Spacer manufacturing method

Abstract

To provide a method for manufacturing a spacer that can suppress variations in the surface pressure distribution of battery cells. [Solution] A method for manufacturing a spacer having a pressurized body containing a plurality of inorganic particles, which is a spacer to be placed opposite a battery cell, includes a composition generation step S1 in which the surfaces of the plurality of inorganic particles are coated with a fluid in which a binder is dissolved or dispersed by a solvent to produce a composition; a placement step S2 in which the composition is placed in a mold; and a molding step S3 in which, after the placement step S2, a pressurized body is formed in which the inorganic particles are bound together by the binder by applying a certain pressure to the mold and vaporizing the solvent.

Description

Technical Field

[0001] The present invention relates to a method for producing a spacer.

Background Art

[0002] Patent Document 1 discloses a spacer as a heat transfer suppression sheet arranged side by side in a battery cell. The spacer is produced by charging a mixture obtained by mixing inorganic particles, glass fibers, a binder, and the like into a mold, pressurizing the mixture with a press machine, heating the obtained pressure-molded body, and then cooling the same.

[0003] Patent Document 2 discloses an aerogel composite material having heat insulating and sound insulating properties. The aerogel composite material is produced by mixing aerogel particles and a binder to form a slurry, and curing the slurry under compression. It is stated that the slurry may contain an opacifier, a surfactant, a flame retardant, fibers, and the like.

[0004] Patent Document 3 discloses a heat insulating material. The heat insulating material is produced by mixing silica aerogel particles, an adhesive and a surfactant, then curing the adhesive to bond a plurality of aerogel particles with the adhesive. The surfactant is carried on surfaces of the aerogel particles.

[0005] Patent Document 4 discloses a pressure-molded body obtained by molding a composition for molding a heat insulating material. For the pressure-molded body, a pressure-molded body is produced by mixing a first adhesive and a second adhesive having different reaction temperatures from a heat insulating material such as aerogel particles, charging the mixture into a press die, and heating and pressurizing the mixture. During the heating and pressurizing, pressing is performed with a press pressure such that the aerogel particles are not crushed and broken.

Prior Art Literature

Patent Literature

[0006]

Patent Document 1

[0007] Incidentally, battery cells expand during charging and return to their original size during discharge. If the surface pressure distribution transmitted from the spacer to the battery cell is uneven during expansion, the deterioration of the battery cell may be accelerated.

[0008] When spacers are formed from inorganic particles such as silica aerogel, the silica aerogel particles themselves possess elasticity. However, controlling the elastic modulus of the silica aerogel particles is not easy. Therefore, the surface shape of the spacer is an important factor in achieving a uniform surface pressure distribution in battery cells.

[0009] In other words, it is desirable that the surface shape of the spacer correspond to the surface shape of the battery cell. For example, if the surface of the battery cell is flat, it is desirable that the surface of the spacer be flat.

[0010] This invention has been made in view of the above background, and aims to provide a method for manufacturing a spacer that can suppress variations in the surface pressure distribution of battery cells. [Means for solving the problem]

[0011] One aspect of the present invention is a method for manufacturing a spacer that is disposed opposite a battery cell, the spacer having a pressure-molded body containing a plurality of inorganic particles, A composition production step that produces a composition in which the surfaces of multiple inorganic particles are coated with a fluid in which a binder is dissolved or dispersed by a solvent, a placement step of placing the composition in a molding die; a molding step of, after the placement step, applying a constant pressing force to the molding die and vaporizing the solvent to mold a pressure-molded body in which the inorganic particles are bound to each other by the binder, the method being for producing a spacer. [Advantageous Effects of Invention]

[0012] According to the production method, a constant pressing force is applied to the molding die in the molding step. This makes it possible to increase the flatness of the surface of the spacer that serves as the pressure-molded body. Accordingly, variation in the surface pressure distribution of a battery cell can be suppressed, and therefore deterioration of the battery cell can be suppressed. Brief Description of Drawings

[0013] [Figure 1] Cross-sectional view illustrating the assembled battery according to Embodiment 1. [Figure 2] Enlarged cross-sectional view of a spacer configuring the assembled battery. [Figure 3] Enlarged schematic diagram illustrating a heat insulating material configuring the spacer. [Figure 4] Enlarged schematic diagram illustrating a part of inorganic particles configuring the heat insulating material. [Figure 5] Flowchart illustrating the method for producing the spacer. [Figure 6] Schematic diagrams illustrating respective steps of the method for producing the spacer. [Figure 7] Exploded perspective view illustrating a molding die used in the molding step and an object to be molded. [Figure 8] Perspective view illustrating a molding die used in the molding step and an object to be molded. [Figure 9] Enlarged cross-sectional view illustrating a molding die and an object to be molded in the placement step and the molding step, the view corresponding to the IX-IX cross-section of Fig. 8. [Mode for Carrying Out the Invention]

[0014] (Embodiment 1) 1. Assembled battery 1 The assembled battery 1 will be described with reference to FIG. 1. The assembled battery 1 includes a housing 2, a plurality of battery cells 3, a plurality of spacers 4, and a bus bar 5.

