Method and system for measuring areal density

Abstract

The application relates to a surface density measurement method and system, a first mass flow and a first solid content of a first slurry before entering a first die are obtained, the first slurry is coated on one side surface of a base through the first die to form a first wet coating layer; a first coating speed and a first coating width of the first slurry coated on the base through the first die are obtained; a first average wet film surface density is calculated according to the first coating speed, the first coating width and the first mass flow; a first average dry film surface density is calculated according to the first solid content and the first average wet film surface density; a first wet film surface density of the first wet coating layer is measured; and the first wet film surface density is corrected according to the first average dry film surface density to output a first dry film surface density for representing a surface density of a first dry coating layer. The method avoids the interference of a solvent on the surface density and achieves the purpose of accurately measuring the actual surface density of the first dry coating layer.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to a method and system for measuring areal density. Background Technology

[0002] In the manufacturing process of lithium-ion batteries, the coating process requires monitoring the areal density of the coating to ensure that the battery performance meets requirements. The wet coating applied to the substrate is usually dried using a drying device to form a dry coating. Drying cracking of the negative electrode coating in lithium-ion batteries is a common problem in the lithium battery manufacturing industry. Drying cracking refers to the presence of cracks in the direction of coating movement after the wet coating has been dried to form a dry coating; these cracks may run through the entire coating or appear intermittently. During the charging and discharging process, these cracks increase the lithium-ion movement path, leading to lithium plating and ultimately short-circuit failure. This type of defect is absolutely prohibited in the lithium battery manufacturing industry.

[0003] It has been verified that if a portion of the solvent remains in the dry coating after the wet coating is dried by the drying device, the problem of coating drying cracking can be solved. In other words, the coating is in a wet film state when it is dried and output by the drying device. This process is called "wet film shipment".

[0004] In traditional technology, the areal density measuring device for monitoring the coating's areal density is located downstream of the drying unit. When using the aforementioned "wet film shipment" process, the areal density measuring device may misinterpret the unevaporated solvent as the coating's areal density, ultimately leading to a higher measured value than the actual value. Furthermore, because it is impossible to accurately determine how much solvent remains unevaporated in the coating, the areal density measuring device cannot accurately measure the coating's actual areal density. Summary of the Invention

[0005] Therefore, it is necessary to provide a method and system for measuring the areal density of a coating that can accurately measure the actual areal density of the coating, in order to address the problem of the inability to accurately measure the actual areal density of the coating.

[0006] A method for measuring areal density, comprising the following steps:

[0007] The first mass flow rate and first solid content of the first slurry before entering the first die head are obtained. The first slurry is coated on one side surface of the substrate through the first die head to form a first wet coating.

[0008] The first coating speed and the first coating width of the first slurry applied to the substrate by the first die head are obtained;

[0009] Calculate the first average wet film surface density based on the first coating speed, the first coating width, and the first mass flow rate;

[0010] Calculate the first average dry film surface density based on the first solid content and the first average wet film surface density;

[0011] Measure the surface density of the first wet film of the first wet coating;

[0012] Based on the first average dry film surface density, the first wet film surface density is corrected to output a first dry film surface density for characterizing the surface density of the first dry coating.

[0013] The first dry coating is formed by drying the first wet coating using a drying device.

[0014] In one embodiment, the first coating speed is defined as V1, the first coating width as L1, and the first mass flow rate as Q. 质量1 The first average wet film surface density is M1, the first average dry film surface density is m1, and the first solid content is α1.

[0015] The step of calculating the first average wet film surface density based on the first coating speed, the first coating width, and the first mass flow rate includes:

[0016]

[0017] The step of calculating the first average dry film surface density based on the first solid content and the first average wet film surface density includes:

[0018] In one embodiment, the surface density of the first wet film is defined as m2;

[0019] The step of measuring the first wet film surface density of the first wet coating includes:

[0020] The first wet coating was subjected to X-ray scanning using an areal density measuring device, and the areal density of the first wet film was obtained based on the degree of X-ray attenuation.

[0021] in, I 01 I1 is the intensity of the radiation before it passes through the first wet coating; λ1 is the intensity of the radiation after it passes through the first wet coating; and λ1 is the absorption coefficient of the first wet coating.

[0022] In one embodiment, the step further includes:

[0023] Obtain the total dry film surface density of the first dry coating and the second dry coating; wherein, the second dry coating is formed by drying the second wet coating through a drying device, and the second wet coating is formed by applying the second slurry to the other side surface of the substrate through a second die head;

[0024] The difference between the total dry film surface density and the first dry film surface density is calculated to obtain the second dry film surface density of the second dry coating.

[0025] In one embodiment, the step of obtaining the total dry film surface density of the first dry coating and the second dry coating includes:

[0026] Obtain the second mass flow rate and second solid content of the second slurry before it enters the second die head;

[0027] The second coating speed and the second coating width of the second slurry applied to the substrate through the second die head are obtained;

[0028] Calculate the second average wet film surface density based on the second coating speed, the second coating width, and the second mass flow rate;

[0029] Calculate the second average dry film surface density based on the second solid content and the second average wet film surface density;

[0030] Measure the total wet film surface density of the first wet coating and the second wet coating;

[0031] The total wet film surface density is corrected based on the sum of the first average dry film surface density and the second average dry film surface density to output the total dry film surface density used to characterize the total surface density of the first dry coating and the second dry coating.

