Battery pack, and resistance welding method and resistance welding device therefor

Abstract

To provide a battery pack that can be made compact and effectively cooled for each battery and that can improve the freedom of configuration of the battery pack, and a method and device for resistance-welding the battery pack.SOLUTION: A number of can-shaped batteries 1 are arranged radially with a positive electrodes 3 facing upward and a can bottoms 5 on the same plane, and the positive electrodes and the negative electrodes on the periphery 2 of the upper can in the same direction as the welding of the positive electrodes are resistance-welded by plate-shaped copper or copper alloy connecting members 7, 8, respectively, to electrically connect the batteries 1 together without using the can bottom side for electrical connection. The first connecting member 7 connecting the negative electrodes together has projections 14 that concentrate a welding current A at the welded points of the negative electrodes 2 on the periphery to suppress welding energy, and slits 15 that block the welding current A from the projections 14 to suppress heat generation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery pack in which a plurality of batteries are resistance-welded to a connecting member to electrically connect the batteries, and to a resistance welding method and device for the battery pack. [Background technology]

[0002] Generally, there is known an assembled battery (battery pack) in which a number of can-shaped batteries, such as cylindrical lithium-ion batteries, are arranged and electrically connected to plate-shaped connecting members (lead plates, tabs) that cover them by resistance welding (for example, Patent Document 1). Here, resistance welding refers to a method in which a pair of welding electrodes is brought into contact with a metal material, and a large current is passed through the material for a short period of time while applying pressure, utilizing the resistance heat of the metal to generate a nugget (alloy layer) and melt and connect the materials.

[0003] In recent years, high output is required for battery packs used in electric vehicles (EVs) and other devices, and there has been a trend toward transitioning connecting members from nickel (Ni) to copper (Cu) or copper alloys, which have higher electrical conductivity (lower electrical resistance) and higher thermal conductivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-119116 A Summary of the Invention [Problem to be solved by the invention]

[0005] When using such a battery pack, the batteries themselves generate heat during charging and discharging, and in order to suppress this heat generation, cooling is performed using air or water cooling methods. However, since the spaces between the batteries are covered with separate cases and the bottoms of the cans are hidden by connecting members (tabs), the batteries cannot be cooled directly, which means that the cooling equipment becomes larger and effective cooling can be difficult.

[0006] Furthermore, with conventional battery packs, connecting members must be welded to both the positive electrode (top lid) and the negative electrode (bottom of the can) of the battery. This means that both the top and bottom sides of each can-shaped battery must be used for connection, which limits the freedom of design of the battery pack.

[0007] An object of the present invention is to solve the above problems and to provide a battery pack, a resistance welding method and an apparatus therefor, which can reduce the size and effectively cool each battery and increase the freedom of design of the battery pack. [Means for solving the problem]

[0008] In order to achieve the above object, the resistance welding device for a battery pack according to the present invention arranges a number of can-shaped batteries in a radial direction with the positive electrodes of the upper lids facing upward and the bottoms of the cans on the same plane, and the positive electrodes and the negative electrodes on the periphery of the upper cans in the same direction as the welding of the positive electrodes are resistance-welded using plate-shaped copper or copper alloy connecting members, thereby electrically connecting the batteries without using the bottoms of the cans for electrical connection, The first connecting member that connects the negative electrodes together is formed with a projection that reduces welding energy by concentrating the welding current at the welding point on the peripheral edge of the battery, and a slit that blocks the welding current from the projection to reduce heat generation.

[0009] According to this configuration, multiple can-shaped batteries are arranged radially with the positive electrodes facing upwards and the bottoms of the cans on the same plane, and the first connecting member that connects the negative electrodes on the peripheral edge of the upper part of the cans is formed with a projection that concentrates the welding current at the welding point to reduce welding energy, and a slit that blocks the welding current from the projection to reduce heat generation, and the batteries are electrically connected to each other without using the bottom of the cans for electrical connection.Since the bottoms of the cans are used directly for cooling, each battery can be made small and effectively cooled, and electrical connection is possible only on the positive electrode side, improving the freedom of configuration of the battery pack.

