Rectangular secondary battery

This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2020/017978, filed on Apr. 27, 2020, which in turn claims the benefit of Japanese Application No. 2019-134855, filed on Jul. 22, 2019, the disclosures of which Applications are incorporated by reference herein.

The present invention relates to a rectangular secondary battery.

With a higher output of an on-vehicle secondary battery, a current flowing through the battery increases. As a result, an increasing amount of heat is generated in the battery, whereby the temperature of the entire battery rises. An excessive rise in the temperature of the entire battery may deteriorate resin parts such as a gasket and/or alter an electrolyte, for example.

Patent Document 1 discloses a sealed battery (e.g., a secondary battery) obtained by fastening a current collecting terminal (i.e., a current collector) to an external terminal by crimping a rivet. The current collecting terminal is connected to each of positive and negative electrodes of an electrode body.

Patent Document

Patent Document 1: Japanese Unexamined Patent Publication No. 2013-105538

In the secondary battery with the structure disclosed in Patent Document 1, the rivet needs to have a thickness reduced to some extent so as to be crimped. The rivet cannot have thus a large cross-sectional area. A large current flowing through the rivet may increase the Joule heat and cause an excessive temperature rise inside the battery.

In a lithium ion battery with a high energy density, a positive electrode current collector is typically made of aluminum or an aluminum alloy, and a negative electrode current collector is typically made of copper or a copper alloy. The rivet connected to each current collector is made of the same material as the current collector. That is, the rivet (e.g., aluminum) used for the positive electrode has a higher electrical resistance than the rivet (e.g., copper) used for the negative electrode. Accordingly, a large current flowing through the rivet for the positive electrode may increase the Joule heat and cause excessive temperature rise inside the battery.

The present invention was made in view of the foregoing. It is a main objective of the present invention to provide a secondary battery causing less Joule heat and less temperature rise inside.

A rectangular secondary battery according to the present invention includes: an electrode body including a positive electrode plate and a negative electrode plate; a rectangular battery case having an opening and housing the electrode body; a sealing plate sealing the opening; a current collector connected to an edge of the positive electrode plate or the negative electrode plate at a longitudinal end of the sealing plate; and an external terminal located outside the sealing plate and connected to the current collector, the current collector having a hole at an end closer to the sealing plate, and the current collector being connected to the external terminal with a connector interposed therebetween which is inserted into the hole.

The present invention provides a secondary battery causing less Joule heat and less temperature rise inside.

FIG. 1 A and FIG. 1 B schematically show a configuration of a rectangular secondary battery according to an embodiment of the present invention. FIG. 1 A is a top view, while FIG. 1 B is a cross-sectional view taken along line Ib-Ib of FIG. 1 A .

FIG. 2 A and FIG. 2 B illustrate a procedure of assembling the rectangular secondary battery according to the embodiment.

FIG. 3 illustrates the procedure of assembling the rectangular secondary battery according to the embodiment.

FIG. 4 illustrates the procedure of assembling the rectangular secondary battery according to the embodiment.

FIG. 5 A and FIG. 5 B illustrate the procedure of assembling the rectangular secondary battery according to the embodiment.

FIG. 6 illustrates the procedure of assembling the rectangular secondary battery according to the embodiment.

FIG. 7 A and FIG. 7 B illustrate a procedure of assembling a rectangular secondary battery according to another embodiment.

FIG. 8 A and FIG. 8 B illustrate the procedure of assembling the rectangular secondary battery according to the other embodiment.

FIG. 9 is a partial schematic perspective view of a structure of the current collector for electrode bodies with a wound structure.

FIG. 10 is a partial schematic perspective view of another structure of the current collector for electrode bodies with a wound structure.

FIG. 11 is a partial cross-sectional view of a structure of the current collector for a single electrode body.

Embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Modifications may be made as appropriate without departing from the scope of the advantages of the present invention.

