Winding coating method for preparing conductive film layer of composite current collector

Abstract

The invention discloses a winding and coating method for preparing a conductive film layer of a composite current collector, which comprises the following steps of: enabling a flexible base film to pass through a plurality of working areas of vacuum winding and coating equipment, and respectively carrying out vacuum coating on the front surface and the back surface to prepare the conductive film layer; the vacuum coating process comprises the steps of preparing a compact seed film layer on the flexible base film through magnetron sputtering coating, and preparing a thickened film layer on the seed film layer on the flexible base film through evaporation coating, so that a conductive film layer is formed on the flexible base film. The magnetic control coating roller and the evaporation coating roller are both filled with cooling media, and the flexible base film is cooled during magnetic control sputtering coating and evaporation coating. By applying bias voltage, the flexible base film is tightly attached to the surfaces of the magnetic control coating roller and the evaporation coating roller when winding around the magnetic control coating roller and the evaporation coating roller, so that a better cooling effect is achieved. Auxiliary electric fields are respectively arranged in downstream side areas where the flexible base film passes through the magnetic control film coating roller and the evaporation film coating roller, and the auxiliary electric fields play a role in assisting the flexible base film to release the roller.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery preparation, and in particular relates to a winding coating method for preparing a composite current collector conductive film layer. Background Art

[0002] The electrode sheets in lithium batteries generally use copper and aluminum metal foils as current collectors. Limited by industrial technology, 6μm and 8μm have become bottlenecks in the thickness of copper foil and aluminum foil current collectors, respectively, restricting the improvement of lithium battery energy density. In recent years, composite current collectors with a layer of copper or aluminum metal film on the front and back of PET, PP and other polymer flexible films as substrates have attracted more and more attention in the industry. This composite current collector has the advantages of light weight and thin volume, which can bring the energy density of lithium batteries to a new level. In the composite current collector, in order to meet the conductivity requirements, the thickness of the metal film layer generally needs to reach more than 1μm.

[0003] In order to obtain a metal film layer with better quality, the industry currently generally uses vacuum evaporation winding coating technology for preparation. However, in order to make the coating film thicker, it is often necessary to increase the evaporation power or reduce the base film running speed to increase the film thickness, or to use the same roll of base film to implement multiple winding coating cycles to accumulate the target film thickness. In the former case, limited by the heat resistance of the flexible film, especially some ultra-thin flexible films that are more picky about the coating working temperature, the flexible film is prone to thermal deformation, thermal damage and other problems when preparing the metal film layer, which seriously affects the product quality and makes product production impossible. In the latter case, the base film needs to be removed between multiple coatings in the coating equipment, and the equipment has to destroy the vacuum environment and reinstall the base film, which not only reduces production efficiency, but also affects the quality of the coating, and thus affects the performance of the composite current collector. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a winding coating method for preparing a composite current collector conductive film layer. The winding coating method allows a flexible base film to pass through multiple working areas of a vacuum winding coating device through a winding system, and performs a vacuum coating process on the front and back sides of the flexible base film to prepare a conductive film layer; the vacuum coating process includes:

[0005] (1) In a magnetron sputtering working area, the flexible base film is sequentially wound around a magnetron front auxiliary roller, a magnetron coating roller, and a magnetron rear auxiliary roller; while winding around the magnetron coating roller, a dense seed film layer is prepared on the flexible base film by magnetron sputtering coating;

[0006] (2) In the evaporation coating working area, the flexible base film is sequentially wound around a pre-evaporation auxiliary roller, an evaporation coating roller, and a post-evaporation auxiliary roller; when winding around the evaporation coating roller, a thickened film layer is prepared on the seed film layer on the flexible base film by evaporation coating, thereby forming a conductive film layer on the flexible base film;

[0007] The seed film layer and the thickened film layer are both made of conductive materials.

[0008] Cooling medium is passed through the magnetron coating roller and the evaporation coating roller to cool the flexible base film during magnetron sputtering coating and evaporation coating.

