Modeling of Li-Ion-Batteries to Optimize the Results Gained by Neutron Imaging

Transcription

1 Modeling of Li-Ion-Batteries to Optimize the Results Gained by Neutron Imaging M.J. Mühlbauer Dr. A. Senyshyn, Dr. O. Dolotko, Prof. H. Ehrenberg SFB 595 Electrical Fatigue in Functional Materials Contact: Martin Mühlbauer SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer NIUS

2 Outline Basics about the type of Li-Ion batteries; the geometry of the electrodes inside the battery and the processes during charge and discharge Short introduction to neutron transmission measurements Modeling of Li-battery radiography data; expected reconstruction results for different wavelengths and the influence of the background caused by scattered neutrons Experimental data Outlook SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 2

3 Introduction Batteries Carbon (Graphite) Cobalt Lithium Oxygen Water free elektrolite Charging Discharging Type Diameter 18 mm Length 65 mm charging LiCoO 2 Li 1-x CoO 2 + xli + + xe discharging xli + + xe +C graphite charging discharging Li x C 6 Cathode Anode SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 3

4 Introduction Neutrons Neutron Attenuation is caused by: neutrons Absorption, σ a Incoherent scattering, σ inc Coherent scattering, σ coh sample detector SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 4

5 Calculated Neutron Radiographies Step 1 The main parameters of the battery geometry are entered at first: Center pin/area Stack of rolled foils Gab between foils and container (optional) Container Outer foils SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 5

6 Calculated Neutron Radiographies Step 2 LiCoO 2 graphite Al Cu LiCoO 2 graphite electrolyte/ separator electrolyte/ separator SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 6

7 Calculated Neutron Radiographies Step 3 Parameters for the output: Width Height Position of the sample Pixel size neutrons sample detector 0 Distance, pixel SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 7

8 Output Files Attenuation due to neutron scattering Attenuation cased by neutron absorption Total Attenuation Transmission (All files have been calculated using a pixel size of 10µm.) SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 8

9 Adding an Image Blur Line profile Gaussian Blur 200 µm Line profile SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 9

10 Calculated Radiographs for various Neutron Wavelengths 0.5 Å 9.0 Å mean wavelength 2.3 Å SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 10

11 transmission Beam Hardening Transmission Profile position, pixel SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 11

12 Reconstruction Results 0.5 Å 1.0 Å 1.5 Å 2.0 Å 2.5 Å 3.0 Å 3.5 Å 4.0 Å 4.5 Å 5.0 Å 5.5 Å 6.0 Å 6.5 Å 7.0 Å 7.5 Å 8.0 Å 8.5 Å 9.0 Å SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 12

13 Radial Profiles for different wavelengths (I) 1.0 Å 2.0 Å 3.0 Å 4.0 Å SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 13

14 Radial Profiles for different wavelengths (II) 5.0 Å 6.0 Å 7.0 Å 8.0 Å SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 14

15 Y Axis Title Radial Profiles for different wavelengths (III) p0AA 4p0AA 6p0AA 8p0AA attenuation, cm radial position, mm X Axis Title SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 15

16 Minimum Transmission Threshold 2,0 1,5 attenuation, cm -1 transmission meanwofoil meanwithfoil mean transmission for center of battery meanwith meanwo 0,1 1,0 0,5 0,01 0, E-3 10 neutron wavelength, Å wavelength, Å SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 16

17 Comparison with Measured Profile attenuation, cm -1 radial position, cm SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 17

18 Contribution of Scattered Neutrons Scattered intensity is overestimated here! SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 18

19 Reconstruction Including Scattered Intensity SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 19

20 Short Summary The neutron wavelength should be shorter than 3Å to 4Å for batteries of the type. Neutrons of larger wavelengths do not yield a significant transmission at the centre of the battery. They only cause beam hardening artefacts and contribute to activation of the battery. Conclusion: Use thermal neutrons instead of cold neutrons! Use monochromatic neutrons if possible! SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 20

21 Tomography setup at ANTARES Neutron Source Collimator Flight Tube Sample Position Detector 16 m Beam geometry and flux L/D 400: 1.0 * 10 8 n /cm 2 /s L/D 800: 2.6 * 10 6 n /cm 2 /s Detector field of view 100 mm x 100 mm pixel size 48 µm SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 21

22 Tomography at SPODI - µtos 2.0 Beam geometry and flux: L/D approximately n /cm 2 /s wave length Å Detector: FOV 45mm x 29mm pixel size 57 µm SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 22

23 Comparison of the Reconstructed Data Polychromatic neutrons Monochromatic neutrons SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 23

24 Final Conclusions Modelling neutron radiography helps to optimize the neutron energy spectrum to yield best contrast during the final reconstruction step. Simple calculations are sufficient enough to get an idea of the expected results and are much less time consuming than complex Monte Carlo models of the sample SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 24

25 Outlook Future facilities at pulsed neutron sources, e.g. the ESS, will enable to acquire radiographs at different wavelengths quasi simultaneously. This will offer new options for data treatment, like contrast enhancement making use of Bragg edges. A combination of diffraction and imaging is feasible. But it is only reasonable if the measurements can really be carried in parallel, i.e. on the same time scale SFB 595 TU-Darmstadt / KIT M.J. Mühlbauer 25