JP2011204589A - Battery case, manufacturing method therefor, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery case which is superior in moisture permeability resistance and pressure resistance.SOLUTION: The case body constituted of a stainless steel plate and a sealed body composed of the stainless steel plate are sealed airtightly by a mold body of thermoplastic resin composition of which mold shrinkage is 0.8% or less. For the case body and the sealed body, a pit is respectively formed in 65 area% or more of a face jointed with the mold body of the thermoplastic resin composition. Moreover, for 35 number% or more of the pit formed in the jointed face, a ratio D/Dof the maximum diameter Dinside the pit, with respect to the diameter Dof a pit opening part is 1.1 or more.

Description

  The present invention relates to a battery case, a manufacturing method thereof, and a secondary battery.

  Secondary batteries such as lithium-ion batteries, nickel-cadmium batteries, and nickel-hydrogen batteries are widely used in electronic devices or electronic parts such as mobile phones, notebook personal computers, video cameras, electric vehicles, satellites, and social infrastructure components. Has been. In particular, a lithium ion battery using a non-aqueous electrolyte is excellent in energy density and output characteristics, and is therefore widely used in mobile phones and mobile devices that are required to be small and light.

  Secondary batteries are classified into cylindrical types, square types, laminate types, and the like depending on the shape of the battery case. Although each type of battery case is different in shape, it is common in that two or more members (for example, a case main body and a sealing body) are hermetically sealed.

  In a secondary battery using a non-aqueous electrolyte, when the non-aqueous electrolyte comes in contact with moisture that has entered from the outside, the non-aqueous electrolyte itself is not only deteriorated but also metal is generated due to the generation of acid. The battery case made of metal will corrode. Therefore, moisture permeation resistance is required for the joint portion of the battery case of the secondary battery.

  In addition, the secondary battery has a risk that the internal pressure abnormally increases depending on the storage environment and usage conditions, and the battery explodes. Therefore, the battery case of the secondary battery is provided with an explosion-proof valve that operates when the internal pressure rises abnormally. Therefore, the junction of the battery case of the secondary battery is required to have a pressure resistance that does not break even when the internal pressure at which the explosion-proof valve operates is reached.

  As described above, the joint portion of the battery case is required to have moisture permeation resistance and pressure resistance. In order to satisfy these requirements, various methods have been proposed as a sealing method for a battery case of a secondary battery (see, for example, Patent Documents 1 and 2).

  In Patent Document 1, a tube expansion cylindrical portion is provided at an opening end portion of a base cylindrical portion of a bottomed cylindrical metal case, a plastic lid is fitted into the tube expansion cylindrical portion of the metal case, and the opening end portion of the metal case is curled. Thus, a method for sealing a battery case is described.

  In Patent Document 2, an annular support portion is provided on a bottomed cylindrical battery case, a sealing body is placed on the annular support portion of the battery case, and the opening edge of the battery case is caulked inside. The method of sealing the battery case is described.

JP 2000-30675 A JP 2008-66048 A

  When the above conventional sealing methods are insufficient in moisture permeation depending on the usage environment of the secondary battery, such as when exposed to high-temperature and high-humidity environments or when exposed to environments that are susceptible to condensation due to rapid cooling and heating. There is.

  The present invention has been made in view of such points, and an object thereof is to provide a battery case that is superior in moisture permeation resistance and pressure resistance.

  The present inventor solves the above-mentioned problem by airtightly sealing the case body and the sealing body by an injection molding method using a thermoplastic resin composition after roughening the surface of the case body and the sealing body. The present invention was completed by finding out what can be done and further studying it.

That is, the first of the present invention relates to the following battery case.
[1] A case body made of a metal plate; a sealing body made of a metal plate that seals the opening of the case body; and the case body and the sealing body joined to the case body and the sealing body. A molded body of a thermoplastic resin composition that is hermetically sealed; each of the case body and the sealing body has pits formed in 65% by area or more of a joint surface with the molded body of the thermoplastic resin composition. In each of the case body and the sealing body, 35% or more of pits formed on the joint surface with the molded body of the thermoplastic resin composition have a pit opening diameter D _2. A battery case in which the ratio D ₁ / D ₂ of the maximum diameter D ₁ inside the pit to 1.1 is 1.1 or more; and the molding shrinkage of the thermoplastic resin composition is 0.8% or less.
[2] The battery case according to [1], wherein the metal plate constituting the case body and the sealing body is a stainless steel plate.
[3] The thermoplastic resin composition includes polypropylene resin, polybutylene terephthalate resin, tetrafluoroethylene-perfluoroalkyl vinyl ether resin, polycarbonate resin, acrylonitrile-butadiene-styrene resin, polyacetal resin and polyphenylene sulfide. The battery case according to [1] or [2], including one or more thermoplastic resins selected from the group consisting of a resin.

The second of the present invention relates to the following battery case manufacturing method.
[4] A step of preparing a case body made of a metal plate and a sealing body made of a metal plate; a step of installing the case body and the sealing body in an injection mold; and a thermoplastic resin in the injection mold Injecting the composition, joining the molded body of the thermoplastic resin composition to the case body and the sealing body, and hermetically sealing the case body and the sealing body; And the sealing body has pits formed in 65% by area or more of the joint surface with the molded body of the thermoplastic resin composition; and the thermoplastic resin composition in each of the case body and the sealing body. 35% by number or more pits of the pits formed at the interface between the molded body of the object, the ratio D _{1 /} D ₂ of the maximum diameter D ₁ of the pit internal to the diameter D ₂ of the pit openings There .1 above; molding shrinkage of the thermoplastic resin composition is not more than 0.8%, the manufacturing method of the battery case.
[5] The battery case manufacturing method according to [4], wherein the metal plate constituting the case body and the sealing body is a stainless steel plate.
[6] The pit formed on the joint surface of the case body and the sealing body is formed by bringing the metal plate into contact with an aqueous solution containing Fe ³⁺ , according to [4] or [5]. A battery case manufacturing method.
[7] The battery case manufacturing method according to [6], wherein the aqueous solution is a ferric chloride aqueous solution.
[8] The thermoplastic resin composition includes polypropylene resin, polybutylene terephthalate resin, tetrafluoroethylene-perfluoroalkyl vinyl ether resin, polycarbonate resin, acrylonitrile-butadiene-styrene resin, polyacetal resin and polyphenylene sulfide. The manufacturing method of the battery case as described in any one of [4]-[7] containing 1 or more types of thermoplastic resins selected from the group which consists of a resin.

The third aspect of the present invention relates to the following secondary battery.
[9] A secondary battery having the battery case according to any one of [1] to [3].

  According to the present invention, a battery case excellent in moisture permeation resistance and pressure resistance can be easily manufactured. Further, according to the present invention, it is possible to provide a secondary battery that can be used for a longer period of time and more safely.

