Spacer manufacturing method, spacer group, and battery pack

Abstract

An object of the present invention is to provide a battery assembly in which excellent heat insulating performance can be stably obtained by means of spacers, a group of spacers used in the battery assembly, and a method for manufacturing the spacers. [Solution] The battery pack includes a plurality of unit cells and a plurality of sheet-like spacers arranged between the unit cells, wherein the tolerance of the creepage distance A of the plurality of spacers is 0.010 to 2.0 mm. (Creepage distance A) A first cell is brought close to the first flat side of the spacer, and a second cell is brought close to the second flat side of the spacer until they come into contact. A point on the edge of the contact portion where the first cell and the spacer are in surface contact is designated as point a1, a point on the edge of the contact portion where the second cell and the spacer are in surface contact is designated as point a2, and the creepage distance between points a1 and a2, which is the shortest distance along the surface of the spacer, is designated as A (mm).

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a spacer, a spacer group, and a battery pack. [Background technology]

[0002] 2. Description of the Related Art As a battery module including a secondary battery mounted on a mobile body such as a vehicle or a ship, a battery pack including a plurality of unit cells and spacers provided between the unit cells is used. For example, Patent Document 1 discloses a battery pack in which a heat-conducting member (spacer) made of a resin material with a high flexural modulus is placed between single battery cells to suppress heat transfer to adjacent single battery cells and efficiently dissipate heat into the heat dissipation space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-108617 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional techniques such as those disclosed in Patent Document 1, it is difficult to obtain a battery pack that can stably achieve excellent heat insulating performance due to the spacers.

[0005] The main object of the present invention is to provide a method for manufacturing spacers that can stably provide spacers with excellent thermal insulation performance, a group of spacers that can stably provide excellent thermal insulation performance, and a battery pack using the group of spacers. [Means for solving the problem]

[0006] The present invention includes the following configurations. [1] A method for manufacturing a spacer having an inner material and an outer material, The method includes an inner packaging material supplying step of supplying an inner packaging material, an outer packaging material supplying step of supplying an outer packaging material, and a sealing step of forming a laminate in which both sides of the inner packaging material are sandwiched between the outer packaging materials, and sealing the outer packaging materials around the inner packaging material to form a sealed body, The method for manufacturing a spacer, wherein the inner casing material supplying step includes causing the inner casing material to absorb a liquid. [2] The manufacturing method according to [1], wherein the inner packaging material supply step includes supplying a strip of inner packaging material and cutting the inner packaging material in a direction perpendicular to the flow direction. [3] The manufacturing method according to [1] or [2], wherein the sealing step includes sealing the outer edges of a pair of exterior materials. [4] The manufacturing method according to any one of [1] to [3], wherein the sealing step includes degassing the air contained between the pair of exterior materials and sealing the outer edges of the pair of exterior materials. [5] The manufacturing method according to any one of [1] to [4], wherein the sealing step includes degassing the air contained between the pair of packaging materials by reducing the pressure in the sealed space in which the laminate is present or by pressing the laminate from the center outward, and sealing the outer edges of the pair of packaging materials. [6] The manufacturing method according to any one of [1] to [5], further comprising a cutting step of cutting the sealed body into rectangles after the sealing step. [7] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, The manufacturing method according to any one of [1] to [6], wherein the dimensional error of the cut rectangle is 5.0 mm or less. [8] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, The manufacturing method according to any one of [1] to [7], wherein the dimensional error of the cut rectangle is 2.0 mm or less. [9] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, The manufacturing method according to any one of [1] to [8], wherein the dimensional error of the cut rectangle is 1.0 mm or less.

[10] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, The manufacturing method according to any one of [1] to [9], wherein the cutting position of the sealed body is adjusted based on a mark printed on the exterior material.

[11] The manufacturing method according to any one of [1] to

[10] , further comprising a cutting step of cutting the sealed body into rectangular shapes after the sealing step, and an inspection step of inspecting the appearance of the surface of the sealed body.

[12] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, and an inspection step of inspecting the appearance of the surface of the sealed body, The manufacturing method according to any one of [1] to

[11] , further comprising determining whether the product is good or bad based on the results of the inspection.

[13] The method further includes a cutting step of cutting the sealed body into a rectangular shape after the sealing step, and an inspection step of inspecting the appearance of the surface of the sealed body, The sealed products that are judged to be non-defective are transported to the exit, The manufacturing method according to any one of [1] to

[12] , which includes discarding sealed products determined to be defective without transporting them to an outlet.

[14] The manufacturing method according to any one of [1] to

[13] , wherein the inner packaging material supply step includes supplying the inner packaging material having a width that is 50 to 90% of the width perpendicular to the flow direction of the outer packaging material.

[15] The manufacturing method described in any one of [1] to

[14] , wherein the inner packaging material supply step includes causing the inner packaging material to absorb water so that the water absorption rate of the inner packaging material is 5% or more of the saturated water absorption amount of the inner packaging material.

[16] The manufacturing method according to any one of [1] to

[15] , wherein in the inner packaging material supplying step, the liquid to be absorbed into the inner packaging material is supplied from a nozzle.

[17] The manufacturing method according to any one of [1] to

[16] , wherein the inner packaging material supply step includes supplying the inner packaging material with one end of the inner packaging material in a fixed position in a width direction perpendicular to the flow direction.

[18] A spacer group including a plurality of sheet-shaped spacers each having a rectangular shape when viewed in the thickness direction, A group of spacers, wherein the tolerance of the creepage distance A described below among the plurality of spacers is 0.010 to 2.0 mm. (Creepage distance A) The creepage distance A is defined by the following methods (1-1) and (1-2), and its tolerance is calculated from 10 arbitrary spacers. (1-1) A first cell is placed on the first flat surface side of a spacer, and a second cell is placed on the second flat surface side of the spacer so that their flat surfaces are parallel to each other, and while maintaining their surfaces parallel to each other, the first cell and the second cell are brought close to a position where they come into contact with the spacer. (1-2) If the first cell and the spacer are in point contact, the contact point is defined as point a1. If the first cell and the spacer are in surface contact, the contact point is defined as point a1. If the second cell and the spacer are in point contact, the contact point is defined as point a2. If the second cell and the spacer are in surface contact, the contact point is defined as point a2. The shortest creepage distance from point a1 to point a2 along the surface of the spacer and across the short side of the spacer is defined as A (mm).

[19] The spacer group according to

[18] , wherein the tolerance of the intersection distance is 0.010 to 10 mm.

