Winding battery, design method thereof and foil resistance value calculation method

Abstract

The invention provides a winding battery, a design method thereof and a foil resistance value calculation method. The foil resistance value calculation method comprises the following steps: S1, determining a mathematical spiral mode of a winding core and size information of a diaphragm, a positive plate and a negative plate; s2, establishing a polar coordinate system, and determining a pole and a polar axis; s3, fitting spiral equations of the diaphragm, the positive plate and the negative plate in the polar coordinates; and S4, fitting a parameter equation of a welding line in the polar coordinate system, combining the spiral equation and the parameter equation, solving all intersection points, generating a geometric solid foil of the positive electrode foil or the negative electrode foil according to welding spot information, and calculating the resistance value of the geometric solid foil through a simulation experiment. The welding spot information is solved through a mathematical model, the resistance value of the geometric solid foil is correspondingly calculated through a simulation experiment, the resistance value of the positive electrode foil or the negative electrode foil can be rapidly calculated without actually winding and welding a winding core, and rapid screening and optimization of welding wire design are achieved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a wound battery and a design method thereof, and a foil resistance calculation method. Background Art

[0002] A wound battery is usually composed of a winding core, an electrolyte and a shell, wherein the two ends of the shell correspond to the external positive electrode and the external negative electrode of the battery respectively. The electrolyte serves as a medium for ion transmission in the battery, and the winding core is used to convert chemical energy into electrical energy. The winding core is usually formed by winding a four-layer structure of a diaphragm, a negative electrode sheet, a diaphragm and a positive electrode sheet stacked in sequence using a winding process. The negative electrode sheet includes a negative electrode foil and a negative electrode material layer coated on at least one surface of the negative electrode foil, and the positive electrode sheet includes a positive electrode foil and a positive electrode material layer coated on at least one surface of the positive electrode foil. One end face of the column formed by the positive electrode sheet after winding is connected to the external positive electrode of the shell, and the other end face of the column formed by the negative electrode sheet after winding is connected to the external negative electrode of the shell.

[0003] The common winding process of the winding core is to first roll the diaphragm to a predetermined length by means of a fixed winding needle, then insert the negative electrode sheet into the space between the two layers of diaphragm and roll it together with the diaphragm to a predetermined length, and finally attach the positive electrode sheet to the outside of the diaphragm to achieve the co-winding of the diaphragm, the negative electrode sheet and the positive electrode sheet until the winding of the winding core is completed. Among them, the predetermined length of the diaphragm when rolled empty is the diaphragm insertion length, and the predetermined length of the negative electrode sheet when rolled together with the diaphragm is the negative electrode sheet insertion length. After the end face formed by the winding of the negative electrode foil is welded to the negative electrode collector disk, it is connected to the external negative electrode of the shell. After the end face formed by the winding of the positive electrode foil is welded to the positive electrode collector disk, it is connected to the external positive electrode of the shell.

[0004] Usually, the end faces of the positive and negative electrode foils are welded to the positive and negative electrode collector plates respectively in a linear welding design. For example, CN117219972B discloses the use of three linear welding wires on the collector plate to connect to the end face of the coiled foil, and CN112290168B discloses the use of three or five linear welding wires to connect to the end face of the coiled foil. Among them, the length, number and arrangement design of the welding wires will affect the conductive path of the foil, and the difference in the conductive path will result in different resistance values ​​when the material and thickness of the foil are the same, and the internal resistance conditions of the formed battery system are also different. Therefore, there is an urgent need for a method that can quickly calculate the resistance of the positive or negative electrode foil under different welding wire designs, so as to provide a certain theoretical basis for evaluating the design quality of the collector plate welding wire or optimizing the collector plate welding wire design. Summary of the invention

[0005] In order to solve the above problems and realize the rapid calculation of the resistance of the positive electrode foil or the negative electrode foil in the battery system under the welding wire design, the first aspect of the present application provides a method for calculating the resistance of the foil, comprising the following steps:

[0006] S1: according to the winding mode of the winding core, determining the mathematical spiral mode, thickness, width in the height direction of the winding core, and corresponding winding arc length of the separator, the positive electrode sheet, and the negative electrode sheet in the orthographic projection view of the end surface of the winding core;

[0007] S2: establishing a polar coordinate system in the orthographic projection view of the end surface of the winding core, wherein the polar coordinate system takes the geometric center of the winding needle in the orthographic projection view of the end surface of the winding core as the pole, and takes the line connecting the pole and the starting winding point of the diaphragm as the polar axis;

[0008] S3: fitting the spiral equations of the winding arc length, polar angle and polar diameter of the separator, the positive electrode sheet and the negative electrode sheet in the polar coordinates; and

[0009] S4: According to the shape, size, quantity and orientation of the welding wire, a parametric equation of the welding wire is fitted in the polar coordinate system, the spiral equation and the parametric equation are combined to solve all intersections, each of which corresponds to the geometric center of a welding point, and a geometric entity foil of the positive electrode foil or the negative electrode foil is generated according to the size information of the welding point, and the resistance value of the geometric entity foil is calculated through simulation experiments.

[0010] In some optional embodiments, the mathematical spiral is an Archimedean spiral, and the polar diameter r and the polar angle θ satisfy the relationship: r=a+bθ, where a is the polar diameter of the starting winding point, b is the radius increment per unit polar angle, and the polar angle θ 1 With polar angle θ 2 The arc length of the spiral between l satisfy:

[0011] In some optional implementations, the establishment of the spiral equation of the winding arc length, polar angle and polar diameter further includes the following steps:

[0012] S31: With the winding needle radius r a is the polar diameter of the starting winding point of the diaphragm, and determines the parameters: the diaphragm thickness sep t With the length of the position Negative electrode insertion length and winding arc length neg l , the thickness of the negative electrode foil Negative electrode material layer thickness t , the winding arc length of the positive electrode is pos l , the thickness of the positive electrode foil And the thickness of the positive electrode material layer pos t ;as well as

[0013] S32: according to the radius increment sep of the unit polar angle when the diaphragm is in place and unwound b , the radius increment per unit polar angle when the negative electrode sheet is in place is neg b And the radius increment pos of the unit polar angle when the positive electrode sheet is wound b , respectively calculate the polar angle and polar diameter of the insertion end point of the diaphragm and the negative electrode sheet, and the polar angle and polar diameter of the winding end point of the positive electrode sheet, and establish the spiral equations of the polar angle, polar diameter and arc length of the negative electrode sheet and the positive electrode sheet respectively.

