Coating and drying method and device for battery pole piece

Abstract

The invention provides a coating and drying method and device for a battery pole piece, and particularly relates to the technical field of batteries. The coating and drying method comprises the following steps: a slurry preparation step: mixing and stirring an active material, a conductive agent and a binder to prepare slurry; a first coating step: coating the slurry on a first surface of a current collector so as to form a first coating on the first surface; and a first drying step: sequentially performing infrared preheating, hot air drying and infrared drying on the current collector coated with the first coating to obtain the pole piece. According to the coating drying method, the hot air convection drying time can be shortened, the drying uniformity is enhanced, and the problems of surface defects caused by too fast convection drying and excessive drying or low production efficiency caused by too slow drying are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery pole piece manufacturing, and in particular to a coating and drying method and equipment for battery pole pieces. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic products such as mobile phones, digital cameras, and laptops due to their advantages of high voltage, long life, high energy density, and low pollution. Lithium-ion batteries are composed of positive and negative electrodes, electrolytes, diaphragms, and shells. As the core components of lithium-ion batteries, the quality of positive and negative electrodes will directly affect battery performance.

[0003] The positive and negative electrodes of lithium-ion batteries need to be prepared through pulping, coating, rolling, slitting and other processes. Among them, coating and drying is one of the important processes that affect the quality of the electrodes. At present, the drying of battery electrodes usually adopts the mode of tunnel box hot air drying, which not only has high energy consumption and large space, but also causes defects such as curling and cracking of the coated electrodes. With the continuous development of lithium-ion battery technology, coating methods such as double-layer coating and thick coating have also put forward higher requirements for electrode drying, and traditional electrode drying methods can no longer meet the requirements.

[0004] Therefore, it is necessary to provide a coating and drying method and device for battery pole pieces to solve the above problems. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a coating and drying method and device for battery pole pieces to improve the problem of low production efficiency caused by surface defects of battery pole pieces due to too fast convection drying, excessive drying or too slow drying.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention provides a coating and drying method for battery pole pieces, the method comprising: a slurry preparation step, mixing and stirring an active material, a conductive agent and a binder to obtain a slurry; a first coating step, coating the slurry on a first surface of a current collector to form a first coating on the first surface; a first drying step, subjecting the current collector coated with the first coating to infrared preheating, hot air drying and infrared drying in sequence to obtain a pole piece.

[0007] In an example of the present invention, the first coating layer is preheated to a temperature of 55° C. to 75° C. by the infrared preheating, and then the hot air drying is performed.

[0008] In an example of the present invention, the hot air drying temperature in the first drying step is 80-115° C., and the weight loss rate of the electrode sheet after the hot air drying is 1-1.5%.

[0009] In one example of the present invention, the weight loss rate of the electrode sheet after infrared drying in the first drying step is 0.7-1.2%.

[0010] In one example of the present invention, a second coating step is further included after the first drying step, and the second coating step includes: coating the slurry on the second surface of the current collector to form a second coating on the second surface, wherein the first surface and the second surface are two surfaces of the current collector arranged opposite to each other along the thickness direction.

[0011] In one example of the present invention, the second coating step further includes a second drying step, in which the current collector coated with the second coating is subjected to infrared preheating, hot air drying and infrared drying in sequence to obtain a pole piece.

[0012] In one example of the present invention, in the second drying step, the second coating is preheated to a temperature of 60-80° C. by infrared, and then hot air drying is performed.

[0013] In one example of the present invention, the hot air drying temperature in the second drying step is 85-120° C., the weight loss rate of the electrode sheet after hot air drying is 0.8-1.2%, and the weight loss rate of the electrode sheet after infrared drying is 0.1-0.4%.

[0014] In one example of the present invention, the infrared preheating temperature in the second drying step is greater than the infrared preheating temperature in the first drying step; the hot air drying temperature in the second drying step is greater than the hot air drying temperature in the first drying step.