[0032] In one embodiment, the second coating speed is defined as V2, the second coating width as L2, and the second mass flow rate as Q. 质量2 The second average wet film surface density is M2, the second average dry film surface density is m3, and the second solid content is α2.

[0033] The step of calculating the second average wet film surface density based on the second coating speed, the second coating width, and the second mass flow rate includes:

[0034]

[0035] The step of calculating the second average dry film surface density based on the second solid content and the second average wet film surface density includes:

[0036] In one embodiment, the total wet film surface density is defined as m4;

[0037] The step of measuring the total wet film areal density of the first wet coating and the second wet coating includes:

[0038] The first wet coating and the second wet coating were scanned by X-ray using a surface density measuring device, and the total wet film surface density was obtained according to the degree of X-ray attenuation.

[0039] in, I 02I2 is the intensity of the radiation before it passes through the first and second wet coatings; I2 is the intensity of the radiation after it passes through the first and second wet coatings; λ2 is the absorption coefficient of the first and second wet coatings.

[0040] A surface density measurement system, comprising:

[0041] The first die head is used to apply the first slurry to one side surface of the substrate;

[0042] A drying device, located downstream of the first die head, is used to dry the first wet coating formed by the first slurry coating to obtain a first dry coating.

[0043] A first areal density measuring device is disposed between the first die head and the drying device, for obtaining the first wet film areal density of the first wet coating and outputting the first dry film areal density for characterizing the areal density of the first dry coating.

[0044] Wherein, the first dry film surface density is the surface density after correcting the first wet film surface density based on the first average dry film surface density. The first average dry film surface density is obtained by the first mass flow rate and first solid content of the first slurry before entering the first die head, as well as the first coating speed and first coating width of the first slurry applied to the substrate by the first die head.

[0045] In one embodiment, it further includes:

[0046] The first solid content meter and the first mass flow rate measuring device are located upstream of the first mold head and are used to obtain the first solid content and the first mass flow rate, respectively.

[0047] A first speed measuring instrument and a first film width measuring instrument are disposed between the first die head and the drying device, and are used to obtain the first coating speed and the first coating width, respectively.

[0048] In one embodiment, it further includes:

[0049] The second die head, located between the first areal density measuring device and the drying device, is used to apply the second slurry to the other side surface of the substrate; the drying device is also used to dry the second wet coating formed by the second slurry to form a second dry coating.

[0050] The second surface density measuring device is located between the second die head and the drying device, and is used to obtain the total wet film surface density of the first wet coating and the second wet coating, and output the total dry film surface density to characterize the total surface density of the first dry coating and the second dry coating.

[0051] The total dry film surface density is the surface density after correcting the total wet film surface density based on the sum of the first average dry film surface density and the second average dry film surface density. The second average dry film surface density is obtained by the second mass flow rate and the second solid content of the second slurry before entering the second die head, as well as the second coating speed and the second coating width of the second slurry applied to the substrate by the second die head.

[0052] In one embodiment, it further includes:

[0053] The second solids content meter and the second mass flow rate measuring device are located upstream of the second mold head and are used to obtain the second solids content and the second mass flow rate.

[0054] The second speed measuring instrument and the second film width measuring instrument are located between the second die head and the drying device, and are used to obtain the second coating speed and the second coating width, respectively.

[0055] The above-mentioned areal density measurement method and system calculates the first dry film areal density of the first dry coating by measuring the first wet film areal density of the first wet coating. Compared with the prior art, which directly places the areal density measuring device downstream of the drying device to measure the areal density of the dry coating, this method avoids the interference of solvent on the areal density and achieves the purpose of accurately measuring the actual areal density of the first dry coating. Attached Figure Description

[0056] Figure 1 A flowchart of a surface density measurement method provided in an embodiment of this application;

[0057] Figure 2 A flowchart of a surface density measurement method provided in another embodiment of this application;

[0058] Figure 3 for Figure 2 A flowchart of one step in the areal density measurement method shown;

[0059] Figure 4 A schematic diagram of a surface density measurement system provided in an embodiment of this application;

[0060] Figure 5 A schematic diagram of a surface density measurement system provided in another embodiment of this application;

[0061] Figure 6 A schematic diagram of a surface density measurement system provided in another embodiment of this application;

[0062] Figure 7 A schematic diagram of a surface density measurement system provided in another embodiment of this application.

