Lithium-ion battery structure
First, let's look at the structure of lithium-ion batteries.
The organic solvents used in lithium-ion batteries contain
1. Acid carbonates: carbon vinyl ester (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), propylene carbonate (PC), etc.
2. Carboxylic acid esters: (methyl formate (MF), methyl acetate (MA), etc.)
3. Ether organic solvents (ethylene glycol dimethyl ether (DME), etc.)
4. Sulfur-containing organic solvents: vinyl sulfite, etc.
Electrolyte (electrolyte salt LiPF6) solvent is mainly composed of alkyl carbonate, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), etc., are very low boiling point flammable liquid, easy to burn in case of fire.
Lithium hexafluorophosphate (LiPF6) has a corrosive effect. Non-combustible, reacting with acid when heated will produce harmful hydrogen fluoride (corrosive). Hydrogen fluoride reacts with metal to produce explosive gas.
Produces sparks that ignite the electrolyte, which in turn spills over to the plastic body and flammable materials in contact with it, causing a fire.
Causing a rapid rise in temperature inside the cell, which is a very small space inside the cell and may explode due to increased pressure.
The temperature inside the battery rises slowly and the battery shell gradually melts, causing the corrosive electrolyte to leak.
Identification of dangerous and harmful factors of lithium batteries
(1) lithium battery fire accident mechanism
As shown in the figure
1) The effect of overcharge on lithium-ion battery
In the process of overcharging, the voltage of lithium battery will lose control and continue to rise, the cathode material in the state of lithium-poor will decompose and release heat, when the cathode potential rises to the electrolyte oxidation decomposition potential, the electrolyte will oxidize and decompose on the surface of the cathode, releasing a large amount of gas and heat, thus the risk of rupture, smoke, fire and explosion.
2) The effect of short circuit on lithium ion
The electrode material and electrolyte of lithium-ion battery are flammable and easily damaged, resulting in a short circuit inside the battery, the huge energy stored in the short-circuit lithium battery will be quickly released in the form of heat, this rapid exothermic behavior will cause the internal temperature of the battery to rise sharply, the electrolyte is easy to ignite at high temperatures, resulting in the risk of rupture, smoke and fire.
Lithium-ion battery safety precautions
1. lithium-ion batteries are strictly prohibited from discharging terminals charging, must use the matching special charger from the charging socket for charging. When the charging indicator on the charger stops rolling, please promptly remove the charging plug to avoid overcharging the battery.
2. lithium-ion battery pack with over-current protection function, when the use of electric equipment current exceeds the maximum output current of the product, over-current protection circuit action and make the use of electric equipment does not seem to work properly.
3. The battery system should be stored in a clean, dry and ventilated indoor environment with an ambient temperature of 20±5 and a relative temperature of not more than 75%.
Post time: Aug-24-2021