Battery cell manufacturing method

Abstract

To improve power generation performance. [Solution] The manufacturing method of the battery cell 1 includes a drying step in which a flat battery cell 1 having a flexible outer casing member 20 is restrained by being sandwiched from both sides in the thickness direction and then heated and dried. The restraining jig 40 that creates the restrained state has a pair of restraining planes 41A, 42A for sandwiching the battery cell 1. The maximum allowable dimension P is the maximum value of the allowable dimensional range between the restraining planes 41A, 42A. max This is the minimum allowable dimension C, which is the minimum value within the allowable dimensional range for the thickness of battery cell 1. min The following applies:

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing battery cells. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a non-aqueous electrolyte secondary battery. In this method, an electrolyte is poured into an outer casing containing a wound electrode body to obtain a battery assembly, and then a load is applied to the battery assembly using a press machine so that a restraining pressure of 0.5 MPa is applied to the battery assembly, thereby charging the battery assembly. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-160470 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the method described in Patent Document 1 has the problem that the wound electrode body is not restrained during drying before the electrolyte is injected, resulting in large variations in the thickness of the battery cell.

[0005] This disclosure has been completed based on the circumstances described above and aims to reduce variations in the thickness of battery cells. [Means for solving the problem]

[0006] A method for manufacturing a battery cell, The process includes a drying step in which a flat battery cell having a flexible outer casing is sandwiched from both sides in the thickness direction to restrain it and then heated and dried. The restraining jig that creates the aforementioned restrained state has a pair of restraining planes for clamping the battery cell, A method for manufacturing a battery cell, wherein a maximum allowable dimension that is the maximum value of an allowable dimensional range between the restraining flat surfaces is equal to or less than a minimum allowable dimension that is the minimum value of an allowable dimensional range of the thickness of the battery cell. Effects of the Invention

[0007] According to the present disclosure, variation in the thickness of battery cells can be reduced. Brief Description of the Drawings

[0008] [Figure 1] It is a perspective view of a secondary battery according to an embodiment. [Figure 2] It is an exploded perspective view of an electrode laminate. [Figure 3] It is a view schematically illustrating a state before a restrained state is established in a drying step. [Figure 4] It is a view schematically illustrating the restrained state in the drying step. [Figure 5] It is a partially enlarged cross-sectional view illustrating a module structure including a battery cell. Modes for Carrying Out the Invention

[0009] Here, preferred exemplary embodiments of the present disclosure are presented. Any combination of a plurality of the following exemplary embodiments within a range not causing contradiction is also included in the modes for carrying out the invention.

[0010] [1] A method for manufacturing a battery cell, comprising a drying step of sandwiching a flat battery cell having a flexible exterior member from both sides in the thickness direction to place the battery cell in a restrained state, and heating and drying the battery cell. A restraining jig for placing the battery cell in the restrained state has a pair of restraining flat surfaces for sandwiching the battery cell. The maximum allowable dimension that is the maximum value of the allowable dimensional range between the restraining flat surfaces is equal to or less than the minimum allowable dimension that is the minimum value of the allowable dimensional range of the thickness of the battery cell. [2] The battery cell includes an electrode laminate in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween. The method for manufacturing a battery cell according to [1], wherein the heating temperature in the drying step is above the glass transition temperature of the constituent resin constituting the separator. [3] The method for manufacturing a battery cell according to [1] or [2], wherein the electrode binder used in at least one of the positive electrode plate and the negative electrode plate is polyvinylidene fluoride, and the heating temperature is 150°C or less. [4] The method for manufacturing a battery cell according to any one of [1] to [3], wherein the minimum allowable dimension, which is the minimum value of the allowable dimensional range between the constraint planes, is 80% or more of the reference dimension of the thickness of the battery cell.

[0011] An embodiment of this disclosure will be described with reference to Figures 1 to 5. In this embodiment, the front-to-back direction is defined as the F direction in each figure. The left-to-right direction is defined as the R direction in each figure. The left-to-right direction and the width direction are used synonymously. The up-to-down direction is defined as the H direction in each figure. Note that in Figure 2, the thickness of each component is omitted. Each figure is a schematic diagram, and the dimensions of each component may not be accurate.

