Popular science about battery cell 18650 formation steps and formation processes from lithium battery manufacturers

　　Lithium battery manufacturers provide popular science about the formation steps and processes of lithium-ion batteries. Lithium-ion batteries have the characteristics of high energy density, long cycle life and no memory effect, and are widely used in consumer goods, energy storage, electric vehicles and other fields. As the battery capacity increases, the compaction density of the pole pieces increases, the amount of electrolyte injection increases, and infiltration becomes difficult, which puts forward higher requirements for the formation process. Next, lithium battery manufacturers will popularize the formation steps and processes of lithium-ion batteries.

　　What is battery cell 18650 formation

　　battery cell 18650 formation refers to the process of charging a battery cell 18650 for the first time in order to make the battery electrochemically active. The formation is to form a layer of solid electrolyte interface film (SEI film) on the surface of the negative electrode. The SEI film has solid electrolyte properties and is an electronic insulator. However, this SEI film is an excellent conductor of Li+, and Li+ can freely pass through the SEI film. The main components of the SEI membrane are Li2CO3, LiF, LiOH, ROCO2Li, ROLi and other substances. The quality of the SEI film is closely related to the formation process. If the formation system is not good, a high-quality SEI film cannot be formed, which will adversely affect the cycle life and electrochemical performance of the battery.

　　The formation process can activate the positive and negative active materials of the battery cell 18650 to perform electrochemical reactions. At the same time, the film-forming components of the electrolyte form a solid electrolyte interface film (SEI film) on the surface of the negative electrode, effectively preventing the reaction between the solvent and the negative active material, allowing lithium ions to By performing disembedding. The excellent formation state of lithium-ion batteries directly affects the battery's negative electrode interface, capacity development, self-discharge, cycle performance, safety performance, etc.

　　battery cell 18650 formation steps

　　Step ①: Electrons are transferred from the current collector-conducting agent-graphite particles to point A where the SEI film is to be formed;

　　Step ②: The solvated lithium ions, wrapped in the solvent, diffuse from the positive electrode to point B on the surface of the SEI film being formed;

　　Step ③: The electrons at point A diffuse to point B through the electron tunneling effect;

　　Step ④: The electrons that jump to point B react with lithium salt, solvated lithium ions, film-forming agents, etc., and continue to form an SEI film on the surface of the original SEI film, thereby increasing the thickness of the SEI film on the surface of the graphite particles, and finally forming a complete SEI. membrane.

　　battery cell 18650 formation process

　　During the first charging process of the lithium battery, Li+ is released from the positive electrode active material, passes through the electrolyte-separator-electrolyte, and is embedded between the layers of the negative electrode graphite material. During this process, electrons migrate from the positive electrode to the negative electrode along the peripheral circuit. At this time, due to the low potential of the lithium ions embedded in the graphite negative electrode, the electrons will first react with the electrolyte to generate an SEI film and some gases.

　　A few batteries swell during the storage stage. The reasons for the gas production may be: First, due to poor sealing performance of the battery, the infiltration of external moisture and air leads to a significant increase in CO2 in the gas, and a considerable amount of O2 and N2 appear at the same time. . At the same time, the penetration of water causes the generation of HF, which will destroy the SEI layer; secondly, the SEI layer formed for the first time is unstable and is destroyed during the storage stage. In order to repair the SEI layer, gases are released again, mainly hydrocarbon gases. .

　　As market demand continues to increase, manufacturing companies have higher and higher requirements for the production efficiency and quality of lithium-ion batteries. Lithium batteries have shortcomings when used in high-energy-density batteries. One-time injection is used, and the injection efficiency is low. The aging time after injection is short, and the electrolyte cannot be fully infiltrated. The electrolyte is easy to splash out during formation, corroding equipment and battery casings. It pollutes the environment, and pumping negative pressure during the formation process requires high equipment.

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