Method for calculating thinning value of R-angle area of winding battery cell, thinning method and battery cell

Abstract

The invention belongs to the technical field of winding battery cells, and particularly relates to a winding battery cell R angle area thinning value calculation method, a thinning method and a battery cell. The method for calculating the structure thinning value of the R-angle region of the winding battery cell comprises the following steps: firstly, determining geometric position relations of a positive pole piece and a negative pole piece in the R-angle region of the winding battery cell, and establishing a corresponding positive curve equation and a corresponding negative curve equation based on the relations; thirdly, integrating the positive curve equation to obtain the arc length (recorded as Lpositive m) of the positive pole piece on the outer side of the mth circle, and similarly, integrating the negative curve equation to obtain the arc length (recorded as Lnegative m) of the negative pole piece on the inner side of the mth circle; and finally, calculating the thinning value of the mth circle in the R-angle area of the winding battery cell by using a predefined thinning value calculation formula according to the arc length information of the positive pole piece and the negative pole piece, furthermore, according to the calculated thinning value of the R-angle area structure of the winding battery cell, the design and manufacturing process of the battery cell is optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of wound battery cells, and in particular relates to a method for calculating the thinning value of an R-angle region of a wound battery cell, a thinning method, and a battery cell. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics, power batteries, energy storage and other fields due to their advantages such as high energy density and long cycle life. Among them, wound batteries are widely used due to their high volume utilization and mature technology. However, during the winding process, as the positive electrode, negative electrode and separator are continuously stacked, the positive and negative electrode sheets at the corners (R corners) of the battery cell often cannot achieve a good and tight fit or the phenomenon of "positive electrode overlying negative electrode" occurs, resulting in insufficient active area of ​​the negative electrode at that location, which is prone to negative electrode lithium plating problems during high-rate or low-temperature charging.

[0003] At present, the treatment method for the R corner area of ​​wound lithium-ion batteries mainly focuses on increasing the negative electrode coating thickness (positive and negative sides), that is, by increasing the additional coating amount on the outer ring negative electrode, the local negative electrode capacity of the R corner can be increased to avoid lithium precipitation. However, this method will increase the thickness of the battery cell and reduce the energy density, and when the overall thickness of the negative electrode is greatly increased, it may cause uneven winding of the pole piece, affecting mass production and consistency. Further. In the prior art, during the manufacturing process of the battery cell, the corner area is locally thickened or material compensation is performed to improve the N / P ratio. However, this type of process is highly complex and requires extremely high coating position accuracy, making it difficult to mass-produce in actual production. Moreover, if the compensation position is inaccurate, it will still cause uneven coating, affecting the final performance.

[0004] Based on this, it is urgent to improve the existing method for calculating the thinning value of the R corner area of ​​the wound battery cell, the thinning method and the battery cell structure to solve the defects of the above-mentioned technology. Summary of the Invention

[0005] One of the purposes of the present invention is to address the deficiencies of the prior art and provide a method for calculating the R-corner thinning value of a wound battery cell, which can improve the calculation accuracy of the R-corner thinning value of the wound battery cell.

[0006] In order to achieve the above-mentioned purpose of the invention, the applicant has implemented the following technical solutions:

[0007] A method for calculating the thinning value of the R corner area of ​​a wound battery cell comprises the following steps:

[0008] S101, constructing a positive electrode curve equation based on the geometric position relationship of the positive electrode sheet in the R corner area of ​​the wound battery cell; constructing a negative electrode curve equation based on the geometric position relationship of the negative electrode sheet in the R corner area of ​​the wound battery cell;

[0009] S201, perform positive arc integration on the positive electrode curve equation to obtain L 正m, the negative electrode curve equation is integrated into the negative electrode arc to obtain L 负m ;L 正m Indicates the arc length of the positive electrode outside the mth circle, L 负m Table 1 shows the arc length of the inner circle of the mth circle;

[0010] S301 , constructing a thinning value calculation formula according to the relationship between the length of the positive electrode sheet and the length of the negative electrode sheet in the R-angle region of the wound battery cell, and calculating the thinning value of m turns in the R-angle region of the wound battery cell using the thinning value calculation formula.