[0015] On the other hand, the present invention provides a coating and drying device for battery pole pieces, the coating and drying device comprising a conveying mechanism, a coating mechanism, a hot air drying device, an infrared preheating device and an infrared drying device; the coating mechanism is arranged on the conveying mechanism or beside the conveying mechanism to coat the slurry on the current collector on the conveying mechanism; the hot air drying device is arranged on one side of the coating mechanism and has a drying chamber for the conveying mechanism to enter; the infrared preheating device is arranged between the coating mechanism and the hot air drying device to preheat the current collector coated with slurry before entering the drying chamber; the infrared drying device is arranged on a side of the hot air drying device away from the infrared preheating device to heat and dry the current collector after drying in the drying chamber.

[0016] The battery pole piece of the present invention adopts a drying mode of infrared preheating, hot air drying and infrared drying, which increases the controllability of the pole piece drying process; infrared preheating is used before hot air drying, so that the middle area of ​​the pole piece coating is heated simultaneously inside and outside, increasing the uniformity of drying, and at the same time suppressing the fluctuation caused by the low-temperature pole piece coating entering the hot air drying box during hot air drying, thereby shortening the drying time; by controlling the hot air drying point, the generation of pole piece surface defects during the drying process can be avoided; after hot air drying, infrared heating is used to thoroughly dry the pole piece coating, thereby improving the overall drying efficiency and saving time and energy. The present invention adopts a composite drying mode of infrared preheating, hot air drying and infrared drying, which can suppress the problems of surface defects caused by excessive convection drying, excessive drying, or low production efficiency caused by excessive drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A flowchart of a coating and drying method for a battery electrode according to an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of the slurry preparation steps in the coating and drying method of the battery electrode of the present invention;

[0020] Figure 3 A flow chart of a coating and drying method for a battery electrode of the present invention in another embodiment;

[0021] Figure 4 It is a schematic structural diagram of a coating and drying device for battery electrodes in one embodiment of the present invention;

[0022] Figure 5 FIG. 1 is a schematic diagram of a coating and drying device for a battery electrode of the present invention when used in one embodiment.

[0023] Reference numerals

[0024] 1. stirring device; 2. slurry; 100. coating and drying device; 110. conveying mechanism; 120. coating mechanism; 130. infrared preheating device; 140. hot air drying device; 150. infrared drying device; 200. pole piece; 210. current collector; 220. coating. DETAILED DESCRIPTION

[0025] The following is an explanation of the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the features in the following embodiments and the embodiments can be combined with each other without conflict. It should also be understood that the terms used in the embodiments of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturers.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0027] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0028] As used herein, "plurality", "multiple", "multiple times", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0029] Herein, "preferred", "better" and "more preferred" are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of the present invention. If multiple "preferred" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "preferred" item is independent.

[0030] Herein, “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0031] In this article, when it comes to numerical ranges, unless otherwise specified, the distribution of optional values ​​within the numerical range is considered continuous and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, as well as every value between the two numerical endpoints. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined.

[0032] During the preparation of battery pole pieces, coating and drying is one of the important processes that affect the quality of pole pieces. At present, pole pieces are mostly dried by hot air convection, which has the following shortcomings: during the heating process, air needs to be used as a medium. First, the air is heated to a certain temperature, and then the heat is transferred to the pole piece by convection heat transfer, so the heating efficiency is low; after the wet film is coated and enters the oven, the heat conduction and surface solvent evaporation will absorb a lot of heat, causing local temperature fluctuations in the drying tunnel, which is not conducive to overall uniform drying; the characteristics of convection heat transfer determine that the pole piece is dried first from the edge to the middle, first from the surface to the inside, and in this process, it is easy to cause pole curling, "wet inside and dry outside" and other problems; when drying too fast, it is easy to cause cracking, adhesive floating and other problems, while drying too slowly affects production efficiency.

[0033] Based on this, the present invention provides a coating and drying method for a battery pole piece and a coating and drying device for implementing the method, which improves the problem of low production efficiency of the battery pole piece caused by surface defects caused by too fast convection drying, excessive drying, or too slow drying by adopting a composite drying mode of infrared preheating, hot air drying and infrared drying.

