JP7848003B2 - battery - Google Patents

Description

This invention relates to a battery.

Batteries in which the power generation element is housed in a metal can have been known for some time.

Japanese Patent Publication No. 2019-192403

In such batteries, it is necessary for the metal casing to absorb shock and reduce malfunctions when subjected to impact. However, conventional batteries have not had sufficient shock absorption capabilities in their metal casings.

This invention was made in view of the above-mentioned problems, and aims to provide a battery with excellent shock absorption properties for the metal can.

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

The wall thickness in the grooved portion of the metal can may be 30-80% of the wall thickness of the thinnest portion of the metal can other than the grooved portion.

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 and second metal members.

The first metal member may be cylindrical.

According to the present invention, a battery with excellent shock absorption properties for the metal can is provided.

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

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

Figure 1 is a cross-sectional view along the axis of a spiral-type battery 100 according to one embodiment. This embodiment of the battery 100 includes a power generation element 10 and a metal casing 50.

The power generation element 10 has a positive electrode 3, a negative electrode 4, and a separator 5 separating the positive electrode 3 and the negative electrode 4. These are impregnated with an electrolyte (not shown).

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 include a positive electrode active material, a conductive additive, and a binder. An example of the positive electrode active material is a lithium-containing composite oxide.

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 may contain a negative electrode active material, a conductive additive, and a binder. Examples of negative electrode active materials include carbon materials and Si. If the negative electrode active material is a metal such as lithium, the negative electrode may be a metal foil.

The separator 5 can be an electrically insulating microporous film or nonwoven fabric, and may have a laminated structure.

The positive electrode 3 and negative electrode 4 are stacked in multiple layers so that the positive electrode 3 and the negative electrode 4 are positioned opposite each other via a separator 5, and are further wound in a spiral shape.

Examples of electrolytes include aqueous and non-aqueous electrolytes, and the electrolyte can be appropriately selected according to the battery. In the case of lithium batteries, a non-aqueous electrolyte containing lithium salts may be used.

Metal can structure: The metal can 50 has a first lid 42, a cylindrical body 44, and a second lid 46.

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

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.

With the small-diameter portion 42B of the first lid 42 inserted into the interior of the cylindrical body 44, 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 are welded together via a weld joint 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 surface 42AS of the large-diameter portion 42A of the first lid 42 are joined via the weld joint 43.

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.

Since this 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.

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.

In this specification, a bent portion refers to a portion where, in a cross-section perpendicular to the direction of extension of the groove G, the axis of the groove G bends at an angle of 80° or more. In this embodiment, the angle is approximately 90°.

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.

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.

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

Specifically, the wall thickness THG of the metal can 50 in the groove G (wall thickness of the welded portion 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.

Such a groove 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. Specifically, by adjusting the output energy when irradiating with a laser from the radially outer portion, the laser scanning speed, etc., only the radially outer portion can be selectively welded to form the welded portion 43 and the groove G.

As shown in Figure 1, the second lid 46, like the first lid 42, has a stepped outer surface. 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 G with a similar bent portion is formed between the second lid 46 and the cylindrical body 44. The shape of the groove G is the same as that provided between the first lid 42 and the cylindrical body 44.

Furthermore, 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.

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.

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).

According to this embodiment of the battery, the metal can 50 has at least one groove G formed along its inner surface, 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 impact, such as when it is dropped, the impact is suitably absorbed, thereby suppressing leakage due to damage to the metal can 50.

This invention can take on various modified forms.

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.

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, 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.

Figure 3(b) differs from the embodiments in 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 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.

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. 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.

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.

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 with two bent portions G1 is formed between the first lid 42 and the cylindrical body 44.

(Other variations)
The groove G is not particularly limited in shape or position as long as it has at least one bent portion. 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.

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. Furthermore, it is also possible for portions with grooves and portions without grooves to be arranged alternately in a dotted line pattern.

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. However, it is not limited to this, and may also be the thickness of the first lid or the second lid.

In the above embodiment, the structure includes a first lid 42 and a second lid 46, with grooves G between the first lid 42 and the cylindrical body 44, and between the second lid 46 and the cylindrical body 44. However, grooves G may be present in only one of these locations.

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

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.

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.

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

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

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.

An impact test was conducted by dropping 100 manufactured batteries onto a stainless steel plate from a height of 1 meter. The number of batteries showing leakage after the test was then counted.

(Examples 2-7)
The procedure was carried out in the same manner as in Example 1, except that the wall thickness of the grooves G (welded portions 43 and 45) was changed to match those shown in Table 1 by varying the welding conditions.

(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, otherwise the procedure is the same as in Example 1.

(Comparative Example 2)
As shown in Figure 6(b), the first lid 42 without a step is used, and the welded portion 43 is 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 is provided, otherwise the configuration is the same as in Embodiment 1.

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

10...power generation element, 50...metal can, 100...battery, G...groove, G...groove, G1, G2...bent section.

Claims (2)

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