Method for detecting coating area density of lithium battery electrode sheet, coating method and coating equipment

Abstract

The present application relates to a lithium battery pole piece coating area density detection method, a coating method and a coating device. A lithium battery pole piece coating area density detection method comprises: S1. When single-sided coating, an associated algorithm between the A-side dry film area density and the A-side wet film area density before drying is obtained; S2. When double-sided coating, the A-side wet film area density is detected, and the associated algorithm is substituted to obtain the A-side dry film area density; S3. The double-sided dry film area density of the AB side is detected, and the B-side dry film area density is calculated based on the A-side dry film area density obtained in S2. A lithium battery pole piece coating method is also provided based on the above area density detection method. A coating device is also provided. The present application effectively calculates and deduces the single-sided coating area density values of the corresponding A side and B side. The entire process method is very convenient to use, effectively improves the precision detection feasibility of the product, and improves the quality of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium battery processing, more particularly, to a lithium battery pole piece coating area density detection method, a coating method and a coating device. BACKGROUND

[0002] With the wide popularization of new energy vehicles, people's demand and process requirements for new energy vehicles are getting higher and higher, especially the battery endurance, the competition in the lithium battery industry is getting fiercer, and the requirements for energy density, safety and cost of lithium batteries are getting higher and higher, and then the requirements for coating precision, area density, surface quality and production cost of lithium battery pole pieces in the production link are also getting higher and higher.

[0003] The existing popular double-sided coating process method is mainly one-time single-sided coating online return type double-sided coating process, which has the characteristics that the pole piece substrate comes out from the unwinding device, the foil area density is detected, then the A side is high-precision coated and enters the oven with supporting rollers for drying, the A side dry film area density is detected and the A side CCD is detected after coming out of the oven, then it is reversely folded upward online, and then the B side is high-precision coated and enters the oven with supporting rollers for drying, the B side dry film area density is detected and the B side CCD is detected after coming out of the oven, and finally the pole piece is wound, the advantages of this process are that the A and B sides can be high-precision coated, the A and B sides can be respectively detected in area density and CCD, and the coating process of the A and B sides can be completed online, but its disadvantages are also obvious, such as low equipment utilization and production efficiency due to one-time coating of one side, high equipment investment cost due to two sets of ovens and other equipment, high factory investment cost due to large occupied area or space, high labor cost due to many operators, low coating quality due to abrasion of the A side dry coating layer caused by the back roller extrusion during B side coating, low coating quality due to the second drying problem of the A side dry coating layer during B side drying, high energy consumption, etc.

[0004] There is also a one-time double-sided coating process in the current technical means, which places the A and B side coating processes before the drying process, so that the substrate completes the AB double-sided coating process before entering the oven, and the AB double-sided dry film density is detected after drying; this method can solve the problems of low efficiency of two-time drying and two-time dry film detection, but it also has the problem of being unable to detect the coating area density of the A side and the B side respectively, that is, the total area density of the AB double-sided dry film can be obtained, but the actual dry film area density of the A side and the actual dry film area density of the B side cannot be known, if the total area density of the double-sided dry film is qualified, but the distribution on both sides is unqualified, the conductivity and quality of the product will also be affected to a certain extent. SUMMARY

[0005] The present application provides a lithium battery pole piece coating area density detection method, a coating method and a coating device.

[0006] To solve the above technical problems, the present application adopts the technical scheme of a lithium battery pole piece coating area density detection method, comprising the following steps:

[0007] S1. When single-sided coating, obtaining the correlation algorithm between the wet film area density after A-side coating and the dry film area density after A-side drying;

[0008] S2. When double-sided coating, detecting the wet film area density of A-side before B-side coating, substituting into the correlation algorithm, and calculating the dry film area density of A-side;

[0009] S3. After B-side coating and pole piece drying, detecting the double-sided dry film area density of AB, and calculating the actual dry film area density of B-side through the dry film area density of A-side obtained in S2.