[0012] 1. Manufacturing method of battery cell 1 The manufacturing method for the battery cell 1 includes a drying step in which a flat battery cell 1 having a flexible outer casing member 20 is restrained by being sandwiched from both sides in the thickness direction and then heated and dried. The restraining jig 40 that creates the restraining state has a pair of restraining planes 41A and 42A for sandwiching the battery cell 1. The maximum allowable dimension P is the maximum value of the allowable dimensional range between the restraining planes 41A and 42A. max This is the minimum allowable dimension C, which is the minimum value within the allowable dimensional range for the thickness of battery cell 1. min The following applies:

[0013] (1) Battery cell 1 As shown in Figure 1, the battery cell 1 has a flattened shape in which the overall height dimension (thickness) is small compared to the depth dimension (length in the front-to-back direction) and width dimension (dimension in the left-to-right direction). The battery cell 1 comprises an electrode stack 10, a pair of terminals 16, and an outer casing member 20.

[0014] As shown in Figure 2, the electrode stack 10 is constructed by alternately stacking multiple negative electrode plates 11 and multiple positive electrode plates 13 with separators 15 in between. The electrode stack 10 in Figure 2 is constructed with multiple sheet-like separators 15. The configuration of the electrode stack is not limited to this. For example, the electrode stack may be constructed by folding a single sheet-like separator in a zigzag pattern, alternating between mountain folds and valley folds. Furthermore, the electrode stack may be a flat, wound electrode body as long as it has a structure in which the negative electrode plates, positive electrode plates, and separators are stacked in a height dimension.

[0015] The separator 15 separates the negative electrode plate 11 and the positive electrode plate 13, preventing short circuits caused by contact between the two electrodes while allowing ions to pass through. The separator 15 is preferably made of a nonwoven fabric mainly composed of fibers with a melting point of 150°C or higher. The nonwoven fabric of the separator 15 may be mainly composed of one or more fibers selected from the group consisting of polyacrylonitrile, polytetrafluoroethylene, cellulose, polyethylene terephthalate, and meta-aramid.

[0016] The negative electrode plate 11 has a negative electrode active material layer (not shown) formed on one or both sides of a rectangular sheet-shaped negative electrode current collector (not shown). The negative electrode current collector is preferably a metal foil such as copper foil. The thickness of the negative electrode current collector is not particularly limited, but is, for example, 5 μm to 20 μm.

[0017] The negative electrode active material layer is constructed by, for example, applying a negative electrode slurry (not shown). The negative electrode slurry is a mixture of negative electrode active material, negative electrode binder, conductive material, dispersion thickener, etc. The negative electrode active material is, for example, a carbon material selected from the group consisting of graphite, hard carbon, and soft carbon. The negative electrode binder is, for example, one or more selected from the group consisting of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA). There are no particular restrictions on the thickness of one side of the negative electrode active material layer, but it is usually between 10 μm and 200 μm.

[0018] The positive electrode plate 13 has a positive electrode active material layer (not shown) formed on one or both sides of a rectangular sheet-shaped positive electrode current collector (not shown). The positive electrode current collector is preferably a metal foil such as aluminum foil. The thickness of the positive electrode current collector is not particularly limited, but is, for example, 5 μm to 20 μm.

[0019] The positive electrode active material layer is constructed by, for example, applying a positive electrode slurry (not shown). The positive electrode slurry is a mixture of positive electrode active material, electrode binder, conductive material, dispersion thickener, etc. The positive electrode active material is, for example, lithium transition metal oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 Examples include lithium transition metal phosphate compounds (e.g., O4) and lithium transition metal phosphate compounds (e.g., LiFePO4). The positive electrode binder is one or more selected from the group consisting of polyvinylidene fluoride, styrene-butadiene rubber, polytetrafluoroethylene, and polyacrylic acid. There are no particular restrictions on the thickness of one side of the positive electrode active material layer, but it is usually between 10 μm and 200 μm.

[0020] A rectangular, flat terminal 16 made of metal plate material is fixed to the negative electrode side connection portion 12 (uncoated portion), which is a protruding part of the negative electrode current collector to which the negative electrode slurry is not applied, and to the positive electrode side connection portion 14 (uncoated portion), which is a protruding part of the positive electrode current collector to which the positive electrode slurry is not applied. The terminal 16 protrudes forward from the negative electrode side connection portion 12 and the positive electrode side connection portion 14.