Sectional schematic diagram which shows the structure of the battery case of Embodiment 1. Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 1. FIG. Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 1. FIG. Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 1. FIG. Sectional schematic diagram showing the configuration of the battery case of the second embodiment Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 2. FIG. Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 2. FIG. Sectional schematic diagram for demonstrating the manufacturing method of the battery case of Embodiment 2. FIG. Photograph of surface of roughened stainless steel sheet Photograph of cross section of roughened stainless steel sheet Enlarged photo of area A shown in FIG. Sectional schematic diagram showing the configuration of the battery case fabricated in Example 1 Sectional schematic diagram showing the configuration of the battery case fabricated in Example 1 Sectional schematic diagram showing the configuration of the battery case produced in Example 2 Sectional schematic diagram showing the configuration of the battery case produced in Example 2

1. Battery Case The battery case of the present invention has a case body, a sealing body, and a molded body of a thermoplastic resin composition. The molded body of the thermoplastic resin composition is bonded to the case body and the sealing body, respectively, and the case body and the sealing body are hermetically sealed by the molded body of the thermoplastic resin composition.

  In this specification, the area | region joined with the molded object of a thermoplastic resin composition among the surfaces of a case main body and a sealing body is called "joint surface." Moreover, the area | region which mutually opposes in the junction part of a case main body and a sealing body among the surfaces of a case main body and a sealing body is called "opposing surface." Usually, the joining surface of the case body is located on the back side of the facing surface of the case body, and the joining surface of the sealing body is located on the back side of the facing surface of the sealing body.

(1) Case main body and sealing body The case main body has an accommodating portion for accommodating a battery element (a positive electrode, a negative electrode, a separator, etc.), an electrolytic solution, and the like. This accommodating portion is open to the outside and is closed by a sealing body. From the viewpoint of improving moisture permeation resistance of the battery case, at the joint portion between the case body and the sealing body, the facing surface of the case body and the facing surface of the sealing body are in contact with each other without any gaps, or are joined through an adhesive layer. It is preferable.

  The shape of the battery case of the present invention is not particularly limited, such as a cylindrical shape or a rectangular tube shape. The shape of the case body can be appropriately selected according to the shape of the battery case. For example, examples of the shape of the case main body include a bottomed cylindrical shape having a flange portion (see Embodiment 1) and a bottomed cylindrical shape having a stepped portion (see Embodiment 2). The shape of the sealing body is not particularly limited as long as it can seal the opening of the case main body, and may be appropriately set according to the shape of the case main body.

  The case main body and the sealing body are formed by molding a metal plate. The type of the metal plate is not particularly limited, but a stainless steel plate is preferable from the viewpoint of forming a pit having an overhang portion (described later). The steel type of the stainless steel sheet is not particularly limited, such as austenite, ferrite, and martensite. Examples of the steel type of the stainless steel plate include SUS304, SUS430, and SUS316. Further, the type of surface finish of the stainless steel plate is not particularly limited. Examples of types of surface finish include BA, 2B, 2D, No. 4, HL, and the like.

  A plurality of pits are formed on the joint surfaces of the metal plates constituting the case body and the sealing body. In the battery case of the present invention, the thermoplastic resin composition enters the pits on the joint surface between the case body and the sealing body. As a result, the molded body of the thermoplastic resin composition adheres firmly to the case body and the sealing body, and hermetically seals the case body and the sealing body.

  In the joint surface of the case body and the sealing body, the area ratio of the pit forming portion is preferably 65 area% or more, more preferably 80 area% or more, and a state in which pits are formed substantially without gaps (almost 100 area%). Is particularly preferred. When the area ratio of the pit formation portion is less than 65 area%, a sufficient anchor effect cannot be obtained, and the adhesion of the thermoplastic resin composition to the molded body cannot be sufficiently improved. As a result, moisture permeability resistance and pressure resistance may be insufficient.

  The area ratio of the pit forming portion can be measured by observing the joint surface using a laser shape measuring microscope and obtaining the area of a part having a depth of 0.5 μm or more and the area of another part. An example of an electron microscope (SEM) photograph obtained by imaging the surface of a stainless steel plate having pits from above is shown in FIG.

At least some of the plurality of pits formed on the joint surface are pits having an overhang portion. In this specification, “pit having an overhang portion” means a pit having D ₁ / D ₂ of 1.1 or more when the maximum diameter inside the pit is D ₁ and the diameter of the pit opening is D _2. (See FIG. 11). The diameter of the pit can be measured by observing an electron microscope (SEM) photograph of a cross section of the joint surface of the case body. An example of an electron microscope (SEM) photograph obtained by imaging a cross section of a stainless steel plate on which pits having an overhang portion are formed is shown in FIG.

The ratio of the number of pits having overhang portions (pits having D ₁ / D ₂ of 1.1 or more) to the number of pits formed on the joint surface is preferably 35% by number or more. A pit having an overhang portion exhibits a more excellent anchor effect than a pit having no overhang portion. Therefore, when the ratio of the number of pits having an overhang portion is 35% by number or more, the adhesion between the thermoplastic resin composition and the molded body can be further improved. As a result, it is possible to prevent moisture from entering from the interface between the metal plate and the thermoplastic resin composition, and to improve moisture permeability resistance. Moreover, when the ratio of the number of pits having an overhang portion is 35% by number or more, the bonding strength of the thermoplastic resin composition is increased, so that the pressure resistance can be improved. On the other hand, if the ratio of the number of pits having an overhang portion is less than 35% by number, the adhesion of the thermoplastic resin composition to the molded body cannot be sufficiently improved, so that the moisture permeation resistance and pressure resistance are high. It may be insufficient.

The ratio of the number of pits having an overhang portion is determined by observing an electron microscope (SEM) photograph of the cross section of the joint surface, and the number of pits having D ₁ / D ₂ of 1.1 or more and other pits It can be confirmed by measuring the number of.

  The metal plate constituting the case body and the sealing body may have pits formed only on the joint surface with the molded body of the thermoplastic resin composition, or pits on surfaces other than the joint surface (for example, the entire surface). May be formed.

  The metal plate constituting the case main body and the sealing body may be covered with a resin composition or the like. However, the metal base is exposed at least on the joint surface with the molded body of the thermoplastic resin composition, and the metal base having pits and the molded body of the thermoplastic resin composition must be in direct contact.

  The case body and the sealing body may be provided with electrode terminals, explosion-proof valves, and the like. As will be described later, the explosion-proof valve is not necessary when the joined portion of the thermoplastic resin composition is made to function as an explosion-proof valve.

(2) Molded body of thermoplastic resin composition The molded body of the thermoplastic resin composition is tightly adhered to the joint surface of the case body and the joint surface of the sealing body, and hermetically seals the case body and the sealing body. . As described above, the joining surface of the case body is usually located on the back side of the facing surface of the case body, and the joining surface of the sealing body is located on the back side of the facing surface of the sealing body.

  The thermoplastic resin composition constituting the molded body of the thermoplastic resin composition may contain either a crystalline thermoplastic resin or an amorphous thermoplastic resin, but has excellent crystallinity due to moisture permeation resistance. It is preferable that the thermoplastic resin is included. Examples of thermoplastic resins that can be used include polypropylene resins, polybutylene terephthalate resins, tetrafluoroethylene-perfluoroalkyl vinyl ether resins, polycarbonate resins, acrylonitrile-butadiene-styrene resins, polyacetal resins and polyphenylene sulfide resins. Resin etc. are included.

