JP3630992B2 - Battery and method for manufacturing battery can - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery in which the volume energy density and weight energy density of a battery are improved by improving the structure of the battery can, and a method for manufacturing the battery can.
[0002]
[Prior art]
With the progress of miniaturization and weight reduction of devices using batteries, particularly portable devices such as mobile phones, improvement of the energy density of the batteries is required. Batteries with standardized outer sizes are desired to have higher energy density and lighter weight even with the same standard size. As an index indicating the energy density of a battery, a volume energy density (Wh / l) serving as an index of battery miniaturization and a weight energy density (Wh / kg) serving as an index of battery weight reduction are used. An important factor that determines the energy density of a battery is a power generation element composed of positive electrode and negative electrode active materials, electrolytes, and the like. A battery can that accommodates this power generation element improves the volume energy density and weight energy density. There are many degrees that contribute to. That is, by reducing the thickness of the battery can, it is possible to increase the volume of the battery can whose outer dimensions are standardized, and the volume energy density of the entire battery is improved due to the increase in the capacity of the power generation element To do. Further, the weight of the battery can be reduced by reducing the weight of the battery can, and the weight energy density can be improved. The weight ratio of the battery can to the weight of the entire battery is 10 to 20 wt% in the case of a cylindrical battery in a nickel metal hydride storage battery or a lithium ion secondary battery at present. In the case of a square battery, the thickness of the battery can needs to be increased in order to obtain the pressure resistance, so that it is 30 to 40 wt%. The weight energy density can be improved by reducing the weight ratio.
[0003]
In order to reduce the thickness and weight of battery cans, various improvements have been made to the materials used for battery cans and processing technology. For rectangular lithium ion secondary batteries, aluminum or aluminum alloys must be used for battery can materials. Thus, the weight ratio can be reduced to 20 to 30 wt%. Further, as a manufacturing method for processing a battery can into a bottomed cylindrical shape, for example, as described in Japanese Patent Publication No. 7-99688, a DI (Drawing and Ironing) method using both drawing processing and squeeze processing is used. In addition to improving productivity by reducing the number of manufacturing steps, it is possible to reduce the thickness, and in the case of using aluminum killed steel (SPCE material), the volume energy density of the battery has been improved by 2 to 5%.
[0004]
[Problems to be solved by the invention]
However, maintaining the strength of the battery can is an indispensable element for ensuring the reliability and safety of the battery, and the energy density cannot be improved at the expense of strength. In the case of a primary battery, in order to ensure capacity during long-term storage, prevent leakage, or obtain stable discharge characteristics, in the secondary battery, in addition to the elements required for the primary battery, charge / discharge cycle life and safety or It is necessary to maintain a strength that can cope with bulging deformation caused by an increase in the internal pressure of the battery. In addition, since the type of electrolyte used depends on the type of battery, the material used as the battery can needs to have corrosion resistance against the electrolyte, and it is easy to select the material for forming the battery can. Can not.
[0005]
Therefore, in order to improve the energy density while securing the strength, a material having high strength and light weight and excellent in corrosion resistance is required. However, a material satisfying this requirement has not been developed. As materials currently used as battery cans, there are iron-based materials such as aluminum killed steel and aluminum-based materials such as aluminum alloys. In either case, the battery cans have advantages and disadvantages. That is, the aluminum killed steel has a Young's modulus of about 20000 kgf / mm.²Therefore, it is possible to reduce the thickness of the battery can and improve the volume energy density, but the specific gravity is about 7.8, which increases the weight of the battery can and improves the weight energy density. I can't let you. On the other hand, the specific gravity of the aluminum alloy is about 2.7, but the Young's modulus is about 7000 kgf / mm.²Therefore, although it can contribute to weight reduction, the rigidity is inferior, so it is necessary to form it thick to obtain the strength as a battery can, the volume energy density is reduced, and the weight energy density is also reduced in terms of weight energy density. I can't save it.
[0006]
Therefore, in order to take advantage of the characteristics of each of the iron-based material and the aluminum-based material, attempts have been made to use a material in which the clad material is formed as a battery can. A cylindrical shape is disclosed in Japanese Patent Laid-Open No. 1-294350. However, a battery can formed into a bottomed cylindrical shape in which the battery capacity is increased by increasing the height dimension of a cylindrical shape or a rectangular tube shape has not yet been realized.
[0007]
An object of the present invention is to provide a battery capable of improving the volume energy density and weight energy density of the battery by reducing the thickness and weight of the battery can and a method for manufacturing the battery can. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a first invention of the present application is a battery in which a power generation element is accommodated in a battery can formed in a bottomed cylindrical shape, wherein the battery can is made of aluminum or an alloy mainly composed of aluminum. The clad material comprising the first layer and the second layer formed of iron or an iron-based alloy has a bottom surface thickness / side surface thickness ratio of 1.2 to 5.0. It ’s formed to beThe battery can is formed in a bottomed cylindrical shape with the first layer as the outer surface side.It is characterized by that.