FIG. 1 A and FIG. 1 B schematically show a configuration of a rectangular secondary battery according to an embodiment of the present invention. FIG. 1 A is a top view, while FIG. 1 B is a cross-sectional view taken along line Ib-Ib of FIG. 1 A .

As shown in FIG. 1 A and FIG. 1 B , in a rectangular secondary battery 1 according to this embodiment, an electrode body 10 , which is a power generation element, is housed together with an electrolyte in a rectangular battery case 11 . The structure of the electrode body 10 is obtained by stacking a positive electrode plate and a negative electrode plate with a separator (none of them are shown) interposed therebetween. The positive electrode plate includes a positive electrode active material layer on the surface of a positive electrode core, while the negative electrode plate includes a negative electrode active material layer on the surface of a negative electrode core. The battery case 11 has an opening sealed with a sealing plate 12 .

Each of the positive and negative electrode plates has exposures 10 a and 10 b , in which the active material layer is not formed, at the longitudinal ends of the sealing plate 12 . The exposures 10 a and 10 b extend oppositely along the longitudinal direction of the sealing plate 12 and are connected to positive and negative current collectors 20 A and 20 B, respectively. Specifically, the plurality of exposures 10 a and 10 b are jointed to the current collectors 20 A and 20 B, respectively, while being bundled. The joining may be laser welding, for example.

The materials of the current collectors 20 A and 20 B are not particularly limited as long as being free from the influence of positive and negative electrode potentials in the electrolyte. The materials may be the same as the materials of the exposures 10 a and 10 b of the positive and negative electrode plates, respectively, in one preferred embodiment. For example, in the case of a lithium ion secondary battery, the (positive) current collector 20 A connected to the exposure 10 a of the positive electrode plate is made of aluminum or an aluminum alloy in one preferred embodiment. The (negative) current collector 20 B connected to the exposure 10 b of the negative electrode plate is made of copper or a copper alloy in one preferred embodiment.

The positive and negative current collectors 20 A and 20 B are block bodies with a thickness along the width of the sealing plate 12 , and holes 23 A and 23 B at their ends closer to the sealing plate 12 . Connectors 22 A and 22 B are respectively inserted into the holes 23 A and 23 B in the current collectors 20 A and 20 B.

The connectors 22 A and 22 B are formed of tubular bodies (e.g., cylindrical bodies) with flanges which are joined to external terminals 21 A and 21 B, respectively. Accordingly, the current collectors 20 A and 20 B are respectively connected to the positive and negative external terminals 21 A and 21 B with the connectors 22 A and 22 B interposed therebetween which are inserted into the holes 23 A and 23 B.

The connectors 22 A and 22 B are insulated from the sealing plate 12 by insulating members (i.e., gaskets) 30 A and 30 B, respectively. The external terminals 21 A and 21 B are insulated from the sealing plate 12 by insulating members 31 A and 31 B, respectively.

The electrode body 10 and the current collectors 20 A and 20 B are wrapped in an insulating holder 40 and housed in the battery case 11 . The insulating holder 40 is in the shape of a bag open toward the sealing plate 12 . The material of the insulating holder 40 is not particularly limited, and examples thereof include resin sheets such as polypropylene (PP) and polyethylene (PET).

Now, a procedure of assembling the rectangular secondary battery 1 according to this embodiment will be described with reference to FIGS. 2 to 6 .

First, as shown in FIG. 2 A and FIG. 2 B , the electrode body 10 and the current collector 20 A (or 20 B) are prepared. As shown in FIG. 2 A , the electrode body 10 has positive and negative exposures 10 a and 10 b at both the longitudinal ends of the sealing plate 12 . As shown in FIG. 2 B , the current collector 20 A is a block body with a hole 23 A, into which the connector 22 A is inserted, at the end closer the sealing plate 12 . The negative electrode current collector 20 B has the same configuration. In the following description, the description of the current collector 20 B will be omitted.

Next, as shown in FIG. 3 and FIG. 4 , the two electrode bodies 10 A and 10 B with the same structure are arranged side by side along the width of the sealing plate 12 . The exposures 10 a and 10 a of the electrode bodies 10 A and 10 B sandwich the current collector 20 A. The exposures 10 a and 10 a and the current collector 20 A are joined by laser welding, for example, in a joint area 24 .

