Battery can and battery using same

Abstract

This battery can 10 comprises a bottom part 13, a cylindrical middle part 14 extending from the bottom part 13, and an opening part 16 continuous with the middle part 14. The opening part 16 includes: an end surface 16p formed by a surface 22 of a base material that does not have a plating layer 20; a peripheral wall section 16w continuous with the middle part 14; and a folding section 16t that is a section including the end surface 16p and folded inside the battery can 10 so as to overlap the peripheral wall section 16w. When the thickness of the folding section 16t at the position of the end surface 16p is defined as T1, the thickness of the peripheral wall section 16w at the position closest from the end surface 16p is defined as T2, and the thickness of the middle part 14 is defined as T3, the total of the thickness T1 and the thickness T2 is less than twice the thickness T3.

Description

Battery can and battery using the same

[0001] The present disclosure relates to a battery can and a battery using the same.

[0002] For batteries such as lithium ion secondary batteries, nickel hydrogen batteries, and alkaline batteries, metal battery cans are widely used.

[0003] Patent Document 1 describes an example of a method for manufacturing a battery can. The battery can is manufactured using a steel sheet having a plating layer. After forming the steel sheet into the shape of a battery can by drawing, a trimming process is performed on the opening.

[0004] Patent Document 2 describes a battery can in which the end surface of the peripheral side wall is folded in a loop shape extending inward to form an annular shoulder surrounding the opening.

[0005] JP-A-2004-220863 JP-A-2019-153580

[0006] As described in Patent Document 1, when trimming the opening, the plating layer is removed and the base material of the steel sheet is exposed on the surface. When the base material of the steel sheet, that is, steel, is exposed on the surface, the exposed portion may come into contact with an electrolytic solution, condensed water, or air, resulting in rust.

[0007] As described in Patent Document 1, if the plating layer is reformed after the trimming process, the occurrence of rust can be prevented. However, since it is complicated to perform a plating process on each of the battery cans formed into a predetermined shape, such a method is difficult to adopt from the viewpoints of cost and mass productivity.

[0008] As described in Patent Document 2, if the opening where the base material of the steel sheet is exposed is folded inward, when the battery is assembled, it becomes difficult for the exposed portion to come into contact with an electrolytic solution, condensed water, or air, and the occurrence of rust can be reduced. However, as described in Patent Document 2, a battery can in which the opening is simply folded inward has a large thickness. When a sealing body provided with a gasket is caulked and fixed to such a battery can, the gasket is strongly pressed against the opening. As a result, a sufficient thickness of the gasket cannot be ensured, and there is a risk of short circuit.

[0009] This disclosure provides a battery can and a battery using the same that can achieve both suppression of rust formation and assurance of battery reliability with a simple configuration.

[0010] A battery can is provided comprising: a bottom portion; a cylindrical body portion extending from the bottom portion; and an opening continuing from the body portion, wherein the opening includes an end face formed by the surface of a base material without a plating layer, a peripheral wall portion continuing from the body portion, and a folded portion including the end face that is folded inward into the battery can so as to overlap the peripheral wall portion, and when the thickness of the folded portion at the position of the end face is defined as T1, the thickness of the peripheral wall portion at the position closest to the end face is defined as T2, and the thickness of the body portion is defined as T3, the sum of the thickness T1 and the thickness T2 is less than twice the thickness T3.

[0011] The technology disclosed herein provides a battery can and a battery using the same that can achieve both suppression of rust formation and assurance of battery reliability with a simple configuration.

[0012] Figure 1 is a cross-sectional view of a battery can according to Embodiment 1. Figure 2 is a partially enlarged view of Figure 1. Figure 3 is a process diagram showing a method for manufacturing a battery can. Figure 4 is a cross-sectional view of a battery according to Embodiment 2. Figure 5 is a partially enlarged view of Figure 4. Figure 6A is a diagram illustrating the operation of the battery of this disclosure. Figure 6B is a diagram illustrating the operation of a conventional battery. Figure 7 is a process diagram showing a method for manufacturing a battery. Figure 8 is a partially enlarged cross-sectional view of a battery can according to a modified example. Figure 9 is a partially enlarged cross-sectional view of a battery can according to another modified example.

[0013] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0014] (Embodiment 1) Figure 1 is a cross-sectional view of a battery can according to Embodiment 1. Figure 2 is a partially enlarged view of Figure 1. The cross-sections in Figures 1 and 2 are cross-sections that include the central axis O of the battery can 10.

