Recently, it has been reported that the industrialization progress of Tesla's 4680 battery has repeatedly lagged behind expectations, which may be due to the slow improvement of yield and the current battery performance not meeting expectations.
Data shows that since September 2021, the yield rate of Tesla 4680 batteries has increased from 20% to nearly 80%, and the yield rate of Tesla products has improved slowly, and the yield rate of 4680 batteries was still less than 92% by the end of last year. The slow ramp-up of 4680 yield is the main reason hindering its mass production.
Cell diagram
Some experts analyze the difficulties of mass production:
1. The whole tab is formed by cutting and folding technology.
Tesla adopts cutting and folding technology, which makes the surface of the tab undulating large, which is easy to cause poor internal resistance consistency due to the inconsistent contact degree of the tab, and the cutting of the electrode piece is easy to produce chips, which affects the product yield.
2. The welding process of the collector plate is complex.
After the whole tab is formed, it needs to be welded with the collector plate, and the welding amount increases from the traditional spot welding of two tabs to the full tab surface welding, and the welding process is complex. The all-tab and collector disc extending from the end face of the cylindrical battery core are all highly reflective metal materials, and the energy absorption rate of the welding laser is less than 10%, if the welding energy is increased, the welding temperature is very likely to have a heat shrinkage effect on the separator under the current collector, affecting the performance of the separator. And the pressure requirements are high when the collector plate and the kneaded end face are welded, the thickness of the upper collector plate is generally 0.2-0.6mm, the thickness of the lower whole tab is 4-12um, the thickness difference is too large, the pressure is too large during welding, it is easy to weld and perforate, the pressure is too small and easy to cause virtual welding, and the complex process affects the yield.
3. There are difficulties in dry electrode coating technology.
Affected by the size of the binder PTFE particles and the bonding effect, the uniformity of the dry electrode film formation is difficult to control, and the cathode active material has high electrochemical activity, which is prone to chemical changes during the rolling process, which hinders large-scale mass production, and the difficulties need to be overcome.
These difficulties may be solved with the new research and development of Yixinfeng's technical equipment!
That's right, this equipment is Yixinfeng's newly developed cylindrical laser cutting and winding machine, which is a fully motorized laser cutting and winding integrated equipment for the production of cylindrical cells.
Cylindrical laser cutting and winding machine
According to the requirements of the cell production process, the positive and negative electrode pieces are laser die-cut into the shape of the tabs (or all tabs), and then automatically wound into products together with the separator through the winding device. In the process of winding, the alignment of the battery cell and the tension of the pole piece and the diaphragm are controlled by the deviation correction control system and the tension control system, and the finished battery cell is subjected to the finishing glue, hot hole, pre-shaping of both ends of the cell (depending on the process), short circuit test, appearance size detection, defective product rejection, scanning code upload and other processes, and finally through the conveyor belt blanking.
Yixinfeng equipment produced products
Sample display
Device parameters
The device has a number of powerful features:
1. The automatic roll change is fast, and the success rate of glue preparation is high.
The roll change time is ≤30s, and the glue preparation is automatic, and the success rate of glue preparation is 100%.
2. Fast response and constant tension.
The tension of each section of the electrode diaphragm is controlled by servo motor, which responds quickly, and the tension fluctuation is controlled below 5%, and the tension sensor and closed-loop tension control can effectively control the winding tension and realize the function of setting and regulating the tension one by one.
3. High correction accuracy.
Five-level correction of the pole piece, overall deviation correction before the diaphragm roll, the guiding accuracy of traveling: 0.1~0.2mm, the correcting accuracy before rolling: 0.1mm.
4. The winding speed is fast, stable and controllable.
The equipment adopts a three-pin winding head turntable structure, and the winding motor adopts an electronic cam to pull the pole piece; It has the function of variable speed and variable tension winding, which can realize three modes of fixed-length winding, fixed-loop winding, and the position of the head and tail of the fixed pole piece, and the linear speed and speed fluctuation of ≤5% during normal winding; The maximum linear speed of the winding constant speed section ≥ 2.5m/s.
