The common safety tests of power battery mainly include overcharge, overdischarge, extrusion and needling, among which battery needling is also known as the most severe safety test. The main purpose of battery needle extrusion test is to simulate the safety of lithium-ion battery under internal short circuit. There are many factors causing internal short circuit of lithium-ion battery, such as metal particles in the production process, lithium dendrite produced by low-temperature charging, copper dendrite produced by overdischarge, etc., which may lead to positive and negative short circuit. Once internal short circuit occurs, the whole battery will discharge through the short circuit point, and the battery will be damaged A large amount of energy is released through the short-circuit point in a short time (up to 70% of the energy is released within 60s), which causes the temperature to rise rapidly, leading to the decomposition of positive and negative active substances and the combustion of electrolyte. In serious cases, it will lead to the battery fire and explosion.

        The original intention of the battery pinprick extrusion test design is to simulate the internal short circuit of the lithium-ion battery. In addition, the methods to simulate the internal short circuit of the lithium-ion battery are extrusion test (extrusion makes the diaphragm fail, causing the positive and negative short circuit), internal short circuit device (manufacturing defects in the battery, adding paraffin insulation sheet at the same time, causing the paraffin to melt by external heating, causing the internal short circuit Among them, needling and extrusion are widely used in practice because of their respective defects because of their convenient operation.