Tabular steel sheet for battery cans, battery can, cylindrical battery, manufacturing method of tabular steel sheet for battery cans, manufacturing method of battery can and manufacturing method of cylindrical battery

Abstract

To provide a cylindrical battery suppressing use of an insulation component and improved in performance.SOLUTION: A tabular steel sheet 40 for battery cans used for a battery can 10 of a cylindrical battery 1 includes a tabular steel sheet 20 and an electro-deposition coating layer 30. The steel sheet 20 includes a first face 21 and a second face 22 at an opposite side of the first face. The electro-deposition coating layer 30 is provided so as to cover only the side of the first face 21 in the side of the first face 21 and the side of the second face 22 of the steel sheet 20. An insulation function is added to the tabular steel sheet 40 for battery cans by the electro-deposition coating layer 30. The battery can 10 and the cylindrical battery 1 using the same are realized using the tabular steel sheet 40 for battery cans to which the insulation function is added. The need of an insulation component such as an outer package label 30a is eliminated, an outer diameter dimension of the battery can 10 is enlarged and battery capacity can be increased thereby.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plate-shaped steel plate for battery cans, a battery can, a cylindrical battery, a method for manufacturing a plate-shaped steel plate for battery cans, a method for manufacturing a battery can, and a method for manufacturing a cylindrical battery. [Background technology]

[0002] A known technology uses an exterior can for housing a battery's power generating element in which an insulating resin layer is formed by baking paint on the outer peripheral surface of a steel plate molded into a bottomed cylindrical shape (Patent Document 1).

[0003] Also, a technique is known in which a conductive agent-containing resin coating is formed on the surface of a Ni-plated cold-rolled steel sheet via a chemical conversion coating, and the coating surface is processed with the coating surface facing inward (Patent Document 2). Also, a technique is known in which synthetic resin powder is applied to the outer surface of a steel exterior case body formed from a steel plate into a cylindrical shape with a bottom, using a cloud-type electrostatic coating method or the like (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-149908 [Patent Document 2] Japanese Patent Application Publication No. 8-287885 [Patent Document 3] JP 2002-367575 A Summary of the Invention [Problem to be solved by the invention]

[0005] With regard to cylindrical batteries, a technique is known in which an insulating exterior label is attached to the outer periphery of the battery can and an insulating washer is attached to insulate the battery can from the adjacent terminals. On the other hand, the outer diameter of a cylindrical battery is determined by the specifications of the cylindrical battery, but this dimension includes the thickness of the exterior label provided on the outer periphery of the battery can. Therefore, the maximum outer diameter of the battery can of a cylindrical battery is restricted by the thickness of the exterior label. Increasing the outer diameter of the battery can increases the internal volume, making it possible to increase the battery capacity. However, in a configuration in which an exterior label is provided on the outer periphery of the battery can, the thickness of the exterior label restricts the expansion of the outer diameter of the battery can and the resulting increase in battery capacity, which may prevent further improvement in the performance of the cylindrical battery.

[0006] In addition, plastics are used for insulating parts such as the exterior labels and insulating washers used to ensure the insulation of cylindrical batteries. In light of the recent demand for reducing plastic use, reducing plastic parts and the plastic waste generated during their production is one of the social challenges.

[0007] In one aspect, the present invention aims to realize a cylindrical battery that uses less insulating parts and has excellent performance. [Means for solving the problem]

[0008] In one aspect, there is provided a plate-shaped steel plate for a battery can used for a cylindrical battery, the plate-shaped steel plate for a battery can comprising: a plate-shaped steel plate having a first surface and a second surface opposite to the first surface; and an electrochemical coating layer arranged so as to cover only the first surface side of the first surface side and the second surface side of the steel plate.

[0009] In another aspect, there is provided a battery can using the plate-shaped steel sheet for a battery can, and a cylindrical battery using the battery can. In still another aspect, there are provided a method for manufacturing a plate-shaped steel plate for a battery can, a method for manufacturing a battery can using the plate-shaped steel plate for a battery can, and a method for manufacturing a cylindrical battery using the battery can. Effect of the Invention

[0010] In one aspect, a plate-shaped steel plate for a battery can having an insulating function is realized. Such a plate-shaped steel plate for a battery can is used to realize a battery can for a cylindrical battery, and a cylindrical battery using the battery can is realized.

