A lithium-ion battery is mainly composed of four parts: a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. Currently, the most commonly used lithium-ion batteries on the market are lithium iron phosphate batteries and ternary lithium-ion batteries. The raw materials for their positive electrodes differ significantly, and although their production processes are relatively similar, the process parameters need to be varied considerably.
The manufacturing process of lithium-ion batteries is relatively complex. The key production processes mainly include the stirring and coating stage of electrode fabrication, the winding and liquid injection stage of cell synthesis, and the formation, packaging, and testing stage. The value proportion is approximately (35~40%):(30~35)%:(30~35)%. The differences mainly come from different equipment suppliers and the difference in the import/domestic ratio. The basic process flow is the same, and although the value proportions may vary, they generally conform to this ratio.
Lithium-ion battery front-end manufacturing process: Electrode manufacturing is crucial to core battery performance
The result of the front-end process of lithium-ion batteries is the preparation of the positive and negative electrode sheets. The first step is stirring, which involves mixing the solid battery materials of the positive and negative electrodes evenly, adding a solvent, and stirring them into a slurry using a vacuum mixer. The stirring of the materials is the foundation of subsequent lithium battery processes, and high-quality stirring is the basis for the high-quality completion of subsequent coating and rolling processes.
Following coating and rolling processes comes slitting, which involves cutting the coated material. If burrs appear during slitting, they can pose safety hazards in subsequent assembly, electrolyte injection, and even during battery use. Therefore, front-end equipment in lithium battery production, such as mixers, coating machines, rolling mills, and slitting machines, are core machines in battery manufacturing and are crucial to the quality of the entire production line.
Lithium-ion battery mid-stage process flow: Efficiency first, winding precedes stacking.
In the manufacturing process of lithium-ion batteries, the mid-stage process is crucial for completing the battery formation. Key processes include sheet making, electrode winding, die cutting, cell winding and forming, and stacking. This is currently a highly competitive area among domestic equipment manufacturers, accounting for approximately 30% of the value of a lithium-ion battery production line.
Currently, there are two main manufacturing processes for power lithium-ion battery cells: winding and stacking. The corresponding battery structures are mainly cylindrical, prismatic, and pouch cells. Cylindrical and prismatic batteries are primarily produced using the winding process, while pouch cells are primarily produced using the stacking process. Because the winding process can achieve high-speed cell production through rotational speed, while the speed improvement of stacking technology is limited, the winding process is currently the dominant method for power lithium-ion batteries in China. Therefore, the shipment volume of winding machines currently exceeds that of stacking machines.
The core process of lithium battery back-end manufacturing is capacity testing and formation.
The main downstream processes of lithium battery manufacturing consist of four steps: capacity grading, formation, testing, and packaging/warehousing, accounting for approximately 35% of the production line's value. Formation and capacity grading are the most crucial downstream processes, activating and testing the formed batteries. Due to the long charge-discharge testing cycle, the equipment used in these processes has the highest value. The formation process is primarily used to activate the electrolyte-filled cells through charging, while the capacity grading process tests the battery's capacity and other electrical performance parameters after activation and performs grading. Formation and capacity grading are typically completed by automated capacity grading and formation systems, with formation machines and capacity grading machines used respectively.
Lithium-ion battery manufacturing process
Step 1 - Electrode Slurry Preparation
The key is to mix the electrode active material, binder, solvent, etc. together, and then stir and disperse them thoroughly to form a slurry.
Step 2 - Coating
The slurry prepared in the first step is uniformly coated onto the current collector (aluminum foil or copper foil, etc.) to a specified thickness, and the solvent is dried.
Step 3 - Electrode punching
The electrode sheet produced in the previous step is punched into the specified size and shape.
Step 4 - Stacking
The positive and negative electrode plates and the separator are assembled together, and after adhesive is applied, the electrode core is formed.
Step 5 - Assemble the pouch battery
The electrode core produced in the previous step is inserted into the pre-punched aluminum-plastic film, and the top and side seals are completed to form a soft-pack battery without liquid filling.
Step 6 - Injection
The specified amount of electrolyte is injected into the pouch cell. Of course, the cell must be baked and the electrolyte injection operation must be carried out in a low humidity environment, as excessive moisture content is undesirable.