[0063] Explanation of reference numerals in the attached figures:

[0064] 100. Areal density measuring system; 10. First die head; 20. Drying device; 30. First areal density measuring device; 40. First storage tank; 50. First feed pump; 60. First feed pipe; 70. First solid content meter; 80. First density meter; 90. First volumetric flow meter; 110. First mass flow meter; 120. First tachometer; 130. First film width measuring instrument; 140. Back roller; 150. Second die head; 160. Second areal density measuring device; 200. First wet coating; 300. First dry coating; 400. Second wet coating; 500. Second dry coating. Detailed Implementation

[0065] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0066] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0067] See Figure 1 One embodiment of this application provides a method for measuring areal density, including the following steps:

[0068] S110: Obtain the first slurry before it enters the first die head 10 (see...) Figure 4 The first mass flow rate and the first solid content are determined before the first slurry is applied to one side surface of the substrate through the first die head 10 to form a first wet coating 200.

[0069] Specifically, the substrate is a current collector. The substrate has a first surface and a second surface that are disposed opposite to each other, and the first slurry is applied to the first surface through the first die 10. The type of the first slurry is not limited.

[0070] Furthermore, the first slurry is stored in the first storage tank 40. When coating is required, the first feed pump 50 draws the first slurry from the first storage tank 40 and delivers it to the first die head 10 through the first feed pipe 60.

[0071] It should be noted that the first mass flow rate is the fluid mass of the first slurry passing through the effective cross-section of the first feed pipe 60 per unit time.

[0072] In one embodiment, the first mass flow rate can be obtained by acquiring the first density and first volumetric flow rate of the first slurry before it enters the first die head 10. The first mass flow rate is the product of the first density and the first volumetric flow rate. For example, the first mass flow rate testing device includes a first density meter 80 and a first volumetric flow meter 90. The first density is acquired through the first density meter 80, and the first volumetric flow rate is acquired through the first volumetric flow meter 90. In another embodiment, the first mass flow rate can also be obtained directly, such as by acquiring the first mass flow meter 110.

[0073] The first solids content is the percentage by mass of the remaining portion of the first slurry after drying under specified conditions. The first solids content is obtained using a first solids content meter.

[0074] S120: Obtain the first coating speed and the first coating width of the first slurry applied to the substrate by the first die head 10;

[0075] It should be noted that the first coating speed is the length coated per unit time, and the first coating width is the dimension coated in the direction perpendicular to the coating direction, which is related to the exit width of the first die 10. Specifically, the first coating speed is measured by the first speed measuring instrument 120, and the first coating width is measured by the first film width measuring instrument 130.

[0076] S130: Calculate the first average wet film surface density based on the first coating speed, the first coating width, and the first mass flow rate;

[0077] The first average wet film surface density is the average value of the wet film surface density in the width direction of the substrate (the width direction of the coating).

[0078] S140: Calculate the first average dry film surface density based on the first solid content and the first average wet film surface density;

[0079] The first average dry film surface density is the average value of the dry film surface density along the width direction of the substrate.

[0080] S150: Measure the surface density of the first wet film of the first wet coating 200;

[0081] The first wet coating 200 is a coating formed by applying the first slurry to the substrate and not drying it with the drying device 20, i.e., a coating in which the solvent has not yet evaporated. The first wet film surface density is measured by the first surface density measuring device 30 located between the first die head 10 and the drying device 20.

[0082] S160: Based on the first average dry film surface density, the first wet film surface density is corrected to output the first dry film surface density used to characterize the surface density of the first dry coating 300.

[0083] The first dry film surface density is the surface density formed after correcting the first wet film surface density based on the first average dry film surface density. It is used to characterize the surface density of the first dry coating 300, which is to characterize the surface density of the coating after the first wet coating 200 has been dried by the drying device 20.

[0084] The areal density measurement method provided in this application calculates the first dry film areal density of the first dry coating 300 by measuring the first wet film areal density of the first wet coating 200. Compared with the prior art method of directly placing the areal density measuring device downstream of the drying device 20 to measure the areal density of the dry coating, this method avoids the interference of solvent on the areal density and achieves the purpose of accurately measuring the actual areal density of the first dry coating 300.

[0085] In one embodiment, the first coating speed is defined as V1, the first coating width as L1, and the first mass flow rate as Q. 质量1 The first average wet film surface density is M1, the first average dry film surface density is m1; the first solid content is α1; Q 质量1 =ρ1.Q 体积1 ρ1 is the first density of the first slurry before it enters the first die head 10, Q 体积1 The first volumetric flow rate is the first slurry before it enters the first die head 10.

[0086] Step S130 includes:

[0087] According to the principle of conservation of volumetric flow rate at the inlet and outlet of the first mold head 10, M1, ρ1, Q 体积1 V1 and L1 satisfy:

[0088]

[0089] Step S140 includes:

[0090] Furthermore, step S150 includes:

[0091] The first wet coating 200 was scanned by X-ray using a surface density measuring device, and the surface density of the first wet film was obtained based on the degree of X-ray attenuation.

[0092] Specifically, the first wet film surface density of the first wet coating 200 before entering the drying device 20 is obtained by the first surface density measuring device 30. Generally, X-ray or β-ray surface density measuring devices are commonly used in the lithium battery industry. When X / β rays penetrate a material, they are reflected, scattered, and absorbed by the material, resulting in a certain attenuation of the intensity of the transmitted rays relative to the intensity of the incident rays. The attenuation ratio has a positive exponential relationship with the surface density of the penetrated material.