[0009]
According to the above configuration, since the battery can containing the power generation element is formed of the clad material obtained by joining the aluminum-based material and the iron-based material, the battery can is formed by taking advantage of the characteristics of each of the different metals. Improvements can be made. In other words, aluminum-based materials are lightweight, but to obtain strength as a battery can, they must be formed thick, and the problem of being unable to take advantage of their lightweight properties can be compensated by the rigidity of iron-based materials. Therefore, a thin battery can can be formed by reducing the wall thickness. By reducing the thickness of the battery can, the capacity of the power generation element is increased by increasing the capacity of the battery can and the volume energy density of the battery is improved. At the same time, the weight energy density can be improved by reducing the weight.
Further, by forming the battery can in a bottomed cylindrical shape with the first layer as the outer surface side, the battery can is formed with the iron-based material as the inner surface side, and preferably nickel plating is applied to the surface to form an electrolyte solution. The battery can can be configured as a negative electrode of the battery while ensuring corrosion resistance. Further, since the aluminum-based material is on the outer surface side, the weldability to the battery can is improved.
In addition, when making the clad material into a bottomed cylindrical shape whose side peripheral surface height is larger than the bottom surface diameter, it is effective to reduce the weight by forming the side peripheral surface with a large weight ratio thin, and the bottom surface thickness is increased by the DI method. The can can be manufactured so that the thickness / side peripheral surface thickness ratio is 1.2 to 5.0. In addition, since the thermal expansion coefficient differs between aluminum-based materials and iron-based materials, when this battery can is applied to a secondary battery, the battery can swells and deforms due to an increase in internal pressure accompanying a temperature rise during charging. Bending stress acts in the direction to suppress the occurrence and suppresses the bulging deformation, so that the required deformation strength can be maintained even if the side peripheral surface is made thin.
[0010]
By forming the first layer in the above configuration with an aluminum alloy containing 0.5 to 2.5 wt% manganese in aluminum, the can-making property is improved and the weldability to the battery can is also improved.
[0011]
Further, the second layer is made of carbon steel for cold rolling with a carbon content of 0.1 wt% or less, so that the squeaking process during DI processing can be smoothly performed and the can-making performance is improved. Battery failure due to can failure can be eliminated.
[0012]
Further, the second layer has a carbon content of 0.1 wt% or less, and at least one of titanium and niobium has a content of 0.1 wt% or less. Can be improved.
[0013]
Further, the second layer can be made of SUS304 or SUS430 stainless steel, and when arranged so as to be on the inner surface side of the battery can, the corrosion resistance to the electrolytic solution can be improved.
[0014]
Moreover, it is desirable that the thickness of each of the first and second layers is 10 to 300 μm, and the thickness when the clad material is used is 20 to 600 μm. A material of 10 μm or less is expensive and not practical. This is suitable for the thickness of the clad material that can be stably produced.
[0015]
Moreover, by providing nickel layers on both sides or one side of the first layer and / or the second layer, the bondability between the aluminum-based material and the iron-based material is improved, and the battery has a stable quality by DI processing. Cans can be manufactured. In addition, since the nickel layer is provided on the surface of the iron-based material, the battery can is manufactured with good corrosion resistance against the alkaline electrolyte with the iron-based material facing the inner surface, and can be applied as a battery can such as a nickel metal hydride storage battery. It is suitable for.
[0016]
The nickel layer is preferably formed so that its thickness is 0.5 to 10 μm after canning. Since the nickel layer is also thinned by drawing and squeaking, the above value can be obtained after canning by setting the nickel plating thickness to 1.0 to 20 μm. Further, in order to suppress the nickel plating cost with a thickness that does not generate pinholes, it is appropriate to provide a nickel layer at the thickness.
[0018]
Further, by forming the battery can in a bottomed cylindrical shape with the second layer as the outer surface side, the outer surface of the battery can is made of an iron-based material, so that the battery can hardly be damaged and has excellent durability and easy sealing.
[0019]
Moreover, since the surface area of the battery can inner surface is increased by forming a large number of fine grooves in the cylinder forming direction on the inner surface of the side peripheral surface, the contact resistance between the power generation element and the battery can is reduced, and the battery performance is reduced. Improvements can be made.
[0020]
It is preferable that the fine groove is formed only on the surface of the nickel layer.
[0021]
In the case where the nickel layer is present, the corrosion resistance due to the nickel layer is not impaired by preventing the fine groove from reaching the substrate surface beyond the nickel layer. Since the formation depth of the fine groove is very small, this state is realized by forming the nickel layer at a depth greater than the depth of the fine groove.
[0022]
In addition, the thickness of the sealing portion having the weakest pressure resistance can be increased by forming the thickness of the side peripheral surface on the opening end side of the battery can 10% or more thicker than other side peripheral surfaces. By increasing the thickness of the entire side peripheral surface, the pressure strength can be increased without causing a decrease in volume and an increase in weight.