[0015] The battery can 10 is a molded body of a plate-shaped base material 22 with a plating layer 20 on its surface, and comprises a bottom portion 13, a body portion 14, and an opening 16. The plating layer 20 plays a role in suppressing corrosion of the base material 22. The plating layer 20 is, for example, a Ni plating layer. The base material 22 is a metal plate such as a steel plate. The body portion 14 is a cylindrical part that extends vertically from the bottom portion 13. The opening 16 is a part that continues from the body portion 14 and is a part that should be bent inward into the battery can 10 in order to seal the battery can 10 during battery assembly.

[0016] The opening 16 includes an end face 16p, an outer circumferential surface 16q, and an inner circumferential surface 16r. The end face 16p is formed by the surface of the base material 22, which does not have the plating layer 20.

[0017] The opening 16 includes a peripheral wall portion 16w that continues from the body portion 14, and a folding portion 16t that includes an end face 16p and is folded inward into the battery can 10 so as to overlap the peripheral wall portion 16w. The opening 16 is folded at the opening edge 16s. The opening edge 16s connects the peripheral wall portion 16w and the folding portion 16t. The opening 16 is folded such that the inner circumferential surface 16r of the folding portion 16t faces the inner circumferential surface 16r of the peripheral wall portion 16w.

[0018] When the thickness of the folding portion 16t at the end face 16p is defined as T1, the thickness of the peripheral wall portion 16w at the position closest to the end face 16p is defined as T2, and the thickness of the body portion 14 is defined as T3, the sum of thickness T1 and thickness T2 is less than twice the thickness T3. Note that thickness T1 is equal to the width of the end face 16p.

[0019] In the assembly of the battery, the opening 16 is bent so that the opening edge 16s faces inward towards the inside of the battery can 10 in order to seal the battery can 10. Therefore, the outer surface 16q of the peripheral wall portion 16w is the surface that is exposed to the outside in the final product, the battery. The outer surface 16q of the folding portion 16t is the surface that contacts the sealing body in the final product, the battery. In the battery can 10, the opening 16 is folded inward to form the folding portion 16t, so that the end face 16p, which does not have the plating layer 20, is not exposed to the outside in the final product, the battery. As a result, contact between the end face 16p and the electrolyte, condensation, or air is suppressed, and the occurrence of rust can be reduced. Furthermore, even if rust occurs on the end face 16p, it does not affect the appearance because the end face 16p is not exposed to the outside of the battery. With this configuration, there is no need to form a plating layer on the end face 16p again, and the occurrence of rust can be suppressed with a simple configuration.

[0020] Furthermore, in the battery can 10, the sum of thicknesses T1 and T2 is less than twice the thickness T3. Therefore, even when the opening 16 is folded inward to form a folded portion 16t, the overall thickness near the opening edge 16s of the battery can 10 does not become excessive. As a result, when sealing the battery can 10, even when the portion near the opening edge 16s is pressed against the gasket of the sealing body, the gasket does not become too concave, and sufficient thickness is ensured to prevent short circuits. Therefore, the battery can 10 can suppress the occurrence of rust while maintaining the reliability of the battery. The overall thickness near the opening edge 16s is the thickness of the portion that is pressed against the gasket of the sealing body when sealing the battery can 10 with the sealing body.

[0021] It is desirable that at least a portion of the inner circumferential surface 16r of the folding portion 16t is in contact with the inner circumferential surface 16r of the peripheral wall portion 16w, and, as shown in Figure 2, it is even more desirable that the entire inner circumferential surface 16r of the folding portion 16t is in contact with the inner circumferential surface 16r of the peripheral wall portion 16w in the battery can 10. This makes it possible to reduce the thickness of the battery can 10 while still having a folding portion 16t.

[0022] The sum of thicknesses T1 and T2 is preferably 1.5 times or less the thickness T3, more preferably 1.2 times or less, and even more preferably 1.0 times or less. The sum of thicknesses T1 and T2 is, for example, 0.5 times or more and less than 2 times the thickness T3, and may also be 0.8 times or more and 1.5 times or less, 0.8 times or more and 1.2 times or less, or 0.9 times or more and 1.0 times or less. With such a configuration, rust generation can be suppressed with a simple structure without significantly changing the thickness of the battery can 10.

