) oC - PbO(OH)2  PbO2
Peaks 6 (endo) oC - b-PbO2  PbOx (A)
Peaks 7, 8 (endo) - above 480oC - PbOx (A)  PbOx (B)
Peaks 4A, 4B (endo) - 385oC and 430oC - PbOx (C)  PbOx (D)

17. 1 2 4 6 DSC of PAM with declined capacity and after capacity recovery
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peak 4 (endo) oC - PbO(OH)2  PbO2
Peak 6 (endo) oC - b-PbO2  PbOx (A) 1 2 4 6
Source: B. Monahov, M. Matrakova, to be published

18. 4 10 9 6 TGA / DTG, PAM, before and after capacity recovery
Peak 4 (endo) oC - PbO(OH)2  PbO2
Peak 6 (endo) oC - b-PbO2  PbOx (A)
Peak 9 (endo) - 510oC - PbOx  Pb3O4 + a-PbOy
Peak 10 (endo) - 560oC - PbOx  Pb3O4 + a-PbOy
TGA / DTG, PAM, before and after capacity recovery 4 10 9 6
Source: B. Monahov, M. Matrakova, to be published

19. Battery knowledge contributed by thermal techniques
Fundamentals of the processes taking place in the plates during production and service life (phase transitions, hydration, dehydtration and their impact on battery performance).
Fundamentals of the processes taking place during the COC and of the processes related to battery thermal runaway.
Rate of temperature changes in the cell and temperature distribution along the plate during charge and discharge.
Dependence of battery temperature changes on cycle life.
Estimation of heating rate, thermal efficiency and thermal capacity of the battery / cell (or its components).
Thermal modeling of batteries in EV and stationary applications.
Based on the application of thermal management techniques following contribution to battery knowledge were developed:
1. Fundamentals of the processes taking place in the plates during production and service life (phase transitions, hydration, dehydtration and their impact on battery performance).
2. Fundamentals of the processes taking place during the COC and of the processes related to battery thermal runaway.
3. Rate of temperature changes in the cell and temperature distribution along the plate during charge and discharge.
4. Dependence of battery temperature changes on cycle life.
Estimation of heating rate, thermal efficiency and thermal capacity of the battery / cell (or its components).
5. Thermal modeling of batteries in EV and stationary applications.