WO2009002126A1

WO2009002126A1 - Secondary battery with a structure having electrode tabs drawn out in different direction and the fabrication method thereof, and battery module using the same

Info

Publication number: WO2009002126A1
Application number: PCT/KR2008/003750
Authority: WO
Inventors: Ki-Chun Kong; Byung-Sai Lee
Original assignee: Cm Partner Inc.
Priority date: 2007-06-28
Filing date: 2008-06-27
Publication date: 2008-12-31

Abstract

A secondary battery with a structure having electrode tabs drawn out in different directions, a fabrication method thereof, and a battery module using the same are disclosed. The secondary battery having a structure of electrode tabs drawn out in each different direction, includes: first and second electrodes which are alternately stacked; a separator interposed between the two electrodes; an electrolyte; a first electrode tab/side cover assembly formed by hermetically combining a first electrode tab combined with the first electrode and drawn out in a first direction and a first side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the first electrode tab; a second electrode tab/side cover assembly formed by hermetically combining a second electrode tab combined with the second electrode and drawn out in a second direction different from the first direction and a second side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the second electrode tab; and a case body having one side combined with the first side cover and a different side combined with the second side cover, accommodating the first and second electrodes, the separator, and the electrolyte, and being made of a non-conductive material.

Description

SECONDARY BATTERY WITH A STRUCTURE HAVING ELECTRODE

TABS DRAWN OUT IN DIFFERENT DIRECTION AND THE FABRICATION METHOD THEREOF. AND BATTERY MODULE USING

THE SAME

TECHNICAL FIELD

The present invention relates to a secondary battery with a structure having electrode tabs drawn out in different directions, a fabrication method thereof, and a battery module using the same.

BACKGROUND ART

In general, unlike a primary battery that is not available for re-charging, a secondary battery refers to a battery that can be re-chargeable or dischargeable. Recently, a high output secondary battery using nonaqueous electrolyte of a high energy density is being developed.

A low-capacity battery in which a unit cell is wrapped in a pack is used for a small portable electronic device such as cellular phones, notebook computers, or camcorders. In case of a power source for driving motors of an electric vehicle that requires large power, tens of unit cells are connected in series and/or in parallel to form a large capacity battery module.

As shown in FIGs. 1 and 2, the related art large capacity battery module includes terminals installed only on one surface of the battery (an upper surface in the drawings), having the following problems. i First, because the first and second electrodes are formed in the same direction, there is a probability of a short circuit in manufacturing the battery.

Second, when the unit cells are connected in series and/or parallel, the fastening portion is too narrow to cause a short circuit in the process of fabricating the battery module and inconvenience of operation.

Third, because current generated by the first and second electrodes should be drawn out in only one direction, the sectional areas of the first and second electrode tabs are small. In addition, the first and second terminals connected with the electrode tabs via leads or the like have a shape of a screw or a small ring with a small sectional area, so the terminal resistance is high.

Fourth, the shortcomings of the high terminal resistance relates to the performance of the battery. That is, the performance of the battery is considerably degraded at a low temperature at which mobility of ions is degraded. Because the area of the terminal is small, heat is excessively generated from the electrode tab or the terminal of the battery in charging or discharging with high efficiency.

Fifth, because the battery should be manufactured in a vertical direction, there is a limitation in designing the battery module for combining the unit cells in series or in parallel.

Sixth, as for connections of the unit cells, electric wires or a battery connection rings are fastened by using bolts or nuts, the operation is difficult to perform and much time is required, degrading the efficiency of the battery.

Seventh, because the electrode tabs or terminals are combined with the case by tightening screws, an electrolyte of the interior of the battery may be leaked.

DISCLOSURE OF THE INVENTION

Therefore, a first object of the present invention is to solve a problem of the possible a short circuit that may occur in manufacturing a battery by drawing out first and second electrode tabs in each different direction, solve a problem of the danger of a short circuit that may occur in manufacturing a battery module, and widen designing of the battery module.