[0010] Further, S1 specifically comprises the following steps:

[0011] S11. After coating, detecting the wet film area density to obtain the A-side wet film area density α;

[0012] S12. Drying A-side, and detecting the dry film area density of A-side of the dried pole piece to obtain the A-side dry film area density β;

[0013] S13. Screening group data to obtain the correlation algorithm of β and α, denoted as β=f(α).

[0014] Further, S2 further comprises the following step: detecting the light foil area density of the pole piece substrate before A-side coating, and marking as θ.

[0015] Further, S2 further calculates the actual dry film area density calculation formula of A-side as:

[0016] a=f(α)-θ

[0017] In the formula, a is the actual dry film area density of A-side.

[0018] Further, in S3, the actual dry film area density calculation formula of B-side is:

[0019] b=c-f(α)

[0020] In the formula, b is the actual dry film area density of the B surface, and c is the double-sided dry film area density.

[0021] Preferably, in the step S14, the screened multiple sets of data are multiple sets of data in the multiple detections and when the product is qualified, and the number of data is not less than 10 sets.

[0022] Also provided is a lithium battery pole piece coating method based on the above lithium battery pole piece coating area density detection method, comprising the following steps:

[0023] S101, unwinding the pole piece;

[0024] S102, detecting the light foil area density of the pole piece;

[0025] S103, coating the A surface of the pole piece;

[0026] S104, detecting the wet film area density of the A surface of the pole piece;

[0027] S105, coating the B surface of the pole piece;

[0028] S106, drying the pole piece after AB surface coating;

[0029] S107, detecting the double-sided dry film area density of the AB surface of the pole piece;

[0030] S108, winding the pole piece.

[0031] Preferably, the step S104 further comprises the following steps: calculating the actual dry film area density of the A surface, and adjusting the coating amount in the step S103 according to the calculation result;

[0032] The step S107 further comprises the following steps: calculating the actual dry film area density of the B surface, and adjusting the coating amount in the step S105 according to the calculation result.

[0033] Also provided is a coating device using the above lithium battery pole piece coating method, comprising an air float deflection roller for conveying the pole piece after AB surface coating and before drying.

[0034] Further, it further comprises an air float drying oven for floating drying the pole piece after AB surface coating.

[0035] Compared with the prior art, the beneficial effects are:

[0036] The application obtains the correlation algorithm between the dry film area density and the wet film area density of the A surface of the pole piece through limited experimental detection before mass production; then, in mass production, the wet film area density of the A surface is detected first, and then the dry film area density of the A and B surfaces is detected, and the actual dry film area density values of the A and B surfaces are effectively calculated and derived through the correlation algorithm; the original coating process is not changed or complicated processes are not added, the coating efficiency of the pole piece is not affected, the whole process method is very convenient to use, the precision detection feasibility of the product is effectively improved, and the quality of the product is improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram when the A surface and the B surface are uniformly distributed in Example 1.

[0038] Figure 2 is a schematic diagram when the A surface and the B surface are not uniformly distributed in the prior art.

[0039] Figure 3 is a schematic diagram of Example 4. DETAILED DESCRIPTION

[0040] The drawings are only used for illustrative description, and cannot be understood as a limitation on the patent; in order to better illustrate the embodiments, some components in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only used for illustrative description, and cannot be understood as a limitation on the patent. In addition, it should also be understood that the thickness, length and width of various components in the embodiments of the application shown in the drawings, and the overall thickness, length and width of the integrated device are only illustrative, and should not constitute any limitation on the application.