[0023]
In the case of a bottomed cylindrical battery can with an outer diameter of 35 mmφ or less, the configuration can be formed such that the side peripheral surface on the opening end side is 30% or more thicker than the thickness of the other side peripheral surface. In the case of a cylindrical battery can with a small outer diameter, even if the thickness of the side peripheral surface is reduced, the battery can hardly be swollen and deformed, and only the thickness of the side peripheral surface on the opening end side that becomes the sealing portion is increased. By doing so, the sealing pressure resistance strength as a battery can be obtained.
[0024]
Further, by forming the rising part from the bottom surface of the battery can formed in the bottomed cylindrical shape to the side peripheral surface to be a curved surface having a curvature radius of 0.5 mm or less, the thickness of the bottom surface / thickness of the side peripheral surface It becomes possible to form a large thickness ratio, and even if the thickness of the side peripheral surface is reduced, the swelling deformation of the battery can can be suppressed. The larger the radius of the curved surface of the rising portion, the better the workability. However, the space for accommodating the power generation element in the battery can is impaired, and the smaller the radius of the curved surface is desirable in consideration of the workability.
[0025]
The second invention of the present application is a method for manufacturing a battery can containing a power generation element.A first layer formed of aluminum or an alloy mainly composed of aluminum and a second layer formed of iron or an alloy mainly composed of ironClad material is drawn by a press machineThe first layer was on the outer sideAfter forming into a cup-shaped intermediate product, the bottomed thickness / side surface thickness becomes 1.2 to 5.0 by DI method in which the cup-shaped intermediate product is squeezed using a drawing die and a squeeze die. It is formed in a cylindrical shape
[0026]
According to the above manufacturing method, the battery can isA first layer formed of aluminum or an alloy mainly composed of aluminum and a second layer formed of iron or an alloy mainly composed of ironClad materialThe first layer was on the outer sideAfter drawing into a cup-shaped intermediate product, the intermediate product can be formed into a desired bottomed cylindrical shape in one step by the DI method, and the height and thickness of the side peripheral surface can be formed to desired values. .
By forming the battery can into a bottomed cylindrical shape with the first layer as the outer surface side, the battery can is formed with the iron-based material as the inner surface side, preferably with nickel plating on the surface to make the electrolyte resistant to corrosion. The battery can can be manufactured as a negative electrode of the battery. Moreover, since an aluminum-type material becomes an outer surface side, a battery can with good weldability can be manufactured.
By drawing and squeezing the DI method, the side peripheral surface is stretched thin with the thickness ratio of the joining metal of the clad material, so a lightweight aluminum-based material and a rigid iron-based material as the base material of the metal layer to be joined By forming the material thin, it is possible to efficiently manufacture a battery can having a predetermined strength while reducing the weight with fewer steps. Since the battery can formed in such a thin wall has an increased volume and can increase the capacity of the power generation element, the volume energy density of the battery can be improved. Moreover, the weight energy density of a battery can be improved by weight reduction.
[0027]
By continuously squeezing in one step so that the squeeze rate by DI processing in the above manufacturing method is in the range of 20 to 90%, the battery can is formed in a bottomed cylindrical shape with a thin side peripheral surface. The battery can can be manufactured with a predetermined strength even if the clad material is formed thin.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0029]
The battery according to this embodiment is characterized by using a clad material obtained by pressure-rolling an iron-based material and an aluminum-based material for a battery can that houses a power generation element. In addition to verifying the effectiveness of the battery as a battery can, the type and shape of the battery to be applied were changed, and an appropriate configuration for forming the battery can using a clad material was verified.
[0030]
First, in order to construct an AA size nickel-metal hydride storage battery, the battery can is formed into a bottomed cylindrical shape with a finished outer diameter of 13.8 mmφ and a height of 49.0 mm, and a power generation element is accommodated in the nickel-metal hydride storage battery. A first embodiment in which is formed will be described.
[0031]
In FIG. 1, a nickel metal hydride storage battery 1 is formed by housing a power generation element 2 in a battery can 6 and sealing the opening end of the battery can 6 with a sealing plate 11. The battery can 6 used in the nickel metal hydride storage battery 1 is manufactured as described below using a clad material obtained by joining an aluminum-based material and an iron-based material.
[0032]
A pure aluminum material (corresponding to JIS-A1050) having a thickness of 200 μm for the first layer as the clad material, and an aluminum killed steel (hereinafter referred to as an SPCE material) having a thickness of 200 μm and a carbon content of 0.04 wt% for the second layer. The SPCE material is plated with nickel to a thickness of 2.5 μm and heat-treated, and then the first layer of aluminum material is overlaid and pressure-rolled to form a clad material having a thickness of 400 μm.