[0009] Both the magnetron coating roller and the evaporation coating roller are biased, and at least one of the magnetron rear auxiliary roller, the evaporation front auxiliary roller, and the evaporation rear auxiliary roller is also biased, becoming a biased auxiliary roller. The bias polarity of the magnetron coating roller and the evaporation coating roller is the same, so that the surfaces of the magnetron coating roller and the evaporation coating roller are distributed with charges of the same polarity. The bias polarity of the biased auxiliary roller (i.e., the auxiliary roller with bias among the magnetron rear auxiliary roller, the evaporation front auxiliary roller, and the evaporation rear auxiliary roller) is opposite to the bias polarity of the magnetron coating roller and the evaporation coating roller. Since the surface of the flexible base film already has a conductive film layer in the seed film layer or thickened film layer stage when the flexible base film is wound around the magnetron rear auxiliary roller, the pre-evaporation auxiliary roller and the post-evaporation auxiliary roller, therefore, when the flexible base film is wound around the bias auxiliary roller, the bias on the bias auxiliary roller will cause the surface of the conductive film layer on the flexible base film in contact with the bias auxiliary roller to be distributed with charges of opposite polarity to the charges distributed on the surface of the magnetron coating roller and the evaporation coating roller. Under the action of the mutual attraction of the two charges of opposite polarity, the flexible base film is adsorbed when it is wound around the magnetron coating roller and the evaporation coating roller, and is closely attached to the surface of the magnetron coating roller and the evaporation coating roller, thereby obtaining a better cooling effect. In a more preferred embodiment, the magnetron rear auxiliary roller in the first magnetron sputtering working area in the vacuum winding coating equipment is at least a bias auxiliary roller. .

[0010] Auxiliary electric fields are respectively arranged in the downstream area where the flexible base film passes through the magnetron coating roller and the evaporation coating roller, and the polarity of the auxiliary electric field is the same as the bias polarity of the magnetron coating roller and the evaporation coating roller belt. The auxiliary electric field repel the charges with the same polarity on the magnetron coating roller and the evaporation coating roller, making the charge distribution density of the parts of the magnetron coating roller and the evaporation coating roller opposite to the auxiliary electric field become sparser, thereby weakening the adsorption effect of the parts on the flexible base film. Under this effect, when the flexible base film reaches the downstream area and needs to be separated from the magnetron coating roller or the evaporation coating roller, the adsorption effect between the flexible base film and the magnetron coating roller or the evaporation coating roller is weakened, the degree of adhesion is reduced, and the flexible base film is easier to be separated from the roller surface, and the auxiliary electric field plays an auxiliary role in removing the roller. The auxiliary electric field is a gradient electric field, and the gradient trend of the electric field intensity is gradually enhanced along the film direction of the flexible base film. The auxiliary electric field strength at the starting end of the downstream area is the smallest. As it extends from the starting end to the downstream area, the corresponding auxiliary electric field strength becomes stronger and stronger, and the repulsive effect on the same polarity charges on the magnetron coating roller or the evaporation coating roller becomes stronger and stronger, so the charge distribution density at the corresponding part of the place becomes more and more sparse, and the adsorption effect of the part on the flexible base film becomes weaker and weaker. At the pre-designed separation position where the flexible base film is separated from the magnetron coating roller or the evaporation coating roller, the adsorption effect of the magnetron coating roller or the evaporation coating roller on the flexible base film is the weakest, and the flexible base film is separated from the magnetron coating roller or the evaporation coating roller at this location.

[0011] A fitting sensor is provided downstream of the magnetron coating roller and the evaporation coating roller, and the fitting sensor monitors the degree of fitting between the flexible base film and the magnetron coating roller or the evaporation coating roller online. The sensor signal reflecting the degree of fitting detected by the fitting sensor corresponds to the tension of the flexible base film downstream of the magnetron coating roller or the evaporation coating roller. When the sensor signal increases, it means that the tension becomes larger, indicating that the flexible base film and the magnetron coating roller or the evaporation coating roller are more closely fitted, and the cooling effect is better; when the sensor signal decreases, it means that the tension becomes smaller, indicating that the degree of fitting between the flexible base film and the magnetron coating roller or the evaporation coating roller is reduced, and the cooling effect is also weakened. The vacuum winding coating equipment is provided with a control module. The auxiliary electric field is generated by an auxiliary electric field generating device, and the auxiliary electric field generating device includes a plurality of generating units arranged in a matrix manner. The control module can regulate each generating unit individually. The lamination sensor transmits the detected sensor signal reflecting the degree of lamination to the control module, and the control module performs online feedback control on the electric field strength and distribution of the auxiliary electric field according to the sensor signal. Specifically, when the lamination sensor transmits the detected sensor signal to the control module, the control module determines the degree of lamination between the flexible base film and the magnetron coating roller or the evaporation coating roller according to the received sensor signal, and sends a control instruction to the auxiliary electric field generating device, so that the auxiliary electric field generating device generates an auxiliary electric field with suitable electric field strength and distribution in the downstream area of ​​the magnetron coating roller or the evaporation coating roller, and forms an effective auxiliary roll-off effect for the flexible base film to be separated from the roller surface. When the degree of lamination between the flexible base film and the magnetron coating roller or the evaporation coating roller is too high or too low, the control module judges the situation and sends a control instruction to the auxiliary electric field generating device to adjust the electric field strength generated by certain generating units, increase or decrease the electric field strength of the auxiliary electric field, change the electric field distribution, and make the auxiliary electric field adapt to this situation, and still maintain an effective auxiliary roll-off effect for the flexible base film to be separated from the roller surface. The control module can also perform online feedback control on the auxiliary electric field according to the cooling effect of the flexible base film on the magnetron coating roller or the evaporation coating roller, and adjust the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated online by adjusting the electric field strength and distribution of the auxiliary electric field. When the control module determines that the flexible base film is not cooled enough, the control module sends a control instruction to the auxiliary electric field generating device to reduce the electric field strength and change the electric field distribution, so that the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated is delayed within an appropriate range compared to the original separation position, thereby enhancing the cooling effect of the flexible base film. When the control module determines that the flexible base film is overcooled, the control module sends a control instruction to the auxiliary electric field generating device to increase the electric field strength and change the electric field distribution, so that the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated is advanced within an appropriate range compared to the original separation position, thereby weakening the cooling effect of the flexible base film.

