Screening method for battery cells meeting hot-pressing treatment conditions, hot-pressing treatment method for battery cells and preparation method

Abstract

The invention provides a screening method of battery cells meeting hot-pressing treatment conditions, a hot-pressing treatment method of the battery cells and a preparation method of the battery cells, and relates to the technical field of batteries. The screening method provided by the invention comprises the following steps: selecting uniformly distributed point positions on a to-be-hot-pressed surface of a battery cell, measuring the thickness xt of the battery cell at different point positions, and recording the maximum thickness as xmax, so that the thickness difference delta xt is equal to xmax-xt; covering a buffer material on the to-be-hot-pressed surface of the battery cell, then carrying out hot pressing treatment, measuring the thickness yt of the battery cell at different point positions after the hot pressing is finished, and determining that the hot pressing deformation quantity deltayt is equal to xt-yt; the delta yt and the delta xt are fitted, and a fitting curve of the delta yt and the delta xt is obtained; and calculating a thickness difference delta x corresponding to the standard deformation quantity delta y according to the fitting curve, so that the same type of battery cells with the surface thickness difference smaller than delta x meet the hot pressing treatment condition. The method can improve the hot pressing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for screening electric cells that meet hot pressing treatment conditions, a hot pressing treatment method for the electric cells and a preparation method thereof. Background Art

[0002] Hot pressing can improve and reduce the gap between the battery cell pole pieces, further improving the battery cell performance. However, during the battery manufacturing process, especially during the hot pressing stage, the unevenness between the battery cells or between the battery cells and the shell will lead to uneven pressure distribution, which may cause the internal microstructure of the battery cell to reduce the gap and become clogged due to uneven pressure distribution, further affecting the overall performance of the battery. By adding foam between the battery cells or between the battery cell and the hot pressing plate, its good compressibility and resilience can be used to fill the gap, thereby achieving the effect of evenly distributing pressure. However, this method is not applicable to some battery cells with poor surface flatness, so it is necessary to screen out suitable battery cells to improve the efficiency of hot pressing.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The first object of the present invention is to provide a method for screening battery cells that meet the conditions for hot pressing treatment, so as to solve the above technical problems.

[0005] A second object of the present invention is to provide a method for hot pressing a battery cell.

[0006] The third object of the present invention is to provide a method for preparing a battery cell.

[0007] In order to achieve the above objectives, the following technical solutions are adopted:

[0008] In a first aspect, the present invention provides a method for screening a battery cell that meets the conditions for hot pressing treatment, comprising the following steps:

[0009] a. Set the conditions for hot pressing treatment and the deformation amount Δy to meet the standard;

[0010] b. Select evenly distributed points on the hot pressing surface of the battery cell and measure the thickness x of the battery cell at different points t , let the maximum thickness be x max , then the thickness difference Δx t =x max -x t , where t is the point number;

[0011] c. Cover the surface of the battery cell to be hot-pressed with buffer material, and then perform hot-pressing. After the hot-pressing is completed, measure the thickness y of the battery cell at different points t , then the thermal deformation variable Δy t =xt -y t ;

[0012] d. Change Δy t and Δx t Perform fitting and obtain Δy t and Δx t The fitting curve of

[0013] e. Calculate the thickness difference Δx corresponding to the standard deformation amount Δy according to the fitting curve, and the same type of battery cells with a surface thickness difference less than Δx meet the hot pressing treatment conditions.

[0014] As a further technical solution, the Δy is less than Δx t =The thermal compression deformation at the point 0.

[0015] As a further technical solution, the number of the points is at least 5.

[0016] As a further technical solution, the cushioning material includes foam.

[0017] As a further technical solution, y=ax 2 +bx+c equation for Δy t and Δx t Perform fitting;

[0018] Among them, a, b and c are constants.

[0019] As a further technical solution, if the surface thickness difference of the same type of battery cells is greater than Δx, the battery cell does not meet the hot pressing treatment conditions.

[0020] As a further technical solution, the battery cell is a laminated battery cell.

[0021] As a further technical solution, the battery cell includes a sodium ion battery cell and a lithium ion battery cell.

[0022] In a second aspect, the present invention provides a method for hot pressing treatment of battery cells, wherein the battery cells are screened using the above screening method, and then the screened battery cells are hot pressed using set hot pressing treatment conditions.

[0023] In a third aspect, the present invention provides a method for preparing a battery cell, comprising treating the battery cell using the above-mentioned hot pressing method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention adopts for the first time a method of determining the heat pressing effect by heat pressure difference.

