A control method and system for improving coating thickness uniformity

Abstract

The present application relates to the field of slurry thickness automatic control, and discloses a coating thickness control method and system, comprising setting slurry dropping height H of coating slurry, coating speed U 入 , lip injection slurry volume V; obtaining static initial radius r e , surface tension gamma L, density rho, viscosity eta of coating slurry; calculating radius r(t) of droplet deposition on the substrate at different slurry dropping heights; judging whether r(t) increases with the increase of slurry dropping height H, if not, adjusting slurry dropping height H, coating speed U 入 , lip injection slurry volume V, so that r(t) increases with the increase of slurry dropping height H. The present application constructs the rheological curve of different positive and negative electrode slurry viscosities under different external factors by analyzing different positive and negative electrode slurry compositions and different temperatures, improves the coating uniformity, adapts to a wider slurry composition and proportion range, reduces the cost, and improves the product quality.

Description

Technical Field

[0001] This invention relates to the field of automatic control of slurry thickness, and in particular to a control method and system for improving the uniformity of coating thickness. Background Technology

[0002] The booming development of new energy vehicles has created a huge demand for power lithium batteries.

[0003] The uniformity of the thickness of the electrode sheets in a single battery cell seriously affects the safety performance of the power battery pack. As one of the key processes in the manufacturing of power lithium battery electrode sheets, ensuring the uniformity and stability of the coating is a prerequisite for improving battery performance.

[0004] Slit extrusion coating is more competitive in the field of power lithium battery coating due to its advantages such as fast coating speed, good coating uniformity, and wide coating window. However, the research on slit extrusion coating technology was initially focused on the traditional film and paper industries. Existing methods mainly consider optimizing the die head process and the film thickness feedback actuator to achieve a certain degree of film thickness uniformity in a closed loop. They rarely consider the changes in the internal slurry characteristics that lead to a decrease in coating uniformity. At the same time, with the increasing urgency of cost reduction, the cost reduction of positive and negative electrode slurries by many manufacturers, and the changes in the composition and proportion of positive and negative electrode slurries, have challenged the stability and uniformity of coating. Summary of the Invention

[0005] The main objective of this invention is to solve the technical problem of poor coating uniformity in the prior art. A coating thickness control method includes the following steps:

[0006] Set the slurry drop height H and the coating speed U. 入 1. The volume of slurry injected into the lip is V;

[0007] Obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η;

[0008] Calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights. The formula for calculating r(t) is as follows:

[0009]

[0010] Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H.

[0011] Determine whether r(t) increases with the increase of the slurry drop height H. If not, adjust the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the slurry drop height H.

[0012] A second aspect of the present invention provides a control system for improving coating thickness uniformity, comprising:

[0013] The coating apparatus includes a slurry drop height H and a coating speed U for coating slurry. 入 Module for injecting slurry volume V at the lip opening;

[0014] The parameter acquisition module is used to obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η;

[0015] The calculation module is used to calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights. The formula for calculating r(t) is as follows:

[0016]

[0017] Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入 t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H.

[0018] The judgment module determines whether r(t) increases with the increase of the slurry drop height H. If not, it adjusts the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the slurry drop height H.

[0019] A third aspect of the present invention provides an electronic device, comprising: a memory and at least one processor, wherein the memory stores instructions, and the memory and the at least one processor are interconnected via a circuit; the at least one processor invokes the instructions in the memory to cause the electronic device to perform the control method described above for improving coating thickness uniformity.

[0020] A fourth aspect of the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the control method described above for improving coating thickness uniformity.

[0021] The present invention has the following beneficial effects:

[0022] This invention analyzes the composition of different positive and negative electrode slurries and different temperatures to construct rheological curves of different positive and negative electrode slurry viscosities under different external factors. By calculating the radius r(t) of droplets deposited on the substrate at different slurry drop heights, it determines whether the coating is in a normal state. Furthermore, it uses the slurry drop height H and coating speed U... 入 Controlling the volume V of the slurry injected into the lip improves coating uniformity and adapts to a wider range of slurry compositions and proportions, reducing costs while improving product quality. Attached Figure Description

[0023] Figure 1 This is a flowchart of the thickness control method of the present invention;

[0024] Figure 2 The morphology of the upstream part of the coated bead under four critical conditions;

[0025] Figure 3 This is a schematic diagram showing the relationship between coating widening and coating gap. Detailed Implementation

[0026] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention 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 described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” or “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 and Figure 3 The first embodiment of a method for controlling coating thickness uniformity in this invention includes:

[0028] Set the slurry drop height H and the coating speed U. 入 1. The volume of slurry injected into the lip is V;

[0029] Obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η;

[0030] Calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights. The formula for calculating r(t) is as follows (the radius of the droplets deposited on the substrate changes with the height; the droplet radius of the slurry can be obtained from the Harth model based on the injection height):

[0031]

[0032] Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入 t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H.

