The production process steps of lithium battery pack electrodes are as follows:

1. Cathode material composition: The cathode material is composed of active substances, conductive agents and binders. Generally, conductive agents need to be baked at about 120℃ for 8 hours, while the binder PVDF needs to be baked at about 80℃ for 8 hours. Whether active substances (such as LFP, NCM, etc.) need to be baked and dried depends on the state of the incoming materials and the process. The workshop requires a temperature of no more than 40℃ and a humidity of no more than 25%RH. If the wet process is adopted, the PVDF adhesive solution (solute PVDF, solution NMP) needs to be prepared in advance. The quality of the adhesive solution is of vital importance to the internal resistance and electrical performance of the battery. The factors affecting the application of glue include temperature and stirring speed. If the temperature is too high, the glue solution is prone to yellowing, which affects the adhesion. Excessively high stirring speed can easily damage the glue solution. The specific rotational speed depends on the size of the dispersion disc. Generally, the linear speed of the dispersion disc is between 10 and 15m/s. At this point, it is required that the circulating water in the stirring tank be turned on, with the temperature ≤30℃. When adding materials, pay attention to the sequence. First, add the active substances and conductive agents and stir slowly to mix them. Then add the gel solution. At the same time, strictly control the rotational speed of the equipment (generally, the dispersion linear speed should be above 17m/s, which depends on the performance of the equipment), the vacuum degree of stirring and the temperature. At this stage, it is necessary to regularly test the particle size and viscosity of the slurry. The conventional process requires a temperature of ≤30℃, a humidity of ≤25%RH, and a vacuum degree of ≤ -0.085MPa. After the slurry is mixed, it needs to be transferred out to the transfer tank or coating workshop. During the transfer, it should be sieved to filter out large particles, sediment and remove ferromagnetic substances. The process requirements are that the temperature is ≤40℃, the humidity is ≤25%RH, the screen mesh is ≤100 mesh and the particle size is ≤15um.

2. Negative electrode ingredients: The negative electrode system is mostly an aqueous mixing process (the solvent is deionized water). There is no need for drying of the incoming materials, but the conductivity of the deionized water should be ≤1us/cm. The workshop requires a temperature of no more than 40℃ and a humidity of no more than 25%RH. After the material confirmation is completed, prepare the glue solution first. Pour the graphite C and conductive agent into the mixer for dry mixing. It is recommended not to evacuate the vacuum. Start the circulating water, operate at a low speed of 15-20 RPM, and scrape the material for 2-3 cycles every 15 minutes. Finally, pour the SBR into the blender. It is recommended to blend it quickly at a low speed, 35-40 RPM at low speed and 1200-1800 RPM at high speed, for 10-20 minutes. The reference values are as follows: viscosity 2000-4000m Pa.s, particle size ≤35μm, solid content 40-70%, vacuum sieving ≤100 mesh. The specific process values may vary depending on the physical properties of the materials and the mixing process, etc. The workshop requires a temperature of no more than 30℃ and a humidity of no more than 25%RH.

3. Coating: Squeeze or spray the positive electrode slurry onto the AB surface of the aluminum current collector, with a single-sided density of 20-40 mg/cm² (NCM power type). The coating oven temperature is typically 4-8 sections or more, with each section baking temperature ranging from 95 to 120 ° C. Adjust according to actual needs to prevent cracking during baking, which may lead to transverse cracks and solvent dripping. The speed ratio of the transfer coating roller is 1.1-1.2. The gap is thinned by 20-30 μ m (to avoid excessive compaction at the TAB due to tailing and lithium plating during battery cycling). The moisture content of the coating is ≤2000-3000 PPM (specifically depending on the material and process). The positive electrode temperature in the workshop should be no more than 30℃ and the humidity no more than 25%. The negative electrode slurry is extruded or sprayed onto the AB surface of the copper current collector, with a single-sided density of approximately 10-15 mg/cm². The temperature of the coating oven is typically 4-8 sections or more, with each section baking at 80-105 ℃. Adjust according to actual needs to avoid cracking during baking and the occurrence of transverse cracks. The transfer roller speed ratio is 1.2-1.3, the gap is thinned by 10-15 μ m, the coating moisture content is ≤3000 PPM, the negative electrode temperature in the workshop is ≤30℃, and the humidity is ≤25%.

4. Roller pressing: After the positive electrode coating is dried, it is necessary to perform roller pressing within the process time, that is, to compact the electrode sheet. Currently, there are two processes: hot pressing and cold pressing. Hot pressing compaction is relatively higher than cold pressing, and the rebound rate is lower. The cold pressing process is relatively simple and easy to operate and control. For the double roller, the main focus should be on process values such as compaction density, rebound rate, and elongation. At the same time, it is necessary to ensure that there are no brittle chips, hard lumps, material dropping, or wavy edges on the surface of the electrode sheet, and no fractures are allowed at the gaps. At this time, the ambient temperature in the workshop is ≤23℃ and the humidity is ≤25%. The negative electrode sheet production is carried out in the same way as the positive electrode, but the process design is different. The workshop environment temperature is ≤23℃ and the humidity is ≤25%.

5. Slitting: After the positive electrode is fully rolled, slitting is carried out, that is, the entire electrode sheet is cut into small strips of the same width (corresponding to the battery height). When slitting, pay attention to the burrs on the electrode sheet. It is necessary to fully inspect the burrs in both the X and Y directions of the electrode sheet (with the help of a secondary dimension equipment). The length of the longitudinal burrs in the process Y should be ≤1/2 H of the separator thickness. The ambient temperature in the workshop is ≤23℃ and the dew point is ≤ -30 ℃. The slitting process of the negative electrode is similar to that of the positive electrode, and burrs in both the X and Y directions need to be controlled.

6. TAB welding and rubber coating: After slitting is completed, the positive electrode sheet needs to be dried (120℃), and then the aluminum tabs are welded and the TAB rubber coating process is carried out. At this time, the length and shaping width of the tabs need to be considered. Take the design of a certain lithium battery as an example. The design of exposed tabs mainly takes into account the reasonable fit when welding the cap and grooving the positive TAB. If the exposed tabs are too long, it is easy to cause a short circuit between the tabs and the steel shell during grooving. Too short tabs cannot weld caps. At present, ultrasonic welding heads can be either linear or point-shaped. In domestic processes, linear welding heads are more commonly used (considering overcurrent and welding strength). In addition, high-temperature glue is used to cover the tabs, mainly considering the risk of short circuits caused by metal burrs and metal debris. The ambient temperature in this workshop is ≤23℃, the dew point is ≤ -30 ℃, and the moisture content of the positive electrode is ≤500-1000ppm. The negative electrode sheet needs to be dried (105-110 ℃), then nickel tabs should be welded and the TAB rubber coating process should be carried out. The length and shaping width of the tabs also need to be considered. The ambient temperature in this workshop is ≤23℃, the dew point is ≤ -30 ℃, and the moisture content of the negative electrode is ≤500-1000ppm.