[0011] The above technical solution produces the following technical effects:

[0012] This application provides a method for calculating the thinning value of the R-corner area structure of a wound battery cell. Through geometric modeling and circle arc length integration, the actual arc length difference between the positive and negative electrodes at the R corner of each circle is more accurately obtained, and the thinning value is calculated based on this. Based on this, while ensuring the safety lower limit of the N / P ratio (or CB value), the application effectively controls the risk of local lithium plating at the negative electrode. Compared with traditional methods, it has the advantages of high calculation accuracy, low loss, and mass production, overcoming the defects of inaccurate calculations, unreasonable thinning ranges, and difficult implementation of actual processes in existing technical solutions.

[0013] As a further improvement to the method for calculating the thinning value of the R-corner region structure of a wound battery cell of the present application, the positive electrode curve equation in step S101 is:

[0014] y 正 =b m -d m x 2

[0015] The negative electrode curve equation is:

[0016] y 负 =c m -a m x 2

[0017] Among them, a m Indicates the opening degree of the negative electrode curve equation of the negative electrode sheet in the mth circle; b m Indicates the arc curvature radius of the positive electrode piece at the top of the R angle area; c m Indicates the arc curvature radius of the negative electrode at the top of the R angle area; d m Indicates the degree of opening of the equation of the negative electrode curve of the positive electrode sheet in the mth circle.

[0018] As a further improvement of the method for calculating the thinning value of the R corner area structure of a wound battery cell in the present application, the arc curvature radius c of the negative electrode sheet at the top of the R corner area is m The thickness of the positive electrode h正 , the thickness of the negative electrode h 负 and the thickness of the diaphragm h 隔膜 satisfy:

[0019] c m+1 =c m +h 正 +h 负 +2h 隔膜

[0020] Where m>0.

[0021] As a further improvement of the calculation method of the thinning value of the R corner area structure of a wound battery cell in the present application, when m=0, the arc curvature radius c of the negative electrode sheet at the top of the R corner area is m Satisfy the formula: c1=h 正 / 2+h 负 / 2+n*h 隔膜 , wherein n represents the number of innermost winding separator layers in the wound battery cell.

[0022] As a further improvement of the method for calculating the thinning value of the R corner area structure of a wound battery cell in the present application, the arc curvature radius d of the positive electrode sheet at the top of the R corner area is m The arc curvature radius c of the negative electrode at the top of the R angle area m and the thickness of the diaphragm h 隔膜 satisfy:

[0023] b m -c m =h 隔膜

[0024] Where m>0.

[0025] As a further improvement to the method for calculating the thinning value of the R-corner region structure of a wound battery cell of the present application, the expression for the positive electrode arc integral in step S201 is:

[0026]

[0027] The expression of the negative arc integral is:

[0028]

[0029] As a further improvement to the method for calculating the thinning value of the R-corner region structure of a wound battery cell in the present application, the thinning value calculation formula is:

[0030] λ m =△L m / L 正m

[0031] Among them, △L m△L is the portion where the length of the positive electrode sheet exceeds the length of the negative electrode sheet in the R corner area of ​​the wound battery cell. m The solution satisfies: △L m =L 正m -L 负m .

[0032] The second object of the present invention is to address the deficiencies of the prior art and provide a method for thinning a wound battery cell based on a thinning value of an R corner area of ​​the wound battery cell with high calculation accuracy.

[0033] In order to achieve the above-mentioned invention objectives, this application implements the following technical solutions:

[0034] A method for thinning the corner region structure of a wound cell, wherein the thinning value λm and the N / P ratio α of the straight region of the wound cell are calculated according to any of the above-mentioned methods for calculating the thinning value of the R corner region structure of the wound cell; wherein α is the ratio of the reversible surface capacity of the negative electrode sheet to the reversible surface capacity of the positive electrode sheet; when α-λm≥CB min When α-λm <CB min , then the positive electrode sheet is thinned; CB min The minimum thinning value required for the set wound battery cell.

[0035] The above technical solution produces the following technical effects:

[0036] This method can achieve precise thinning of the R corner area of ​​the wound battery cell, effectively controlling the risk of local lithium deposition in the negative electrode while ensuring the energy density and consistency of the battery cell. min The safety lower limit is set to ensure that the thinned battery cell still meets the performance requirements. In addition, the method can be calculated based on the actual structural parameters of the battery cell, which is highly flexible and applicable and can be widely applied to the manufacturing of different types of wound battery cells.