[0033] There is a relationship between droplet spreading width and droplet height, which is usually described by the Weber number and Bond number. The Weber number (We) represents the ratio between inertial force and surface tension, i.e.

[0034]

[0035] Where ρ is the fluid density, v is the droplet velocity, d is the droplet diameter, and σ is the surface tension. A higher Weber number indicates a greater inertial force during droplet fall, making the droplet shape more easily changeable and increasing its spread width. The Bond number (Bo) represents the ratio between gravity and surface tension, i.e.:

[0036]

[0037] Where g is the acceleration due to gravity, d is the droplet diameter, and σ is the surface tension. The smaller the Bond number, the greater the influence of surface tension during droplet fall, making it easier for the droplet to maintain a spherical shape and reducing the spreading width. Therefore, when the Weber and Bond numbers are large, the droplet will exhibit a larger spreading width; when the Weber and Bond numbers are small, the droplet will exhibit a smaller spreading width. Besides the characteristics of the droplet itself and its velocity, the droplet height also affects the spreading width. Generally, the greater the droplet height, the larger the spreading width. Slit coating allows for flexible and convenient adjustment of the coating gap, effectively controlling the height of the slurry drop.

[0038] Determine whether r(t) increases with the increase of the slurry drop height H. If not, adjust the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the slurry drop height H.

[0039] Specifically:

[0040] Slurry drop height H: Affects the time it takes for the slurry to travel from the coating head to the substrate.

[0041] Coating speed U 入 The speed at which the slurry moves during the coating process may affect the spread of the droplets.

[0042] The volume of slurry injected into the lip and the drop height V: the amount of slurry injected each time, which affects the initial size and shape of the droplet.

[0043] Initial radius of rest, slurry drop height r e : The initial radius of the slurry in a static state.

[0044] Surface tension γ L Density ρ and viscosity η: Physical properties of the slurry that affect the spreading and shape of droplets.

[0045] Gravitational acceleration (G) at drop height g: a constant that affects the acceleration of the droplet during its descent.

[0046] Shape factor λ: The value ranges from 0.5 to 2 based on the slurry drop height, and is used to adjust the formula to better fit the experimental data.

[0047] Experimental delay time slurry drop height t0: The value range is slurry drop height 3-5, taking into account the experimental equipment response and measurement delay.

[0048] The formula for calculating the time interval t between the slurry's application from the coating head and its deposition on the substrate is:

[0049] .

[0050] The adjustment of the slurry drop height H and coating speed U... 入 The volume V of slurry injected through the lip causes r(t) to increase with the slurry drop height H, including:

[0051] like Figure 2 Observe the shape of the coating slurry, and adjust the slurry drop height H and coating speed U according to the shape of the coating slurry. 入 The method of injecting slurry volume V into the lip is as follows:

[0052] ① When the upstream area of ​​the coating bead is too large, slurry leakage occurs at the lip of the die head, resulting in coating accumulation and excessive coating thickness:

[0053] At this point, first adjust the coating speed U. 入 Then adjust the slurry drop height H, without adjusting the slurry volume V injected through the lip.

[0054] ② When the slurry is located at the bottom edge of the die lip, no slurry leakage occurs:

[0055] At this point, first adjust the coating speed U. 入 Then adjust the slurry drop height H. If it does not meet expectations, fine-tune the slurry volume V injected through the lip.

[0056] ③ When the slurry is located between the upper lip of the die and the slit channel:

[0057] At this point, the slurry drop height H and the coating speed U 入 The adjustment weights of the volume V of the slurry injected through the lip are equal, and the order can be adjusted simultaneously without regard to the sequence.

[0058] ④ When the slurry is located at the head edge of the lower die head lip:

[0059] At this point, prioritize adjusting the slurry injection volume V at the lip, then adjust the slurry drop height H and the coating speed U. 入 ;

[0060] ⑤ When the slurry causes air to be trapped at the head edge of the lower die head lip:

[0061] At this point, prioritize adjusting the volume V of the slurry injected through the lip, then adjust the slurry drop height H, and finally adjust the coating speed U. 入 .

[0062] Specifically:

[0063] ① The upstream area of ​​the coating bead is too large, and slurry leakage occurs at the lip of the die head, resulting in coating accumulation and excessive coating thickness;

[0064] Adjust strategy:

[0065] First, adjust the coating speed U. 入 Reducing the coating speed can reduce the accumulation of slurry on the die head, because a slower speed gives the slurry more time to spread and distribute evenly.