[0021] The outer casing member 20 is a member that liquid-tightly encloses the base end of the terminal 16 and the entire electrode laminate 10. An electrolyte (not shown) is contained inside the outer casing member 20. The outer casing member 20 consists of a pair of laminate sheets 21 and 22. The laminate sheets 21 and 22 are composed of a sheet-like substrate and a sealing material attached to the inner surface of the sheet-like substrate. There are no particular restrictions on the thickness of each of the laminate sheets 21 and 22, but they are usually between 100 μm and 200 μm.

[0022] (2) Preferred example of a method for manufacturing the battery cell 1 An example of a method for manufacturing a battery cell 1 includes the steps of preparing an electrode stack 10, wrapping the electrode stack 10 with an outer casing member 20, drying, liquid injection, and activation.

[0023] The process of preparing the electrode laminate 10 involves stacking multiple negative electrode plates 11 and multiple positive electrode plates 13 alternately with a separator 15 in between, as shown in Figure 2. Terminals 16 are then welded to the negative electrode side connection portion 12 (uncoated portion) and the positive electrode side connection portion 14 (uncoated portion), respectively, while the laminate is bundled in the stacking direction.

[0024] The process of wrapping the electrode stack 10 with the outer casing member 20 involves placing the electrode stack 10 between a pair of laminate sheets 21 and 22, and heat-welding the edges of the laminate sheets 21 and 22 on three sides: in the width direction and the front direction (the direction in which the terminals 16 protrude). Once the edges on the three sides are heat-welded, the electrode stack 10 is housed in the bag-shaped outer casing member 20. After the process of wrapping the electrode stack 10 with the outer casing member 20, a flat battery cell 1 having a flexible outer casing member 20 is obtained. This battery cell 1 is in its state before the electrolyte is injected.

[0025] In the process of enclosing the electrode laminate 10 with the outer casing member 20, the rear edge of the outer casing member 20 is not heat-sealed (see Figures 3 and 4). The unheat-sealed portion forms an opening that allows solvents and other substances inside the outer casing member 20 to escape to the outside during the subsequent drying process.

[0026] The drying process involves clamping the obtained battery cell 1 from both sides in the thickness direction to restrain it and then heating and drying it. In the drying process, for example, with a part of the exterior member 20 open, the battery cell 1 is restrained with a restraining jig 40 and held at a predetermined temperature for a predetermined time. The operation of holding at a predetermined temperature for a predetermined time can be carried out, for example, using a constant temperature bath. The drying process may also involve reduced-pressure drying or vacuum drying in combination with heating. The requirements for restraining with the restraining jig 40 will be explained later.

[0027] The heating temperature in the drying process is not particularly limited. The heating temperature in the drying process is usually 80°C or higher, but may be 90°C or higher, or even 100°C or higher. The upper limit of the heating temperature can be set appropriately within a range that does not degrade the components constituting the battery cell 1. Depending on the components constituting the battery cell 1, the upper limit of the heating temperature can be set, for example, to 150°C or lower.

[0028] From the viewpoint of improving the creep resistance of the separator 15, the heating temperature in the drying process is preferably above the glass transition temperature of the constituent resin that makes up the separator 15, and more preferably above the glass transition temperature + 6°C. For example, the glass transition temperature of polyacrylonitrile is 104°C. When the constituent resin that makes up the separator 15 is polyacrylonitrile, the heating temperature in the drying process is preferably 104°C or higher, and more preferably 110°C or higher.

[0029] When the electrode binder used in at least one of the positive electrode plate 13 and the negative electrode plate 11 is polyvinylidene fluoride, the heating temperature is preferably 150°C or lower from the viewpoint of ensuring battery performance. Polyvinylidene fluoride is preferably used in at least the positive electrode plate 13, may be used only in the positive electrode plate 13, or may be used in both the positive electrode plate 13 and the negative electrode plate 11. Polyvinylidene fluoride may be a polyvinylidene fluoride homopolymer or a polyvinylidene fluoride copolymer. In this specification, polyvinylidene fluoride copolymer means a copolymer containing 50% by mass or more and 99% by mass or more of vinylidene fluoride monomer units (monomer units derived from vinylidene fluoride) based on the mass of the polyvinylidene fluoride copolymer.

[0030] The heating time in the drying process is not particularly limited. For example, the heating time in the drying process may be between 1 hour and 24 hours. In the drying process, after heating for a predetermined time, it is preferable to cool the heated battery cell 1 while maintaining its restrained state.

