Process that lithium batteries must go through before leaving the factory

Like other batteries, lithium batteries must be converted, tested, and sorted before they leave the factory. The formation of lithium batteries has two important uses: one is to convert the active material in the battery into a substance with a normal electrochemical effect through a single charge; the other is to form an effective passivation film (SEI film) on the important negative surface of the electrode to prevent The negative electrode reacts spontaneously with the electrolyte, and at the same time, the active material is in good contact with the electrolyte. Generally speaking, each manufacturer has its own chemical conditions. In addition to taking materials and manufacturing processes as a secret, battery manufacturers have also listed chemical conditions as an important secret for each company's battery manufacturing. During the formation of the battery, due to the irreversible reaction of the battery, in the initial stage, the first few charge and discharge of the battery will reduce the discharge capacity of the battery. After the electrochemical state is stable, the battery capacity tends to be stable. Therefore, some formation processes include multiple charge and discharge cycles to achieve the purpose of stabilizing the battery. Regarding all lithium batteries, it is very important to control the charging process, usually by constant current charging first, and then constant voltage charging when the battery charging voltage reaches the set value. When the lithium battery is charged with an inappropriate cut-off voltage and constant voltage, it will easily affect the cycle life, and even cause the electrolyte to decompose, causing danger. Therefore, the constant current charging method commonly used for nickel-cadmium batteries and nickel-hydrogen batteries cannot be used. Since lithium batteries usually use constant voltage charging, the cut-off voltage of charging must be accurately controlled. The detection process of lithium batteries mainly includes five stages: constant current charging stage, constant voltage charging stage, charge-discharge interval stage, discharge interval stage and cycle interval stage. In the constant current charging stage, there is a peak voltage that limits the charging of the constant current charging terminal. When the battery voltage reaches the upper limit of 4.1v or 4.2v, the constant current charging phase ends, and the battery enters the next phase, that is, the constant voltage charging phase. Constant voltage charging refers to charging the battery without changing the voltage across the battery. At this stage, the charging current is gradually reduced to zero, so that the battery is fully charged. During the charge-discharge interval, the battery is in a self-discharge state. The discharge stage is the key stage of battery detection and sorting. The capacity of the battery at this stage is calculated by the product of the discharge current and the discharge time. Before and after the battery is placed on the shelf, measure the battery impedance. After the test is over, the data is combined with the battery capacity value to perform battery sorting. Generally speaking, the lower the battery impedance, the better the battery performance and the better the overall performance. The formation and separation of batteries is very important, especially in the application process of lithium batteries, often in parallel, series or a combination of multiple groups of batteries. Good-shaped batteries are classified according to certain rules. For example, according to the discharge capacity or discharge curve, the batteries with similar performance are divided into one category and assembled into a battery pack to ensure the good operation of the battery. 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: Analysis of my country's power lithium battery industry scale