[0012] There are multiple magnetron targets arranged on the opposite side of the magnetron coating roller, and the magnetron sputtering coating in the magnetron sputtering working area is multi-target magnetron sputtering coating. The evaporation coating working area includes more than two evaporation coating rollers, and at least one evaporation boat is arranged under each evaporation coating roller. The arrangement of multiple evaporation coating rollers can realize the preparation of thicker film layers, especially the preparation of film layers above 1μm, within one vacuum coating process cycle under conventional or even faster film travel speed conditions.

[0013] The control module can also perform online feedback control on the bias of the magnetron coating roller, the evaporation coating roller and the bias auxiliary roller according to the sensor signal, and adjust the degree of contact between the flexible base film and the surface of the magnetron coating roller and the evaporation coating roller according to the specific process adjustment needs or when the vacuum coating process fluctuates, so as to obtain the required and stable cooling effect. The bias magnitudes of each magnetron coating roller, the evaporation coating roller and the bias auxiliary roller can be different. When the control module determines that the cooling effect of the flexible base film needs to be increased or decreased according to the received sensor signal, the control module will send a control instruction to the bias generating device to increase or decrease the bias of the magnetron coating roller and the bias auxiliary roller close thereto, or increase or decrease the bias of a certain evaporation coating roller and the bias auxiliary roller close thereto, and adjust the degree of contact between the flexible base film and the surface of the magnetron coating roller or the evaporation coating roller online, so that the flexible base film obtains the required and stable cooling effect.

[0014] By applying a bias voltage to the magnetron coating roller, the evaporation coating roller, and at least one of the magnetron post-coating roller, the evaporation pre-coating roller, and the evaporation post-coating roller, the magnetron coating roller and the evaporation coating roller have charges of opposite polarity on the surface of the conductive film layer on the flexible base film, the flexible base film can be more closely attached to the magnetron coating roller and the evaporation coating roller, and the flexible base film can be better cooled, overcoming the problem that the flexible film is prone to thermal deformation or even thermal damage when preparing a thicker film layer. However, the bias voltage and cooling effect are not the higher the better. When the flexible base film is overcooled, on the one hand, the lower film forming temperature is not conducive to the formation of a good microstructure of the film layer, and on the other hand, the lower surface temperature is prone to condensation, affecting the product quality. Therefore, the present invention performs online feedback control on the bias voltage and auxiliary electric field of each roller, so that the flexible base film obtains a suitable, required, and stable cooling effect, so that the winding vacuum coating process of preparing a thicker film layer on the flexible base film can be stably implemented, and a high-quality flexible composite current collector film product is obtained.

