Compared with lead-acid batteries, lithium batteries are more prone to explosion and fire accidents, mainly because their electrolytes are different. The electrolyte of lead-acid batteries is generally an aqueous solution, which is not easy to catch fire; while the electrolyte in lithium batteries is organic matter, we can directly understand it as gasoline which is flammable.
So why can lead-acid batteries use aqueous solution, while lithium batteries use relatively dangerous organic matter as electrolyte?
Simply put, it is because the maximum ionization voltage of the two is different.The highest ionization voltage of aqueous solution is 2V, which is far from enough for lithium battery.In order to improve the electric energy density, lithium batteries must use organic matter as electrolyte.When the organic electrolyte is sealed in such a narrow space as the battery, there will be a high risk of explosion and fire.
Why is it easy to cause lithium batteries to explode and catch fire when charging? The destruction of the SEI film (the solid electrolyte membrane) of the negative electrode is one of the main reasons. Same as lead-acid batteries, lithium batteries are also divided into positive and negative electrodes. The positive electrode is generally a transition metal oxide of lithium, and the negative electrode is graphite and carbon.
When the SEI film on the surface of the negative electrode is destroyed, the carbon and lithium compounds generated during charging cannot react normally, and huge heat is generated inside the battery. When the temperature rises, the positive electrode of the lithium battery will automatically release oxygen. When the three combustion conditions of "temperature rise, the presence of flammable substances, and the presence of oxygen" are met, the probability of explosion and fire rises sharply.
It is precisely because the positive electrode of lithium battery will automatically release oxygen when the temperature rises, so we can't put out the fire by isolating oxygen, that is to say, dry powder fire extinguishers are useless. Therefore, lithium battery fire is very dangerous.
So how to solve the safety problem of lithium batteries? This is a systematic project, which needs to be carried out from the battery design, to the battery protection board, and then to the charging. Therefore, users who have purchased a lithium battery vehicle must use the battery in accordance with the regulations, avoid some charging items prohibited in the manual, and recommend that you conduct a battery safety inspection about once a year to prevent problems before they occur.
Luyuan's BMS battery management system can check whether the lithium battery is damaged. If there is a problem, charging is automatically disabled. If you encounter the situation that the lithium battery cannot be charged, please do not continue to forcibly charge the battery by short-circuiting the BMS board. Instead, you should go to a special store or maintenance office to find the reason for the inability to charge, and then prescribe the right way to solve the problem.