[0037] As a further improvement of the method for thinning the corner region structure of a wound battery core in the present application, the N / P ratio α of the straight region satisfies: 1<α<1.2.

[0038] A third object of the present invention is to address the deficiencies of the prior art and provide a battery cell that is thinned according to the thinning value of the R corner area of ​​the wound battery cell.

[0039] In order to achieve the above technical objectives, this application implements the following technical solutions:

[0040] A battery cell is prepared by any of the above methods for thinning the R corner area of ​​a wound battery cell.

[0041] The above technical solution produces the following technical effects:

[0042] Because the battery cell of this application has a more uniform fit between the positive and negative electrode sheets in the R corner area, it effectively avoids the problem of lithium plating at the negative electrode, improving the safety and cycle life of the battery cell. At the same time, the battery cell still maintains a high energy density and volume utilization rate, making it suitable for various electronic devices with high energy density requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0044] Figure 1 This is a schematic diagram of the structure of the R corner area of ​​the wound battery cell in the present invention;

[0045] Figure 2 This is a flow chart of the method for thinning the R corner area structure of the wound battery cell in the present invention;

[0046] Figure 3 Schematic diagram of the structure of the positive electrode sheet in the wound battery cell structure of the present invention;

[0047] Figure 4 Schematic diagram of the battery cell winding method in the present invention.

[0048] in:

[0049] 1- positive pole outer arc area;

[0050] 2-current collector;

[0051] 3- positive outer arc area;

[0052] 31-Thinning area. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0054] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0055] Although the present application is disclosed as above in terms of a preferred embodiment, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

[0056] The present invention will be described in further detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0057] It is known that for wound lithium-ion batteries, the negative electrode's R-corner region is prone to lithium deposition. Compared to the straight region, the R-corner region has poorer contact with the positive electrode, and the convex surface has a lower N / P ratio (the ratio of the negative electrode's reversible capacity to the positive electrode's reversible capacity). When the battery is charged at a high rate, the R-corner region is more susceptible to lithium deposition than the straight region.

[0058] The current solution is to design a "yin-yang side" to improve corner lithium deposition by increasing the N / P ratio of the outer ring of the negative electrode. However, this approach comes at the expense of the cell's energy density, increasing the weight of the negative electrode coating on one side and the overall thickness of the cell.

[0059] The Chinese patent (application number: 202210778260.6) proposes a method to improve lithium deposition at the corners of the winding core by calculating and compensating the N / P ratio α at each corner, thereby reducing the risk of lithium deposition. The theoretical basis of this patent is: let the arc length of the negative electrode corner be S1, and the arc length of the positive electrode corner be S2, thereby obtaining the positive electrode super-negative electrode length ΔS=π(R2-R1). From this, the difference in the N / P ratio α between the corner area and the non-corner area is calculated, and the process compensation is performed according to the difference.

[0060] However, the patent's technical solution treats the R-angle as an arc for calculation during implementation. In reality, the inner circle has a greater curvature near the center, potentially closer to an ellipse or parabola, resulting in a simplified arc model. Furthermore, the coating compensation process in the R-angle area is difficult, making it unlikely for mass production.

[0061] In order to solve the above technical defects, the present application makes an improvement to the calculation method of the thinning value of the R corner area structure of the existing wound battery cell. Figure 1-4 As shown: In this application, the method for calculating the thinning value of the R corner area of ​​the wound battery cell includes the following steps:

[0062] S101, constructing a positive electrode curve equation based on the geometric position relationship of the positive electrode sheet in the R corner area of ​​the wound battery cell; constructing a negative electrode curve equation based on the geometric position relationship of the negative electrode sheet in the R corner area of ​​the wound battery cell;

[0063] S201, perform positive arc integration on the positive electrode curve equation to obtain L 正m , the negative electrode curve equation is integrated into the negative electrode arc to obtain L 负m ;L 正m Indicates the arc length of the positive electrode outside the mth circle, L 负m Table 1 shows the arc length of the inner circle of the mth circle;

[0064] S301 , constructing a thinning value calculation formula according to the relationship between the length of the positive electrode sheet and the length of the negative electrode sheet in the R-angle region of the wound battery cell, and calculating the thinning value of m turns in the R-angle region of the wound battery cell using the thinning value calculation formula.