[0015] The inventors have found that when the bias causes the flexible base film to fit too closely to the coating roller, the following phenomena may easily occur when the flexible base film needs to be separated from the coating roller after passing through the coating roller: (1) when preparing a film layer on the back side of the flexible base film on which a film layer has been prepared on the front side, in order to resist the large adsorption force between the flexible base film and the coating roller, it is necessary to increase the pulling force on the flexible base film, which may easily cause the front film layer in adsorption contact with the roller surface to be adhered and torn, and the flexible base film to fall off; (2) when a large pulling force is applied to the flexible base film to make it fall off the coating roller, the flexible base film may be severely squeezed between the guide roller or the auxiliary roller downstream of the coating roller, causing the newly prepared film layer to be squeezed. (3) The position where the flexible base film is separated from the magnetron coating roller or the evaporation coating roller will be too late than the pre-planned separation position, so that the flexible base film after being removed from the roller and the flexible base film remaining on the roller surface will be bent at an acute angle. This acute angle will produce an irreversible crease on the flexible base film, which will cause the composite current collector to form a microscopic height difference. The thickness of the active material to be coated on the composite current collector is mostly less than 100 microns. Therefore, the existence of the height difference caused by this crease will cause the thickness of the active material coated near the crease to be uneven, resulting in different expansion volumes of the active material, which will bury the hidden dangers of accidents such as electrode sheet rupture. When the bias voltage is insufficient, not only will the flexible base film be unable to obtain sufficient cooling from the coating roller, but the flexible base film will also be separated from the magnetron coating roller or the evaporation coating roller in advance, causing local film speed fluctuations in the winding system, bringing uncertain fluctuation factors to the stability of the winding vacuum coating process, and thus affecting the stability of the quality of the flexible film product. During the vacuum winding coating process, the bias voltage fluctuation caused by certain uncertain factors will cause the bias voltage to increase or decrease abnormally, which will cause instability in the production process and affect the stability and consistency of the product. The present invention sets an auxiliary electric field with a gradually changing intensity to effectively assist the flexible base film to separate from the roller surface, thereby overcoming the above problems. At the same time, by online feedback control of the bias voltage and auxiliary electric field of each roller, the position where the flexible base film is separated from the magnetron coating roller or the evaporation coating roller is adjusted online. This multi-faceted technical effect not only enables the flexible base film to obtain a suitable, required, and stable cooling effect, but also ensures that the film layer quality on the flexible base film is not easily damaged. More importantly, this comprehensive effect enables the production process of winding vacuum coating to be continuously and stably implemented without being affected by process fluctuations such as bias voltage fluctuations caused by certain uncertain factors, thereby obtaining a highly consistent and high-quality flexible composite current collector film product.

[0016] When the vacuum coating process is performed on the reverse side of the flexible base film to prepare a conductive film layer, the outer surface layer of the magnetron coating roller in the corresponding magnetron sputtering working area and the evaporation coating roller in the evaporation coating working area is also provided with a heat-conductive electrical insulation layer, and the composition of the electrical insulation layer is one of aluminum oxide, aluminum nitride, silicon nitride, silicon oxide, zirconium oxide, and resin. The provision of the electrical insulation layer can prevent the charges distributed on the surface of the conductive film layer on the front side of the flexible base film from being neutralized with the charges on the magnetron coating roller and the evaporation coating roller for vacuum coating on the reverse side, and prevent the adsorption process between the flexible base film and the magnetron coating roller and the evaporation coating roller during the vacuum coating process on the front side from having adverse effects.

[0017] The conductive film layers prepared on the front and back surfaces of the flexible base film are respectively composed of at least one selected from copper, aluminum, silver, nickel, molybdenum, titanium, niobium, iron, zinc, stainless steel, graphene, carbon nanotubes, ketjen black, acetylene black, graphite powder and carbon fiber, with a thickness in the range of 0.3 to 1.5 μm; among the conductive film layers, the thickness of the seed film layer is in the range of 20 to 150 nm.

[0018] Beneficial effects of the present invention:

[0019] (1) A dense seed film layer with good organizational structure is first deposited on the surface of the flexible base film by magnetron sputtering coating with strong particle kinetic energy, and then a thicker thickening film layer is deposited on the seed film layer at a high speed by evaporation coating. The seed film layer with good organizational structure is conducive to the continued growth of the thickening film layer particles deposited on it along the organizational structure growth direction of the seed film layer, thereby forming a better film layer organization.

[0020] (2) Through multi-target magnetron sputtering coating and arranging multiple evaporation modules including evaporation coating rollers and evaporation boats in the evaporation coating working area, the flexible base film and the coating roller are more closely fitted by using online controllable bias voltage, so that the flexible base film can obtain a better and more stable cooling effect, thereby overcoming the problem that the flexible base film is prone to thermal deformation or even thermal damage when using higher coating power (including magnetron coating power and evaporation coating power). The preparation of a thicker film layer is achieved within one vacuum coating process cycle without reducing the film speed of the flexible base film.

[0021] (3) An auxiliary electric field with a gradually varying intensity is set to effectively assist the flexible base film in being detached from the roller surface, thereby overcoming the problem that the flexible base film is easily damaged when being separated from the coating roller due to a large bias voltage. At the same time, by performing online feedback control on the bias voltage and auxiliary electric field of each roller, the production process of preparing a thicker conductive film layer by winding vacuum coating can be implemented continuously and stably without being affected by process fluctuations such as bias voltage fluctuations caused by certain uncertain factors, thereby obtaining a highly consistent and high-quality flexible composite current collector film product. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic flow chart of a winding coating method for preparing a composite current collector conductive film layer.

[0023] Figure 2 It is a schematic diagram of the layout of the vacuum winding coating equipment involved in the winding coating method of the present invention.

[0024] The accompanying drawings are only used to schematically illustrate the technical solution of the present invention, and the proportions of the various parts in the accompanying drawings do not constitute a proportion limitation to the present invention.