5. Prevent the wrinkle (bending) function of the tabs.
The detection of tab fold in the process and on the needle reel is realized by means of several tab and induction tab, and 100% detection and discharge can be detected and discharged when there is tab fold and angle in the pole core.
6. Automatic rejection of defects.
Positive and negative electrode pieces and diaphragm defective products single roll and rejection function, bad electrode piece, can be without diaphragm automatic single roll rejection, can also without diaphragm manual single roll rejection. The defective diaphragm is discharged manually by the reel needle, which saves good material and winding time for wide and long materials.
7. High die-cutting precision.
The shape and size accuracy of the tab is controlled within ±0.3mm; The accuracy of the spacing between the single tab and the set spacing is controlled within ±0.3mm, and the accuracy control of the width of the pole piece (from die-cut edge to slitting edge) ± less than 0.3mm; The accuracy control within 7000mm ± 2mm, and the accuracy control within 10000mm ±3mm.
(1) When the positive and negative electrode lasers cut the foil, the maximum size of the protruding foil burr (including welding slag and molten beads) is ≤ 10 μm, the heat affected area is ≤ 120 μm, and the target is 0;
(2) The maximum size of the dust splashed on the pole piece ≤ 10μm, the thickness of the melting edge < 3T (T = foil thickness), and the melting edge is smooth and nodulging (including the trajectory splicing point);
(3) Cut the dressing or alumina coating, and the edge of the dressing takes away the dressing (the amount of ablation of the cutting edge) ≤ 50μm.
8. Closed dust removal system.
The equipment is equipped with a dust removal mechanism at the upper and lower cutting positions, which collects the dust generated during the cutting of the pole piece and extracts it through the negative pressure pipeline; There is a cutting pole piece backing plate below the pole piece cutting, and the negative pressure dust removal function is provided below the backing plate to remove the dust generated after the pole piece is cut, and the design of the dust removal mechanism at the cutting position should completely avoid welding slag/molten beads splashing on the surface of the pole piece.
9. Independent automatic waste collection system.
The equipment has a waste collection fan, the positive and negative electrodes are collected independently, and the equipment does not stop when collecting waste; After the waste is cut, it directly enters the waste sealing pipeline, and the waste is extracted and compressed under negative pressure through the pipeline, and automatically collected; Negative pressure sucks up the cutting waste and the dust attached to the waste, filters the dust on the waste foil, and avoids the spread of waste dust to the workshop and causes environmental pollution.
10. Tab folding and kneading and bulldozing.
(1) The tabs are pre-folded and formed before the feeding coil, and the positive and negative guide foil wheels in the winding process are further folded and pressed in the direction of the winding direction, and the final bending angle of the tabs after pre-folding is ≥60°
(2) The contact surface between the flattening block of the pre-flattening mechanism and the tab is in the form of concave, and the concave angle of the multi-channel pre-flattening block increases sequentially, and the cell position alignment function is provided before the final flattening of the tab, so as to ensure the total height of the cell after the final flattening
At the same time, the production energy efficiency of this equipment reaches 15ppm, the yield rate of the equipment can reach more than 99% (excluding the defective material, the yield rate of the battery cell flowing to the next process is 100%), and the utilization rate of the equipment is also as high as more than 95%. It can be said that compared with the current market production technology level, it is a great improvement.
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Judging from the production video of the equipment, the battery winding process level of our equipment is also much higher than the industry standard. If it can be used in batches, it may be able to solve the problem of batch production of 4680 cylindrical batteries. Add new impetus to the development of the new energy battery industry.
Yixinfeng
Guangdong Yixinfeng Intelligent Equipment Co., Ltd. was established in 2009. It is a national specialized and special new "little giant" enterprise specializing in the manufacture of intelligent equipment, a national high-tech enterprise, a national high-tech enterprise, a Guangdong Province intelligent lithium battery equipment (Yixinfeng) Engineering Technology Center, a patent demonstration enterprise in Guangdong Province, a pilot multiplication enterprise in Dongguan City, and a small and medium-sized enterprise certified by the ISO9001-2015 quality management system system. Mold splitting machine (laser, hardware), die stacking machine, winding machine (square, cylindrical), high-speed slitting machine, high-speed stacking machine and other products.
Yixinfeng's main products and equipment: