New Energy Industry

EV Battery Testing
EV Battery Cell, Module and Pack Solutions

As the global automotive industry moves toward electrification, battery manufacturers are under unprecedented pressure to innovate and evolve. ITM-LAB engineers are working closely with industry leaders to meet the growing demand for smaller, lighter and more powerful batteries. Current challenges include developing test methods and fixtures customized for battery testing applications, as well as improving throughput and efficiency in QC labs. As a global leader in the materials testing industry, ITM-LAB is uniquely positioned to meet the needs of battery testing labs around the world, providing local support that is responsive and in the local language, offering a full range of services including installation, calibration, training, on-site machine upgrades, and any service needs in the process to minimize downtime.

Material and Component Testing
Batteries consist of a variety of materials, adhesives, welds and component structures that require comprehensive testing. In addition to our wide range of standard grips and fixtures for battery testing, ITM-LAB develops custom fixtures specifically designed to improve efficiency and repeatability in testing battery materials and components. Our Engineering Solutions group can quickly complete battery fixture design to meet specific needs.

Separator Testing
Separators are an essential component of lithium-ion batteries as well as other liquid electrolyte batteries. The polymers used in these separators must be strong enough to withstand the winding operation during assembly and the uneven plating of lithium on the anode due to heavy use. Safer, stronger separator materials can more effectively prevent contact between the anode and cathode, while thinner materials help reduce the weight of each cell and increase energy density.

Puncture Testing
Separator puncture testing is critical to ensure the safety and longevity of each cell throughout the battery lifecycle. The separator must be strong enough to withstand punctures from dendrites formed due to heavy use. Ensuring proper sample tension and alignment of the upper probe is critical for this application. Testing is similar to EN 14477 and ASTM F1306.
Both manual and pneumatic puncture grips are available to meet standards such as EN 14477, ASTM F1306, etc. Pneumatic grips ensure repeatable clamping force and higher throughput. Integration into existing systems is as simple as installing pneumatic grips.

Tensile Testing
Tensile testing is used to ensure that the separator can withstand all mechanical manipulations during manufacturing and over the life of the battery. Ensuring proper sample alignment, insertion, and clamping is critical to achieving optimal repeatability and throughput, as well as avoiding damage to the sample prior to testing. We recommend using a precision sample loader to reduce variability in test results while improving ergonomics and safety. Testing is similar to ASTM D882 and ISO 527-3.

Friction Coefficient Testing
Tight winding creates mechanical loading between the separator and electrode coating, so it is important to understand the coefficient of friction between the two surfaces. A better understanding of the coefficient of friction ensures the proper winding process in production. ISO 8295 and ASTM D1894-14 are commonly used as guidance for this testing.

Puncture Resistance to Impact Events Testing
The selection of separator materials is critical to the integrity of the battery, as any mechanical performance issues can increase the likelihood of internal shorts, leading to thermal runaway. Testing for puncture resistance to impact events is critical to selecting the best performing material, while also reducing thickness and weight.

Automated Testing
ITM-LAB’s automated systems take battery testing to a new level of productivity. As battery production continues to increase, throughput and efficiency are critical to meet demand. Utilizing automated systems and recommended equipment for each application can free up operators and maximize production while maintaining optimal results.

Electrode Testing

One of the most common failure modes for batteries is the cracking or peeling of the electrode material coating from the current collector. This cracking or peeling is often caused by the constant charging and discharging of the battery and the mechanical loads of use. Understanding the bond strength and longevity of the electrode is critical to ensure that the battery does not fail before the end of its expected service life.

180 Degree Peel Test

The 180° peel test is a commonly used method to determine the strength of the electrode-to-current collector bond. Due to the mechanical advantages and easy alignment of the peeling device, this test can be performed using low-force grips and load cells. It is best to consider using pneumatic grips and metal substrates to ensure high throughput and proper 180° peel for each test.

90 Degree Peel Test
The 90° peel test is another common method for testing battery electrode adhesion. The 90° peel test typically has a slightly higher load than the 180° peel test and can be set up more quickly because it generally does not require a substrate. ITM-LAB’s most common solutions for this test are either a standard 90° peel fixture or a pneumatic peel fixture specifically designed for testing electrode adhesion. Pneumatic 90° peel fixtures provide better repeatability and throughput while also helping the operator to consistently position and align samples at 90°. For the upper fixture, pneumatic grips optimize throughput and repeatability and are recommended for testing delicate materials.

