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

▍What is TISI Certification?

TISI is short for Thai Industrial Standards Institute, affiliating to Thailand Industry Department. TISI is responsible for formulating the domestic standards as well as participating in international standards formulation and supervising the products and qualified assessment procedure to ensure the standard compliance and recognition. TISI is a governmental authorized regulatory organization for compulsory certification in Thailand. It is also responsible for formation and management of standards, lab approval, personnel training and product registration. It is noted that there is no non-governmental compulsory certification body in Thailand.

There is voluntary and compulsory certification in Thailand. TISI logos (see Figures 1 and 2) are allowed to use when products meet the standards. For products that have not yet been standardized, TISI also implements product registration as a temporary means of certification.

▍Compulsory Certification Scope

The compulsory certification covers 107 categories, 10 fields, including: electrical equipment, accessories, medical equipment, construction materials, consumer goods, vehicles, PVC pipes, LPG gas containers and agricultural products. Products beyond this scope are fall within the voluntary certification scope. Battery is compulsory certification product in TISI certification.

Applied standard: TIS 2217-2548 (2005)

Applied batteries：Secondary cells and batteries(containing alkaline or other non-acid electrolytes – safety requirements for portable sealed secondary cells, and for batteries made from them, for use in portable applications)

License issuance authority:  Thai Industrial Standards Institute

▍Why MCM?

● MCM cooperates with factory audit organizations, laboratory and TISI directly, capable to provide best certification solution for clients.

● MCM possesses 10 years abundant experience in battery industry, capable to provide professional technical support.

● MCM provides one-stop bundle service to help clients enter into multiple markets (not only Thailand included) successfully with simple procedure.

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.
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.