[20] A battery pack comprising a plurality of cells and the spacer group according to

[18] or

[19] . [Effects of the Invention]

[0007] According to the present invention, there are provided a method for manufacturing a spacer that can provide spacers that can stably provide excellent thermal insulation performance, a group of spacers that can stably provide excellent thermal insulation performance, and a battery pack using the group of spacers. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a spacer manufactured by a manufacturing method according to an embodiment. [Figure 2] 5A and 5B are schematic diagrams illustrating an inner packaging material supplying step in a spacer manufacturing method according to an example of an embodiment. [Figure 3] 5A to 5C are schematic diagrams illustrating an outer packaging material supplying step and a sealing step in a spacer manufacturing method according to an example of an embodiment. [Figure 4]5A to 5C are schematic diagrams illustrating a cutting step and an inspection step in a spacer manufacturing method according to an example of an embodiment. [Figure 5] 10A to 10C are schematic diagrams illustrating degassing in a sealing step of a spacer manufacturing method according to an example of an embodiment. [Figure 6] 1 is a cross-sectional view schematically illustrating a battery pack according to an embodiment; [Figure 7] FIG. 2 is a schematic diagram illustrating a creepage distance A of a spacer. [Figure 8] FIG. 2 is a schematic diagram illustrating a creepage distance A of a spacer. [Figure 9] FIG. 2 is a schematic diagram illustrating a creepage distance A of a spacer. [Figure 10] FIG. 2 is a schematic diagram illustrating a creepage distance A of a spacer. [Figure 11] 10 is a diagram illustrating the distance between the intersection of the diagonal lines of the spacer and the intersection of the diagonal lines of the inner packaging material in a plan view of the spacer seen from the thickness direction. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. The dimensional ratios in the drawings are for the convenience of explanation and may differ from the actual ratios. Furthermore, the same components in the drawings will be indicated by the same reference numerals, and descriptions of overlapping components may be omitted.

[0010] [Spacer manufacturing method] The spacer manufacturing method according to the embodiment is a method for manufacturing spacers provided between the cells that make up a battery pack. The spacers are members that prevent the cells from coming into contact with each other.

[0011] The method for manufacturing a spacer according to the embodiment includes the following inner packaging material supplying step, outer packaging material supplying step, and sealing step. Packaging material supplying process: Packaging material is supplied. Exterior material supply process: Exterior materials are supplied. Sealing step: A laminate is formed by sandwiching both sides of the inner packaging material between the outer packaging materials, and the outer packaging materials are sealed together around the inner packaging material to form a sealed body. In the spacer manufacturing method according to the embodiment, the inner case material supplying step includes causing the inner case material to absorb a liquid.

[0012] The method for manufacturing a spacer according to the embodiment preferably includes the following cutting step after the sealing step, and more preferably includes the following inspection step. Cutting step: The encapsulated body is cut into rectangular shapes. Inspection step: inspecting the appearance of the sealed body.

[0013] <Spacer> Fig. 1 is a cross-sectional view showing a typical example of a spacer manufactured by a manufacturing method according to an embodiment. The example spacer 20 shown in Fig. 1 includes an inner packaging material 22 and an outer packaging material 24 in which the inner packaging material 22 is sealed. Typically, the inner packaging material 22, which has a rectangular planar shape, is placed between two outer packaging materials 24, each having a rectangular planar shape, and the outer packaging materials 24 are sealed together at outer edge portions 26 around the periphery of the inner packaging material 22.

[0014] The spacer may be filled with a heat insulating material, typically heat insulating paper, but is not limited thereto. The insulating material may include cotton sheets, polyimide fibers, aramid fibers, polytetrafluoroethylene (PTFE) fibers, glass fibers, rock wool, ceramic fibers, and the like. The insulating material may include particles such as silica particles, alumina particles, calcium silicate, clay minerals, vermiculite, mica, cement, perlite, fumed silica, and aerogel.

[0015] The thermal conductivity of the heat insulating material is preferably 0.3 W / (m·K) or less, and more preferably 0.1 W / (m·K) or less. The thermal conductivity of the heat insulating material can be measured by the cyclic heating method described in JIS R2616. For example, temperature-controllable heaters are installed on the top and bottom surfaces of the test specimen (insulating material), and the upper heater applies periodic temperature fluctuations in the thickness direction, while the lower heater controls the lower surface at a constant temperature.The thermal diffusivity is then calculated from the phase difference (time difference) that occurs when the temperature fluctuations propagate from the top surface of the test specimen to the middle surface, and the thermal conductivity is calculated from the product of the specific heat and density.

[0016] The density of the insulation is 0.23 g / cm 3 More than 0.25 g / cm is preferable. 3 More preferably, 0.28 g / cm 3 If the density of the heat insulating material is equal to or greater than the lower limit, the deformation of the spacer during compression tends to be small. 3 Preferably less than 1.00 g / cm 3 Less than 0.90 g / cm is more preferable. 3 If the density of the heat insulating material is equal to or less than the upper limit, the heat insulating property tends to be good because the internal voids have many air layers. The preferable lower and upper limits of the density of the heat insulating material can be arbitrarily combined, and for example, it is 0.23 to 1.10 g / cm. 3 is preferred, and 0.25 to 1.00 g / cm 3 More preferably, 0.28 to 0.90 g / cm 3 is more preferable.

[0017] The spacer's encapsulating material is preferably made of a thermal insulating material containing a liquid, as this is more effective in suppressing thermal runaway in the battery pack. In a battery pack, if one of the cells is damaged due to overcharging, an internal short circuit, or the like, the battery surface temperature can reach several hundred degrees, which can then be transmitted to the surrounding cells, causing damage to spread throughout the entire battery pack. However, if the insulating material contains a liquid, the liquid in the encapsulating material can evaporate if one of the cells generates abnormal heat, absorbing the heat of vaporization from the surrounding area and suppressing the temperature rise.

[0018] The liquid held in the heat insulating material preferably has a boiling point of 80 to 250°C at normal pressure, and more preferably has a boiling point of 100 to 150°C at normal pressure. Examples of the liquid include water, alcohols, esters, ethers, ketones, hydrocarbons, fluorine-based compounds, and silicone oils, with water being preferred. The liquid contained in the heat insulating material may be one type only or two or more types. The liquid held in the insulating material may contain additives such as substances that impart antifreeze properties (antifreeze agents), preservatives, pH adjusters, and the like.

