We analyzed above 10 various cutting technology and equipment, and make the comparison on the Automotive Power Battery Pole Slice Cutting Technology & Equipment

pic:  various cutting technology and equipment comparation

We analyzed above10 various cutting technology and equipment, and do the comparison on the Automotive Power Battery Pole Slice Cutting Technology & Equipment, get the conclusion that The laser die cutting technology and equipment of power battery electrode plate have obvious advantages, compared with traditional technology and equipment. The use of non-contact cutting, can ensure the quality of the pole slice after cutting, no burr and powder; The dimensional accuracy and consistency of the pole plate can also be guaranteed.

Various cutting technology and equipment comparison

1. Comparison of cutting technology

At the present stage, the cutting technology of power lithium battery electrode plate is judged by whether there are unacceptable burr and powder.

Power battery pole is coated with insulating material on the surface of the metal sheet, in the die cutting forming, the edge of the metal sheet is easy to produce burr, inevitably will appear powder. When the edge burr length exceeds the acceptable range, it will puncture the insulation layer on the pole sheet, cause short circuit, or even explosion, generate waste products in the subsequent process, and waste the cost of the subsequent process. The existing inspection process is as follows: after finishing cutting, the workers touch the edge of the pole piece one by one, wearing silk gloves. If the gloves hook wire, it indicates that the pole piece has burr. Discard the pole piece to avoid subsequent losses. The advantage of die cutting is that die cutting each pole piece, only need to replace the upper die cutting knife; Die cutting speed and high efficiency, especially rolling cutting, speed can reach 40r/s, 60 ~ 200PPM. Die cutting without intermediate waste, pole sheet no oxidation, cutting process does not produce extra dust, one-time input cost is low.

 Using high-precision fiber laser contactless machining to cut the electrode plate, almost no external force applied to the electrode plate coating, can significantly improve the existing method of the upper and lower blade cutting each other will inevitably produce burr and powder, can improve the safety of the battery, but also can improve the size consistency of the electrode plate. But laser cutting pole will more or less produce intermediate waste, cutting using gasification will inevitably produce soot, and in the cutting area will produce a certain amount of oxidation.

 2. Comparison of cutting equipment

Three kinds of pole slice cutting forming equipment on the whole structure principle is the same, are through feeding, cutting and cutting, complete the whole production cycle. Feeding includes all kinds of unwinding system, deviation correction system, tensioning system and conveying system; Blanking includes taking system and winding system. The main differences between the three polar slice cutting and forming equipment are the driving and cutting parts.

 Flat die cutting pole piece equipment is intermittent work, need to stop feeding, can not continuous fast die cutting, so the work efficiency is low. When pressing flat die cutting pole slice, the working edge of the die cutting knife participates in the die cutting work at the same time, which requires great pressure to cut through and separate the material. When the force is too large, the die cutting knife is easy to deformation and damage. Therefore, this kind of die cutting method can not die cutting large-size pole plate at present, the production efficiency is not high, its application is limited. Moreover, punching knives need die, replacement and maintenance is very inconvenient, especially the consistency of the pole size is greatly affected by the mechanical accuracy of the die, the sharpness of the blade of the die and the size of the pole burr are closely related.

Rotary die cutting pole chip equipment can be continuous feeding, cutting and cutting, high working efficiency. However, similar to the flat-pressing die cutting equipment, the edge of the pole piece is burr and the edge material falls off, and the tool die is also damaged quickly. Frequent replacement of the tool die or repair of the tool die cost is high; It is difficult to debug the replacement tool die, and the labor intensity of the operator is high. After replacing the tool die, the size of the electrode slices cut out is inconsistent, resulting in unstable battery capacity and unable to produce qualified battery electrode slices stably.

It can be seen from the analysis that although the use of die cutting forming equipment is high efficiency, one-time input cost is low, but the die cutting out of the pole will produce burr and powder, and after the sequence needs to increase the inspection burr process. Due to the frequent replacement or repair of the pole die, the size consistency of the pole die cannot be guaranteed, and the high maintenance cost in the later stage of equipment is not conducive to large-scale continuous production. All these shortcomings limit the production and application of automotive power batteries.

Power battery electrode laser cutting equipment is designed because of the shortcomings of the above die cutting forming equipment. The power battery electrode laser cutting equipment will not produce burr and almost no powder, save the time and cost of replacing or repairing the cutting die, improve the consistency of the electrode forming, ensure the stable quality of the electrode. And the cutting shape is arbitrary, not limited by the size and mold, it is very convenient to modify the sample. Although laser cutting power battery electrode equipment has many advantages compared with die cutting forming equipment, its one-time input cost is high in the early stage, and the feeding is intermittent, the processing efficiency needs to be improved. The comparison of each cutting process and equipment is shown in the table.