[0034] See also Figure 1 The method for preparing the dry electrode of the present invention comprises at least the following steps:

[0035] S1, a slurry preparation step, mixing and stirring the active material, the conductive agent and the binder to prepare a slurry;

[0036] S2, a first coating step, coating the slurry on a first surface of the current collector to form a first coating on the first surface;

[0037] S3, a first drying step, sequentially subjecting the current collector coated with the first coating layer to infrared preheating, hot air drying and infrared drying to obtain a single-sided electrode sheet;

[0038] The active material in step S1 is the main active substance participating in the electrochemical reaction in the battery pole piece, and the selection of the active material is related to the type of battery and the polarity of the pole piece. Taking lithium-ion batteries as an example, the active material of the positive pole piece is selected from the conventional lithium-insertable and deinsertable materials in the art. As an example, the positive electrode material can be selected from lithium-rich active materials such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, and ternary materials (lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide). The active material can be selected from any one of the above-listed materials, for example, lithium iron phosphate, or lithium nickel cobalt manganese oxide, etc.; any two or more combinations of the above-listed materials can also be selected, for example, a combination of lithium manganese oxide and lithium cobalt oxide, or a combination of lithium iron phosphate and lithium nickel cobalt manganese oxide, or a combination of lithium iron phosphate, lithium iron manganese phosphate and lithium nickel cobalt manganese oxide, etc. The active material of the negative electrode plate is selected from conventional negative electrode active materials that can embed and release lithium in the art. As an example, the negative electrode active material can be selected from artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, pyrolytic carbon, etc. The negative electrode active material can be selected from any one of the materials listed above, or a combination of any two or more of the materials listed above, for example, a combination of artificial graphite and hard carbon; or a combination of soft carbon and hard carbon; or a combination of artificial graphite, hard carbon and soft carbon, etc., which are not listed here one by one. When the active material is a combination of two or more materials, there is no restriction on the ratio between the components in the composition, and they can be mixed in any proportion.

[0039] In step S1, the conductive agent is mainly used to improve the electronic conductivity, ensure that the battery has good charge and discharge performance, and collect microcurrents between active materials and between active materials and current collectors to reduce the contact resistance of the battery and accelerate the movement rate of electrons. The conductive agent can also improve the processability of the electrode, promote the infiltration of the electrolyte into the electrode, and effectively improve the migration rate of lithium ions in the battery material, thereby improving the charge and discharge efficiency and service life of the battery. The conductive agent includes but is not limited to one or more of carbon black, acetylene black, carbon nanotubes, carbon fiber, and graphene, that is, the conductive agent can be any one of the materials listed above, or a combination of any two or more of the materials listed above. For example, the conductive agent is carbon black; or carbon nanotubes; or a combination of carbon black and acetylene black; or a combination of carbon fiber, acetylene black and graphene. It should be noted that when the conductive agent is a plurality of compositions, there is no restriction on the ratio between the components in the composition, and any proportion can be mixed.

[0040] The binder in step S1 is used to bond the active material particles and the active material particles to the current collector. The binder is selected from one or more mixtures of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, sodium carboxymethyl cellulose, and styrene-butadiene rubber. For example, a combination of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polytetrafluoroethylene, etc.

[0041] See also Figure 1 and Figure 2 , S1 slurry preparation step is to add the above-mentioned active materials, conductive agents and binders to the solvent in a certain proportion, mix them evenly in the stirring device 1, and obtain the required slurry 2 after adjusting the viscosity, defoaming, demagnetizing and filtering. Among them, when preparing the positive electrode slurry, the solvent can be selected from one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), deionized water and alcohol, preferably NMP; when preparing the negative electrode slurry, the solvent is selected from one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), deionized water and alcohol, preferably deionized water. The ratio between the active material, conductive agent, binder and solvent can be set according to the actual situation, and is not limited here.