[0014] In some optional implementations, the S32 further includes the following steps:

[0015] S321: The sep b By formula It is found that the relationship between the polar diameter and the polar angle during the diaphragm insertion stage is: sep =r a +sep b θ sep , the diaphragm insertion length is Establishing Relationship I: where θ 0 = 0, solve the polar angle of the end point of the diaphragm further, Solve for the polar diameter of the diaphragm entry end point

[0016] S322: The neg b By formula It is found that the relationship between the pole diameter and the pole angle during the negative electrode sheet insertion stage corresponds to: The end point of the diaphragm is the starting point of the negative electrode sheet. Establish relationship II: Solve the polar angle of the negative electrode sheet entry end point further, Solve the pole diameter of the negative electrode sheet at the end point of insertion

[0017] S323: the pos b By formula The end point of the negative electrode sheet is the starting point of the positive electrode sheet winding. According to the winding arc length pos of the positive electrode sheet l , establish relation III: Solve the polar angle of the winding end point of the positive electrode sheet Further according to the formula Solve the pole diameter r of the winding end point of the positive electrode sheet b ;as well as

[0018] S324: Any two polar angles θ of the positive electrode sheet 1 With θ 2 The length of the arc segment of the spiral satisfies:

[0019] Any two polar angles θ of the negative electrode sheet in the insertion stage 1 With θ 2 The length of the arc segment of the spiral satisfies:

[0020] Any two polar angles θ of the negative electrode sheet during the co-winding phase with the positive electrode sheet after the placement phase 1 With θ 2 The arc length of the spiral satisfies: Said For the diaphragm The polar diameter at the polar angle,

[0021] In some optional embodiments, the solution method of the relationship I-III includes at least one of a heuristic algorithm and a numerical optimization algorithm, the heuristic algorithm includes a genetic algorithm, a particle swarm algorithm, a differential evolution algorithm and an ant colony algorithm, and the numerical optimization algorithm includes a least squares method, a bisection method, a gradient descent method, a Newton method and a conjugate gradient method.

[0022] In some optional implementations, the S4 further includes the following steps:

[0023] S41: The line connecting the geometric symmetry center of each welding line and the pole forms a welding line polar angle, and a list of welding line polar angles θ of all welding lines is listed. list , and corresponds to the welding line polar angle list θ list Match the parameter equation of the corresponding welding wire, solve the parameter equation of the welding wire and the spiral equation of the positive electrode sheet or the negative electrode sheet simultaneously, and use the range of each welding wire on the polar diameter as a constraint condition to obtain n intersection points of all the welding wires and the negative electrode sheet or the positive electrode sheet, and divide the spiral corresponding to the negative electrode sheet or the positive electrode sheet into n+1 arc segments corresponding to the intersection points, solve the arc segment length of each arc segment, and, according to the welding wire width w data, correct the intersection point to the welding point, and correct the foil length gap corresponding to the arc segment length length , the list is obtained (gap length , w);

[0024] S42: Based on the foil length between each two adjacent welding points and the welding point width list (gap length, w), combining the thickness of the corresponding positive electrode foil or the negative electrode foil, the winding arc length parameter of the positive electrode sheet or the negative electrode sheet, and the width parameter of the positive electrode sheet or the negative electrode sheet in the height direction of the winding core, generating a geometric entity corresponding to the foil in the finite element software; and

[0025] S43: Conduct a simulation experiment in the finite element software, input the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each of the welding points, use the welding points as current input terminals to input a specified current I into the geometric entity foil, and calculate the average potential Vup of the current input terminal surface and the potential Vlb of the ground terminal surface by the finite element method based on the conductivity coefficient σ of the foil, and output the resistance value of the geometric entity foil.

[0026] In some optional embodiments, the parametric equation of the welding wire is used to describe the welding trajectory of the welding wire in the polar coordinate system, the welding trajectory is a straight line or curve of a finite length, the distance between the endpoint of the welding trajectory close to the pole and the pole is d1, and the width of the welding trajectory in the polar radius direction of the polar coordinate system is d2.

[0027] In some optional embodiments, the welding trajectory is a straight line extending through the pole, and the width of each welding line is w, and the combination of polar angles corresponding to each welding trajectory is the welding line polar angle list θ list , the gap length , w) The solution method of the list includes the following steps:

[0028] S411: Determine the spiral equation r(θ)=a+bθ of the positive electrode sheet or the negative electrode sheet where the welding point is located, determine the parameters a, b and the effective polar diameter range [r1, r2] of the spiral, and input θ list , input the polar diameter range of each welding track [d1, d1+d2], and the width w of the welding line;

[0029] S412: Define the arc length integral formula Any two polar angles θ star To the polar angle θ end The arc length calculation formula is: length a,b,θ star ,θ end )=L(a,b,θ end -L(a,b,θ star ); S413: Initialize θ to 0, obtain θ list Any polar angle value θ 1 , constrain r1≤r(θ 1 )≤r2, calculate the polar diameter d=r(θ 1), if d∈d1,d1+d2, then calculate the arc length: length sec =L(θ 1 )-L(0), record θ 1 ,d,length sec , set the increment to 2π, update θ = θ 1 +2π, recalculate r(θ), merge θ 1 The corresponding θ, d, length of all the welding wires that meet the conditions sec ;

[0030] S414: Traversing θ list For each polar angle value, record the θ, d, and length of all welding lines that meet the conditions. sec ; S415: Sort θ, d, length in ascending order according to the value of θ sec , according to the width w data of the welding line, correct the length sec for gap length , gap length =length sec -w;

[0031] S416:θ,d,length sec The first set of data in corresponds to [θa, da, length seca ], the last set of data corresponds to: [θb, db, length secb ], the total length of the spiral is L, and the spiral includes the first arc: Final Arc and each set of middle arcs except the first arc and the last arc; and

[0032] S417: Output the first arc (gap lengtha , w), the middle arc of each group (gap length , w) and the terminal arc gapl eng thb.

[0033] In some optional embodiments, the (gap length , w) The solution method of the list can be converted into a computer programming language and applied to a computer terminal, wherein the computer programming language includes at least one of java, C, C++ and mathlab.

[0034] In some optional implementations, the S43 further includes the following steps:

[0035] S431: inputting the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each welding point;

[0036] S432: According to the material properties of the foil material actually used, the conductivity σ is defined, the potential Vlb of the grounded end surface is defined to be equal to 0, and the normal component of the current is preset to be zero;

[0037] S433: inputting a specified current I into the geometric entity foil material with the welding point as the current input end, each welding point corresponding to a node of the current input end surface;

[0038] S434: Extract the potential value V of each node of the current input end surface i , calculate the area weight Dai of each node, and take the weighted average potential value of all nodes to get V up ;as well as

[0039] S435: The resistance R of the geometric entity foil is: R = (V up -V lb ) / I.