[0033]
This clad material is cut out in a circular shape, drawn with a press so that the inner surface side of the battery can is SPCE material and the outer surface side is aluminum material, and a cup-shaped intermediate product having an outer diameter of 21.5 mmφ and a height of 15.5 mm 5 to form. In this state, there is almost no change in the thickness of the bottom surface and the thickness of the side peripheral surface from the original cladding material. The cup-shaped intermediate product 5 formed in this way is sent to the DI processing step as shown in FIG. 2, and is formed into a bottomed cylindrical shape whose side surface has a predetermined height by drawing and squeezing. In this DI method, the inner product 5 is pushed out by a punch 7 into a die row in which drawing dies 3 and squeeze dies 4, 4 and 4 are arranged in a straight line so that the inner diameter of the punch 7 decreases in the advance direction. Each time the intermediate product 5 is pushed into the squeeze dies 3 and the squeegee dies 4, the squeeze and squeeze are added to form a bottomed cylindrical battery can 6 of a predetermined size in one step. When the DI processing is performed, the outer diameter is 13.8 mmφ and the height is 54 mm, and the opening end side is not flat but undulated. Cut the ear on the open end side to 0 mm.
[0034]
FIG. 3 shows a cross-sectional shape of the battery can 6 formed by the DI method. The thickness of the bottom surface 6a is 400 μm, the thickness of the side peripheral surface 6b is 150 μm, and the thickness of the opening end side peripheral surface 6c is It is formed in a bottomed cylindrical shape of 170 μm. Therefore, the squeeze rate in DI processing of the battery can 6 is 63%. The squeeze rate is defined as “squeeze rate (%) = (original thickness−thickness after squeeze) × 100 / original thickness”. The bottom surface thickness / side peripheral surface thickness ratio is 2.67, and the weight is about 2.4 g. Incidentally, when a battery can of the same shape and the same size is formed of a single material of SPCE material, the weight is about 3.6 g, and the weight reduction of about 33% is achieved by forming it with a clad material.
[0035]
The opening end side peripheral surface 6c is formed to be about 13% thicker than the thickness of the side peripheral surface 6b in order to obtain a sealing strength for sealing the opening end with a sealing plate after the power generation element or the like is accommodated in the battery can 6. Has been. When the internal pressure of the battery rises, the sealing part becomes the weakest part in terms of pressure resistance, so that the pressure resistance due to the sealing can be increased by forming the sealing part thicker than the side peripheral surface 6b, and the thickness of the side peripheral surface 6b. Can be minimized to the extent that bulging deformation can be suppressed. In particular, when such a cylindrical battery can is formed to have an outer diameter of 35 mmφ or less, the thickness of the opening end side peripheral surface 6c can be 30% or more thicker than the other side peripheral surface 6b. In other words, in the case of a cylindrical shape of 35 mmφ or less, even if the side peripheral surface 6b is formed to be considerably thin, the bulging deformation due to the increase in battery internal pressure can be suppressed. By forming the opening end side peripheral surface 6c that is likely to be formed to a required thickness, the weight reduction of the battery can can be further promoted. Incidentally, the method of forming the opening end side peripheral surface 6c thicker than the side peripheral surface 6b is to increase the diameter of the punch 7 in the DI mold at the position of the opening end side peripheral surface 6c as shown in FIG. By forming it as small as the thickness corresponding to the thickness, the opening end is pushed inward so that the diameter of the punch 7 is reduced when passing through the squeeze die 4, and the opening end side peripheral surface 6c becomes the side peripheral surface 6b. It is formed thicker.
[0036]
FIG. 4 shows the cross-sectional shape of the corner portion rising from the bottom surface 6a to the side peripheral surface 6b in order to confirm the formation state of the battery can 6 formed by the DI method, as determined from a 50x metal microscope. The bottom surface 6a is made of a 200 μm thick aluminum material (Al) and a 200 μm thick SPCE material (referred to as Fe because it is an iron-based material) to a total thickness of 400 μm, and the side peripheral surface 6b is an aluminum material having a thickness of 75 μm. And a 75 μm-thick SPCE material to a total thickness of 150 μm, between which the corner portion with a radius of 0.4 mm smoothly changes the thickness of the bottom surface 6 a to the thin state of the side peripheral surface 6 b. I understand that. By providing a curved surface having a radius of 0.4 mm at the corner portion, it is possible to obtain smoothing processing and to obtain the pressure resistance of the battery can 6 in which the side peripheral surface 6b is thinned. If the radius of curvature of the corner is increased, the squeeze processing becomes easier and the pressure resistance is improved, but the effective volume of the power generating element accommodated in the battery can 6 is reduced, and the radius of curvature is made as small as possible. Therefore, the curvature radius is obtained.
