Lithium-ion battery explosion-proof circuit and explosion-proof cell technology

Lithium-ion battery explosion-proof technology Lithium-ion battery has become the battery of choice for portable electronic devices. Batteries, with their high capacity density and competitive prices, are expected to remain the mainstream of the market in the next few years. But lithium-ion batteries are always in danger of explosion. As the application rises, so does the explosion. In fact, through the correct battery system design and the determination of battery capacity, lithium-ion batteries are very safe. At present, the explosion-proof circuit and the core technology of explosion-proof are mature, and there should be fewer and fewer explosions. Lithium-ion battery characteristics Lithium is the smallest and most active metal on the periodic table. Because of its small size and high capacity density, it is deeply loved by users and engineers. However, the chemical nature is too active, which brings high risks. When lithium is exposed to the air, it undergoes a violent oxidation reaction with oxygen. In order to improve safety and voltage, scientists have developed materials such as graphite and lithium cobalt oxide to store lithium atoms. The molecular structure of these materials forms tiny nano-scale storage cells that can be used to store lithium atoms. In this way, even if the battery casing breaks and oxygen enters, the oxygen molecules are too large to fit into the tiny battery, thereby preventing lithium atoms from coming into contact with oxygen and exploding. This principle of lithium ion batteries enables people to achieve safety while achieving high capacity density. When a lithium ion battery is charged, lithium atoms lose electrons and are oxidized into lithium ions. Lithium ions pass through the electrolyte to the cathode, where they enter the cathode cell, gain an electron, and are reduced to lithium atoms. When unloading, the whole process is reversed. In order to prevent the battery from being short-circuited due to the direct contact between the positive electrode and the negative electrode, a diaphragm paper with many small holes is added to the battery to prevent short-circuit. A good diaphragm paper can also automatically close small holes when the battery temperature is too high, so that lithium ions cannot pass through, so as not to waste time and prevent danger. Protection measures When the charging voltage exceeds 4.2v, the lithium-ion battery will begin to appear side-effects. The greater the pressure, the greater the risk. When the voltage of a lithium-ion battery is higher than 4.2v, less than half of the lithium atoms remain in the positive electrode material, and the battery often collapses, resulting in a permanent decrease in battery capacity. If the battery is charged, subsequent lithium metal will accumulate on the surface of the material because the negative battery is already full of lithium atoms. These lithium atoms grow dendrites from the surface of the cathode toward the lithium ions. These lithium crystals will pass through the diaphragm paper, shorting the anode and cathode. Sometimes the battery explodes before the short circuit occurs. This is because when overcharged, the electrolyte and other substances will decompose to produce gas, causing the battery casing or pressure valve to expand and burst, allowing oxygen to enter and react with the lithium atoms accumulated on the surface of the negative electrode, causing the negative electrode to explode. Therefore, when charging a lithium-ion battery, the upper voltage limit must be set to take into account the battery's life, capacity, and safety. The optimal upper limit of the charging voltage is 4.2v. Li-ion battery discharge must also have a lower voltage limit. When the battery voltage is lower than 2.4v, some materials begin to be damaged. And because the battery will self-discharge, the longer the voltage, the lower it is. Therefore, it is best not to stop the discharge to 2.4V. During the discharge period from 3.0v to 2.4v, the lithium-ion battery can only release about 3% of its capacity. Therefore, 3.0v is the ideal discharge cut-off voltage. When charging and discharging, in addition to voltage limitation, current limitation is also necessary. When the current is too large, lithium ions have no time to enter the storage battery and will accumulate on the surface of the material. When these ions gain electrons, they crystallize lithium atoms on the surface of the material, which is the same risk as overcharging. If the battery box is broken, it will explode. Therefore, the protection of lithium-ion batteries should include at least three parts: the upper limit of the charging voltage, the lower limit of the discharge voltage, and the upper limit of the current. In addition to lithium-ion battery cells, a general lithium-ion battery pack will also have a protection board, which is important to provide these three protections. However, the protection of the three protective plates is obviously insufficient, and explosion accidents of lithium-ion batteries are still common. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Introduction to the safety features of lithium-ion batteries