  The molding shrinkage of the thermoplastic resin composition is preferably 0.8% or less. When the molding shrinkage ratio exceeds 0.8%, the thermoplastic resin composition that has entered the pits on the joint surface during injection molding may shrink more than the diameter of the pit openings. As a result, a gap is generated at the interface between the metal plate and the thermoplastic resin composition, which may result in insufficient moisture permeation resistance and pressure resistance.

  The molding shrinkage rate of the thermoplastic resin composition was determined by measuring the volume B of the resin composition solidified after injection molding with respect to the volume A of the resin inflow portion of the mold used at the time of injection molding, and “(A−B) / A × 100 (%) ”.

  The molding shrinkage of the thermoplastic resin composition can be adjusted depending on the type of resin, but can also be adjusted by adding a filler, for example. Examples of fillers include fiber fillers such as glass fiber, carbon fiber, and aramid resin; carbon black, calcium carbonate, calcium silicate, magnesium carbonate, silica, talc, glass, clay, lignin, mica, quartz powder, glass sphere Powder fillers such as: pulverized carbon fiber or aramid fiber. Among these fillers, when a filler that does not transmit moisture such as glass fiber is added, the moisture permeation resistance can be further improved. The filler content in the thermoplastic resin composition is preferably in the range of 5 to 60% by mass, more preferably in the range of 10 to 40% by mass.

  The molding shrinkage rate of the thermoplastic resin composition can also be adjusted by mixing a crystalline resin and an amorphous resin. In general, a crystalline resin has a larger molding shrinkage ratio than an amorphous resin. Therefore, if the mixing ratio of the amorphous resin is increased, the molding shrinkage ratio can be reduced.

  The breaking strength (pressure resistance) of the battery case of the present invention is determined by the type of the thermoplastic resin composition constituting the molded article of the thermoplastic resin composition, the thickness of the molded article of the thermoplastic resin composition, and the like. For example, the breaking strength of the battery case of the present invention may be about 0.5 to 1.5 MPa. When an explosion-proof valve is provided in a battery case as in a conventional battery case, the molded body of the thermoplastic resin composition (joint part of the battery case) has a breaking strength that does not break even when the explosion-proof valve operates at an internal pressure ( Pressure resistance) is required. On the other hand, in the battery case of the present invention, instead of providing an explosion-proof valve in the battery case, a molded body (joint part of the battery case) of the thermoplastic resin composition may function as an explosion-proof valve. That is, the battery case may be broken before the battery case explodes by intentionally lowering the breaking strength (pressure resistance) of the molded body of the thermoplastic resin composition. By doing in this way, since it becomes unnecessary to provide an explosion-proof valve, a battery case can be manufactured at lower cost.

  As described above, in the battery case of the present invention, 1) the facing surface of the case body and the facing surface of the sealing body are joined, and 2) the molded body of the thermoplastic resin composition is joined to the joining surface and the sealing body of the case body. The case main body and the sealing body are tightly hermetically sealed by firmly adhering to the joint surface and completely covering the joint portion of the case main body and the sealing body. Therefore, the battery case of the present invention has excellent moisture permeation resistance and pressure resistance.

  Although the battery case of this invention is not specifically limited, For example, it can be manufactured with the following method.

2. Battery Case Manufacturing Method The battery case manufacturing method of the present invention includes 1) a first step for preparing a case body and a sealing body, and 2) a second step for installing the case body and the sealing body in an injection mold. And 3) a third step of injecting the thermoplastic resin composition into an injection mold and hermetically sealing the case main body and the sealing body.

  In the first step, a case body and a sealing body are prepared.

As described above, the shapes of the case main body and the sealing body are not particularly limited, but pits are formed so as to satisfy the following two conditions at the joint surface of the case main body and the sealing body.
A) Pits are formed in 65 area% or more of the portion to be the joint surface.
B) Of the pits formed on the joint surface, 35% or more of pits have a ratio D ₁ / D ₂ of the maximum diameter D ₁ inside the pit to the diameter D ₂ of the pit opening of 1.1 or more. It is.

  These pits may be formed before the metal plate is molded or may be formed after the molding process. That is, the roughened metal plate may be molded to produce the case main body and the sealing body, or may be roughened after the case main body and the sealing body are molded. Further, the pits may be formed on the entire surface of the case main body and the sealing body, or may be formed only on a portion serving as a joint surface.

In order to form a pit having an overhang portion on the surface of the metal plate, an aqueous solution containing Fe ³⁺ ions may be brought into contact with the surface where the pit is to be formed. The aqueous solution containing Fe ³⁺ ions is preferably a ferric chloride (FeCl ₃ ) aqueous solution.

To a method of forming a pit having an overhang portion on the surface of the metal plate, a) a method of immersing the metal plate in an aqueous solution containing Fe ³⁺ ions (immersion method) and, b) an aqueous solution containing a metal plate Fe ³⁺ ions Among them, there is a method of alternating electrolysis (alternative electrolytic method). In the following description, the dipping method of a) will be described. The alternating electrolysis method b) is described in JP-A-10-259499, JP-A-2002-106718, and the like.

In the dipping method, the metal plate is immersed in an aqueous solution containing Fe ³⁺ ions to form a plurality of pits having overhang portions on the surface of the metal plate. Since a stainless steel plate is preferable as the metal plate, the following description will be made on the case where a stainless steel plate is used as the metal plate. In addition, the steel type of the stainless steel plate immersed in the treatment liquid is not particularly limited, such as austenitic, ferritic, and martensitic. Further, the type of surface finish of the stainless steel plate is not particularly limited.

As described above, the aqueous solution in which the stainless steel plate is immersed is preferably an aqueous ferric chloride solution. The ferric chloride in the aqueous solution forms pits on the surface of the stainless steel plate by the pitting corrosion action starting from the adsorbed portion of Cl ⁻ ions. The concentration of ferric chloride in the aqueous solution is preferably within the range of 0.1 to 3.0 mol / L. When the ferric chloride concentration is less than 0.1 mol / L, pits having a sufficient depth cannot be formed on the surface of the stainless steel plate. On the other hand, even if the ferric chloride concentration exceeds 3.0 mol / L, an increase in the number of pits corresponding to the increase in the ferric chloride concentration is not observed.

