Is The Cell Selected For Winding Or Be Laminated? The Market Has The Final Say.

- Aug 15, 2019-

Winding and lamination, such as the twin brothers battle, the market makes the desion.
China's new energy vehicle market, according to Tencent's marketing forecast, will maintain a compound growth rate of 40% in the next five years, with an annual sales volume of approximately 3 million units by 2022. The reason for the increase is the support of policy objectives, the improvement of vehicle battery quality and the increase in consumer acceptance. It can be inferred that the development of enterprises will be shifted from policy-oriented to market-driven.

Market-driven products mean that consumers can truly be customers, and the value of new energy vehicles is not worth buying. After field research, the main concern for customers to purchase new energy vehicles is the battery life, service life and safety. It also includes the completeness of charging pile distribution, charging time, second-hand resale and maintenance rate, distribution channels, and after-sales service.

To be straightforward, batteries are like a heart for new energy vehicles, and their performance and cost directly determine sales.

The most widely used lithium-ion battery in batteries, its performance is closely related to the process and manufacturing equipment. Especially in the core process winding and lamination involved, there is a rigid constraint on the mass production cost.

This paper will analyze and evaluate the process, equipment characteristics and vehicle development platform of the two processes of winding and lamination.

01 Winding and lamination process

In the winding process, after the pole piece diaphragm is made into a battery core, the electrodes at the edge positions on both sides have a large curvature, and during the charging and discharging process, the electrode is easily deformed and twisted, which may cause a decrease in battery performance and even a safety hazard. In addition, during the discharge process of the battery core, the current distribution on both sides is uneven, the voltage polarization is large, and the discharge voltage is unstable.

The lamination process is cumbersome, mainly because the pole piece and the diaphragm are cut into pieces. However, the pass rate of the pole piece is low, and the quality (section, burr, etc.) is difficult to maintain a high degree of consistency, and the alignment accuracy is insufficient.

In general, the winding efficiency is high and the process is simple, but the quality of the battery is not as good as the laminate. Although the lamination machine can improve efficiency through multiple stations, the overall cost is still high, the cell consistency is poor, and the competitiveness in the market is still weak, and only a small part can be used.

02 Winding equipment

The winding equipment includes positive and negative plates, automatic unwinding of the diaphragm, automatic dust removal, automatic winding of the positive and negative plates, paste termination tape, automatic blanking of the finished product, preloading and weighing, and QR code.

For battery manufacturers, the most important performance indicators for purchasing equipment are winding line speed, tension fluctuation control, alignment accuracy, machine qualification rate, time utilization rate, and failure rate.

For the current level of the winder, the linear speed can be 3m/s, the tension fluctuation control is ±5%, the alignment accuracy is ±2mm, the whole machine pass rate is ≥99%, the time utilization rate is ≥98%, and the failure rate is ≤1%. .

03 lamination equipment

Taking a thermal composite laminator as an example, the incoming material is a wound material having a cut ear. The process is cutting of positive and negative electrodes, thermal compounding, lamination, hot pressing and surrounding encapsulation.

The functions are automatic unwinding of the diaphragm diaphragm, automatic deviation correction, tension control, flattening and guiding of the ear, dust removal, pole cutting and feeding, thermal compounding, CCD positioning and lamination, encapsulation, weighing and so on.

The specific process is that the positive and negative electrodes and the diaphragm coil are automatically unwound by the servo motor, and then subjected to tension control and rectification, and are cut into fixed length single pieces by the pole piece cutting device. The thermal composite mechanism feeds the cut positive and negative single sheets and the double layer membrane into the oven for preheating, and then uses the Mylar membrane to protect the pole piece and the diaphragm. After the end, it is directly cold pressed and cut into independent lamination units.

The independent lamination unit is transported to the CCD photographing position, and after photographing and positioning, the position information is transmitted to the transport robot. The transport robot receives the command, and the suction cup absorbing lamination unit on the robot is stacked to the lamination station. After stacking to the required number of layers of the cell, it is directly transferred to the hot pressing platform to complete the hot pressing.

After hot pressing, the battery enters the rubberizing station for short-circuit test and is surrounded by rubber. Then it is weighed and bound on the surface labeling information. Finally, the NG is automatically removed, and the qualified products are retained.

The lamination machine level is currently the overall alignment accuracy of the battery core ± 0.5mm, product qualification rate ≥ 99.5%, time utilization rate ≥ 98%, failure rate ≤ 1%, lamination efficiency (five stations) at 4 pieces / s.

04 Summary

Both the laminator and the winder can produce large-capacity prismatic batteries. From the perspective of the vehicle development platform, the manufacture of square batteries in the future will match the chassis of the model.

At present, the most popular electric vehicle platform in the industry is the Volkswagen MEB platform. From this trend, the module and battery size of the battery are getting larger. In addition, Volkswagen's VDA-size batteries have reached the limit of the circumference of the needle. According to the cell size of the MEB platform, the length of the incoming core will increase.

If you look at energy density and cruising range alone, large modules and large batteries are indeed the trend, and laminated sheets are more dominant than winding. The essence of market competition is the price. If the lamination equipment can greatly reduce the cost, the profit is higher than the winding, and the replacement may be close at hand.