[0037]
FIG. 5 shows the state of the inner surface of the side peripheral surface 6b obtained from a 3000 × scanning electron microscope. Fine grooves (parts that appear white) are formed in the direction of formation of the side peripheral surface 6b (cylindrical formation direction). Has been. This can be said to be a scratch caused by the punch 7 in the DI processing step, and is caused by a relatively hard particle such as alumina being interposed between the punch 7 and the battery can 6. The alumina particles are present on the surface of the clad material which is a raw material. However, in order to consciously promote the formation of grooves, the alumina powder is dispersed on the inner surface of the intermediate product 5 and then DI processing is performed. Is made more certain. The depth of the groove is about 1 μm, and is formed so as not to exceed the thickness of the nickel plating layer. FIG. 6 shows a cross section of the side peripheral surface 6b as a scanning electron micrograph at a magnification of 10,000. A nickel plating layer (Ni) is formed on the SPCE material (Fe), and a groove is formed in the nickel plating layer. Thus, it can be seen that the groove is formed so as not to exceed the nickel plating layer.
[0038]
Since the groove is formed on the inner surface of the battery can 6 in this manner, the surface area of the inner surface of the battery can 6 is increased, and the battery can 6 serving as one of the positive and negative electrodes of the battery is accommodated therein. The effect of significantly reducing the contact resistance with the power generating element is obtained.
[0039]
The battery can 6 formed as described above is reduced in weight by the aluminum material constituting the clad material, and the low pressure strength due to the low Young's modulus of the aluminum material is compensated by the rigidity of the SPCE material. be able to. In addition, when the battery can 6 is applied to a secondary battery, the swelling deformation caused by the increase in internal pressure accompanying the temperature increase during charging (maximum temperature of about 60 ° C.) is the coefficient of thermal expansion between the aluminum-based material and the iron-based material. Since the bending stress due to the difference acts as a stress that deforms the side peripheral surface 6b of the battery can 6 inward, an effect of suppressing the swollen deformation of the battery can 6 can be obtained.
[0040]
In order to produce a nickel metal hydride storage battery using the battery can 6 configured as described above, the following power generation element is accommodated in the battery can 6.
[0041]
First, the positive electrode is prepared by mixing spherical nickel hydroxide powder and additives such as zinc oxide, cobalt oxide, and cobalt hydroxide in a paste form, filling the sponge-like nickel conductive porous body, and then drying and pressing The positive electrode plate is formed by cutting to a predetermined size.
[0042]
Moreover, the negative electrode is AB as a hydrogen storage alloy.₅Type of MmNi_3.6Mn_0.4Al_0.3Co_0.7A conductive agent or binder is added to the alloy powder of the composition to form a paste, which is then applied to a nickel-plated iron punching metal core, formed into a predetermined size by drying, pressing and cutting, and a negative electrode plate To do. These positive electrode plate and negative electrode plate are wound through a separator made of a polypropylene non-woven fabric processed with sulfone, and are accommodated in the battery can 6. At this time, the outermost peripheral surface of the negative electrode plate is brought into direct contact with the inner surface of the battery can 6, and the lead is pulled out from the positive electrode plate and spot welded to the positive electrode terminal provided on the sealing cap.
[0043]
Next, lithium hydroxide (LiOH · H) is used as an electrolyte in the battery can 6.₂2.0 cc of an aqueous potassium hydroxide (KHO) solution having a specific gravity of 1.30 dissolved by 40 g / l of O) is injected. Then, in order to seal the opening end of the battery can 6 with the sealing cap, the sealing cap is attached by caulking the opening end side peripheral surface 6c, and the inside of the battery can 6 is hermetically sealed to complete the nickel hydride storage battery. The AA size nickel metal hydride storage battery thus manufactured has a battery weight of about 26 g and a battery capacity of 1350 mAh.
[0044]
Taking the battery can 6 produced as the first embodiment as (battery can 6A), in order to consider the suitability of the battery can 6A, battery cans 6B to 6G having the same standard size are produced by changing the composition and processing method. And nickel hydride storage battery was similarly produced with each battery can 6B-6G. Hereinafter, the battery cans 6B to 6G will be described while being compared with the battery can 6A.
[0045]
(Battery can 6B)
The battery can 6B is configured to verify the effectiveness of nickel plating on the surface of the iron-based material constituting the clad material. The battery can 6B has a thickness of 200 μm pure aluminum (equivalent to JIS-A1050), A clad material having a thickness of 400 μm obtained by pressure-rolling a 200 μm thick SPCE material (carbon content 0.04 wt%) was DI-processed to form the same size as that shown in FIG. The difference from the battery can 6A is that nickel plating is not applied to both surfaces of the SPCE material, and the other configurations are the same. Therefore, the bottom face thickness / side peripheral face thickness ratio (2.67), the squeeze rate (63%), and the weight (2.4 g) are substantially equal to the battery can 6A.
