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Battery production process
Release Time2015-3-9 16:50:32     Sourceվ     Reading7192 times



                                             Battery production process



      Cathode slurry

      This is the cathode slurry mixing room. First, we mix the power with NMP in the mixing tank. And the NMP is added to the mixing tank in three times. Add more NMP to the mixing tank to adjust the slurry viscosity. Finally, transfer the slurry to the coating line after slurry sifting.


      Anode slurry

      This is the anode powder process. First, we mix CMC with water in that anode binder mixing room, and after weighing, the raw material is transferred into the mixing tank. Then, we add the anode binder solution to the mixing tank in 3 times. After that, we add the SBR for the final mixing. And then, we add more water to adjust the slurry viscosity. Next we sift the slurry in that sifting room. Finally, we transfer the finished slurry to the coating line.




      Coating

      Now, we are in coating line. We use back reverse coating. This is the slurry-mixing tank. The anode (Cathode) slurry is introduced to the coating header by pneumaticity from the mixing tank. The slurry is coated uniformly on the copper foil, then the solvent is evaporated in this oven. There are four temperature zones, they are independently controlled. Zone one sets at 55 degree C, zone two sets at 65 degree C, zone three sets at 80 degree C, zone four sets at 60 degree C. The speed of coating is 4 meters per minute.

      You see the slurry is dried. The electrode is wound to be a big roll and put into the oven. The time is more than 2 hours and temperature is set at 60 degree C.

      Throughout the coating, we use micrometer to measure the electrode thickness per about 15 minutes. We do this in order to keep the best consistency of the electrode.


      Electrode

      After coating we compress the electrode with this cylindering machine at about 7 meters per minute. Before compares we clean the electrode is wound to a big roll. We use micrometer to measure the compressed electrode thickness every 10 minutes. After compressing we cut the web into large pieces. We tape the cathode edge to prevent any possible internal short. The large electrode with edge taped is slit into smaller pieces. This is ultrasonic process that aluminum tabs are welded onto cathodes using ultrasonic weld machine. We tape the weld section to prevent any possible internal short. And finally, we clean the finished electrodes with vacuum and brush.


      Anode making

      In anode making process, we cut the nickel roll into certain length strips. At the mean time, we put a small piece of insulation tape to the tab in order to prevent any possible internal short. Then the prepared nickel tab is riveted on anode and pat plain. We also tape the rivet section to prevent any possible internal short. And finally, we clean the finished electrodes with vacuum and brush.


      Jelly roll

      This is Jelly roll, a manual winding process. In the course of Jelly roll, firstly, we place the separator in between central pins, press the foot switch to turn central pins about 120 degrees. Lastly, place the cathode to the edge of central pins. During the winding process, we apply tension by pressing the electrodes and the separator. We put the termination tape at the end.

      After Jelly roll, we check the short circuit, then form the Jelly roll by pressing, so that it is easier to insert the Jelly roll into the can.

 

      Control points:

1.   When winding to the end of the anode, covering the anode completely by the separator.

2.   In the whole process, it is the most important points to ensure the best alignment among the cathode, the anode and the separator for the Jelly roll. The separator has to cover the anode and the cathode, and the anode has to cover the cathode completely. These points are mainly checked before short checking.


      Taping & Inserting

      Put the tape on the two side of J/R, to prevent J/R being hurt in the insertion process.

      Put a piece of tape between cathode tab and J/R. Because anode electrode is wider than cathode electrode.

      Put the bottom tape.

      Insert the finished J/R into the can manually and then short circuit check by multi-meter.

      Spot welding Ni tab to cap.

      Ultrasonic welding the AL tab to cap using ultrasonic weld.

      We have the second spot welding to ensure the best contact between the tab and cap.

      Apply top insulator, to prevent Ni tab contacting with can.

      Final J/R insertion by the centrifuge.

      Can positioning by hand. Then check the cap in the suitable position, or the defects is put into red bin. Finally, short circuit check again to ensure that there be no internal short J/R flowing to next line.


                      

        


      Laser welding

      This is the Laser welding room. The first process is welding for the aluminum cap,specially connect the rivet with weld plate to prevent the cell impedance excursion.

      The second process is the Laser seam welding. In the process, it must ensure the intensity and airproof characters of the weld.

      After the cell is welded, we would perform the leak checking, the short circuit checking and the weighing checking.

      Oven drying electrolyte filling and storing

      This is the process of cells oven drying at 80 degrees for more than 12 hours under vacuum. After oven drying, the cells are transferred to the process of electrolyte filling through this channel. The electrolyte filling performs in dry room. The electrolyte is injected in two times so that it can be filled easily and sufficiently. When filling, vacuum first, then inject electrolyte. After that, we repeat vacuum and vent to room pressure several times. Finally the cell is put off at room pressure, then weigh the cell in order to check the amount of electrolyte. After weighing, we seal with tape onto the filling port to prevent the cells adsorbing water during storing.

      We store the filled cells for 24 hours at room temperature so that the electrolyte can be saturated sufficiently by the anodes and cathodes.


      Pre-charge and ball seal

      At first, we place a piece of absorb cotton above the filling port to absorb the excess electrolyte. This is the first process.

      The second process is performing a pre-charge at 0.1 C rate for 390 minutes.

      After the pre-charge, we take a voltage checking to the cell at once. If the voltage is lower than the standard, it needs to be re-charged.

      The fourth process is the ball seal. We must complete this process in 15 minutes.

      First, put the steel ball in the right place. Then, give pressure to it so that the steel ball can fill the filling port.

      In the whole process, we must make sure that the temperature and humidity are in the regular range.

 

      Finally, the process is cleaning to eliminate the electrolyte on the cell surface with acetone solvent.


      Aging and Formation

      This is the aging room. We age cells at 35~40 degree C for 7 days. The temperature is controlled by two heating instruments which are set at 38 degree C. Then we transfer cells to the testing workshop. First, we check the voltage of cells with multi-meters. According to voltage, we divide the cells into acceptable and defects. Formation is done at 1.0 Capacity rate for 140 minutes to 4.2 Voltage. After that, check thickness and impedance. At last, we transfer the acceptable to the storehouse.





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