How does the partial crush test lead to cell deactivation,
How does the partial crush test lead to cell deactivation,

▍What is ANATEL Homologation?

ANATEL is a short for Agencia Nacional de Telecomunicacoes which is Brazil governmental authority to certified communication products for both compulsory and voluntary certification. Its approval and compliance procedures are the same both for Brazil domestic and abroad products. If products are applicable to compulsory certification, the testing result and report must be in line with the specified rules and regulations as requested by ANATEL. Product certificate shall be granted by ANATEL first before product is circulated in marketing and put into practical application.

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Crush is a very typical test to verify the safety of cells, simulating the crush collision of cells or end products in daily use. There are generally two types of crush tests: flat crush and partial crush. Compared to the flat crush, the partial indentation caused by a spherical or cylindrical indenter is more likely to cause the cell ineffective. The sharper the indenter, the more concentrated the stress on the core structure of the lithium battery, the more serious the rupture of the inner core, which will cause deformation and displacement of the core, and even lead to serious consequences such as electrolyte leakage or even fire. So how does crush lead to the deactivation of the cell? Here introduce you to the internal structure evolution of the core in the local extrusion test.The squeezing force is applied to the cell enclosure first, and the enclosure deforms. The force is then transferred to the inside of the battery, and the cell assembly also starts to deform.
With further compression of the crush head, the deformation is expanding and localization is formed. At the same time, the layer spacing between each electrode layer is gradually shortened. Under continuous compression, the current collector is bent and deformed, and shear bands are formed. When the deformation of the electrode material reaches the limit, the electrode material will produce cracks.
With the increase of deformation, the crack gradually extends to the current collector, which will be torn and produce ductile fracture. In addition, the radial crack is elongated due to the increase of stress and radial displacement.