[0023] The opening 16 has a thin-walled region R1 with a thickness less than the thickness T3 and a thick-walled region R2 with a thickness greater than the thin-walled region R1. That is, the opening 16 has a thin-walled region R1 with a thickness less than the thickness T3 and a thick-walled region R2 which is the region other than the thin-walled region R1. In the direction in which the body portion 14 and the opening 16 extend from the bottom portion 13 toward the end face 16p, the thin-walled region R1 is located toward the end face 16p than the thick-walled region R2. The thick-walled region R2 is the portion that continues from the body portion 14 in the opening 15. The thickness of the thick-walled region R2 is typically the same as the thickness T3 of the body portion 14. That is, the opening 16 is composed of a portion having the same thickness as the body portion 14 and a portion including the end face 16p with a reduced thickness compared to the body portion 14. With the above configuration, the area of ​​the end face 16p where the plating layer 20 is not provided can be reduced, so the occurrence of rust can be further reduced. The thickness of the opening 16 is the distance between the outer surface 16q and the inner surface 16r.

[0024] The thickness T1 is adjusted to, for example, a thickness T2 or less. The ratio of thickness T1 to thickness T2 (T1 / T2) may be 80% or less, and even more preferably 50% or less, in percentage terms. The ratio (T1 / T2) is, for example, greater than 0% and 100% or less, preferably greater than 0% and 80% or less, and more preferably greater than 0% and 50% or less. The lower limit of the ratio (T1 / T2) may be 5% or more, and may be 10% or more. By adjusting the ratio (T1 / T2) to such a range, the folding portion 16t can be formed without significantly changing the overall thickness near the opening edge 16s of the battery can 10, while avoiding the complicated process of providing a thin-walled region R1 in the opening 16, and a sufficient rust suppression effect can be obtained.

[0025] The thickness T1 is adjusted to, for example, 80% or less of the thickness T3. By appropriately adjusting the thickness T1, the rust suppression effect and the reliability of the battery are enhanced. The ratio of thickness T1 to thickness T3 (T1 / T3) is, for example, greater than 0% and 80% or less, preferably greater than 0% and 50% or less, in percentage terms. The lower limit of the ratio (T1 / T3) may be 5% or more, or 10% or more. By adjusting the ratio (T1 / T3) to this range, the folding portion 16t can be formed without significantly changing the overall thickness near the opening edge 16s of the battery can 10, while avoiding the complicated process of providing a thin-walled region R1 in the opening 16, and a sufficient rust suppression effect can be obtained.

[0026] In the opening 16 shown in Figure 2, the maximum thickness of the folded portion 16t is less than the thickness T3 of the body portion 14. That is, the entire folded portion 16t is located within the thin-walled region R1. This makes it possible to reduce the overall thickness of the battery can 10 near the opening edge 16s.

[0027] In the opening 16 shown in Figure 2, the thickness T2 is smaller than the thickness T3. Therefore, the entire folded portion 16t and the portion of the peripheral wall portion 16w that overlaps with the folded portion 16t are located within the thin-walled region R1. In other words, the opening 16 is folded within the thin-walled region R1. This makes it possible to reduce the overall thickness of the battery can 10 near the opening edge 16s. Also, because the opening 16 is easy to fold, the inner circumferential surface 16r of the folded portion 16t is more likely to come into contact with the inner circumferential surface 16r of the peripheral wall portion 16w.

[0028] In the opening 16 shown in Figure 2, the thickness T1 is smaller than the thickness T2. In Figure 2, in the thin-walled region R1, the thickness of the opening 16 decreases toward the end face 16p. Therefore, the thickness of the folded portion 16t decreases toward the end face 16p, and the thickness of the peripheral wall portion 16w decreases toward the opening edge 16s from at least the position closest to the end face 16p.

[0029] Specifically, in the opening 16 shown in Figure 2, the inner circumferential surface 16r in the thin-walled region R1 includes a tapered surface 16u that is inclined such that the thickness of the opening 16 decreases toward the end face 16p. The tapered surface 16u is inclined with respect to the outer circumferential surface 16q and the end face 16p. In the battery can 10, the opening 16 is folded inward starting from the tapered surface 16u. Therefore, the tapered surface 16u exists from the circumferential wall portion 16w to the folded portion 16t, and the tapered surface 16u located in the folded portion 16t and the tapered surface 16u located in the circumferential wall portion 16w are opposite each other and in contact. With this configuration, even if the folded portion 16t is formed, the overall thickness near the opening edge 16s of the battery can 10 can be made smaller. In addition, the area of ​​the end face 16p where the plating layer 20 is not provided can be reduced. As a result, the occurrence of rust can be suppressed while maintaining the reliability of the battery.