Next, as shown in FIG. 5 A and FIG. 5 B , the current collector 20 A is fixed to the sealing plate 12 and the external terminal 21 A. Here, FIG. 5 A is an enlarged partial perspective view of portion around the sealing plate 12 of the current collector 20 A. FIG. 5 B is a partial cross-sectional view taken along line Vb-Vb of FIG. 5 A .

As shown in FIG. 5 A and FIG. 5 B , the insulating member (i.e., the gasket) 30 A, the sealing plate 12 , the insulating member 31 A, and the external terminal 21 A are placed in this order on the current collector 20 A. Each of the insulating member 30 A, the sealing plate 12 , the insulating member 31 A, and the external terminal 21 A has a through-hole in a corresponding position to the hole 23 A of the current collector 20 A. In addition, the insulating member 30 A has an outer periphery abutting on the inner peripheral surface of a through-hole 12 a in the sealing plate 12 .

Then, the connector 22 A passes through the through-holes in the insulating member 30 A, the sealing plate 12 , the insulating member 31 A, and the external terminal 21 A, and press-fitted into the hole 23 A of the current collector 20 A. Accordingly, the current collector 20 A is fixed to the connector 22 A more firmly. At this time, a compressed insulating member (i.e., gasket) 30 A is interposed between the inner peripheral surface of the through-hole 12 a in the sealing plate 12 and the outer peripheral surface of the connector 22 A, and between the bottom surface of the sealing plate 12 and the upper surface of the current collector 20 A.

After that, the flange of the connector 22 A and the external terminal 21 A are welded with laser, for example, to melt-bond the connector 22 A and the external terminal 21 A, which further reduces the electrical resistance.

When the connector 22 A is press-fitted into the hole 23 A, the space inside the hole 23 A is gradually compressed. That is, the connector 22 A gradually has difficulty in being press-fitted and may not reach a predetermined depth. In order to solve this problem, as shown in FIG. 5 B , the connector 22 A has a continuous hole 26 A causing the hole 23 A to communicate with the outside in one preferred embodiment. Accordingly, the connector 22 A can be press-fitted to a predetermined depth of the hole 23 A, while releasing the air inside the hole 23 A through the continuous hole 26 A to the outside.

Next, as shown in FIG. 6 , the sealing plate 12 , to which the current collector 20 A, the connector 22 A, and the external terminal 21 A are integrally fixed, is inserted into the insulating holder 40 . The electrode body 10 and the current collector 20 A wrapped in the insulating holder 40 are then housed in the battery case 11 . After that, the end of the battery case 11 closer to the opening and the outer periphery of the sealing plate 12 are welded with laser, for example, to seal the battery case 11 . At the end, an electrolyte is poured into the battery case 11 through a liquid inlet (not shown) in the sealing plate 12 , and then the liquid inlet is closed with a plug 50 (see FIG. 1 ).

According to this embodiment, the connector 22 A connecting the current collector 20 A and the external terminal 21 A is a tubular body, which provides a larger cross-sectional area for flowing a current than in typical fastening by crimping a rivet. Accordingly, the electrical resistance decreases at the connector 22 A, which generates less Joule heat even when a large current flows through the connector 22 A. This results in less temperature rise inside the battery.

In this embodiment, the two electrode bodies 10 A and 10 B are arranged side by side along the width of the sealing plate 12 . As shown in FIG. 4 , the exposures 10 a and 10 a of the electrode bodies 10 A and 10 B sandwich the current collector 20 A to be jointed to the current collector 20 A. The block body of the current collector 20 A has thus a greater thickness along the width of the sealing plate 12 . This increases the cross-sectional area of the current collector 20 A and eventually the inner diameter of the hole 23 A. As a result, the outer diameter of the connector 22 A increases, which reduces temperature rise inside the battery more advantageously.