[0025] Implementation

[0026] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0027] The terms "first", "second", "front", "back", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchangeable under appropriate circumstances.

[0028] The term "correspondence" may refer to an association relationship or a binding relationship. The correspondence between A and B means that there is an association relationship or a binding relationship between A and B.

[0029] The present invention provides a winding coating method for preparing a composite current collector conductive film layer, wherein a flexible base film is passed through multiple working areas of a vacuum winding coating device through a winding system, and a vacuum coating process is performed on the front and back sides of the flexible base film to prepare a conductive film layer. Figure 1 As shown, specifically including:

[0030] (1) The flexible base film passes through the first magnetron sputtering working area, and is wound around the magnetron front auxiliary roller, the magnetron coating roller, and the magnetron rear auxiliary roller in sequence; when winding around the magnetron coating roller, a dense seed film layer is prepared on the front side of the flexible base film by magnetron sputtering coating;

[0031] (2) the flexible base film passes through the first evaporation coating working area, and sequentially passes through the pre-evaporation coating auxiliary roller, the evaporation coating roller, and the post-evaporation coating auxiliary roller; when passing through the evaporation coating roller, a thickened film layer is prepared on the seed film layer on the front side of the flexible base film by evaporation coating, thereby forming a conductive film layer on the front side of the flexible base film;

[0032] (3) The flexible base film passes through the second magnetron sputtering working area, and a dense seed film layer is prepared on the reverse side of the flexible base film by magnetron sputtering coating;

[0033] (4) The flexible base film passes through the second evaporation coating working area, and a thickened film layer is prepared on the seed film layer on the back side of the flexible base film by evaporation coating, thereby forming a conductive film layer on the back side of the flexible base film.

[0034] The thickened film layer and the seed film layer together constitute a conductive film layer of the composite current collector.

[0035] The web-to-web coating method Figure 2 The vacuum winding coating equipment shown in FIG. Figure 2 As shown, the vacuum winding coating equipment includes a first magnetron sputtering working area 3, a first evaporation coating working area 8, a second magnetron sputtering working area 15 and a second evaporation coating working area 37. A plurality of magnetron targets 7 and 19 are arranged on the opposite sides of the magnetron coating rollers 5 and 17, respectively, and the magnetron sputtering coating in the first magnetron sputtering working area 3 and the second magnetron sputtering working area 15 is a multi-target magnetron sputtering coating. The first evaporation coating working area 8 and the second evaporation coating working area 37 respectively include evaporation coating rollers 10, 13 and 23, 27, and evaporation boats 20 and 21 are arranged below the evaporation coating rollers 10 and 13, respectively, and evaporation boats 25 and 29 are arranged below the evaporation coating rollers 23 and 27, respectively. The arrangement of multiple evaporation coating rollers can realize the preparation of a thicker film layer within one vacuum coating process cycle under conventional or even faster film travel speed conditions.

[0036] The flexible base film 2 from the unwinding roller 1 enters the first magnetron sputtering working area 3, where the flexible base film 2 is sequentially wound around the magnetron front auxiliary roller 4, the magnetron coating roller 5 and the magnetron rear auxiliary roller 6; when winding around the magnetron coating roller 5, a dense seed film layer is prepared on the front side of the flexible base film 2 by magnetron sputtering coating. Then the flexible base film 2 enters the first evaporation coating working area 8, and sequentially winds around the evaporation front auxiliary roller 9, the evaporation coating roller 10, the evaporation rear auxiliary roller 11, the evaporation front auxiliary roller 12, the evaporation coating roller 13 and the evaporation rear auxiliary roller 14; when winding around the evaporation coating rollers 10 and 13, a thickened film layer is prepared on the seed film layer on the front side of the flexible base film by evaporation coating, thereby forming a conductive film layer on the front side of the flexible base film. Then, the flexible base film 2 passes through the second magnetron sputtering working area 15, and is wound around the magnetron front auxiliary roller 16, the magnetron coating roller 17 and the magnetron rear auxiliary roller 18 in sequence, and a dense seed film layer is prepared on the back of the flexible base film by magnetron sputtering coating. Then, the flexible base film passes through the second evaporation coating working area 37, and is wound around the evaporation front auxiliary roller 22, the evaporation coating roller 23, the evaporation rear auxiliary roller 24, the evaporation front auxiliary roller 26, the evaporation coating roller 27 and the evaporation rear auxiliary roller 28 in sequence; when winding around the evaporation coating rollers 23 and 27, a thickened film layer is prepared on the seed film layer on the back of the flexible base film by evaporation coating, thereby forming a conductive film layer on the back of the flexible base film. Finally, the flexible base film with conductive film layers on both the front and back sides is wound up by the winding roller 36.