[0015] The housing 2 includes at least a bottom surface 11. The bottom surface 11 is not limited to being positioned downward in the vertical direction, and may be positioned at another position. The housing 2 further includes a pair of side walls 12 and 13. A plurality of battery cells 3 are arranged on the bottom surface 11. In order to cool the battery cells 3, the bottom surface 11 may include a heat conductive member or a cooling member. The pair of side walls 12 and 13 are disposed opposing each other in the left-right direction of FIG. 1, and are configured to sandwich the arranged plurality of battery cells 3 from both sides. The pair of side walls 12 and 13 are formed of, for example, metal or resin. Note that the housing 2 may also include a pair of side walls opposing each other in the direction normal to the drawing sheet of FIG. 1.

[0016] Note that the bottom surface 11 and the pair of side walls 12 and 13 that constitute the housing 2 may be formed of different materials, or may be formed of the same material.

[0017] The plurality of battery cells 3 are housed in the housing 2. The plurality of battery cells 3 are arranged on the bottom surface 11 of the housing 2 and between the pair of side walls 12 and 13. Each battery cell 3 is positioned in the vertical direction with reference to the bottom surface 11 of the housing 2. Each battery cell 3 is formed in a flat shape. The battery cells 3 are arranged such that their flat surfaces face each other. The shape of the outer peripheral surface of the battery cell 3 (the contour shape viewed from the normal direction of the flat surface) is arbitrary. For example, the shape of the outer peripheral surface of the battery cell 3 is a polygon such as a rectangle.

[0018] The battery cell 3 is, for example, a rechargeable battery (also called a secondary battery). The battery cell 3 is one selected from the group, for example, lithium-ion batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and all-solid-state batteries. The battery cell 3 generates heat during charging and discharging. The heat generated by the battery cell 3 is transferred, for example, to the bottom surface 11 of the housing 2. In this way, the battery cell 3 is cooled.

[0019] Furthermore, battery cell 3 expands when charged and contracts when discharged. Therefore, battery cell 3 repeatedly expands and contracts as charging and discharging are repeated. Here, as mentioned above, battery cell 3 is formed in a flattened shape. Therefore, battery cell 3 mainly expands and contracts in the direction normal to the flattened plane (left-right direction in Figure 1).

[0020] The battery cell 3 includes a cell housing (not shown) made of, for example, metal or resin, and a cell body (not shown) housed within the cell housing. The battery cell 3 expands and contracts in accordance with the expansion and contraction of the cell body. The structure of the battery cell 3 is publicly known and is therefore omitted.

[0021] Multiple spacers 4 are housed in the housing 2. Each spacer 4 is formed in a flattened shape. For example, the thickness of a spacer 4 is thinner than the thickness of a battery cell 3. Some of the multiple spacers 4 are sandwiched between adjacent battery cells 3. Other parts of the multiple spacers 4 are sandwiched between the battery cells 3 and the side walls 12, 13, respectively. In other words, at least one side of each spacer 4 is positioned facing the battery cell 3. At least one side of each spacer 4 may be in direct contact with the battery cell 3, or it may be separated from the battery cell 3 via other members such as heat transfer members or thickness adjustment members.

[0022] The spacers 4, like the battery cells 3, are positioned on the bottom surface 11 of the housing 2, between the pair of side walls 12 and 13. Each spacer 4 is positioned vertically with respect to the bottom surface 11 of the housing 2. If the normal to the bottom surface 11 of the housing 2 is horizontal, each spacer 4 is positioned horizontally.

[0023] Spacer 4 has thermal insulation properties. In other words, spacer 4 suppresses the transfer of heat from one adjacent battery cell 3 to the opposite battery cell 3. If heat from one battery cell 3 is transferred to an adjacent battery cell 3, it may cause a heat chain reaction. As a result, the lifespan of the battery cell 3 will decrease. Therefore, the thermal insulation properties of spacer 4 help to suppress the reduction in the lifespan of the battery cell 3.

[0024] Furthermore, it is preferable that the spacer 4 is elastic. As described above, the battery cell 3 expands and contracts with charging and discharging. When the battery cell 3 expands and contracts, the spacer 4 is required to hold the battery cell 3 within a predetermined pressure range. This helps to suppress the reduction in the lifespan of the battery cell 3. Therefore, the spacer 4 is formed to have a predetermined elastic force when it deforms in accordance with the expansion and contraction of the battery cell 3.

[0025] The busbar 5 is positioned on top of the multiple battery cells 3, spanning across the multiple battery cells 3. The busbar 5 is made of an electrically conductive material and is electrically connected to the electrodes of the battery cells 3. Note that the busbar 5 is not limited to being positioned above the battery cells 3, but may also be positioned on the sides.

[0026] 2. Spacer 4 Spacer 4 will be described with reference to Figure 2. In Figure 2, the vertical direction corresponds to the horizontal direction in Figure 1. Spacer 4 includes an insulating material 21, an outer cover 22, and an inner cover 23. However, spacer 4 may include elements other than those described above (21-23).

[0027] The thermal insulation material 21 is formed in a flattened shape. Preferably, the contour shape of the thermal insulation material 21, when viewed from the direction normal to the flattened surface, corresponds to the outer shape of the battery cell 3. However, it is preferable that the thermal insulation material 21 has a shape that is slightly smaller than the outer shape of the battery cell 3. For example, the thermal insulation material 21 is formed in a polygon, such as a rectangle.