[0019] The outer packaging material may be any material that can seal the inner packaging material, and for example, a resin sheet or a metal sheet can be used. A laminate in which a metal foil and a resin layer are laminated is preferred as the packaging material because it is easy to obtain excellent heat resistance and strength. For example, a laminate of three or more layers including a resin layer, a metal foil, and a sealant layer can be mentioned.

[0020] Examples of metal foils include aluminum foil, copper foil, tin foil, nickel foil, stainless steel foil, lead foil, tin-lead alloy foil, bronze foil, silver foil, iridium foil, and phosphor bronze foil. Among these, aluminum foil, copper foil, and nickel foil are preferred, and aluminum foil is particularly preferred.

[0021] The resin constituting the resin layer can be at least one of a thermosetting resin and a thermoplastic resin, with a thermoplastic resin being preferred. Examples of the resin include olefin resins such as polyethylene and polypropylene, polystyrene, nylon, acrylic resins, epoxy resins, polyurethane, polyether ether ketone, polyethylene terephthalate, polyphenylene sulfide, polycarbonate, and aramid. Among these, polypropylene, nylon, and polyethylene terephthalate are preferred.

[0022] The thickness of the exterior material is not particularly limited and can be, for example, 5 to 200 μm. When the exterior material is a laminate, for example, the metal foil can be 3 to 50 μm thick and the resin layer can be 2 to 150 μm thick.

[0023] Examples of ways of housing the inner packaging material within the outer packaging material include, but are not limited to, sandwiching the inner packaging material between two sheets of outer packaging material and sealing the outer edges of the inner packaging material by heat fusion, adhesive, etc. Alternatively, one sheet of outer packaging material may be folded to sandwich the inner packaging material therebetween, and the outer edges of the inner packaging material on the outer packaging material may be joined by heat fusion, adhesive, etc. to seal the inner packaging material.

[0024] The width of the outer edge of the spacer is preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 4 mm or more. If the width of the outer edge of the spacer is equal to or greater than the lower limit, sufficient peel strength can be obtained and the amount of liquid or gas contained therein can be maintained for a long period of time. The width of the outer edge of the spacer is preferably 10 mm or less, more preferably 9 mm or less, and even more preferably 8 mm or less. If the width of the outer edge of the spacer is equal to or less than the upper limit, functions other than sealing can be efficiently designed. The preferred lower and upper limits of the width of the outer edge of the spacer can be arbitrarily combined, and for example, 2 to 10 mm is preferred, 3 to 9 mm is more preferred, and 4 to 8 mm is even more preferred.

[0025] The ratio of the area of ​​the spacer to the area of ​​the cell is preferably 0.8 or more, more preferably 0.9 or more, and even more preferably 0.95 or more. If the area ratio of the spacer to the cell is equal to or greater than the lower limit, short circuits due to contact between the cells are less likely to occur, and the pressure applied to the surface of the cell is more uniform, tending to prevent performance degradation over time. The area ratio of the spacer to the cell is preferably 1.2 or less, more preferably 1.1 or less, and even more preferably 1.05 or less. If the area ratio of the spacer to the cell is equal to or less than the upper limit, the battery pack is more likely to be miniaturized and the battery energy density tends to be higher. The preferable lower and upper limits of the area ratio of the spacer to the cell can be arbitrarily combined, and for example, 0.8 to 1.2 is preferred, 0.9 to 1.1 is more preferred, and 0.95 to 1.05 is even more preferred.

[0026] <Manufacturing equipment> A manufacturing apparatus used in a manufacturing method according to an embodiment will be described below. Fig. 2 is a schematic diagram showing an inner packaging material supplying device 110 used in the inner packaging material supplying step. Fig. 3 is a schematic diagram showing an outer packaging material supplying device 120 used in the outer packaging material supplying step and a sealing device 130 used in the sealing step. Fig. 4 is a schematic diagram showing a cutting device 140 used in the cutting step and an inspection device 150 used in the inspection step. The spacer manufacturing method according to one embodiment uses a spacer manufacturing apparatus 100 that includes an inner wrapping material supply device 110, an outer wrapping material supply device 120, a sealing device 130, a cutting device 140, and an inspection device 150.

[0027] As shown in Figure 2, the packaging material supplying device 110 comprises a packaging material supplying means 111 that supplies a long strip of insulation material 22A onto a first conveyor 114, a liquid supplying means 112 that supplies liquid L to the strip of insulation material 22A on the first conveyor 114 supplied by the packaging material supplying means 111, and a cutting means 113 that cuts the strip of insulation material 22A containing the liquid.

[0028] Strip-shaped insulating material 22A supplied onto first conveyor 114 from inner wrapping material supply means 111 is transported with both flat surfaces parallel to the horizontal direction. The liquid supply means 112 may be any means capable of supplying the liquid L to the strip-shaped heat insulating material 22A on the first conveyor 114, and may include, for example, a means equipped with a syringe pump and a slit nozzle.

[0029] In the example shown in FIG. 2, two inner casing material supply means 111 and two liquid supply means 112 are provided alternately in the flow direction, so that two layers of strip-shaped insulating material 22A containing liquid L are stacked. The number of encapsulating material supply means 111 and liquid supply means 112 is not limited to two, but may be one, or three or more. In other words, the configuration is not limited to two layers of strip-shaped insulating material 22A containing liquid L stacked, but may be one layer, or three or more layers. It is preferable to place an edge position controller (EPC) at the position where the strip insulation material 22A is stacked, and use the EPC to control the position of the side edge of the stacked strip insulation material 22A. This makes it possible to further reduce the tolerance of the intersection distance D, which will be described later.

[0030] The cutting means 113 is equipped with a cutting blade that cuts the strip insulation material 22A in a direction perpendicular to the flow direction, i.e., along the width direction of the strip insulation material 22A. By cutting the strip insulation material 22A at predetermined intervals with the cutting means 113, multiple rectangular inner wrapping materials 22 are formed one after another. By cutting the strip-shaped insulation material 22A containing liquid L in a stacked state at once using cutting means 113, the individual insulation materials that make up the inner packaging material 22 are less likely to shift, and the tolerance of the intersection distance D described below can be made smaller. The cutting means 113 may be configured to cut the strip-shaped heat insulating material 22A with a laser.

[0031] In the inner packaging material supply device 110, the plurality of cut inner packaging materials 22 are transported from a first conveyor 114 to a second conveyor 115. The transport speed of the second conveyor 115 is faster than the transport speed of the first conveyor 114, so that the spaces between the inner packaging materials 22 become wider as they move from the first conveyor 114 to the second conveyor 115. When transported by a conveyor, the position of the inner packaging material 22 is less likely to shift than when transported by a robot arm, and the tolerance of the intersection distance D, which will be described later, can be made smaller.