Pic 1 Power battery pole slice punching equipment composition system

At this stage, power lithium batteries are laminated structure, that is, the multiple layers (from a dozen to hundreds of sheets) of positive and negative electrode monomer staggered superimposed, and then placed in the positive and negative electrode between the insulation diaphragm, and then all the positive electrode ear pressed to the positive ear terminal, all the negative electrode ear pressed to the negative ear terminal, and finally the positive and negative electrode into the battery shell,

At this stage, power lithium batteries are laminated structure, that is, the multiple layers (from a dozen to hundreds of sheets) of positive and negative electrode monomer staggered superimposed, and then placed in the positive and negative electrode between the insulation diaphragm, and then all the positive electrode ear pressed to the positive ear terminal, all the negative electrode ear pressed to the negative ear terminal, and finally the positive and negative electrode into the battery shell, The power lithium battery is formed by forming and packaging. Although the production technology of domestic power lithium battery is becoming more and more mature, the preparation of positive and negative electrode pieces has always been one of the difficult problems in the production technology of automotive power battery, and it is also the technology and equipment problem that the major battery production enterprises and battery equipment manufacturers continue to explore.

 When preparing positive and negative electrode pieces of power lithium battery, specific equipment is needed to cut out the required shape and size of the electrode pieces, and the quality of the cutting of the electrode pieces (whether there are burr, powder, etc.) and the consistency of the electrode size directly affect the service life of the power battery and the quality of the battery. At present, most of the China domestic power battery production enterprises are using the traditional die cutting forming equipment to cut the power battery electrode, and some battery equipment enterprises and laser enterprises began to study the use of laser to non-contact cutting of automotive power lithium battery electrode. 

• Pole die cutting forming

1. Die cutting process of pole slice

Die cutting indentation processing technology, initially suitable for all kinds of printed matter surface processing. Die-cutting process can be printed matter or other paper products in accordance with the pre-designed graphics made into die-cutting knife plate for cutting, so that the shape of the printed matter is no longer limited to the straight edge of the right Angle. Die cutting is generally divided into two kinds:

(1) Steel knife die cutting is the most commonly used form of customized die cutting, the method is to make imitation "steel knife" according to customer specifications, to cut out parts by stamping.

(2) Rotary die cutting is mainly used for bulk coil cutting. Rotary die cutting is suitable for soft to semi-rigid materials, which are cut by pressing the material into a cylindrical die and the blade on a cylindrical anvil. This form is often used for gasket die cutting. The rotary die cutting has the advantages of low cost, fast processing, high output and low material loss.

At present, positive and negative electrode materials are uniformly coated on both sides of copper foil (negative electrode) and aluminum foil (positive electrode). Drawing on the printing die cutting processing technology, the mature power lithium battery electrode cutting is usually through the die cutting forming equipment will be cut into a specific shape. The die cutting equipment used on the production line of some domestic power battery production enterprises is mostly divided into two categories: one is punching, that is, flat pressing die cutting; One is rolling cutting, that is, circular die cutting.

2. Pole chip punching equipment

As shown in Figure 1, the punching equipment of the power battery pole piece is generally composed of the following parts: unwinding system, deviation correction system, tensioning system, driving system, cutting system, conveying system, material taking system and winding system.

 The unwinding system is set in the front end of the whole equipment, and the air expansion shaft of the fixed pole piece coil is driven by a variable frequency motor or magnetic coupler. A rectifying sensor is arranged at the back end of the unwinding system, and a rectifying actuator is arranged at the lower end of the unwinding system platform. The rectifying system is tested by the heel edge to keep the released pole strip moving forward in a straight line. Usually, you can purchase a complete set of correction system (including correction actuator, correction sensor and correction controller), such as German BST, E+L and other international well-known brands of correction system; Power battery equipment manufacturers can also assemble by themselves, such as using Keenes optical fiber sensor as the correction sensor, servo motor driven ball screw pair as the correction actuator, and design the correction controller by themselves. In addition, the unwinding system can be integrated with the rectifying system and designed into the form of a moving trolley, which is convenient to realize the moving and rapid replacement of the material coil.

Pic 2 Power battery electrode cutting equipment composition system

The tensioning system is usually positioned between the correction sensor and the front drive system.