Moreover, the aqueous solution which immerses a stainless steel plate may contain the oxidizing compound further. As described above, when a stainless steel plate is immersed in a ferric chloride aqueous solution, a plurality of pits having an overhang portion are formed on the surface of the stainless steel plate by the pitting corrosion action of Cl 2 ⁻ ions derived from ferric chloride. However, depending on the steel type of the stainless steel plate and the type of surface finish, melting of the entire stainless steel plate occurs and the pit opening (overhang portion) also melts, so it may be difficult to form a pit having an overhang portion. . For example, SUS430 has a lower immersion potential in an aqueous ferric chloride solution than SUS304, and the surface of the stainless steel plate is easily dissolved as a whole. Therefore, even if SUS430 is immersed in a ferric chloride aqueous solution, the dissolution of the pit opening also proceeds in parallel with the formation of the pits. Therefore, the ratio of pits having an overhang portion among the formed pits is 35. May be less than a few percent. In such a case, a pit having an overhang portion can be formed by adding an oxidizing compound to the ferric chloride aqueous solution regardless of the type of stainless steel or the type of surface finish.

The oxidizing compound increases the thickness of the oxide film (passive film) on the surface of the stainless steel plate and suppresses dissolution on the surface of the stainless steel plate. As described above, the pits are formed by pitting corrosion starting from the Cl ⁻ ion adsorption portion. In the pitting portion (inside the pit), Cl ⁻ ions are concentrated and the pH is locally lowered, so that etching proceeds. On the other hand, since the surface of the stainless steel plate is oxidized when Fe ³⁺ in the aqueous solution is reduced to Fe ²⁺ , the portion where the Cl ⁻ ions on the stainless steel plate surface are not adsorbed is protected. Since the oxidizing compound oxidizes Fe ²⁺ to Fe ³⁺ and oxidizes the surface of the stainless steel plate, the passive film can be further strengthened as compared with the case of using a ferric chloride aqueous solution alone.

By adding an oxidizing compound to the aqueous solution in which the stainless steel plate is immersed, regardless of the type of steel plate or surface finish of the stainless steel plate, the dissolution of the pit opening is suppressed, making it easier to create a pit with an overhang. Can be formed. Further, since the oxidizing compound has an action of oxidizing Fe ²⁺ generated in the aqueous solution by the immersion treatment to Fe ³⁺ , a precipitate made of iron hydroxide (III) / Fe (OH) ₃ generated by hydrolysis of the aqueous solution. Suppresses the occurrence of By suppressing the generation of precipitates in this way, the stability of the aqueous solution is improved, and as a result, continuous processability can be improved.

The kind of the oxidizing compound is not particularly limited as long as it can increase the thickness of the oxide film on the surface of the stainless steel plate to such an extent that the dissolution of the surface of the stainless steel plate by the ferric chloride aqueous solution can be suppressed. Examples of such oxidizing compounds include permanganates such as potassium permanganate (KMnO ₄ ); potassium dichromate (K ₂ Cr ₂ O ₇ ) and chromic acid (VI) (CrO ₃ ). Chromates; nitric acids such as nitric acid (HNO ₃ ) and potassium nitrate (KNO ₃ ); peroxides such as hydrogen peroxide (H ₂ O ₂ ) and sodium peroxide (Na ₂ O ₂ ); sulfuric acid (H ₂ SO ₄ ) and other sulfuric acids.

  According to the experiments by the present inventors, any of the above oxidizing compounds was effective in suppressing dissolution of the stainless steel plate surface. Among these oxidizing compounds, potassium permanganate and potassium dichromate have a large oxidizing action but are difficult to use because of low solubility and difficulty in preparing an aqueous solution. On the other hand, nitric acid, hydrogen peroxide solution, and sulfuric acid are easy to use because they are aqueous solutions from the beginning. Among nitric acid, hydrogen peroxide solution and sulfuric acid, nitric acid having the strongest oxidizing power (many electron exchange) is preferable.

The molar ratio of the oxidizing compound (for example, nitric acid) to Fe in the aqueous solution is preferably within the range of 0.5 to 3.0. When the molar ratio is less than 0.5, the thickness of the oxide film (passive film) on the surface of the stainless steel plate cannot be increased sufficiently, and precipitation consisting of iron (III) hydroxide / Fe (OH) ₃ The generation of objects cannot be sufficiently suppressed. On the other hand, even if the molar ratio exceeds 3.0, an increase in the thickness of the oxide film that is commensurate with the increase in the concentration of the oxidizing compound is not observed.

  The liquid temperature of the aqueous solution is preferably in the range of room temperature to 95 ° C, and more preferably in the range of room temperature to 60 ° C. This is because when the liquid temperature is high, the evaporation of the treatment liquid becomes remarkable.

  The time for immersing the stainless steel plate in the aqueous solution is preferably 120 seconds or less. When the immersion time exceeds 120 seconds, the diameter of the formed pits becomes excessively large and the anchor effect is lowered. Moreover, since the remarkable improvement of an anchor effect is not recognized even if it processes for 60 seconds or more, it is more preferable that immersion time shall be 60 seconds or less. On the other hand, since the immersion treatment for 1 second or less is difficult to control, the immersion time is preferably 2 seconds or more.

By immersing the stainless steel plate in an aqueous solution containing Fe ³⁺ ions, a large number of pits having an overhang portion can be formed on the surface of the stainless steel plate. In addition, when it is desired to form pits only on a part of the stainless steel plate (for example, a part to be a bonding surface), the stainless steel plate may be immersed in an aqueous solution after masking a portion where pits are not to be formed. The same effect can be obtained by applying an aqueous solution to the surface of the stainless steel plate instead of immersing the stainless steel plate in the aqueous solution.

  In the second step, the case body and the sealing body are placed in an injection mold. At this time, a sealing body is arrange | positioned so that the opening part of a case main body may be sealed. In addition, the case body and the sealing body are placed in the injection mold so that the portion serving as the joint surface between the case body and the sealing body can come into contact with the thermoplastic resin composition.

  In the third step, the high temperature thermoplastic resin composition is injected into the injection mold at high pressure, and the molded body of the thermoplastic resin composition is bonded to the bonding surfaces of the case body and the sealing body.

  A plurality of pits having an overhang portion are formed on the joint surface of the case body and the sealing body. Since the high-temperature thermoplastic resin composition enters the inside of the pit formed on the joint surface of the case body and the sealing body, the molded body of the thermoplastic resin composition is firmly attached to the joint surface of the case body and the sealing body. To do. As a result, the case body and the sealing body are hermetically sealed by the molded body of the thermoplastic resin composition.

  The temperature of the injection mold is preferably near the melting point of the resin used. This is because the injected thermoplastic resin composition easily penetrates into the pits of the roughened stainless steel plate. Moreover, it is preferable to provide a gas vent in the injection mold so that the thermoplastic resin composition flows smoothly.

  After the injection is completed, the battery case in which the case main body and the sealing body are hermetically sealed can be obtained by opening the mold and releasing the mold. Thereafter, the molded article of the thermoplastic resin composition may be further annealed to eliminate internal distortion due to molding shrinkage.

  By the above procedure, the battery case of the present invention can be manufactured by firmly sealing the case main body and the sealing body with the molded body of the thermoplastic resin composition.

3. Secondary battery The secondary battery of the present invention has the battery case of the present invention. A battery element (a positive electrode, a negative electrode, a separator, etc.), an electrolytic solution, and the like are accommodated inside the battery case. The shape of the secondary battery is not particularly limited, such as a cylindrical shape or a rectangular tube shape. The type of secondary battery is not particularly limited, such as a lithium ion battery, a lithium polymer battery, a nickel metal hydride battery, or a nickel cadmium battery.