[0042] See also Figure 1 , step S2 is to apply the slurry configured in step S1 on the substrate current collector. The current collector can be selected from materials known to those skilled in the art, for example, the positive electrode current collector is selected from aluminum foil, and the negative electrode current collector is selected from copper foil. The current collector has two oppositely arranged first and second surfaces in the thickness direction. During coating, the slurry is coated on at least one surface of the current collector, that is, the slurry can be coated on only one of the first and second surfaces, or on both surfaces. When the slurry is coated on both surfaces of the current collector, it is necessary to wait until the first coated surface is dry before coating the other surface. Step S2 is to coat the first surface of the current collector to form a first coating on the first surface of the current collector. The coating amount of the slurry during coating can be selected according to actual conditions. For example, the coating surface density of the positive electrode slurry during coating is 0.3g~0.4g / 1540.25mm 2 The single-sided coating thickness is 79μm to 124μm; the coating surface density of the negative electrode slurry is 0.114g to 0.167g / 1540.25mm 2 The single-sided coating thickness is 52μm to 75μm.

[0043] See also Figure 1, step S3 is to dry the first coating of step S2. The drying process is as follows: first, the current collector coated with the first coating is preheated by infrared to a temperature of 55°C to 75°C, for example, 55°C, 60°C, 70°C or 75°C, and then hot air drying is performed to remove most of the solvent in the first coating, and the degree of drying of the coating is controlled to be non-sticky to the roller and non-cracking; then infrared drying is used to dry the remaining solvent in the first coating. Among them, the temperature of hot air drying is 80 to 115°C, for example, 80°C, 100°C or 115°C, and the time of hot air drying varies depending on the type of positive and negative electrode materials, the solid content of the slurry, the production line layout, etc. Taking the positive electrode of the HD pilot line as an example, the oven is 20m and the iron lithium coating speed is 5m / min, then the drying time is 4min. The actual hot air drying time needs to consider the coating film appearance, weight loss rate and other specifications. In some embodiments, the hot air drying degree is not sticky to the roller and does not crack. The weight loss rate of the pole piece after hot air drying is 1% to 1.5%, for example, 1%, 1.2% or 1.5%. After infrared drying, the weight loss rate of the pole piece is 0.7% to 1.2%, for example, 0.7%, 1.0% or 1.2%.

[0044] Since infrared heating is a non-contact heating process in which the internal energy of the radiation source is converted into radiation energy for heat transfer, the heat can penetrate into the heated object and no strong heat exchange will occur on the surface of the heated object. The present application performs infrared preheating before hot air drying, which can make the middle area of ​​the coating wet film both heated inside and outside, increase the uniformity of drying, and at the same time suppress the fluctuation of the temperature in the box caused by the entry of the low-temperature electrode coating during hot air drying, shorten the drying time; then use hot air drying to remove most of the solvent, and by controlling the hot air drying point, avoid the generation of electrode surface defects during the drying process; then use infrared heating to thoroughly dry the electrode, improve the overall drying efficiency, and save time and energy.

[0045] See also Figure 3 In some embodiments, the battery electrode is coated on both sides, that is, the first surface and the second surface of the current collector are coated with the slurry. In this case, after step S3, a second coating step S4 and a second drying step S5 are required.

[0046] The second coating step is to flip the single-sided electrode obtained after the first drying step and then repeat the first coating step to coat the slurry on the second surface of the current collector to form a second coating. After the coating is completed, the second drying step is performed to thoroughly dry the second coating. The second drying step is the same as the first drying step. The second layer is first preheated by infrared, and then most of the solvent is removed by hot air drying, and then the pole piece is thoroughly dried by infrared drying. It should be noted that the infrared preheating temperature in the second drying step is higher than the infrared preheating temperature in the first drying step, and the hot air drying temperature in the second drying step is higher than the hot air drying temperature in the first step. This is because the pole piece adopts a return coating method when double-sided coating is applied. After the first coating on the first surface of the current collector is applied, it needs to go through two drying processes, which is more prone to cracking. Therefore, the temperature of the first coating will be lower when it is dried, and the corresponding weight loss rate will be higher.

[0047] In some embodiments, the infrared preheating in the second drying step heats the temperature of the second coating to a temperature of 60 to 80°C, such as 60°C, 70°C or 80°C, etc.; the hot air drying temperature in the second drying step is 85 to 120°C, and further, 90 to 110°C, such as 90°C, 100°C or 110°C, etc. The weight loss rate of the electrode sheet after hot air drying is 0.8 to 1.2%, such as 0.8%, 1.0% or 1.2%, etc., and the weight loss rate of the electrode sheet after infrared drying in the second drying step is 0.1 to 0.4%, such as 0.1%, 0.2% or 0.4%, etc.