[0040] In some optional embodiments, the finite element software includes at least one of croe, solidwork, comsol, ansys and ABAQUS.

[0041] A second aspect of the present application provides a design method for a wound battery, the design method for a wound battery comprising the following steps:

[0042] S01: Determine the three-dimensional size information of the separator, negative electrode sheet, positive electrode sheet and winding needle and the winding method of the winding core; S02: Design the welding wire scheme between the positive electrode foil and the negative electrode foil and the corresponding positive electrode collector and negative electrode collector respectively;

[0043] S03: calculating the resistance of the positive electrode foil or the negative electrode foil respectively according to any of the foil resistance calculation methods described above;

[0044] S04: adjusting the three-dimensional size information of the separator, the negative electrode sheet, the positive electrode sheet and the winding needle, the winding method of the winding core and the welding wire scheme, until a battery design scheme with the smallest resistance value of the positive electrode foil or the negative electrode foil is screened out.

[0045] A third aspect of the present application provides a wound battery, wherein the wound battery is a wound battery designed according to the above-mentioned design method.

[0046] Furthermore, the wound battery is a lithium-ion cylindrical battery.

[0047] This application has at least the following technical effects:

[0048] 1) The first aspect of the present application provides a method for calculating the resistance of a foil of a wound battery, wherein a polar coordinate system is established in an orthographic projection view of the end face of a winding core, and the geometric center of the winding needle in the orthographic projection view of the end face of the winding core is taken as the pole, and the line connecting the pole and the starting winding point of the diaphragm is taken as the polar axis, and the spiral equations of the diaphragm, the positive electrode sheet and the negative electrode sheet are fitted in a mathematical spiral manner, and the parameter equation of the welding wire is combined, and all the intersections of the spiral and the welding wire are solved by the simultaneous equations, so as to determine the three-dimensional geometric parameters of the geometric entity foil and the distribution of the welding points, and the resistance of the geometric entity foil is calculated correspondingly through simulation experiments, without actually performing the winding of the winding core and the welding operation between the winding core and the current collector, the resistance of the positive electrode foil or the negative electrode foil under the determined welding wire design in the battery system can be quickly calculated, which saves time and effort, and can also quickly screen out the welding wire design with smaller interface contact resistance, and can also provide a theoretical basis for evaluating the design quality of the current collector wire or optimizing the current collector wire design.

[0049] 2) The second aspect of the present application provides a design method for a wound battery. By using the above-mentioned foil resistance calculation method, parameters can be adjusted from multiple dimensions such as the core winding method, the three-dimensional size information of the diaphragm, the negative electrode sheet, the positive electrode sheet and the winding needle, and the welding wire design. By comparing the resistance of the positive electrode foil or the negative electrode foil in the battery system under various parameters, the battery design optimization direction is determined, the resistance of the positive electrode foil or the negative electrode foil in the battery system is minimized, and the optimal battery design scheme is formed.

[0050] 3) The third aspect of the present application provides a wound battery. The wound battery obtained by the above-mentioned design method, the positive and negative electrode foils can be adapted to the optimal welding wire arrangement design, thereby minimizing the resistance in the battery system, reducing the energy loss when the current passes through, improving the battery's charging and discharging efficiency and stability, extending the service life and improving the safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0052] Figure 1 is a schematic diagram of a three-dimensional structure of a wound battery in an optional embodiment of the present application with the core part of the wound battery unfolded;

[0053] Figure 2 is a schematic diagram of the welding wire at the end surface of the winding core in Example 1 of the present application;

[0054] Figure 3It is a schematic diagram of a geometric solid foil generated in finite element software after solving the welding point and segment arc length information in Example 1 of the present application;

[0055] Figure 4 It is a partial enlarged view of the current input end surface of the negative electrode foil in Example 1 of the present application;

[0056] Figure 5 is a schematic diagram of the welding wire at the end surface of the winding core in Example 2 of the present application;

[0057] Figure 6 is a schematic diagram of the welding wire at the end surface of the winding core in Example 3 of the present application;

[0058] Figure 7 It is a plan view of an orthographic projection of the end face of a winding core of a wound battery in an optional embodiment of the present application, in which a separator, a negative electrode sheet and a positive electrode sheet are wound together.

[0059] Figure numerals: 2-winding core, 21-positive electrode sheet, 210-positive electrode active material layer, 212-positive electrode foil, 23-separator, 25-negative electrode sheet, 250-negative electrode active material layer, 252-negative electrode foil, 3-welding wire, 30-welding point, 32-arc segment. DETAILED DESCRIPTION

[0060] Embodiments of the present embodiment are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present embodiment, and should not be construed as limiting the present embodiment.

[0061] In the description of this embodiment, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this embodiment.

[0062] In the description of this embodiment, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0063] In the description of this embodiment, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this embodiment based on the specific content of the technical solution.

[0064] A first aspect of the present application provides a method for calculating the resistance of a foil of a wound battery, the method comprising the following steps:

[0065] S1: According to the winding mode of the winding core 2, determine the mathematical spiral mode, thickness, width in the height direction of the winding core 2 and the corresponding winding arc length of the separator 23, the positive electrode sheet 21 and the negative electrode sheet 25 in the orthographic projection view of the end surface of the winding core 2;

[0066] S2: Establishing a polar coordinate system in the orthographic projection view of the end surface of the winding core 2, wherein the polar coordinate system takes the geometric center of the winding needle in the orthographic projection view of the end surface of the winding core 2 as the pole, and takes the line connecting the pole and the starting winding point of the diaphragm 23 as the polar axis;

[0067] S3: fitting the spiral equations of the winding arc length, polar angle and polar diameter of the separator 23, the positive electrode sheet 21 and the negative electrode sheet 25 in the polar coordinates; and

[0068] S4: According to the shape, size, quantity and orientation of the welding wire 3, a parametric equation of the welding wire 3 is fitted in the polar coordinate system, the spiral equation and the parametric equation are combined to solve all intersections, each of which corresponds to the geometric center of a welding point 30, and the geometric entity foil of the positive foil 212 or the negative foil 252 is generated according to the size information of the welding point 30, and the resistance value of the geometric entity foil is calculated through simulation experiments.