  In order to manufacture the secondary battery of the present invention, for example, 1) a battery element (a positive electrode, a negative electrode, a separator, etc.) or an electrolyte is accommodated in the case body, and 2) a sealing body is formed in the opening of the case body 3) The molded body of the thermoplastic resin composition is bonded to the bonding surface of the case main body and the bonding surface of the sealing body, and the case main body and the sealing body are hermetically sealed (the battery of the present invention described above). (See Case Manufacturing Method).

  Hereinafter, the battery case of the present invention will be described in more detail with reference to the drawings.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view showing the configuration of the battery case according to Embodiment 1 of the present invention. As shown in FIG. 1, the battery case 100 of the first embodiment has a case main body 110, a sealing body 120, and a molded body 130 of a thermoplastic resin composition.

  The case main body 110 has a flange portion 112 and a housing portion 114, and has a bottomed cylindrical shape. The case body 110 is formed by forming a stainless steel plate. When a secondary battery is manufactured using the battery case 100 of Embodiment 1, a battery element (a positive electrode, a negative electrode, a separator, or the like), an electrolytic solution, or the like is housed in the housing portion 114.

  Sealing body 120 is a disk-shaped stainless steel plate disposed on flange portion 112 of the case body so as to close the opening of case body 110. The sealing body 120 is in contact with the flange portion 112 of the case main body without a gap, and blocks the housing portion 114 of the case main body from the outside.

  The molded body 130 of the thermoplastic resin composition is a molded body of a thermoplastic resin composition having a molding shrinkage rate of 0.8% or less, and is bonded to the bonding surface 116 of the case body and the bonding surface 122 of the sealing body, The case main body 110 and the sealing body 120 are hermetically sealed. As shown in FIG. 1, in the present embodiment, the lower surface of the flange portion 112 of the case body serves as the joint surface 116 of the case body, and the upper surface of the peripheral portion of the sealing body 120 serves as the joint surface 122 of the sealing body.

  A plurality of pits are formed on the joint surface 116 of the case body and the joint surface 122 of the sealing body. In these joining surfaces 116 and 122, the area ratio of the pit forming portion is 65 area% or more. In addition, 35% by number or more of the pits formed on the joint surfaces 116 and 122 are pits having an overhang portion. The molded body 130 of the thermoplastic resin composition is in close contact with each of the case main body 110 and the sealing body 120 by entering the inside of many pits having these overhang portions.

  The battery case 100 of the present embodiment is excellent in moisture permeation resistance and pressure resistance because the molded body 130 of the thermoplastic resin composition is firmly joined to the case body 110 and the sealing body 120 without any gaps. Yes.

  Hereinafter, a method for manufacturing battery case 100 of the first embodiment will be described with reference to FIGS.

  First, as shown in FIG. 2, a case main body 110 and a sealing body 120 are prepared. The case main body 110 and the sealing body 120 are obtained by forming a stainless steel plate, and pits having an overhang portion are formed in portions that become the joining surfaces 116 and 122. In order to form a pit having an overhang portion, for example, an aqueous ferric chloride solution may be brought into contact with the surface on which the pit is to be formed.

  Next, as shown in FIG. 3, the case main body 110 and the sealing body 120 are placed in the injection mold 140 so that the flange portion 112 of the case main body and the peripheral edge portion of the sealing body 120 are disposed in the resin inflow portion 142. Set to.

  Next, as shown in FIG. 4, the thermoplastic resin composition is injected into the resin inflow portion 142 from the resin injection port 144 of the injection mold, and the molded body 130 of the thermoplastic resin composition is attached to the case body. The flange part 112 and the peripheral part of the sealing body 120 are joined.

  Through the above procedure, the battery case 100 (see FIG. 1) of the present embodiment in which the case main body 110 and the sealing body 120 are hermetically sealed by the molded body 130 of the thermoplastic resin composition can be manufactured.

[Embodiment 2]
FIG. 5 is a schematic cross-sectional view showing the configuration of the battery case according to the second embodiment of the present invention. As shown in FIG. 5, the battery case 200 of the second embodiment includes a case main body 210, a sealing body 220, and a molded body 230 of a thermoplastic resin composition.

  The case main body 210 has a stepped portion 212 and a storage portion 214 formed by necking, and has a bottomed cylindrical shape. The case body 210 is formed by forming a stainless steel plate. When a secondary battery is manufactured using the battery case 200 of Embodiment 2, a battery element (a positive electrode, a negative electrode, a separator, or the like), an electrolytic solution, or the like is stored in the storage portion 214.

  The sealing body 220 is a bottomed cylindrical stainless steel plate disposed on the stepped portion 212 of the case body so as to seal the opening of the case body 210. The sealing body 220 is in contact with a portion above the stepped portion 212 of the case main body without a gap, and shuts off the housing portion 214 of the case main body and the outside world.

  The molded body 230 of the thermoplastic resin composition is a molded body of a thermoplastic resin composition having a molding shrinkage rate of 0.8% or less, and is bonded to the bonding surface 216 of the case body and the bonding surface 222 of the sealing body, The case main body 210 and the sealing body 220 are hermetically sealed. As shown in FIG. 5, in the present embodiment, the outer surface of the portion above the stepped portion 212 of the case body serves as the joint surface 216 of the case body, and the inner side surface of the sealing body 120 serves as the joint surface 222 of the sealing body. It becomes.

  A plurality of pits are formed on the joint surface 216 of the case body and the joint surface 222 of the sealing body. In these joint surfaces 216 and 222, the area ratio of the pit forming portion is 65 area% or more. In addition, 35% by number or more of the pits formed on the joint surfaces 216 and 222 are pits having an overhang portion. The molded body 230 of the thermoplastic resin composition is firmly in close contact with each of the case main body 210 and the sealing body 220 by entering the inside of many pits having these overhang portions.

  The battery case 200 of the present embodiment is excellent in moisture permeation resistance and pressure resistance because the molded body 230 of the thermoplastic resin composition is firmly joined to the case body 210 and the sealing body 220 without any gaps. Yes.

  Hereinafter, a method for manufacturing the battery case 200 of the second embodiment will be described with reference to FIGS.

  First, as shown in FIG. 6, a case main body 210 and a sealing body 220 are prepared. The case main body 210 and the sealing body 220 are obtained by forming a stainless steel plate, and pits having an overhang portion are formed in portions that become the joining surfaces 216 and 222. In order to form a pit having an overhang portion, for example, an aqueous ferric chloride solution may be brought into contact with the surface on which the pit is to be formed.

  Next, as shown in FIG. 7, the case main body 210 and the sealing member are arranged such that the portion 218 above the stepped portion 212 of the case main body and the side surface portion 224 of the sealing member 220 are disposed in the resin inflow portion 242. The body 220 is set in the injection mold 240.

