Published on 17-May-2024

Customized Microscopy Solutions for Electric Vehicle Battery Inspection

Customized Microscopy Solutions for Electric Vehicle Battery Inspection

Table of Content

Global electric vehicle (EV) sales have been growing steadily. EV unit sales are expected to reach over 17 million vehicles in 2028. The rapid shift toward EVs means that new inspection solutions are needed to help ensure the quality of critical components. For electric cars, these components include the battery cell package and copper and aluminum current collectors.

In this post, Evident shares three examples of custom inspection solutions they created for EV battery manufacturers, enabling them to inspect these critical components at their required volume.

Electric Vehicle Battery Inspection

Today, electric cars mostly use lithium-ion batteries. While they are a popular choice due to their lightweight and high energy density, capacity, and efficiency, lithium-ion batteries pose certain safety risks. For instance, a lithium-ion battery cell that short circuits can cause a fire, explosion, or other accidents. Contamination or damage introduced during the manufacturing process can also affect battery safety and performance. As a result, it’s critical to have rigorous inspection processes throughout battery production. The entire EV power battery system depends on battery safety to perform well.

During lithium-ion battery manufacturing, several battery components are normally inspected: the current collector, electrode material, and separator. Here’s a brief overview of each part:

  • The current collector is a sheet-like metal that supplies electrical energy to the tab lead. In general, copper is used in the cathode, and aluminum is used in the anode.
  • The electrode material is pasted on the current collector to flow electrical energy. It is a mixture of an active material, binder, and conductive material.
  • The separator is located in between the cathode and the anode to prevent an electrical short caused by their contact. It has many micro-sized holes, and only lithium ions can pass through them (unlike electrical energy).

Industrial Microscope Inspections of Lithium-Ion Battery Materials

Our industrial microscope systems can perform a variety of inspections on these lithium-ion battery materials, including:

1. Roughness of the current collectors and electrodes.

The electrode material and current collector must have high adhesion to maintain a stable battery capacity. The appropriate roughness level of the current collector depends on the type of electrode material applied. Therefore, control of the current collector roughness is important for battery quality control.

Roughness measurement of the current collector copper foil using the LEXT OLS5100 3D laser confocal microscope.

2. Burrs on the electrode or current collector.

A burr on a lithium-ion battery’s electrode material or current collector can result in an electrical short circuit, and the battery may overheat and even ignite during operation. Therefore, batteries need to be strictly inspected for burrs to help ensure their safety.

Observation of an electrode plate burr using the DSX1000 digital microscope.

3. Electrode cross-section.

After an electrode is completed, the electrode is placed vertically. An inspector then uses a microscope to check the adhesion between the electrode material and the current collector from the cross-section.

3D measurement of an electrode plate cross-section using the DSX1000 digital microscope.

4. Dimension of the battery packs.

This measurement is completed to check that the dimensions are within the specifications required by the manufacturer.

Electric Vehicle Battery Inspection Challenges

Performing these inspections can present multiple challenges depending on your microscope systems and inspection requirements. Here are some common challenges and ways to solve them:

1. It’s difficult to acquire high-quality images of battery samples.

For good battery quality, the stacking processes in the battery manufacturing must have high quality control. A certain number of sheets of anode, separators, and cathode are stacked, and the stacked body is inserted into a battery container. After that, the tab lead, which transfers electricity to and from the outside, is welded at the inlet and outlet of the anode and cathode.

An important part of the quality control process is to inspect the surfaces and check for defects such as burrs, scratches, and metal contamination. Therefore, acquiring high-quality images of these aluminum and copper surfaces is an important step in quality control.

The MIX and differential interference contrast (DIC) observation methods are good options for detecting surface defects. They provide different lighting conditions that enhance certain features of the defects. For example, DIC observation can enhance height differences (in the nm range) on the defects or sample surface waviness. With MIX observation, scratches can be enhanced with the darkfield and brightfield combination.