[0011] By using a plate-shaped steel sheet for battery cans to which an insulating function has been added, it is possible to reduce the use of insulating parts and realize a cylindrical battery with excellent performance. [Brief description of the drawings]

[0012] [Figure 1] 1A and 1B are diagrams illustrating an example of the configuration of a cylindrical battery. [Diagram 2] FIG. 2 is a diagram illustrating the formation of a surface treatment layer after processing of a plate-shaped steel sheet for a battery can. [Diagram 3] FIG. 1 is a diagram illustrating an example of a cylindrical battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Known cylindrical batteries include primary batteries such as alkaline batteries, manganese batteries, lithium batteries, and nickel-cadmium batteries, and secondary batteries such as lithium-ion batteries. Conventionally, cylindrical batteries have an insulating exterior label made of PET (polyethylene terephthalate) or PVC (polyvinyl chloride) attached to the outer periphery of a bottomed cylindrical battery can in which a power generating element is housed, and an insulating washer is generally attached to insulate the battery can from the adjacent terminal. Since the entire battery can of a cylindrical battery is made of metal and has electrical conductivity, without these insulating parts, a short circuit may occur due to electrical conduction at a location other than the contact terminal surface with the device to which the cylindrical battery is applied. A short circuit not only causes the battery to lose its characteristics, but also causes heat generation, leakage, explosion, and other dangers for users. For this reason, insulating parts such as an exterior label and an insulating washer are used in conventional cylindrical batteries to ensure insulation at specific locations.

[0014] On the other hand, the battery capacity of a cylindrical battery is solely proportional to its internal volume, and increasing the internal volume is an effective way to develop a high-capacity battery. Since the length of a cylindrical battery is somewhat restricted due to terminal contact with the device to which the cylindrical battery is applied, expanding the battery in the direction of the outer diameter is an extremely effective way to increase the internal volume.

[0015] However, even if the battery can is expanded in the outer diameter direction to increase the internal volume of a cylindrical battery, the expansion is limited by the thickness of the exterior label attached to the outer circumference. That is, the outer diameter of a cylindrical battery is determined by the specifications of the cylindrical battery, but the dimension includes the thickness of the exterior label attached to the outer circumference of the battery can. Therefore, the maximum outer diameter of the battery can of a cylindrical battery is restricted by the thickness of the exterior label. The outer diameter of a cylindrical battery is the outer diameter of the battery can plus the thickness of two exterior labels, and at the overlapping portion of the edge of the exterior labels, the thickness of three exterior labels is added (this is the maximum outer diameter of a cylindrical battery).

[0016] In this way, in a configuration in which an exterior label is provided on the outer periphery of the battery can, the thickness of the label is a constraint, which limits the expansion of the outer diameter of the battery can and therefore the increase in battery capacity, and may prevent further performance improvements of cylindrical batteries.

[0017] Plastics are also used for insulating parts such as exterior labels and insulating washers. It is known that the production of such insulating parts generates waste such as label mounts and resin runners. In recent years, there has been a demand to reduce the amount of plastic used and disposed of, and reducing plastic parts and the plastic waste generated during their production is one of the social challenges.

[0018] In view of the above, the configuration described below as an embodiment is adopted to realize a cylindrical battery that uses less insulating parts and has excellent performance. Fig. 1 is a diagram for explaining a configuration example of a cylindrical battery, which diagrammatically shows a cross-sectional view of the essential parts of each battery can and its surface layer of two types of cylindrical batteries according to a conventional example and an embodiment.

[0019] First, one cylindrical battery 1a (left side) shown in FIG. 1 will be described. This cylindrical battery 1a is an example of a cylindrical battery according to a conventional example. The cylindrical battery 1a includes a battery can 10a formed of a steel plate 20a, for example, a plated steel plate having a surface plated with nickel or the like. For convenience, in FIG. 1, when a plated steel plate is used for the steel plate 20a, a plated layer formed on the surface of the steel plate is illustrated by a dotted line as a plated layer 23a. Although not illustrated here, the battery can 10a is cylindrical with a bottom, and a power generating element, for example, a power generating element including a positive electrode layer, a negative electrode layer, a separator interposed between them, and an electrolyte, is accommodated on the inner periphery of the battery can 10a.

[0020] In the cylindrical battery 1a, an insulating exterior label 30a is provided as a surface layer on the outer periphery of the battery can 10a, i.e., on the surface of the steel plate 20a. The exterior label 30a prevents electrical conduction and short circuits at locations other than the contact terminal surface with the device to which the cylindrical battery 1a is applied. For example, a film of PET, PVC, or the like having a thickness of about 160 μm is used for the exterior label 30a.

[0021] The cylindrical battery 1a according to the conventional example is manufactured, for example, by the following method. First, a plate-shaped steel plate 20a is prepared. The prepared steel plate 20a is processed into a bottomed cylindrical shape by pressing to manufacture a battery can 10a (e.g., a positive electrode). A power generating element is accommodated in the inner periphery of the manufactured battery can 10a, and the opening of the battery can 10a is sealed with a sealing body (e.g., a negative electrode). As an example, the positive electrode layer of the power generating element is electrically connected to the battery can 10a, and the negative electrode layer of the power generating element is electrically connected to the sealing body. Then, an exterior label 30a is attached to the outer periphery of the battery can 10a. For example, such a method is used to manufacture a cylindrical battery 1a. The cylindrical battery 1a (left side) in FIG. 1 shows a schematic cross-sectional view of a part of the battery can 10a of the cylindrical battery 1a manufactured in this way and the exterior label 30a, which is its surface layer.