[0069] Furthermore, the mathematical spiral is an Archimedean spiral, and the polar diameter r and the polar angle θ satisfy the relationship: r=a+bθ, where a is the polar diameter of the starting winding point, b is the radius increment per unit polar angle, and the polar angle θ 1 With polar angle θ 2 The arc length of the spiral between l satisfy:

[0070] It should be noted that, taking the positive electrode sheet 21 as an example, the positive electrode sheet 21 is formed by coating a positive electrode material on at least one side of the positive electrode foil 212. The positive electrode material is solidified to form the positive electrode material layer 210. Therefore, the positive electrode foil 212 and the positive electrode material layer 210, the negative electrode foil 252 and the negative electrode material layer 250 can be regarded as a sheet-like entity. Furthermore, the spiral equation of the positive electrode sheet 21 can be equivalent to the spiral equation of the positive electrode foil 212, and the spiral equation of the negative electrode sheet 25 can be equivalent to the spiral equation of the negative electrode foil 252.

[0071] A polar coordinate system is established in the orthographic projection view of the end face of the winding core 2, and the geometric center of the winding needle in the orthographic projection view of the end face of the winding core 2 is taken as the pole, and the line connecting the pole and the starting winding point of the diaphragm 23 is taken as the polar axis. The spiral equations of the diaphragm 23, the positive electrode sheet 21 and the negative electrode sheet 25 are fitted in a mathematical spiral manner. Combined with the parameter equation of the welding wire 3, all the intersections of the spiral and the welding wire 3 are solved by the simultaneous equations, so as to determine the three-dimensional geometric parameters of the geometric entity foil and the distribution of the welding points 30. The resistance of the geometric entity foil is calculated correspondingly through the simulation experiment. Without actually performing the winding of the winding core 2 and the welding operation between it and the current collector, the resistance of the positive electrode foil 212 or the negative electrode foil 252 in the battery system under the determined welding wire 3 design can be quickly calculated, which saves time and effort and can quickly screen out the welding wire 3 design with smaller interface contact resistance, and at the same time provides a theoretical basis for evaluating the design quality of the current collector welding wire 3 or optimizing the design of the current collector welding wire 3.

[0072] In some optional implementation methods, the establishment of the spiral equation of the winding arc length, polar angle and polar diameter further includes the following steps:

[0073] S31: With the winding needle radius r a is the diameter of the starting winding point of the diaphragm 23, and determines the parameters: the thickness sep of the diaphragm 23 t With the length of the position The insertion length of the negative electrode sheet 25 and winding arc length neg l , the thickness of the negative electrode foil 252 Negative electrode material layer 250 thickness neg t , the winding arc length pos of the positive electrode sheet 21 l , the thickness of the positive electrode foil 212 and the thickness of the positive electrode material layer 210 is pos t ;as well as

[0074] S32: according to the radius increment sep per polar angle when the diaphragm 23 is in place and unwound b , the radius increment per unit polar angle when the negative electrode sheet 25 is in place is neg b and the radius increment pos of the unit polar angle when the positive electrode sheet 21 is wound b , respectively, the polar angle and polar diameter of the insertion end point of the diaphragm 23 and the negative electrode sheet 25, and the polar angle and polar diameter of the winding end point of the positive electrode sheet 21 are calculated, and the spiral equations of the polar angle, polar diameter and arc length of the negative electrode sheet 25 and the positive electrode sheet 21 are established respectively.

[0075] In some optional implementation methods, the S32 further includes the following steps:

[0076] S321: the sep b By formula It is found that the relationship between the polar diameter and the polar angle of the diaphragm 23 in the stage of being in place is: sep =r a +sep b θ sep , the diaphragm 23 is inserted into the position with a length of Establishing Relationship I: where θ 0 = 0, solve the polar angle of the end point of the diaphragm 23 further, Solve the polar diameter of the end point of the diaphragm 23

[0077] S322: The neg b By formula It is found that the relationship between the polar diameter and the polar angle of the negative electrode sheet 25 in the stage of being in place corresponds to: The insertion end point of the diaphragm 23 is the insertion starting point of the negative electrode sheet 25. Establish relationship II: Solve the polar angle of the negative electrode sheet 25 at the end point of insertion further, Solve the pole diameter of the negative electrode sheet 25 at the end point of insertion as well as

[0078] S323: the pos b By formula It is found that the end point of the negative electrode sheet 25 is the starting point of the winding of the positive electrode sheet 21. According to the winding arc length pos of the positive electrode sheet 21 l , establish relation III: Solve the polar angle of the winding end point of the positive electrode sheet 21 Further according to the formula Solve the pole diameter r of the winding end point of the positive electrode sheet 21 b ;as well as

[0079] S324: Any two polar angles θ of the positive electrode sheet 21 1 With θ 2 The length of the spiral arc segment 32 satisfies: The negative electrode sheet 25 has any two polar angles θ in the in-position stage. 1 With θ 2 The length of the spiral arc segment 32 satisfies: Any two polar angles θ of the negative electrode sheet 25 during the co-winding phase with the positive electrode sheet 21 after the placement phase 1 With θ2 The arc length of the spiral satisfies: Said The diaphragm 23 is The polar diameter at the polar angle,

[0080] In the specific implementation process, the thickness of the diaphragm 23 is sep t The thickness of the negative electrode sheet 25 includes the thickness of the negative electrode foil 252. and the thickness of the negative electrode material layer 250 is neg t , usually, The range is 4-15μm, the neg t The range is 50-200 μm, and the thickness of the positive electrode sheet 21 includes the thickness of the positive electrode foil 212 and the thickness pos of the positive electrode material layer 210 t , usually, The range is 6-20μm, the pos t The range is 60-200 μm. t With pos t Corresponds to the total thickness of the negative electrode material and the positive electrode material, that is, when both sides of the foil are coated with materials, negative t With pos t Corresponds to the total thickness of the double-sided material.

[0081] It should be noted that see Figure 1 and Figure 7 , when winding the winding core 2, the diaphragm 23 will be pre-wound on the winding needle, and the diaphragm 23 includes two layers, and the corresponding thickness increment is the thickness of the diaphragm 23 that increases by 2 times for each winding. The starting point of the negative electrode sheet 25 is the middle of the two layers of the diaphragm, and its starting polar diameter for insertion should be the ending polar diameter of the inner diaphragm 23 for insertion. However, since the thickness of the diaphragm 23 differs from that of the negative electrode sheet 25 by more than ten times, in order to simplify the spiral equation, no additional distinction is made between the two layers of diaphragms 23, and the starting polar diameter of the negative electrode sheet 25 for insertion is simplified to the ending polar diameter of the diaphragm 23 for insertion, that is, the ending polar diameter of the outer diaphragm 23 for insertion. Moreover, when the negative electrode sheet 25 is wound together with the positive electrode sheet 21 after insertion, the starting polar diameter of the negative electrode sheet 25 also corresponds to the θ of the diaphragm 23 corresponding to the negative electrode sheet 25 when the negative electrode sheet 25 is inserted. negs The polar diameter r sepu .

