JP2010097771A - Container of secondary battery and method for manufacturing secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery hardly breaking a battery container, a container of a secondary battery, and a method for manufacturing the secondary battery. <P>SOLUTION: The container of the secondary battery includes a body part which is a box type in which the upper surface is an opening surface and housing a secondary power generation element; and a lid arranged so as to seal the opening surface and welded to the edge portion of the opening surface, and the body part is constituted with an aluminum material having a tensile strength of 150 N/mm<SP>2</SP>or more at normal temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary battery container and a method for manufacturing a secondary battery.

  Rechargeable secondary batteries are known. FIG. 1 is a perspective view showing an example of a secondary battery. The secondary battery in FIG. 1 includes a battery container. The battery container is usually made of metal and is configured to act as an electrode of the secondary battery.

  The battery container includes a main body 1 and a lid 2. The main body 1 has a box shape with an upper surface opened. The lid 2 is disposed so as to close the opening surface of the main body 1. The lid | cover 2 is joined to the opening edge of a main-body part normally by welding. The lid 2 is provided with a safety valve 23, a negative electrode terminal 21, a positive electrode terminal 22, and the like.

  Although not shown, a power generation element is accommodated in the battery container. The power generation element includes a positive electrode and a negative electrode, and the positive electrode and the negative electrode face each other via a separator. In addition, an electrolytic solution is sealed in the battery container, and the power generation elements (positive electrode and negative electrode) are immersed in the electrolytic solution.

  In such a secondary battery, the power generation element may expand and contract during charging and discharging. For example, when graphite is used as the negative electrode material, the negative electrode may expand during charging. In addition, the negative electrode may shrink during discharge. Furthermore, when a nonaqueous electrolytic solution is used as the electrolytic solution, the electrolytic solution is decomposed during the operation of the secondary battery to generate gas, and the generated gas may increase the internal pressure of the battery container. It is conceivable that the battery container is deformed and damaged due to expansion and contraction of the power generation element and an increase in internal pressure. Therefore, it is desirable that the battery container is configured so as not to be damaged during use.

As a related technique, Patent Document 1 (Japanese Patent Laid-Open No. 2006-324160) is cited. In Patent Document 1, chamfering is performed on the lower side of the abutting surface of the battery lid so that the width of the abutting surface is smaller than the thickness of the battery lid, and the tip of the weld bead extends below the lower side of the abutting surface. A battery casing sealing structure is disclosed.
JP 2006-324160 A

  An object of the present invention is to provide a secondary battery, a secondary battery container, and a method for manufacturing the secondary battery, in which the battery container is not easily damaged.

  In the following, means for solving the problem will be described using reference numerals with parentheses used in [Best Mode for Carrying Out the Invention]. These symbols are added in order to clarify the correspondence between the description of [Claims] and the description of the best mode for carrying out the invention. ] Should not be used for interpretation of the technical scope of the invention described in the above.

The secondary battery container according to the present invention has a shape in which an upper end surface is opened, and is disposed so as to close the main body portion (1) that houses a chargeable / dischargeable secondary power generation element (4) and the upper end surface thereof. And a lid (2) welded to the upper end of the main body (1). The main body (1) is made of an aluminum material having a tensile strength of 150 / mm ² or more at room temperature.
It is assumed that the battery container has repeatedly expanded and contracted due to charging and discharging. Due to the expansion and contraction, the angle formed by the main body (1) and the lid (2) changes many times at the welded portion between the main body (1) and the lid (2). Thereby, a welding part raise | generates a metal fatigue and may be damaged. On the other hand, according to the present invention, the main body (1) has a residual stress at the time of molding. And the change amount of the angle formed by the lid (2) is suppressed. As a result, metal fatigue at the welded portion is suppressed and the battery container is prevented from being damaged.

  The aluminum material is preferably an aluminum alloy containing Al at a ratio of 99% or more. Such an aluminum material has high toughness and hardly causes metal fatigue. Even when a low load force is repeatedly applied due to expansion and contraction, the battery container is hardly damaged.