  Next, as shown in FIG. 8, the thermoplastic resin composition is injected into the resin inflow portion 242 from the resin injection port 244 of the injection mold, and the molded body 230 of the thermoplastic resin composition is attached to the case body. It joins to the part above the step part 212, and the side part of the sealing body 220. FIG.

  Through the above procedure, the battery case 200 (see FIG. 5) of the present embodiment in which the case main body 210 and the sealing body 220 are hermetically sealed by the molded body 230 of the thermoplastic resin composition can be manufactured.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Example 1]
Example 1 shows an example in which a roughened stainless steel plate is produced by an alternating electrolysis method, and the battery case of Embodiment 1 is produced.

1. Production of Roughened Stainless Steel Sheet The following four types of stainless steel sheets were prepared as test stainless steel sheets.
Stainless steel plate A: SUS304, 2B finish, plate thickness 0.8mm
Stainless steel plate B: SUS304, HL finish, thickness 0.8mm
Stainless steel plate C: SUS430, 2B finish, plate thickness 0.8mm
Stainless steel plate D: SUS430, HL finish, thickness 0.8mm

After each stainless steel plate (stainless steel plates A to D) is alkaline degreased (pH 12, liquid temperature 60 ° C., immersion time 1 minute), in aqueous ferric chloride solution (Fe ³⁺ concentration: 60 g / L, liquid temperature: 40 ° C.) Then, alternating electrolysis was performed under the conditions shown in Table 1, and pits were formed on the surface of each stainless steel plate.

For each stainless steel plate having been subjected to the roughening treatment (steel Nanba1～21) and untreated stainless steel A (steel No.22), the area ratio of the pits, the maximum internal pit to the diameter D ₂ of the pit openings the ratio _D 1 / _{D 2} of diameter _{D 1} is calculated the ratio of 1.1 or more pits.

  The area ratio of the pits is determined by observing the steel plate surface with a 500 × field of view using a laser shape measurement microscope (OLS1200; Olympus Optical Co., Ltd.) and other parts having a depth of 0.5 μm or more. The binarization process is performed so that the portion having a depth of 0.5 μm or more is colored and the other portions are not colored. And the area ratio of the colored part was calculated | required and it was set as the area ratio of a pit formation part.

Maximum diameter _{D 1} of the inner diameter _{D 2} and pits of the pit openings, FE-SEM; measured by observing at 5000 times the steel sheet section (width 200μm fraction) by using (S-4000 Hitachi High-Technologies Corporation) (See FIG. 11).

Table 2 shows the stainless steel plate types (steel plates Nos. 1 to 22), the types of stainless steel plates, the conditions of alternating electrolysis (treatment No.), the area ratio of the pit forming portion, and the ratio of pit diameters D ₁ / D _2. Indicates the ratio of pits of 1.1 or more.

FIG. 9 is an electron micrograph (SEM image) of the surface of the roughened stainless steel plate No. 2 steel plate. FIG. 10 is an electron micrograph (SEM image) of a cross section of the roughened stainless steel plate of No. 2 steel plate. FIG. 11 is an enlarged photograph of the area A shown in FIG. As shown in these pictures, by the alternating electrolysis in an aqueous solution of ferric chloride, forming pits (see the arrows in FIG. 11) D 1 _/ D ₂ has 1.1 or more of the overhang portion I was able to.

2. Moisture permeation resistance test and pressure resistance test (1) Moisture permeation resistance test Each stainless steel plate (steel plates No. 1 to 22) is subjected to cylindrical drawing and subjected to alkaline degreasing (pH 12, liquid temperature 60 ° C., immersion time 1 minute). Thus, the case main body 110 having the shape shown in FIG. 2 was produced. The conditions of the cylindrical drawing process were as follows: punch diameter: 50 mm, punch shoulder R: 15 mm, die diameter: 54 mm, die shoulder R: 8 mm, punching diameter: 100 mm, drawing height: 20 mm, with oil coating. The width of the flange portion of the case body 110 is 25 mm. Further, the same stainless steel plate (steel plates No. 1 to 22) was punched out to the same size (punching diameter: 100 mm) as the outer edge of the flange portion of the case main body 110 to produce the sealing body 120 having the shape shown in FIG.

As shown in FIG. 3, the case main body 110 and the sealing body 120 were set in the injection mold 140. At this time, 30 mL of clean water was poured into the case body 110. Subsequently, the molten thermoplastic resin composition shown in Table 3 was injected from the resin injection port 144 into the resin inflow portion 142 of the injection mold, and the injected thermoplastic resin composition was solidified. The volume of the resin inflow portion 142 was 10 mm width × 314 mm circumference × 8 mm thickness. The flange part of the case body 110 and the peripheral part of the sealing body 120 are joined to the thermoplastic resin composition in a region having a width of 7 mm. By the above procedure, as shown in FIG. 12, the case main body 110 has clean water 310, and the case main body 110 and the sealing body 120 are hermetically sealed by the molded body 130 of the thermoplastic resin composition. Battery cases (Examples 1 to 16, Comparative Examples 1 to 6) were obtained.

  For each resin shown in Table 3, Novatec PP MA1B (melting point: 170 ° C .; Nippon Polypro Co., Ltd.) was used as the polypropylene. As the polybutylene terephthalate, Duranex 2002 (melting point: 228 ° C .; Polyplastics Co., Ltd.) was used. As the polyphenylene sulfide, Fortron 0220A9 (melting point: 280 ° C .; Polyplastics Co., Ltd.) was used. As the tetrafluoroethylene-perfluoroalkyl vinyl ether, Fluon PFA P-65P (melting point: 310 ° C., Asahi Glass Co., Ltd.) was used. As the polyacetal, TPS-POM NC (melting point: 163 ° C .; Toyo Plastic Seiko Co., Ltd.) was used. For acrylonitrile-butadiene-styrene, Techno ABS130 (melting point: 91 ° C .; Technopolymer Co., Ltd.) was used. As the polycarbonate, Iupilon GS-2030MR2 (melting point 250 ° C .; Mitsubishi Engineering Plastics Co., Ltd.) was used.

  In addition, as Comparative Example 7, a battery case in which the case main body 110 and the sealing body 120 were joined by curling instead of joining with the molded body of the thermoplastic resin composition was also produced.

  The obtained battery cases (Examples 1 to 16 and Comparative Examples 1 to 7) were subjected to a moisture permeation resistance test. Specifically, each battery case is allowed to stand for 240 hours in a thermostat set at 70 ° C., and the change in the weight of the battery case is measured, thereby reducing the amount of clean water in the battery case (= water permeation). Amount) was measured. “◎” when the amount of water permeation (decrease amount of clean water) is 5 mL or less, “◯” when it is more than 5 mL and less than 10 mL, “Δ” when it is 10 mL or more but less than 15 mL, ".

(2) Pressure resistance test Battery cases (Examples 1 to 16 and Comparative Examples 1 to 7) were prepared from each stainless steel plate (steel plates Nos. 1 to 22) in the same procedure as the moisture permeability test. At this time, as shown in FIG. 13, clean water was not poured into the case main body 110, and the air injection pipe 320 was attached to the central portion of the sealing body 120.