[0028] The thermal insulation material 21 can be made from various materials as long as they possess thermal insulation properties. For example, the thermal insulation material 21 may exhibit thermal insulation properties through the materials that make it up, or it may exhibit thermal insulation properties by holding a gas such as air inside. The thermal insulation material 21 may also contain, for example, multiple inorganic particles.

[0029] Furthermore, the thermal insulation material 21 may include materials with various purposes in addition to materials having thermal insulation properties. For example, the thermal insulation material 21 may include reinforcing materials to improve the strength of the thermal insulation material 21, or base materials to hold the thermal insulation material. Examples of reinforcing materials include reinforcing fibers. Reinforcing fibers can be inorganic fibers such as glass fibers or organic fibers such as resin fibers. In addition to being thread-like, reinforcing fibers can also be formed into, for example, woven fabrics or nonwoven fabrics.

[0030] The outer cover 22 is formed from a flexible sheet. The outer cover 22 covers the entire surface of the insulation material 21. Therefore, the outer cover 22 houses the insulation material 21.

[0031] The purpose of enclosing the insulation material 21 with the outer cover 22 is optional. For example, the outer cover 22 may serve to protect the surface of the insulation material 21. Also, if the insulation material 21 is formed of multiple particles, the outer cover 22 may function as a component to prevent dust generation by the insulation material 21. The outer cover 22 may also function to maintain the shape of the insulation material 21.

[0032] The outer cover 22 may be formed from a sheet without through holes. However, the outer cover 22 may have fine through holes.

[0033] The material of the outer cover 22 can be, for example, resin, cloth, paper, or metal. The outer cover 22 may be formed from a single material or may have a multi-layer structure made of multiple different materials. For example, the outer cover 22 may have a structure formed from a metal layer and a resin layer, a structure formed from a cloth layer containing resin and a metal layer, or a structure formed from a resin layer and a cloth layer.

[0034] The resin may include thermoplastic resins. Examples of such resins include polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene terephthalate (PET). Examples of fabrics include woven fabrics and nonwoven fabrics. The fibers of the fabric may also include thermoplastic resins.

[0035] The inner cover 23 is formed from a flexible sheet. The inner cover 23 is positioned inside the outer cover 22 and covers the insulation material 21. Thus, the inner cover 23 houses the insulation material 21 inside the outer cover 22.

[0036] The material of the inner cover 23 can be, for example, resin, cloth, paper, or metal. The inner cover 23 may be formed from a single material or may have a multi-layer structure made of multiple different materials. For example, the inner cover 23 may have a structure formed from a metal layer and a resin layer, a structure formed from a cloth layer containing resin and a metal layer, or a structure formed from a resin layer and a cloth layer.

[0037] The resin may include a thermoplastic resin. Examples of such resins include polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene terephthalate (PET). Examples of fabrics include woven fabrics and nonwoven fabrics. The fibers of the fabric may include the aforementioned thermoplastic resin.

[0038] For example, the outer cover 22 may be made of resin, and the inner cover 23 may be made of nonwoven or woven fabric. In this case, the outer cover 22 can function as a component that prevents dust generation by the heat insulating material 21, and the inner cover 23 can function as a component that protects the surface of the heat insulating material 21.

[0039] Furthermore, the inner cover 23 may be in close contact with the insulation material 21, or it may be positioned with an air layer in between. The outer cover 22 may be in close contact with the inner cover 23, or it may be positioned with an air layer in between. Figure 2 schematically shows the spacer 4, illustrating a case where there is an air layer between the inner cover 23 and the insulation material 21, and an air layer between the outer cover 22 and the inner cover 23. However, the configuration is not limited to this.

[0040] 3. Insulation material 21 3-1. Basic composition of insulation material 21 As described above, it is preferable that the spacer 4 has elasticity in addition to having thermal insulation properties. This allows the spacer 4 to hold the battery cell 3 within a predetermined pressure range when the battery cell 3 expands and contracts. In this case, it is preferable that the thermal insulation material 21 be made of a material that has thermal insulation properties and is also elastic.

[0041] As described above, the thermal insulation material 21 can be made from various materials as long as it has thermal insulation properties. As an example of the thermal insulation material 21, a case in which the thermal insulation material 21 is made from a material that has thermal insulation properties and is elastic will be explained with reference to Figures 3 and 4.

[0042] As shown in Figure 3, the thermal insulation material 21 includes at least a plurality of inorganic particles 31. The inorganic particles 31 consist of, for example, a porous structure. The inorganic particles 31, individually, have thermal insulation properties and elasticity.

[0043] The thermal insulation material 21 includes a binder 32. The binder 32 binds the inorganic particles 31 together. The binder 32 coats at least a portion of the surface of the inorganic particles 31 and binds adjacent inorganic particles 31 together. The binder 32 may coat all of the surface of the inorganic particles 31, or it may coat only a portion of it.

[0044] Furthermore, the thermal insulation material 21 includes voids 33 between the multiple inorganic particles. In addition to the inorganic particles 31 and the binder 32, the thermal insulation material 21 may also include at least one selected from infrared shielding particles, inorganic fibers, dispersants, reinforcing inorganic particles, flame retardants, etc.

