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What are the Protective Measures for Electric Vehicle Batteries?

Jul. 23, 2021

Shell protection, in order to prevent air from entering, lithium batteries are encapsulated in a closed container, and in order to prevent external force damage usually equipped with stainless steel shell and aluminum alloy shell. For example, Tesla's electric cars even use titanium alloy shields to prevent damage to the battery container during car use, especially in traffic accidents. As a Chinese Lithium Battery Manufacturer, share with you.

EV Battery

EV Battery

The diaphragm blocking protection prevents damage from external forces while also preventing damage from inside the battery.

Usually, in order to prevent the positive and negative electrodes of the battery from directly touching and short-circuiting, there is a separator in the battery, which separates the positive and negative electrodes on the one hand, and allows charged ions to pass through on the other.

However, in lithium batteries, the separator also assumes another protective function. When the battery temperature is too high, the diaphragm gap will automatically close, so that lithium ions cannot pass through, thereby terminating the entire battery reaction. This prevents the battery from causing the electrolyte to vaporize to generate high pressure due to the excessively high temperature of the battery, which would damage the battery's sealing structure.

Overcharge voltage protection not only keeps the air out, but also prevents metal lithium from leaking from the electrode.

Scientists use the nano-voids of electrode materials and the material lattice mechanism to store and lock the metallic lithium formed during charging and discharging.

In this way, even if the battery shell ruptures and oxygen enters, the oxygen molecules are too large to enter these small storage cells, and spontaneous combustion is avoided.

However, using too high voltage or continuing to charge for too long after being fully charged will cause very dangerous damage to the lithium battery.

After the charging voltage of the lithium battery is higher than the rated voltage (usually 4.2V), if you continue to charge, since the storage cell of the negative electrode is already filled with lithium atoms, subsequent lithium ions will accumulate on the surface of the negative electrode material. Due to polarization, these lithium ions will form electron transfer to form metallic lithium, and dendrites will grow from the surface of the negative electrode to the direction of the lithium ions.

These metal lithiums without electrode protection are extremely active on the one hand, and are prone to oxidation reactions and explosions. On the other hand, the formed metallic lithium crystals will pierce the separator and short-circuit the positive and negative electrodes, which will cause a short circuit and generate high temperatures. At high temperatures, the electrolyte and other materials will crack to produce gas, causing the battery casing or pressure valve to swell and rupture, allowing oxygen to enter, and react with the lithium atoms accumulated on the surface of the negative electrode, and then explode.

When charging a lithium battery, be sure to set the upper voltage limit and overcharge protection. Lithium batteries produced by regular battery manufacturers are equipped with such protection circuits. When the voltage exceeds the standard or the battery is full, it will automatically cut off the power.

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