  Each battery case (Examples 1-16, Comparative Examples 1-7) obtained was subjected to a pressure resistance test. Specifically, with each battery case immersed in water, air was injected into the battery case through the air injection pipe 320 so that the pressure increase rate was 0.1 MPa / min. Each time the pressure inside the battery case increased by 0.1 MPa, the pressure was maintained for 30 minutes. Experiments until air leakage occurs from the joint (flange) between the case body 110 and the sealing body 120 or the pressure in the battery case reaches 0.6 MPa, and air leakage occurs from the joint (flange). The air pressure was measured. When the air pressure is 0.6 MPa, there is no air leakage, “◎”, when air leakage occurs at 0.5 MPa or more and less than 0.6 MPa, “◯”, when air leakage occurs at 0.4 MPa or more and less than 0.5 MPa, The case where it occurred was evaluated as “Δ”, and the case where air leakage occurred at less than 0.4 MPa was evaluated as “x”.

(3) Results Table 4 shows the results of the moisture permeation resistance test and the pressure resistance test of each battery case (Examples 1 to 16, Comparative Examples 1 to 7).

In the battery cases of Examples 1 to 16, the area ratio of the pit forming portion on the joint surface is 65 area% or more, and the ratio of pit diameters D ₁ / D _{2 on} the joint surface is 1.1 or more is 35. Since it was several percent or more and the molding shrinkage of the thermoplastic resin composition was 0.8% or less, good evaluation was obtained regarding moisture permeability resistance and pressure resistance.

On the other hand, in the battery cases of Comparative Examples 1 to 3, since the molding shrinkage rate of the thermoplastic resin composition was more than 0.8%, good evaluation on moisture permeation resistance and pressure resistance could not be obtained. Further, in the battery case of Comparative Example 4, since the area ratio of the pit formation portion on the joint surface was less than 65 area%, good evaluation on moisture permeation resistance could not be obtained. In the battery case of Comparative Example 5, since the ratio of pits having a pit diameter ratio D ₁ / D ₂ of 1.1 or more at the joint surface is less than 35% by number, the moisture permeability resistance and pressure resistance are well evaluated. It was not obtained.

[Example 2]
Example 2 shows an example in which a roughened stainless steel plate is produced by an alternating electrolysis method, and the battery case of Embodiment 2 is produced.

1. Production of Roughened Stainless Steel Sheet The following two types of stainless steel sheets were prepared as test stainless steel sheets.
Stainless steel plate A: SUS304, 2B finish, plate thickness 0.8mm
Stainless steel plate C: SUS430, 2B finish, plate thickness 0.8mm

Each stainless steel plate (stainless steel plates A and C) is alkaline degreased (pH 12, liquid temperature 60 ° C., immersion time 1 minute), and then in ferric chloride aqueous solution (Fe ³⁺ concentration: 60 g / L, liquid temperature: 40 ° C.) Then, alternating electrolysis was performed under the conditions shown in Table 1 of Example 1 to form pits on the surface of each stainless steel plate.

For each stainless steel plate having been subjected to the roughening treatment (steel Nanba23～30), the area ratio of the pit, the ratio _D 1 / _{D 2} of the maximum diameter _{D 1} of the pit internal to the diameter _{D 2} of the pit openings 1. The ratio of one or more pits was determined.

Table 5 shows the types of stainless steel plates, conditions of alternating electrolysis (treatment No.), area ratios of pit formation portions, and pit diameter ratios D ₁ / D _{2 for} each stainless steel plate (steel plates No. 23 to 30). Indicates the ratio of pits of 1.1 or more.

2. Moisture permeation resistance test and pressure resistance test (1) Moisture permeation resistance test Each stainless steel plate (steel plates No. 23 to 30) is subjected to cylindrical drawing and necking, and alkaline degreasing (pH 12, liquid temperature 60 ° C., immersion time 1) The case body 210 having the shape shown in FIG. 6 was produced. The conditions of the cylindrical drawing were as follows: punch diameter: 50 mm, punch shoulder R: 15 mm, die diameter: 54 mm, die shoulder R: 8 mm, punching diameter: 100 mm, drawing height: 50 mm, and oiling. The necking process was performed by rotating a hydraulic chuck by roll rolling. The width of the portion above the stepped portion 212 of the case body 210 is 15 mm. Further, the same stainless steel plate (steel plates No. 23 to 30) is subjected to cylindrical drawing and subjected to alkaline degreasing (pH 12, liquid temperature 60 ° C., immersion time 1 minute) to produce a sealing body 220 having the shape shown in FIG. did. The conditions of the cylindrical drawing were as follows: punch diameter: 47 mm, punch shoulder R: 15 mm, die diameter: 48 mm, die shoulder R: 8 mm, punching diameter: 98 mm, drawing height: 20 mm, and oiling.

  As shown in FIG. 7, the case main body 210 and the sealing body 220 were set in the injection mold 240. At this time, 30 mL of clean water was put into the case body 210. Next, the molten thermoplastic resin composition shown in Table 3 of Example 1 was injected from the resin injection port 244 into the resin inflow portion 242 of the injection mold, and the injected thermoplastic resin composition was solidified. . The volume of the resin inflow portion 242 was set to width 5.6 mm × circumference 174.6 mm × thickness 2 mm. The portion above the stepped portion 212 of the case body and the side surface portion of the sealing body 220 are joined to the thermoplastic resin composition in a region having a width of 8 mm. With the above procedure, as shown in FIG. 14, the case body 210 has clean water 310, and the case body 210 and the sealing body 220 are hermetically sealed by the molded body 230 of the thermoplastic resin composition. Battery cases (Examples 17 to 24) were obtained.

  The obtained battery case (Examples 17 to 24) was subjected to a moisture permeation resistance test in the same procedure as in Example 1.

(2) Pressure resistance test Battery cases (Examples 17 to 24) were prepared from each stainless steel plate (steel plates No. 23 to 30) in the same procedure as the moisture permeation resistance test. At this time, as shown in FIG. 15, clean water was not poured into the case main body 210, and the air injection pipe 320 was attached to the central portion of the sealing body 220.

  About each obtained battery case (Examples 17-24), the pressure | voltage resistance test was done in the procedure similar to Example 1. FIG.

(3) Results Table 6 shows the results of the moisture permeation resistance test and the pressure resistance test of each battery case (Examples 17 to 24).

In the battery cases of Examples 17 to 24, the area ratio of the pit forming portion on the joint surface is 65 area% or more, and the ratio of pit diameters D ₁ / D _{2 on} the joint surface is 1.1 or more is 35. Since it was several percent or more and the molding shrinkage of the thermoplastic resin composition was 0.8% or less, good evaluation was obtained regarding moisture permeability resistance and pressure resistance.

[Example 3]
In Example 3, an example is shown in which a roughened stainless steel plate is produced by an immersion method, and the battery case of Embodiment 2 is produced.