[0026] 2. The relationship between the cell thickness difference (thermal pressure deformation) and the thermal pressure difference is established for the first time. By using this relationship, the cell thickness can be directly used to screen out the cells that meet the thermal pressure conditions.

[0027] 3. This method can also be applied to hot pressing of multiple battery cells at the same time. It can directly select multiple battery cells with consistent thickness difference for hot pressing at the same time to improve the efficiency of hot pressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a schematic diagram of point selection in Example 1 of the present invention;

[0030] Figure 2 This is the relationship curve between the thermal compression deformation and the thickness difference. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but it will be appreciated by those skilled in the art that the following embodiments and examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified, proceed according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0032] In a first aspect, the present invention provides a method for screening a battery cell that meets the conditions for hot pressing treatment, comprising the following steps:

[0033] a. Set the conditions for hot pressing treatment and the deformation amount Δy to meet the standard;

[0034] b. Select evenly distributed points on the hot pressing surface of the battery cell and measure the thickness x of the battery cell at different points t , let the maximum thickness be x max , then the thickness difference Δx t =x max -x t , where t is the point number;

[0035] c. Cover the surface of the battery cell to be hot-pressed with buffer material, and then perform hot-pressing. After the hot-pressing is completed, measure the thickness y of the battery cell at different pointst , then the thermal deformation variable Δy t =x t -y t ;

[0036] d. Change Δy t and Δx t Perform fitting and obtain Δy t and Δx t The fitting curve of

[0037] e. Calculate the thickness difference Δx corresponding to the standard deformation amount Δy according to the fitting curve, and the same type of battery cells with a surface thickness difference less than Δx meet the hot pressing treatment conditions.

[0038] The screening method provided by the present invention quantifies the hot pressing effect by thickness, so as to improve the hot pressing effect and enhance the hot pressing efficiency by screening the battery cells before hot pressing.

[0039] In addition, according to the present invention, the relationship curve between the thermal pressure deformation and the difference in cell thickness is obtained. Through the changes in the cell deformation before and after, it can reflect the effect of adding foam and other buffer materials on improving the pressure uniformity of the cell. The pressure change is reflected by the cell deformation at different points of the cell, and the deformation is kept consistent as much as possible so that the cell is evenly compressed.

[0040] It should be noted that, in the present invention, the hot pressing treatment conditions and the target deformation amount Δy can be set as needed, and the two need to match to avoid the set deformation amount Δy being much higher than the hot pressing deformation amount that can be achieved under the hot pressing treatment conditions.

[0041] In some optional embodiments, the Δy is less than Δx t =The thermal compression deformation at the point 0.

[0042] In some optional embodiments, the number of the points is at least 5.

[0043] The more points you select, the more accurate the screening will be.

[0044] In some optional embodiments, the cushioning material includes but is not limited to foam, or other cushioning materials known to those skilled in the art.

[0045] The present invention does not impose any specific restrictions on the fitting equation. In some optional embodiments, y=ax 2 +bx+c equation for Δy t and Δx t Perform fitting;

[0046] Among them, a, b and c are constants and can be determined by fitting.

[0047] In some optional embodiments, the battery cell is a laminated battery cell.

[0048] The screening method of the present invention is applicable to a variety of battery cells. In some optional embodiments, the battery cells include sodium ion battery cells and lithium ion battery cells.

[0049] In a second aspect, the present invention provides a method for hot pressing a battery cell, comprising the following steps:

[0050] a. Set the conditions for hot pressing treatment and the deformation amount Δy to meet the standard;

[0051] b. Select evenly distributed points on the hot pressing surface of the battery cell and measure the thickness x of the battery cell at different points t , let the maximum thickness be x max , then the thickness difference Δx t =x max -x t , where t is the point number;

[0052] c. Cover the surface of the battery cell to be hot-pressed with buffer material, and then perform hot-pressing. After the hot-pressing is completed, measure the thickness y of the battery cell at different points t , then the thermal deformation variable Δy t =x t -y t ;

[0053] d. Change Δy t and Δx t Perform fitting and obtain Δy t and Δx t The fitting curve of

[0054] e. Calculate the thickness difference Δx corresponding to the standard deformation variable Δy according to the fitting curve, and select the same type of battery cells with a surface thickness difference less than Δx;

[0055] f. The screened cells are subjected to hot pressing treatment using set hot pressing conditions.

[0056] The battery cells treated by the heat pressing method can achieve the expected heat pressing effect.

[0057] In a third aspect, the present invention provides a method for preparing a battery cell, comprising treating the battery cell using the above-mentioned hot pressing method.