[0065] The positive electrode curve equation in step S101 is:

[0066] y 正 =b m -d m x 2

[0067] The negative electrode curve equation is:

[0068] y 负 =c m -a m x 2

[0069] Among them, a m Indicates the opening degree of the negative electrode curve equation of the negative electrode sheet in the mth circle; b m Indicates the arc curvature radius of the positive electrode piece at the top of the R angle area; c m Indicates the arc curvature radius of the negative electrode at the top of the R angle area; d m Indicates the degree of opening of the equation of the negative electrode curve of the positive electrode sheet in the mth circle.

[0070] It is worth noting that the above formulas are derived from the analysis of the geometry of the R corner area, which gives the negative and positive curve equations respectively, and then the arc length at the corner and the thinning value of the N / P ratio α are obtained. In the process of constructing the negative curve equation, considering that the winding radius is related to the number of pole pieces, the total thickness of the pole piece increases with each additional turn, resulting in a larger outer circle radius. In order to describe this change in a geometric model that approximates a parabola or ellipse, let a mTake the inverse of a function:

[0071] a m =1 / c m

[0072] And c m >0: Indicates the radius of curvature of the negative electrode curve equation at x=0 in the mth circle R angle region. This can be understood as the distance between the top and the center of the circle. It is related to the thickness of the positive and negative electrodes and the separator.

[0073] Furthermore, a m >0 and represents the opening degree of the R angle curve equation of the mth (m=1, 2, 3....), a m with c m Satisfaction: a m =1 / c m ; further, c m >0,c m It also represents the radius of curvature of the arc at the top of the mth circle R angle (i.e., when x=0), which is related to the thickness of the positive electrode, negative electrode, and separator, such as Figure 1 As shown, it satisfies:

[0074] c m+1 =c m +h 正 +h 负 +2h 隔膜

[0075] Where m>0, c1=hpositive / 2+hnegative / 2+n*hdiaphragm, n represents the number of innermost winding diaphragm layers, which depends on the winding conditions. hpositive represents the thickness of the positive electrode, hneg represents the thickness of the negative electrode, and hdiaphragm represents the thickness of the diaphragm.

[0076] When m=0, the arc curvature radius c of the negative electrode at the top of the R angle area is m Satisfy the formula: c1=h 正 / 2+h 负 / 2+n*h 隔膜 , n represents the number of innermost winding diaphragm layers in the wound battery cell, and the specific number depends on the winding situation.

[0077] Furthermore, in the negative electrode curve equation: d m >0 indicates the opening degree of the R angle curve equation of the mth (m=1, 2, 3....) circle, d m with b m Satisfaction: d m =1 / b m ; further, b m >0,b m It represents the radius of curvature of the arc at the top of the R angle of the mth circle (i.e. when x=0), which is related to the thickness of the positive electrode, negative electrode and separator, such as Figure 1 As shown, it satisfies:

[0078] b m -c m =h 隔膜

[0079] Furthermore, in step S201, the expression of the positive arc integral is:

[0080]

[0081] Among them, the arc length (concave surface) of the positive electrode mth circle satisfies: Indicates the curve interval corresponding to the R angle area of ​​the positive electrode. Its design principle is to take into account the arc length formula Used to calculate the arc length of a parabola or approximate curve. After approximation or numerical integration, the arc length L of the convex surface of the circle is obtained. 正m .

[0082] Furthermore, the expression of the negative arc integral is:

[0083]

[0084] in, Ω represents the curve interval corresponding to the R angle area of ​​the negative electrode. The design principle is to take into account the arc length formula Used to calculate the arc length of a parabola or approximate curve. After approximation or numerical integration, the arc length L of the convex surface of the circle is obtained. 负m .

[0085] From this we can see that the calculation formula for the thinning value is:

[0086] λ m =△L m / L 正m

[0087] Among them, △L m △L is the portion where the length of the positive electrode sheet exceeds the length of the negative electrode sheet in the R corner area of ​​the wound battery cell. m The solution satisfies: △L m =L 正m -L 负m .