[0066] Next, adjust the slurry drop height H: If leakage still occurs after reducing the coating speed, try reducing the slurry drop height to reduce the kinetic energy of the slurry before it reaches the die head, thereby reducing the impact on the die head and leakage.

[0067] No adjustment of slurry volume V during lip injection: In this case, the main problem is not the initial amount of slurry, but its distribution and speed, so V is not directly adjusted.

[0068] ② The slurry is located at the bottom edge of the die lip, and there is no slurry leakage;

[0069] Adjust strategy:

[0070] First, adjust the coating speed U. 入 By fine-tuning the coating speed, the flow rate and spreading of the slurry on the die head can be controlled.

[0071] Next, adjust the slurry drop height H: If the slurry position is still not ideal after adjusting the coating speed, you can try adjusting the drop height to further control the slurry flow trajectory.

[0072] If the desired result is not achieved, fine-tune the volume of the slurry injected into the lip: If the slurry position still does not meet the requirements after the first two steps of adjustment, the volume of the slurry injected into the lip can be slightly adjusted, but this should be done with caution to avoid affecting other parameters.

[0073] ③ The slurry is located between the upper lip of the mold and the narrow slit channel;

[0074] Adjust strategy:

[0075] In this case, the adjustment weights of the three parameters are equal, so they can be adjusted simultaneously.

[0076] Simultaneously adjust the slurry drop height H and coating speed U. 入 The volume of slurry injected into the lip (V): These three parameters should be flexibly adjusted according to the specific location and shape of the slurry to achieve the best coating effect.

[0077] ④ The slurry is located at the head edge of the lower die head lip;

[0078] Adjust strategy:

[0079] Prioritize adjusting the slurry injection volume V at the lip: Increasing the slurry injection volume at the lip allows the slurry to fill the lip of the die head more fully, reducing blank areas at the edges.

[0080] Then adjust the slurry drop height H: If the slurry position is still not ideal after adjusting V, you can try adjusting the drop height to optimize the slurry flow trajectory.

[0081] Finally, adjust the coating speed U: After adjusting the first two parameters, fine-tune the coating speed to ensure uniform spreading of the slurry.

[0082] ⑤ The slurry causes air to be trapped at the head edge of the lower die head lip.

[0083] Adjust strategy:

[0084] Prioritize adjusting the volume of slurry injected into the lip: Increasing the slurry volume helps to expel and reduce air entrainment at the edges.

[0085] Secondly, adjust the slurry drop height H: Adjusting the drop height can change the speed and direction of the slurry when it reaches the die head, which helps to reduce air entrainment.

[0086] Finally, adjust the coating speed U. 入 After adjusting the first two parameters, fine-tune the coating speed to ensure stable flow and uniform spreading of the slurry, further reducing air entrainment.

[0087] The coating thickness control method further includes thickness h. 干 calculate:

[0088] The calculation formula is:

[0089]

[0090] G is the mass fraction of the coating slurry solution, K is the error coefficient, 0≤K≤1; T0 is the coating head temperature, T1 is the substrate temperature;

[0091] w is the slit width of the coating head, n is the number of coating strips, and U c E represents the coating speed, and E represents the width ratio.

[0092] The formula for calculating the width increase ratio E is:

[0093] .

[0094] The viscosity η is calculated as follows:

[0095]

[0096] Where k is the fluid consistency; γ is the shear rate; and ε is the non-Newtonian exponent.

[0097] The above describes a control method for improving coating thickness uniformity in embodiments of the present invention. The following describes a control device for improving coating thickness uniformity in embodiments of the present invention. A first embodiment of the control device for improving coating thickness uniformity in embodiments of the present invention includes:

[0098] The coating apparatus includes a slurry drop height H and a coating speed U for coating slurry. 入 Module for injecting slurry volume V at the lip opening;

[0099] The parameter acquisition module is used to obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η;

[0100] The calculation module is used to calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights. The formula for calculating r(t) is as follows:

[0101]

[0102] Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入 t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H.

[0103] The judgment module determines whether r(t) increases with the increase of the slurry drop height H. If not, it adjusts the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the slurry drop height H.

[0104] By analyzing the composition of different positive and negative electrode slurries and different temperatures, rheological curves of different positive and negative electrode slurry viscosities under different external factors were constructed. The radius r(t) of droplets deposited on the substrate at different slurry drop heights was calculated to determine whether the coating was in a normal state. Furthermore, the drop height H and coating speed U were used as parameters to determine the coating process. 入 Controlling the volume V of the slurry injected into the lip improves coating uniformity and adapts to a wider range of slurry compositions and proportions, reducing costs while improving product quality.