[0010] Preferably, the first connecting member connecting the negative electrodes has a shape in which a hole for exposing the positive electrode and a ring-shaped portion for covering the negative electrode on the peripheral portion are formed, and the ring-shaped portions are connected to each other, and a plurality of projections extending in the radial direction are formed on the ring-shaped portion, and slits extending in a direction intersecting the radial direction are formed at the radial tip positions of the projections. In this case, the welding energy is suppressed by the plurality of projections extending in the radial direction formed on the ring-shaped portion, and the welding current is interrupted by the slits to suppress heat generation, so that the negative electrodes are electrically connected to each other without the peripheral portion being burned out by resistance welding. This allows the can bottom side to be used directly for cooling, making it possible to reduce the size and provide effective cooling, and improving the freedom of the battery pack configuration.

[0011] Preferably, the second connecting member connecting the positive electrodes has a projection for concentrating a welding current at a welding point of the positive electrodes and a slit for reducing unnecessary ineffective current passing through the connecting member. In this case, unnecessary ineffective current is reduced during resistance welding, and when the battery is assembled into a battery pack, an effective current path between the batteries can be secured.

[0012] Preferably, after the negative electrodes are connected to each other, the positive electrodes are connected to each other via an insulating separator that insulates the first connecting member of the negative electrodes from the second connecting member of the positive electrodes. In this case, the insulating separator can reliably insulate the first connecting member of the negative electrodes from the second connecting member of the positive electrodes.

[0013] The battery pack according to the present invention is formed by the resistance welding apparatus, and a coolant is provided at the bottom of each battery exposed on the same plane to directly cool the bottom of the battery. In this case, the bottom of each battery can be directly cooled by the coolant, which allows for compactness and effective cooling, and improves the freedom of the battery pack configuration.

[0014] A method for resistance welding a battery pack according to the present invention includes a first step of arranging a plurality of identical batteries in a radial direction with the positive electrodes of the top lids facing upward and the bottoms of the batteries on the same plane, and placing a plate-shaped first connecting member made of copper or copper alloy on the negative electrodes on the periphery of the upper part of the cans. The plate-shaped first connecting member has projections that concentrate a welding current at a welding point on the periphery to reduce welding energy, and slits that block the welding current from the projections to reduce heat generation. a second step of electrically connecting the negative electrodes to each other by resistance welding the first connecting member to the peripheral portion, and then placing an insulating separator on the first connecting member to insulate the first connecting member of the negative electrode from the second connecting member of the positive electrode; A third step of placing on the insulating separator a plate-shaped second connecting member made of copper or copper alloy, the second connecting member having a projection for concentrating a welding current at a welding point of the positive electrode and a slit for reducing unnecessary ineffective shunt current passing through the connecting member; and a fourth step of resistance-welding the second connecting member to the positive electrode in the same direction as the welding of the negative electrode, thereby electrically connecting the positive electrodes to each other, and electrically connecting the batteries to each other without using the can bottoms for electrical connection; Includes.

[0015] According to this configuration, multiple can-shaped batteries are arranged radially with the positive electrodes facing upwards and the bottoms of the cans on the same plane, and the first connecting member connecting the negative electrodes is formed with a projection that concentrates the welding current at the welding points on the periphery of the batteries to reduce welding energy, and a slit that blocks the welding current from the projection to reduce heat generation.Since the batteries are electrically connected to each other without using the bottom sides of the cans for electrical connections, the can bottoms can be used directly for cooling, allowing for compactness and effective cooling, and improving the freedom of design of the battery pack. Effect of the Invention

[0016] In the present invention, multiple can-shaped batteries are arranged radially with the positive electrodes facing upwards and the bottoms of the cans on the same plane, and the first connecting member that connects the negative electrodes at the peripheral edges is formed with a projection that concentrates the welding current at the welding point to reduce welding energy, and a slit that blocks the welding current from the projection to reduce heat generation, and the batteries are electrically connected to each other without using the can bottom side for electrical connection.Since the bottoms of the cans are used directly for cooling, compactness and effective cooling are possible, and electrical connection is possible only on the positive electrode side, improving the freedom of configuration of the battery pack. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1A is a perspective view showing an example of a can-shaped battery used in a resistance welding device for a battery pack of the present invention, and FIG. [Diagram 2] 1 is a front view showing a resistance welding device for a battery pack according to an embodiment of the present invention; [Diagram 3] 1 is a front view showing a resistance welding device for a battery pack according to an embodiment of the present invention; [Figure 4] FIG. 4 is a plan view showing an example of a second connecting member that connects negative electrodes together in the present invention. [Diagram 5] FIG. 2 is a partial vertical cross-sectional view showing an example of an assembled battery pack according to the present invention. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1(A) is a perspective view showing an example of a can-shaped battery 1 used in the resistance welding device for a battery pack of the present invention, and Fig. 1(B) is a partial vertical cross-sectional view thereof. As shown in Fig. 1(A), the top cap protrusion 3 of this battery 1 is the positive electrode (+), and the rim part (shoulder of the battery) 2 at the top of the can and the can bottom 5 are the negative electrodes (-). As shown in Fig. 1(B), the can bottom 5 and the rim part 2 are connected via the exterior can 4 of the battery 1 to form the negative electrode (-). A sealing packing 6 is provided between the positive electrode (+) and the negative electrode (-). In the present invention, the negative electrode (-) of the rim part 2 is resistance welded.