[0093] Define the surface density of the first wet film as m2. I 01I1 is the intensity of the radiation before it passes through the first wet coating 200; I1 is the intensity of the radiation after it passes through the first wet coating 200; λ1 is the absorption coefficient of the first wet coating 200, which is strongly correlated with the atomic number of the material in the first wet coating 200.

[0094] Step S160 includes:

[0095] m1 = k1·m2 + b1, then

[0096] The correction coefficients k1 and b1 are calculated according to the above formula, and the first dry film surface density is output based on m2 and the correction coefficients k1 and b1.

[0097] Since the first mass flow rate, first solid content, first coating speed, first coating width, and first wet film surface density fluctuate at different times, correction coefficients k1 and b1 are calculated by obtaining the first mass flow rate, first solid content, first coating speed, first coating width, and first wet film surface density at different times.

[0098] It should be noted that when the type of slurry remains unchanged, k1 is a fixed value. In this case, a value of k1 needs to be given, and the value of b1 can be calculated using the formula.

[0099] After obtaining the values ​​of k1 and b1, the obtained first wet film surface density is corrected using the obtained k1 and b1 values ​​to output the first dry film surface density.

[0100] In addition, due to the rising cost of raw materials and labor in the lithium battery manufacturing industry, the industry's manufacturing profits have decreased, making "cost reduction" a core demand for the industry.

[0101] In lithium battery manufacturing lines, coating is the most energy-intensive process, mainly due to the high power and low heat utilization of the drying device 20. Conventional coating line processes involve coating the first surface of the substrate with a first coating layer, drying it in the drying device 20, and then winding it up. The wound substrate is then coated with a second coating layer on the second surface and dried again in the drying device 20 before being wound up again, completing the coating process. This means the first coating layer passes through the drying device 20 twice, wasting manpower and resources, resulting in higher manufacturing costs.

[0102] To reduce manufacturing costs, double-sided coating is often used, with the first and second coatings entering the drying device 20 simultaneously for drying. In traditional technology, the areal density measuring device is located downstream of the drying device 20, which makes it impossible to distinguish the areal density of the first coating and thus cannot effectively monitor the coating quality.

[0103] In one embodiment, see Figure 2The areal density measurement method also includes the following steps:

[0104] S170: Obtain the total dry film surface density of the first dry coating 300 and the second dry coating 500;

[0105] Specifically, the second slurry is applied to the second surface of the substrate through the second die head 150. The type of the second slurry is not limited. The second slurry is stored in a second storage tank. When coating is required, a second feed pump draws the second slurry from the second storage tank and delivers it to the second die head 150 via a second feed pipe.

[0106] The second wet coating 400 is a coating formed by applying the second slurry onto the substrate and not drying it using the drying device 20. The second dry coating 500 is the coating formed by drying the second wet coating 400 using the drying device 20.

[0107] It should be noted that the total dry film surface density is measured by the second surface density measuring device 160. In one specific embodiment, the total dry film surface density is obtained by directly measuring the surface density of the first dry coating layer 300 and the second dry coating layer 500. In another specific embodiment, the total dry film surface density is obtained by detecting and correcting the surface density of the first wet coating layer 200 and the second wet coating layer 400.

[0108] S180: Calculate the difference between the total dry film surface density and the first dry film surface density to obtain the second dry film surface density of the second dry coating 500.

[0109] The areal density measurement method provided in this application can not only measure the areal density of the first dry coating 300, but also calculate the second dry film areal density of the second dry coating 500 by calculating the difference between the total dry film areal density and the first dry film areal density, thereby achieving the purpose of distinguishing the areal densities of the first dry coating 300 and the second dry coating 500, and effectively monitoring the coating quality.

[0110] In some embodiments, see Figure 3 Step S170 includes:

[0111] S171: Obtain the second mass flow rate and second solid content of the second slurry before it enters the second die head 150;

[0112] S172: Obtain the second coating speed and the second coating width of the second slurry applied to the substrate through the second die head 150;

[0113] S173: Calculate the second average wet film density of the second slurry coated on the substrate based on the second coating speed, the second coating width, and the second mass flow rate;

[0114] S174: Calculate the second average dry film surface density based on the second solid content and the second average wet film surface density;

[0115] S175: Measure the total wet film surface density of the first wet coating 200 and the second wet coating 400;

[0116] S176: Based on the sum of the first average dry film surface density and the second average dry film surface density, the total dry film surface density is corrected to output the total dry film surface density used to characterize the total surface density of the first dry film layer and the second dry coating layer 500.

[0117] The definitions of the second mass flow rate, second solid content, second coating speed, second coating width, second average wet film surface density, and second average dry film surface density can be referred to the definitions of the first mass flow rate, first solid content, first coating speed, first coating width, first average wet film surface density, and first average dry film surface density, and will not be elaborated here.

[0118] It should be noted that the total wet film surface density is the sum of the first wet film surface density and the second wet film surface density. The second wet film surface density is measured by the second surface density measuring device 160 located between the first density measuring device and the drying device 20.

