With the popularity of electric cars growing, safety and electric power of electric cars need more attention. If a high-energy accident such as a collision occurs when using an electric vehicle, the lithium-ion battery may have significant damage, which may lead to serious safety problems such as short circuits in the internal and lithium ion batteries.
When an internal short circuit occurs in a lithium-ion battery, 70% of the energy of the entire battery will be released from the short circuit within 60 seconds, causing the temperature to rise rapidly in the area, which makes bones. Positive and negative working conditions, electrolyte, etc., which lead to the overheating of lithium-ion batteries.
In order to ensure the safety of lithium-ion batteries under the above conditions, people have developed a strong compression test to evaluate the safety performance of lithium-ion batteries under severe deformation. Research shows that during the crushing test, deformation and deformation of the electrode group will occur first. With increasing numbers, the collector current will fall on the 45 degree line. Finally, the diaphragm changes too much, causing the diaphragm to collapse, making the short-term area shorter.
Once an internal short circuit occurs, it can cause the lithium-ion battery to overheat and the high temperature will cause the battery to burn. Even if there is no thermal runaway, the high temperature area will still melt part of the current collector, separator, etc., so we need to study the structural changes of lithium-ion batteries in the test of ‘crushing.
Later, it was discovered that the copper foil produces irregular pieces during the extrusion test, and these things are difficult to find with traditional light and electron microscopes. These hidden pieces of copper foil can have a significant impact on the electrical performance and running behavior of lithium-ion batteries.
Broken copper wire can have these effects on lithium-ion batteries.
- Broken copper insulation can not take the function of the current collector, causing the local active material to slow down the effective connection to the network.
- Active substances and electrolytes will fill the voids in the broken copper sheet, but they are not good conductors of electricity and heat, so when a short circuit occurs here, it is difficult to heat quickly.
- In the calculation, due to the poor contact between the active material and the conductive network, the activity is reduced, or it cannot contribute to the charging reaction. And interruptions, resulting in reduced capacity of lithium -ion batteries.
- Broken copper wire will reduce the performance of the negative electrode.
- The worst failure of the battery in the crush test was caused by the failure of the positive electrode and separation.
- At the beginning of the small circuit, the aluminum foil / active material of the positive electrode is connected to the copper sheet / active material of graphite of the negative electrode.
The best option to test this type of lithium battery is to use the Battery Nail Penetration Tester so that you can not only see the reaction of the battery during the penetration, but also see what happens to the battery during nail penetration.