Adhesion Testing
Researchers support the use of adhesion testing as another method for testing electrode-to-current collector adhesion in batteries. Rather than slowly peeling the electrode from the current collector, adhesion testing focuses on the adhesion strength across a predetermined electrode area. The extremely fast data acquisition rate combined with ITM-LAB’s adhesion testing fixtures ensures optimal results and throughput.

Foil Testing
Aluminum and copper foils are used as current collectors in batteries and have traditionally been used in large quantities. As the industry strives to use the least amount of material to achieve the best energy density in each battery, understanding the mechanical properties of each foil is critical to ensuring battery safety and longevity. As foils become longer, thinner, and wider, improved technology is needed to address the wrinkling and tearing that can ensue. Verifying and maintaining the mechanical properties of this material is critical to optimizing battery production.

Tensile Testing
Standard tensile testing is the most appropriate method for determining the mechanical properties of aluminum and copper foil samples. Pneumatic side grips provide constant pressure and fast throughput for these high-volume materials, and proper sample alignment is critical for sample repeatability and protection prior to testing, as thin foils can be affected by slight misalignments within the grips. We recommend using a precision sample loader to reduce variance in test results while improving ergonomics and safety. ASTM E345-16 is often used as a guide for this test.

Automated Testing
As battery production continues to increase, materials are becoming thinner, and throughput and efficiency are critical to meet demand. Utilizing automated systems and recommended equipment can meet the demand for thinner, wider, and longer foil samples while freeing up operators and maximizing throughput while maintaining optimal results.

Weld Inspection
Lithium-ion batteries and other liquid electrolyte batteries require countless welds between electrodes, tabs, casings, and cells. Understanding the most common failure modes and strengths of each weld is critical to determining the life of the battery. Each weld must withstand the mechanical loads found within a vehicle or device, which can wear the weld over time. For example, electric vehicles are constantly moving and vibrating, which must be accounted for in terms of weld design and quality.

Cylindrical Battery Weld Testing
Cylindrical batteries require multiple welds during assembly, including welding the cathode tab to the battery cover, welding the anode tab to the can bottom, and even individual tab-to-tab welds. All of these require proper alignment and gripping solutions for high throughput and repeatable results.

Prismatic Battery Weld Inspection
The majority of welds in prismatic cells are between the cathode/anode tabs and each current collector, as well as within the busbar or battery can itself. Failures can occur in all locations, and they must be checked for consistency and durability.

Pouch Cell Weld Testing
Pouch cells have the anode or cathode tabs welded together and the tabs welded to the battery terminals. In addition, pouch cells have busbar welds that need to be tested. Proper fixture and sample alignment, as well as versatile solutions for different sizes, are important.

Additional Testing
As more components and materials are introduced into the battery industry, there are countless other features that need to be tested to ensure the quality, strength, safety, and longevity of each design.

Swelling Testing
The expansion of the battery during charge and discharge is an important feature that needs to be tested. It is well known that some batteries expand and contract only minimally during cycling. However, prismatic and pouch cells can exhibit significant expansion and contraction that must be characterized to ensure proper use and safety of each battery.

Stack Compression Testing
Stack compression testing can be used to best replicate the real forces and mechanical abuse during the life of a battery

Foam Compression Testing
ITM-LAB’s wide range of compression platens, combined with standard or high-precision displacement sensors, can be used to fully characterize the behavior of foam materials under load. Users can use a set of compression platens (available in a variety of sizes and shapes) to perform static or cyclic compression tests and acquire load and local displacement data simultaneously to test foams and gels used in EV battery cell and pack assemblies. In addition, a heated plate can be added to the lower anvil to control the temperature of the press face, and a closed-loop controller can be used to control the heated plate temperature and output the actual temperature reading to the test software.

Lap Shear Testing
ITM-LAB users can choose between manual or pneumatic grips to perform the important lap shear test to characterize the bond strength of adhesives and welds used in battery pack and module assemblies. Specialized automated solutions are also available to align the grips laterally based on lap shear sample information from barcodes or measured dimensions.

Environmental Testing
Materials, cells, modules and packs behave differently under changing environmental conditions. The test chamber integrated into the ITM-LAB test framework enables users to test their samples under load while monitoring and controlling the test space environment.