[0119] The above setup calculates the total dry film density of the first dry coating 300 and the second dry coating 500 by measuring the total wet film density of the first wet coating 200 and the second wet coating 400. Compared with the method of measuring the total dry film density by placing the second surface density measuring device 160 downstream of the drying device 20, this avoids the interference of solvent on the total dry film density and achieves the purpose of accurately measuring the actual surface density of the dry film, that is, achieving the purpose of accurately measuring the actual surface density of the second dry coating 500.

[0120] Define the second coating speed as V2, the second coating width as L2, and the second mass flow rate as Q. 质量2 The second average wet film surface density is M2, the second average dry film surface density is m3; the second solid content is α2; Q 质量2 =ρ2.Q 体积2 ρ2 is the second density of the second slurry before it enters the second die head by 150°, and Q is the second density of the second slurry. 体积2 The second volumetric flow rate is the second slurry before it enters the second die head 150.

[0121] Step S173 includes:

[0122] According to the principle of conservation of volumetric flow rate at the inlet and outlet of the second mold head 150, M2, ρ2, Q 体积2 V2 and L2 satisfy:

[0123] Step S174 includes:

[0124] Furthermore, step S175 includes:

[0125] The first wet coating 200 and the second wet coating 400 were scanned by X-ray using a surface density measuring device, and the total wet film surface density was obtained according to the degree of X-ray attenuation.

[0126] Define the total wet film surface density as m4. I 02 I1 is the intensity of the radiation before it passes through the first wet coating 200 and the second wet coating 400; I2 is the intensity of the radiation after it passes through the first wet coating 200 and the second wet coating 400; λ2 is the absorption coefficient of the first wet coating 200 and the second wet coating 400, which is strongly correlated with the atomic number of the substances in the first wet coating 200 and the second wet coating 400.

[0127] Step S176 includes: m1 + m3 = k2·m4 + b2, then

[0128] The correction coefficients k2 and b2 are calculated based on the formula m1+m3=k2·m4+b2, and the total dry film surface density is output based on m4 and the correction coefficients k2 and b2.

[0129] Since the first mass flow rate, first solid content, first coating speed, first coating width, first wet film surface density, second mass flow rate, second solid content, second coating speed, second coating width, and second wet film surface density fluctuate at different times, correction coefficients k2 and b2 are calculated by obtaining the first mass flow rate, first solid content, first coating speed, first coating width, first wet film surface density, second mass flow rate, second solid content, second coating speed, second coating width, and second wet film surface density at different times.

[0130] It should be noted that when the type of slurry remains unchanged, k2 is a fixed value. In this case, the value of k2 needs to be given, and the value of b2 can be calculated by the formula.

[0131] After obtaining the values ​​of k2 and b2, the total wet film surface density is corrected using the obtained k2 and b2 values ​​to output the total dry film surface density.

[0132] See Figure 4Another embodiment of this application provides an areal density measurement system 100, including a first die head 10, a drying device 20, and a first areal density measuring device 30. The first areal density measuring device 30 is disposed between the first die head 10 and the drying device 20. The first die head 10 is used to coat a first slurry onto one side surface of a substrate. The drying device 20 is disposed downstream of the first die head 10 and is used to dry the first wet coating 200 formed by the coating of the first slurry into a first dry coating 300. The first areal density measuring device 30 is used to obtain the first wet film areal density of the first wet coating 200 and output a first dry film areal density characterizing the areal density of the first dry coating 300.

[0133] The first dry film surface density is the surface density after correcting the first wet film surface density based on the first average dry film surface density. The first average dry film surface density is obtained by the first mass flow rate and first solid content of the first slurry before entering the first die head 10, as well as the first coating speed and first coating width of the first slurry applied to the substrate by the first die head 10.

[0134] Specifically, the substrate has a first surface and a second surface that are disposed opposite to each other, and the first slurry is applied to the first surface through the first die 10.

[0135] During coating, the first die 10 extrudes the first slurry and applies it to the first surface of the substrate to form a first wet coating 200. The substrate, along with the first wet coating 200, enters the drying device 20 for drying. After drying in the drying device 20, the first wet coating 200 forms a first dry coating 300. It should be noted that the first dry coating 300 is not an absolutely dry coating; it contains a certain amount of solvent. The first areal density measuring device 30 can measure the first wet film areal density of the first wet coating 200 and correct the first wet film areal density based on the first average dry film areal density to output the first dry film areal density characterizing the first dry coating 300.

[0136] The areal density measurement system 100 provided in this application embodiment has a first areal density measuring device 30 located between the first die head 10 and the drying device 20. That is, in the coating direction, the first areal density measuring device 30 is located upstream of the drying device 20. It can calculate the first dry film areal density of the first dry coating 300 by measuring the first wet film areal density of the first wet coating 200. Compared with the prior art, which directly places the areal density measuring device downstream of the drying device 20 to measure the areal density of the dry coating, it avoids the interference of solvent on the areal density and achieves the purpose of accurately measuring the actual areal density of the first dry coating 300.