[0031] In the liquid injection step, after going through the drying step, an electrolytic solution is injected into the battery cell 1 from which the restraining jig 40 has been removed. The electrolytic solution may be injected, for example, from the opening of the exterior member 20. In the liquid injection step, after injecting the electrolytic solution, the opening of the exterior member 20 is sealed. In the activation step, an aging treatment is performed on the battery cell 1.

[0032] (3) Restraining Jig 40 As shown in FIGS. 3 and 4, the restraining jig 40 has a pair of restraining flat surfaces 41A, 42A for sandwiching the battery cell 1. The restraining jig 40 of the present embodiment includes a first member 41, a second member 42, a spacer 44, and a fastening member 45. The first member 41 has one restraining flat surface 41A. The second member 42 has the other restraining flat surface 42A, and is disposed to face the first member 41. The spacer 44 is located between the first member 41 and the second member 42, and defines the dimension between the restraining flat surfaces 41A, 42A. The fastening member 45 reduces the dimension between the first member 41 and the second member 42 by fastening. The fastening member 45 of the present embodiment is configured to be screwed into a screw hole provided in the spacer 44.

[0033] (4) Requirements for Restraint by Restraining Jig 40 (4.1) Explanation of Terms Hereinafter, the technique of the present disclosure will be described using the terms "reference dimension", "upper dimensional tolerance", and "lower dimensional tolerance". The reference dimension is a dimension that serves as a reference for machining. The difference between the upper dimensional tolerance and the lower dimensional tolerance is referred to as a dimensional tolerance. The upper dimensional tolerance means the difference between the reference dimension and the maximum allowable dimension, and the lower dimensional tolerance means the difference between the reference dimension and the minimum allowable dimension. The absolute value of the upper dimensional tolerance and the absolute value of the lower dimensional tolerance may be the same value, or may be different values.

[0034] Let the reference dimension of the thickness of the battery cell 1 be C, and let the minimum allowable dimension, which is the minimum value of the allowable dimensional range for the thickness of the battery cell 1, be C min and let the maximum allowable dimension, which is the maximum value of the allowable dimensional range for the thickness of the battery cell 1, be C max Lower dimensional tolerance = Minimum allowable dimension C​min - Reference dimension C of the thickness of battery cell 1 The upper dimension tolerance = maximum allowable dimension C max - Reference dimension C of the thickness of battery cell 1

[0035] The lower and upper dimensional tolerances of the battery cell 1 are within the range of practically permissible errors of the battery cell 1 and are not particularly limited. The lower dimensional tolerance is preferably 10% or less of the reference dimension C of the thickness of the battery cell 1, more preferably 5% or less. The upper dimensional tolerance is preferably 10% or less of the reference dimension C of the thickness of the battery cell 1, more preferably 5% or less.

[0036] For example, if the standard dimension C of the thickness of battery cell 1 is 10.0 mm, the lower dimensional tolerance is 0.5 mm, and the upper dimensional tolerance is 0.5 mm, then the allowable dimensional range for the thickness of battery cell 1 is C min 9.5mm or moreC max The size is 10.5 mm or less (10.0 ± 0.5 mm).

[0037] Furthermore, let P be the reference dimension between the constrained planes 41A and 42A, and let P be the minimum allowable dimension, which is the minimum value of the allowable dimensional range between the constrained planes 41A and 42A. min The maximum allowable dimension, which is the maximum value of the allowable dimensional range between the constrained planes 41A and 42A, is set to P. max Let's assume that. The dimensional tolerance below = minimum allowable dimension P min - Reference dimension P between constrained planes 41A and 42A The dimensional tolerance above = maximum allowable dimension P max - Reference dimension P between constrained planes 41A and 42A

[0038] For example, if the reference dimension P between constrained planes 41A and 42A is 9.4 mm, the lower dimensional tolerance is 0.1 mm, and the upper dimensional tolerance is 0.1 mm, then the allowable dimensional range between constrained planes 41A and 42A is P min 9.3mm or more P max The size is 9.5 mm or less (9.4 ± 0.1 mm).