[0045] 3-2.Inorganic particles 31 As shown in Figure 4, the inorganic particles 31 are formed by a skeleton created by the linkage of multiple primary particles 31a, with pores 31b between these skeletons. The diameter of the primary particles 31a forming the skeleton is preferably about 2-5 nm, and the size of the pores 31b formed between the skeletons is preferably about 10-50 nm. If most of the pores 31b are so-called mesopores with a size of 50 nm or less, the mesopores are smaller than the mean free path of air, thus restricting air convection and inhibiting heat transfer. The primary particles 31a forming the skeleton are mainly composed of inorganic materials such as silica, alumina, zirconia, and titania. Silica is preferred for the primary particles 31a due to its excellent chemical stability.

[0046] Examples of inorganic particles 31 include silica aerogel. Depending on the drying method used in the production of aerogel, those dried at atmospheric pressure are sometimes called "xerogels" and those dried under supercritical conditions are sometimes called "aerogels," but both are referred to as "aerogels." Silica aerogel is suitable because it has a good balance between the size of the skeleton and the size of the pores. Silica aerogel is produced, for example, by a sol-gel reaction of a solution containing two or more silane compounds with different numbers of siloxane bonds (hereinafter sometimes referred to as "silane compound-containing solution").

[0047] In addition to silica aerogel, the inorganic particles 31 may also include the following: The inorganic particles 31 may also be an aggregated structure in which nanoparticles with a particle diameter of less than 1 μm are linked together to form a framework. Examples of nanoparticles include fumed silica, wet silica, and those obtained by crushing or dispersing these, as well as those produced from nanoparticle sols such as colloidal silica and colloidal alumina.

[0048] 3-3. Binding agent 32 Suitable binders 32 include surfactants and water-soluble oligomers having both polar and nonpolar components in their side chains. Suitable surfactants include ionic surfactants (cationic surfactants, anionic surfactants, and amphoteric surfactants) and nonionic surfactants.

[0049] For example, using ionic surfactants can increase the viscosity of a composition even in relatively small amounts, or stabilize the dispersion of materials such as porous structures within the composition. Examples of ionic surfactants include sodium carboxymethylcellulose (CMC-Na), polycarboxylate amine salts, polycarboxylate ammonium salts, polycarboxylate sodium salts, and TEMPO-oxidized cellulose nanofiber (CNF-Na). When using nonionic surfactants, materials such as porous structures are more easily incorporated into the solvent during composition preparation. Furthermore, if these materials aggregate or separate within the composition, they are more easily redispersed, and the solvent is more easily discharged during pressure molding. Examples of nonionic surfactants include polyethylene oxide (PEO) and polyvinyl alcohol (PVA).

[0050] 3-4. Detailed configuration of insulation material 21 As shown in Figure 3, the thermal insulation material 21 is manufactured by pressure molding a composition containing a plurality of inorganic particles 31. In other words, the thermal insulation material 21 constitutes a pressure-molded body. Therefore, the spacer 4 includes the pressure-molded body.

[0051] The thermal insulation material 21 may consist solely of a pressure-molded body, or it may include a base material that supports the pressure-molded body. The base material may be placed on only one side in the thickness direction of the pressure-molded body, or it may be placed on both sides so as to sandwich the pressure-molded body. An adhesive layer may also be interposed between the pressure-molded body and the base material. The adhesive layer may contain not only adhesive components but also flame retardants and the like.

[0052] The inorganic particles 31 constituting the thermal insulation material 21 consist of particles of different shapes and sizes obtained by, for example, pulverizing a porous structure manufactured by the sol-gel method. A media-less pulverizing and mixing device such as a jet mill, or an agitator can be used for the pulverizing process. The inorganic particles 31 take on various shapes after pulverization, but it is desirable that they are not spherical.

[0053] The average particle size of the inorganic particles 31 is preferably 30 μm or larger from the viewpoint of increasing the pore volume and improving heat insulation. Powders with an average particle size of less than 30 μm are difficult to obtain by grinding, and fine voids tend to form between the particles, which may make the press-molded product brittle. A suitable average particle size is 50 μm or larger. On the other hand, from the viewpoint of ease of molding into a sheet and suppression of particle shedding, an average particle size of 150 μm or less is desirable. Powders with an average particle size exceeding 150 μm do not tend to form voids between particles, but the size of the voids tends to be large. A suitable average particle size is 120 μm or less. The average particle size of the porous structure powder is determined by the median diameter (D) obtained from the volume-based particle size distribution measured by laser diffraction-scattering. 50 ) should be adopted.

[0054] A composition having inorganic particles 31 may also contain other components of inorganic particles 31. From the viewpoint of ensuring the desired thermal insulation performance in the thermal insulation material 21, the content of inorganic particles 31 in the composition should be 65% by mass or more, preferably 70% by mass or more, when the solid content of the composition is 100% by mass. Here, solid content refers to components excluding volatile substances such as organic solvents and water. Other components include binders 32, infrared shielding particles, inorganic fibers, reinforcing inorganic particles, and flame retardants.

[0055] As shown in Figure 3, in the thermal insulation material 21 obtained by pressure molding a composition having inorganic particles 31, multiple inorganic particles 31 are arranged in a stacked manner. In the thermal insulation material 21, it is desirable that inorganic particles 31 of different shapes and sizes are randomly stacked.