[0019] In this example, multiple identical can-shaped batteries 1 are arranged radially with the positive electrodes (+) 3 of each top lid facing upwards, so that the positive electrodes (+) 3 are flush with the can bottoms 5. The negative electrodes (-) of the peripheral portions (battery shoulders) 2 are resistance-welded together in the same welding direction by plate-shaped first connecting members (tabs) 7, and the positive electrodes (+) of the battery protrusions 3 are resistance-welded together by plate-shaped second connecting members (tabs) 8. In other words, the connections of the batteries 1 can be consolidated only on the positive electrode side, so that the batteries 1 are electrically connected together without using the negative electrodes (-) of the can bottoms 5 for electrical connection as in the past.

[0020] The can-shaped battery 1 is, for example, a cylindrical lithium ion battery, and the plate-shaped first and second connecting members 7, 8 are made of, for example, copper or a copper alloy. Nickel, which has a lower electrical conductivity than copper, may also be used.

[0021] Fig. 2 is a front view showing a state in which a negative electrode 2 and a first connecting member 7 are welded in a resistance welding device for a battery pack according to one embodiment of the present invention, and Fig. 3 is a front view showing a state in which a positive electrode 3 and a second connecting member 8 are welded in the same device.

[0022] As shown in FIG. 2, a pair of welding electrodes 10, 11 are supplied with power from a welding power source (not shown), and each of the pair of welding electrodes 10, 11 is brought into contact with, for example, a pair of opposing welding points on the peripheral portion (negative electrode) 2 of a battery 1, on the outer surface of the first connecting member 7 opposite the negative electrode 2 of the battery 1, and electricity is passed between the welding electrodes 10, 11 so that a welding current A flows.

[0023] The first connecting member 7 connecting the negative electrodes together has projections 14 that concentrate the welding current A at the welding points of the peripheral portion (negative electrode) 2 to minimize the welding energy, and slits 15 that block the welding current A from the projections 14 to suppress heat generation. The welding current A is forcibly induced to pass through these projections 14, forming a nugget (alloy layer) N due to resistance heating between the first connecting member 7 and the negative electrode 2 of the battery 1, and the negative electrode 2 of the battery 1 is resistance welded to the first connecting member 7. The negative electrodes 2 of the other batteries 1 are then resistance welded in the same manner, and the negative electrodes 2 of the batteries 1 are connected together via the first connecting member 7.

[0024] That is, as shown in FIG. 4, the first connecting member 7 has a shape in which a plurality of holes 16 are formed to expose the positive electrode 3 for welding by the second connecting member 8 described later, and a plurality of annular portions 17 are formed to cover the negative electrode 2 at the peripheral portion, and the annular portions 17 are connected to each other, and a plurality of projections 14 extending radially, for example a pair of opposing projections 14, are formed at the radial tip positions of the projections 14, and a slit 15 is formed that extends in a direction that intersects with the radial direction, for example perpendicular to the radial direction.

[0025] The welding power source used may be, for example, a high-energy type welding power source with a large-capacity capacitor that can pass a large current in a short time. This, combined with the effects of the projections 14 and slits 15, safely protects the sealing packing 6 (Fig. 1(B)) of the battery 1 even if it is directly under the welding point, making it possible to safely prevent leakage.

[0026] As shown in FIG. 3, a pair of welding electrodes 10, 11 are supplied with power from a welding power source (not shown), and each of the pair of welding electrodes 10, 11 straddles slit 22 and contacts the outer surface of second connecting member 8 opposite the positive electrode 3 of battery 1, causing electricity to flow between the welding electrodes 10, 11 and causing welding current A1 to flow.