[0022] Next, the other cylindrical battery 1 (right side) shown in FIG. 1 will be described. This cylindrical battery 1 is an example of a cylindrical battery according to the embodiment. The cylindrical battery 1 includes a battery can 10 formed of a battery can-shaped steel plate 40. Although not shown here, the battery can 10 is cylindrical with a bottom, and the inner periphery of the battery can 10 contains a power generating element, for example, a power generating element including a positive electrode layer, a negative electrode layer, a separator interposed between them, and an electrolyte.

[0023] The plate-shaped steel sheet 40 for a battery can includes a steel sheet 20 and an electrodeposition coating layer 30 provided on the surface thereof. The steel sheet 20 of the plate-shaped steel sheet 40 for battery cans is, for example, a plated steel sheet having a surface plated with nickel or the like. For convenience, in FIG. 1, when a plated steel sheet is used for the steel sheet 20, a plated layer formed on the surface is illustrated by a dotted line as a plated layer 23. The steel sheet 20 has a first surface 21 and a second surface 22 opposite to the first surface 21. The first surface 21 of the steel sheet 20 is the surface that becomes the outer periphery side of the battery can 10 of the cylindrical battery 1, and the second surface 22 of the steel sheet 20 is the surface that becomes the inner periphery side of the battery can 10 of the cylindrical battery 1. Of the first surface 21 side and the second surface 22 side of the steel sheet 20, an electrodeposition coating layer 30 is provided so as to cover only the first surface 21 side. When a plated steel sheet is used as the steel sheet 20, an electrodeposition coating layer 30 is provided so as to cover the plated layer 23 on the surface.

[0024] The electrodeposition coating layer 30 of the plate-shaped steel plate 40 for battery cans is a layer applied to the first surface 21 side of the steel plate 20 by using an electrodeposition coating method. For example, a cationic electrodeposition coating method is used to form the electrodeposition coating layer 30. The steel plate 20 with the second surface 22 side protected is immersed in a tank containing a water-soluble electrodeposition coating material that conducts electricity, and an electric current is applied to obtain a state in which the electrodeposition coating material is applied only to the first surface 21 side. The applied electrodeposition coating material is dried and baked to obtain the plate-shaped steel plate 40 for battery cans in which the electrodeposition coating layer 30 is formed on the first surface 21 side of the steel plate 20. The electrodeposition coating layer 30 formed on the first surface 21 side of the steel plate 20 has insulating properties. The thickness of the electrodeposition coating layer 30 formed on the first surface 21 side of the steel plate 20 is set to a range of, for example, 1.0 μm to 5.0 μm.

[0025] Furthermore, according to the electrodeposition coating method that utilizes an electrochemical reaction, the reaction can be caused uniformly on the first surface 21 side of the steel plate 20, and an insulating layer, i.e., an electrodeposition coating layer 30, having a highly uniform thickness can be formed compared to an insulating layer formed by applying an insulating resin.

[0026] A surface treatment layer 50 may be provided on the surface of the battery can plate-shaped steel plate 40 of the battery can 10. The surface treatment layer 50 has insulating properties. Here, the surface treatment layer 50 includes a printed layer 51 formed on the surface of the electrodeposition coating layer 30 and a coating layer 52 covering the printed layer 51. The printed layer 51 is a layer on which the exterior design of the cylindrical battery 1 is formed by printing. The thickness of the printed layer 51 is set to, for example, about several μm to several tens of μm. The coating layer 52 is a layer that protects the printed layer 51 from the outside, such as a UV (ultraviolet) coating. The thickness of the coating layer 52 is set to, for example, about 40 μm. The printed layer 51 and the coating layer 52 have insulating properties. Note that the printed layer 51 and the coating layer 52 are only examples, and as the surface treatment layer 50, other layers having insulating properties may be formed together with the printed layer 51 and the coating layer 52, or instead of the printed layer 51 and the coating layer 52.

[0027] The cylindrical battery 1 according to the embodiment is manufactured, for example, by the following method. First, a plate-shaped steel plate 20 is prepared, and the electrodeposition coating layer 30 is formed only on the first surface 21 side of the first surface 21 side and the second surface 22 side, to manufacture a plate-shaped steel plate 40 for a battery can. The manufactured plate-shaped steel plate 40 for a battery can is processed into a bottomed cylindrical shape by press working, to manufacture a battery can 10. At this time, the plate-shaped steel plate 40 for a battery can is processed so that the first surface 21 side on which the electrodeposition coating layer 30 is provided becomes the outer periphery of the bottomed cylindrical shape. This manufactures a bottomed cylindrical battery can 10 (e.g., a positive electrode) with the electrodeposition coating layer 30 provided on the outer periphery side. A surface treatment layer 50, for example, a printed layer 51 and a coating layer 52 are formed on the outer periphery side of the processed battery can 10. A power generating element is accommodated on the inner periphery of the battery can 10 on which the surface treatment layer 50 has been formed, and the opening of the battery can 10 is sealed with a sealing body (e.g., a negative electrode). As an example, the positive electrode layer of the power generating element is electrically connected to the battery can 10, and the negative electrode layer of the power generating element is electrically connected to the sealing body. For example, such a method is used to manufacture a cylindrical battery 1. The cylindrical battery 1 (right side) in FIG. 1 shows a schematic cross-sectional view of a part of a plate-shaped steel plate 40 for a battery can (steel plate 20 and electrodeposition coating layer 30) of the battery can 10 of the cylindrical battery 1 manufactured in this manner, and its surface treatment layer 50 (printed layer 51 and coating layer 52).