[0137] In one embodiment, the areal density measurement system 100 further includes a back roller 140, which supports the substrate so that the distance between the first die head 10 and the substrate is within a preset range, thereby ensuring the consistency of the coating areal density.

[0138] In one embodiment, the areal density measurement system 100 further includes a first storage tank 40, a first feed pump 50, and a first feed pipe 60. The two ends of the first feed pipe 60 are connected to the first storage tank 40 and the first die head 10, respectively. The first feed pump 50 is disposed on the first feed pipe 60. The first slurry is stored in the first storage tank 40. The first feed pump 50 can draw the first slurry from the first storage tank 40 and transport it to the first die head 10 for coating via the first feed pipe 60.

[0139] It should be noted that the first mass flow rate is the fluid mass of the first slurry passing through the effective cross-section of the first feed pipe 60 per unit time.

[0140] In one embodiment, the areal density measurement system 100 further includes a first solids content meter 70 and a first mass flow rate measuring device. The first solids content meter 70 is used to measure the first solids content of the first slurry, and the first mass flow rate measuring device is used to obtain the first mass flow rate of the first slurry. Specifically, the first mass flow rate measuring device includes a first densitometer 80 and a first volumetric flow rate meter 90. The first densitometer 80 is used to measure the first density of the first slurry, and the first volumetric flow rate meter 90 is used to measure the first volumetric flow rate of the first slurry. The first mass flow rate is obtained by multiplying the first density by the first volumetric flow rate.

[0141] In other embodiments, see Figure 5 The areal density measurement system 100 may omit the first density meter 80 and the first volumetric flow meter 90. The first mass flow measurement device includes a first mass flow meter 110, which directly measures the first mass flow of the first slurry.

[0142] In one embodiment, the areal density measurement system 100 further includes a first velocimeter 120 and a first film width measuring instrument 130, wherein the first velocimeter 120 is used to obtain a first coating speed and the first film width measuring instrument 130 is used to obtain a first coating width.

[0143] In some embodiments, see Figure 6 and Figure 7 The areal density measurement system 100 also includes a second die 150, which is disposed between the first areal density measurement device 30 and the drying device 20. The second die 150 is used to coat the slurry onto the second surface of the substrate. The drying device 20 is also used to dry the second wet coating 400 formed by the second slurry coating into a second dry coating 500. In this way, the areal density measurement system 100 can achieve simultaneous coating on both sides, improving the manufacturing efficiency of lithium batteries.

[0144] During coating, the second die 150 extrudes the second slurry and coats it onto the second surface of the substrate to form a second wet coating 400. The substrate, together with the first wet coating 200 and the second wet coating 400, enters the drying device 20 for drying. After the second wet coating 400 is dried by the drying device 20, it forms a second dry coating 500.

[0145] Furthermore, the areal density measurement system 100 also includes a second areal density measurement device 160 for obtaining the total dry film areal density of the first dry coating 300 and the second dry coating 500. Since the first areal density measurement device 30 can measure the first dry film areal density of the first dry coating 300, and the second areal density measurement device 160 can measure the total dry film areal density of the first dry coating 300 and the second dry coating 500, the second dry film areal density of the second dry film layer can be obtained by calculating the difference between the total dry film areal density and the first dry film areal density. Not only can the areal density of the first dry coating 300 be measured, but the second dry film areal density of the second dry coating 500 can also be obtained by calculating the difference between the total dry film areal density and the first dry film areal density, thus achieving the purpose of distinguishing the areal densities of the first dry coating 300 and the second dry coating 500, and effectively monitoring the coating quality.

[0146] In one implementation, see further... Figure 6 The second surface density measuring device 160 is located downstream of the drying device 20. It directly obtains the total dry film surface density by directly measuring the first dry coating 300 and the second dry coating 500.

[0147] In another implementation, see [link to relevant documentation]. Figure 7 A second areal density measuring device 160 is disposed between the second die head 150 and the drying device 20. The second areal density measuring device 160 is used to obtain the total wet film areal density of the first wet coating 200 and the second wet coating 400, and output the total dry film areal density. The total dry film areal density is the areal density after correcting the total wet film areal density based on the first average dry film areal density and the second average dry film areal density. The second average dry film areal density is obtained by the second mass flow rate and the second solid content of the second slurry before entering the second die head 150, and the second coating speed and the second coating width of the second slurry applied to the substrate by the second die head 150.

[0148] The above setup calculates the total dry film density of the first dry coating 300 and the second dry coating 500 by measuring the total wet film density of the first wet coating 200 and the second wet coating 400. Compared with the method of measuring the total dry film density by placing the second surface density measuring device 160 downstream of the drying device 20, this avoids the interference of solvent on the total dry film density and achieves the purpose of accurately measuring the actual surface density of the dry film, that is, achieving the purpose of accurately measuring the actual surface density of the second dry coating 500.

[0149] The areal density measurement system 100 also includes a second storage tank, a second feed pump, and a second feed pipe. The two ends of the second feed pipe are connected to the second storage tank and the second die head 150, respectively. The second feed pump is located on the second feed pipe. The second slurry is stored in the second storage tank. The second feed pump can draw the second slurry from the second storage tank and transport it to the second die head 150 for coating via the second feed pipe.