In this embodiment, portion of the (positive electrode) connector 22 A connected to the positive electrode current collector 20 A is located in the battery case 11 below the sealing plate 12 . However, as shown in FIG. 5 B , the compressed insulating member (i.e., gasket) 30 A is interposed between the inner peripheral surface of the through-hole 12 a in the sealing plate 12 and the outer peripheral surface of the connector 22 A, and between the bottom surface of the sealing plate 12 and the upper surface of the current collector 20 A. That is, the connector 22 A press-fitted into the hole 23 A of the current collector 20 A is isolated from the space inside the battery case 11 by the insulating member (i.e., the gasket) 30 A and the current collector 20 A. The connector 22 A does not come into contact with the electrolyte in the battery case 11 and is thus free from the influence of the electrolyte, even if the positive electrode connector 22 A is made of copper or a copper alloy.

Accordingly, the positive electrode connector 22 A is made of copper or a copper alloy instead of typically used aluminum or an aluminum alloy to further reduce the electrical resistance at the connector 22 A. As a result, less Joule heat is generated even when a large current flows through the connector 22 A, which further reduces temperature rise inside the battery. If the positive electrode connector 22 A is made of copper or a copper alloy, the external terminal for the positive electrode (i.e., the positive electrode external terminal) 21 A may also be made of copper or a copper alloy.

In this embodiment, the connector 22 A is press-fitted into the hole 23 A of the current collector 20 A to fix the current collector 20 A. This causes less contact resistance between the connector 22 A and the current collector 20 A than in typical fastening by crimping a rivet. Accordingly, less Joule heat is generated at the connector 22 A, which further reduces temperature rise inside the battery.

While the present invention has been described with reference to a preferred embodiment, such description is not limiting, and various modifications may be made.

For example, while the connector 22 A is the tubular body with the flange in the embodiment described above, the configuration is not limited thereto. The connector 22 A may be a bolt, for example.

FIGS. 7 A, 7 B, 8 A, and 8 B illustrate an assembly procedure where the connector 22 A is a bolt. Here, FIG. 7 A is an enlarged partial perspective view of portion around the sealing plate 12 of the current collector 20 A, while FIG. 7 B is a partial cross-sectional view taken along line VIIb-VIIb of FIG. 7 A . Here, FIG. 8 A is an enlarged partial perspective view of portion around the sealing plate 12 of the current collector 20 A, while FIG. 8 B is a partial cross-sectional view taken along line VIIIb-VIIIb of FIG. 8 A .

As shown in FIG. 7 A and FIG. 7 B , the insulating member (i.e., the gasket) 30 A, the sealing plate 12 , and an insulating member 32 A are placed in this order on the current collector 20 A. Each of the insulating member 30 A, the sealing plate 12 , and the insulating member 32 A has a through-hole in a corresponding position to the hole 23 A (with an internal thread) of the current collector 20 A. In addition, the insulating member 30 A has an outer periphery abutting on the inner peripheral surface of the through-hole in the sealing plate 12 .

Next, the connector 22 A passes through the through-holes in the sealing plate 12 and the insulating member 32 A, and fastened with a bolt to the hole 23 A (with the internal thread) of the current collector 20 A. Accordingly, the current collector 20 A and the insulating member 30 A are fixed to the sealing plate 12 by the connector 22 A. Note that the connector 22 A may have a continuous hole 26 A causing the space inside the hole 23 A (with an internal thread) to communicate with the outside.

Next, as shown in FIG. 8 A and FIG. 8 B , the insulating member 31 A and the external terminal 21 A are placed on the sealing plate 12 , and the flange of the connector 22 A and the external terminal 21 A are welded with laser, for example. Accordingly, the connector 22 A and the external terminal 21 A are melt-bonded, which further reduces the electrical resistance.

Even the connector 22 A, which is a bolt, secures a larger cross-sectional area, through which a current flows, than in typical fastening by crimping with a rivet, which reduces the electrical resistance at the connector 22 A. Accordingly, less Joule heat is generated even when a large current flows through the connector 22 A, which reduces temperature rise inside the battery.