[0046]
In the above configuration, it was found that the drawing and squeeze processing in the DI processing, which is the can manufacturing process of the battery can 6B, is not always smooth, and a can manufacturing defect is likely to occur when compared with the case of the battery can 6A of the battery A. . This is thought to be due to the fact that the bonding strength between the aluminum-based material and the iron-based material is weakened due to the absence of the nickel plating layer, and the absence of the nickel plating layer on the contact surface with the DI mold.
[0047]
In addition, when the battery can 6B is applied to an alkaline storage battery such as a nickel metal hydride storage battery, charging characteristics, discharge characteristics, cycle life characteristics, and storage characteristics, which are presumed to be caused by corrosion by an alkaline electrolyte due to the absence of a nickel plating layer. A drop in However, when applied to a lithium ion secondary battery using an organic electrolyte, there is no problem at all, and it can be said that it has utility as a battery can except for a decrease in workability of DI processing.
[0048]
(Battery can 6C)
The battery can 6C has been verified for can manufacturing by the DI method based on the carbon content of the iron-based material constituting the clad material. The pure aluminum material (equivalent to JIS-A1050) having a thickness of 200 μm, the thickness of 200 μm, A clad material having a thickness of 400 μm obtained by pressure rolling a 2.3 μm-thick nickel plated SPCE material having a carbon content of 0.11 wt% was subjected to DI processing in the same manner as the battery can 6A. The same size as that shown in FIG. The bottom thickness / side surface thickness ratio (2.67), squeeze rate (63%), and weight (2.4 g) are the same as the battery can 6A, but the carbon content exceeds 0.1 wt%. The SPCE material has difficulty in DI processing, has a problem in workability for manufacturing a battery can, and could not be an appropriate battery can material.
[0049]
(Battery can 6D)
The battery can 6D has been verified for DI processability and weldability by the manganese content of the aluminum-based material constituting the clad material, and the manganese content is 0.4 wt% instead of the pure aluminum material of the battery can 6A. A clad material was formed using an aluminum alloy. Other configurations are the same as those of the battery can 6A. In the case of the configuration of the battery can 6D, since the content of manganese is small, the hardness of the aluminum alloy is low, and there is a problem in can-making performance by DI processing, and the intended configuration cannot be obtained.
[0050]
(Battery can 6E)
The battery can 6E uses an aluminum alloy having a high manganese content of 2.6 wt% on the contrary to the battery can 6D. In this case as well, there is a problem in can-making property, and the battery can be processed at the time of battery assembly. In addition, the weldability was poor and the desired configuration was not achieved.
[0051]
(Battery can 6F)
The battery can 6F is configured as a comparative example for comparing a battery can made of a clad material and a battery can made of a single material, and is the same DI processing with the same shape and dimensions as the battery can 6 shown in FIG. It is what went. There was no problem in can manufacturing ability, and even when the battery was configured, the same performance as that using the battery can 6A was obtained. However, since it is made of only iron-based material, the weight of the battery can increases, which leads to a capacity reduction of about 4% in terms of weight energy density as compared with the battery can 6A.
[0052]
(Battery can 6G)
The battery can 6G was manufactured by using a clad material having the same composition as the battery can 6A and changing the squeeze rate in DI processing in order to verify the appropriate range of the cylindrical bottom surface thickness / side peripheral surface thickness ratio. If the side surface thickness is 360 μm with respect to the bottom surface thickness of 400 μm, the squeeze rate at this time is 10%, and a high sealing pressure strength can be obtained. Not practical to use. In addition, since the effective volume in the battery can is reduced, the volume energy density is reduced by about 6% as compared with the battery can 6A. In order to increase the volume energy density, it is effective to reduce the thickness of the side peripheral surface. Therefore, a battery can having a side peripheral surface thickness reduced to 30 μm with respect to a bottom surface thickness of 400 μm is manufactured. Tried. In this case, the bottom face thickness / side peripheral face thickness ratio was as high as 13.3 and the squeeze rate was as high as 93%, and it was difficult to process into the required shape. As a result of the verification, an appropriate value of the ratio of bottom surface thickness / side peripheral surface thickness was set to 1.2 to 5.0.
[0053]
From the verification of the battery cans 6B to 6G according to the above embodiments, it can be seen that the configuration shown in Example 1 is appropriate as the battery can 6 applied to the AA size nickel metal hydride storage battery, and the conventional SPCE material alone The weight energy density can be improved as compared with the case using the battery can manufactured by the above, and the effectiveness of manufacturing the battery can made of the clad material by DI processing is shown.
[0054]
Next, in order to construct a square lithium ion secondary battery, the battery can is formed into a bottomed rectangular tube having a bottom size of 22 × 8 mm and a height of 48.0 mm, and a power generation element is accommodated in this. A second embodiment in which a lithium ion secondary battery is formed will be described.
[0055]
In FIG. 7, a lithium ion secondary battery 12 is formed by housing a power generation element 13 in a battery can 9 and sealing the open end of the battery can 9 with a sealing cap 14. The battery can 9 used in the lithium ion secondary battery 12 is manufactured as described below using a clad material obtained by joining an aluminum material and an iron material.