[0039] (4.2) Maximum allowable dimension Pmax Requirements related to The maximum allowable dimension P is the maximum value of the allowable dimensional range between the constraint planes 41A and 42A. max This is the minimum allowable dimension C, which is the minimum value within the allowable dimensional range for the thickness of battery cell 1. min The following applies: Maximum allowable dimension P max ≤ Minimum allowable dimension C min

[0040] Maximum allowable dimension P max The minimum allowable dimension C min It may be the same as the minimum allowable dimension C min It may be smaller than that. In the specific example above, the maximum allowable dimension P max The minimum allowable dimension C is 9.5 mm. min Since it is 9.5 mm, the maximum allowable dimension P max ≤ Minimum allowable dimension C min The conditions are met.

[0041] (4.3) Minimum allowable dimension P min Requirements related to The minimum allowable dimension P is the minimum value of the allowable dimensional range between the constrained planes 41A and 42A. min Preferably, this is 80% or more of the reference dimension C of the thickness of the battery cell 1. The standard thickness of battery cell 1 is C × 0.8 ≤ minimum allowable dimension P. min

[0042] Minimum allowable dimension P min The minimum allowable dimension P may be the same as the standard thickness dimension C × 0.8 of the battery cell 1, or it may be larger than the standard thickness dimension C × 0.8 of the battery cell 1. In the specific example above, the standard thickness dimension C × 0.8 of the battery cell 1 is 8.0 mm, and the minimum allowable dimension P is 8.0 mm. min Since it is 9.3 mm, the standard dimension C × 0.8 ≤ minimum allowable dimension P of the battery cell 1 thickness min The conditions are met.

[0043] 2. Effects of this embodiment The manufacturing method of the battery cell 1 in this embodiment has a drying step as described above, which reduces variations in the thickness of the battery cell 1. Unlike this embodiment, if the drying step is performed without the battery cell 1 being constrained, variations in the thickness of the battery cell 1 may increase due to reasons such as the thickness of the separator 15 becoming excessively large compared to the reference dimension C, or the individual components constituting the battery cell 1 not being in sufficient contact. On the other hand, the battery cell 1 in this embodiment has a maximum allowable dimension P which is the maximum value of the allowable dimensional range between the constrained planes 41A and 42A. max The minimum allowable dimension C is the minimum value within the allowable dimensional range for the thickness of battery cell 1. min By performing the drying process according to the following requirements, it is possible to suppress the thickness of the separator 15 from becoming excessively larger than the standard dimension C, and to ensure that each component constituting the battery cell 1 is in sufficient contact.

[0044] Figure 5 shows an example of a modular structure equipped with battery cells 1. This modular structure comprises multiple battery cells 1 arranged at intervals and multiple cooling plates 50 arranged to stack without gaps between adjacent battery cells 1. If there is a large variation in the thickness of the battery cells 1, the maximum allowable dimension C will be affected when modularizing to a standard size. max The pressure required to pressurize nearby battery cells 1 increases. Therefore, the module structure itself needs to be designed to withstand large pressures, which increases both the volume and mass of the module structure, raising concerns about a decrease in the energy density of the module structure. On the other hand, since the battery cells 1 of this embodiment have little variation in thickness, they can contribute to miniaturization of the module structure and ensure sufficient energy density of the module structure.

[0045] Furthermore, in this embodiment, if the heating temperature in the drying process is above the glass transition temperature of the constituent resin constituting the separator 15, the creep resistance of the separator 15 can be improved. Generally, it is known that battery cells expand during charging and contract during discharge (see the white arrow in Figure 5). If the creep resistance of the separator 15 can be improved, for example, the reaction force of the battery cell 1 can be suitably secured even in a module structure that has undergone repeated charging and discharging. If the reaction force of the battery cell is lost and the battery cell cannot be properly pressurized, gas generated inside the battery cell during use will remain between the positive and negative electrodes, and there is a concern that the reaction area will decrease due to the gas, causing the resistance to increase. On the other hand, in this embodiment, the reaction force of the battery cell 1 can release the gas remaining between the negative electrode plate 11 and the positive electrode plate 13 to the side, thereby suppressing the increase in resistance caused by the gas.

[0046] The reason why the creep resistance of the separator 15 can be improved when the heating temperature in the drying process is above the glass transition temperature of the constituent resin of the separator 15 is not clear, but it is presumed that the degree of crystallinity of the constituent resin increases, making it less likely for the separator 15 to deform from the shape it was held in a constrained state during the drying process. This disclosure is not to be interpreted as being limited to this presumed reason.