[0030] The outer circumferential surface 16q is a plated surface formed by the plating layer 20. The inner circumferential surface 16r in the thick-walled region R2 is a plated surface formed by the plating layer 20. The inner circumferential surface 16r in the thin-walled region R1, i.e., the tapered surface 16u, is a surface formed by the surface of the base material 22 where the plating layer 20 is not provided. That is, the portion of the inner circumferential surface 16r excluding the tapered surface 16u is a plated surface formed by the plating layer 20. In the battery can 10, the tapered surface 16u faces the inner circumferential surface 16r of the outer circumferential wall due to the folding of the opening 16, and is less likely to come into contact with the electrolyte, condensation, or air in the final product, the battery. Therefore, the occurrence of rust on the tapered surface 16u can also be suppressed. Furthermore, a battery can 10 with such a configuration may be easy to manufacture.

[0031] The position of the end of the tapered surface 16u on the end face 16p side coincides with the end face 16p. The position of the other end of the tapered surface 16u is not particularly limited. In the opening 16 shown in Figure 2, the length of the tapered surface 16u and the length of the thin-walled region R1 of the opening 16 are the same. The length of the tapered surface 16u is adjusted to a range of, for example, the thickness T3 of the body portion 14 or more and the length of the straight portion 162 (see Figure 5) described later. For example, if the diameter of the body portion 14 is around 21 mm, it is adjusted to a range of 1.0 mm to 1.3 mm. By ensuring an appropriate length of the tapered surface 16u, the process of forming the tapered surface 16u can be avoided. That is, by adjusting the length of the thin-walled region R1 to a range of the thickness T3 of the body portion 14 or more and the length of the straight portion 162 (see Figure 5) described later, the process of forming the thin-walled region R1 in the opening 16 can be avoided. The length of the tapered surface 16u and the length of the thin-walled region R1 refer to the lengths in the direction perpendicular to the thickness direction of the opening 16.

[0032] In the battery can 10, the outer surface 16q does not necessarily have to be tapered. With this configuration, problems that may arise due to changes in the external dimensions of the battery can be avoided.

[0033] The length L1 of the folding section 16t is adjusted to a range that is, for example, greater than or equal to the thickness T3 of the body section 14 and less than or equal to the straight section 162 (see Figure 5) described later. By ensuring an appropriate length for the folding section 16t, the effects of this disclosure can be more fully realized. In some cases, the length L1 may be less than the thickness T3 of the body section 14.

[0034] The shape of the battery casing 10 is not particularly limited. The battery casing 10 may have, for example, a cylindrical, rectangular, or elliptical shape, and is typically cylindrical.

[0035] Figure 3 is a process diagram showing the manufacturing method of the battery can 10. In step S1, a plate-shaped base material 22 is subjected to deep drawing. The plate-shaped base material 22 is a plated steel sheet and has been pre-processed to a predetermined size considering the final shape of the battery can 10. In the deep drawing process, the plate-shaped base material 22 is set in a mold and a punch is pressed against the plate-shaped base material 22 to plastically deform it into a cylindrical shape. If necessary, the molded body obtained by deep drawing may be subjected to ironing.

[0036] Next, in step S2, the opening of the molded body is trimmed. After the drawing process in step S1, a flange-like portion is formed in the opening of the molded body. The flange-like portion is the part that was gripped by the die during the drawing process. Trimming is a process to cut and remove this flange-like portion. The cut surface formed by trimming is the surface of the base material 22 that does not have a plating layer.

[0037] Next, in step S3, a thin-walled region R1 is formed in the opening. For example, a tapered surface 16u is formed by grinding and / or polishing. When the tapered surface 16u is formed by grinding and / or polishing, the plating layer 20 is removed, and the tapered surface 16u becomes the surface of the base material 22 where the plating layer 20 is not provided. Here, the step of trimming the opening of the molded body and the step of forming the thin-walled region R1 may be performed simultaneously. For example, the tapered surface 16u may be formed simultaneously by trimming the opening of the molded body. This reduces the number of steps and makes it easier to manufacture the battery can 10 of Embodiment 1.

[0038] Next, in step S4, the opening is folded inward to form the folded portion 16t.

