Battery

Abstract

To provide a metal can battery with excellent shock absorption properties.SOLUTION: A battery 100 includes a power generation element 10 and a metal can 50 that houses the power generation element 10. The metal can 50 has at least one groove G formed along the inner surface of the metal can 50, and in a cross section perpendicular to the direction along the inner surface of the groove G, the groove G has at least one bent portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] Conventionally, a battery in which a power generation element is housed in a metal can is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a battery, when the metal can is subjected to an impact, it is required to absorb the impact and reduce defects. However, in conventional batteries, the impact absorption performance of the metal can is not sufficient.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a battery having excellent impact absorption properties of a metal can.

Means for Solving the Problems

[0006] A battery according to an embodiment includes a power generation element and a metal can that houses the power generation element. The metal can has at least one groove portion formed along the inner surface of the metal can, and the groove portion has at least one bent portion in a cross section perpendicular to the direction along the inner surface of the groove portion.

[0007] The wall thickness of the groove portion of the metal can can be 30 to 80% of the wall thickness of the thinnest portion other than the groove portion of the metal can.

[0008] The metal can comprises a first metal member and a second metal member welded to the first metal member, and the groove may be provided between the first metal member and the second metal member.

[0009] The first metal member can be cylindrical. [Effects of the Invention]

[0010] According to the present invention, a battery with excellent shock absorption properties for a metal can is provided. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view of a battery according to one embodiment. [Figure 2] Figure 2 is a perspective cross-sectional view of the top of the metal can 50 shown in Figure 1. [Figure 3] Figures 3(a) and 3(b) show partial cross-sectional views of the metal casing of a battery according to another embodiment. [Figure 4] Figures 4(a) and 4(b) show partial cross-sectional views of the metal casing of a battery according to another embodiment. [Figure 5] Figure 5 is a partial cross-sectional view of the metal can of a battery according to another embodiment. [Figure 6] Figures 6(a) and 6(b) show partial cross-sectional views of the metal casing of a battery in a comparative configuration. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the invention will be described below with reference to the drawings. In the following description, the same or similar parts may be denoted by the same reference numerals, and redundant explanations may be omitted.

[0013] Figure 1 is a cross-sectional view along the axis of a spiral-type battery 100 according to one embodiment. The battery 100 in this embodiment comprises a power generation element 10 and a metal can 50.

[0014] The power generation element 10 has a positive electrode 3, a negative electrode 4, and a separator 5 that separates the positive electrode 3 and the negative electrode 4, and these are impregnated with an electrolyte solution not shown in the figure.

[0015] The positive electrode 3 can be a laminate of a positive electrode current collector and a positive electrode mixture layer. An example of the positive electrode current collector is aluminum foil. The positive electrode mixture layer can contain a positive electrode active material, a conductive assistant, and a binder. An example of the positive electrode active material is a lithium-containing composite oxide.

[0016] The negative electrode 4 can be a laminate of a negative electrode current collector and a negative electrode mixture layer. The negative electrode mixture layer can contain a negative electrode active material, a conductive assistant, and a binder. Examples of the negative electrode active material are a carbon material, Si, etc. When the negative electrode active material is a metal such as lithium, the negative electrode may be a metal foil.

[0017] The separator 5 can be an electrically insulating microporous film or non-woven fabric, etc., and may have a laminated structure.

[0018] The positive electrode 3 and the negative electrode 4 are stacked in multiple layers in a layered manner such that the positive electrode 3 and the negative electrode 4 are arranged to face each other through the separator 5, and are further wound in a spiral shape.

[0019] Examples of the electrolyte solution are an aqueous electrolyte solution and a non-aqueous electrolyte solution, and the electrolyte can be appropriately selected according to the battery. In the case of a lithium battery, it can be a non-aqueous electrolyte solution containing a lithium salt.

[0020] Structure of the metal can The metal can 50 has a first lid 42, a cylindrical body 44, and a second lid 46.

[0021] As shown in Figure 2, the first lid 42 has a stepped disc shape, and the outer diameter DB of the small diameter portion 42B (lower side) is smaller than the outer diameter DA of the large diameter portion (upper side) 42A. The difference between the outer diameter DA of the large diameter portion 42A and the outer diameter DB of the small diameter portion 42B can be 140 to 1400 μm. The axial length (thickness) LA of the large diameter portion 42A can be 200 to 800 μm, and the axial thickness LB of the small diameter portion 42B can be 200 to 600 μm.