[0058] The present invention is further described below by means of specific examples. However, it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0059] Example 1

[0060] A method for screening battery cells that meet hot pressing treatment conditions comprises the following steps:

[0061] a. Set the hot pressing conditions as follows: pressure 0.6Mpa, hot pressing temperature 80°C, hot pressing time 60s;

[0062] The standard deformation Δy=0.075mm;

[0063] b. Figure 1 As shown, 9 evenly distributed points are selected on the hot pressing surface of the battery cell (the first battery cell in Table 1. It should be noted that the present invention is applicable to batteries of different sizes and specifications. The other two battery cells are also applicable to the method of the present invention after verification) and the thickness x of the battery cell at different points is measured. t , let the maximum thickness be x max , then the thickness difference Δx t =x max -x t , where t = 0, 1, 2, 3, ... 11;

[0064] Among them, the parameters of the battery cell are as follows:

[0065] Table 1

[0066] Serial number Cell Type Weight / g Thickness / mm Width / mm Length / mm Capacity / Ah 1 Laminated battery 539±10 8.8±0.3 141±2 240±2 30 2 Laminated battery 374±8 8.5±0.3 99±2 250±2 20 3 Laminated battery 1804±30 15.8±0.3 150.5 385 100

[0067] c. Cover the surface of the battery cell to be hot-pressed with 3mm foam, and then perform hot-pressing. After the hot-pressing is completed, measure the thickness y of the battery cell at different points t , then the thermal deformation variable Δy t =x t -y t ; The data are shown in Table 2:

[0068] Table 2

[0069] ΔXt ΔYt 0.01 0.0783 0.05 0.0783 0.07 0.0782 0.10 0.078 0.22 0.0764 0.24 0.076 0.24 0.0753 0.27 0.075 0.28 0.0727 0.36 0.0724 0.40 0.0713

[0070] d. Change Δy t and Δx t Perform fitting and obtain Δy t and Δx t The fitting curve is: Δy = -0.049Δx 2 +0.0021x+0.0783, e.g. Figure 2 As shown;

[0071] e. Calculate the thickness difference Δx corresponding to the standard deformation amount Δy according to the fitting curve, and the same type of battery cells with a surface thickness difference less than Δx meet the hot pressing treatment conditions.

[0072] Verification: According to the screening method provided in Example 1, 11 battery cells of the same type with a surface thickness difference less than Δx were screened, and then covered with 3mm foam for hot pressing treatment (pressure 0.6Mpa, hot pressing temperature 80°C, hot pressing time 60s). After the hot pressing, the hot pressing deformation amount of each point was detected respectively. The results showed that the hot pressing deformation amount of each point of the 11 batteries was above 0.075mm, as shown in Table 3.

[0073] Table 3

[0074]

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for screening cells that meet the conditions for hot pressing treatment, characterized in that: The following steps are involved: a. Set the conditions for hot pressing treatment and the deformation amount Δy to meet the standard; b. Select evenly distributed points on the surface of the battery cell to be hot pressed, and measure the thickness x of the battery cell at different points t , let the maximum thickness be x max , then the thickness difference Δx t =x max -x t , where t is the point number; c. Cover the surface of the battery cell to be hot-pressed with buffer material, and then perform hot-pressing. After the hot-pressing is completed, measure the thickness y of the battery cell at different points t , then the thermal deformation variable Δy t =x t -y t ; d. Change Δy t and Δx t Perform fitting and obtain Δy t and Δx t The fitting curve of e. Calculate the thickness difference Δx corresponding to the standard deformation amount Δy according to the fitting curve, and the same type of battery cells with a surface thickness difference less than Δx meet the hot pressing treatment conditions.

2. The screening method according to claim 1, characterized in that The Δy is smaller than Δx t =The thermal compression deformation at the point 0.

3. The screening method according to claim 1, characterized in that The number of the points is at least 5.

4. The screening method according to claim 1, characterized in that The cushioning material includes foam.

5. The screening method according to claim 1, characterized in that Using y=ax 2 +bx+c equation for Δy t and Δx t Perform fitting; Among them, a, b and c are constants.

6. The screening method according to claim 1, characterized in that If the surface thickness difference of the same type of battery cells is greater than Δx, the battery cell does not meet the heat pressing treatment conditions.

7. The screening method according to claim 1, characterized in that The battery core is a laminated battery core.

8. The screening method according to claim 1, characterized in that The battery cells include sodium ion battery cells and lithium ion battery cells.

9. A hot pressing method for a battery cell, characterized in that: The battery cells are screened by the screening method according to any one of claims 1 to 8, and then the screened battery cells are subjected to hot pressing treatment under set hot pressing treatment conditions.

10. A method for preparing a battery cell, characterized in that: The method comprises using the hot pressing method described in claim 9 to process the battery core.

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