The tensioning system is usually positioned between the correction sensor and the front drive system. At present, the general tensioning system has two forms: one is the spring + linear guide structure, the float roller is installed on the linear guide slide block, the pole sheet material belt is tensioned by the float roller, the float roller by the pole sheet material belt tension changes can slide along the linear guide, the sliding limit position is detected by the limit switch; Another form is the use of low friction cylinder + potentiometer, guide column will support the float roller, cylinder connected to the float roller, pole sheet material belt tensioned by the float roller. The float roller can slide along the guide column when the tension of the strip changes. The potentiometer outputs the signal linked with the position of the float roller and feeds back to the controller of the magnetic coupler of the unwinding system or to the converter. The coupling torque or unwinding speed can be changed immediately to maintain the constant tension of the pole strip.

 The driving system is arranged after the tensioning system, including the front and rear driving parts. The front drive and the rear drive are respectively placed before and after the cutting system, which is equivalent to the front drive part to feed the cutting system; After the driving part to pull from the cutting system, a feed a pull to form intermittent loading and unloading. Both front and rear driving systems adopt the form of opposing-roll motion, and the servo motor drives the driving roller together to drive the driven roller together to roll opposite to each other.

 The cutting system is arranged between the front and rear drive systems, including the electric press and the cutting die. A conveying system is provided under the front and rear drive system and cutting system.

 Conveying system adopts high toughness, high hardness circulating conveyor belt to support and transport the positive and negative electrode pieces of the power battery. Under the rotating motion of the active roller of the front and back driving system, the positive and negative electrode pieces of the power battery attached to it are transferred forward.

 The winding system is the same as the unwinding system, which collects the edge material of the finished product separated from the polar sheet material belt through the inflatable shaft. The collecting system is equivalent to collecting the finished pole pieces.

 Power battery electrode cutting equipment is to flush out the electrode plate in a flat way. When making single sheet forming electrode sheets, the coiled electrode sheet material is cut into single sheet forming electrode sheets by feeding system, correcting system and tensioning system through the driving system and conveying system into the electrode punching device. When the battery electrode is blanked in this way, the electrode material shall stay in the blanking zone for a period of time, and then start feeding after the blanking is finished. Because this kind of die - cutting process is intermittent, limiting the further improvement of production efficiency.

 3. Pole roll cutting equipment

As shown in Figure 2, the power battery pole piece hobbing equipment is generally composed of the following parts: unwinding system, deviation correction system, tensioning system, cutting system, conveying system, material taking system and waste system.

The power battery electrode cutting equipment is the same as the power battery electrode cutting equipment before and after the electrode processing, the difference is mainly in the cutting system. Compared with the power battery electrode punching equipment, the power battery electrode rolling equipment provides a high-speed die cutting process in the movement of two conjugate die cutting rollers. The power battery electrode roll cutting equipment comprises a die roll and a die roll parallel to each other. An appropriate gap is reserved between the die roll and the die roll and a die line for cutting pole pieces is provided on the surface of the die roll. This plays both the role of driving the feeding and the role of cutting the pole piece. 

The pole piece passes between the die roll and the die roll and is pressed by the die roll and the die roll. The die roll and the die roll roll opposite each other, and the rolling friction between the pole piece and the die roll and the die roll makes the pole piece move in the corresponding direction. At the same time, the pole piece is cut by the die line on the die roll. The shape of the die line can be designed according to the shape and size requirements of the pole piece after cutting. In order to facilitate the loading of electrode between die roll and die roll before cutting, and to control the clearance distance between die roll and die roll during the cutting of pole roll to adapt to the cutting of pole roll with different thickness, an adjustment device can also be set up to adjust the clearance distance between die roll and die roll.

The pole piece passes between the die roll and the die roll and is pressed by the die roll and the die roll. The die roll and the die roll roll opposite each other, and the rolling friction between the pole piece and the die roll and the die roll makes the pole piece move in the corresponding direction. At the same time, the pole piece is cut by the die line on the die roll. The shape of the die line can be designed according to the shape and size requirements of the pole piece after cutting. In order to facilitate the loading of electrode between die roll and die roll before cutting, and to control the clearance distance between die roll and die roll during the cutting of pole roll to adapt to the cutting of pole roll with different thickness, an adjustment device can also be set up to adjust the clearance distance between die roll and die roll.