[0082] In the specific implementation process, the solution method of the relationship I-III includes at least one of a heuristic algorithm and a numerical optimization algorithm, the heuristic algorithm includes a genetic algorithm, a particle swarm algorithm, a differential evolution algorithm and an ant colony algorithm, and the numerical optimization algorithm includes a least squares method, a bisection method, a gradient descent method, a Newton method and a conjugate gradient method. The above methods can all be used to solve the polar angle values ​​in the relationship I-III.

[0083] In some optional implementation methods, the S4 further includes the following steps:

[0084] S41: The line connecting the geometric symmetry center of each welding line 3 and the pole forms a welding line polar angle, and a list of welding line polar angles θ of all welding lines 3 is listed. list , and corresponds to the welding line polar angle list θ list Match the parameter equation of the corresponding welding wire 3, solve the parameter equation of the welding wire 3 and the spiral equation of the positive electrode sheet 21 or the negative electrode sheet 25 simultaneously, and use the range of each welding wire 3 on the polar diameter as a constraint condition to obtain n intersections of all the welding wires 3 and the negative electrode sheet 25 or the positive electrode sheet 21, and the intersections correspond to dividing the spiral corresponding to the negative electrode sheet 25 or the positive electrode sheet 21 into n+1 arc segments 32, solve the arc segment length of each arc segment 32, and, according to the width w data of the welding wire 3, correct the intersection to the welding point 30, and correct the foil length gap corresponding to the length of the arc segment 32 length , the list is obtained (gap length , w);

[0085] S42: Based on the length of the foil between each two adjacent welding points 30 and the width list of the welding points 30 (gap length , w), combining the thickness of the corresponding positive electrode foil 212 or the negative electrode foil 252, the winding arc length data of the positive electrode sheet 21 or the negative electrode sheet 25, and the width data of the positive electrode sheet 21 or the negative electrode sheet 25 in the height direction of the winding core 2, generating the geometric entity corresponding to the foil in the finite element software;

[0086] S43: Conduct a simulation experiment in the finite element software, input the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each of the solder joints 30, use the solder joints 30 as current input terminals to input a specified current I into the geometric entity foil, and calculate the average potential Vup of the current input terminal surface and the potential Vlb of the ground terminal surface using the finite element method based on the conductivity coefficient σ of the foil, and output the resistance value of the geometric entity foil.

[0087] In some optional implementation methods, the parametric equation of the welding line 3 is used to describe the welding trajectory of the welding line 3 in the polar coordinate system, the welding trajectory is a straight line or curve of a finite length, the distance between the endpoint of the welding trajectory close to the pole and the pole is d1, and the width of the welding trajectory in the polar radius direction of the polar coordinate system is d2.

[0088] In some optional implementation methods, the welding trajectory is a straight line extending through the pole, and the width of each welding line 3 is w, and the combination of polar angles corresponding to each welding trajectory is the welding line polar angle list θ list , the gap length , w) The solution method of the list includes the following steps:

[0089] S411: Determine the spiral equation r(θ)=a+bθ of the positive electrode sheet 21 or the negative electrode sheet 25 where the welding point 30 is located, determine the parameters a, b and the effective polar diameter range [r1, r2] of the spiral, and input θ list , input the polar diameter range [d1, d1+d2] of each welding track, and the width w of the welding line 3;

[0090] S412: Define the arc length integral formula Any two polar angles θ star To the polar angle θ end The arc length calculation formula is: length (a,b,θ star ,θ end )=L(a,b,θ end )-L(a,b,θ star );

[0091] S413: Initialize θ to 0, obtain θ list Any polar angle value θ 1 , constrain r1≤r(θ 1 )≤r2, calculate the polar diameter d=r(θ 1 ), if d∈d1,d1+d2, then calculate the arc length: length sec =L(θ 1 )-L(0), record θ 1 ,d,length sec , set the increment to 2π, update θ = θ 1 +2π, recalculate r(θ), merge θ 1 The corresponding θ, d, length of all the welding wires 3 that meet the conditions sec ;

[0092] S414: Traversing θ listFor each polar angle value, record the θ, d, length of all welding lines 3 that meet the conditions. sec ; S415: Sort θ, d, length in ascending order according to the value of θ sec , according to the width w data of the welding line 3, correct the length sec for gap length , gap length =length sec -w;

[0093] S416:θ,d,length sec The first set of data in corresponds to [θa, da, length seca ], the last set of data corresponds to: [θb, db, length secb ], the total length of the spiral is L, and the spiral includes the first arc: Final Arc and each set of middle arcs except the first arc and the last arc; and

[0094] S417: Output the first arc (gap lengtha , w), the middle arc of each group (gap length , w) and the terminal arc gapl eng thb.

[0095] It can be understood that when the welding line 3 is a straight line, the parameter equation of the welding line 3 corresponds to the equation of the welding trajectory: θ = θ 0 , r∈d1,d1+d2, the resulting intersection is the set {θ 0 ,r 0 ,θ 1 +2π,r 1 ,…,θ 1 +2nπ,r n}, n is an integer.

[0096] In addition, the welding wire 3 can also be a curve. A common curved welding wire 3 is an S-shaped welding wire. The S-shaped welding wire 3 can be a sinusoidal type or a piecewise symmetrical type. Taking the sinusoidal S-shaped welding wire 3 as an example, first define the spiral equation r(θ)=a+bθ. The equation of the S-shaped welding wire 3 in polar coordinates is: r s=d1+d2sin(θ), wherein d1 is the distance between the end point of the S-shaped curve close to the pole and the pole, and d2 is the width of the extension range of the S-shaped curve in the polar radius direction. The simultaneous equations a+bθ=d1+d2sin(θ) are organized into a nonlinear equation: f(θ)=a+bθ-d1-d2sin(θ)=0. The numerical solution is obtained by further using heuristic algorithms such as genetic algorithm, particle swarm algorithm, differential evolution algorithm and ant colony algorithm, or numerical optimization algorithms such as least squares method, bisection method, gradient descent method, Newton method and conjugate gradient method. After the numerical solution is obtained, refer to the above method to correct the intersection to welding point 30, and output the corresponding output first arc (gap lengtha , w), the middle arc of each group (gap length , w) and the end arc gap lengthb .

