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Photon Counting X-ray Detectors for

Battery Inspection

X-ray for Batteries

New Generation Batteries, New Challenges

The advanced technology of Direct Conversion photon counting X-ray detectors ensure battery safety compliance with quality requirements at final assembly and test.

Small Batteries

      

Fig 1a                                                                         Fig 1b
Fig 1a  Section cut from a volume CT inspection of a stacked battery
Fig 1b  A slice from the CT volume with details of the anode-cathode edges in the section

Small, high performance batteries are required for sophisticated new devices, such as the latest smartphones and laptops. As they are so small, these batteries have been designed using ultra-thin, alternating layers of cathode, electrolyte and anode, with insulating separators to prevent short circuits. Typically, there are 20 – 50 layers in these batteries, which are used for communications, IT and smart devices (compared to 200 – 250 layers for batteries required for electric vehicles (EVs) – see below). A wide variety of materials are incorporated into the layers – for example, AL-Cathode-Separator- Anode-Cu –  with layer thicknesses of between 10 – 150 μm.

A minimum space between anode and cathode at the ends of these layers is essential to prevent a shortage between the two polarities. However, it is here, at the end, and particularly at the corners, where damage, from crushing for example, is highly likely to occur.  It is challenging to check this level of fine detail, but our powerful, direct conversion X-ray detectors can capture these tiny defects and ensure quality compliance at final assembly and test.

Car Batteries and the Electric Vehicle (EV) Market

Direct Conversion X-ray detectors provide high-speed inspection for advanced battery technology

Direct Conversion, the innovators behind photon counting X-ray detectors, were fast to identify the emerging issues facing the battery industry. Despite the extreme pressures of Covid, global sales of EVs surged by 40 % in 2020, and sales of EVs in 2021 in the UK, for example, exceeded the combined sales of the previous five years.

Staying ahead of this constantly changing field of technology, Direct Conversion has worked closely with battery manufacturers to provide X-ray detectors for rapid battery inspection as production is ramped up.

As the market for EVs has grown, manufacturers have applied themselves to making the vehicles easier to use. EVs are being designed to travel further between charges and to have ultra-fast charging mechanisms, all of which present challenges for the battery manufacturers. Meanwhile, new approaches to battery waste disposal are on their way, and there are exciting practices emerging for battery re-use, and extension to battery life. Direct Conversion is collaborating with the experts in battery production and exploiting the versatility of its X-ray detectors for the battery inspection requirements that come with innovation and adaptation.

2D Inspection

In-line scanning using a DC-TDI X-ray detector delivers rapid inspection of stacked batteries

DC-TDI X-ray Detector for 2D Inspection

Benefits

*Rapid scanning

*Up to 100 % of all relevant parts

*Implemented into in-line manufacturing processes

 

 Fig 2a                                                                                    Fig 2b
Fig 2a  TDI-scan Imaging with DC-TDI200 (200 mm/ 60 lines) Automotive Stacked Battery
The image shows a minimized parallax effect due to programmable pixel-lines
Fig 2b  TDI-scan Imaging with DC-TDI100 (100 mm/ 60 lines) Smartphone L-shaped Stacked Battery (un-pouched)
The image demonstrates challenges in 2D-imaging due to layer variability
Note: 2D-imaging has restrictions for precise quantitative measurement due to object overlaps and limited geometrical alignment in 2D-technique (no z-depths information)

  

Fig 3                                                                            Fig 4
Fig 3 Showing an image of the winding battery in a vertical position. Half of the battery is imaged. (DC-TDI350)
Fig 4  DC-TDI-scan Imaging with DC-TDI200 (200 mm/ 60 lines) Automotive Stacked Battery

The DC-TDI detector provides fast pre-scan during the in-line inspection of stacked batteries, highlighting any significant anomalies. Using this method, malfunctions which may be causing defects in, for example, the anode-cathode offsets, are quickly identified.

This 2D method reduces the parallax effect of stacked layers to the minimum possible level when the scanning direction is at a 90 degree angle to the anode/ cathode layers because every layer is vertical to the line scanner. The number of lines is optimised to image the layer structure to gain both thickness and distance information.

Our DC-TDI photon counting detectors are modular and flexible, accommodating the variable settings for the number of pixel lines required. The DC-TDI line scan setup can inspect very thin (<100 μm) stacked layers with a minimum of parallax effects, irrespective of the number of layers.

A typical scenario would combine a DC-TDI100 or DC-TDI200 detector (depending on the size of the battery) with fast scanning, together with a microfocus tube (15 – 40 μm spot size).

Note: this is one scenario and implementations vary depending on the specific application. The energy level and power of the tube are key factors in determining the speed – as well as the imaging capabilities – of the detector. Energy levels up to 160 kV, with X-ray power of 75 W – 200 W, and a detector set-up housing 0.75 mm CdTe conversion material would be a typical combination.

2D Inspection for Cylindrical Batteries

  

        Fig 3a                                    Fig 3b                                                    Fig 3c
Fig 6a  2D scan of cylindrical batteries of the type used in the automotive sector
Fig 6b  2D scan of upper portion of cylindrical battery
Fig 6c  2D scan of lower portion of cylindrical battery

Tesla, the world’s largest EV car manufacturer, was the first to use cylindrical batteries in its cars in 2008, and the market for these batteries has expanded dramatically, with more EVs in production, as well as a wide range of other types of EV hitting the road, such as e-scooters, e-bikes, light electrical vehicles (LEVs) and delivery and truck EVs.  As demand grows so do the challenges for existing inspection systems.

Our 2D X-ray inspection approach with automated parts handling, optimised for the correct rotation angle, provides a good solution.

CT Inspection

XC-Thor X-ray Detector for CT Imaging

Highly Sensitive Imaging for Volume Data

CT imaging enables specific slice positions to be extracted to provide exact quantitive offset measurements of stacked batteries.

Fig 10                                                                                Fig 11

Fig 12                                                                                 Fig 13
Fig 10 and Fig 12 show slices taken out of this volume and here the specifics of the anode-cathode edges are clearly visible
Fig 11 shows an image of the battery corner
Fig 13 shows a CT-volume section of one battery corner area
CT Imaging Scenario

When using CT imaging for small components such as smartphone batteries, a typical solution would be a fast XC-Thor with a 512 line setup, so an XC-Thor.10G (100 x 50 mm) detector. (Larger, automotive batteries would need an XC-Thor FX20 because it has a larger active area of 200 x 50 mm).

In the diagram below, the inspection set up must enable the measurement of the distance between anode and cathode. A typical scenario CT inspection would be used to image and locate the battery corners where a slice can be cut from the full volume to enable specific measurements to be taken.The process requires the battery to be tilted at specific angles so that the battery corners can be inspected.

An example of an implementation of a typical off-line CT battery corner inspection system: 

CT scan setup with source, robotic battery handler and detector

Speed

Super Fast CT with XC-Thor.10G

Inspection speed is an important criteria for CT volume production. The Direct Conversion XC-Thor.10G platform (scroll down for data sheet) offers unique, high speed image acquisition rates of up to 1000 fps in industrial implementation settings.

The result, which has been demonstrated in real-world examples, is the reduction of CT inspection time per stacked battery corner by a factor of approximately 10 (100 – 200 fps with a 150 W X-ray tube and 1000 projections/ CT).

A full battery scan with four corners, including time for handling (such as positioning and automatic rotation to scan each corner) is performed in under one minute. Using a higher power tube/ source increases speed capabilities to > 200fps, so that a 4 x corner CT scan can be completed in less than 30 seconds.

Downloads

XC-Thor

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XC-Thor.10G

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XC-TDI

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