[0032] The outer packaging material supply device 120 includes a first outer packaging material supply means 121 that supplies a long strip-shaped outer packaging material 24A to the upper surface side of each inner packaging material 22 after cutting, and a second outer packaging material supply means 122 that supplies a long strip-shaped outer packaging material 24A to the lower surface side of each inner packaging material 22.

[0033] The sealing device 130 is a device that seals the strip-shaped exterior material 24A around the inner cover material 22 in the stack 25 of the strip-shaped exterior material 24A, the inner cover material 22, and the strip-shaped exterior material 24A. The sealing device 130 preferably includes deaeration means 131 for removing air existing between the pair of strip-shaped exterior materials 24A in the laminate 25, as shown in FIG. Furthermore, the sealing device 130 preferably includes sealing means 134 for sealing the strip-shaped exterior materials 24A around the inner packaging material 22 in the laminate 25 while the degassing means 131 is in a degassing state.

[0034] The form of the sealing means 134 is not particularly limited, and examples include a form having a first sealing portion that seals (side seals) both sides of the width of each inner packaging material 22 in a pair of strip-shaped outer packaging materials 24A of the laminate 25 along the flow direction, and a second sealing portion that seals (end seals) between each inner packaging material 22 in the pair of strip-shaped outer packaging materials 24A of the laminate 25 along the width direction. The first and second sealing portions of the sealing means 134 are not particularly limited, and for example, a heat sealer can be used.

[0035] The deaeration means 131 comprises a receiving stand 132 and a sponge body 133 that is arranged above the receiving stand 132 and is capable of moving up and down. The deaeration means 131 presses the sponge body 133 from above against the stack 25 on the receiving stand 132 to compress it, thereby discharging the air contained between the pair of strip-shaped exterior materials 24A, mainly contained in the inner packaging material 22, to the outside.

[0036] By using the degassing means 131 during sealing by the sealing device 130, degassing can be easily performed without creating a vacuum around the laminate 25. Furthermore, compared to creating a vacuum around the laminate 25, this method improves processing speed and makes it easier to accommodate changes in the size of the target spacer. Furthermore, by changing the pressure when compressing the laminate 25 with the sponge body 133, the degassing state within the laminate 25 can be easily changed. Furthermore, by sealing the inner packaging material 22 of the laminate 25 while pressing it with the sponge body 133, it is possible to prevent the inner packaging material 22 from shifting position during sealing, thereby making it possible to further reduce the tolerance of the intersection distance D, which will be described later.

[0037] In the sealed body 28 after sealing by the sealing device 130, the multiple inner packaging materials 22 are individually sealed at predetermined intervals in the flow direction. The cutting device 140 is a device that cuts the sealed portion around the inner packing material 22 of the sealed body 28 after sealing, typically into a rectangular shape, and punches out spacers 20. The cutting device 140 may be any device that can punch out a plurality of spacers 20 from the sealed body 28, and examples of such devices include a Thomson die and a metal mold. The cutting device 140 may also be a device that cuts the sealed portion around the inner packing material 22 in the sealed body 28 using a laser.

[0038] The cutting device 140 preferably has a mechanism for adjusting the position using alignment marks printed in advance on the strip-shaped exterior material 24A when punching each spacer 20 from the sealing body 28. By providing such a position adjustment mechanism, the external dimensional accuracy of the obtained spacers 20 is improved. The cutting device 140 may also include a means for forming ear holes in the outer edge of the periphery of the inner cover material 22 when punching out each spacer 20 from the sealing body 28 .

[0039] The inspection device 150 is a device that inspects the outer shape and appearance of each spacer 20 obtained by cutting the sealing body 28, and sends any defective products to a disposal route to separate them from the finished product. An example of the inspection device 150 is a device that includes a light irradiation means that irradiates light from various angles onto the surface of the portion of the spacer 20 that contains the inner packaging material 22, an imaging means that photographs the surface of the portion of the spacer 20 that contains the inner packaging material 22, and a judgment means that analyzes the photographed image to determine whether or not there are wrinkles.

[0040] The location where a spacer 20 determined to be defective is sent to the disposal course is not particularly limited, and it may be sent to the disposal course from the inspection device 150, or it may be sent to a disposal course that branches off downstream of the inspection device 150.

[0041] <Manufacturing method> Hereinafter, a method using the above-described manufacturing apparatus 100 will be described as an example of a method for manufacturing a spacer according to the embodiment.

[0042] (Packaging material supply process) The inner casing material supply step is a step of supplying the inner casing material, and preferably includes the steps of supplying a long strip of insulation material, soaking the strip of insulation material in a liquid, preferably water, stacking the strip of insulation material, and cutting the stacked strip of insulation material perpendicular to the flow direction to form sheets of inner casing material. It may also include supplying the inner casing material with one end of the width perpendicular to the flow direction fixed.

[0043] 2, in the inner cover material supply device 110, inner cover material supply means 111 supplies a long strip of insulating material 22A unwound from a roll of raw material onto a first conveyor 114, and liquid supply means 112 drips liquid L onto the strip of insulating material 22A. Furthermore, a subsequent inner cover material supply means 111 supplies a long strip of insulating material 22A unwound from a roll of raw material onto the strip of insulating material 22A containing liquid L, and the subsequent liquid supply means 112 drips liquid L onto the upper strip of insulating material 22A. In this way, strips of insulating material 22A containing liquid L can be stacked.

[0044] In a preferred embodiment, insulating paper is used as the strip-shaped insulating material 22 A. For example, an insulating paper roll having a predetermined width is used as a raw roll, and the strip-shaped insulating paper is supplied as the strip-shaped insulating material 22 A. Note that insulating materials other than the insulating paper described above for the spacer may also be used as the strip-shaped insulating material 22 A. The width of the insulating strip 22A can be set appropriately depending on the product size. By matching the width of the insulating strip 22A to the width of the inner casing material 22 of the spacer 20 product and not adjusting the width by cutting on the production line, it is possible to reduce misalignment of the inner casing material 22 within the spacer 20, thereby further reducing the tolerance of the intersection distance D described below. In one example, it is preferable to supply the strip-shaped heat insulating material 22A having a width that is 50 to 90% of the width perpendicular to the flow direction of the strip-shaped exterior material 24A.