A second object of the present invention is to immediately draw electricity generated by electrodes out of a case without using components, use an electrode tab with a large area, improve a charging and discharging efficiency of a battery, improve low temperature characteristics and high rate discharge characteristics, and minimize a terminal resistance.

A third object of the present invention is to simply implement configurations of various battery modules by simply bending electrode tabs and combining them in connecting unit cells in series and in parallel.

A fourth object of the present invention is to reduce time and costs incurred for manufacturing a battery by combining a plurality of stacked electrodes and electrode tabs in a simple manner.

A fifth object of the present invention is to prevent a problem of a leakage of an electrolyte from the interior of a battery by injection-molding a case with an electrode tab inserted at the center.

(1 ) To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a secondary battery having a structure of electrode tabs drawn out in each different direction, including: first and second electrodes which are alternately stacked; a separator interposed between the two electrodes; an electrolyte; a first electrode tab/side cover assembly formed by hermetically combining a first electrode tab combined with the first electrode and drawn out in a first direction and a first side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the first electrode tab; a second electrode tab/side cover assembly formed by hermetically combining a sejcond electrode tab combined with the second electrode and drawn out in a second direction different from the first direction and a second side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the second electrode tab; and a case body having one side combined with the first side cover and a different side combined with the second side cover, accommodating the first and second electrodes, the separator, and the electrolyte, and being made of a non-conductive material.

(2) To achieve the above objects, there is provided a battery module comprising a plurality of secondary batteries of (1), wherein a first electrode tab of one secondary battery is combined to be connected in series with a second electrode tab of another secondary battery.

(3) To achieve the above objects, there is provided a battery module comprising a plurality of secondary batteries of (1 ), wherein a plurality of first electrode tabs are combined with each other and a plurality of second electrode tabs are combined with each other so as to be connected in parallel.

(4) To achieve the above objects, there is provided a battery module comprising a plurality of secondary batteries of (1), wherein at least one first electrode tab of a group of secondary batteries connected in parallel and at least one second electrode tab of a different group of secondary batteries connected in parallel are directly or indirectly combined so as to be connected in series.

(5) To achieve the above objects, there is also provided a method for fabricating a secondary battery with a structure having electrode tabs drawn out in different directions, including: alternately stacking first and second electrodes with separators interposed therebetween such that a first uncoated portion without an active material of each first electrode and a second uncoated portion without an active material of each second electrode do not overlap with each other; inserting the first electrode tab penetrating a first side cover without a gap between two adjacent first uncoated portions among the plurality of first uncoated portions all stacked to face a first direction, and allowing two first uncoated portions positioned at the outermost portions to come in contact with a welding bar to simultaneously weld the plurality of first uncoated portions and the first electrode tab; inserting the second electrode tab penetrating a second side cover without a gap between two adjacent second uncoated portions annong the plurality of second uncoated portions all stacked to face a second direction, and allowing two second uncoated portions positioned at the outermost portions to come in contact with a welding bar to simultaneously weld the plurality of second uncoated portions and the second electrode tab to complete an electrode assembly; and putting the electrode assembly in a case body, combining the first and second side covers with the case body, impregnating an electrolyte in the electrode assembly, and then sealing the same.

According to the present invention, first, because the electrode tabs have a large area, the charging and discharging characteristics of the battery can be improve compared with that of an existing battery, a high rate charging and discharging can be possible, charging and discharge can be advantageously performed at a low temperature, and a terminal resistance can be considerably reduced.

Second, unlike the existing method in which two electrode tabs are all formed in one direction, the two electrodes and their electrode tabs of the battery are formed in different directions to solve the problem of a short circuit that may be generated in fabricating the battery.

Third, the simplicity of the battery modularization can be maximized. Fourth, because the case is injection-molded with the electrode tabs inserted at the central portion thereof, a leakage of the electrolyte at the interior of the battery can be prevented. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a photograph showing a related art battery module including unit cells connected in series. FIG. 2 is a vertical sectional view of a single unit cell of the battery module in FIG. 1.

FIG. 3 is a perspective view of a secondary battery according to an embodiment of the present invention.