[0039] (Embodiment 2) Figure 4 is a cross-sectional view of a battery according to Embodiment 2. The battery 100 comprises a battery case 10 and an electrode group 4. The battery case 10 is the same as that described in Embodiment 1. A sealing body 24 is attached to the opening 16 so that the inside of the battery 100 is sealed. The opening 16 is bent to fix the sealing body 24 to the battery case 10. The sealing body 24 includes a lid 2 and a gasket 3. The gasket 3 is positioned between the lid 2 and the opening 16 of the battery case 10.

[0040] The battery can 10 houses an electrode group 4. The electrode group 4 has a wound structure. The electrode group 4 has a positive electrode 5, a negative electrode 6, and a pair of separators 7. The electrode group 4 is impregnated with electrolyte. The positive electrode 5 has a positive electrode current collector 5a and a positive electrode active material layer 5b. One end of the positive electrode lead 5c is connected to the positive electrode 5. The other end of the positive electrode lead 5c is connected to the back surface of the lid 2. The negative electrode 6 has a negative electrode current collector 6a and a negative electrode active material layer 6b. One end of the negative electrode lead 6c is connected to the negative electrode 6. The other end of the negative electrode lead 6c is connected to the bottom surface of the battery can 10. Insulating rings 8 are arranged on the top and bottom surfaces of the electrode group 4, respectively.

[0041] The lid 2 seals the battery can 10 via the gasket 3. The lid 2 serves as both a terminal and a safety valve. The structure of the lid 2 is not particularly limited as long as it can seal the inside of the battery 100 via the gasket 3; for example, it may be a structure in which multiple components, such as a component that acts as a terminal and a component that acts as a safety valve, are stacked. The gasket 3 is an annular component made of an insulating material such as resin.

[0042] Figure 5 is a partially enlarged view of Figure 4. The opening 16 of the battery can 10 is bent and pressed against the gasket 3. The outer peripheral surface 16q of the folded portion 16t of the opening 16 and the inner peripheral surface 16r of the folded portion and the inner peripheral surface 16r excluding the portion in contact therewith are in close contact with the gasket 3. Thereby, the inside of the battery 100 is sealed. In the example shown in Figure 5, a part of the opening 16 bites into the gasket 3, so that the entire folded portion 16t to the opening edge 16s is in close contact with the gasket 3. That is, a part of the outer peripheral surface 16q in the opening 16 is in contact with and covered by the gasket 3.

[0043] As shown in Figure 5, in the present embodiment, the opening 16 of the battery can 10 includes a rounded portion 161 curved toward the central axis O of the battery can 10 and a straight portion 162 extending from the rounded portion 161 and contacting the upper surface of the sealing body 24. The entire peripheral wall portion 16w and the folded portion 16t of the opening 16 are formed only on the straight portion 162. By restricting the formation range of the folded portion 16t to the straight portion 162, the airtightness inside the battery 100 is surely ensured. It is desirable that the thin-walled region R1 of the opening 16 exists only on the straight portion 162. The rounded portion 161 is a portion where stress concentrates in the battery can 10. When the thin-walled region R1 does not exist in the rounded portion 161 and the folded portion 16t is not provided, the wall thickness of the rounded portion 161 can be sufficiently ensured. Therefore, the possibility that the plating layer 20 causes stress corrosion cracking in the rounded portion 161 can be reduced.

[0044] In the projection image obtained by orthographically projecting the battery 100 onto a plane perpendicular to the central axis O of the battery can 10, it is desirable that the entire folded portion 16t overlaps the lid body 2. According to such a configuration, the possibility that the plating layer causes stress corrosion cracking in the rounded portion 161 can be reduced. Also, the inside of the battery 100 can be properly sealed. The central axis O of the battery can 10 typically coincides with the winding axis direction of the electrode group 4.

[0045] The length of the straight section 162 is, for example, 0.5 mm to 1.5 mm. It is also desirable that the length L1 of the folding section 16t (Figure 2) be between 0.3 mm and 1.0 mm. For example, the length L1 from the opening edge 16s to the end face 16p is between 1 / 3 and 1 / 2 of the length from the opening edge 16s to the boundary between the rounded section 161 and the straight section 162 (the length of the straight section 162 in Figure 5). With such a configuration, the possibility of stress corrosion cracking of the plating layer in the rounded section 161 can be reduced. It is also desirable that the length of the thin-walled region R1 of the opening 16, i.e., the length of the tapered surface 16u (Figure 2), be between 0.3 mm and 1.0 mm.