[0028] As described above, of the cylindrical battery 1a and cylindrical battery 1 shown in Fig. 1, the cylindrical battery 1a according to the conventional example has a relatively thick exterior label 30a provided on the surface of the steel plate 20a on the outer periphery of the battery can 10a. The outer diameter of the cylindrical battery 1a is the outer diameter of the battery can 10a plus the thickness of the exterior label 30a. In other words, the outer diameter of the cylindrical battery 1a is the sum of the thickness of two exterior labels 30a, and the thickness of three exterior labels 30a at the overlapping portions at the ends of the exterior labels 30a.

[0029] In contrast, in the cylindrical battery 1 according to the embodiment, an electrodeposition coating layer 30 is provided on the first surface 21 of the steel plate 20, which is the outer periphery of the battery can 10, and has a thickness of the order of several μm, which is extremely thin compared to the exterior label 30a. A plate-shaped steel plate 40 for a battery can, which includes the steel plate 20 and the electrodeposition coating layer 30, is used to form the battery can 10. The electrodeposition coating layer 30 has insulating properties. Therefore, the electrodeposition coating layer 30 can ensure the insulation properties of the first surface 21 of the steel plate 20. That is, the electrodeposition coating layer 30 imparts an insulating function to the first surface 21 of the steel plate 20. Therefore, the cylindrical battery 1 does not require the exterior label 30a used in the cylindrical battery 1a.

[0030] In this way, in the cylindrical battery 1 according to the embodiment, the use of the electrodeposition coating layer 30 allows the insulating material provided on the outer periphery of the battery can 10 to be made thinner in order to ensure insulation. In the cylindrical battery 1, the thickness of the insulating material provided on the outer periphery of the battery can 10 can be made thinner than the thickness of the exterior label 30a, even when the thickness of the electrodeposition coating layer 30 plus the thickness of the surface treatment layer 50 (printed layer 51 and coat layer 52) provided on the surface is added. In the cylindrical battery 1, the thickness of the insulating material provided on the outer periphery of the battery can 10 can be made thinner, so that the outer diameter of the battery can 10 can be enlarged by the amount shown in FIG. 1 as the battery can outer diameter enlargement allowance 100, compared to the outer diameter of the battery can 10a of a cylindrical battery 1a using the exterior label 30a.

[0031] Therefore, in the cylindrical battery 1 using the electrodeposition coating layer 30, it is possible to increase the internal volume of the battery can 10 compared to the cylindrical battery 1a using the exterior label 30a. By increasing the internal volume of the battery can 10, it is possible to increase the capacity of the power generating element housed therein, thereby increasing the battery capacity, and it is possible to realize a cylindrical battery 1 with excellent performance. Furthermore, in the cylindrical battery 1 using the electrodeposition coating layer 30, the exterior label 30a, which is one of the plastic insulating parts, is not required, so it is possible to reduce the plastic material used for the exterior label 30a and the plastic waste generated during its production process. Therefore, in the cylindrical battery 1 using the electrodeposition coating layer 30, it is possible to reduce the cost required for producing plastic parts and reduce the environmental load.

[0032] Furthermore, in a cylindrical battery 1 using the electrodeposition coating layer 30, insulation is ensured by the electrodeposition coating layer 30 of the battery can 10 (plate-shaped steel plate 40 for battery can), making it possible to eliminate the need for plastic insulating parts such as insulating washers to prevent short circuits between the battery can 10 and other parts. This makes it possible to reduce the plastic material used in insulating washers and the plastic waste generated during the production process, thereby reducing the costs required for producing plastic parts and reducing the environmental impact.

[0033] By obtaining a battery can 10 using a plate-shaped steel plate 40 for a battery can, which includes a steel plate 20 and an electrocoating layer 30 provided on the first surface 21 side of the steel plate 20, a cylindrical battery 1 with excellent performance is realized while reducing the use of insulating parts.

[0034] In the manufacture of the cylindrical battery 1, the plate-shaped steel plate 40 for a battery can, which has the electrodeposition coating layer 30 provided on the first surface 21 side of the plate-shaped steel plate 20, is processed, for example, by pressing using a multi-stage deep drawing process to manufacture the battery can 10. A surface treatment layer 50 is formed on the outer periphery of the battery can 10 manufactured by processing the plate-shaped steel plate 40 for a battery can in this manner.