[0088] Furthermore, in order to obtain the thinned wound cell, specifically, the thinning value λm and the N / P ratio α of the straight area of ​​the wound cell are calculated according to any of the above-mentioned calculation methods for the thinning value of the R corner area structure of the wound cell; wherein α is the ratio of the reversible surface capacity of the negative electrode sheet to the reversible surface capacity of the positive electrode sheet; when α-λm≥CB min When α-λm <CB min, then thin the positive electrode sheet; CB min The minimum thinning value required for the set wound battery cell.

[0089] It is worth noting that λm can be understood as the "thinning value" or "negative electrode capacity ratio that needs to be reduced" in the mth circle R angle area. If the negative electrode N / P ratio in the straight area is defined as α, then the actual N / P ratio that can be achieved in the R angle area is α-λm. This is taken into account during the design process. When △L m The larger the value is, the larger the λm is, and the thickness of the negative electrode sheet or the coating amount needs to be thinned to a greater extent in the R angle area to make the N / P ratio α in this area close to the flat area or the preset lower limit.

[0090] Assume that the required minimum N / P ratio α (or CB value) is the set value CB min , for example 1.02. If α-λm <CB min , then the corresponding area of ​​the R angle needs to be thinned by laser or scribing to improve the local N / P ratio α and reduce the risk of lithium plating.

[0091] Further, such as Figure 3 The positive electrode sheet thinned by the method of the present application is shown, which includes a positive electrode outer arc region 1 and a positive electrode inner arc region 3 arranged on both sides of the current collector 2 in the thickness direction; wherein, the thinning region 31 is arranged in the positive electrode inner arc region 3, thereby further ensuring the fit of the positive electrode sheet in the R angle area, while reducing the impact of the thinning operation on the overall structural strength of the battery cell. In addition, the thinning design of the positive electrode inner arc region 3 can also effectively balance the stress distribution of the battery cell during the charge and discharge process, and improve the mechanical stability and cycle performance of the battery cell. In specific implementation, the position and size of the thinning region 31 can be flexibly adjusted according to the design requirements and actual production conditions of the battery cell to meet the needs of different application scenarios.

[0092] To further demonstrate the technical effects of the present invention, two specific embodiments are presented. By designing corresponding wound cells using the present invention, the technical effects of the present invention are further demonstrated. It should be noted that the following embodiments provide calculation results for the thinning value λm of the N / P ratio per turn of the R angle under different design parameters, as well as the decision-making process for thinning or not in actual processes.

[0093] Example 1

[0094] Wound battery cell performance model: 465055;

[0095] Design parameters:

[0096] 1) The thickness of the positive electrode sheet is 81 μm;

[0097] 2) The thickness of the negative electrode sheet is 66 μm;

[0098] 3) The thickness of the diaphragm is 8 μm;

[0099] 4) The number of innermost diaphragm layers n = 1;

[0100] 5) The number of winding turns of the battery cell is 1010

[0101] Among them, the thinning value of each circle λ m Calculation method:

[0102] Determine c1 and b1 based on the thickness of the innermost layer; for each layer (m=1,2,...,10), calculate c based on the amount of layer increase. m ,b m , thus obtaining a m =1 / c m with d m =1 / b m .

[0103] Perform numerical integration respectively and get L 负m With L 正m , calculate ΔL m =L 正m -L 负m . And λm satisfies the thinning value CB: λm=ΔL m / L 正m .

[0104] Table 1 below gives the λm corresponding to each circle (only circles 1, 2, 9, and 10 are shown as examples in this article).

[0105]

[0106] Table 1

[0107] As shown in Table 1, as the number of turns m increases, the thinning value λm of the R-angle area gradually decreases. This indicates that during the winding process of the battery cell, as the number of electrode layers accumulates, the difference in the N / P ratio of each turn in the R-angle area gradually decreases. In the early stages of battery cell design, especially in the first few turns, due to the small number of electrode layers, the difference in the N / P ratio in the R-angle area is large, so a large degree of thinning is required to adjust the N / P ratio and reduce the risk of lithium plating. However, as the number of winding turns increases, the number of electrode layers increases, the N / P ratio of the R-angle area gradually approaches the straight area, and the thinning value also decreases accordingly.