[0046] Figure 6A is a diagram illustrating the operation of the battery 100 of this embodiment. As shown in Figure 6A, the battery 100 of this embodiment uses the battery can 10 of Embodiment 1. The opening 16 of the battery can 10 includes a folding portion 16t. According to the battery 100 of this embodiment, even if a liquid W such as water or electrolyte remains on the upper surface of the sealing body 24, the folding portion 16t prevents the liquid W from coming into contact with the end face 16p. Therefore, even if the end face 16p is formed by the surface of the base material 22 which does not have a plating layer, the occurrence of rust can be minimized. Even if rust does occur, it is unlikely to be a problem because the end face 16p is not exposed on the surface of the battery 100. Furthermore, even though the opening 16t of the battery can 10 of this embodiment has a folding portion 16t, the sum of the thickness T1 and the thickness T2 is less than twice the thickness T3, and does not become excessively large. As a result, the opening 16 does not bite into the gasket 3 too much, and a sufficient thickness of the gasket 3 can be maintained. If the thickness of the part of the battery can 10 that presses against the gasket 3 is large, the thickness of the pressed gasket 3 will decrease. Since the gasket 3 also acts as an insulator, if the thickness of the gasket 3 becomes too small, there is a possibility that the lid 2 of the sealing body 24 and the battery can 10 will become electrically connected, causing a short circuit.

[0047] Even if the plating layer 20 does not exist at the position corresponding to the tapered surface 16u on the inner peripheral surface 16r, the tapered surface 16u is in close contact with the gasket 3, or the tapered surface 16u is not exposed due to the folded portion 16t, so the possibility of the tapered surface 16u rusting is low.

[0048] FIG. 6B is a diagram for explaining the operation of a conventional battery. When the opening 116 of the battery can does not include a folded portion, the end face 116p, which is the open end edge of the battery can, comes into contact with the liquid W. Therefore, rust may occur.

[0049] FIG. 7 is a process diagram showing an example of a method for manufacturing the battery 100. In step S11, a plate-shaped base material 22 is drawn. Step S11 is the same as step S1 in Embodiment 1.

[0050] Next, in step S12, the opening of the formed body obtained by the drawing process is trimmed. Step S12 is the same as step S2 in Embodiment 1.

[0051] Next, in step S13, a thin region R1 is formed. For example, the tapered surface 16u is formed by grinding and / or polishing. Step S13 is the same as step S3 in Embodiment 1. The process of trimming the opening of the formed body and the process of forming the thin region R1 may be carried out simultaneously.

[0052] Next, in step S14, the electrode group 4 is housed in the formed body. When housing the electrode group 4, the negative electrode lead 6c connected to the electrode group 4 may be connected to the formed body. After the electrode group 4 is housed in the formed body, the insulating ring 8 may be inserted into the formed body and disposed above the electrode group 4. Then, the electrolytic solution may be injected into the formed body.

[0053] Next, in step S15, the opening of the formed body is folded inward of the formed body to form the folded portion 16t. Thus, the battery can 10 housing the electrode group 4 is obtained.

[0054] Finally, in step S16, the battery can 10 is sealed with the sealing body 24. The sealing is done, for example, by crimping and fixing the sealing body 24 to the opening 16. In this way, the battery 100 is obtained.

[0055] According to the above manufacturing method, since the opening is folded inward after the electrode group 4 is housed in the can, the shape of the battery can 10, such as the thickness of the folded portion 16t, is not affected by the size of the electrode group 4. When housing the electrode group 4 in the battery can 10 after manufacturing the battery can 10 according to Embodiment 1, it is necessary to design the shape and thickness of the folded portion 16t so that the electrode group 4 can be housed.

[0056] The manufacturing method of the battery 100 is not limited to the above. For example, after forming the folding portion 16t, that is, after manufacturing the battery can 10 according to Embodiment 1, the electrolyte may be injected into the molded body (battery can 10). Alternatively, for example, after manufacturing the battery can 10 according to Embodiment 1, the electrode group 4, insulating ring 8, electrolyte, etc., may be housed inside the battery can 10.

[0057] (Modified Version) Figure 8 is a partially enlarged cross-sectional view of a modified battery can 11. In the battery can 11, the tapered surface 16u, which is part of the inner circumferential surface 16r, is also a plated surface formed by the plating layer 20. With this configuration, the occurrence of rust on the tapered surface 16u can be further suppressed. The entire surface of the battery can 10, excluding the end face 16p, may be a plated surface formed by the plating layer 20.

