The production process of 18650 lithium battery cells.
The common 18650 lithium batteries are divided into lithium-ion batteries and lithium iron phosphate batteries. Lithium ion batteries have a nominal voltage of 3.7V and a charging cut-off voltage of 4.2V. Lithium iron phosphate batteries have a nominal voltage of 3.2V and a charging cut-off voltage of 3.6V, with a typical capacity of 1200mAh-3350mAh and a common capacity of 2200mAh-2600mAh.
The production process of
18650 lithium battery cells
18650 lithium battery is a commonly used lithium battery in electronic products, often used as a battery cell in laptop batteries. The definition of its model is: for example, 18650 type, which refers to a cylindrical battery with a diameter of 18mm and a length of 65mm.
Production process of 18650 lithium battery cells: coating
Firstly, starting from the coating process, large rolls of copper foil (yellow) and aluminum foil (silver) can be seen in this process. Aluminum foil is used to coat nickel cobalt manganese NCM ternary materials; On the contrary, copper foil is used to coat the negative electrode active material graphite; The white one is the diaphragm. Global lithium battery separators are mainly dominated by manufacturers such as Asahi, Celgard, SK, Toray, W-SCOP, and these foreign companies hold nearly 70% of the market share. The market share of Chinese separator enterprises is about 30%, and the independent localization of lithium battery separators is constantly breaking through. The capacity of the battery cell is obtained based on the blending ratio and area of these formulas.
The width of the positive and negative electrode materials coated in a whole roll is about 126mm. Next, they need to be cut into 7 small rolls with a width of about 18mm. Each roll will be evenly divided into several sections, and each section represents the material required for a battery cell. According to engineer Xu Gong from the battery cell factory, the current selling price of ternary positive electrode materials is 120000 yuan per ton, and each ton of material can be used to produce 50000 battery cells; The current daily production capacity of battery cells is 500000 units, requiring the use of 10 tons of ternary positive electrode materials, which alone costs 600000 yuan per day.
Automated machines will apply nickel strips and insulating high-temperature resistant Mylars to each section, and the next step is to weigh them in five levels: heavy, A1, A2, A3, and light. Similar to the selection of CPU wafers, the same batch of cutting processes can also result in different configurations. Based on different configurations, corresponding capacities can be divided and paired for shipment.
Production Process 2 of 18650 Lithium Battery Cells: Assembly
The sorted positive and negative electrodes will be fully automatically wrapped here, and the white material is the separator. 18650 lithium battery cells cannot function properly in this way, and electrolyte needs to be added as a medium to cause chemical reactions between the positive and negative electrodes. Only then can lithium ions migrate between the positive and negative electrodes, generating charge ions to output energy. Only then can the lithium battery be charged and discharged. After being automatically wrapped, it rolls directly onto the assembly line and enters the next assembly step to be loaded into the steel shell.
The steel shell is formed by integral stamping with a thickness of less than 1mm, so high requirements are placed on the strength and quality of the steel. This 18650 lithium battery cell factory uses imported Korean steel materials.
This step connects the negative electrode lug to the bottom of the steel shell by spot welding. Ensure spot welding accuracy and product quality. The spot welding machine cannot weld the bottom of the steel shell. The assembly girl has a copper nail in her hand. First, insert it into the bottom through the reserved small hole, then put it into the spot welding machine, click it, and the negative electrode is connected to the bottom of the steel shell with a nickel strip.
The electrolyte is injected into a glove box filled with inert gas argon, and the oxygen concentration inside the glove box must be below 10ppm to prevent electrode oxidation. The electrolyte argon gas is input into the sealed box through a circulating purification device, which contains catalyst and reducing agent hydrogen gas. Oxygen can be removed by the hydrogen oxygen reaction to generate water. At the same time, the desiccant in the device absorbs moisture to ensure a dry atmosphere inside the box.
The battery cells injected with electrolyte have been laser welded to integrate the cap with the steel shell. Rows of neat and orderly stacking, ready to go. A new 18650 lithium battery cell was born in this way. Each battery cell needs to be fitted with a "new clothing" PVC sleeve classified by capacity. Different capacities correspond to different PVC envelopes.
Production process three of 18650
lithium battery cells: initial charging and testing
After injecting electrolyte, 18650 lithium battery cells have not actually stored electricity, and the state of the positive and negative electrode surfaces has not reached stability at this time. They must be charged for the first time before they can be used normally, which is called "formation". When charging for the first time, additional power needs to be added to create a protective film on the electrode surface, which is the secret of low self discharge in lithium-ion batteries. Meanwhile, the properties of the protective film also affect the performance and lifespan of the battery. Therefore, the chemical conversion process is very important. The transformation is completed using a separate container.
Battery cells are chemicals, and in order to ensure safety and longevity, they need to be paired and packaged in boxes of 200 before leaving the factory. Ensure consistency in three aspects: consistent capacity, consistent internal resistance, and consistent voltage. Only in this way can we leave the factory normally, otherwise we will be relegated to the cold palace and become B-class or C-class battery cells.
Internal structure of 18650 lithium battery cells
Lithium battery positive electrode
The 18650 lithium battery is wrapped in a metal shell on the outside, and if the shell is damaged, the battery cells inside can be seen
Negative pole of lithium battery cell
Both the negative and positive electrodes of the battery cell have blue plastic insulation pads
Upon disassembling it, we discovered that the cylindrical 18650 battery cell is wrapped in an all metal casing, which provides excellent protection for the internal material and prevents leakage from occurring.
Inside the battery cell, the thin film is soaked in electrolyte
The 18650 lithium battery cell is composed of a roll of thin film inside, with positive and negative electrodes designed at both ends of the cell. The internal thin film is a specially formed polymer film with a microporous structure design, which allows lithium ions to freely shuttle through it.