[0045] In a preferred example, water is used as the liquid L. The water absorption rate referred to below is the ratio of the amount of water absorbed by the encapsulating material when the saturated water absorption capacity of the encapsulating material is taken as 100%. The higher the water absorption rate, the less likely each inner wrapping material 22 formed by cutting the strip-shaped insulation material 22A (described below) will shift position on the conveyor during transport. Therefore, the tolerance of the intersection distance D can be reduced. In a preferred example, the water absorption rate of the insulating paper is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. If the water absorption rate of the insulating paper is above the lower limit, the presence of liquid at the interface between the packaging material and the insulating paper provides adhesion, allowing for transport and sealing without shifting position. The water absorption rate of the insulating paper is preferably 100% or less, more preferably 98% or less, and even more preferably 95% or less. If the water absorption rate of the insulating paper is below the upper limit, the insulating material can be transported and degassed without overflowing, allowing for sealing without liquid passing through the seal portion. The preferred lower and upper limits of the water absorption rate of the insulating paper can be arbitrarily combined, for example, 5 to 100% is preferred, 10 to 98% is more preferred, and 15 to 95% is even more preferred.

[0046] For example, by using a nozzle, preferably a slit nozzle, as the liquid supply means 112, the water absorption rate of the insulating paper can be stably adjusted to a predetermined value. From the perspective of uniform water absorption, it is preferable that the nozzle be positioned perpendicular to the flow direction. The water absorption rate of the insulating paper can be adjusted, for example, by changing the slit width of the slit nozzle. It should be noted that, instead of water, the liquid L may be a liquid other than water as described above in relation to the spacer.

[0047] The number of layers of the insulating strip 22A is not limited to 2 as long as it can provide the inner cover material 22 with a predetermined thickness. The number of layers of the insulating strip 22A can be, for example, 1 to 6, 1 to 4, 1 to 3, or 1 to 2.

[0048] It is preferable that the misalignment in the width direction between stacked strip insulation materials 22A be within 1 mm. When stacking three or more strip insulation materials 22A, it is preferable that the misalignment between all of the strip insulation materials 22A be within 1 mm. This makes it possible to further reduce the tolerance of the intersection distance D, which will be described later.

[0049] The position of the side edges of the stacked strip insulation materials 22A is preferably controlled by an edge position controller (EPC), which allows the misalignment of the stacked strip insulation materials 22A in the width direction to be stably controlled to within 1 mm, further reducing the tolerance of the intersection distance D described below.

[0050] The stacked strip insulation material 22A is cut intermittently at predetermined intervals by cutting means 113 in a direction perpendicular to the flow direction, i.e., along the width direction of the strip insulation material 22A, thereby sequentially forming multiple rectangular inner casing materials 22. By cutting the strip insulation material 22A containing liquid L at once while it is stacked, the individual insulation materials that make up the inner casing material 22 are less likely to shift, and the tolerance of the intersection distance D, which will be described later, can be made smaller. It is preferable that the cutting by the cutting means 113 is carried out so that the cut surface is as perpendicular as possible to the plane of the strip-shaped heat insulating material 22A. It is preferable that the deviation in length of each inner packaging material 22 in the flow direction be within 1 mm, which makes it possible to further reduce the tolerance of the intersection distance D, which will be described later.

[0051] After cutting, the transport speed of the second conveyor 115 is set faster than the transport speed of the first conveyor 114, thereby increasing the spacing between the cut inner packaging materials 22. The spacing between the inner packaging materials 22 can be freely adjusted by adjusting the difference between the transport speeds of the second conveyor 115 and the first conveyor 114. Adjusting the spacing between the inner packaging materials 22 can improve processing speed.

[0052] (Outer packaging material supply process) 3, in outer packaging material supply device 120, first packaging material supply means 121 supplies long strip-shaped outer packaging material 24A unwound from a roll of raw material to the upper side of each cut inner packaging material 22 being conveyed. Second packaging material supply means 122 supplies long strip-shaped outer packaging material 24A unwound from a roll of raw material to the lower side of each inner packaging material 22 being conveyed. This produces stack 25 in which strip-shaped outer packaging material 24A, inner packaging material 22, and strip-shaped outer packaging material 24A are stacked.

[0053] The strip-shaped exterior material 24A may be a roll of exterior material having a predetermined width, and the strip-shaped exterior material may be supplied from the roll of exterior material. The exterior material may be any of the exterior materials described above in relation to the spacer. The width of the strip-shaped heat insulating material 22A can be set appropriately depending on the product size.

[0054] At least one of a registration mark for positioning in the sealing process and an alignment mark for positioning in the cutting process may be printed in advance on the surface of at least one of the pair of strip-shaped exterior materials 24A, preferably on the upper surface of the strip-shaped exterior material 24A supplied above each inner packaging material 22. By using these marks for positioning in the sealing process and cutting process, the dimensional accuracy of the obtained spacer 20 is improved, and the tolerance of the creepage distance A and the tolerance of the intersection distance D, which will be described later, can be made smaller.

[0055] (Sealing process) In the sealing step, in the stack 25 in which each inner packaging material 22 is sandwiched between strip-shaped exterior materials 24A, the outer edges of the pair of strip-shaped exterior materials 24A around each inner packaging material 22 are sealed to form a sealed body . In the sealing step using sealing device 130, it is preferable to remove air between the pair of strip-shaped exterior materials 24A in stack 25 using degassing means 131 as shown in Fig. 5. Then, it is preferable to seal the strip-shaped exterior materials 24A around inner packaging material 22 in stack 25 while degassing using degassing means 131.

[0056] More specifically, the degassing means 131 presses the sponge body 133A from above against the stack 25 that has been transferred onto the receiving table 132, compressing it. At this time, by pushing the stack 25 outward from its center, the air contained between the pair of strip-shaped exterior materials 24A, mainly in the inner packaging material 22, can be discharged to the outside. By performing degassing through compression with the sponge body 133, degassing can be easily performed without creating a vacuum around the stack 25, and processing speed is also improved. In addition, it is easy to accommodate changes in the size of the desired spacer, and the degassing state can be easily adjusted by changing the pressure during compression.

[0057] In the sealing step, degassing may be performed by sealing the periphery of the laminate 25 and reducing the pressure inside the sealed space in which the laminate 25 is present. That is, the sealing step may include sealing the degassed pair of exterior materials by reducing the pressure inside the space in which the laminate is sealed or by pushing the laminate from the center toward the outside.