[0056] Many of the inorganic particles 31 have shapes other than spherical, and their individual shapes and sizes differ. The packing state of the inorganic particles 31 is similar to the "nozura-zumi" style found in the stone walls of Japanese castles. "Nozura-zumi" is a stone masonry method in which natural stones or roughly cut stones are stacked without processing. There are small gaps 33 between the inorganic particles 31. The inorganic particles 31 are in contact with each other at points, lines, and surfaces, or in combination thereof, or they are arranged via a binder 32, and there is no regularity in their arrangement.

[0057] When the thermal insulation material 21 is compressed from the outside in the thickness direction, the binder material 32 undergoes viscoelastic deformation. As the compressive force increases, the inorganic particles 31 move and deform by shifting against each other. As the compressive force increases further, the elastic inorganic particles 31 deform. In other words, when the thermal insulation material 21 is compressed, the inorganic particles 31 and the binder material 32 deform while generating the desired reaction force, and when the load is removed, the inorganic particles 31 and the binder material 32 return to their original shape.

[0058] The amount of voids in the thermal insulation material 21 affects its thermal insulation properties. When the amount of voids 33 increases, i.e., when the porosity increases, heat transfer due to air convection increases, and thus the thermal insulation properties decrease. Therefore, if only thermal insulation properties are considered, it is desirable to have no voids 33. However, if the amount of voids 33 is small, the inorganic particles 31 may not shift easily when compressed from the outside, and the amount of deformation may decrease. Conversely, if the amount of voids 33 is too large, the contact points formed by points, lines, and surfaces of the inorganic particles 31, or a combination thereof, decrease, making it difficult for the elasticity of the inorganic particles 31 to be exhibited, and the recovery rate may decrease. Therefore, in the thermal insulation material 21, considering thermal insulation properties, deformability, and recovery properties, it is desirable that the porosity be between 1 and 50%. More preferably, the porosity is 20% or less, and even more preferably, the porosity is 15% or less.

[0059] The void ratio is a value obtained by scanning an electron microscope (SEM) to capture a cross-sectional image of the insulation material 21 in the thickness direction, and then binarizing the resulting cross-sectional image. The procedure is described below.

[0060] (1) First, take a cross-sectional SEM image of the insulation material 21 in the thickness direction at a magnification of 200x. (2) Next, the captured SEM images were subjected to contrast adjustment, noise reduction, and binarization in this order. The CLAHE (Contrast Limited Adaptive Histogram Equalization) algorithm was used for contrast adjustment. The parameters used were Contrast Limit: 2.0 and Grid Size: (8,8). A Non-Local Means Filter was used for noise reduction. The parameters used were h: 40, Template Window Size: 23, and Search Window Size: 39. Here, h is the filter strength, Template Window Size is the size of the area to be searched, and Search Window Size is the size of the area to be searched. Adaptive binarization was used for binarization. The parameters used were Block Size: 219 and C: 40. Here, Block Size is the range referenced when calculating the threshold, and C is the threshold correction. The threshold was calculated using the average value of the reference range. Finally, to remove minute noise, structures smaller than 15 μm (32 pixels) were removed from the binarized image. (3) The structures remaining on the screen were considered as voids, and the void ratio was calculated using the following equation (I). Void ratio (%) = Area of ​​voids / Total area of ​​screen × 100 ... (I)

[0061] 4. Manufacturing method of spacer 4 The manufacturing method for the spacer 4 will be explained with reference to Figures 5 to 9. The manufacturing method for the spacer 4 consists of a composition generation step S1, an arrangement step S2, a molding step S3, and a coating step S4.

[0062] In the composition production step S1, a composition 42 is produced in which the surfaces of multiple inorganic particles 31 are coated with a fluid 41 in which a binder 32 is dissolved or dispersed by a solvent. The composition production step S1 will be described in detail.

[0063] As shown in Figure 5, the inorganic particle material 131, binder 32, and solvent are prepared (S11: preparation step). In addition, infrared shielding particles, inorganic fibers, dispersants, reinforcing inorganic particles, flame retardants, etc. are prepared as needed.

[0064] The inorganic particle material 131 is the material for the inorganic particles 31 that form the spacer 4, and uses inorganic particles before the final crushing treatment. However, the inorganic particle material 131 may be the inorganic particles 31 that form the spacer 4 itself. In this case, the inorganic particle material 131 will be the inorganic particles after the crushing treatment.

[0065] The binder 32 is as described above. As will be discussed later, when water is used as the solvent, it is desirable that the binder 32 be a water-soluble material.

[0066] The solvent can be water, an organic solvent, or an inorganic solvent. Water is preferred as the solvent because it has a low environmental impact. Examples of organic solvents include alcohols, ketones, aromatic hydrocarbons, esters, and aliphatic hydrocarbons. Examples of inorganic solvents include sulfuric acid, hydrochloric acid, and aqueous ammonia. The solvent may be used alone or in combination of two or more.

[0067] Examples of organic solvents include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone. Examples of aromatic hydrocarbons include toluene, xylene, ethylbenzene, and mesitylene. Examples of esters include methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate. Examples of aliphatic hydrocarbons include hexane, heptane, cyclohexane, and methylcyclohexane.

[0068] As examples of inorganic particle material 131, binder 32, solvent, etc., the following can be prepared.