[0035] Here, Fig. 2 is a diagram for explaining the formation of a surface treatment layer after processing of a plate steel sheet for a battery can. Fig. 2(A) shows a schematic cross-section of a main part of a plate steel sheet for a battery can before processing. Fig. 2(B) shows a schematic cross-section of a main part of a plate steel sheet for a battery can after processing. Fig. 2(C) shows a schematic cross-section of a main part of a plate steel sheet for a battery can after processing and a surface treatment layer formed on the surface thereof.

[0036] When a deep-drawing press is performed on a plate-shaped steel sheet 40 for a battery can as shown in FIG. 2(A), a valley 41 may be formed in the surface layer of the deep-drawn plate-shaped steel sheet 40 for a battery can, penetrating the electrodeposition coating layer 30 and reaching the steel sheet 20, as shown in FIG. 2(B). For example, when a plated steel sheet is used for the steel sheet 20, a valley 41 may be formed that reaches the plated layer on the surface, or that penetrates the plated layer and reaches the underlying steel sheet. The formation of the valley 41 leads to the occurrence of a portion where the conductive steel sheet 20 is exposed without being covered by the insulating electrodeposition coating layer 30. The partial exposure of the steel sheet 20 due to the valley 41 may increase the risk of causing a short circuit with the outside.

[0037] In the manufacture of the cylindrical battery 1, even when the valleys 41 are formed in the plate-shaped steel plate 40 for a battery can by deep drawing, a surface treatment layer 50 is formed on the surface of the plate-shaped steel plate 40 for a battery can after deep drawing, as shown in FIG. 2(C). That is, an insulating surface treatment layer 50 is formed on the electrodeposition coating layer 30 of the plate-shaped steel plate 40 for a battery can in which the valleys 41 are formed after deep drawing. As a result, the valleys 41 formed in the plate-shaped steel plate 40 for a battery can by deep drawing are covered with the insulating surface treatment layer 50 (its printed layer 51 or coating layer 52). Therefore, partial exposure of the steel plate 20 by the valleys 41 is suppressed, and the risk of causing a short circuit with the outside is reduced. In the plate-shaped steel plate 40 for a battery can, an insulating function is added to the first surface 21 side of the steel plate 20 by the surface treatment layer 50 in addition to the electrodeposition coating layer 30.

[0038] From this viewpoint, it is preferable that the surface treatment layer 50 is formed on the surface of the plate-shaped steel sheet for battery cans 40 after deep drawing rather than before deep drawing. Next, an example of a cylindrical battery will be described.

[0039] Fig. 3 is a diagram for explaining an example of a cylindrical battery. Fig. 3(A) shows an example of a unit cell. Fig. 3(B) shows an example of a cylindrical battery according to a conventional example. Fig. 3(C) shows an example of a cylindrical battery according to the embodiment.

[0040] Figure 3(A) is a schematic diagram showing the appearance of a cell 1b of a conventional cylindrical battery 1a (Figure 3(B)) together with part of its internal structure before an exterior label 30a and an insulating washer 90 are provided. The cell 1b has a power generating element 60 housed inside a battery can 10a (positive electrode) which is manufactured by pressing a steel sheet 20a into a cylindrical shape with a bottom, and the opening of the battery can 10a is sealed with a sealing body 70a (negative electrode).

[0041] Here, the battery can 10a is manufactured by pressing using deep drawing so as to have a positive electrode terminal 2a protruding outward and a recess 11a (beading portion) recessed to the inner periphery. The sealing body 70a has a negative electrode terminal 3a protruding outward. The power generating element 60 is accommodated on the inner periphery of the battery can 10a, and the sealing body 70a is provided with the recess 11a as a seat, and the opening of the battery can 10a is sealed. The space between the battery can 10a and the sealing body 70a is insulated and sealed by an insulating gasket (not shown). The power generating element 60 includes a positive electrode layer 61 and a negative electrode layer 62, a separator 63 interposed therebetween, and an electrolyte (not shown) impregnated therein. The positive electrode layer 61 of the power generating element 60 is electrically connected to the battery can 10a, and the negative electrode layer 62 of the power generating element 60 is electrically connected to the sealing body 70 through a current collector 80 such as a carbon rod inserted therein.

[0042] Fig. 3(B) is a schematic diagram of the appearance of a cylindrical battery 1a according to a conventional example, in which an exterior label 30a is provided on the outer periphery of the unit cell 1b shown in Fig. 3(A), and an insulating washer 90 is provided on the surface on the negative terminal 3a side. For convenience, Fig. 3(B) shows the part corresponding to the unit cell 1b in a schematic diagram using dotted lines. Furthermore, for convenience, Fig. 3(B) shows a schematic diagram of a cross section of a battery can 10a (steel plate 20a) and a portion of the exterior label 30a provided on its outer periphery. The cylindrical battery 1a shown in Fig. 3(B) has a larger outer diameter than the unit cell 1b shown in Fig. 3(A) due to the exterior label 30a provided on the outer periphery.