[0041] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used in the specification of the present application are only for the purpose of describing the specific embodiments of the present application, and are not intended to limit the present application; the terms in the specification and claims of the present application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0042] In addition, the terms "first", "second", "third", and the like are used only for descriptive purposes and do not denote or imply relative importance. "Vertical" is not strictly vertical, but within the range of error. "Parallel" is not strictly parallel, but within the range of error. In the description of the embodiments of the present application, the orientation or positional relationship indicated by the technical terms "thickness", "inner", "outer", and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0043] The pole piece mentioned in the embodiments of the present application is a component of a battery cell, as known to those skilled in the art, the battery cell mainly works by moving metal ions between the positive pole piece and the negative pole piece. The positive pole piece includes a positive current collector and a positive active material layer, the positive active material layer is coated on the surface of the positive current collector, the positive current collector without the positive active material layer protrudes from the positive current collector with the positive active material layer, and the positive current collector without the positive active material layer serves as a positive tab. Taking a lithium ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The negative pole piece includes a negative current collector and a negative active material layer, the negative active material layer is coated on the surface of the negative current collector, the negative current collector without the negative active material layer protrudes from the negative current collector with the negative active material layer, and the negative current collector without the negative active material layer serves as a negative tab. The material of the negative current collector can be copper, and the negative active material can be carbon or silicon, etc. In order to ensure that no fusing occurs when passing a large current, the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly can be a winding type structure or a stacking type structure, and the embodiments of the present application are not limited thereto.

[0044] The technical solutions of the present application will be further described in detail below through specific embodiments and in conjunction with the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0045] Embodiment 1

[0046] In the current technical means, reference Figure 1 and Figure 2If the AB double-sided dry film area density detection is performed after the double-sided coating of the pole piece, the total area density c of both sides is detected, but the actual dry film area density a of the single-sided coating and the actual dry film area density b increased by the coating on the other side cannot be known. However, for high-precision products, it is required that a and b are close to each other, that is, as shown in FIG. 2, the two sides are uniformly distributed, or a specific proportional relationship range; since the actual dry film area density a of the single-sided coating and the actual dry film area density b increased by the coating on the other side cannot be known, as shown in FIG. 3, the sum a+b of a and b is required, but a and b are not required respectively, the overall product is not required, but the current double-sided coating process cannot be detected. Figure 1 Figure 2

[0047] In view of the above technical problems, the inventors ingeniously design a lithium battery pole piece actual dry film area density detection method, which comprises the following steps:

[0048] S1. When single-sided coating, obtain the correlation algorithm between the wet film area density after A-side coating and the dry film area density after A-side drying;

[0049] S2. When double-sided coating, detect the wet film area density of A side before B-side coating, and substitute it into the correlation algorithm to calculate the dry film area density of A side;

[0050] S3. After B-side coating and pole piece drying, detect the double-sided dry film area density of AB side, and calculate the actual dry film area density of B side by using the dry film area density of A side obtained in S2.

[0051] That is, first, the relationship between the single-sided area density of one side (assumed to be A side in this embodiment) before and after coating is found out through experimental testing, which generally shows a linear proportional relationship, and an algorithm can be obtained through sufficient data; then, during mass production, A and B sides are both coated, but the wet film area density of A side is detected before B-side coating, and AB side is dried and measured after double-sided coating; the actual dry film area density value of A side can be obtained by using the wet film area density value of A side measured by using the algorithm relationship obtained in the foregoing, and the actual dry film area density value of B side can be calculated by using the corresponding algebraic relationship formula; through the above method, the actual dry film area density values of A side and B side can be ingeniously obtained, and the original coating process is not changed or increased, and the product precision detection efficiency and product qualification rate are effectively improved.

[0052] In this embodiment, S1 specifically comprises the following steps:

[0053] ​​S11. Only the A surface of the pole piece is coated, and the wet film surface density of the A surface is detected after coating, to obtain the A surface wet film surface density as α;

[0054] S12. The A surface is dried, and the dry film surface density of the A surface of the dried pole piece is detected, to obtain the A surface dry film surface density as β;

[0055] S13. Screening multiple sets of data to obtain the correlation algorithm of β and α, denoted as β = f(α).

[0056] That is, before mass production, only the A surface of the pole piece is coated and detected to obtain the corresponding correlation algorithm. Since the relationship is almost linear, when the data is sufficient, a sufficiently accurate correlation algorithm can be obtained. In the above step S2, the following step is further included: detecting the light foil of the pole piece substrate before coating the A surface, and calibrating it as θ;

[0057] In this way, during actual mass production, after coating the A surface, the wet film surface density of the A surface is detected to obtain the A surface wet film surface density as α, which can be inversely deduced to obtain the A surface dry film surface density as β, and then the actual dry film surface density of the A surface is calculated, as follows:

[0058] The actual dry film surface density calculation formula of the A surface in the AB double-sided dry film is as follows:

[0059] a = f(α) - θ

[0060] In the formula, a is the actual dry film surface density of the A surface.