pic 3. Component system of laser cutting equipment for power battery pole piece

• Laser cutting and forming of pole slice

1. Laser cutting technology of pole slice

At present, copper foil and aluminum foil are used as the base materials for automotive power lithium battery electrode sheets, and positive and negative electrode materials are evenly coated on both sides of the foil sheets. Among them, the thickness of copper foil is about 12mm, the thickness of aluminum foil is about 20mm, and the total thickness of the coated pole piece is about 150mm. For such a thin metal material with laser cutting, if you want to ensure that the cut through the pole piece, only gasification cutting way. Copper and aluminum are highly reflective materials to laser, belonging to laser more difficult to cut metal materials; The absorption rate of laser from metal materials will gradually increase with the decrease of wavelength. Therefore, the shorter the wavelength of laser used to cut aluminum foil and copper foil, the higher the cutting efficiency will be. The absorption efficiency of aluminum for 1064nm laser is about 5%, the absorption rate of CO2 laser at 10.6nm is about 1.7%, and the absorption efficiency of copper for 1064nm laser is even lower. Therefore, 1064nm laser is an ideal choice for cutting battery electrode pieces. At present, the industrial lasers capable of generating 1064nm laser include Nd:YAG laser and fiber laser. The output of Nd:YAG laser is generally multi-mode laser. The diameter of the focused spot after passing through the focusing mirror is large, and the large heat affected zone will be generated when cutting, which is not suitable for the cutting of the pole plate of the automobile power battery. The optical fiber laser and optical fiber laser cutting head are used to focus the diameter of the spot to 10 ~ 20mm. At this time, the power density of the laser at the spot reaches more than 108W/cm2. When the laser is focused on the positive and negative electrode material of the power battery, the material is immediately vaporized to complete the cutting.

 Fiber laser has the advantages of beam quality close to diffraction limit, high energy conversion efficiency, high stability, almost maintenance-free, long service life and small size, and has been widely used in laser cutting, welding and marking industrial manufacturing fields. Fiber laser cutting equipment uses fiber laser as a light source, laser output laser after collimation, beam expansion and focusing, the spot diameter will be focused to dozens of microns or even a few microns, very suitable for fine cutting. Fiber laser cutting adopts non-contact cutting mode, narrow slit, small heat-affected zone, smooth cutting edge and fast cutting speed, its many advantages just can meet the rapid cutting and quality improvement of automotive power battery pole slice, is an ideal alternative to the traditional die cutting process.

 2. Pole laser cutting equipment

As shown in Figure 3, the laser cutting equipment for power battery electrode pieces is generally composed of the following parts: unwinding system, deviation correction system, tensioning system, driving system, cutting system, adsorption system, conveying system, taking system and waste system.

Pole laser cutting equipment and pole die cutting equipment is the main difference in the cutting system. The pole strip from the tensioning system is sent to the front conveyor system through the drive system. The driving system is mainly composed of two parallel rubber rollers with adjustable spacing. Generally, the rubber roller is coated with a certain thickness of rubber on the surface of a solid steel rod. The rubber hardness is about 70 ~ 80 Shore, which can ensure sufficient friction on the roller to drive the pole piece forward without scratching the pole piece. The driving roller is driven by a servo motor and drives the driven roller to roll towards each other, and the rolling friction between the pole plate and the main and driven roller makes the pole plate move in the corresponding direction, so as to be transported to the front conveying system. The pole strip is transported to the cutting system by the front conveyor system for cutting and then to the next process by the back conveyor system. Pole laser cutting equipment conveying system with die cutting equipment, but the conveyor belt does not go through the middle of the cutting system but by the two sets of independent and interrelated system composition.

 The main difference between laser cutting equipment and die cutting equipment is that there is an adsorption system. Pole laser cutting equipment cutting system usually adopts gantry structure X/Y two-dimensional working platform. The laser cutting head is installed on the Y-axis drive system, and the adsorption system is installed under the gantry structure. When the electrode material belt transported by the front conveying system reaches the adsorption plate and is covered with the adsorption plate, the vacuum generator will pump the lower cavity of the adsorption plate into a vacuum so as to suck and hold the electrode plate flat. Then, the gantry structure X/Y two-dimensional working platform drives the laser cutting head to cut the set shape and size of the power battery pole piece through the X/Y linear motion and X/Y interpolation motion. Finally, the finished pole piece is removed through the feedstock system and the waste is transferred to the waste system through the after delivery system.

In summary

Compared with die cutting process and equipment, power battery electrode laser cutting process and equipment has obvious advantages. The non-contact cutting can ensure the quality of the electrode after cutting, no burr and powder, and the dimensional accuracy and consistency of the electrode can also be guaranteed. Although the one-time investment cost is relatively high, but long service life, late maintenance cost is low. If the production efficiency can be further improved and related process problems solved, the laser cutting technology and equipment of power battery electrode can not only improve the battery quality and performance of electric vehicles, but also have great market prospects and benefits.