[0058] In this modified example, the tapered surface 16u can be formed by press-forming the opening of the molded body in step S3 shown in Figure 3. Press-forming leaves the plating layer 20 on the inner circumferential surface 16r (tapered surface 16u) of the thin-walled region.

[0059] Figure 9 is a partially enlarged cross-sectional view of a battery can 12 according to another modified example. In the battery can 12, the end face 16p is formed by a tapered surface 16u. The tapered surface 16u (end face 16p) is formed by the surface of the base material 22 which does not have a plating layer. With this configuration, it is easier to make the thickness of the folding portion 16t smaller. Therefore, it is easier to make the overall thickness near the opening edge 16s of the battery can 12 smaller, so that a sufficient gasket thickness can be ensured even when the opening 16 is pressed against the sealing body when sealing the battery can 12.

[0060] In this modified example, the end face 16p can be formed by step S2 shown in Figure 3. Therefore, step S2 and step S3, which forms the thin-walled region, can be performed simultaneously. The battery can 12 of this modified example may be easier to manufacture than the battery can 10 and / or the battery can 11. Alternatively, after step S2, the end face 16p can be formed in step S3 by grinding and / or polishing.

[0061] (Other Embodiments) (Note) The above description of embodiments discloses the following technologies.

[0062] (Technical 1) A battery can comprising: a bottom portion; a cylindrical body portion extending from the bottom portion; and an opening continuing from the body portion, wherein the opening includes an end face formed by the surface of a base material without a plating layer, a peripheral wall portion continuing from the body portion, and a folded portion including the end face that is folded inward into the battery can so as to overlap the peripheral wall portion, and when the thickness of the folded portion at the position of the end face is defined as T1, the thickness of the peripheral wall portion at the position closest to the end face is defined as T2, and the thickness of the body portion is defined as T3, the sum of the thickness T1 and the thickness T2 is less than twice the thickness T3.

[0063] The technology disclosed herein provides a battery case that can suppress rust formation and ensure battery reliability with a simple configuration.

[0064] (Technology 2) The battery can according to Technology 1, wherein the maximum thickness of the folding portion is smaller than the thickness T3. With this configuration, the opening is easily folded, so that the inner surface of the folding portion comes into contact with the inner surface of the peripheral wall. Therefore, the overall thickness near the opening edge of the battery can can be reduced.

[0065] (Technology 3) A battery can according to Technology 1 or 2, wherein the thickness T2 is smaller than the thickness T3. Such a battery can reduce the overall thickness near the opening edge. Therefore, the occurrence of rust can be suppressed while more reliably maintaining the reliability of the battery.

[0066] (Technology 4) A battery can according to any one of Technology 1 to 3, wherein the thickness T1 is smaller than the thickness T2. According to Technology 4, a battery can is provided that can suppress rust formation and ensure battery reliability with a simple configuration.

[0067] (Technical 5) The battery can according to any one of Technical 1 to 4, wherein the opening has a thin-walled region having a thickness less than the thickness T3 and a thick-walled region having a thickness greater than the thickness of the thin-walled region, and in the direction in which the body and the opening extend from the bottom toward the end face, the thin-walled region is located closer to the end face than the thick-walled region, and in the thin-walled region, the thickness of the opening decreases toward the end face. Such a battery can reduce the overall thickness near the edge of the opening. Therefore, the occurrence of rust can be suppressed while more reliably maintaining the reliability of the battery.

[0068] (Technical 6) The battery can according to Technical 5, wherein the entire folding portion and the portion of the peripheral wall that overlaps with the folding portion are located within the thin-walled region. Such a battery can reduce the overall thickness near the opening edge. Therefore, the occurrence of rust can be suppressed while more reliably maintaining the reliability of the battery.

[0069] (Technical 7) The battery can according to Technical 5 or 6, wherein in the thin-walled region, the inner circumferential surface of the opening includes a tapered surface that slopes toward the end face such that the thickness of the opening decreases toward the end face, and the tapered surface is formed by the surface of a base material that does not have a plating layer. Such a battery can have a smaller overall thickness near the opening edge. Therefore, rust can be suppressed while more reliably maintaining the reliability of the battery. Furthermore, such a battery can may be easily manufactured.