[0069] [Inorganic Particle Material] Crushed product of "Aerogel Particles P200" manufactured by Cabot Corporation, average particle size 100 μm, 50-95% by mass This product is solid 29 Analysis using Si-NMR with the DD method, at a MAS rotation speed of 10 kHz and a pulse waiting time of 5 seconds, revealed that the abundance of Q units was 78.3 mass% and the abundance of M units was 21.7 mass%. Based on these analysis results, it was confirmed that the silane compounds used in the manufacture of this product consisted of 78.3 mass% tetrafunctional silane compounds and 21.7 mass% monofunctional silane compounds, with the total being considered as 100 mass%.

[0070] [Binding agent] Polyethylene oxide "PEO-8" manufactured by Sumitomo Seika Co., Ltd., viscosity average molecular weight 1.7 million to 2.2 million, 0.5 to 15% by mass [Solvent] Water, 20-80% by mass [Silicon Carbide Powder] Fuji Random GC #4000, manufactured by Fuji Seisakusho Co., Ltd., average particle size 5 μm, 0-40% by mass [Glass Fiber] "ECS03-615" manufactured by Central Glass Fiber Co., Ltd., length 3 mm, fiber diameter 9 μm, 0-30% by mass

[0071] For example, the amount of solvent can be adjusted according to the proportion of voids 33 (porosity) in the spacer 4. As mentioned above, it is desirable that the porosity be between 1% and 50%. Preferably, the porosity is 20% or less, and more preferably, 15% or less. The amount of solvent should be set according to the desired porosity.

[0072] Next, as shown in Figure 5, the binder 32 and solvent are added to the container 50 (shown in Figure 6(a)). Then, by mixing the binder 32 and solvent, a fluid 41 is produced in which the binder 32 is dissolved or dispersed by the solvent (S12: Fluid production step). The fluid 41 can be produced using, for example, a stirrer. The binder 32 may be dissolved in the solvent, or it may simply be dispersed without dissolving. The fluid 41 may be a liquid, paste, or slurry.

[0073] Next, as shown in Figures 5 and 6(a), multiple inorganic particle materials 131 are added to the container 50 in which the fluid 41 is generated. Then, as shown in Figures 5 and 6(b), the fluid 41 and the multiple inorganic particle materials 131 are stirred to generate a composition 42 in which the surface of the inorganic particles 31 is coated with the fluid 41 (S13: coating step). In other words, by stirring the binder 32 and solvent that constitute the fluid 41 with the inorganic particle materials 131, the inorganic particle materials 131 are pulverized to obtain inorganic particles 31 of different shapes and sizes. Furthermore, this stirring coats the surface of the obtained inorganic particles 31 with the fluid 41. Composition 42 can be generated using, for example, a stirrer. In addition, if necessary, infrared shielding particles, inorganic fibers, dispersants, reinforcing inorganic particles, flame retardants, etc. can be added in the fluid generation step S12 or the coating step S13.

[0074] Following the composition generation step S1, the placement step S2 is performed. In the placement step S2, the composition 42 and the inner cover 23 (shown in Figure 2) are placed in the mold 60. The mold 60 will be described with reference to Figures 7 to 9.

[0075] The molding die 60 includes a lower die 61, an upper die 62, and a middle die 63. The lower die 61 includes a base portion 61a, a protrusion 61b, and a plurality of support elastic bodies 61c. The base portion 61a is a flat plate-shaped part that rests on the installation surface and has, for example, a rectangular plate shape. The protrusion 61b is located in the center of the upper surface of the base portion 61a and has a rectangular plate shape. The protrusion 61b is smaller than the outer shape of the base portion 61a. The upper surface of the protrusion 61b constitutes a first molding surface 60a for molding the lower surface of the object to be molded. The plurality of support elastic bodies 61c are arranged at intervals around the protrusion 61b on the upper surface of the base portion 61a. The support elastic bodies 61c are configured to be elastically deformable in the vertical direction. The support elastic bodies 61c can be, for example, spring members such as coil springs and leaf springs, or viscoelastic materials such as rubber and elastomers.

[0076] The upper mold 62 is positioned opposite the lower mold 61. The upper mold 62 has a rectangular plate shape. The central portion of the lower surface of the upper mold 62 constitutes a second molding surface 60b, which corresponds to the upper surface of the convex portion 61b of the lower mold 61. The second molding surface 60b forms the upper surface of the object to be molded. The outer peripheral portion of the lower surface of the upper mold 62 is recessed above the second molding surface 60b and constitutes a cover retaining surface.

[0077] The intermediate mold 63 has a ring shape. For example, the intermediate mold 63 has a rectangular ring shape. The inner circumferential surface of the intermediate mold 63 has a shape corresponding to the outer circumferential surface of the convex portion 61b of the lower mold 61. The inner circumferential surface of the intermediate mold 63 constitutes the third molding surface 60c for molding the outer circumferential surface of the object to be molded. However, it is preferable that grooves (not shown) for discharging vaporized solvent are formed on the inner circumferential surface of the intermediate mold 63. These grooves are formed, for example, to extend in the vertical direction. Instead of grooves, through holes may be formed. The lower surface of the intermediate mold 63 abuts against the upper surface of the support elastic body 61c of the lower mold 61. Furthermore, the upper surface of the intermediate mold 63 faces the cover retaining surface of the upper mold 62.