[0097] It should be further explained that the width w of the welding line 3 is determined by the welding procedure. Generally, without considering the operation error and the system error, the width of the welding line 3 is consistent during the continuous welding operation. Therefore, the width of the same welding line 3 should be equal at all places; however, the widths of different welding lines 3 may be different. Therefore, in the above steps, the width information of each welding line 3 may be supplemented, and the first arc (gap) may be corrected with a relative width value according to the information of the welding line 3 where the welding point 30 is located. lengtha , w a ), each group of mid-arc (gap length , w i ) and the end arc gap lengthb This has certain practicality in actual production design. Taking the straight welding line 3 as an example, the closer to the outer periphery of the spiral, the longer the arc segment 32 between each two welding points 30 is. Therefore, the arc segment length of the arc segment 32 between the welding points 30 can be adjusted by increasing the width of the welding line 3 at the outer periphery, or adding welding lines 3 at the outer periphery (see Figure 5 and Figure 6 ) is used to adjust the arc length of the arc segment 32 between the weld points 30. On the other hand, the intersection is directly corrected to the weld point 30 by using the width value w of the weld line 3, considering that the width w of the weld line 3 is much smaller than the spiral length L. Therefore, in order to reduce the amount of calculation, the arc of the foil covered by the weld point 30 is ignored, and the length of the foil covered by the weld point 30 is approximately equal to the width of the weld line 3. In scenarios with higher precision requirements, the width of the weld point 30 can be further corrected to the arc length of the foil, so as to obtain more accurate size data of the weld point 30, for example, the polar angles corresponding to the endpoints of the width W of the weld point 30 are determined, and the arc length integral formula is used to solve the arc length between the two polar angle values.

[0098] In the specific implementation process, part or all of the welding lines 3 have the characteristics of rotational symmetry about the poles. After confirming the intersection information of a welding line 3, the intersection information of the welding line 3 that has a symmetrical relationship with it can be quickly solved by using a symmetric mapping method, thereby reducing the amount of calculation to a certain extent and reducing the computing power requirements of the computer.

[0099] In some optional implementations, the (gap length , w) The solution method of the list can be converted into a computer programming language and applied to a computer terminal, wherein the computer programming language includes at least one of Java, C, C++ and MathLab. The computer can be equipped with a programming language to implement the above-mentioned solution process in a programming language to achieve more efficient calculation.

[0100] In some optional implementation methods, performing simulation experiments in the finite element software to calculate the resistance of the foil further includes the following steps:

[0101] S431: input the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each of the welding points 30; S432: define the conductivity σ according to the material properties of the foil actually used, define the potential Vlb of the grounded end surface to be equal to 0, and preset the normal component of the current to be zero;

[0102] S433: inputting a specified current I into the geometric entity foil material with the welding point 30 as the current input end, each welding point 30 corresponding to a node of the current input end surface;

[0103] S434: Extract the potential value V of each node of the current input end surface i , calculate the area weight Dai of each node, and take the weighted average potential value of all nodes to get V up ;as well as

[0104] S435: The resistance R of the geometric entity foil is: R = (V up -V lb ) / I.

[0105] In some optional implementation methods, the finite element software includes at least one of croe, solidwork, comsol, ansys and ABAQUS. The above software all have corresponding computer-aided design, finite element calculation and simulation experiment functions.

[0106] A second aspect of the present application provides a design method for a wound battery, the design method for a wound battery comprising the following steps:

[0107] S01: Determine the three-dimensional size information of the separator 23, the negative electrode sheet 25, the positive electrode sheet 21 and the winding needle and the winding method of the winding core 2;

[0108] S02: Designing welding wire 3 schemes for the positive electrode foil 212 and the negative electrode foil 252 to the corresponding positive electrode current collecting disc and the negative electrode current collecting disc respectively;

[0109] S03: Calculate the resistance of the positive electrode foil 212 or the negative electrode foil 252 respectively according to any of the foil resistance calculation methods described above;

[0110] S04: adjusting the three-dimensional size information of the separator 23, the negative electrode sheet 25, the positive electrode sheet 21 and the winding needle, the winding method of the winding core 2 and the welding wire 3 scheme, until a battery design scheme with the smallest resistance value of the positive electrode foil 212 or the negative electrode foil 252 is selected.

[0111] By adopting the above-mentioned foil resistance calculation method, parameter adjustment can be performed from multiple dimensions such as the winding method of the core 2, the three-dimensional size information of the diaphragm 23, the negative electrode sheet 25, the positive electrode sheet 21 and the winding needle, and the design of the welding wire 3. By comparing the resistance of the positive electrode foil 212 or the negative electrode foil 252 in the battery system under various parameters, the battery design optimization direction is determined, the resistance of the positive electrode foil 212 or the negative electrode foil 252 in the battery system is minimized, and the optimal battery design scheme is formed.

[0112] The third aspect of the present application provides a wound battery, which is a wound battery designed according to the above-mentioned design method. The wound battery obtained by the above-mentioned design method can adapt the positive and negative electrode foils to the optimal arrangement design of the welding wire 3, thereby minimizing the resistance value in the battery system, reducing the energy loss when the current passes through, improving the charging and discharging efficiency and stability of the battery, extending the service life and improving the safety performance.

[0113] Furthermore, the wound battery is a lithium-ion cylindrical battery.

[0114] The technical solution of the present application is described below in conjunction with Examples 1-3. In Examples 1-3, a lithium-ion cylindrical battery with a model number of 21700 is used as the target battery, wherein the height of the winding core 2 is 70 mm and the diameter is 21 mm.

[0115] Embodiment 1:

[0116] See also Figure 2-Figure 4 In Example 1, the thickness of the diaphragm 23 is: sep t =12e -3 mm, Needle radius: r a =1.75mm, diaphragm 23 insertion length: Negative electrode material layer 250 thickness: neg t =9.5e -2 mm, negative electrode foil 252 thickness: Negative plate 25 insertion length: Positive electrode material layer 210 thickness: pos t =7.7e -2 mm, positive electrode foil 212 thickness: The winding arc length of the negative electrode sheet 25: l =1493mm, the width of each welding line 3 is w: w = 0.5mm;

[0117] Polar angle list of welding line 3

[0118] The distance between welding wire 3 and the center of the coil is d1 = 3.85 mm, the length of welding wire 3 is d2 = 3.85 mm, the current is I = 4A, and the conductivity of the foil is σ = 5.8e 7 S / m, the calculated resistance of the negative electrode foil 252 is 13.56 μΩ.