[0150] It should be noted that the second mass flow rate is the fluid mass of the second slurry passing through the effective cross-section of the second feed pipe per unit time.

[0151] Furthermore, the areal density measurement system 100 also includes a second solids content meter and a second mass flow rate testing device. The second solids content meter is used to measure the second solids content of the second slurry, and the second mass flow rate testing device is used to obtain the second mass flow rate of the second slurry. Specifically, the second mass flow rate testing device includes a second densitometer and a second volumetric flow rate meter. The second densitometer is used to measure the second density of the second slurry, and the second volumetric flow rate meter is used to measure the second volumetric flow rate of the second slurry. The second mass flow rate is obtained by multiplying the second density by the second volumetric flow rate.

[0152] In other embodiments, the areal density measurement system 100 may omit the second density meter and the second volumetric flow meter, and the second mass flow test device may include a second mass flow meter to directly measure the second mass flow rate of the second slurry.

[0153] The areal density measurement system 100 also includes a second velocimeter and a second film width measuring instrument. The second velocimeter is used to obtain a second coating speed, and the second film width measuring instrument is used to obtain a second coating width.

[0154] The areal density measurement method and system provided in this application have errors for the various measuring instruments used, as shown in Table 1. The slurry in Table 1 refers to either the first slurry or the second slurry.

[0155] Table 1

[0156]

[0157] Since the measurement error of each instrument is accumulated in the final measurement result, by analyzing the measurement error of each measuring instrument, the coating surface density measurement error is calculated to be ±0.15%, which is comparable to the measurement error of the coating surface density measured by offline measuring instruments (generally electronic scales) in the prior art. Therefore, the surface density measurement system 100 and method provided in this application are reliable.

[0158] For a graphite-based ink slurry with identical coating parameters, the areal density measurement method and system provided in this application were used to compare data with existing dry film measurement devices. Table 2 shows the coating-related parameters:

[0159] Table 2

[0160]

[0161] For the areal density measurement system 100 and method (wet film shipping process) provided in this application, after the coating process stabilizes, the slurry volumetric flow rate, density, solid content, coating speed, and coating width are collected and summarized in Table 3. According to the formula... The calculated value is m1 = 105.32 g / m 2 The areal density of the first dry coating 300 after drying was measured to be 105.44 g / m³ using an offline measuring instrument. 2 If so, the calculation error is less than 0.15%.

[0162] Table 3

[0163]

[0164] The areal density is scanned by the first areal density measuring device 30. The scan results of a single cycle are shown in Table 4. By calculation, the average value of the 13 scan results in a single scan cycle is m2 = 114.81 g / m2. According to the formula m1 = k1·m2 + b1, let k1 = 1, and calculate b1 = -9.49.

[0165] Table 4

[0166]

[0167]

[0168] After correction, coating began. The areal density measurement method and system of this application were used to collect the areal density data of the first dry film during the 2000-meter coating process. Simultaneously, the areal density data of the first dry coating layer 300 after exiting the drying device 20 was collected. Offline measuring instruments were used to collect the areal density data of the first dry coating layer 300, and the two sets of data were compared. The comparison results are shown in Table 5:

[0169] Table 5

[0170]

[0171] As can be seen from the data in Table 5, the mean, standard deviation, and quantiles of the areal density data collected by the areal density measurement method provided in this application are consistent with the results collected using offline measuring instruments.

[0172] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0173] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for measuring areal density, characterized in that, Including the following steps: The first mass flow rate and first solid content of the first slurry before entering the first die (10) are obtained. The first slurry is coated on one side surface of the substrate through the first die (10) to form a first wet coating (200). The first coating speed and the first coating width of the first slurry applied to the substrate by the first die (10) are obtained; Calculate the first average wet film surface density based on the first coating speed, the first coating width, and the first mass flow rate; Calculate the first average dry film surface density based on the first solid content and the first average wet film surface density; Measure the first wet film surface density of the first wet coating (200); Based on the first average dry film surface density, the first wet film surface density is corrected to output a first dry film surface density for characterizing the surface density of the first dry coating (300). The first dry coating (300) is formed by drying the first wet coating (200) using a drying device (20).

2. The areal density measurement method according to claim 1, characterized in that, Define the first coating speed as V1, the first coating width as L1, and the first mass flow rate as Q. 质量1 The first average wet film surface density is M1, the first average dry film surface density is m1, and the first solid content is α1. The step of calculating the first average wet film surface density based on the first coating speed, the first coating width, and the first mass flow rate includes: The step of calculating the first average dry film surface density based on the first solid content and the first average wet film surface density includes:

3. The areal density measurement method according to claim 2, characterized in that, Define the surface density of the first wet film as m2; The step of measuring the first wet film areal density of the first wet coating (200) includes: The first wet coating (200) was subjected to X-ray scanning using an areal density measuring device, and the areal density of the first wet film was obtained based on the degree of X-ray attenuation. in, I 01 I1 is the intensity of the radiation before it passes through the first wet coating (200); I1 is the intensity of the radiation after it passes through the first wet coating (200); λ1 is the absorption coefficient of the first wet coating (200).