[0078] Then, as shown in Figures 7 and 9(a), the inner cover 23 and composition 42, which are the objects to be molded, are placed in the mold 60. The procedure will now be described in detail. First, the middle mold 63 is set in the lower mold 61. At this time, the middle mold 63 is located on the outer circumference side of the convex portion 61b of the lower mold 61 and is supported on the upper surface of the support elastic body 61c.

[0079] Next, the first inner cover member 23a of the inner cover 23 is positioned so as to span the first molding surface 60a, the third molding surface 60c, and the upper surface of the medium mold 63. Subsequently, the composition 42 is placed on the upper surface of the first inner cover member 23a of the inner cover 23, within the region formed by the first molding surface 60a and the third molding surface 60c. At this time, the upper surface of the composition 42 is smoothed.

[0080] Next, the second inner cover member 23b of the inner cover 23 is placed. The second inner cover member 23b covers the composition 42 and also covers the outer periphery of the first inner cover member 23a. Then, the upper mold 62 is placed on top of it. In this way, the inner cover 23 and the composition 42, which are the objects to be molded, are placed in the molding die 60.

[0081] The image of the composition 42 inside the mold 60 at this time is shown in Figure 6(c). That is, the coated inorganic particles 31 are arranged with sufficient gaps between them inside the molding surfaces 60a, 60b, and 60c of the mold 60. Note that in Figure 6(c), the inner cover 23 has been removed for the sake of clarity. The same applies to Figure 6(d).

[0082] Following the placement process S2, the molding process S3 is performed. In the molding process S3, as shown in Figures 5, 6(d), and 9(b), the heat insulating material 21, which is a pressure-molded body, is formed by heating and pressurizing the mold 60. This will be explained in detail below.

[0083] First, in molding step S3, a pressure-molded body is formed by applying a constant pressure to the mold 60 and vaporizing the solvent, thereby binding the inorganic particles 31 together with the binder 32. The constant pressure applied should be set according to the average particle size of the inorganic particles 31. Furthermore, the constant pressure applied should be set according to the type of solvent and binder 32 contained in the composition 42.

[0084] In this way, by applying a constant pressure to the mold 60, the flatness of the surface of the spacer 4, which includes the heat insulating material 21 and is a pressure-molded body, can be increased. Therefore, variations in the surface pressure distribution of the battery cell 3 can be suppressed. As a result, the degradation of the battery cell 3 can be suppressed.

[0085] Furthermore, in molding step S3, a constant pressure is applied while heating the mold 60. In this case, the mold 60 brings the object to be molded to a temperature above the melting point of the binder 32. The heating temperature of the mold 60 is set to a temperature higher than the vaporization temperature of the solvent. This allows the solvent contained in the composition 42 to be vaporized.

[0086] Furthermore, the heating temperature of the mold 60 should be set to a temperature above the melting point of the binder 32. This allows for the formation of a pressure-molded body in which the inorganic particles 31 are bound together by the binder 32. Alternatively, the heating temperature of the mold 60 should be set lower than the thermal decomposition temperature of the binder 32. This helps maintain the properties of the binder 32. For example, if the binder 32 is made of a viscoelastic material, the binder 32 can maintain the desired viscoelastic properties.

[0087] However, in molding step S3, instead of heating the mold 60, the internal pressure (cavity pressure) in the region within the molding surface 60a to 60c may be reduced. By reducing the pressure, the binder 32 can be melted and the solvent vaporized, similar to heating. Alternatively, in molding step S3, the mold 60 may be heated and the region within the molding surface 60a to 60c may be reduced.

[0088] When a constant pressure is applied to the mold 60, the upper mold 62 and the middle mold 63 move downward. At this time, the middle mold 63 is biased upward by the support elastic body 61c of the lower mold 61. Therefore, the upper mold 62 and the middle mold 63 can move downward while sandwiching the outer circumference of the inner cover 23.

[0089] Furthermore, grooves are formed on the inner circumferential surface of the medium mold 63 of the mold 60. In addition, support elastic bodies 61c are intermittently positioned between the upper surface of the base portion 61a of the lower mold 61 and the lower surface of the medium mold 63. Therefore, a gap exists between the upper surface of the base portion 61a and the lower surface of the medium mold 63. During heating and pressurization by the mold 60, the solvent constituting the composition 42 vaporizes. The vaporized solvent passes through the grooves on the inner circumferential surface of the medium mold 63 and reaches the gap between the upper surface of the base portion 61a and the lower surface of the medium mold 63. The vaporized solvent is then discharged to the outside of the mold 60. In this way, the vaporized solvent can be discharged to the outside of the pressurized molded body. By vaporizing the solvent, voids 33 can be formed between the multiple inorganic particles 31 in the heat insulating material 21, which is a pressurized molded body.

[0090] In the molding process S3, in addition to the composition 42, the inner cover 23 is also molded. This allows the inner cover 23 to be molded as well. Since the inner cover 23 is made of nonwoven or woven fabric, the vaporized solvent can pass through the inner cover 23. Therefore, the vaporized solvent can be discharged to the outside of the mold 60.

[0091] The constant pressure applied to the mold 60 is set so that the heat-insulating material 21, which is a pressure-molded body, has a desired degree of flatness. Furthermore, the constant pressure applied to the mold 60 is set so that a desired void 33 is formed in the heat-insulating material 21, which is a pressure-molded body. In other words, the void ratio can be adjusted by adjusting the constant pressure.