[0061] And then the actual dry film surface density of the B surface is calculated, as follows: the actual dry film surface density calculation formula of the B surface in the AB double-sided dry film is as follows:

[0062] b = c - f(α)

[0063] In the formula, b is the actual dry film surface density of the B surface, and c is the double-sided dry film surface density.

[0064] In the step S14, the multiple sets of data screened are multiple sets of data when the product is qualified in multiple detections, and the number of data is not less than 10 sets. In a more preferred implementation, the total amount of qualified data is selected in the range of 30-60 sets according to the actual situation. If the final calculation value has deviation, the skilled person in the art can appropriately increase the screened qualified data.

[0065] Thus, before mass production, the present embodiment obtains the correlation algorithm between the A-side dry film area density and the wet film area density through limited experimental detection, and then in mass production, the wet film area density of the A-side is detected first, and then the dry film area density of the A-side and the B-side is detected, and the corresponding actual dry film area density values of the A-side and the B-side are calculated and derived through the correlation algorithm. The original coating process is not changed or the cumbersome process is not increased, the coating efficiency of the pole piece is not affected, the whole process method is very convenient to use, the precision detection feasibility of the product is effectively improved, and the quality of the product is improved.

[0066] Embodiment 2

[0067] The present embodiment provides a lithium battery pole piece coating method, which is processed by using the coating equipment as shown in Figure 3 and based on the above-mentioned lithium battery pole piece coating area density detection method, comprising the following steps:

[0068] S101, unwinding the pole piece;

[0069] S102, detecting the light foil area density of the pole piece;

[0070] S103, coating the A-side of the pole piece;

[0071] S104, detecting the wet film area density of the A-side of the pole piece;

[0072] S105, coating the B-side of the pole piece;

[0073] S106, drying the pole piece after AB-side coating;

[0074] S107, detecting the dry film area density of the AB-side of the pole piece;

[0075] S108, winding the pole piece.

[0076] In the present embodiment, the step S104 further comprises the following steps: calculating the actual dry film area density of the A-side, and adjusting the coating amount in the step S103 according to the calculation result; and the step S107 further comprises the following steps: calculating the actual dry film area density of the B-side, and adjusting the coating amount in the step S105 according to the calculation result.

[0077] Thus, when the actual detected and calculated A-side dry film area density and B-side actual dry film area density deviate from the required deviation range, the coating amount of the A-side or the B-side can be adjusted accordingly, so that the adjusted coating amount meets the requirements, and adaptive adjustment is made in time through detection data to ensure product quality.

[0078] Embodiment 3

[0079] The embodiment is similar to embodiment 2, and the difference is that a CCD detection process is added between step S107 and step S108 in the embodiment, and the product is detected by the CCD detection mechanism 108.

[0080] Embodiment 4

[0081] The embodiment is a coating device using the lithium battery pole piece coating method in embodiment 2, and reference is made to the coating device shown in Figure 3 .

[0082] In the embodiment, the coating device shown in Figure 3 is used to coat the pole piece of the lithium battery, and the process steps are as follows: the pole piece is unwound by the unwinding machine 101, the pole piece 100 is walked in a predetermined direction, the foil surface density is detected at the first surface density detector 102, the A surface is coated at the first coating mechanism 103, the A surface is detected on line at the second surface density detector 104, the B surface is coated at the second coating mechanism 105, after the A surface and the B surface are both coated, the pole piece is dried in the air float oven 106, after drying, the AB surface is detected by the third surface density detector 107, then the CCD detection is performed at the CCD detection mechanism 108, and finally the pole piece is wound by the winding mechanism 109.