[0043] Fig. 3(C) is a schematic diagram of the external appearance of a cylindrical battery 1 according to an embodiment. For convenience, Fig. 3(C) shows a portion corresponding to a unit cell (different from the unit cell 1b in Fig. 3(A)) in a schematic diagram using dotted lines. Furthermore, for convenience, Fig. 3(C) shows a schematic diagram of a cross section of a part of a battery can 10 (steel plate 20 and electrodeposition coating layer 30 of a plate-shaped steel plate 40 for a battery can) and a surface treatment layer 50 provided on the outer periphery of the battery can.

[0044] 3(C), a battery can 10 is manufactured by pressing a plate-shaped steel plate 40 for a battery can, which has been manufactured by forming an electrodeposition coating layer 30 only on the first surface 21 side of a plate-shaped steel plate 20, into a bottomed cylindrical shape with the electrodeposition coating layer 30 on the outer periphery side. Then, following the example of the unit cell 1b (FIG. 3(A)), a power generating element (having a configuration similar to the power generating element 60) is housed on the inner periphery side of the manufactured battery can 10 (positive electrode), and the opening of the battery can 10 is sealed with a sealing body 70 (negative electrode).

[0045] Here, the battery can 10 is manufactured by pressing using deep drawing so as to have a positive electrode terminal 2 protruding outward and a recess 11 (beading portion) recessed toward the inner periphery. The electrodeposition coating layer 30 on the surface of the portion of the battery can 10 that will become the positive electrode terminal 2 is removed. A surface treatment layer 50 is formed on the outer periphery of the processed battery can 10. Even if the valley 41 in which the steel plate 20 is exposed as described above is formed in the battery can 10 manufactured by pressing, the valley 41 is covered with the surface treatment layer 50, and the exposure of the steel plate 20 is suppressed. That is, the insulation of the outer periphery of the battery can 10 is ensured. A power generating element is accommodated on the inner periphery of the battery can 10 on which the surface treatment layer 50 is formed, and the opening of the battery can 10 is sealed with a sealing body 70 that is provided with the recess 11 as a seat. The sealing body 70 has a negative electrode terminal 3 protruding outward. The sealing body 70 may be manufactured by pressing a plate-shaped steel plate 40 for a battery can, which has an electrodeposition coating layer 30 formed only on the first surface 21 side of the plate-shaped steel plate 20, in the same manner as the battery can 10. In this case, the electrodeposition coating layer 30 on the surface of the portion that will become the negative electrode terminal 3 is removed. A surface treatment layer 50 may be formed on the surface of the sealing body 70 other than the portion that will become the negative electrode terminal 3. The space between the battery can 10 and the sealing body 70 is insulated and sealed by an insulating gasket (not shown). Following the example of the unit cell 1b (FIG. 3(A)), the positive electrode layer of the power generating element is electrically connected to the battery can 10, and the negative electrode layer of the power generating element is electrically connected to the sealing body 70 through a current collector such as a carbon rod.

[0046] In the cylindrical battery 1 shown in FIG. 3(C), an insulating function is imparted to the first surface 21 of the steel plate 20 by the electrodeposition coating layer 30 provided on the plate-shaped steel plate 40 for a battery can, or by a surface treatment layer 50 further provided on the surface of that.

[0047] In the cylindrical battery 1 shown in FIG. 3(C), a plate-shaped steel plate 40 for a battery can, in which a thin electrodeposition coating layer 30 is provided on the first surface 21 side of the steel plate 20, is used for the battery can 10, making it possible to eliminate the need for a thick exterior label 30a (FIG. 3(B)). This allows the outer diameter dimension of the battery can 10 to be enlarged. This allows the internal volume of the battery can 10 to be increased, and the battery capacity to be increased. Furthermore, in the cylindrical battery 1 shown in FIG. 3(C), in addition to the exterior label 30a, which is a plastic insulating part, the insulating washer 90 is unnecessary. This makes it possible to reduce plastic materials and plastic waste generated in the production process. The use of the plate-shaped steel plate 40 for a battery can reduces the use of insulating parts and realizes a cylindrical battery 1 with excellent performance.

[0048] Next, the results of evaluating the performance of various cylindrical batteries will be described. <Cylindrical battery> As cylindrical batteries, AA alkaline batteries of the following Conventional Example, Comparative Example 1-2, and Example 1-5 were prepared.

[0049] [Conventional example] A power generating element was placed inside the battery can (positive electrode) obtained by pressing a plate-shaped steel sheet using a multi-stage deep drawing process, the opening was sealed with a sealant (negative electrode), a 160 μm thick PET label was attached to the outer periphery of the battery can as an exterior label (exterior), and a 200 μm thick insulating washer (exterior) was attached to the sealant side, resulting in a conventional AA alkaline battery.