FIG. 4 is a separative perspective view of a secondary battery in FIG. 3.

FIG. 5 is a separative perspective view of electrodes to be stacked according to the present invention.

FIGs. 6 and 7 are sectional views showing the state before and after electrodes and electrode tabs are welded according to the present invention.

FIG. 8 is a perspective view showing a side cover of a case injection-molded with an electrode tab inserted at the center thereof according to the present invention. FIG. 9 is a perspective view of a secondary battery with air cooling recesses formed on an outer surface of a case;

FIGs. 10 and 11 are perspective view and sectional view showing a battery module including unit cells connected in series according to the present invention; FIGs. 12 to 14 are perspective view and sectional view showing a battery module including unit cells connected in parallel according to the present invention; and

FIG. 15 is a sectional view showing a battery module including a group of unit cells, which are connected in parallel, and a different group of unit cells, which are connected in parallel, connected in series.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

With reference to FIGs. 3 and 4, a secondary battery 100 according to an embodiment of the present invention includes first and second electrodes 111 and 113 which are alternately stacked, a separator (not shown) interposed between the two electrodes 111 and 113, an electrolyte (not shown), a case 150 for accommodating the first and second electrodes, the separator and the electrolyte, and first and second electrode tabs 130 and 140 combined with the first and second electrodes 111 and 113 and drawn out in each different direction. In this embodiment, the first and second electrode tabs 130 and 140 are drawn out in the mutually opposite directions, but without being limited thereto, the first and second electrode tabs 130 and 140 may be drawn out in mutually right angle directions.

In the related art as shown in FIGs. 1 and 2, because the first and second electrode tabs are drawn out in one direction, there is a high possibility that the electrodes are short-circuited, and because the area of the electrode tabs is small, a resistance loss is severe in the process of drawing out electricity generated from the electrodes. However, in the present invention, as shown in FIGs. 3 and 4, because the first and second electrode tabs 130 and 140 are drawn out in the mutually opposite directions, the inter-electrode short circuit can be prevented, and because the area of the electrode tabs is increased, the resistance loss can be minimized.

In order to draw out the first and second electrode tabs 130 and 140 in the mutually opposite directions, the electrodes according to this embodiment have such a stacked structure as shown in FIG. 5. Namely, the first and second electrodes 111 and 113 are alternately stacked such that a first coated portion 111a and a second coated portion 113a face with a separator 112 interposed therebetween while a first uncoated portion 111 b and a second uncoated portion 113b are disposed not to overlap with each other.

Here, the first coated portion 111a is a portion where a first active material is coated on a first current collector. The first uncoated portion 111b is a portion where the first current collector is exposed without the first active material. The second coated portion 113a is a portion where a second active material is coated on a second current collector. The second uncoated portion 113b is a portion where the second current collector is exposed without the second active material. Preferably, the first and second coated portions 111a and 113a are stacked such that they accurately overlap with each other with the same area, and the separator 112 is formed to be slightly larger than the area of the first and second coated portions 111a and 113a to prevent a short circuit between the two coated portions. Preferably, the first and second uncoated portions 111b and 113b are disposed in directions in which the electrode tabs are desired to be drawn out. In this embodiment, because the two electrode tabs are drawn out in the mutually opposite directions, the first and second uncoated portions 111b and 113b are disposed in the mutually opposite directions. In order to draw out electricity generated by the first and second electrodes 111 and 113, the first and second electrode tabs 130 and 140 are combined in such a manner as shown in FIGs. 6 and 7.