[0070] (Technical 8) A battery can according to any one of Technical 1 to 7, wherein the sum of the thickness T1 and the thickness T2 is 1.0 times or less the thickness T3. Such a battery can suppress the occurrence of rust with a simple structure without significantly changing the thickness. Therefore, the occurrence of rust can be suppressed while more reliably maintaining the reliability of the battery.

[0071] (Technical 9) A battery comprising: a battery can; an electrode group housed in the battery can; and a sealing body attached to the battery can, wherein the battery can is a battery can described in any one of Technical 1 to 8.

[0072] The technology disclosed herein provides a battery that can achieve both rust suppression and reliability with a simple configuration.

[0073] (Technical 10) The battery according to Technical 9, wherein the sealing body includes a lid and a gasket disposed between the peripheral edge of the lid and the opening, and in the projected image obtained by orthogonally projecting the battery onto a plane perpendicular to the central axis of the battery can, the entire folding portion overlaps the lid. With such a configuration, for example, the possibility of stress corrosion cracking of the plating layer in the curved portion where the opening curves toward the center of the battery can can be reduced. In addition, the inside of the battery can be properly sealed.

[0074] (Technical 11) The battery according to Technical 9 or 10, wherein the opening of the battery can includes a curved portion that is curved toward the center of the battery can and a straight portion that extends from the curved portion and is in contact with the upper surface of the sealing body, and the entire peripheral wall portion and the folding portion are included in the straight portion. With such a configuration, the possibility of stress corrosion cracking of the plating layer in the curved portion can be reduced.

[0075] (Technical 12) The battery according to Technical 11, wherein the length from the opening edge of the battery can to the end face is 1 / 3 or more and 1 / 2 or less of the length from the opening edge to the boundary between the curved portion and the straight portion. With such a configuration, the possibility of stress corrosion cracking of the plating layer in the curved portion can be reduced.

[0076] The technology disclosed herein is useful for batteries using metal containers.

Claims

1. A battery can comprising: a bottom; a cylindrical body extending from the bottom; and an opening continuing from the body, wherein the opening includes an end face formed by the surface of a base material without a plating layer; a peripheral wall continuing from the body; and a folded portion including the end face that is folded inward into the battery can so as to overlap the peripheral wall, and the thickness of the folded portion at the position of the end face is defined as T1, the thickness of the peripheral wall at the position closest to the end face is defined as T2, and the thickness of the body is defined as T3, the sum of the thickness T1 and the thickness T2 is less than twice the thickness T3.

2. The battery can according to claim 1, wherein the maximum thickness of the folding portion is less than the thickness T3.

3. The battery can according to claim 1, wherein the thickness T2 is smaller than the thickness T3.

4. The battery can according to claim 1, wherein the thickness T1 is smaller than the thickness T2.

5. The battery can according to claim 1, wherein the opening has a thin-walled region having a thickness less than the thickness T3 and a thick-walled region having a thickness greater than the thickness of the thin-walled region, and in the direction in which the body and the opening extend from the bottom toward the end face, the thin-walled region is located closer to the end face than the thick-walled region, and in the thin-walled region, the thickness of the opening decreases toward the end face.

6. The battery can according to claim 5, wherein the entire folding portion and the portion of the peripheral wall that overlaps with the folding portion are located within the thin-walled region.

7. The battery can according to claim 5, wherein in the thin-walled region, the inner circumferential surface of the opening includes a tapered surface that is inclined such that the thickness of the opening decreases toward the end face, and the tapered surface is formed by the surface of a base material that does not have a plating layer.

8. The battery can according to claim 1, wherein the sum of the thickness T1 and the thickness T2 is 1.0 times or less the thickness T3.

9. A battery comprising: a battery can; an electrode group housed in the battery can; and a sealing body attached to the battery can, wherein the battery can is the battery can described in claim 1.

10. The battery according to claim 9, wherein the sealing body includes a lid and a gasket disposed between the peripheral edge of the lid and the opening, and in a projection image obtained by orthogonally projecting the battery onto a plane perpendicular to the central axis of the battery can, the entire folding portion overlaps the lid.

11. The battery according to claim 9, wherein the opening of the battery can includes a curved portion that is curved toward the center of the battery can and a straight portion that extends from the curved portion and is in contact with the upper surface of the sealing body, and the entire peripheral wall portion and the folding portion are included in the straight portion.

12. The battery according to claim 11, wherein the length from the opening edge of the battery can to the end face is 1 / 3 or more and 1 / 2 or less of the length from the opening edge to the boundary between the curved portion and the straight portion.

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