[0027] 8, the second connecting member 8 has a shape in which a plurality of welded portions 18 are formed so as to cover and contact the welded portions of each positive electrode 3, and annular portions 19 are connected to the welded portions 18, and the annular portions 19 are connected to each other. The welded portions 18 have, for example, two projections 21 formed at each welded portion of the positive electrode 3 of each battery 1, facing the other adjacent battery with a slit 22 in between, for a total of four projections 21.

[0028] 3 is forcibly induced to pass through this projection 21, forming a nugget (alloy layer) N due to resistance heating between the second connecting member 8 and the positive electrode 3 of the battery 1, and the positive electrode 3 of the battery 1 is resistance welded to the second connecting member 8. The positive electrodes 3 of the other batteries 1 are then resistance welded in the same way, and the positive electrodes 3 of the batteries 1 are connected together via the second connecting member 8.

[0029] 8 is formed with a hole so that the welded portion is recessed from the annular portion 19, and the slits 22 at the welded portion of the welded portion 18 communicate with the annular portion 19 via a step. The slits 22 extend in mutually opposite directions and spaced apart approximately parallel to one another between one battery 1 and the other battery 1 in the annular portion 19, and have a shape that reaches from one battery 1 to the vicinity of the welded portion of the other battery 1 beyond the midpoint between the batteries 1, 1.

[0030] In this way, the slits 22 overlap while being spaced apart and generally parallel to each other, so that the current (reactive shunt) flowing from unnecessary electrode 10 through second connecting member 8 to electrode 11 can be reduced by the length of the overlap. Furthermore, when made into a battery pack, the shape of the slits 22, which are inclined in opposite directions and spaced apart generally parallel to each other, allows the current between the positive electrodes of each battery 1 to flow diagonally between the slits 22, and the current path can be effectively secured to be large without being obstructed.

[0031] In this manner, the negative electrodes 2 of the batteries 1 are resistance-welded to each other by the first connecting members 7, and the positive electrodes 3 are resistance-welded to each other by the second connecting members 8, so that the batteries 1 are electrically connected to each other to form a battery pack 7.

[0032] Fig. 5 is a partial vertical cross-sectional view showing an example of an assembled battery pack 20. As shown in Fig. 5, the negative electrodes 2 of the batteries 1 are resistance-welded to each other by a first connecting member 7, and the positive electrodes 3 are resistance-welded to each other by a second connecting member 8, so that the batteries 1 are electrically connected to each other to form the battery pack 20. The first connecting member 7 of the negative electrode 2 and the second connecting member 8 of the positive electrode 3 are insulated by an insulating separator 9. As shown in Fig. 9, the insulating separator 9 has approximately the same outer shape as the first connecting member 7 without the projections 14 and slits 15 formed therein.

[0033] The can bottom 5 of each battery 1 in Fig. 5 is provided with a coolant 23 that directly cools it. In this case, the can bottom 5 of each battery 1 can be directly cooled by the coolant 23, which allows for compactness and effective cooling, and allows electrical connection only on the positive electrode side, improving the freedom of configuration of the battery pack 20.

[0034] 6 to 9 are perspective views showing the operation of the resistance welding device for a battery pack of the present invention. Fig. 6 shows the first step (step 1), in which a number of identical can-shaped batteries 1 are radially arranged with their positive electrodes 3 facing upward and their can bottoms 5 on the same plane, and a plate-shaped copper or copper alloy first connecting member 7 is placed on the negative electrodes 2 on the periphery, the projections 14 concentrating the welding current A at the welding points to suppress the welding energy, and the slits 15 blocking the welding current from the projections 14 to suppress heat generation.

[0035] FIG. 7 shows the second step (step 2), in which the first connecting member 7 is resistance welded to the negative electrode 2 at the peripheral portion to electrically connect the negative electrodes, and then an insulating separator 9 is placed on the first connecting member 7 to insulate the first connecting member 7 of the negative electrode 2 from the second connecting member 8 of the positive electrode 3.

[0036] FIG. 8 shows the third step (step 3), in which a plate-shaped second connecting member 8 made of copper or copper alloy is placed on an insulating separator 9. The second connecting member 8 has a projection 21 for concentrating the welding current A1 at the welding point of the positive electrode 3 and a slit 22 for reducing unnecessary reactive shunt current passing through the connecting member.

[0037] FIG. 9 shows the fourth step (step 4), in which the second connecting member 8 is resistance welded to the positive electrode 3 in the same direction as the welding of the negative electrode 2, electrically connecting each positive electrode to each other, and electrically connecting each battery 1 to each other without using the bottom sides of each can for electrical connection.