[0108] Furthermore, the data in Table 1 also shows that the thinning value λm for each R-corner region is calculated based on the specific design parameters of that region (such as the thickness of the positive and negative electrode sheets, and the thickness of the separator). This means that in practical applications, the thinning value of each R-corner region can be flexibly adjusted according to the specific design requirements and process conditions of the battery cell to achieve optimal battery cell performance and safety.

[0109] Example 2

[0110] The difference from Example 1 is its design parameters:

[0111] 1) The number of separator layers in the innermost circle of the wound cell is n=3.

[0112] 2) The thickness of the positive electrode sheet is 81 μm;

[0113] 3) The thickness of the negative electrode sheet is 66 μm;

[0114] 4) The thickness of the diaphragm is 8 μm.

[0115] Results: Because the number of separator layers in the innermost circle of the wound core increases, the initial curvature is different, and λ1 is 0.0758, which is slightly smaller than that in Example 1. When the 10th circle is wound, λ 10 If the N / P ratio of the straight area is still α, the number of turns required to be thinned in the R-angle area is less than that in Example 1.

[0116] Other details that are the same as those in Example 1 are not described in detail in this example.

[0117] Example 3

[0118] The difference from Example 1 is its design parameters:

[0119] Wound battery cell performance model: 466494;

[0120] Design parameters:

[0121] 1) The thickness of the positive electrode sheet is 70 μm;

[0122] 2) The thickness of the negative electrode sheet is 86 μm;

[0123] 3) The thickness of the diaphragm is 6 μm.

[0124] 4) The number of innermost diaphragm layers n = 1;

[0125] 5) The number of winding turns is 20.

[0126] result:

[0127] λ1=0.0870,λ 10 =0.0051,λ 20 =0.0025

[0128] Because the negative electrode is thicker, the overall initial curvature increases, but when it reaches the outer circle, the λm value gradually decreases.

[0129] Other details that are the same as those in Example 1 are not described in detail in this example.

[0130] Furthermore, in order to more intuitively show the difference between the data of Examples 1-3, the data of Examples 1-3 are shown in Table 2 below:

[0131]

[0132] Table 2

[0133] By comparing the data of Examples 1, 2, and 3, we can further understand the flexibility and effectiveness of the technical solution of this application in practical applications. In Example 1, we used standard design parameters and found that as the number of winding turns increased, the thinning value of the R angle area gradually decreased. This law was also verified in Example 2. Although the initial thinning value λ1 decreased due to the increase in the number of innermost diaphragm layers, the final thinning value λ1 at the 10th turn was λ1. 10 The same as in Example 1, both are 0.0051. This shows that the technical solution of the present application has good adaptability to battery cells with different design parameters.

[0134] It is worth noting that in Example 1, when winding to the 9th and 10th turns, the thinning value λm is already very small, 0.0057 and 0.0051 respectively. This shows that under these two turns, the N / P ratio of the R angle area is already very close to the straight area, so no significant thinning operation is required. This result also verifies the effectiveness of the technical solution of the present application, that is, by accurately calculating the thinning value of the R angle area of ​​each turn, the N / P ratio of the battery cell can be accurately controlled, thereby reducing the risk of lithium plating while ensuring the energy density of the battery cell. If α-λm≥CB min , then thinning is not required to avoid excessive loss of active substances and maintain energy density.

[0135] In Example 3, we changed the performance model and design parameters of the battery cell, including the thickness of the positive electrode sheet, the thickness of the negative electrode sheet, the thickness of the separator, and the number of winding turns. Although these parameters are different from those of Examples 1 and 2, the results of Example 3 are still consistent with our previous observations, that is, as the number of winding turns increases, the thinning value of the R angle area gradually decreases. In particular, in Example 3, due to the thicker negative electrode sheet, the overall initial curvature increases, resulting in a larger initial thinning value λ1. However, as the winding progresses, by the 20th turn, the thinning value λ 20 It has decreased to 0.0025, which shows that the N / P ratio of the R corner area is very close to that of the straight area.

[0136] In summary, the technical solution of this application achieves precise control of the N / P ratio of the battery cell by accurately calculating the thinning value of each R corner area. This method is not only applicable to battery cells with different design parameters, but also can be flexibly adjusted according to the specific design requirements and process conditions of the battery cell in actual application.