[0047] Furthermore, in this embodiment, if the electrode binder used in at least one of the positive electrode plate 13 and the negative electrode plate 11 is polyvinylidene fluoride, and the heating temperature is 150°C or lower, the battery performance can be suitably ensured. At temperatures higher than 150°C, there is a concern that hydrofluoric acid may be released from polyvinylidene fluoride. If the heating temperature is 150°C or lower, the deterioration of battery performance due to hydrofluoric acid release can be suppressed.

[0048] The following experiments were conducted to investigate the relationship between drying temperature and separator displacement, and the relationship between drying temperature and IV resistance.

[0049] First, a separator made of polyacrylonitrile (glass transition temperature 104°C) was prepared. An electrode laminate with a total thickness of 10 mm was fabricated, and a battery cell was manufactured by performing a drying process at the drying temperatures listed in Table 1. Polyvinylidene fluoride was used as the electrode binder for the positive electrode plate of the electrode laminate.

[0050] To simulate the pressurized state in the module structure, battery cells were compressed at 0.3 MPa for 6 hours using an autograph. The thickness of the battery cells was measured before and after compression, and the thickness displacement was calculated. The results are shown in Table 1. It can be seen that the smaller the thickness displacement, the better the creep resistance of the separator.

[0051] Furthermore, the IV resistance (mΩ) of the fabricated battery cells was measured. The results are shown in Table 1. It can be seen that the smaller the IV resistance, the better the battery performance is guaranteed.

[0052] [Table 1]

[0053] Samples 1 and 2 are samples whose drying temperature is lower than the glass transition temperature of the polyacrylonitrile constituting the separator 15. Samples 3-5 are samples whose drying temperature is higher than the glass transition temperature of the polyacrylonitrile constituting the separator 15. Samples 3-5 showed less thickness displacement than samples 1 and 2, and exhibited superior creep resistance of the separator.

[0054] Samples 1-4 are samples with a drying temperature of 150°C or less. Sample 5 is a sample with a drying temperature greater than 150°C. Samples 1-4 had lower IV resistance than Sample 5, ensuring battery performance.

[0055] The examples described herein are for illustrative purposes only and should not be construed as limiting the invention. Although the invention has been described with examples of typical embodiments, the language used in the description and illustrations of the invention should be understood as descriptive and illustrative, not limiting. As detailed herein, modifications are possible within the scope or essence of the invention without departing in any way. While specific structures, materials, and embodiments have been referenced in this detailed description of the invention, the invention is not intended to be limited to the disclosures herein, but rather to encompass all functionally equivalent structures, methods, and uses within the scope of the claims. [Explanation of Symbols]

[0056] 1 ... Battery cell 10 ... Electrode stack 11 ... Negative plate 12 ... Negative electrode connection part 13 ... Positive plate 14 ... Positive side connection 15 ... Separator 16… Terminals 20 ... Exterior components 21, 22… Laminating sheets 40 ... Restraint fixtures 41 ...First member 41A…Constraint plane 42 ...Second component 42A…Constraint plane 44... Spacer 45 ... Fastening member 50 ... Cooling plate

Claims

1. The process includes a drying step in which a flat battery cell having a flexible outer casing is sandwiched from both sides in the thickness direction to restrain it and then heated and dried. The restraining jig that creates the aforementioned restrained state has a pair of restraining planes for clamping the battery cell, A method for manufacturing a battery cell, wherein the maximum allowable dimension, which is the maximum value of the allowable dimensional range between the constraint planes, is less than or equal to the minimum allowable dimension, which is the minimum value of the allowable dimensional range of the thickness of the battery cell.

2. The aforementioned battery cell comprises an electrode laminate in which a positive electrode plate and a negative electrode plate are stacked with a separator in between, The method for manufacturing a battery cell according to claim 1, wherein the heating temperature in the drying step is above the glass transition temperature of the constituent resin constituting the separator.

3. The method for manufacturing a battery cell according to claim 2, wherein the electrode binder used in at least one of the positive electrode plate and the negative electrode plate is polyvinylidene fluoride, and the heating temperature is 150°C or lower.

4. The method for manufacturing a battery cell according to any one of claims 1 to 3, wherein the minimum allowable dimension, which is the minimum value of the allowable dimensional range between the constraint planes, is 80% or more of the reference dimension of the thickness of the battery cell.

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