[0037] The flexible base film is turned over when passing through the guide rollers in the first evaporation coating working area 8 and the second magnetron sputtering working area 15, so that a conductive film layer can be prepared on the front and back sides of the flexible base film within one process cycle of the vacuum winding coating equipment, thereby avoiding the situation where the flexible base film roll that needs to prepare film layers on both sides is exposed to the atmosphere between two process cycles, thereby ensuring the quality of the thin film product.

[0038] Cooling medium is passed through the magnetron coating rollers 5 and 17 and the evaporation coating rollers 10, 13, 23 and 27 to cool the flexible base film during magnetron sputtering coating and evaporation coating.

[0039] The magnetron coating rollers 5 and 17, and the evaporation coating rollers 10, 13, 23 and 27 are all biased. The magnetron rear auxiliary rollers 6 and 18 are also biased and are bias auxiliary rollers.

[0040] The bias polarity of the magnetron coating roller and the evaporation coating roller is the same, so that the surfaces of the magnetron coating roller and the evaporation coating roller are distributed with charges of the same polarity. The bias polarity of the bias auxiliary roller (i.e., the magnetron rear auxiliary rollers 6 and 18) is opposite to the bias polarity of the magnetron coating roller and the evaporation coating roller. When the flexible base film is wound around the bias auxiliary roller, the bias on the bias auxiliary roller causes the surface of the conductive film layer already existing on the flexible base film to be distributed with charges of opposite polarity to the charges distributed on the surfaces of the magnetron coating roller and the evaporation coating roller. Under the mutual attraction of the two charges of opposite polarity, the flexible base film is adsorbed when it is wound around the magnetron coating roller and the evaporation coating roller, and fits tightly with the surfaces of the magnetron coating roller and the evaporation coating roller, thereby obtaining a better cooling effect.

[0041] Auxiliary electric fields are respectively arranged in the downstream area where the flexible base film passes through the magnetron coating roller and the evaporation coating roller, and the polarity of the auxiliary electric field is the same as the bias polarity of the magnetron coating roller and the evaporation coating roller belt. The auxiliary electric field repel the charges with the same polarity on the magnetron coating roller and the evaporation coating roller, making the charge distribution density of the parts of the magnetron coating roller and the evaporation coating roller opposite to the auxiliary electric field become sparser, thereby weakening the adsorption effect of the parts on the flexible base film. Under this effect, when the flexible base film reaches the downstream area and needs to be separated from the magnetron coating roller or the evaporation coating roller, the adsorption effect between the flexible base film and the magnetron coating roller or the evaporation coating roller is weakened, the degree of adhesion is reduced, and the flexible base film is easier to be separated from the roller surface, and the auxiliary electric field plays an auxiliary role in removing the roller. The auxiliary electric field is a gradient electric field, and the gradient trend of the electric field intensity is gradually enhanced along the film direction of the flexible base film. The auxiliary electric field strength at the starting end of the downstream area is the smallest. As it extends from the starting end to the downstream area, the corresponding auxiliary electric field strength becomes stronger and stronger, and the repulsive effect on the same polarity charges on the magnetron coating roller or the evaporation coating roller becomes stronger and stronger, so the charge distribution density at the corresponding part of the place becomes more and more sparse, and the adsorption effect of the part on the flexible base film becomes weaker and weaker. At the pre-designed separation position where the flexible base film is separated from the magnetron coating roller or the evaporation coating roller, the adsorption effect of the magnetron coating roller or the evaporation coating roller on the flexible base film is the weakest, and the flexible base film is separated from the magnetron coating roller or the evaporation coating roller at this location.