  The aluminum material is preferably a material whose shape is processed cold from the base material. By using a cold processed material, the aluminum material can be used as the main body (1) in a work-hardened state.

  From one viewpoint, the aluminum material is more preferably processed in shape by cold forging. The aluminum material is more preferably processed in shape by an impact press.

  The secondary battery which concerns on this invention comprises the above-mentioned secondary battery container, and the secondary power generation element (4) which can be charged / discharged accommodated in the secondary battery container.

  The manufacturing method of the secondary battery according to the present invention includes a step of producing a main body (1) having an upper end surface opened by plastic processing using an aluminum material as a base material, and a filling in the main body (1). After the step of storing the secondary power generation element (4) capable of discharging and the step of storing the secondary power generation element, the lid (2) is disposed so as to close the upper end surface of the main body (1), and the lid ( 2) welding to the upper end of the main body (1). The process from the process of producing the main body part to the process of welding is performed cold.

The step of producing the main body part preferably includes a step of plastic working so that the main body part (1) has a higher tensile strength than the base material. Specifically, an aluminum material having a tensile strength of 60 to 100 N / mm ^{2 at} normal temperature is prepared as a base material. And the main-body part (1) whose tensile strength is 150 N / mm < ² > or more at normal temperature is obtained by cold forging the prepared base material.

  In the above secondary battery manufacturing method, the aluminum material is preferably an aluminum alloy containing Al at a ratio of 99% or more.

  In the above-described method for manufacturing a secondary battery, from one viewpoint, it is preferable that the step of manufacturing the main body includes a step of performing cold forging as the plastic working.

  In the above-described method for manufacturing a secondary battery, from another viewpoint, it is preferable that the step of manufacturing the main body includes a step of performing an impact press as the plastic working.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the secondary battery with which a battery container cannot be damaged easily, a secondary battery container, and a secondary battery is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing the secondary battery according to the present embodiment. The secondary battery according to this embodiment is a lithium secondary battery that is a non-aqueous electrolyte secondary battery.

  As shown in FIG. 2, the secondary battery includes a secondary battery container and a power generation element 4.

  The secondary battery container includes a main body 1 and a lid 2. The main body 1 and the lid 2 are made of aluminum (made of aluminum or aluminum alloy). The main body 1 has a box shape with an upper end surface opened. The lid | cover 2 is arrange | positioned so that an upper end surface may be plugged up. The lid 2 is joined to the edge of the opening of the main body 1 by welding. In FIG. 2, a joint portion between the main body 1 and the lid 2 is shown as a welded portion 3. The lid 2 is provided with a positive terminal 21, a negative terminal 22, and a safety valve 23. The positive electrode terminal 21 and the negative electrode terminal 22 are attached to the lid via an insulator.

  The power generation element 4 is accommodated in the secondary battery container. A nonaqueous electrolytic solution is sealed in the secondary battery container, and the power generation element 4 is impregnated with the nonaqueous electrolytic solution. As the non-aqueous electrolyte, a solution containing lithium ions is used.

The power generation element 4 includes a plurality of positive electrodes and a plurality of negative electrodes. The plurality of positive electrodes and the plurality of negative electrodes are alternately stacked via separators. The plurality of positive electrodes are connected to the positive electrode terminal 21 via the positive electrode lead 41. The plurality of negative electrodes are connected to the negative electrode terminal 22 via the negative electrode lead 42. Each of the plurality of positive electrodes has a main body made of, for example, an aluminum foil, and a positive electrode active material (eg, lithium manganate, LiMn ₂ O ₄ ) capable of inserting and extracting lithium ions on the surface of the main body. . As each of the plurality of negative electrodes, for example, carbon or graphite is used.

  The safety valve 23 provided on the lid 2 is provided for discharging the gas in the secondary battery container when the internal pressure in the secondary battery container increases. The safety valve 23 is designed to be opened when the internal pressure of the secondary battery container exceeds a predetermined value.