[0058] More specifically, the degassing means 131 clamps the laminate 25 transferred onto the receiving table 132 with molds 133B from above and below to seal it, and then reduces the pressure inside the sealed space with a rotary pump. At this time, by providing a step of drilling tiny holes in the strip-shaped exterior material 24A before the clamping step, it becomes easier to reduce the pressure inside the space and the interior of the laminate 25. Furthermore, the degassing state can be easily adjusted by changing the pump output and decompression time during decompression.

[0059] While degassing is being performed using a pump by degassing means 131, the sealing mold of sealing means 134 simultaneously seals all four sides of each inner packaging material 22 in the pair of strip-shaped packaging materials 24A of laminate 25 in the width direction and flow direction. While the four sides are being sealed, the pressure inside mold 133B is restored, and after a predetermined sealing time has elapsed, the upper and lower molds are separated. This forms sealed body 28, the interior of which contains inner packaging material 22 and whose interior has been sufficiently degassed. The pair of belt-shaped exterior materials 24A is preferably sealed by heating, that is, by heat sealing.

[0060] While degassing is being carried out by degassing means 131, the first and second sealing parts of sealing means 134 seal both widthwise sides of each inner packaging material 22 in the pair of strip-shaped outer packaging materials 24A of stacked body 25 in the flow direction (side seals), and seal the spaces between each inner packaging material 22 in the pair of strip-shaped outer packaging materials 24A of stacked body 25 in the widthwise direction (end seals). This forms sealed body 28, the interior of which contains inner packaging material 22 and is sufficiently degassed. The pair of belt-shaped exterior materials 24A is preferably sealed by heating, that is, by heat sealing.

[0061] By carrying out the side sealing and end sealing in stages, it is possible to easily accommodate changes in the size of the target spacer 20.

[0062] It is preferable to adjust the sealing positions of the side seals and end seals in the sealing process while reading registration marks pre-printed on the surface of the belt-shaped exterior material 24A. This improves sealing accuracy, making it possible to further reduce the tolerance of the creepage distance A or the intersection distance D, which will be described later, of the obtained spacer 20.

[0063] (cutting process) For example, a cutting device 140 is used to cut the sealed portion around each inner packaging material 22 in the sealed body 28 into a rectangular shape, thereby successively producing a plurality of spacers 20 . The dimensional error of the rectangle cut in the cutting step is preferably 5.0 mm or less, more preferably 2.0 mm or less, even more preferably 1.5 mm or less, particularly preferably 1.0 mm or less, and even more preferably 0.5 mm or less. When cutting with a guillotine cutter, the dimensional error of the rectangle can be kept to 1.5 mm or less, and when cutting by punching, it is possible to cut with an accuracy of 0.5 mm or less. These allow the tolerance of the creepage distance A or the intersection distance D of the obtained spacer 20 to be further reduced, as will be described later.

[0064] In the cutting process, when punching each spacer 20 from the sealing body 28, it is preferable to adjust the cutting position based on the mark printed on the strip-shaped exterior material 24A. This improves the accuracy of the external dimensions of the obtained spacers 20, and makes it possible to further reduce the tolerance of the creepage distance A or the tolerance of the intersection distance D, which will be described later. In the cutting step, when punching out each spacer 20 from the sealing body 28, ear holes may be formed in the outer edge of the periphery of the inner cover material 22.

[0065] (Inspection process) For example, the appearance of the sealed body after cutting, i.e., each spacer 20 punched out from the sealed body 28, is inspected by the inspection device 150. Spacers 20 determined to be defective are removed and separated from the product. In this way, the inspection process may include determining and discarding spacers with defective appearances (defective products) based on the judgment results.

[0066] More specifically, for example, light is irradiated from various angles onto the front and back surfaces of the portion of spacer 20 containing encapsulating material 22, and the shape of the portion of spacer 20 containing encapsulating material 22 is photographed. By combining multiple images irradiated with light from different angles, it is possible to minimize shadow areas and obtain a contrast that is close to the actual shape. In addition, by appropriately adjusting the camera position, aperture value, and focus, it is possible to adjust the image quality to suit the inspection. The captured images are then evaluated using a preset algorithm to determine whether there are wrinkles on the front and back surfaces of the portion of the spacer 20 containing the inner packaging material 22, as well as any misalignment of the inner packaging material, and the product is then classified as defective or product-quality based on the results. Parameters used for sorting include, for example, brightness differences, or differences in shading, to measure the presence or absence of wrinkles and misalignment. It is also possible to use the detected area as the size of the wrinkles. Regarding misalignment of the inner packaging material, the distance between the edges of the inner packaging material and the distance between the outer edge and the edge of the inner packaging material are measured from the above-mentioned shading difference information, and the product is classified as defective or product-quality based on specified values. The sealed products determined to be non-defective can be transported to an outlet, and the sealed products determined to be defective can be discarded without being transported to an outlet. In the inspection process, for example, if there are wrinkles of 1 cm or more on the surface of the portion of the spacer 20 where the inner packaging material 22 is housed, it can be determined that the appearance is defective.

[0067] [Battery pack] According to an embodiment, the battery pack includes a plurality of cells and a spacer group. The spacer group includes a plurality of sheet-like spacers each having a rectangular shape when viewed in the thickness direction. Each spacer in the spacer group is disposed between the cells. 6 is a schematic diagram showing an example of a battery pack 1 according to an embodiment. The battery pack 1 includes a housing 30, a plurality of unit cells 10 housed in the housing 30, and a plurality of sheet-like spacers 20 arranged between the unit cells 10. The housing 30 includes a bottom plate 30a and a cylindrical side wall 30b rising from the peripheral edge of the bottom plate 30a. Within the housing 30, the cells 10 are arranged in the thickness direction, with spacers 20 disposed between the cells 10. In the example battery pack 1 shown in Fig. 6, spacers 20 are also disposed between the upper surface of the bottom plate 30a of the housing 30 and each cell 10, but the present invention is not limited to this configuration.

[0068] The spacers 20 are members that are provided between the cells 10 that make up the battery pack 1 to prevent the cells 10 from coming into contact with each other. Even if the cells 10 constituting the battery pack 1 expand during use, the expansion pressure is absorbed by the flexible spacers 20. Furthermore, the insulating effect of the spacers 20 makes it difficult for heat to be transferred to adjacent cells 10. Therefore, even if one of the cells 10 is damaged due to overcharging, an internal short circuit, or the like, causing the battery surface temperature to become excessively high, this damage is prevented from spreading to the surrounding cells 10 in a chain reaction, thereby preventing thermal runaway in the battery pack 1.

