Assessing the effect of mechanical deformation of the panasonic NCR18650B lithium-ion power cell housing on its fire safety

Abstract

This paper considers the deformation properties of the body of the lithium-ion power cell (LIPC) Panasonic NCR18650B (LiNi0.8Co0.15Al0.05O2) exposed to the action of static load at various techniques of fixing the cell. Determining the properties of LIPCs under appropriate conditions makes it possible to fill the gap in existing studies, which will further ensure the safety of their use.

Based on the results of experimental studies, the LIPC rigidity and temperature indicators were determined in accordance with the applied load. The most dangerous variant, from the point of view of fire danger, of applying a static load on the cell has been established.

It was experimentally established that, on average, the Panasonic NCR18650B LIPC housing can withstand a load of about 80 kg·s/cm2 (or 7.84 MPa) without further ignition. An increase in pressure force in the range exceeding 85–90 kg·s/cm2 leads to an irreversible chain thermochemical reaction, which, within 2–3 seconds, leads to LIPC ignition. Compressing the LIPC evenly along its lateral surface showed the occurrence of combustion at the load on the cell equal to 150 kg·s/cm2. The average temperature of the cell during combustion caused by the deformation of the housing is 350–450 °C, and the maximum value is registered in the range of 580–680 °C.

The mathematical model built on the basis of the mathematical theory of thin shells adequately describes the stressed-strained state of the cylindrical body of cells under the action of a force concentrated and distributed load. The estimation model is satisfactorily verified by experimental results, making it possible to improve the strength and rigidity of LIPC housing by choosing the appropriate steel grade for its body, the geometric dimensions, and the structural technique of its fastening.