[0048] After the second drying step, a double-sided electrode can be obtained. The present invention preheats the coating with infrared before hot air drying, so that the temperature inside and outside the middle area of ​​the coating wet film is raised simultaneously, increasing the drying uniformity, and suppressing the fluctuation of the low-temperature electrode due to the low temperature when entering the hot air drying box, thereby shortening the drying time; hot air drying is used to remove most of the solvent in the coating, and the generation of surface defects of the electrode during the drying process is avoided by controlling the hot air drying point; infrared heating is used after hot air drying to thoroughly dry the electrode, thereby improving the overall drying efficiency and saving time and energy.

[0049] See also Figure 4 The present invention also provides a coating and drying device 100 for implementing the coating and drying method of the present invention, the device includes a conveying mechanism 110, a coating mechanism 120, an infrared preheating device 130, a hot air drying device 140 and an infrared drying device 150.

[0050] See also Figure 4 and Figure 5The conveying mechanism 110 is used to convey the electrode current collector 210. The conveying mechanism 110 includes a conveyor belt and a driving motor for driving the conveyor belt. The conveyor belt can transport the current collector to each station under the drive of the driving motor to complete the coating and drying process of the electrode. The coating mechanism 120 is arranged above the conveying mechanism 110 along the conveying direction of the conveyor belt to coat the current collector 210 on the conveying mechanism 110 with slurry. The specific structure of the coating mechanism 120 is not limited here, and the conventional structure in the field can be adopted. The hot air drying device 140 is arranged on one side of the coating mechanism 120. The hot air drying device 140 has a drying chamber. The conveyor belt of the conveying mechanism 110 runs through the drying chamber and extends from the entrance of the drying chamber to the outside of the outlet. The hot air drying device 140 is used to perform hot air drying on the current collector coated with slurry. The hot air drying device 140 can be, for example, a hot air drying tunnel box. The infrared preheating device 130 is arranged between the coating mechanism 110 and the hot air drying device 140, and is arranged horizontally above the conveyor belt. The infrared preheating device 130 can perform infrared preheating on the current collector coated with the slurry before it enters the hot air drying device 140, so as to preheat the coating temperature to the set temperature; the infrared preheating device 130 can be an infrared lamp, or it can be an infrared radiator or other device that can perform infrared heating. Because infrared heating is a non-contact heating process in which the internal energy of the radiation source is converted into radiation energy for heat transfer, the heat can penetrate into the heated object, and no strong heat exchange will occur on the surface of the heated object. Therefore, infrared preheating can heat the inside and outside of the coating at the same time, thereby increasing the uniformity of drying. Preferably, the infrared preheating device 130 also includes a light shielding baffle (not shown in the figure), which is slidably mounted on one side of the infrared light source. By sliding the light shielding baffle, part of the infrared light source can be shielded to achieve the effect of adjusting the heating area to meet the needs of different coating widths. The infrared drying device 150 is arranged on the side of the hot air drying device 140 away from the infrared preheating device, and can thoroughly dry the electrode after being dried by the hot air drying device 140. The infrared drying device 150, like the infrared preheating drying device 130, can also use infrared lamps, infrared radiators and other devices that can perform infrared heating.

[0051] It should be noted that the structures of the coating and drying device not described in detail above can be arranged according to the conventional arrangements in the art and will not be described in detail here.