[0069] 1, for example, spacer 20 comprises inner packaging material 22 and outer packaging material 24 in which inner packaging material 22 is sealed. Typically, spacer 20 is formed by placing inner packaging material 22, which has a rectangular planar shape, between two outer packaging materials 24, each having a rectangular planar shape, and sealing the outer packaging materials 24 together at outer edge portions 26 around inner packaging material 22.

[0070] In the example shown in Figure 6, spacers 20 are stacked between each of the cells 10, but it is not necessary to place a spacer 20 between all of the cells 10; it is sufficient to place a spacer between at least one of the cells.

[0071] <Spacer group> Before being placed between the individual cells, the plurality of spacers can be bundled together and stored, transported, sold, etc. as a group of spacers. The spacers in the spacer group according to the embodiment have a creepage distance A tolerance of 0.010 to 2.0 mm, which is determined by a method described below. If the creepage distance A tolerance is within this range, the spacers can stably provide excellent heat insulating performance. The tolerance of the creepage distance A of the plurality of spacers in the spacer group according to the embodiment is preferably 0.010 to 1.0 mm, and more preferably 0.010 to 0.50 mm.

[0072] (Creepage distance A tolerance) The creepage distance A is defined by the following methods (1-1) and (1-2), and its tolerance is calculated from 10 arbitrary spacers. (1-1) A first cell is placed on the first flat surface side of a spacer, and a second cell is placed on the second flat surface side of the spacer so that their flat surfaces are parallel to each other, and while maintaining their surfaces parallel to each other, the first cell and the second cell are brought close to a position where they come into contact with the spacer. (1-2) If the first cell and the spacer are in point contact, the contact point is defined as point a1. If the first cell and the spacer are in surface contact, the contact point is defined as point a1. If the second cell and the spacer are in point contact, the contact point is defined as point a2. If the second cell and the spacer are in surface contact, the contact point is defined as point a2. The shortest creepage distance from point a1 to point a2 along the spacer and across the short side of the spacer is defined as A (mm).

[0073] In step (1-1), as shown in FIG. 7, the first cell 10A is placed on the first flat surface 20a side of the spacer 20, and the second cell 10B is placed on the second flat surface 20b side of the spacer 20 so that their flat surfaces are parallel to each other, and while maintaining their surfaces parallel to each other, the first cell 10A and the second cell 10B are brought close to a position where they come into contact with the spacer 20. In the example shown in FIG. 7, the spacer 20 and the first cell 10A are in surface contact with each other, and the spacer 20 and the second cell 10B are in surface contact with each other.

[0074] In this example, in step (1-2), a point on the edge of the contact portion between the first cell 10A and the spacer 20 is defined as point a1, and a point on the edge of the contact portion between the second cell 10B and the spacer 20 is defined as point a2. Then, as shown in Figs. 7 and 8, the creepage distance (the length of the dashed line in Fig. 4) that is the shortest distance along the surface of the spacer 20 and across the short side of the spacer to reach points a1 and a2 is calculated and defined as A (mm). Typically, points a1 and a2 that are the shortest distance along the surface of the spacer 20 are located on the same short side of the spacer 20 in the same cross section of the spacer 20 cut in the thickness direction. Similarly, find the creepage distance A for any 10 spacers and calculate their tolerance.

[0075] 9 is an example in which, in step (1-1), when the first cell 10A and the second cell 10B are brought close enough to contact the spacer 20, the spacer 20 and the first cell 10A are in point contact and the spacer 20 and the second cell 10B are in surface contact in a cross section cut in the thickness direction of the spacer 20. For example, this type of contact can occur when the first flat surface 20a of the spacer 20 has unevenness such as wrinkles.

[0076] In this example, in step (1-2), the point of contact between the first cell 10A and the spacer 20 is designated as point a1, and the point on the edge of the contact portion between the second cell 10B and the spacer 20 is designated as point a2. If there are multiple points of contact between the first cell 10A and the spacer 20, the point of contact closest to the outer edge of the spacer 20 is designated as point a1. 9 and 10, the creepage distance (the length of the dashed line in FIG. 10) that is the shortest distance between points a1 and a2 along the surface of the spacer 20 and across the short side of the spacer is found and defined as A (mm). Typically, point a2, where the distance along the surface of the spacer 20 is shortest, is located on the short side of the spacer 20 that is closest to point a1 within the same cross section of the spacer 20 cut in the thickness direction. Similarly, find the creepage distance A for any 10 spacers and calculate their tolerance.

[0077] In step (1-1), when the first cell 10A and the second cell 10B are brought close enough to contact the spacer 20, the creepage distance A is similarly calculated for an example in which the spacer 20 and the first cell 10A make point contact and the spacer 20 and the second cell 10B make point contact in a cross section of the spacer 20 cut in the thickness direction.

[0078] In this example, in step (1-2), the contact point between the first cell 10A and the spacer 20 is defined as point a1, and the contact point between the second cell 10B and the spacer 20 is defined as point a2. Then, the creepage distance between points a1 and a2, which is the shortest distance along the surface of the spacer 20, is calculated and defined as A (mm). If there are multiple contact points between the first cell 10A and the spacer 20 and multiple contact points between the second cell 10B and the spacer 20, the contact points which are the shortest distance along the surface of the spacer 20 are selected as points a1 and a2. Similarly, find the creepage distance A for any 10 spacers and calculate their tolerance.

[0079] The tolerance of the creepage distance A tends to increase if, in step (1-1), at least one of the contact between the first cell and the spacer and the contact between the second cell and the spacer is point contact due to wrinkles or other irregularities on the spacer surface. Therefore, the battery pack according to the embodiment preferably includes spacers that are free of wrinkles or other irregularities on the surface so that the first cell and the spacer and the second cell and the spacer are in surface contact with each other for all 10 spacers arbitrarily selected when calculating the creepage distance A.

[0080] (Intersection distance tolerance) In the battery pack according to the above embodiment, it is preferable that the tolerance of the distance between the intersection of the diagonal lines of the spacer and the intersection of the diagonal lines of the inner casing material (hereinafter also referred to as "intersection distance D") in a plan view of the spacer from the thickness direction is 0.010 to 10 mm. 11 is a plan view conveniently showing a case where the position of the inner packaging material 22 in the spacer 20 is misaligned. When the intersection point of the diagonal of the spacer 20, which has a rectangular planar shape, i.e., the diagonal of the outer packaging material 24, which also has a rectangular planar shape, is defined as point a, and the intersection point of the diagonal of the inner packaging material 22, which also has a rectangular planar shape, is defined as point b, the intersection distance D is the distance between points a and b. The tolerance of the intersection distance D is calculated from 10 arbitrary spacers.