[0119] Embodiment 2:

[0120] See also Figure 5 In Example 2, the thickness of the diaphragm 23 is: sep t =12e -3 mm, Needle radius: r a =1.75mm, diaphragm 23 insertion length: Negative electrode material layer 250 thickness: neg t =9.5e -2 mm, negative electrode foil 252 thickness: Negative plate 25 insertion length: Positive electrode material layer 210 thickness: pos t =7.7e -2 mm, positive electrode foil 212 thickness: The winding arc length of the negative electrode sheet 25: l =1493mm, the width of each welding line 3 is w: w = 0.5mm, the distance between welding line 3 and the center of the coil is d1 = [3.85, 5.35, 6.85] mm, and the length of welding line 3 is d2 = [4.5, 3, 1.5] mm;

[0121] Polar angle list of welding line 3:

[0122] Current I = 4A, conductivity σ of negative electrode foil 252 = 5.8e 7 S / m, the calculated resistance of the negative electrode foil 252 is 16.59 μΩ.

[0123] Embodiment 3:

[0124] See also Figure 6 In Example 3, the thickness of the diaphragm 23 is: sep t =12e -3mm, Needle radius: r a =1.75mm, diaphragm 23 insertion length: Negative electrode material layer 250 thickness: neg t =9.5e -2 mm, negative electrode foil thickness 252 Negative electrode insertion length Positive electrode material layer 210 thickness: pos t =7.7e - 2 mm, positive electrode foil 212 thickness: The winding arc length of the positive electrode sheet 21: pos l =1411mm, the width of each welding line 3 is w: w = 0.5mm, the distance between welding line 3 and the pole d1 = [3.55, 6.55, 5.05, 3.55] mm, the length of welding line 3 d2 = [4.5, 1.5, 3, 1.5] mm;

[0125] Polar angle list of welding line 3:

[0126]

[0127] Current: I = 4A, conductivity of positive electrode foil 212: σ = 3.5e 7 S / m, the calculated resistance of the positive electrode foil is 19.49μΩ.

[0128] It can be seen from the resistance data calculated in Examples 1-2 that the resistance difference of foils of the same material and size under different welding wire designs is as high as 18%, which also confirms that the interfacial contact resistance of the positive and negative electrode foils is one of the key variables of the battery internal resistance. The traditional method of testing the resistance of foils requires resistance calibration through physical battery experiments, which has the disadvantages of long testing cycles and high equipment costs. The foil resistance calculation method provided in this application can quickly calculate the resistance of the positive electrode foil or the negative electrode foil in the battery system under a certain welding wire design without conducting a physical battery experiment, providing a theoretical tool for the forward design of the battery internal resistance, and is particularly suitable for the development of a new generation of batteries that are sensitive to interfaces, such as high-nickel ternary / silicon-carbon systems, and has significant technical foresight.

[0129] In the description of this specification, reference to the terms "some embodiments", "an example", or similar descriptions means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment are included in at least one embodiment or example. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0130] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A method for calculating the resistance of a foil, characterized in that: The following steps are involved: S1: according to the winding mode of the winding core, determining the mathematical spiral mode, thickness, width in the height direction of the winding core, and corresponding winding arc length of the separator, the positive electrode sheet, and the negative electrode sheet in the orthographic projection view of the end surface of the winding core; S2: establishing a polar coordinate system in the orthographic projection view of the end surface of the winding core, wherein the polar coordinate system takes the geometric center of the winding needle in the orthographic projection view of the end surface of the winding core as the pole, and takes the line connecting the pole and the starting winding point of the diaphragm as the polar axis; S3: fitting the spiral equations of the winding arc length, polar angle and polar diameter of the separator, the positive electrode sheet and the negative electrode sheet in the polar coordinates; as well as S4: According to the shape, size, quantity and orientation of the welding wire, a parametric equation of the welding wire is fitted in the polar coordinate system, the spiral equation and the parametric equation are combined to solve all intersections, each of which corresponds to the geometric center of a welding point, and a geometric entity foil of the positive electrode foil or the negative electrode foil is generated according to the size information of the welding point, and the resistance value of the geometric entity foil is calculated through simulation experiments.

2. The method for calculating the resistance of foil according to claim 1, characterized in that: The mathematical spiral is an Archimedean spiral, and the polar diameter r and the polar angle θ satisfy the relationship: r = a + bθ, where a is the polar diameter of the starting winding point, b is the radius increment per unit polar angle, and the arc length of the spiral between the polar angle θ1 and the polar angle θ2 is arc l satisfy:

3. The method for calculating the resistance of foil according to claim 2, characterized in that: The establishment of the spiral equation of the winding arc length, polar angle and polar diameter also includes the following steps: S31: With the winding needle radius r a is the polar diameter of the starting winding point of the diaphragm, and determines the parameters: the diaphragm thickness sep t With the length of the position Negative electrode insertion length and winding arc length neg l , the thickness of the negative electrode foil Negative electrode material layer thickness t , the winding arc length of the positive electrode is pos l , the thickness of the positive electrode foil And the thickness of the positive electrode material layer pos t ;as well as S32: according to the radius increment sep of the unit polar angle when the diaphragm is in place and unwound b , the radius increment per unit polar angle when the negative electrode sheet is in place is neg b And the radius increment pos of the unit polar angle when the positive electrode sheet is wound b , respectively calculate the polar angle and polar diameter of the insertion end point of the diaphragm and the negative electrode sheet, and the polar angle and polar diameter of the winding end point of the positive electrode sheet, and establish the spiral equations of the polar angle, polar diameter and arc length of the negative electrode sheet and the positive electrode sheet respectively.

4. The method for calculating the resistance of foil according to claim 3, characterized in that: The S32 further comprises the following steps: S321: the sep b By formula It is found that the relationship between the polar diameter and the polar angle during the diaphragm insertion stage is: sep =r a +sep b θ sep , the diaphragm insertion length is Establishing Relationship I: Where θ0 = 0, solve for the polar angle of the diaphragm entry end point further, Solve for the polar diameter of the diaphragm entry end point S322: The neg b By formula It is found that the relationship between the pole diameter and the pole angle during the negative electrode sheet insertion stage corresponds to: The end point of the diaphragm is the starting point of the negative electrode sheet. Establish relationship II: Solve the polar angle of the negative electrode sheet entry end point further, Solve the pole diameter of the negative electrode sheet at the end point of insertion S323: the pos b By formula The end point of the negative electrode sheet is the starting point of the positive electrode sheet winding. According to the winding arc length pos of the positive electrode sheet l , establish relation III: Solve the polar angle of the winding end point of the positive electrode sheet Further according to the formula Solve the pole diameter r of the winding end point of the positive electrode sheet b ;as well as S324: The arc length of the spiral between any two polar angles θ1 and θ2 of the positive electrode sheet satisfies: The arc length of the spiral between any two polar angles θ1 and θ2 of the negative electrode sheet during the in-position stage satisfies: The arc length of the spiral between any two polar angles θ1 and θ2 of the negative electrode sheet during the co-winding stage with the positive electrode sheet after the placement stage satisfies: Said For the diaphragm The polar diameter at the polar angle, 5. The method for calculating the resistance of foil according to claim 4, characterized in that: The solution method of the relationship I-III includes at least one of a heuristic algorithm and a numerical optimization algorithm. The heuristic algorithm includes a genetic algorithm, a particle swarm algorithm, a differential evolution algorithm and an ant colony algorithm. The numerical optimization algorithm includes a least squares method, a bisection method, a gradient descent method, a Newton method and a conjugate gradient method.