[0083] The embodiment is also characterized in that an air float turning roller is arranged between the second coating mechanism 105 and the oven of the coating device, and the pole piece is suspended and dried in the air float oven 106. The pole piece after AB surface coating and before drying is transported; because the A surface and the B surface are both coated, it is necessary to ensure that both surfaces cannot have physical contact with the turning roller. The principle of the air float turning roller is that the substrate with AB double surfaces after coating is turned into the air float oven without any physical contact through a stable outer flow field, and it can also serve as the nearest fulcrum in front of the air float oven to provide tension to the substrate, thereby ensuring the coating and drying effects.

[0084] Obviously, the above embodiments of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the implementation modes. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for detecting the coating surface density of a lithium battery pole piece, characterized in that: The following steps are involved: S1. When coating on one side, obtain the correlation algorithm between the wet film surface density after coating on the electrode surface A and the dry film surface density after drying on the electrode surface A; S2. When double-sided coating is applied, after coating side A and before coating side B, the wet film density of side A is measured and substituted into the correlation algorithm to calculate the dry film density of side A. S3. After coating the B side and drying the electrode, the dry film density of both sides A and B is tested. The actual dry film density of the B side is calculated based on the dry film density of the A side obtained in S2. The step S2 further includes the following steps: calculating the actual dry film surface density of surface A, and adjusting the coating amount in step S1 according to the calculation result; The step S3 further includes the following steps: calculating the actual dry film surface density of the B side, and adjusting the coating amount in the step S2 according to the calculation result.

2. The method for detecting the coating surface density of a lithium battery pole piece according to claim 1, wherein: The S1 specifically includes the following steps: S11. After coating, the wet film surface density of surface A is measured, and the wet film surface density of surface A is α; S12. Drying the A surface, and testing the dry film surface density of the electrode after drying the A surface, and obtaining the dry film surface density of the A surface is β; S13. Filter multiple groups of data to obtain the association algorithm between β and α, denoted as β=f(α).

3. The method for detecting the coating surface density of a lithium battery pole piece according to claim 2, wherein: Said S2 further includes the following steps: before coating the A side, the light foil surface density of the electrode substrate is tested and calibrated as θ.

4. The method for detecting the coating surface density of a lithium battery pole piece according to claim 3, wherein: In step S2, the actual dry film surface density of surface A is also calculated using the formula: a=f(α)-θ Where a is the actual dry film surface density of surface A.

5. The method for detecting the coating surface density of a lithium battery pole piece according to claim 2, wherein: In S3, the actual dry film surface density of surface B is calculated as follows: b=cf(α) Where b is the actual dry film density of side B, and c is the double-sided dry film density.

6. The method for detecting the coating surface density of a lithium battery pole piece according to claim 2, wherein: In step S13, the multiple sets of data screened are multiple sets of data when the product is qualified during multiple tests, and the number of data is no less than 10 sets.

7. A lithium battery pole piece coating method, based on the lithium battery pole piece coating surface density detection method according to any one of claims 1 to 6, characterized in that: The following steps are involved: S101, electrode unwinding; S102, testing the surface density of the light foil of the electrode; S103, coating the A side of the electrode; S104, testing the wet film surface density of the A side of the electrode; S105, coating the B side of the electrode; S106, drying the electrode after coating the AB surface; S107, perform double-sided dry film surface density test on the AB surface of the electrode; S108, winding the electrode.

8. The lithium battery pole piece coating method according to claim 7, characterized in that: The step S104 further includes the following steps: calculating the actual dry film surface density of surface A, and adjusting the coating amount in step S103 according to the calculation result; The step S107 further includes the following steps: calculating the actual dry film surface density of the B side, and adjusting the coating amount in step S105 according to the calculation result.

9. A coating device using the lithium battery pole piece coating method according to any one of claims 7 to 8, characterized in that: It includes air-floating turning rollers, which are used to transport the electrodes after AB surface coating and before drying.

10. The coating device according to claim 9, characterized in that It also includes an air flotation oven for suspending and drying the electrodes after coating on the AB surfaces.

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