[0042] A fitting sensor is provided downstream of the magnetron coating roller and the evaporation coating roller, and the fitting sensor monitors the degree of fitting between the flexible base film and the magnetron coating roller or the evaporation coating roller online. The sensor signal reflecting the degree of fitting detected by the fitting sensor corresponds to the tension of the flexible base film downstream of the magnetron coating roller or the evaporation coating roller. When the sensor signal increases, it means that the tension becomes larger, indicating that the flexible base film and the magnetron coating roller or the evaporation coating roller are more closely fitted, and the cooling effect is better; when the sensor signal decreases, it means that the tension becomes smaller, indicating that the degree of fitting between the flexible base film and the magnetron coating roller or the evaporation coating roller is reduced, and the cooling effect is also weakened. The vacuum winding coating equipment is provided with a control module. The auxiliary electric field is generated by auxiliary electric field generating devices 30, 31, 32, 33, 34 and 35, and the auxiliary electric field generating device includes a plurality of generating units arranged in a matrix manner. The control module can regulate each generating unit separately. The lamination sensor transmits the detected sensor signal reflecting the degree of lamination to the control module, and the control module performs online feedback control on the electric field strength and distribution of the auxiliary electric field according to the sensor signal. Specifically, when the lamination sensor transmits the detected sensor signal to the control module, the control module determines the degree of lamination between the flexible base film and the magnetron coating roller or the evaporation coating roller according to the received sensor signal, and sends a control instruction to the auxiliary electric field generating device, so that the auxiliary electric field generating device generates an auxiliary electric field with suitable electric field strength and distribution in the downstream area of ​​the magnetron coating roller or the evaporation coating roller, and forms an effective auxiliary roll-off effect for the flexible base film to be separated from the roller surface. When the degree of lamination between the flexible base film and the magnetron coating roller or the evaporation coating roller is too high or too low, the control module judges the situation and sends a control instruction to the auxiliary electric field generating device to adjust the electric field strength generated by certain generating units, increase or decrease the electric field strength of the auxiliary electric field, change the electric field distribution, and make the auxiliary electric field adapt to this situation, and still maintain an effective auxiliary roll-off effect for the flexible base film to be separated from the roller surface. The control module can also perform online feedback control on the auxiliary electric field according to the cooling effect of the flexible base film on the magnetron coating roller or the evaporation coating roller, and adjust the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated online by adjusting the electric field strength and distribution of the auxiliary electric field. When the control module determines that the flexible base film is not cooled enough, the control module sends a control instruction to the auxiliary electric field generating device to reduce the electric field strength and change the electric field distribution, so that the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated is delayed within an appropriate range compared to the original separation position, thereby enhancing the cooling effect of the flexible base film. When the control module determines that the flexible base film is overcooled, the control module sends a control instruction to the auxiliary electric field generating device to increase the electric field strength and change the electric field distribution, so that the position where the flexible base film and the magnetron coating roller or the evaporation coating roller are separated is advanced within an appropriate range compared to the original separation position, thereby weakening the cooling effect of the flexible base film.

[0043] The control module can also perform online feedback control on the bias voltage of the magnetron coating rollers 5 and 17, the magnetron rear auxiliary rollers 6 and 18, and the evaporation coating rollers 10, 13, 23 and 27 according to the sensor signal, and adjust the degree of contact between the flexible base film and the surface of the magnetron coating roller and the evaporation coating roller according to the specific process adjustment needs or when the vacuum coating process fluctuates, so as to obtain the required and stable cooling effect. The bias voltages of the magnetron coating rollers, the magnetron rear auxiliary rollers and the evaporation coating rollers can be different. When the control module determines that the cooling effect of the flexible base film needs to be improved or reduced according to the received sensor signal, the control module will send a control instruction to the bias generating device to increase or reduce the bias voltage of the magnetron coating roller and the magnetron rear auxiliary roller close thereto, or increase or reduce the bias voltage of a certain evaporation coating roller and the magnetron rear auxiliary roller close thereto, and adjust the degree of contact between the flexible base film and the surface of the magnetron coating roller or the evaporation coating roller online, so that the flexible base film obtains the required and stable cooling effect.

[0044] By applying bias to the magnetron coating roller, the magnetron rear auxiliary roller and the evaporation coating roller, the magnetron coating roller and the evaporation coating roller have charges of opposite polarity to the surface of the conductive film layer on the flexible base film, so that the flexible base film can be more closely attached to the magnetron coating roller and the evaporation coating roller, and the flexible base film can be better cooled, overcoming the problem that the flexible film is prone to thermal deformation or even thermal damage when preparing a thicker film layer. However, the higher the bias and cooling effect, the better. When the flexible base film is overcooled, on the one hand, the lower film forming temperature is not conducive to the formation of a good microstructure of the film layer, and on the other hand, the lower surface temperature is prone to condensation, affecting the product quality. Therefore, the present invention performs online feedback control on the bias and auxiliary electric field of each roller, so that the flexible base film obtains a suitable, required and stable cooling effect, so that the winding vacuum coating process of preparing a thicker film layer on the flexible base film can be stably implemented, and a high-quality flexible composite current collector film product is obtained.

[0045] When the vacuum coating process is performed on the reverse side of the flexible base film to prepare a conductive film layer, the outer surface layers of the magnetron coating roller 17 in the second magnetron sputtering working area and the evaporation coating rollers 23 and 27 in the second evaporation coating working area are also provided with heat-conductive electrical insulation layers 40, 39 and 38, respectively. The composition of the electrical insulation layer is one of aluminum oxide, aluminum nitride, silicon nitride, silicon oxide, zirconium oxide, and resin. The provision of the electrical insulation layer can prevent the charges distributed on the surface of the conductive film layer on the front side of the flexible base film from being neutralized with the charges on the magnetron coating roller and the evaporation coating roller for vacuum coating on the reverse side, and prevent the adsorption process between the flexible base film and the magnetron coating roller and the evaporation coating roller during the vacuum coating process on the front side from having an adverse effect.