4. The areal density measurement method according to any one of claims 1-3, characterized in that, It also includes the following steps: Obtain the total dry film surface density of the first dry coating (300) and the second dry coating (500); wherein, the second dry coating (500) is formed by drying the second wet coating (400) through a drying device (20), and the second wet coating (400) is formed by coating the second slurry onto the other side surface of the substrate through a second die (150); The difference between the total dry film surface density and the first dry film surface density is calculated to obtain the second dry film surface density of the second dry coating (500).

5. The areal density measurement method according to claim 4, characterized in that, The step of obtaining the total dry film areal density of the first dry coating (300) and the second dry coating (500) includes: Obtain the second mass flow rate and second solid content of the second slurry before it enters the second die head (150); The second coating speed and the second coating width of the second slurry applied to the substrate by the second die head (150) are obtained; Calculate the second average wet film surface density based on the second coating speed, the second coating width, and the second mass flow rate; Calculate the second average dry film surface density based on the second solid content and the second average wet film surface density; The total wet film surface density of the first wet coating (200) and the second wet coating (400) is measured; The total wet film surface density is corrected based on the sum of the first average dry film surface density and the second average dry film surface density to output the total dry film surface density used to characterize the total surface density of the first dry coating (300) and the second dry coating (500).

6. The areal density measurement method according to claim 5, characterized in that, Define the second coating speed as V2, the second coating width as L2, and the second mass flow rate as Q. 质量2 The second average wet film surface density is M2, the second average dry film surface density is m3, and the second solid content is α2. The step of calculating the second average wet film surface density based on the second coating speed, the second coating width, and the second mass flow rate includes: The step of calculating the second average dry film surface density based on the second solid content and the second average wet film surface density includes:

7. The areal density measurement method according to claim 6, characterized in that, Define the total wet film surface density as m4; The step of measuring the total wet film areal density of the first wet coating (200) and the second wet coating (400) includes: The first wet coating (200) and the second wet coating (400) were subjected to X-ray scanning using a surface density measuring device, and the total wet film surface density was obtained based on the degree of X-ray attenuation. in, I 02 I2 is the intensity of the radiation before it passes through the first wet coating (200) and the second wet coating (400); I2 is the intensity of the radiation after it passes through the first wet coating (200) and the second wet coating (400); λ2 is the absorption coefficient of the first wet coating (200) and the second wet coating (400).

8. A surface density measurement system (100), characterized in that, include: The first die head (10) is used to apply the first slurry to one side surface of the substrate; A drying device (20) is located downstream of the first die head (10) and is used to dry the first wet coating (200) formed by the first slurry coating to obtain the first dry coating (300). A first surface density measuring device (30) is disposed between the first mold head (10) and the drying device (20) for obtaining the first wet film surface density of the first wet coating (200) and outputting the first dry film surface density for characterizing the surface density of the first dry coating (300). Wherein, the first dry film surface density is the surface density after correcting the first wet film surface density based on the first average dry film surface density. The first average dry film surface density is obtained by the first mass flow rate and first solid content of the first slurry before entering the first die head (10), as well as the first coating speed and first coating width of the first slurry coated on the substrate by the first die head (10).

9. The areal density measurement system (100) according to claim 8, characterized in that, Also includes: The first solid content meter (70) and the first mass flow measurement device are located upstream of the first mold head (10) and are used to obtain the first solid content and the first mass flow, respectively. The first speed measuring instrument (120) and the first film width measuring instrument (130) are located between the first die head and the drying device (20), and are used to obtain the first coating speed and the first coating width, respectively.

10. The areal density measurement system (100) according to claim 8, characterized in that, Also includes: The second die head (150) is located between the first surface density measuring device (30) and the drying device (20) for applying the second slurry to the other side surface of the substrate; the drying device (20) is also used to dry the second wet coating (400) formed by the second slurry to form a second dry coating (500). The second surface density measuring device (160) is located between the second mold head (150) and the drying device (20) to obtain the total wet film surface density of the first wet coating (200) and the second wet coating (400), and output the total dry film surface density to characterize the total surface density of the first dry coating (300) and the second dry coating (500). The total dry film surface density is the surface density after correcting the total wet film surface density based on the sum of the first average dry film surface density and the second average dry film surface density. The second average dry film surface density is obtained by the second mass flow rate and the second solid content of the second slurry before entering the second die head (150), as well as the second coating speed and the second coating width of the second slurry coated on the substrate by the second die head (150).

11. The areal density measurement system (100) according to claim 10, characterized in that, Also includes: The second solid content meter and the second mass flow rate measuring device are located upstream of the second mold head (150) and are used to obtain the second solid content and the second mass flow rate. The second speed measuring instrument and the second film width measuring instrument are located between the second die head (150) and the drying device (20), and are used to obtain the second coating speed and the second coating width, respectively.

Images