[0050] Comparative Example 1 A plate-shaped steel sheet was subjected to a press working using a multi-stage deep drawing process to obtain a battery can (positive electrode) having an outer diameter equivalent to that (including the outer label) of an AA alkaline battery having an outer label of the conventional example, i.e., an enlarged outer dimension. A larger power generating element than that of the conventional example was housed on the inner periphery of the obtained battery can, and the opening was sealed with a sealer (negative electrode), to obtain an AA alkaline battery of Comparative Example 1. The AA alkaline battery of Comparative Example 1 corresponds to the unit cell of the AA alkaline batteries of Comparative Example 2 and Examples 1-5.

[0051] Comparative Example 2 A plate-shaped steel plate for a battery can, which had a 1.0 μm-thick electrodeposition coating layer (exterior) formed on only one side of the plate-shaped steel plate by cationic electrodeposition coating, was subjected to press working by multi-stage deep drawing so that the electrodeposition coating layer was on the outer periphery side, to obtain a battery can (positive electrode) having an outer diameter dimension equivalent to that of Comparative Example 1. A larger power generating element than that of the conventional example was accommodated on the inner periphery side of the obtained battery can, and the opening was sealed with a sealer (negative electrode), to obtain an AA alkaline battery of Comparative Example 2.

[0052] Example 1 A battery can plate-shaped steel plate having an electrodeposition coating layer (exterior) of 1.0 μm thick formed only on one side of the plate-shaped steel plate by cationic electrodeposition coating method was subjected to press working by multi-stage deep drawing so that the electrodeposition coating layer was on the outer periphery side, and a battery can (positive electrode) having an outer diameter dimension equivalent to that of Comparative Example 1-2 was obtained. A UV coat (about 40 μm thick) was formed by spraying and solidifying a UV resin on the outer periphery side of the obtained battery can. A larger power generating element than that of the conventional example was accommodated on the inner periphery side of the battery can after the UV coat was formed, and the opening was sealed with a sealing body (negative electrode), and a AA alkaline battery of Example 1 was obtained.

[0053] Example 2 An AA alkaline battery of Example 2 was obtained in the same manner as in Example 1, except that a plate-shaped steel plate for a battery can was used, in which a 2.0 μm-thick electrodeposition coating layer (exterior) was provided on only one side of the plate-shaped steel plate by a cathodic electrodeposition coating method.

[0054] Example 3 An AA alkaline battery of Example 3 was obtained in the same manner as in Example 1, except that a plate-shaped steel plate for a battery can was used, in which a 3.0 μm-thick electrodeposition coating layer (exterior) was provided on only one side of the plate-shaped steel plate by a cathodic electrodeposition coating method.

[0055] Example 4 An AA alkaline battery of Example 4 was obtained in the same manner as in Example 1, except that a plate-shaped steel plate for a battery can was used, in which a 4.0 μm-thick electrodeposition coating layer (exterior) was provided on only one side of the plate-shaped steel plate by a cathodic electrodeposition coating method.

[0056] Example 5 An AA alkaline battery of Example 5 was obtained in the same manner as in Example 1, except that a plate-shaped steel plate for a battery can was used, in which a 5.0 μm-thick electrodeposition coating layer (exterior) was provided on only one side of the plate-shaped steel plate by a cathodic electrodeposition coating method.

[0057] <Performance evaluation> The following Test 1-3 was carried out on the AA alkaline batteries (cylindrical batteries) of the above Conventional Example, Comparative Example 1-2, and Example 1-5 to evaluate their performance.

[0058] [Test 1] External short circuit test (parallel arrangement) Here, we checked whether the conduction of the side of the battery would cause a drop in battery voltage or heat generation. For the test, we assumed a battery case that uses four batteries, arranged the batteries side by side, fixed them with tape, and left them for 24 hours. In Table 1, cases where there was no voltage drop or heat generation are marked as "O," and cases where there was a voltage drop or heat generation are marked as "X."

[0059] [Test 2] External short circuit test (removed from the device) It was confirmed whether the side of the battery would be scratched or peeled off when inserted into and removed from the device, and whether any electrical continuity would occur as a result. The test involved inserting and removing the battery from the device 30 times, and checking whether there were any scratches or peeling on the side of the battery or any external short circuit caused by these. In Table 1, those without scratches or peeling are marked with "O", and those with scratches or peeling or any external short circuit caused by these are marked with "X".

[0060] [Test 3] Battery capacity measurement The battery capacities were compared by measuring the discharge capacity. For the test, a method was adopted in which the discharge capacity was measured by constant current continuous discharge. In Table 1, the battery capacity of the conventional example is set to 100%, and the ratio of the battery capacity of Comparative Example 1-2 and Example 1-5 to it is shown.

[0061] The results of Tests 1-3 carried out on the AA alkaline batteries of Conventional Example, Comparative Example 1-2 and Example 1-5 are shown in Table 1.

[0062] [Table 1]

[0063] In the AA alkaline battery of Comparative Example 1, which was not provided with an exterior and a UV coating, the battery capacity was increased compared to the conventional AA alkaline battery by enlarging the outer diameter of the battery can and enlarging the size of the power generating element contained therein. However, in the external short circuit test (parallel arrangement) in Test 1, it was determined that there was a voltage drop or heat generation, and in the external short circuit test (removal) in Test 2, it was determined that there was a scratch or peeling, or an external short circuit caused by the above.