[0046] The conductive film layers prepared on the front and back surfaces of the flexible base film are respectively composed of at least one selected from copper, aluminum, silver, nickel, molybdenum, titanium, niobium, iron, zinc, stainless steel, graphene, carbon nanotubes, ketjen black, acetylene black, graphite powder and carbon fiber, with a thickness in the range of 0.3 to 1.5 μm; among the conductive film layers, the thickness of the seed film layer is in the range of 20 to 150 nm.

Claims

1. A winding coating method for preparing a composite current collector conductive film layer, characterized in that: The flexible base film is passed through multiple working areas of the vacuum winding coating equipment through the winding system, and the vacuum coating process is performed on the front and back sides of the flexible base film to prepare a conductive film layer. The vacuum coating process includes: (1) In a magnetron sputtering working area, the flexible base film is sequentially wound around a magnetron front auxiliary roller, a magnetron coating roller, and a magnetron rear auxiliary roller; while winding around the magnetron coating roller, a dense seed film layer is prepared on the flexible base film by magnetron sputtering coating; (2) In the evaporation coating working area, the flexible base film is sequentially wound around a pre-evaporation auxiliary roller, an evaporation coating roller, and a post-evaporation auxiliary roller; when winding around the evaporation coating roller, a thickened film layer is prepared on the seed film layer on the flexible base film by evaporation coating, thereby forming a conductive film layer on the flexible base film; There is cooling medium in both the magnetron sputtering coating roller and the evaporation coating roller to cool the flexible base film during magnetron sputtering coating and evaporation coating; Both the magnetron coating roller and the evaporation coating roller are biased, and at least one of the magnetron rear auxiliary roller, the evaporation front auxiliary roller and the evaporation rear auxiliary roller is also biased to become a bias auxiliary roller. The bias makes the flexible base film closely fit with the surface of the magnetron coating roller and the evaporation coating roller when it passes through the magnetron coating roller and the evaporation coating roller, so as to obtain a better cooling effect; Auxiliary electric fields are respectively arranged in the downstream area where the flexible base film passes around the magnetron coating roller and the evaporation coating roller; when the flexible base film reaches the downstream area and needs to separate from the magnetron coating roller or the evaporation coating roller, the auxiliary electric field plays an auxiliary role in removing the roller.

2. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: The bias polarity of the magnetron coating roller and the evaporation coating roller is the same, and the bias polarity of the bias auxiliary roller is opposite to the bias polarity of the magnetron coating roller and the evaporation coating roller.

3. The winding coating method for preparing a composite current collector conductive film layer according to claim 2, characterized in that: The polarity of the auxiliary electric field is the same as the bias polarity of the magnetron coating roller and the evaporation coating roller belt.

4. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: The auxiliary electric field is a gradient electric field, and the gradient trend of the electric field intensity is that it gradually increases along the film direction of the flexible base film.

5. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: A fitting sensor is arranged downstream of the magnetron coating roller and the evaporation coating roller, and the fitting sensor monitors the degree of fitting between the flexible base film and the magnetron coating roller or the evaporation coating roller.

6. The winding coating method for preparing a composite current collector conductive film layer according to claim 5, characterized in that: The vacuum winding coating equipment is provided with a control module; the bonding sensor transmits a sensing signal reflecting the degree of bonding to the control module, and the control module performs online feedback control on the electric field strength and distribution of the auxiliary electric field according to the sensing signal.

7. The winding coating method for preparing a composite current collector conductive film layer according to claim 6, characterized in that: The control module performs online feedback control on the bias voltage of the magnetron coating roller, the evaporation coating roller and the bias auxiliary roller according to the sensor signal.

8. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: A plurality of magnetron targets are arranged on the opposite side of the magnetron coating roller, and the magnetron sputtering coating in the magnetron sputtering working area is multi-target magnetron sputtering coating.

9. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: The evaporation coating working area includes more than two evaporation coating rollers, and at least one evaporation boat is arranged under each evaporation coating roller.

10. The winding coating method for preparing a composite current collector conductive film layer according to claim 1, characterized in that: The conductive film layers prepared on the front and back surfaces of the flexible base film are respectively composed of at least one selected from copper, aluminum, silver, nickel, molybdenum, titanium, niobium, iron, zinc, stainless steel, graphene, carbon nanotubes, ketjen black, acetylene black, graphite powder and carbon fiber, with a thickness in the range of 0.3 to 1.5 μm; among the conductive film layers, the thickness of the seed film layer is in the range of 20 to 150 nm.

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