6. The method for calculating the resistance of foil according to claim 1, characterized in that: The S4 further comprises the following steps: S41: The line connecting the geometric symmetry center of each welding line and the pole forms a welding line polar angle, and a list of welding line polar angles θ of all welding lines is listed. list , and corresponds to the welding line polar angle list θ list Match the parameter equation of the corresponding welding wire, solve the parameter equation of the welding wire and the spiral equation of the positive electrode sheet or the negative electrode sheet simultaneously, and use the range of each welding wire on the polar diameter as a constraint condition to obtain n intersection points of all the welding wires and the negative electrode sheet or the positive electrode sheet, and divide the spiral corresponding to the negative electrode sheet or the positive electrode sheet into n+1 arc segments corresponding to the intersection points, solve the arc segment length of each arc segment, and, according to the welding wire width w data, correct the intersection point to the welding point, and correct the foil length gap corresponding to the arc segment length length , the list gets (gap length , w); S42: Based on the foil length between each two adjacent welding points and the welding point width list (gap length , w), combining the thickness of the corresponding positive electrode foil or the negative electrode foil, the winding arc length parameter of the positive electrode sheet or the negative electrode sheet, and the width parameter of the positive electrode sheet or the negative electrode sheet in the height direction of the winding core, generating a geometric entity corresponding to the foil in the finite element software; and S43: Conduct a simulation experiment in the finite element software, input the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each of the welding points, use the welding points as current input terminals to input a specified current I into the geometric entity foil, and calculate the average potential Vup of the current input terminal surface and the potential Vlb of the ground terminal surface by the finite element method based on the conductivity coefficient σ of the foil, and output the resistance value of the geometric entity foil.

7. The method for calculating the resistance of foil according to claim 6, characterized in that: The parametric equation of the welding line is used to describe the welding trajectory of the welding line in the polar coordinate system. The welding trajectory is a straight line or curve of a finite length. The distance between the endpoint of the welding trajectory close to the pole and the pole is d1, and the width of the welding trajectory in the polar radius direction of the polar coordinate system is d2.

8. The method for calculating the resistance of foil according to claim 7, characterized in that: The welding trajectory is a straight line extending through the pole, and the width of each welding line is w. The combination of pole angles corresponding to each welding trajectory is the welding line pole angle list θ. list , the gap length , w) The solution method of the list includes the following steps: S411: Determine the spiral equation r(θ)=a+bθ of the positive electrode sheet or the negative electrode sheet where the welding point is located, determine the parameters a, b and the effective polar diameter range [r1, r2] of the spiral, and input θ list , input the polar diameter range of each welding track [d1, d1+d2], and the width w of the welding line; S412: Define the arc length integral formula Any two polar angles θ star To the polar angle θ end The arc length calculation formula is: length (a,b,θ star ,θ end )=L(a,b,θ end )-L(a,b,θ star ); S413: Initialize θ to 0, obtain θ list For any polar angle value θ1, constrain r1≤r(θ1)≤r2, calculate the polar radius d=r(θ1). If d∈[d1,d1+d2], calculate the arc length: length sec =L(θ1)-L(0), record [θ1, d, length sec ], set the increment to 2π, update θ=θ1+2π, recalculate r(θ), merge all the [θ, d, length sec ]; S414: Traversing θ list For each polar angle value, record all the welding lines that meet the conditions [θ, d, length sec ]; S415: Sort in ascending order according to the value of θ [θ, d, length sec ], according to the width w data of the welding line, correct the length sec for gap length , gap length =length sec -w; S416: [θ, d, length sec ] corresponds to the first set of data [θa, da, length seca ], the last set of data corresponds to: [θb, db, length secb ], the total length of the spiral is L, and the spiral includes the first arc: Final Arc and each set of middle arcs except the first arc and the last arc; and S417: Output the first arc (gap lengtha , w), the middle arc of each group (gap length , w) and the end arc gap lengthb .

9. The method for calculating the resistance of foil according to claim 8, characterized in that: The gap length , w) The solution method of the list can be converted into a computer programming language and applied to a computer terminal, wherein the computer programming language includes at least one of java, C, C++ and mathlab.

10. The method for calculating the resistance of foil according to claim 6, characterized in that: The S43 further comprises the following steps: S431: inputting the three-dimensional geometric parameters of the geometric entity foil and the geometric parameters of each welding point; S432: According to the material properties of the foil material actually used, the conductivity σ is defined, the potential Vlb of the grounded end surface is defined to be equal to 0, and the normal component of the current is preset to be zero; S433: inputting a specified current I into the geometric entity foil material with the welding point as the current input end, each welding point corresponding to a node of the current input end surface; S434: Extract the potential value V of each node of the current input end surface i , calculate the area weight Dai of each node, and take the weighted average potential value of all nodes to get V up ;as well as S435: The resistance R of the geometric entity foil is: R = (V up -V lb ) / I.

11. The method for calculating the resistance of foil according to claim 1, characterized in that: The finite element software includes at least one of croe, solidwork, comsol, ansys and ABAQUS.

12. A method for designing a wound battery, characterized in that: The design method of the wound battery comprises the following steps: S01: Determine the three-dimensional size information of the separator, the negative electrode sheet, the positive electrode sheet and the winding needle, and the winding method of the winding core; S02: Design the welding wire schemes between the positive electrode foil and the negative electrode foil and the corresponding positive electrode collector and negative electrode collector respectively; S03: Calculating the resistance of the positive electrode foil or the negative electrode foil respectively according to the foil resistance calculation method according to any one of claims 1 to 11; S04: adjusting the three-dimensional size information of the separator, the negative electrode sheet, the positive electrode sheet and the winding needle, the winding method of the winding core and the welding wire scheme, until a battery design scheme with the smallest resistance value of the positive electrode foil or the negative electrode foil is screened out.

13. A wound battery, characterized in that: The wound battery is a wound battery designed according to the design method according to claim 12.

14. The wound battery according to claim 13, characterized in that: The wound battery is a lithium-ion cylindrical battery.

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