[0137] The above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for calculating the thinning value of the R corner area of ​​a wound battery cell, characterized in that: The following steps are included: S101, constructing a positive electrode curve equation based on the geometric position relationship of the positive electrode sheet in the R corner area of ​​the wound battery cell; constructing a negative electrode curve equation based on the geometric position relationship of the negative electrode sheet in the R corner area of ​​the wound battery cell; S201, perform positive arc integration on the positive electrode curve equation to obtain L 正m , the negative electrode curve equation is integrated into the negative electrode arc to obtain L 负m ;L 正m Indicates the arc length of the positive electrode outside the mth circle, L 负m Table 1 shows the arc length of the inner circle of the mth circle; S301 , constructing a thinning value calculation formula according to the relationship between the length of the positive electrode sheet and the length of the negative electrode sheet in the R-angle region of the wound battery cell, and calculating the thinning value of m turns in the R-angle region of the wound battery cell using the thinning value calculation formula.

2. The method for calculating the R-angle thinning value of a wound battery cell according to claim 1, characterized in that: The positive electrode curve equation in step S101 is: y 正 =b m -d m x 2 The negative electrode curve equation is: y 负 =c m -a m x 2 Among them, a m b represents the opening degree of the negative electrode curve equation of the negative electrode sheet in the mth circle; m represents the arc curvature radius of the positive electrode piece at the top of the R angle area; c m The radius of curvature of the arc of the negative electrode at the top of the R angle area; d m Indicates the degree of opening of the equation of the negative electrode curve of the positive electrode sheet in the mth circle.

3. The method for calculating the thinning value of the R corner area of ​​a wound battery cell according to claim 2, characterized in that: The arc curvature radius c of the negative electrode piece at the top of the R angle area m The thickness h of the positive electrode sheet 正 , the thickness h of the negative electrode sheet 负 and the thickness of the diaphragm h 隔膜 satisfy: c m+1 =c m +h 正 +h 负 +2h 隔膜 Where m>0.

4. A method for calculating the thinning value of the R corner area of ​​a wound battery cell according to claim 3, characterized in that: When m=0, the arc curvature radius c of the negative electrode sheet at the top of the R angle area is m Satisfy the formula: c1=h 正 / 2+h 负 / 2+n*h 隔膜 , wherein n represents the number of innermost winding separator layers in the wound battery cell.

5. The method for calculating the thinning value of the R corner area of ​​a wound battery cell according to claim 2, characterized in that: The curvature radius d of the arc of the positive electrode sheet at the top of the R angle area m The arc curvature radius c of the negative electrode piece at the top of the R angle area m and the thickness of the diaphragm h 隔膜 satisfy: b m -c m =h 隔膜 Where m>0.

6. The method for calculating the R-angle thinning value of a wound battery cell according to claim 1, characterized in that: The expression of the positive arc integral in step S201 is: The expression of the negative arc integral is:

7. The method for calculating the R-angle thinning value of a wound battery cell according to claim 1, characterized in that: The calculation formula of the thinning value is: l m =△L m / L 正m Among them, △L m The length of the positive electrode sheet exceeds the length of the negative electrode sheet in the R corner area of ​​the wound battery cell, △L m The solution satisfies: △L m =L 正m -L 负m .

8. A method for thinning the R corner area of ​​a wound battery cell, characterized in that: The thinning value λm and the N / P ratio α of the straight area of ​​the wound cell are calculated according to the calculation method of the thinning value of the R corner area structure of the wound cell according to any one of claims 1 to 7; wherein α is the ratio of the reversible surface capacity of the negative electrode sheet to the reversible surface capacity of the positive electrode sheet; when α-λm≥CB min When α-λm <CB min , then the positive electrode sheet is thinned; CB min The minimum thinning value required for the set wound battery cell.

9. A method for thinning the R corner area of ​​a wound battery cell according to claim 8, characterized in that: The N / P ratio α in the flat region satisfies: 1<α<1.

2.

10. A battery cell, characterized in that: The battery is prepared by the method for thinning the R corner area of ​​the wound battery cell as described in any one of claims 8-9.

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