Namely, the first electrode tab 130 is inserted between two first uncoated portions at a central portion among a plurality of first uncoated portions 111 b, and then, a welding bar is applied to come in contact with the two first uncoated portions positioned at outermost positions (i.e., the uppermost and lowermost positions on the drawing) to simultaneously weld the plurality of first uncoated portions 111b and the first electrode tab 130 (FIG. 6). Accordingly, the other first adjacent uncoated portions than the two adjacent first uncoated portions at the central portion are combined through welding (FIG. 7). For reference, the separator is not shown in FIG. 7 for the sake of brevity, but actually, the separator 112 is interposed between the two electrodes as shown in FIG. 6. Similarly, the second electrode tab 140 is inserted between two adjacent second uncoated portions at the central portion among a plurality of second uncoated portions 113b, and then, the welding bar is applied to com in contact with the two second uncoated portions positioned at the outermost positions (i.e., the uppermost and lowermost positions on the drawing) to simultaneously weld the plurality of second uncoated portions 113b and the second electrode tab 140 (FIG. 6). Accordingly, the other second adjacent uncoated portions than the two adjacent second uncoated portions at the central portion are combined through welding (FIG. 7).

In the related art, the homogeneous electrode tabs drawn out of the homogeneous electrodes should be welded to each other, and each electrode and each electrode tab should be welded to each other, causing a problem that the operation time and costs increase and the electric resistance also increase.

However, in the present invention, because the single large electrode tab and the plurality of electrodes are combined through single welding, the operation time and costs can be considerably reduced and a loss of electric resistance can be minimized.

Also, in the present invention, as shown in FIG. 8, in a state that the electrode tab 130 is positioned at a certain position of a mold pattern (not shown) for injection-molding a side cover 151 of the case such that the electrode tab 130 penetrates a central portion of the side cover without a gap, and the side cover 151 is injection-molded. Namely, in the present invention, the electrode tab/side cover assembly is prepared by hermetically combining the electrode tab 130 and the side cover 151 , the electrode tab 130 is welded with the electrodes (See FIGs. 6 and 7), and then, the side cover 151 is combined with the case body (See FIG. 4). Here, the side cover 151 is made of a non-conductive material such as polypropylene, nylon, reinforced plastic, or the like. The electrode tab 130 may be made of a conductive material such as copper, nickel, aluminum, iron, or the like.

Accordingly, the electrode tab 130 may be inserted into the side cover 151 of the case without a gap, and the thusly assembled battery does not have a possibility that the electrolyte within the battery cannot be leaked because there is no seamed portion unlike the related art.

In addition, because the large electrode tab is drawn out without using components in the process of drawing out electricity generated from the electrodes, the electrical conductivity, the charging and discharging efficiency, the low temperature characteristics and the high rate discharge characteristics can be remarkably improved.

Air cooling recesses 147 as shown in FIG. 9 may be formed on the external portion of the secondary battery case to improve heat release characteristics of the battery. The air cooling recesses 147 are passages along which air flows, increasing the surface area of the external portion of the case that comes in contact with air. In addition, battery fixing holes 159 may be formed on the external portion of the case to fix the position of the battery.

A method for fabricating the secondary battery according to the present invention will now be described.

First, as shown in FIG. 5, in a state that the separator 112 is interposed between the first and second electrodes 111 and 113, the first and second electrodes 111 and 113 are alternately stacked such that the first uncoated portion 111b without the active material of the first electrode 111 and the second uncoated portion 113b without the active material of the second electrode 113 do not overlap with each other. In this embodiment, the first and second uncoated portions 111 b and 113b are stacked such that the face in the mutually opposite directions.

Next, as shown in FIGs. 6 and 7, the first electrode tab 130 penetrating the first side cover 151 without a gap is inserted between two adjacent first uncoated portions among the plurality of first uncoated portions 111 b staked toward the first direction, and a welding bar comes in contact with two first uncoated portions positioned at the outermost portions to simultaneously weld the plurality of first uncoated portions 111b and the first electrode tab 130.

And then, as shown in FIGs. 6 and 7, simultaneously when or after the welding process of the first electrode tab 130 is performed, the second electrode tab 140 penetrating the second side cover 152 without a gap is inserted between two adjacent second uncoated portions among the plurality of second uncoated portions 113b staked toward the second diirection, and the welding bar comes in contact with two second uncoated portions positioned at the outermost portions to simultaneously weld the plurality of second uncoated portions 113b and the second electrode tab 140, to thus complete an electrode assembly. The welding process may be performed before the welding process of the first electrode tab.