[0022] The cylindrical body 44 is cylindrical, and its outer diameter DD is equivalent to the outer diameter DA of the large-diameter portion 42A of the first lid 42. The inner diameter DC of the cylindrical body 44 is larger than the outer diameter DB of the small-diameter portion 42B of the first lid 42. The difference between DB and DC can be 40 to 400 μm.

[0023] With the small-diameter portion 42B of the first lid 42 inserted into the interior of the cylindrical body 44, the stepped-side surface 42AS of the large-diameter portion 42A of the first lid 42 and the upper end surface 44E of the cylindrical body 44 are welded together via a weld 43. Here, only the radially outer portion of the upper end surface 44E of the cylindrical body 44 and only the radially outer portion of the stepped-side surface 42AS of the large-diameter portion 42A of the first lid 42 are joined together via the weld 43.

[0024] As a result, a groove G is formed between the upper end surface 44E and the inner circumferential surface 44R of the cylindrical body 44, and the stepped side surface 42AS of the large diameter portion 42A and the outer circumferential surface 42BS of the small diameter portion 42B of the first lid 42.

[0025] Since the groove G is formed between the corner formed by the upper end surface 44E and the inner circumferential surface 44R of the cylindrical body 44 and the corner formed by the stepped side surface 42AS of the large diameter portion 42A and the outer circumferential surface 42BS of the small diameter portion 42B of the first lid 42, the groove G has one bent portion G1.

[0026] This groove G communicates with the internal space V of the metal can 50, extends from the internal space V toward the outside of the metal can 50, and does not communicate with the outside of the metal can 50.

[0027] In this specification, a bent portion refers to a portion of a groove G that bends at an angle of 80° or more in a cross-section perpendicular to the direction in which the groove G extends. In this embodiment, the angle is approximately 90°.

[0028] The width W of the groove G in the cross-section can be 20 to 200 μm. The total length of the axis of the groove G can be 0.2 to 0.9 mm.

[0029] As shown in Figure 2, the groove G is formed in an annular shape along the inner circumferential surface 44R of the cylindrical body 44. Figures 1 and 2 show a cross-section of the groove G perpendicular to the direction along the inner surface of the metal can 50.

[0030] The wall thickness THG in the groove G of the metal can 50 (in this embodiment, the wall thickness of the welded portion 43) is preferably 30-80% of the wall thickness of the thinnest part of the metal can 50 other than the groove G.

[0031] Specifically, the wall thickness THG of the metal can 50 in the groove G (wall thickness of the welded part 43) can be 50 to 400 μm, and the wall thickness of the thinnest part of the metal can 50 other than the groove G (for example, the wall thickness TH of the cylindrical body 44) can be 50 to 500 μm.

[0032] Such grooves G can be obtained by selectively welding only the radially outer portion when butting the stepped surface 42AS of the large-diameter portion 42A of the first lid 42 and the upper end surface 44E of the cylindrical body 44 together. Specifically, by adjusting the output energy when irradiating with a laser from the radially outer portion, the scanning speed of the laser, etc., the welded portion 43 and grooves G can be formed by selectively welding only the radially outer portion.

[0033] As shown in Figure 1, the second lid 46, like the first lid 42, has a stepped outer surface, and the radially outer portion of the stepped surface 46AS of the large diameter portion 46A and the radially outer portion of the lower end surface 44F of the cylindrical body 44 are joined via a welded portion 45. Therefore, a groove portion G with a similar bent portion is formed between the second lid 46 and the cylindrical body 44. The shape of the groove portion G is the same as that provided between the first lid 42 and the cylindrical body 44.

[0034] The second cover 46 has a through hole 46h in its center, through which the electrode member 47 and the crimped electrode member 48 are inserted via an electrical insulating gasket 49.

[0035] The materials of the first lid 42, the cylindrical body 44, and the second lid 46 can be any metal material, such as aluminum, stainless steel, or iron.

[0036] The negative electrode 4 of the power generation element 10 is electrically connected to the cylindrical body 44 or the first cover 42, and the positive electrode 3 of the power generation element 10 is connected to the electrode member 47 by lead wires (not shown).

[0037] According to the battery of this embodiment, the metal can 50 has at least one groove G formed along the inner surface of the metal can 50, and in a cross section perpendicular to the direction along the inner surface of the groove G, the groove G has at least one bent portion G1. Therefore, when the battery 100 is subjected to an impact, such as when the battery 100 is dropped, the impact is suitably absorbed, and leakage due to damage to the metal can 50 can be suppressed.

[0038] This invention can take on various modified forms.