[0038] In this way, in the present invention, multiple can-shaped batteries 1 are arranged radially with the positive electrodes 3 facing upwards and the can bottoms 5 on the same plane, and the first connecting member 7 connecting the negative electrodes at the peripheral portion 2 of the upper part of the can is formed with a projection 14 that concentrates the welding current A at the welding point to minimize the welding energy, and a slit 15 that blocks the welding current A from the projection 14 to suppress heat generation, and the batteries 1 are electrically connected to each other without using the can bottom side for electrical connection. Therefore, by using each can bottom 5 for direct cooling, compactness and effective cooling are possible, and electrical connection is possible only on the positive electrode side, thereby improving the freedom of configuration of the battery pack 20.

[0039] The present invention is not limited to the above-described embodiment, and various additions, modifications, and deletions are possible without departing from the scope of the present invention. Therefore, such modifications are also included in the scope of the present invention. [Explanation of symbols]

[0040] 1:Battery 2: Negative electrode (the rim of the upper part of the can) 3: Positive electrode (protruding part) 5: Can bottom 7: First connecting member 8: Second connecting member 10, 11: Welding electrodes 14: Projection 15: Slit 16: Hole 17: Ring section 20: Battery pack 21: Projection 22: Slit A, A1: Welding current

Claims

1. A resistance welding device for a battery pack, in which a number of can-shaped batteries are arranged in a radial direction with the positive electrodes of the upper lids facing upward and the bottoms of the cans on the same plane, and the positive electrodes and the negative electrodes on the periphery of the upper cans in the same direction as the welding of the positive electrodes are resistance-welded to each other using plate-shaped copper or copper alloy connecting members, so that the batteries are electrically connected to each other without using the bottoms of the cans for electrical connection, A resistance welding device for a battery pack, in which a first connecting member that connects the negative electrodes together is formed with a projection that reduces welding energy by concentrating a welding current at the welding point on the peripheral edge of the negative electrode, and a slit that blocks the welding current from the projection to reduce heat generation.

2. In claim 1, A resistance welding device for a battery pack, wherein a first connecting member connecting the negative electrodes has a shape in which a plurality of holes exposing the positive electrodes and annular portions covering the peripheral portions of the negative electrodes are formed, the annular portions are connected to each other, a plurality of projections extending radially are formed on the annular portions, and slits extending in a direction intersecting the radial direction are formed at the radial tip positions of the projections.

3. In claim 1, A resistance welding device for a battery pack, wherein a second connecting member that connects the positive electrodes together is formed with a projection that concentrates welding current at the welding point of the positive electrodes and a slit that reduces unnecessary reactive shunt current passing through the connecting member.

4. In claim 3, A resistance welding device for a battery pack, wherein after the negative electrodes are connected to each other, the positive electrodes are connected to each other via an insulating separator that insulates the first connecting member of the negative electrodes from the second connecting member of the positive electrodes.

5. A battery pack formed by the resistance welding device according to any one of claims 1 to 4, In this battery pack, the bottom of each battery is exposed and arranged on the same plane, and a coolant is provided to directly cool the bottom of the battery.

6. a first step of arranging a plurality of can-shaped batteries in a radial direction with the positive electrodes of the top lids facing upward and the bottoms of the cans on the same plane, and placing a plate-shaped first connecting member made of copper or copper alloy on the negative electrodes on the periphery of the upper part of the cans, the plate-shaped first connecting member having a projection for concentrating a welding current at a welding point of the negative electrode to suppress welding energy and a slit for blocking the welding current from the projection to suppress heat generation; a second step of electrically connecting the negative electrodes to each other by resistance welding the first connecting member to the peripheral portion of the battery, and then placing an insulating separator on the first connecting member to insulate the first connecting member of the negative electrode from the second connecting member of the positive electrode; A third step of placing on the insulating separator a plate-shaped second connecting member made of copper or copper alloy, the second connecting member having a projection for concentrating a welding current at a welding point of the positive electrode and a slit for reducing unnecessary ineffective shunt current passing through the connecting member; and a fourth step of resistance-welding the second connecting member to the positive electrode in the same direction as the welding of the negative electrode, thereby electrically connecting the positive electrodes to each other, and electrically connecting the batteries to each other without using the bottom sides of the cans for electrical connection; A method for resistance welding a battery pack comprising:

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