[0052] The technical scheme of the present invention is described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0053] Example 1

[0054] See also Figure 5 , the positive electrode active material LiNi0.8 Co 0.1 Mn 0.1 O2, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black are mixed in a mass ratio of 98:1:1, and a solvent N-methylpyrrolidone (NMP) is added and stirred in a vacuum mixer until the system becomes uniform and transparent to obtain a positive electrode slurry;

[0055] The treated positive electrode current collector (aluminum foil with a thickness of 16 μm) is placed on a conveyor belt of a conveyor mechanism 110, and is transported to a coating mechanism 120 by the conveyor belt, and a positive electrode slurry is sprayed on a first surface of the positive electrode current collector by the coating mechanism 120 to form a first coating layer;

[0056] The current collector coated with the first coating is then sequentially conveyed by a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a single-sided electrode; wherein the infrared preheating device 130 preheats the first coating to 55° C., the hot air drying device 140 has a drying temperature of 80° C., the weight loss rate of the electrode sheet after hot air drying is 1%, and the weight loss rate of the electrode sheet after infrared drying is 0.7%;

[0057] The single-sided electrode is then turned over, and the positive electrode slurry is sprayed on the second surface of the positive electrode current collector by a coating mechanism 120 to form a second coating layer. The coated electrode is sequentially conveyed by a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a double-sided electrode; wherein, the infrared preheating device preheats the second coating layer to 60°C, and the drying temperature of the hot air drying device 140 is 85°C. The weight loss rate of the electrode after hot air drying is 0.8%, and the weight loss rate of the electrode after infrared drying is 0.1%.

[0058] The double-sided electrode film layer prepared in this embodiment has no defects such as cracking and floating of the adhesive on the surface, and the drying time is greatly shortened.

[0059] Example 2

[0060] See also Figure 5 , the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black are mixed in a mass ratio of 98:1:1, and a solvent N-methylpyrrolidone (NMP) is added and stirred in a vacuum mixer until the system becomes uniform and transparent to obtain a positive electrode slurry;

[0061] The treated positive electrode current collector (aluminum foil with a thickness of 16 μm) is placed on a conveyor belt of a conveying mechanism 110, and transported to a coating mechanism 120 by the conveyor belt, and a positive electrode slurry is sprayed on a first surface of the positive electrode current collector by the coating mechanism 120 to form a first coating layer;

[0062] The current collector coated with the first coating is then sequentially conveyed by a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a single-sided electrode; wherein the infrared preheating device preheats the first coating to 65° C., the drying temperature of the hot air drying device 140 is 95° C., the weight loss rate of the electrode sheet after hot air drying is 1.2%, and the weight loss rate of the electrode sheet after infrared drying is 1%;

[0063] The single-sided electrode is then turned over, and the positive electrode slurry is sprayed on the second surface of the positive electrode current collector by means of a coating mechanism 120 to form a second coating layer. The coated electrode is sequentially conveyed by means of a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a double-sided electrode. The infrared preheating device preheats the second coating layer to 70°C, and the drying temperature of the hot air drying device 140 is 110°C. The weight loss rate of the electrode after hot air drying is 1.0%, and the weight loss rate of the electrode after infrared drying is 0.3%.

[0064] The double-sided electrode film layer prepared in this embodiment has no defects such as cracking and floating of the adhesive on the surface, and the drying time is greatly shortened.

[0065] Example 3

[0066] See also Figure 5 , mixing the negative electrode active material artificial graphite, the conductive agent Ketjen black, the binder styrene-butadiene rubber, and the thickener sodium carbon methyl cellulose in a mass ratio of 87:9:2:1:1, adding deionized water, and fully stirring under the action of a vacuum mixer to obtain a negative electrode slurry;

[0067] The treated negative electrode current collector (copper foil with a thickness of 8 μm) is placed on a conveyor belt of a conveyor mechanism 110, and transported to a coating mechanism 120 by the conveyor belt. The coating mechanism 120 sprays a negative electrode slurry on a first surface of the negative electrode current collector to form a first coating layer.

[0068] The current collector coated with the first coating is then sequentially conveyed by a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a single-sided electrode; wherein the infrared preheating device preheats the first coating to 75° C., the drying temperature of the hot air drying device 140 is 115° C., the weight loss rate of the electrode sheet after hot air drying is 1.5%, and the weight loss rate of the electrode sheet after infrared drying is 1.2%;

[0069] The single-sided electrode is then turned over, and the negative electrode slurry is sprayed on the second surface of the negative electrode current collector by a coating mechanism 120 to form a second coating layer. The coated electrode is sequentially conveyed by a conveyor belt to an infrared preheating device 130, a hot air drying transposition device 140 and an infrared device 150 for drying to obtain a double-sided electrode. The infrared preheating device preheats the second coating layer to 80°C, and the drying temperature of the hot air drying device 140 is 120°C. The weight loss rate of the electrode after hot air drying is 1.2%, and the weight loss rate of the electrode after infrared drying is 0.4%.