The connector 22 A fastened to the hole 23 A (with the internal thread) of the current collector 20 A with the bolt is isolated from the space inside the battery case 11 by the insulating member (i.e., the gasket) 30 A and the current collector 20 A. The connector 22 A does not come into contact with the electrolyte in the battery case 11 and is thus free from the influence of the electrolyte, even if the positive electrode connector 22 A is made of copper or a copper alloy. Accordingly, the connector 22 A is made of copper or a copper alloy to further reduce the electrical resistance at the connector 22 A. As a result, less Joule heat is generated even when a large current flows through the connector 22 A, which further reduces temperature rise inside the battery.

In the embodiment described above, the connector 22 A and the external terminal 21 A are separate components. Alternatively, the connector 22 A and the external terminal 21 A may be integrally formed into a single member. In addition, the connector 22 A has a solid structure in one preferred embodiment, but may have a partially hollow structure.

In addition, in the embodiment described above, each electrode body is obtained by stacking the positive and negative electrode plates with the separator interposed therebetween. Alternatively, the positive and negative electrode plates may be wound with a separator interposed therebetween.

FIG. 9 is a partial perspective view schematically showing a structure of the current collector 20 A for the electrode body 10 A with the wound structure.

As shown in FIG. 9 , the electrode bodies 10 A and 10 B have a plurality of exposures 10 a at the longitudinal ends of the sealing plate 12 of wound electrode plates. Each of the exposures 10 a is compressed at a middle area P in the height direction of the battery case 11 , while being bundled.

On the other hand, the current collector 20 A is placed while being sandwiched between the exposures 10 a and 10 a of the electrode bodies 10 A and 10 B. At this time, in a middle area Q in the height direction of the battery case 11 , the current collector 20 A has, along the width of the sealing plate 12 , a width increasing toward the exposures 10 a and 10 a to come into contact with the exposures 10 a and 10 a . Accordingly, in the areas P and Q, the current collector 20 A and the exposures 10 a and 10 a are joined by laser welding, for example.

The current collector 20 A has a solid structure in FIG. 9 , but may have a hollow structure as shown in FIG. 10 . In this case, the hole 23 A, into which the connector 22 A ( 22 B) is inserted, may be made as follows. The current collector 20 A may have, at the end closer to the sealing plate 12 , a cylindrical part 23 a with the hole 23 A.

In the embodiment described above, the two electrode bodies 10 A and 10 B with the same structure are arranged in the battery case 11 . Alternatively, a single electrode body may be placed. In this case, as shown in FIG. 11 , the electrode body 10 has, at the longitudinal ends of the sealing plate 12 , a plurality of exposures 10 a which are bundled at the transverse ends of the sealing plate 12 . Then, the exposures 10 a and the current collector 20 may be joined by laser welding, for example, with the current collector 20 abutting on the exposures 10 a.

In the embodiment described above, the current collectors 20 A and 20 B are connected to the exposures 10 a and 10 b at both edges of the positive and negative electrode plates, respectively. Alternatively, the current collector 20 may be connected to the exposures 10 a and 10 b of only one of the positive or negative electrode plate.

The type of the rectangular secondary battery according to this embodiment is not particularly limited. For example, the rectangular secondary battery is applicable to a lithium ion secondary battery, a nickel hydrogen secondary battery, or other batteries.

1 Rectangular Secondary Battery

10 , 10 A, 10 B Electrode Body

10 a , 10 b Exposure

11 Battery Case

12 Sealing Plate

12 a Through-hole

20 , 20 A, 20 B Current Collector

21 A, 21 B External Terminal

22 A, 22 B Connector

23 A, 23 B Hole

23 a Cylindrical Part

24 Joint Area

26 A, 26 B Continuous Hole

30 A, 30 B Insulating Member (Gasket)

31 A, 31 B Insulating Member

32 A Insulating Member

40 Insulating Holder

50 Plug