[0039] Figures 3(a) and 3(b), 4(a) and 4(b), and 5 show examples of modified configurations of the groove G of the present invention. Only the differences from the embodiments in Figures 1 and 2 will be explained.

[0040] Figure 3(a) differs from Figures 1 and 2 in that the upper end of the cylindrical body 44 has a stepped shape and has a protruding portion 44A and a non-protruding portion 44B. The outer diameter DA of the large-diameter portion 42A of the first lid 42 is smaller than the inner diameter DE of the protruding portion 44A of the cylindrical body 44, and the height AH of the protruding portion 44A is larger than the thickness (axial length) LA of the large-diameter portion 42A of the first lid 42. The axially outer portion of the inner circumferential surface of the protruding portion 44A and the axially outer portion of the outer circumferential surface of the large-diameter portion 42A of the first lid 42 are joined via a welded portion 43. Therefore, in this embodiment, compared to the embodiments of Figures 1 and 2 described above, a bent portion G2 is further added, formed by the corner formed between the protruding portion 44A and the non-protruding portion 44B of the cylindrical body 44 and the corner of the large-diameter portion 42A of the first lid 42, forming a groove portion G with two bent portions.

[0041] The difference between Figure 3(b) and the embodiments in Figures 1 and 2 is that the upper end of the cylindrical body 44 has a stepped shape and has a protruding portion 44A and a non-protruding portion 44B. The outer diameter DB of the small-diameter portion 42B of the first lid 42 is smaller than the inner diameter DE of the protruding portion 44A of the cylindrical body 44, and larger than the inner diameter DC of the non-protruding portion 44B of the cylindrical body 44. Therefore, in this embodiment, the groove portion G has a bent portion G1 formed by the corner between the protruding portion 44A and the non-protruding portion 44B of the cylindrical body 44 and the corner of the small-diameter portion 42B, and a bent portion G2 formed by the corner of the protruding portion 44A of the cylindrical body 44 and the corner between the large-diameter portion 42A and the small-diameter portion 42B of the first lid 42.

[0042] Figure 4(a) differs from the embodiments in Figures 1 and 2 in that the first lid 42 has a cylindrical portion 42C that is provided along the outer peripheral edge of its inner surface and protrudes downward, and the cylindrical body 44 has a cylindrical portion 44C that protrudes upward toward the inner peripheral surface of its upper end surface. The inner diameter DF of the cylindrical portion 42C of the first lid 42 is larger than the outer diameter DG of the cylindrical portion 44C of the cylindrical body 44. The lower end of the cylindrical portion 42C of the first lid 42 and the axially outer portion of the upper end surface 44E of the non-cylindrical portion of the cylindrical body 44 are joined via a welded portion 43. The tip of the cylindrical portion 44C of the cylindrical body 44 is separated from the first lid 42. Therefore, in this embodiment, a groove G having a bent portion G1 is formed between the first lid 42 and the cylindrical body 44. Note that in the cases of Figure 4(a) and Figure 4(b) below, the wall thickness of the cylindrical portion 42C and the wall thickness of the welded portion 43 are the same.

[0043] The difference between the configuration in Figure 4(b) and Figure 4(a) is that the lower surface of the first lid 42 has a recess 42V. The cylindrical portion 42C of the first lid 42 forms the outer edge of the recess 42V, and the inner diameter DF of the cylindrical portion 42C of the first lid 42 is larger than the outer diameter DG of the cylindrical portion 44C of the cylindrical body 44. The outer diameter DH of the inner circumferential surface of the recess 42V is smaller than the inner diameter DC of the cylindrical body 44. The cylindrical portion 44C of the cylindrical body 44 is recessed into the recess 42V, and the upper end of the cylindrical portion 44C is spaced apart from the first lid 42. Therefore, in this configuration, a groove G having bent portions G1 and G2 is formed between the first lid 42 and the cylindrical body 44.

[0044] The difference between the configuration in Figure 5 and Figure 4(a) is that the position of the groove G has shifted towards the axial center of the metal can 50. That is, the first lid 42 also has a cylindrical body 42Z with the same thickness as the cylindrical body 44, and a cylindrical portion 42C is formed at the end of the cylindrical body 42Z. In this configuration as well, a groove G having two bent portions G1 is formed between the first lid 42 and the cylindrical body 44.

[0045] (Other variations) The groove G is not particularly limited in shape or position as long as it has at least one bend. When the metal can 50 has a first metal member such as a first lid 42 and a second metal member such as a cylindrical body 44 welded to the first metal member, it is preferable that the groove G be provided between the first metal member and the second metal member.

