The ZHN universal nano-mechanical testing machine’s design principle minimizes parasitic environmental influences, such as temperature variations. (ZwickRoell)

ZwickRoell rallies for EV battery testing

Cells and coatings are gateways to new milestones for electric-vehicle batteries, but progress could be sidetracked without reliable testing methodologies.

A lightweight, higher-capacity lithium-ion or Li-blended battery could fast-track the demand for electric vehicles (EVs) by increasing the driving range, but progress could be easily sidetracked without reliable, repeatable testing methods. “In order to improve the technical capabilities of batteries, mechanical testing must be an integral part of the development process,” said Aleksander Koprivc, automotive industry manager for materials test machine supplier ZwickRoell.

Amid a backdrop of dynamic and static materials testing equipment on display at ZwickRoell’s campus in Ulm, Germany, Koprivc and others spoke with Automotive Engineering during the firm’s recent 28th International Forum for Materials Testing. The company’s customers include 80% of the world’s top automotive suppliers, all major global automakers as well as several start-up companies. For those companies involved with eMobility, the quest for better-performing batteries is more than desirable. It reigns as an outright game-changer.

“Every R&D department that is serious about developing next-generation batteries should be doing tons of tests on the copper and aluminum foils for the electrodes and cathodes. They should be doing tons of tests on the different coatings, and they should be doing tons of tests on the mechanical behavior of the cell,” Koprivc stressed. The ability to predict how a specific material will react during operating conditions is must-have information, and physical tests are the conduit to obtaining that data. “Our main message is you need reliable test results,” Koprivc said.

One example that underscores the value of physical testing relates to the reactions that happen when Li-ion batteries are being recharged. In simplistic terms, the cells encounter dramatic stresses from the thermal expansion that occurs during battery recharging. While mechanical tests help researchers and engineers understand how the cell material is likely to perform during operating conditions, it is just as important to understand how the material is likely to react during the production process.

“Let’s say the production process is highly automated, so that means the material will be under stress being stretched, tempered and coated. There are a lot of things going on with the material that need to be understood in the R&D stage so that in the vehicle production application, the battery will be OK,” Koprivc said.

Physical testing paired with software
Testing software is the operational brains behind a wide array of the firm’s standardized and customized equipment. “Software is an integral part of a testing machine,” Koprivc said, noting a slew of software options, including the company’s intelligent testing program for applicable industry standards compliance. One constant for equipment users is finding new testing applications for a specific machine, which underscores the firm’s ZHN universal nano-mechanical testing machine.

A few years ago, the machine was used to evaluate coatings for internal combustion engine piston pins and injection needles, according to Dr. Thomas Chudoba, the machine’s developer and the managing director of ASMEC Advanced Surface Mechanics, a ZwickRoell company. “This machine can also be used to test battery coatings for Li-ion batteries, and it can be used to test ceramic separator materials,” Chudoba said. The testing machine’s indentation heads operate in both the compression and tensile directions to provide high-accuracy measurements of thin electrode coatings in the nano-range.

“What’s unique is that the machine with two measuring heads combines two directions of force application – normal and lateral to the sample surface – without either direction being influenced by the other direction,” Chudoba explained. Additionally, dynamic forces can be applied in both directions. By physically simulating a combination of forces, the machine essentially mimics a coating material’s work environment. “A coating almost always encounters friction, so this machine helps researchers understand the dynamic and frictional behaviors that occur on the coating surface during usage,” Chudoba said. 

For users of the nano-mechanical testing machine and other equipment, in-house developed software is slated for release in January 2020. “We are adding more functionality and features within a user-friendly context,” Koprivc said. When designing the latest software version, developers purposely counted the number of mouse clicks needed to do various operational tasks. ”It’s not rocket science to count mouse clicks, but it is important to make sure that you have a low number of mouse clicks to go from setting up a test to printing out a report,” Koprivc said.

A look to the future
Unlike a testing report that contains findings on a specific series of tests, predicting the future is not always reliable. That lack of clarity challenges companies in terms of determining what will be needed to match future product development needs. “While we listen to customers and hear what they think they’ll need for tomorrow, we also have to develop our own view of where the industry is going,” said ZwickRoell’s CEO Dr. Jan Stefan Roell. Paying close attention to the activities of certain companies in specific regions is helpful. “It’s easy to find out which companies in which countries are taking a lead in the different fields,” he said.

Companies based in the United States, China, Japan, South Korea and Europe are leading the way with EVs and battery developments. “There are lots of new things to be tested. But at this point, it is difficult to estimate future volumes,” Roell said, adding that the need for test equipment isn’t in doubt. “There will be lots of testing for batteries on all levels, ranging from thin films/foils to crash testing,” Roell said, adding, “The general need for testing systems in the automotive industry will grow.”

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