[0064] In the AA alkaline battery of Comparative Example 2, which had a 1.0 μm thick electrodeposition coating layer as an exterior and no UV coating, the battery capacity was increased compared to the conventional AA alkaline battery by enlarging the outer diameter of the battery can and enlarging the size of the power generating element contained therein. In the external short circuit test (parallel arrangement) in Test 1, it was determined that there was no voltage drop or heat generation. However, in the external short circuit test (removal) in Test 2, it was determined that there was a scratch or peeling, or an external short circuit caused by the scratch or peeling.

[0065] In the AA alkaline battery of Example 1, which has an exterior electrodeposition coating layer of 1.0 μm thickness and further has a UV coating, the battery capacity was increased compared to the conventional AA alkaline battery by enlarging the outer diameter of the battery can and enlarging the size of the power generating element contained therein. In the external short circuit test (parallel arrangement) in Test 1, it was determined that there was no voltage drop or heat generation, and in the external short circuit test (removal) in Test 2, it was determined that there was no scratch or peeling.

[0066] The AA alkaline batteries of Examples 2-5, which were provided with an electrodeposition coating layer having a thickness of 2.0 μm-5.0 μm as an exterior and further provided with a UV coating, also obtained results similar to those of Example 1. That is, the battery capacity was higher than that of the conventional AA alkaline batteries, and in the external short circuit test (parallel arrangement) in Test 1, it was determined that there was no voltage drop or heat generation, and in the external short circuit test (removal) in Test 2, it was determined that there was no scratch or peeling.

[0067] From the results of Examples 1 to 5 in Table 1, it was confirmed that by obtaining a battery can with larger external dimensions by using a plate-shaped steel sheet for a battery can provided with an electrodeposition coating layer, and further providing a UV coating on the obtained battery can, it is possible to obtain an AA alkaline battery with high battery capacity and in which external short circuits are effectively suppressed. Note that, although Comparative Example 2 is a battery can without a UV coating here, even the AA alkaline battery of Comparative Example 2 can obtain the effect of improving battery capacity and can obtain a certain degree of the effect of suppressing external short circuits. [Explanation of symbols]

[0068] 1, 1a cylindrical battery 1b Cell 2, 2a positive terminal 3, 3a negative terminal 10, 10a battery can 11, 11a recess 20, 20a steel plate 21 Page 1 22 Side 2 23, 23a plating layer 30 Electrochemical coating layer 30a Exterior label 40. Steel sheets for battery cans 41 Valley 50 Surface treatment layer 51 Printing layer 52 Coating layer 60 Power generation elements 61 Positive electrode layer 62 Negative electrode layer 63 Separator 70, 70a sealing body 80 Current collector 90 Insulating washer 100 Increase the outer diameter of the battery can

Claims

1. A plate-shaped steel sheet for a battery can used for a cylindrical battery, A plate-shaped steel plate having a first surface and a second surface opposite to the first surface; An electrodeposition coating layer provided so as to cover only the first surface side of the first surface side and the second surface side of the steel sheet; and a plate-shaped steel sheet for battery cans.

2. the steel sheet has a plating layer on the first surface side, The plate-shaped steel sheet for battery cans according to claim 1 , wherein the electrodeposition coating layer is provided so as to cover the plating layer.

3. A battery can for a cylindrical battery using the plate-shaped steel sheet for battery cans according to claim 1 or 2, The plate-shaped steel sheet for a battery can is processed so that the first surface side on which the electrodeposition coating layer is provided becomes the outer periphery side of a bottomed cylindrical can.

4. The battery can according to claim 3 , further comprising a surface treatment layer provided so as to cover the electrodeposition coating layer.

5. A cylindrical battery using the battery can according to claim 3 or 4.

6. A method for manufacturing a plate-shaped steel sheet for a battery can used for a cylindrical battery, comprising: A step of preparing a steel plate having a first surface and a second surface opposite to the first surface; forming an electrodeposition coating layer so as to cover only the first surface side of the first surface side and the second surface side of the steel sheet; The method for producing a plate-shaped steel sheet for a battery can, comprising:

7. A method for manufacturing a battery can of a cylindrical battery, comprising the steps of: A method for manufacturing a battery can, comprising a step of processing the plate-shaped steel sheet for a battery can according to claim 1 or 2 so that the first surface side on which the electrodeposition coating layer is provided becomes an outer periphery side of a bottomed cylinder.

8. The method for producing a battery can according to claim 7 , further comprising the step of forming a surface treatment layer covering the electrodeposition coating layer after the step of processing the plate-shaped steel sheet for a battery can.

9. A method for manufacturing a cylindrical battery, comprising: A method for manufacturing a cylindrical battery using the battery can according to claim 3 or 4.

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