  Then, the material of the main-body part 1 is demonstrated.

As described above, the main body 1 is made of aluminum. The main body 1 is manufactured by cold forging an aluminum base material. The main body 1 has a tensile strength equal to or greater than the tensile strength of the base material. Specifically, the main body 1 has a tensile strength of 150 N / mm ² or more at room temperature. This includes the effect of compressive stress (residual stress) generated when the main body 1 is manufactured. By having the tensile strength as described above, the secondary battery container is prevented from being damaged. The reason will be described below.

  If the main body 1 has no residual stress, the secondary battery container easily expands and contracts easily. FIG. 3A is a schematic diagram showing a state when the secondary battery container is expanded. When an expanding force is applied to the secondary battery container, an angle (θ in the figure) formed by the lid and the main body portion increases at the joint portion (welded portion 3) between the main body portion 1 and the lid 2. On the other hand, FIG. 3B is a schematic diagram showing a state when the secondary battery container contracts. At the time of contraction, the angle θ formed by the lid and the main body portion becomes small in the welded portion. When charging / discharging is repeated, expansion and contraction are repeated. When the expansion and contraction are repeated, the angle θ formed by the lid and the main body changes repeatedly. As a result, metal fatigue occurs in the welded portion 3, and the welded portion 3 is easily damaged.

  On the other hand, when the main body 1 has residual stress, the secondary battery container is difficult to expand and shrink. FIG. 4A is a schematic diagram illustrating a state when an expanding force is applied to the secondary battery container in the present embodiment. As shown in FIG. 4A, since the main body 1 itself has residual stress, even if an expansion force is applied to the main body 1, the angle θ in the welded portion 3 does not increase so much. FIG. 4B is a schematic diagram illustrating a state when a contracting force is applied to the secondary battery container. Similarly to the case where the expansion force is applied, the angle θ in the welded portion 3 is not so small due to the residual stress of the main body portion 1.

  Thus, according to the present embodiment, the deformation of the secondary battery container is suppressed because the main body 1 has residual stress. As a result, metal fatigue in the welded portion 3 is suppressed, and damage to the secondary battery container is prevented.

  The tensile strength of the main body 1 can be measured by, for example, a tensile test defined in JIS standard (JIS Z 2241; 1998).

  Then, the manufacturing method of the secondary battery which concerns on this embodiment is demonstrated.

First, the main body 1 is manufactured. Specifically, a base material of an aluminum material having a tensile strength of 60 to 100 N / mm ² at normal temperature is prepared, and the main body 1 is manufactured by plastic processing the base material. Here, by performing plastic working cold, stress remains in the molded product, and the aluminum material is work-hardened. By work hardening, the strength is increased, and the main body 1 having a tensile strength equal to or higher than the tensile strength of the base material can be obtained. Specifically, the main body 1 having a tensile strength of 150 N / mm ² or more at room temperature can be obtained. That is, it is possible to make the main body 1 difficult to be damaged by performing cold forging.

  Specifically, an impact press is preferably used as the cold forging. When an impact press is used, a large amount of products can be processed in a short time. FIG. 5A is an explanatory diagram for explaining an impact press. As shown in FIG. 5A, the base material 5 is disposed between the upper mold and the lower mold. Then, the base material 5 is pressed by the upper mold. Thereby, the base material 5 is plastically deformed, and the molding material 6 is produced as shown in FIG. 5B. This molding material 6 is used as the main body 1.

  After the main body 1 is created, the power generation element is stored in the main body 1. Thereafter, the lid 2 is welded to the opening edge of the main body 1 to produce a sealed secondary battery container.

  Thereafter, the electrolytic solution is injected from an opening (not shown) for injecting the electrolytic solution provided in the lid 2, and the secondary battery according to this embodiment is obtained.

  Then, the material of the main-body part 1 is demonstrated.

  As an aluminum material used for the main-body part 1, the aluminum alloy prescribed | regulated to A1000 series by JIS standard and the aluminum alloy prescribed | regulated to A3000 series by JIS standard (JIS H4000; 2006) can be mentioned, for example.