Thereafter, as shown in FIG. 4, the electrode assembly is put in the case body 153, the first and second side covers 151 and 152 and the case body 153 are combined, an electrolyte (not shown) is impregnated to the electrode assembly, and the upper cover 154 covers the case body in a sealing manner to thus complete a battery. In a different embodiment, if an electrolyte injection hole (not shown) is separately formed at the case, the electrolyte may be impregnated through the electrolyte injection hole after the case is covered by the upper cover 154, and then, the electrolyte injection hole may be sealed. In a still different embodiment, the case body 153 and the upper cover 151 may be integrally formed.

A battery module configured as the thusly fabricated secondary batteries (called 'unit cells' so as to be discriminated from the battery module) are connected in series and/or in parallel will now be described. First, the battery module including the unit cells connected in series will now be described with reference to FIGs. 10 and 11. In a battery module 200 according to an embodiment of the present invention, a first electrode tab 231 of one unit cell (e.g., 230) is connected in series with a second electrode tab 243 of another unit cell 240.

As shown, a plurality of unit cells 210, 220, 230, 240, 250 and 260 are stacked such that polarities of the unit cells are alternately arranged. But the present invention is not limited thereto, and the unit cells may be arranged on a plane (to be level with each other) to complete a battery module. Namely, according to the present invention, the battery module can be designed in various manners.

In the present invention, the unit cells may be connected in series by simply bending and welding the electrode tabs. For example, the first electrode tab 231 of the unit cell 230 is bent at 90° downwardly, the second electrode tab 243 of the unit cell 240 is bent at 90° upwardly toward the first electrode tab, and then the two electrode tabs 231 and 243 are welded. In this manner, the unit cells can be connected in series.

Accordingly, in fabricating the battery module, the space utilization can be maximized, various configurations of battery modules can be simply implemented, and time and costs for fabricating the battery module can be considerably reduced.

Next, a battery module having unit cells connected in parallel will now be described with reference to FIGs. 12 to 14. In a battery module 300 according to a different embodiment of the present invention, a plurality of first electrode tabs 311 , 321 , 331 , 341 , 351 and 361 are connected in series with each other, and a plurality of second electrode tabs (not shown) are connected in series with each other. As illustrated, the plurality of unit cells 310, 320, 330, 340, 350, and

360 are stacked such that their polarities are arranged to be the same. Namely, the plurality of first electrode tabs are 311 , 321 , 331 , 341 , 351 and

361 are directed in the first direction, while the plurality of second electrode tabs are directed in the second direction, the opposite to the first direction. But the present invention is not limited thereto, and the unit cells may be arranged on a plane (to be level with each other) to complete a battery module.

A battery module including the unit cells connected in series or in parallel will now be described with reference to FIG. 15. In a battery module 400 according to an embodiment of the present invention, at least one first electrode tab 431 in a group of primary cells connected in parallel (e.g., a group of unit cells 420 and 430) and at least one second electrode tab 453 in a group of secondary cells connected in parallel (e.g., a group unit cells 440 and 450) are combined to be connected in series. Here, as shown in FIG. 15, the first electrode tab 431 and the second electrode tab 453 are combined with a conductive connection member (B) by welding so as to be connected in series. But the present invention is not limited thereto, and the second electrode tab 453 may be formed to be long so as to be directly welded with the first electrode tab 431.

In addition, as illustrated, a plurality of unit cells 410, 420, 430, 440, 450, 460, 470 and 480 are stacked such that their polarities are arranged alternately by groups of the unit cells connected in series. But the present invention is not limited thereto, and the groups of stacked unit cells may be arranged on a plane (to be level with each other) to complete a battery module.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

1. A secondary battery having a structure of electrode tabs drawn out in each different direction, comprising: first and second electrodes which are alternately stacked; a separator interposed between the two electrodes; an electrolyte; a first electrode tab/side cover assembly formed by hermetically combining a first electrode tab combined with the first electrode and drawn out in a first direction and a first side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the first electrode tab; a second electrode tab/side cover assembly formed by hermetically combining a second electrode tab combined with the second electrode and drawn out in a second direction different from the first direction and a second side cover, an injection-molded member made of a non-conductive material, with a central portion penetrated by the second electrode tab; and a case body having one side combined with the first side cover and a different side combined with the second side cover, accommodating the first and second electrodes, the separator, and the electrolyte, and being made of a non-conductive material.