[0081] If the tolerance of the intersection distance D is within the above range, the spacer can stably provide excellent heat insulating performance. The tolerance of the intersection distance D of the plurality of spacers in the battery pack according to this embodiment is preferably 0.010 to 5.0 mm, and more preferably 0.010 to 2.5 mm.

[0082] <Single cell> Examples of the single cell include a lithium ion secondary battery having a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, and an electrolyte. Secondary batteries such as a lithium ion all-solid-state battery, a nickel-metal hydride battery, a nickel-cadmium battery, and a lead-acid battery can also be used as the single cell.

[0083] The use of the assembled battery is not particularly limited, and the assembled battery can be applied to, for example, battery packs to be mounted on electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric heavy machinery, electric motorcycles, electrically assisted bicycles, ships, aircraft, trains, uninterruptible power supplies, home energy storage systems, and storage battery systems for stabilizing power systems that use renewable energy.

[0084] The present invention is not limited to the above-described embodiment. For example, instead of using a strip-shaped insulating material or a strip-shaped packaging material, a spacer may be manufactured by using a sheet of insulating material and a sheet of packaging material and performing the inner packaging material supply step, packaging material supply step, and sealing step. In this case, after the sealing step, the outer edge of one or two sides of the sealed body may be cut to adjust the dimensions. In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0085] 1 battery pack 10 D cells 10A 1st cell 10B Second cell 20 spacer 20a First plane 20b Second Plane 22 Packaging material 22A Strip insulation 24 Exterior materials 26 outer edge 30 Case 100 Spacer manufacturing equipment 110 Packaging material supply device 111 Packaging material supply means 112 Liquid supply means 120 Outer packaging material supply device 121 First exterior material supply means 122 Second exterior material supply means 130 Sealing device 131 Degassing means 140 Cutting device 150 Inspection equipment

Claims

1. A method for manufacturing a spacer including an inner material and an outer material, the method includes an inner packaging material supplying step of supplying a strip-shaped inner packaging material and cutting the inner packaging material in a direction perpendicular to the flow direction; an outer packaging material supplying step of supplying an outer packaging material; a sealing step of forming a laminate in which both sides of the inner packaging material are sandwiched between the outer packaging materials and sealing the outer packaging materials around the inner packaging material to form a sealed body; a cutting step of cutting the sealed body into a rectangular shape after the sealing step; and an inspection step of inspecting the appearance of the surface of the sealed body, The method for manufacturing a spacer, wherein the inner casing material supplying step includes causing the inner casing material to absorb a liquid.

2. The manufacturing method according to claim 1 , wherein the sealing step includes sealing outer edges of a pair of exterior materials.

3. The manufacturing method according to claim 1 , wherein the sealing step includes degassing air contained between the pair of exterior materials and sealing outer edges of the pair of exterior materials.

4. 2. The manufacturing method according to claim 1, wherein the sealing step includes degassing air contained between a pair of exterior materials by pressing the laminate from the center outward, and sealing outer edge portions of the pair of exterior materials.

5. The manufacturing method according to claim 1, wherein the dimensional error of the cut rectangle is 5.0 mm or less.

6. The manufacturing method according to claim 1, wherein the dimensional error of the cut rectangle is 2.0 mm or less.

7. The manufacturing method according to claim 1, wherein the dimensional error of the cut rectangle is 1.0 mm or less.

8. The manufacturing method according to claim 1 , further comprising adjusting a cutting position of the sealing body based on a mark printed on the exterior material.

9. The manufacturing method according to claim 1 , further comprising determining whether the product is good or bad based on the results of the inspection.

10. A method for determining whether a product is good or bad based on the results of the inspection, The sealed products that are judged to be non-defective are transported to the exit, The manufacturing method according to claim 1, further comprising discarding the sealed products determined to be defective without transporting them to an outlet.

11. The manufacturing method according to claim 1, wherein the inner packaging material supply step includes supplying the inner packaging material having a width that is 50 to 90% of the width perpendicular to the flow direction of the outer packaging material.

12. The manufacturing method according to claim 1 , wherein the step of supplying the inner packaging material includes causing the inner packaging material to absorb water so that the water absorption rate of the inner packaging material is 5% or more of the saturated water absorption amount of the inner packaging material.

13. The manufacturing method according to claim 1 , wherein the liquid to be absorbed into the inner packaging material is supplied from a nozzle in the inner packaging material supplying step.

14. The manufacturing method according to claim 1 , wherein the inner wrapping material supply step includes supplying the inner wrapping material with one end of the inner wrapping material positioned at a fixed position in a width direction perpendicular to the flow direction.

15. A method for producing a spacer group including a plurality of sheet-like spacers each having a rectangular shape as viewed in the thickness direction, using spacers produced by the production method according to claim 1, comprising: The method for manufacturing a spacer group, wherein the tolerance of the creepage distance A of the plurality of spacers is 0.010 to 1.0 mm. (Creepage distance A) The creepage distance A is defined by the following methods (1-1) and (1-2), and its tolerance is calculated from 10 arbitrary spacers. (1-1) A first cell is arranged on a first flat surface side of a spacer, and a second cell is arranged on a second flat surface side of the spacer so that their flat surfaces are parallel to each other, and while maintaining their surfaces parallel to each other, the first cell and the second cell are brought close to a position where they come into contact with the spacer. (1-2) When the first battery and the spacer are in point contact, the contact point is defined as point a1. When the first battery and the spacer are in surface contact, the contact point is defined as point a1. When the second battery and the spacer are in point contact, the contact point is defined as point a2. When the second battery and the spacer are in surface contact, the contact point is defined as point a2. The shortest creepage distance from point a1 to point a2 along the surface of the spacer and across the short side of the spacer is defined as A (mm).

16. A method for manufacturing a spacer group as described in Claim 15, wherein the tolerance of the intersection distance, which is the distance between the intersection of the diagonal lines of the spacer and the intersection of the diagonal lines of the encapsulating material when viewed in a plane from the thickness direction of the spacer, is 0.010 to 2.5 mm.

17. A method for manufacturing a battery pack including a plurality of cells and a spacer group, the method using the spacer group manufactured by the manufacturing method according to claim 15 or 16.

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