[0046] In the above embodiment, the groove G is formed in an annular shape along the entire circumference of the inner surface of the cylindrical body 44, but it does not have to be around the entire circumference. For example, it may be formed over half the circumference or over a quarter of the circumference. It is also possible for the parts with grooves and parts without grooves to be arranged alternately in a dotted line pattern.

[0047] In the above embodiment, the thinnest part of the metal can 50, other than the groove G, is the thickness of the cylindrical body 44, but it is not limited to this, and may be the thickness of the first lid or the second lid.

[0048] In the above embodiment, the first lid 42 and the second lid 46 are provided, and there are grooves G between the first lid 42 and the cylindrical body 44, and between the second lid 46 and the cylindrical body 44, but the grooves G may be provided in only one of them.

[0049] Furthermore, the first lid 42 and the cylindrical body 44 may be integrally formed by drawing or the like. In that case, a groove G can be provided between the second lid and the cylindrical body 44.

[0050] The shape of the cross-section perpendicular to the axis of the cylindrical body 44 is not limited to a circle; it may also be a square or other shape.

[0051] Examples of batteries include lithium primary batteries, which use lithium metal or lithium alloy as the negative electrode active material and manganese dioxide or copper oxide as the positive electrode active material, and lithium secondary batteries, which use lithium metal or lithium alloy as the negative electrode active material and lithium-cobalt composite oxide (LiCoO2) as the positive electrode active material.

[0052] The configuration of the power generation elements is not particularly limited, and it does not have to be spiral-shaped.

[0053] Example 1 A battery was constructed as shown in Figures 1 and 2. The specific dimensions were DA=26mm, DB=25.2mm, DC=25.36mm, DD=26mm, LA=500μm, LB=450mm, groove width W=80μm, groove thickness (i.e., weld thickness) THG=80μm. The thickness TH of the cylindrical body 44, which is the thinnest part other than the groove, was set to 320μm. Since the thickness THG of the groove G (welded parts 43 and 45) is 80μm, the ratio of the groove G thickness to the thinnest part thickness TH was 25%. The total length of the battery was 66mm.

[0054] The metal can was made of aluminum. Lithium iron phosphate was used as the positive electrode active material, a mixture of graphite and silicon oxide was used as the negative electrode active material, and lithium hexafluoride phosphate (LiPF6) was dissolved as the electrolytic salt in a mixed organic solvent of 4-fluoro-1,3-dioxolan-2-one (FEC), ethylene carbonate (EC), and dimethyl carbonate (DMC) as the electrolyte.

[0055] An impact test was conducted by dropping 100 manufactured batteries from a height of 1 meter onto a stainless steel plate. The number of batteries that leaked after the test was then counted.

[0056] (Examples 2-7) The procedure was the same as in Example 1, except that the welding conditions were changed to make the wall thickness of the grooves G (welded sections 43 and 45) as shown in Table 1.

[0057] (Comparative Example 1) As shown in Figure 6(a), the first lid 42 without a step is used, and the entire surface of the butt joint between the first lid 42 and the cylindrical body 44 is welded to form a welded portion 43, so that there is no groove portion G, except that the procedure is the same as in Example 1.

[0058] (Comparative Example 2) As shown in Figure 6(b), the first lid 42 without a step was used, and the welded portion 43 was formed by welding only the radially outer side of the butt joint between the first lid 42 and the cylindrical body 44, and a groove G without a bent portion was provided, except that the configuration was the same as in Example 1.

[0059] In embodiments equipped with a groove G having a bent portion, the impact test fluid leakage rate was reduced compared to the comparative example. In particular, the fluid leakage rate was low when the wall thickness ratio was 30-80%.

[0060] [Table 1] [Explanation of Symbols]

[0061] 10...Power generation element, 50...Metal can, 100...Battery, G...Groove section, G...Groove section, G1, G2...Bent section.

Claims

1. A battery comprising a power generation element and a metal can housing the power generation element, The metal can has at least one groove formed along the inner surface of the metal can, The metal can comprises a first metal member and a second metal member welded to the first metal member, with the groove provided between the first metal member and the second metal member. The first metal member is a cylindrical body, and the second metal member is a lid. In a cross-section perpendicular to the direction along the inner surface of the groove, the groove has two or more bent portions. A battery in which the wall thickness of the groove portion of the metal can is 30 to 80% of the wall thickness of the thinnest part of the metal can other than the groove portion.

2. The battery according to claim 1, wherein the first metal member is a cylinder.

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