ELECTRIC VEHICLE BATTERY TESTING
As the global automotive industry trends towards electrification, battery manufacturers are under tremendous pressure to innovate and grow faster than ever before. Instron engineers are working closely with industry leaders to meet the growing demand for smaller, lighter, more powerful batteries. Current challenges include the development of test methods and fixturing customized to battery testing applications, along with throughput and efficiency improvements for QC labs. As a global leader in the materials testing industry, Instron is uniquely positioned to accommodate the needs of battery testing labs all over the world with local support that can respond quickly and in the local language, providing our full suite of services, including installation, calibration, training, onsite machine upgrades, and any service needs along the way to minimize downtime.
Batteries are comprised of a variety of materials, adhesives, welds, and component structures that require thorough testing. In addition to our wide offering of standard grips and fixtures for battery testing, Instron has developed custom fixtures specifically designed to improve the efficiency and repeatability of testing battery materials and components. Our Engineered Solutions Group can accommodate quick turnarounds on battery fixture designs to fit specific needs.
View Battery Testing AccessoriesSeparator films are a critical part of lithium-ion batteries as well as other liquid electrolyte batteries. The polymers used for these films must be strong enough to withstand the winding operation during assembly as well as plating of lithium on the anode in an uneven manner due to extensive use. Safer and stronger separator material more effectively prevents contact between the anode and cathode, while thinner material helps reduce the weight of each battery and improve energy density.
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Puncture Testing of separator film is critical to ensure the safety and longevity of each cell throughout the life cycle of a battery. Film must be strong enough to withstand punctures from dendrites that form with extensive use. Ensuring proper specimen tautness and alignment of an upper probe are critical for this application. Testing is similar to EN 14477 and ASTM F1306.
Both manual and pneumatically driven puncture fixtures are available to meet EN 14477, ASTM F1306, and more. Pneumatic fixtures ensure repeatable clamping forces and higher throughput. Integration into an existing system is as simple as installing a pneumatic grip.
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Tensile testing is used to ensure that separator film can withstand all mechanical operations through manufacturing and the life of the battery. Ensuring proper specimen alignment, insertion, and grip operation are necessary for best repeatability and throughput, as well as to avoid possible damage to a specimen before testing. We recommend using the Precision Specimen Loader to reduce variability in test results while improving ergonomics and safety. Testing is similar to ASTM D882 and ISO 527-3.
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Tight winding creates mechanical loads between the separator film and the electrode coating, and it is important to understand is the coefficient of friction between the two surfaces. Better understanding of the coefficient of friction can ensure proper winding processes occur in production. It’s common to use ISO 8295 and ASTM D1894-14 as guidance for this testing.
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Material selection for separator film is essential for battery integrity as any mechanical performance issues can increase the potential for internal short circuits, which can lead to thermal runaway. Testing the puncture resistance to an impact event is crucially important to selecting the material with the best performance with an added goal of reducing thickness and weight.
Learn MoreAutomation systems from Instron introduce a new level of productivity for battery testing. As battery production volumes continue to increase, throughput and efficiency are critical to keep up with demand. Utilizing an automation system with the recommended equipment for each application can free up operators and maximize throughput, while maintaining optimal results.
One of the most common failure modes in batteries is caused when the coating of electrode material cracks or delaminates from the current collector. This cracking or delaminating is typically caused by the constant charging and discharging of a battery as well as the mechanical loading when in use. It is critical to understand the electrode adhesion strength and longevity to ensure a battery does not fail before the end of its predicted life cycle.
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180° peel testing is a commonly used method for determining the adhesion strength of electrodes to the current collector. With the mechanical advantage of the peel setup and ease of alignment, this testing can be done using low force grips and load cells. It is best to consider pneumatic grips and the use of a metal substrate to ensure high throughput and a proper 180° peel throughout each test.
90° peel testing is another common method for testing electrode adhesion in batteries. The 90° peel test generally involves slightly higher loads than the 180° peel test and can be set up more quickly because it often does not require a substrate. Instron’s most common solutions for this testing are a standard 90° peel fixture or a pneumatic peel fixture designed specifically to test the adhesion of electrodes. The pneumatic 90° peel fixture provides improved repeatability and throughput while also aiding the operator in consistent specimen placement and alignment at 90°. For the upper fixture, a pneumatic grip optimizes throughput and repeatability and is recommended for testing delicate materials.
Tack tests have been backed by researchers as an additional way to test the adhesion of electrodes to the current collector in batteries. Instead of slowly peeling electrodes from the current collector, a tack test focuses on the adhesion strength of an entire predetermined area of electrodes. A very fast data rate collection paired with Instron’s tack test fixturing ensure the best possible results and throughput.
