in-operando high-speed tomography of lithium-ion batteries during thermal runaway

Preventing and relieving fever from being out of control is one of the biggest challenges faced by lithium\'s safe operationion batteries.
Here, we demonstrated high for the first time-
Synchronous Accelerator X
Ray Computed Tomography and radiography combine thermal imaging to track the evolution of internal structural damage and thermal behavior during the initiation and propagation of lithium thermal runawayion batteries.
This diagnostic method is suitable for commercial lithium-ion batteries (
LG 18650 NMC battery)
, In-depth understanding of key degradation modes including gas
Induced stratification, electrode layer collapse and propagation of structural degradation.
It is envisaged that the use of these technologies will lead to Li-
Ion batteries and their safety properties.
Use 76-in the ID15A beam line of ESRF-
Kevin monochrome beam with pixel resolution of 10. 87u2009μm.
The camera detector records Ray photos at a speed of 1,250 Mbps;
Take the fault map at the speed of 2. 5 and 1.
25 hz, consisting of 500 and 1,000 projections, respectively.
A fault map with a smaller number of projections was taken at a higher speed, but significantly sacrificed the image quality.
In the case of almost no movement inside the battery, higher image quality and lower frequency are preferred. The 2. 5-and 1. 25-
Hz tomography projection is performed at an angle increment of 0 in a 360 ° rotation of the cell. 72° and 0.
36 degrees respectively.
The field of view of the monochrome beam is 10. 5u2009mm × 7.
6 u2009 mm, half of the cells were captured in the ray photos.
The transmitted image is reconstructed to 7. 6-mm-
High 3D cylindrical sections of cells using standard reconstruction methods. The set-
The up presented in Provides real-
Time tomography, thermal and electrochemical analysis during electrical and thermal abuse testing extends dynamic fault analysis of commercial batteries to include internal structural features.
Imaging experiments were performed using 76-
Kevin monochrome beam with a view of 10. 5u2009mm × 7. 6u2009mm.
The exposure time is set to 0.
35 Sims ms and high-
The speed camera for imaging is PCO Dimax (PCO, Germany)
, Achieved 1,250 fps.
Area of interest of 960 × 700 pixels (
Horizontal x vertical)was used.
A fault map consisting of 500 projections with a resolution of 10.
Capture 87 μm every 0 times.
Rotate at 360 ° and at °. p. m.
A fault map consisting of 1,000 projections with a resolution of 10.
Capture 87 μm every 0 times.
Rotate 8 ° s at 360 ° r at 75 ° r. p. m.
To achieve the desired frequency of tomography, the image is stored on the PCO Dimax camera, which has a 36gb open time
Board memory for fast intermediate storage where 17 seconds of recording can be stored.
The post event trigger function is implemented, and the detector records continuously before triggering. At this time, it will store the previous 17 u2009 s high. Velocity fault map. During high-
The velocity fault scan, the sample rotates continuously through 360 °.
The standard reconstruction method is used to reconstruct the transmitted image in 3D and save it as a 32-bit floating point file.
Use Avizo Fire 7 (VSG, France)
, Where the 3D image is displayed as a stack of 2D image slices.
A kind of edge protection
While preserving the detail features and edge sharpness of the image, local mean filtering is performed on the image to remove noise.
Material stage defined by Gray
Scale the values and selectively display them using Avizo\'s split editor.
X-ray film was developed using MATLAB r203a.
Flat field correction is applied to the original Ray photos to remove artifacts and gray-scale image contrast is enhanced using MATLAB\'s \"adaptive. There is still enough oxygen in the air to allow the heat of the cell contents to get out of control
A uniform layer of heat
Resistant to black paint (
The specific radiation rate of calibration is 0.
96 in the range of 40-180 °c)
Apply to each battery before testing.
The battery is tightly secured between the fastening screw and the wall of the sample holder, and is placed in a position where the area of interest is consistent with the beam.
Heat with a hot gun (
German stannel HG 2310 LCD electronics)
Located next to the battery, the battery has 9-
Mm reduces the nozzle to concentrate heat on the surface of the battery, protects the adjacent equipment, and helps to prevent the weekly non-uniformity of the temperature.
Reducing the size of the nozzle causes spots.
The surface diameter of the rotating battery is 10mm.
The heat gun uses Duratherm heating elements to achieve accurate control of applied temperature by changing the air flow rate and air temperature in a 10 °c increment.
Record the temperature of the battery using a hot camera (
Croissy-FLIR Systems, France
Fort France)
, From the opposite to the hot gun as shown in the figure.
The thermal camera was calibrated in the temperature range of 15 ° c-250 ° c and 250 ° c-1,500 ° c;
In order to ensure accurate temperature measurement within the expected temperature range, the previous temperature range was applied.
The thermal camera has an extended wavelength detector that can detect infrared
Red wavelength between 2. 5 and 7u2009μm.
The noise equivalent temperature difference of the camera in the calibration range is less than 20 mk.
The image is recorded at a speed of 25 hz and the temperature measurement accuracy specified by the manufacturer is ± 1 °c or ± 1%.
Two businesses 18650 Li (NMC)batteries (LG 2.
2 Ah NMC and LG 2. 6 Ah NMC)
High temperature (. 250u2009°C)
Using a hot gun, the hot gun is activated when the battery starts to spin.
Under the maximum airflow, the hot gun is set to a temperature of 480 °c, and the reduction nozzle of the hot gun is carefully placed 2 cm from the battery to avoid the difference in heating between tests.
Continuous rotation helps to maintain a uniform distribution of ambient temperature around the battery.
The heating continues until the heat is out of control.
The PCO Dimax camera stores 17 s at 1,250 fps under previously outlined conditions. The post-
Event trigger for recording image is activated.
After the catastrophic consequences of heat runaway (
(Explosion or violence).
This led. 15u2009s of high-
Frequency tomography of events and previously captured.
The fault map 2 u2009 s taken after the incident.