[0105] This invention provides an electronic device structure that can vary significantly depending on configuration or performance. It may include one or more central processing units (CPUs) (e.g., one or more processors) and memory, and one or more storage media (e.g., one or more mass storage devices) for storing applications or data. The memory and storage media can be temporary or persistent storage. The program stored in the storage media may include one or more modules (not shown in the figures), each module including a series of instruction operations on the electronic device. Furthermore, the processor may be configured to communicate with the storage media and execute the series of instruction operations stored in the storage media on the electronic device.

[0106] The electronic device may also include one or more power supplies, one or more wired or wireless network interfaces, one or more input / output interfaces, and / or one or more operating systems, such as Windows Server, Mac OS X, Unix, Linux, FreeBSD, etc. Those skilled in the art will understand that the structure of the electronic device does not constitute a limitation on the electronic device itself, and may include more or fewer components than described above, or combine certain components, or have different component arrangements.

[0107] The present invention also provides a computer-readable storage medium, which can be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when executed on a computer, cause the computer to perform the steps of a control method for improving coating thickness uniformity.

[0108] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system, device, or unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0109] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0110] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling coating thickness, characterized in that, Includes the following steps: Set the slurry drop height H and the coating speed U. 入 1. The volume of slurry injected into the lip is V; Obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η; Calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights; Determine whether r(t) increases with the increase of the slurry drop height H. If not, adjust the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the increase of the slurry drop height H; The formula for calculating r(t) is: Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入 t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H. The formula for calculating the time interval t between the slurry's application from the coating head and its deposition on the substrate is: 。 2. The coating thickness control method according to claim 1, characterized in that, The adjustment of the slurry drop height H and coating speed U... 入 The volume V of slurry injected through the lip causes r(t) to increase with the slurry drop height H, including: Observe the shape of the coating slurry, and adjust the slurry drop height H and coating speed U accordingly. 入 The method of injecting slurry volume V into the lip is as follows: ① When the upstream area of ​​the coating bead is too large, slurry leakage occurs at the lip of the die head, resulting in coating accumulation and excessive coating thickness: At this point, first adjust the coating speed U. 入 Then adjust the slurry drop height H, without adjusting the slurry volume V injected through the lip. ② When the slurry is located at the bottom edge of the die lip, no slurry leakage occurs: At this point, first adjust the coating speed U. 入 Then adjust the slurry drop height H. If it does not meet expectations, fine-tune the slurry volume V injected through the lip. ③ When the slurry is located between the upper lip of the die and the slit channel: At this point, the slurry drop height H and the coating speed U 入 The adjustment weights of the volume V of the slurry injected through the lip are equal, and the order can be adjusted simultaneously without regard to the sequence. ④ When the slurry is located at the head edge of the lower die head lip: At this point, prioritize adjusting the slurry injection volume V at the lip, then adjust the slurry drop height H and the coating speed U. 入 ; ⑤ When the slurry causes air to be trapped at the head edge of the lower die head lip: At this point, prioritize adjusting the volume V of the slurry injected through the lip, then adjust the slurry drop height H, and finally adjust the coating speed U. 入 .

3. A coating thickness control system, characterized in that, The system includes: The coating apparatus includes a slurry drop height H and a coating speed U for coating slurry. 入 Module for injecting slurry volume V at the lip opening; The parameter acquisition module is used to obtain the initial static radius r of the coating slurry. e Surface tension γ L Density ρ, viscosity η; The calculation module is used to calculate the radius r(t) of droplets deposited on the substrate at different slurry drop heights. The formula for calculating r(t) is as follows: Where, r e Let γ be the initial radius of the slurry at rest. L ρ is surface tension, ρ is density, g is gravitational acceleration, η is viscosity, λ is shape factor (value 0.5-2), V is the volume of slurry injected through the lip, and U... 入 t is the coating speed, t0 is the experimental delay time, which takes a value of 3-5, and t is the time interval between the slurry from the coating head to the deposition on the substrate. t is determined by the slurry drop height H. The formula for calculating the time interval t between the slurry's application from the coating head and its deposition on the substrate is: ； The judgment module determines whether r(t) increases with the increase of the slurry drop height H. If not, it adjusts the slurry drop height H and the coating speed U. 入 The volume V of slurry injected through the lip is such that r(t) increases with the slurry drop height H.

4. An electronic device comprising a memory and at least one processor, wherein the memory stores instructions; The at least one processor invokes the instructions in the memory to cause the electronic device to perform the steps of the coating thickness control method as described in claim 1 or 2.

5. A computer-readable storage medium storing instructions thereon, characterized in that, When the instructions are executed by the processor, they implement the various steps of the coating thickness control method as described in claim 1 or 2.

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