Aluminum and copper foil are used as current collectors in batteries, and are traditionally needed in large volumes. As the industry strives to use minimal amounts of material to achieve optimal energy density of each battery, it is critical to understand the mechanical properties of each foil in order to ensure the battery's safety and longevity. As foil becomes longer, thinner, and wider, improved technology is required to address the wrinkling and tearing that may come along with it. Validating and maintaining the mechanical properties of this material is critical for optimizing battery production.
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A standard tensile test is the most appropriate way to determine the mechanical properties of aluminum and copper foil specimens. Pneumatic side action grips offer constant pressure with quick throughput for these high-volume materials, and proper specimen alignment is critical for repeatability and protection of the specimen before testing, as thin foils can be affected by minor misalignment within the grips. We recommend using the Precision Specimen Loader to reduce variability in test results while improving ergonomics and safety. It’s common to use ASTM E345-16 as guidance for this testing.
As battery production volumes continue to increase and material gets thinner, throughput and efficiency are critical to keep up with demand. Utilizing an automation system with the recommended equipment can keep up with the demand for thinner, wider, and longer foil specimens as well as free up operators and maximize throughput, while maintaining optimal results.
View Automation SolutionsLithium-ion and other liquid electrolyte batteries require countless welds between electrodes, tabs, casings, and cells. Understanding the most common failure modes and strength of each weld is critical for determining the life of a battery. Each weld must withstand the mechanical loading that comes with being inside a vehicle or device, which can wear on the weld over time. Electric vehicles, for instance, are constantly moving and vibrating, and this must be accounted for in the design and quality of a weld.
Cylindrical cells require several welds during assembly, including the cathode tab to the cap of the cell, the anode tab to the base of the can, and even the tab to tab individual welds. All of these require proper alignment and gripping solutions for high throughput and repeatable results.
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The majority of the welds in prismatic cells are between the cathode/anode tabs to each of the current collectors, as well as within the busbar or the can itself. Failures can occur at all locations and must be checked for consistency and durability.
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Pouch cells have welded together anode or cathode tabs as well as tabs welded to the cell terminal. Additionally, pouch cells have busbar welding that needs to be tested. Proper fixture and specimen alignment, along with a versatile solution for different sizes, are important.
View Busbar Clamping StageAs more and more components and materials are being introduced into the battery industry, there are countless other features that need to be tested for the quality, strength, safety, and longevity of each design.
The swelling of a battery during charging and discharging is an important characteristic to test for. Some cells are known to have minimal expansion and contraction during cycling. However, prismatic and pouch cells are known to exhibit significant expansion and contraction, which must be characterized to ensure the proper use and safety of each cell.
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Stack compression testing can be used to best replicate real world forces and mechanical abuse during a batteries life.
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Instron’s wide range of compression platens, coupled with a standard or high-accuracy displacement sensor, can be used to fully characterize foam material behavior under load. Users can run static or cyclic compression tests using a set of compression platens, available in multiple sizes and shapes and synchronously acquire load and localized displacement data to test foam and gels used in EV battery cell and pack assemblies.
Additionally, a heat plate can be added to the lower compression anvil to control the temperature of the compression surface. A closed-loop controller is used to control the temperature of the plate and output the actual temperature readings to the testing software.
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Instron users can choose between manual and pneumatic grips to perform the important lap shear tests needed to characterize the bond strength of adhesives and welds used in pack and module assemblies. Specialized, automated solutions can also be provided to align grips laterally based on lap shear specimen information from a barcode or measured dimensions.
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Materials, cells, modules and packs can all perform differently in changing environmental conditions. Testing chambers integrated to the Instron test frame enable users to test their specimens under load while monitoring and controlling the test space environment.
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Universal Testing Systems
Universal testing systems can be equipped with a wide range of accessories to perform fundamental tests of strength and static properties. These are ideal for monotonic tests at low speed (1 - 600 mm/min).
Impact Testing Systems
Drop Tower systems are used to apply and measure impact loading at moderate-to-high speed (typically puncture or point indentation). Single-strike tests are controlled in terms of incident velocity and energy (1-24m/s and up to 1800J).
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Fatigue Testing Systems
Used for tests that require low-to-moderate force capacity, these machines are capable of fatigue and cyclic loading at up to 100 Hz (transient movements at over 1m/s or 40G acceleration), but can also be deployed for static tests.
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Servohydraulic High-Rate Testing Systems
These highly specialized testing systems can test at speeds up to 25m/s at high force and are commonly used to determine the properties of materials in crash conditions. They can also be used for puncture and crush testing.
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HDT Vicat
Testing Systems
These tests machines are used to characterize the behavior of plastic materials at high temperatures, measuring their heat deflection temperature (HDT) and Vicat softening temperature.
Automated
Testing Systems
Testing equipment is becoming increasingly automated, ranging from automatic specimen measurement devices to fully robotic systems, helping laboratories across the battery industry handle growing volumes of tests more efficiently.
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