1. Production of Roughened Stainless Steel Sheet The following two types of stainless steel sheets were prepared as test stainless steel sheets.
Stainless steel plate A: SUS304, 2B finish, plate thickness 0.8mm
Stainless steel plate C: SUS430, 2B finish, plate thickness 0.8mm

After each stainless steel plate (stainless steel plates A and C) was alkaline degreased (pH 12, liquid temperature 60 ° C., immersion time 1 minute), the conditions shown in Table 7 in the aqueous ferric chloride solution having the composition shown in Table 7 (liquid The pits were formed on the surface of each stainless steel plate.

For each stainless steel plate having been subjected to the roughening treatment (steel Nanba31～39), the area ratio of the pit, the ratio _D 1 / _{D 2} of the maximum diameter _{D 1} of the pit internal to the diameter _{D 2} of the pit openings 1. The ratio of one or more pits was determined.

Table 8 shows the types of stainless steel plates, immersion treatment conditions (treatment No.), area ratios of pit forming portions, and pit diameter ratios D ₁ / D ₂ for the respective stainless steel plates (steel plates No. 31 to 39). Indicates the ratio of pits of 1.1 or more.

2. Moisture permeation resistance test and pressure resistance test (1) Moisture permeation resistance test In the same procedure as in Example 2, from each stainless steel plate (steel plates No. 31 to 39), the case main body 210 having the shape shown in FIG. Sealing body 220 was produced. Further, as shown in FIG. 14, the case main body 210 has clean water 310 in the same procedure as in the second embodiment, and the case main body 210 and the sealing body 220 are formed from a thermoplastic resin composition 230. Thus, battery cases (Examples 25 to 30 and Comparative Examples 8 to 10) hermetically sealed were obtained.

  About each obtained battery case (Examples 25-30, Comparative Examples 8-10), the moisture-permeation resistance test was done in the procedure similar to Example 1. FIG.

(2) Pressure resistance test Battery cases (Examples 25 to 30 and Comparative Examples 8 to 10) were prepared from the respective stainless steel plates (steel plates Nos. 31 to 39) in the same procedure as the moisture permeation resistance test. At this time, as shown in FIG. 15, clean water was not poured into the case main body 210, and the air injection pipe 320 was attached to the central portion of the sealing body 220.

  About each obtained battery case (Examples 25-30, Comparative Examples 8-10), the pressure | voltage resistant test was done in the procedure similar to Example 1. FIG.

(3) Results Table 9 shows the results of the moisture permeation resistance test and the pressure resistance test of each battery case (Examples 25 to 30, Comparative Examples 8 to 10).

In the battery cases of Examples 25 to 30, the area ratio of the pit forming portion on the joint surface is 65 area% or more, and the ratio of pit diameters D ₁ / D _{2 on} the joint surface is 1.1 or more is 35. Since it was several percent or more and the molding shrinkage of the thermoplastic resin composition was 0.8% or less, good evaluation was obtained regarding moisture permeability resistance and pressure resistance.

On the other hand, in the closed containers of Comparative Examples 8 and 9, the area ratio of the pit formation portion on the joint surface is less than 65 area%, and the pit diameter ratio D ₁ / D _{2 on the} joint surface is 1.1 or more. Since the ratio of pits was less than 35% by number, good evaluation on moisture permeation resistance (only Comparative Example 9) and pressure resistance could not be obtained. Further, in the battery case of Comparative Example 10, since the molding shrinkage rate of the thermoplastic resin composition was more than 0.8%, good evaluation on moisture permeation resistance and pressure resistance could not be obtained.

  The battery case of the present invention is useful as a battery case for a secondary battery such as a lithium ion battery.

100, 200 Battery case 110, 210 Case body 112 Flange part 114, 214 Housing part 116, 216 Case body joint surface 120, 220 Sealing body 122, 222 Sealing body joint surface 130, 230 Molded body of thermoplastic resin composition 140, 240 Injection mold 142, 242 Resin inflow portion 144, 244 Resin injection port 212 Stepped portion 218 A portion above the stepped portion of the case body 224 Side surface portion of sealing body 310 Water supply 320 Air injection pipe

Claims (9)

A case body made of a metal plate;
A sealing body made of a metal plate for sealing the opening of the case body;
A molded body of a thermoplastic resin composition that is bonded to the case body and the sealing body and hermetically seals the case body and the sealing body, and
The case body and the sealing body each have pits formed in 65% by area or more of the joint surface with the molded body of the thermoplastic resin composition,
In each of the case body and the sealing body, 35% by number or more pits of the pits formed at the interface between the molded article of the thermoplastic resin composition of the pit internal to the diameter D ₂ of the pit openings the ratio _D 1 / _{D 2} of the maximum diameter _{D 1} is not less than 1.1,
The molding shrinkage ratio of the thermoplastic resin composition is 0.8% or less.
Battery case.   The battery case according to claim 1, wherein the metal plate constituting the case main body and the sealing body is a stainless steel plate.   The thermoplastic resin composition comprises a polypropylene resin, a polybutylene terephthalate resin, a tetrafluoroethylene-perfluoroalkyl vinyl ether resin, a polycarbonate resin, an acrylonitrile-butadiene-styrene resin, a polyacetal resin, and a polyphenylene sulfide resin. The battery case according to claim 1, comprising at least one thermoplastic resin selected from the group consisting of: Preparing a case body made of a metal plate and a sealing body made of a metal plate;
Installing the case body and the sealing body in an injection mold; and
The thermoplastic resin composition is injected into the injection mold, the molded body of the thermoplastic resin composition is joined to the case body and the sealing body, and the case body and the sealing body are hermetically sealed. And having steps,
The case body and the sealing body each have pits formed in 65% by area or more of the joint surface with the molded body of the thermoplastic resin composition,
In each of the case body and the sealing body, 35% by number or more pits of the pits formed at the interface between the molded article of the thermoplastic resin composition of the pit internal to the diameter D ₂ of the pit openings the ratio _D 1 / _{D 2} of the maximum diameter _{D 1} is not less than 1.1,
The molding shrinkage ratio of the thermoplastic resin composition is 0.8% or less.
A battery case manufacturing method.   The battery case manufacturing method according to claim 4, wherein the metal plate constituting the case body and the sealing body is a stainless steel plate. The battery case manufacturing method according to claim 4, wherein the pits formed on the joint surface of the case body and the sealing body are formed by bringing the metal plate into contact with an aqueous solution containing Fe ³⁺ .   The method for manufacturing a battery case according to claim 6, wherein the aqueous solution is an aqueous ferric chloride solution.   The thermoplastic resin composition comprises a polypropylene resin, a polybutylene terephthalate resin, a tetrafluoroethylene-perfluoroalkyl vinyl ether resin, a polycarbonate resin, an acrylonitrile-butadiene-styrene resin, a polyacetal resin, and a polyphenylene sulfide resin. The manufacturing method of the battery case of Claim 4 containing 1 or more types of thermoplastic resins selected from the group which consists of.   The secondary battery which has a battery case as described in any one of Claims 1-3.