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Seeing inside lead-acid batteries using neutron imaging
J. M. Campillo-Robles, D. Goonetilleke, N. Sharma, D. Soler, U. Garbe, P. Türkyilmaz
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Causes of aging
- Electrode degradation: sulfating, corrosion, non-cohesion of active mass (shedding/degradation).
- Electrolyte degradation: stratification, water loss.
- Faulty manufacturing of cell: paste production, pasting, grid manufacturing, formation of the cell.
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Limitations of lead acid battery
≈ 35 Wh/kg
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What is happening inside?
We will try to see inside using neutrons
First time
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Gaston Planté (1834-1889)
1.- In operando monitoring.
2.- Neutron imaging techniques.
3.- Cell design.
4.- Results
5.- Conclusions
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1.- In operando monitoring
Monitoring of inner processes to optimize and improve the cell. A lot of sensors developed to check the SOC of the cell (using electrolyte concentration). Unfriendly environment: acid, electrical, small place.
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1.- In operando monitoring
Intrusive techniques: - Optic techniques: point measurement. - Equilibrium potential: point measurement.
Non-intrusive techniques:
- Electric potential of the cell. - Ultrasounds: line measurement. - Holographic Laser Interferometry (HLI): plane measurement. - Neutron Imaging
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2.- Neutron imaging techniques
Non-destructive testing for industrial/engineering applications. Advantages over other imaging techniques: - Neutron interaction only with the nucleus.
- Neutron pictures are related to the elemental composition of the object.
- Greater penetration than gamma rays.
Opaque to X rays.
Transparent to neutrons. Pb
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2.- Neutron imaging techniques
Different elements/compounds have different attenuation coefficients. Two mean attenuation processes: absorption and scattering.
scattering
absorption
transmission Neutron source Target Detector
collimator
Nuclear reactor Spallation source
2.- Neutron imaging techniques
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Two techniques: - Radiography (2D) Shadow image of the investigated sample. - Tomography (3D) Full three-dimensional image of the object is reconstructed from 2D pictures.
Already applied in energy storage:
Fuel cells, Lithium-Ion Batteries (LIBs), hydrogen storage, nuclear fuel, etc.
First time neutron imaging has been used for monitoring lead acid batteries!
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2.- Neutron imaging techniques: Dingo instrument
Open Pool Australian Lightwater (OPAL) Reactor
Fuel: 30 kg low enriched uranium
T = 60 °C 20 MW
13 neutron beam instruments
Opened in 2007
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2.- Neutron imaging techniques: Dingo instrument
Neutron radiography/tomography - Thermal neutrons (∼25 meV). - Detector:
CCD camera + scintillator. Measured area 20 × 20 cm.
- Spatial resolution: 27 µm. - Average flux at sample (n cm-2 s-1):
∼107 (centre of image) ∼ 7 × 106 (corner of image)
Opened in 2014
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3.- Cell design
Only one cell: 1.2 Ah.
Neutron friendly case Teflon (PTFE)
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3.- Cell design: electrodes
Dry charged commercial plates.
2 positive electrodes 3 negative electrodes
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3.- Cell design: separators
Commercial separators in positive plates (not in all cells). Polyethylene → hydrogen → high attenuation of the beam.
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3.- Cell design: electrical connections
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3.- Cell design: electrolyte
Deuterated electrolyte:
D2SO4 (Sigma-Aldrich) 96-98 wt. % in D2O, 99.5 atom % D.
D2O (Cambridge Isotope Laboratories) 99.9 atom % D.
Initial concentration (previous activation): 5 M.
4.- Results
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4.- Results: electrical behaviour
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C/3
C/3 C/4
Charge-discharge processes:
C/5 (0.182 A)
C/2 (0.38 A)
Problems at higher intensities!
4.- Results: attenuation
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Beer-Lambert law of attenuation of radiation valid for neutrons: 𝐼𝐼 = 𝐼𝐼0𝑒𝑒−𝜇𝜇𝜇𝜇. µ - linear attenuation coefficient of the target: µ = µabsorption + µ scattering . d - thickness of the sample.
Intensity reduction for different attenuation coefficients
4.- Results: attenuation
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Neutron linear attenuation coefficient, µ , for λ = 1.54 Å:
Less attenuation in concentrated electrolyte!!!
Data obtained from: NIST, Center for neutron research, https://www.ncnr.nist.gov/
ρ (g/cm3) µ (cm-1)
Pb (porous) 4.97 0.002
PbO2 (porous) 5.5 0.002
Pb (metal) 11.34 0.005 PbSO4 6.29 0.008
D2SO4 (liquid) 1.86 0.051
D2O (liquid) 1.107 0.137
4.- Results: open beam / as measured picture
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Cell without separators as measured
Open beam profile not homogeneous
not centred
4.- Results: as measured pictures
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Intensity profile as measured in air Electrodes
More attenuation at electrodes and separators
Cell with separators
Separators
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4.- Results: as measured pictures
Intensity profile as measured Electrodes
Separators cause measurement problems
Cell with separators
Separators
4.- Results: as measured pictures
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Intensity profile as measured
Electrodes
More attenuation at electrolyte than at electrodes
Cell without separators
4.- Results: corrections
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Corrections to be performed:
- Subtraction of noise (gamma rays). - Correction of open beam profile:
∼30 % reduction from maximum to minimum. - Correction of battery case.
- Fluctuations of reactor beam.
4.- Results: empty cell
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More than 70% of the neutrons pass through the cell
4.- Results: cell with electrodes
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The electrodes reduce the transmittance from 70% to 40%
4.- Results: electrolyte
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Final state after slow charging Final state after fast charging
4.- Results: neutron tomography
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Same principle as in X-R tomography. Only one difference: rotating sample. We can decide the cutting plane to analyse. Detailed inner structure.
Full image of the cell.
4.- Results: neutron tomography
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What can we see? - Inner structure of the electrodes (also through separators). - Active material behaviour. - Inner structural problems. - Sulfation of the electrodes. - Corrosion.
Grid
Active material
Separator
Electrode.
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5.- Conclusions
- Neutron imaging is complementary to other monitoring techniques. - Only technique with capability to see inside electrodes. - We can see changes in the electrolyte concentration. - Need to improve the experiment.
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We are working on …
- Optimization of cell design. - Quantification of electrolyte concentration. - Electrolyte stratification analysis. - Active material degradation analysis. - Transport properties of deuterated acid in heavy water.
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Thanks to …
Cell design: I. Urrutibeaskoa (MU), B. Turhan (YIGITAKU). Cell manufacturing: G. Arrizabalaga (MU), A. Arrillaga (MU), Parra Mekanizatuak. CAD drawing: E. Ruiz de Samaniego (MU), F. Zugasti (MU), I. Perez (MU). FEM simulations: X. Artetxe (MU), L. Oca (MU). Help at ANSTO: J. Pramudita (UNSW), N. Booth (ANSTO).
Data processing: F. Rossi (ANSTO), A. Velasco (ANSTO), J. Coslovich (ANSTO).
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Any question?
Aramaio valley (Basque Country)
Thank you! Eskerrik asko!