Testing the adhesion strength of lithium-ion battery electrode coatings

The life expectancy of lithium-ion batteries for electrically powered vehicles is closely linked to the adhesion strength between the electrode coating and the substrate. Testing the adhesion strength allows prediction of the mechanical bond before it is actually used. Available from Zwick is an ideal solution consisting of an AllroundLine materials testing machine plus a special test device.
Z-direction tensile test1
Z-direction tensile test2

The life expectancy of lithium-ion batteries for electrically powered vehicles is closely linked to the adhesion strength between the electrode coating and the substrate. Testing the adhesion strength allows prediction of the mechanical bond before it is actually used. Available from Zwick is an ideal solution consisting of an AllroundLine materials testing machine plus a special test device.

The bond strength between current collector and coating can be determined via a tensile test. This provides precise information regarding the mechanical strength of the electrode coating, particularly its adhesion to the current collector, and concerning the quality of the mechanical joint. The aim is to establish a conclusive relationship between the materials, the process parameters and the electro-chemical activity in the battery. In preparation for the Z-direction tensile test, special double-sided adhesive tape is applied to parallel test platens. Having previously been trimmed to size, the electrode is then inserted between the platens and attached firmly under a defined pre-load by means of the adhesive tapes. To determine adhesion strength, the peel test is continued until the coating is pulled off the current collector. Meet the most demanding testing requirements During measurement of separation behavior the electrode separates from the substrate in a series of pulses. The high measured-value acquisition-rate (2,000 Hz) of the testControl II measurement and control electronics allows clearly defined recording and display of these force peaks. AllroundLine's precision crosshead guidance and high stiffness minimize undesirable mechanical influences on the specimen, while crosshead resolution exceeds the values usually available by a factor of 2, thanks to the use of a Hiperface motor feedback system. Other test resolution highlights available with AllroundLine plus testControl II include outstanding measurement reproducibility, return speeds well above the nominal speed and excellent constant-speed characteristics, even at the lowest speeds. Ideal for varying testing requirements AllroundLine is ideal for use in laboratories with demanding testing applications subject to frequent changes. The presence of two test areas allows two alternative test applications to be used immediately, saving reconfiguration time and maintaining test result reproducibility. The flexible adapter system, large test area and integrated T-slotted platforms also allow the use of large, complex test arrangements, while the comprehensive storage system means that all test fixtures are always quickly and conveniently to hand. AllroundLine gives the user access to all the legally prescribed safety requirements contained in the EC Machinery Directive.

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