2. The battery of claim 1, wherein the first electrode comprises a first coated portion where a first active material is coated on a first current collector, and a first uncoated portion where the first current collector is exposed without the first active material, the second electrode comprises a second coated portion where a second active material is coated on a second current collector, and a second uncoated portion where the second current collector is exposed without the second active material, the first and second coated portions are disposed to face each other with the separator interposed therebetween, and the first and second uncoated portions are disposed not to overlap with each other.

3. The battery of claim 2, wherein a plurality of first electrodes are provided, of which two adjacent first uncoated portions, among a plurality of first uncoated portions, are welded to be combined with the first electrode tab inserted therebetween, and other adjacent first uncoated portions than the two first uncoated portions are welded to be combined.

4. The battery of claim 2 or 3, wherein a plurality of second electrodes are provided, of which two adjacent second uncoated portions, among a plurality of second uncoated portions, are welded to be combined with the second electrode tab inserted therebetween, and other adjacent second uncoated portions than the two second uncoated portions are welded to be combined.

5. The battery of claim 1 , wherein air cooling recesses are formed on an outer surface of the case.

6. A battery module comprising a plurality of secondary batteries of claim 1 , wherein a first electrode tab of one secondary battery is combined to be connected in series with a second electrode tab of another secondary battery.

7. The module of claim 6, wherein the plurality of secondary batteries are stacked such that their polarities are arranged alternately.

8. The module of claim 7, wherein the first and second electrode tabs are bent toward each other and welded.

9. A battery module comprising a plurality of secondary batteries of claim 1 , wherein a plurality of first electrode tabs are combined with each other and a plurality of second electrode tabs are combined with each other so as to be connected in parallel.

10. The module of claim 9, wherein the plurality of secondary batteries are stacked such that the plurality of first electrode tabs are all directed in a first direction and the plurality of second electrode tabs are all directed in a second direction.

11. The module of claim 10, wherein, as for the plurality of first and second electrode tabs, the homogenous tabs are bent in the same direction and welded.

12. A battery module comprising a plurality of secondary batteries of claim 1 , wherein at least one first electrode tab of a group of secondary batteries connected in parallel and at least one second electrode tab of a different group of secondary batteries connected in parallel are directly or indirectly combined so as to be connected in series.

13. The module of claim 12, wherein the plurality of secondary batteries are stacked such that their polarities are arranged alternately by groups.

14. A method for fabricating a secondary battery with a structure having electrode tabs drawn out in different directions, comprising: alternately stacking first and second electrodes with separators interposed therebetween such that a first uncoated portion without an active material of each first electrode and a second uncoated portion without an active material of each second electrode do not overlap with each other; inserting the first electrode tab penetrating a first side cover without a gap between two adjacent first uncoated portions among the plurality of first uncoated portions all stacked to face a first direction, and allowing two first uncoated portions positioned at the outermost portions to come in contact with a welding bar to simultaneously weld the plurality of first uncoated portions and the first electrode tab; inserting the second electrode tab penetrating a second side cover without a gap between two adjacent second uncoated portions among the plurality of second uncoated portions all stacked to face a second direction, and allowing two second uncoated portions positioned at the outermost portions to come in contact with a welding bar to simultaneously weld the plurality of second uncoated portions and the second electrode tab to complete an electrode assembly; and putting the electrode assembly in a case body, combining the first and second side covers with the case body, impregnating an electrolyte in the electrode assembly, and then sealing the same.

15. The method of claim 14, wherein the first and second side covers are injection-molded with a non-conductive material so as to be formed in a state that the first and second electrode tabs penetrate central portions of the respective side covers.