[0056]
A 200 μm thick aluminum alloy (equivalent to JIS-A3003) is used for the first layer as the cladding material, and a SPCE material having a thickness of 250 μm and a carbon content of 0.03 wt% is used for the second layer. Then, nickel plating is applied to both sides to a thickness of 3.5 μm and heat treatment is performed, and then the aluminum material of the first layer is superposed and pressure-rolled to form a clad material having a thickness of 450 μm.
[0057]
The clad material is cut into a circular shape, and is drawn into a cup-shaped intermediate product by a press machine so that the inner surface side of the battery can is an aluminum alloy and the outer surface side is an SPCE material. In this state, there is almost no change in the bottom thickness and side thickness from the original cladding material. The cup-shaped intermediate product 5 formed in this way is sent to a DI processing step similar to that shown in FIG. 2, and is formed into a bottomed rectangular tube having a predetermined height by drawing and squeezing. In the state where DI processing is performed, the bottom size is 22 × 8 mm and the height is 52 mm, and the opening end side is not flat but undulated, so that the set height dimension of the battery can is 48 mm. Cut the ear on the open end side.
[0058]
FIG. 8 shows the cross-sectional shape of the prismatic battery can 9 manufactured by the above processing method. The bottom surface 9a has a thickness of 450 μm, and the side peripheral surface 9b has a thickness of 200 μm. The side surface thickness ratio is 2.25, and the squeeze rate is 56%. Moreover, the opening end side peripheral surface 6c of the battery can 9 is formed to 250 μm which is 30% thicker than the side peripheral surface 6b, thereby improving the sealing strength of the opening end.
[0059]
Further, the corner portion rising from the bottom surface 9a to the side peripheral surface 9b is formed as a curved surface having a curvature radius of 0.35 mm. Increasing the radius of curvature can increase the strength of the battery can 9. However, in order to secure an effective volume of the power generation element accommodated in the battery can 9, it is desirable that the radius of curvature is small, In consideration of securing the volume, the radius of curvature must be 0.5 mm or less.
[0060]
In order to manufacture a lithium ion secondary battery using the battery can 9 configured as described above, a power generation element as shown below is accommodated in the battery can 9.
[0061]
The positive electrode is made by mixing LiCoO2, which is a conductive agent, acetylene black, fluororesin, which is a binder, and the like, pasted on an aluminum foil substrate, and then dried, pressed and cut to a predetermined size. Form a plate. The negative electrode is made by adding a styrene butadiene rubber binder, carboxymethyl cellulose thickener, etc. to a spherical graphite and pasting it into a copper foil substrate, drying it, pressurizing it, and cutting it to a predetermined size. Form on a plate. These positive electrode plate and negative electrode plate are wound through a separator formed of a polyethylene microporous film, accommodated in a battery can 9, and a sealing cap used as a negative electrode terminal of the lithium ion secondary battery and the negative electrode plate are connected with leads. While connecting, the battery can 9 used as a positive electrode terminal is connected with a lead. Into the battery can 9, an electrolyte solution in which lithium hexafluorophosphate having a concentration of 1 mol / 1 is dissolved is injected into a mixture of ethylene carbonate and diethyl carbonate in a molar ratio of 1: 3. A sealing cap 14 is arranged at the end, and the space between the battery can 9 and the sealing cap 14 is sealed with a laser sealing.
[0062]
The lithium ion secondary battery thus manufactured is a square battery having a width of 22 mm, a thickness of 8 mm, and a height of 48 mm. The battery weight is about 18 g and the battery capacity is 610 mAh. In order to verify the effectiveness of this battery, a lithium ion secondary battery of the same standard was manufactured as a comparative example using a conventional battery can made of a single material.
[0063]
Since the comparative example is formed to have the same outer diameter as the battery can 9 using a single material of an aluminum alloy (equivalent to JIS-A3003) that has been used conventionally, the thickness of the side peripheral surface is from the viewpoint of pressure resistance strength. A battery can was produced with a uniform thickness of 500 μm, which required a thickness of 500 μm or more and a bottom surface thickness / side circumferential surface thickness ratio of 1, and a lithium-ion secondary battery was produced by accommodating the power generation element in the same manner as described above. This battery had a battery weight of 17 g and a battery capacity of 550 mAh.
[0064]
As for the battery weight, the comparative example in which the battery can is formed of a single aluminum material is more advantageous, but the battery of the example using the battery can 9 formed of the clad material has a large battery can volume and a large battery capacity. It was revealed that the volume energy density increased by 10% and the weight energy density increased by 5%.
[0065]
Each of the embodiments described above shows an example applied to a cylindrical battery and a rectangular secondary battery. However, the secondary battery is the most severe in deformation due to an increase in battery internal pressure due to charging or the like, and the pressure resistance strength of the sealing portion. These were subject to application as subject to various conditions. Therefore, it is clear that the present invention may be applied to a primary battery whose application conditions are gentler.