[0092] For example, if the average particle diameter of the inorganic particles 31 is between 30 μm and 150 μm, the constant pressure should be, for example, between 0.1 MPa and 2.0 MPa. This allows the desired flatness to be obtained, as described above. For example, the variation in the thickness of the spacer 4 can be kept within 10%. Furthermore, the porosity can be set to 1 to 50%. In order to have the desired flatness while keeping the porosity at 20% or less, the pressure should be, for example, between 5 kPa and 100 kPa. However, the constant pressure should also be adjusted depending on the type of binder 32.

[0093] Furthermore, if the binder 32 is polyethylene oxide and the solvent is water, the temperature of the mold 60 should be, for example, 110°C to 240°C. The time for applying a constant pressure in the molding process S3 should be, for example, 1 minute to 12 hours. This allows the water solvent to vaporize and the inorganic particles 31 to bond together with the binder 32.

[0094] As shown in Figure 5, after the molding process S3, the pressure-molded body is covered with the outer cover 22 in the covering process S4. In this way, the outer surface of the heat insulating material 21 is covered with the inner cover 23, and then the outer surface of the inner cover 23 is covered with the outer cover 22, thereby completing the spacer 4.

[0095] 5. Effects of the manufacturing method of spacer 4 According to this manufacturing method, in the molding process S3, by applying a constant pressure to the mold 60, the flatness of the surface of the spacer 4 including the press-molded body can be increased. Therefore, variations in the surface pressure distribution of the battery cell 3 can be suppressed, and thus the deterioration of the battery cell 3 can be suppressed. Furthermore, the thermal insulation material 21 has a desired porosity, and the inorganic particles 31 can be bound together by the binder 32. As a result, the thermal insulation material 21 can have desired thermal insulation properties and elastic properties.

[0096] 6. Others In Embodiment 1, a fluid 41 was prepared by mixing the binder 32 and the solvent, and then stirred with the inorganic particle material 131. Alternatively, the inorganic particle material 131, binder 32, and solvent may be stirred simultaneously. However, by preparing the fluid 41 first, the binder 32 can be evenly coated onto the surface of the inorganic particle material 131.

[0097] In Embodiment 1, the molding process S3 involved molding the composition 42 and the inner cover 23 using a mold 60. Alternatively, the molding process S3 could involve molding only the composition 42. [Explanation of symbols]

[0098] 3 battery cells 4 Spacers 31 Inorganic particles 32 Binding agent 33 void 41 Fluids 42 Composition 60 mold 60a,60b,60c molding surface 131 Inorganic particle material S1 Composition generation process S2 placement process S3 Molding process

Claims

1. A method for manufacturing a spacer that is positioned opposite a battery cell, the spacer having a pressure-molded body containing a plurality of inorganic particles, A composition production step that produces a composition in which the surfaces of a plurality of inorganic particles are coated with a fluid in which a binder is dissolved or dispersed by a solvent, A placement step of placing the composition in a mold, A method for manufacturing a spacer, comprising: a molding step, after the arrangement step, applying a certain amount of pressure to the mold and vaporizing the solvent to form the pressurized molded body in which the inorganic particles are bound together by the binder;

2. The method for manufacturing a spacer according to claim 1, wherein in the molding step, the solvent is vaporized by applying a temperature to the mold that is equal to or greater than the melting point of the binder, or by reducing the internal pressure in a region within the molding surface of the mold.

3. The method for manufacturing a spacer according to claim 1, wherein in the molding step, the vaporized solvent is discharged to the outside from a region within the molding surface of the mold.

4. The pressure-molded body includes voids between the plurality of inorganic particles, The method for manufacturing a spacer according to claim 1, wherein the constant applied pressure is set to form the gap.

5. The method for manufacturing a spacer according to claim 4, wherein the porosity of the pressure-molded body is 20% or less.

6. The method for manufacturing a spacer according to claim 1, wherein in the arrangement step, the composition covered with a cover made of a nonwoven fabric or a woven fabric is placed in the mold.

7. The method for manufacturing a spacer according to claim 1, wherein the inorganic particles consist of a porous structure.

8. The method for manufacturing a spacer according to claim 7, wherein the inorganic particles consist of silica aerogel.

9. The average particle diameter of the inorganic particles is 30 μm or more and 150 μm or less. The method for manufacturing a spacer according to claim 8, wherein the constant pressing force is 0.1 MPa or more and 2.0 MPa or less.

10. The method for manufacturing a spacer according to claim 1, wherein the binder is made of a viscoelastic material.

11. The method for manufacturing a spacer according to claim 10, wherein the binder includes polyethylene oxide.

12. The aforementioned binder is a water-soluble material. The method for manufacturing a spacer according to claim 1, wherein the solvent includes water.

13. In the above composition production step, By mixing at least the binder and the solvent, a fluid is produced in which the binder is dissolved or dispersed by the solvent. The method for producing a spacer according to claim 1, further comprising stirring the fluid and the plurality of inorganic particles to produce the composition.

14. In the composition production step, the inorganic particle material, the binder, and the solvent are stirred to pulverize the inorganic particle material to obtain inorganic particles of different shapes and sizes, and to produce the composition. The method for manufacturing a spacer according to claim 1, wherein the pressure-molded body has particles of different shapes and sizes randomly stacked on top of each other.

Images