[0070] The double-sided electrode film layer prepared in this embodiment has no defects such as cracking and floating of the adhesive on the surface, and the drying time is greatly shortened.

[0071] The battery pole piece of the present invention adopts a drying mode of infrared preheating, hot air drying and infrared drying, which increases the controllability of the pole piece drying process; infrared preheating is used before hot air drying, so that the temperature inside and outside the middle area of ​​the pole piece coating is simultaneously increased, which increases the uniformity of drying, and at the same time suppresses the fluctuation caused by the low-temperature pole piece coating entering the hot air drying box during hot air drying, thereby shortening the drying time; by controlling the hot air drying point, the generation of pole piece surface defects during the drying process can be avoided; after hot air drying, infrared heating is used to thoroughly dry the pole piece coating, thereby improving the overall drying efficiency and saving time and energy. The present invention adopts a composite drying mode of infrared preheating, hot air drying and infrared drying, which can suppress the problems of surface defects caused by excessive convection drying, excessive drying or low production efficiency caused by excessive drying. Therefore, the present invention effectively overcomes some practical problems in the prior art and thus has high utilization value and use significance.

[0072] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A coating and drying method for a battery pole piece, characterized in that: include: a slurry preparation step, mixing and stirring the active material, the conductive agent and the binder to prepare a slurry; A first coating step of coating the slurry on a first surface of a current collector to form a first coating on the first surface; In the first drying step, the current collector coated with the first coating layer is subjected to infrared preheating, hot air drying and infrared drying in sequence to obtain a pole piece.

2. The coating and drying method according to claim 1, characterized in that: The first coating layer is preheated by the infrared to a temperature of 55° C. to 75° C., and then hot air drying is performed.

3. The coating and drying method according to claim 1, characterized in that: The hot air drying temperature in the first drying step is 80-115° C., and the weight loss rate of the electrode sheet after the hot air drying is 1-1.5%.

4. The coating and drying method according to claim 1, characterized in that: In the first drying step, the weight loss rate of the electrode sheet after infrared drying is 0.7-1.2%.

5. The coating and drying method according to claim 1, characterized in that: The first drying step further includes a second coating step, which includes: coating the slurry on the second surface of the current collector to form a second coating on the second surface, wherein the first surface and the second surface are two surfaces of the current collector arranged opposite to each other along the thickness direction.

6. The coating and drying method according to claim 5, characterized in that: The second coating step also includes a second drying step. In the second drying step, the current collector coated with the second coating layer is subjected to infrared preheating, hot air drying and infrared drying in sequence to obtain a pole piece.

7. The coating and drying method according to claim 6, characterized in that: In the second drying step, the second coating is preheated to a temperature of 60-80° C. by infrared, and then dried by hot air.

8. The coating and drying method according to claim 6, characterized in that: The hot air drying temperature in the second drying step is 85-120° C., the weight loss rate of the electrode sheet after hot air drying is 0.8-1.2%, and the weight loss rate of the electrode sheet after infrared drying is 0.1-0.4%.

9. The coating and drying method according to claim 6, characterized in that: The infrared preheating temperature in the second drying step is greater than the infrared preheating temperature in the first drying step; the hot air drying temperature in the second drying step is greater than the hot air drying temperature in the first drying step.

10. A coating and drying device for battery pole pieces, characterized in that: include: Transmission mechanism; A coating mechanism, disposed on or beside the conveying mechanism, to coat the current collector on the conveying mechanism with slurry; A hot air drying device is arranged on one side of the coating mechanism and has a drying chamber for the conveying mechanism to enter; an infrared preheating device, disposed between the coating mechanism and the hot air drying device, to preheat the current collector coated with the slurry before entering the drying chamber; and The infrared drying device is arranged on a side of the hot air drying device away from the infrared preheating device to heat and dry the current collector after drying in the drying chamber.

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