[0066]
In addition, stainless steel can be used as the iron-based material constituting the clad material, and the workability in the DI method is slightly inferior to the SPCE material employed in each embodiment, but the pressure strength and corrosion resistance can be improved. As stainless steel, SUS304, SUS430 and the like are suitable.
[0067]
【The invention's effect】
As described above, according to the present invention, the clad material obtained by joining the aluminum-based material and the iron-based material is adjusted so that the bottom surface thickness / side peripheral surface thickness ratio is 1.2 to 5.0 by the DI method. The battery can is formed, so the battery can be configured using a battery can that achieves both the weight reduction by the aluminum-based material and the rigidity by the iron-based material. Thus, it is possible to provide a battery that realizes both an improvement in volumetric energy due to an increase in the amount of storage and an improvement in weight energy density due to weight reduction.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a nickel metal hydride storage battery according to a first embodiment.
FIG. 2 is a schematic sectional view showing a configuration of a DI method.
FIG. 3 is a cross-sectional view showing a configuration of a cylindrical battery can.
FIG. 4 is a cross-sectional view obtained by a metal microscope at a corner portion of a battery can.
FIG. 5 is a surface view obtained by a scanning electron microscope on an inner peripheral surface of a battery can.
FIG. 6 is a cross-sectional view obtained by a scanning electron microscope on a side peripheral surface of a battery can.
FIG. 7 is a cross-sectional view showing a schematic configuration of a lithium ion secondary battery according to a second embodiment.
FIG. 8 is a cross-sectional view showing a configuration of a rectangular battery can.
[Explanation of symbols]
1 Nickel metal hydride storage battery
2 Power generation elements
6 Battery can (cylindrical)
9 Battery can (square)
6a, 9a Bottom
6b, 9b side peripheral surface
6c, 9c Open end side peripheral surface
12 Lithium ion secondary battery
13 Power generation elements

Claims (15)

In a battery in which a power generation element is housed in a bottomed cylindrical battery can, the battery can is mainly composed of aluminum or an aluminum-based alloy and iron or iron-based first layer. the clad material and a second layer formed by an alloy, Ri Na is formed as the bottom thickness / side peripheral surface thickness ratio is 1.2 to 5.0, wherein the battery can is the A battery characterized in that the first layer is formed in a bottomed cylindrical shape with the outer surface side . The battery according to claim 1, wherein the first layer is formed of an aluminum alloy containing 0.5 to 2.5 wt% manganese in aluminum. The battery according to claim 1, wherein the second layer is carbon steel for cold rolling having a carbon content of 0.1 wt% or less. The battery according to claim 1 or 3, wherein the second layer is carbon steel for cold rolling having a carbon content of 0.1 wt% or less and a content of at least one of titanium and niobium of 0.1 wt% or less. . The battery according to claim 1, wherein the second layer is stainless steel. 6. The battery according to claim 1, wherein each of the first and second layers has a thickness of 10 to 300 μm and a thickness of 20 to 600 μm when used as a clad material. The battery according to claim 1, wherein nickel layers are provided on both surfaces or one surface of the first layer and / or the second layer. The battery according to claim 7, wherein the nickel layer is formed to have a thickness of 0.5 to 10 μm after canning. The battery according to any one of claims 1 to 8 , wherein a large number of fine grooves are formed in the cylinder forming direction on the inner surface side of the side peripheral surface. Claim 7 or 8 minute grooves are formed only on the surface of the nickel layer, 9 battery according. The battery according to any one of claims 1 to 10 , wherein a thickness of the side peripheral surface on the opening end side of the battery can is 10% or more thicker than other side peripheral surfaces. Outer diameter of the battery can is formed in the following cylinder with bottom 35 mm, the side peripheral surface of the opening end side, formed by thickly formed over 30% than the thickness of the other side circumference one of claims 1 to 11 A battery according to any one of the above. The battery according to any one of claims 1 to 12 , wherein a rising part from the bottom surface to the side peripheral surface of the battery can formed in a bottomed cylindrical shape is formed on a curved surface having a curvature radius of 0.5 mm or less. In a method for manufacturing a battery can containing a power generation element, the battery can includes a first layer formed of aluminum or an alloy mainly composed of aluminum, and a second layer formed of iron or an alloy mainly composed of iron. After the clad material is formed into a cup-shaped intermediate product with the first layer on the outer surface side by drawing with a press machine, the bottom thickness is measured by a DI method in which the cup-shaped intermediate product is squeezed using a drawing die and a squeeze die. / Battery can manufacturing method characterized by forming in bottomed cylindrical shape with side peripheral surface thickness of 1.2 to 5.0. The method for producing a battery can according to claim 14 , wherein the ironing is continuously performed in one step so that the squealing rate by the DI method is in a range of 20 to 90%.

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