  As the aluminum material, it is more preferable to use an aluminum alloy containing Al at a ratio of 99% or more. As such an aluminum alloy, specifically, an aluminum alloy specified in the A1000 range in accordance with JIS standards (JIS H 4000; 2006) can be given.

  An aluminum alloy containing 99% or more of Al is excellent in toughness. By being excellent in toughness, even if the secondary battery container repeats expansion and contraction, it is difficult to cause metal fatigue. Further, when the main body 1 is rigid, cracks are likely to occur when the lid 2 is welded to the opening edge of the main body 1. As described above, by using an aluminum alloy having excellent toughness, cracks are less likely to occur when the lid 2 is welded.

  As described above, according to the present embodiment, the reliability of the welded portion can be increased because the main body 1 has a tensile strength equal to or higher than the tensile strength of the base material.

  This effect is due to the fact that the main body 1 can be provided with residual stress by performing cold forging.

  Furthermore, by using an aluminum alloy containing Al at a ratio of 99% or more as a constituent material of the main body 1, it is possible to make it difficult for cracks to occur when the lid 2 is welded.

It is a perspective view which shows a secondary battery. It is sectional drawing which shows a secondary battery. It is explanatory drawing which shows a mode when expansion force is added to the secondary battery. It is explanatory drawing which shows a mode when contraction force is added to the secondary battery. It is explanatory drawing which shows a mode when expansion force is added to the secondary battery. It is explanatory drawing which shows a mode when contraction force is added to the secondary battery. It is explanatory drawing for demonstrating an impact press. It is explanatory drawing for demonstrating an impact press.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main-body part 2 Lid 21 Positive electrode terminal 22 Negative electrode terminal 23 Safety valve 3 Welding part 4 Secondary power generation element 41 Positive electrode lead 42 Negative electrode lead 5 Base material 6 Molding material

Claims (10)

A box-shaped upper surface is an open surface, and a main body that houses a chargeable / dischargeable secondary power generation element;
A lid arranged to close the opening surface and welded to an edge portion of the opening surface;
Comprising
The said main-body part is a secondary battery container comprised by the aluminum material which has the tensile strength of 150 N / mm < ² > or more at normal temperature. The secondary battery container according to claim 1,
The secondary battery container, wherein the aluminum material is an aluminum alloy containing Al at a ratio of 99% or more. A secondary battery container according to claim 1 or 2,
The aluminum material is a secondary battery container whose shape is processed by cold forging. A secondary battery container according to claim 3,
The aluminum material is a secondary battery container whose shape is processed by an impact press. A secondary battery container according to any one of claims 1 to 4,
A chargeable / dischargeable secondary power generation element housed in the main body,
A secondary battery comprising: Using an aluminum material as a base material, a step of producing a box-shaped main body portion whose upper surface is an open surface by plastic working;
Storing a chargeable / dischargeable secondary power generation element in the main body;
After the step of housing the secondary power generation element, placing a lid so as to close the opening surface, and welding the lid to an edge portion of the opening surface;
Comprising
The method for manufacturing a secondary battery is performed cold from the step of producing the main body to the step of welding. A method for manufacturing a secondary battery according to claim 6, comprising:
The step of producing the main body includes a step of plastic processing so that the main body has a tensile strength equal to or higher than the tensile strength of the base material. A method of manufacturing a secondary battery according to claim 7,
The step of producing the main body part includes:
Preparing an aluminum material having a tensile strength of 60 to 100 N / mm ^{2 at} room temperature as the base material;
Forming the main body having a tensile strength of 150 N / mm ² or more at room temperature by cold forging the base material. A method of manufacturing a secondary battery according to claim 7 or 8,
The method for manufacturing a secondary battery, wherein the aluminum material is an aluminum alloy containing Al at a ratio of 99% or more. A method of manufacturing a secondary battery according to any one of claims 7 to 9,
The step of producing the main body includes a step of performing an impact press as the plastic working.

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