Battery pack

Abstract

Provided is a battery pack that eliminates a local load caused by bending of an electrode tab, and that realizes an ideal wiring pattern and an ideal mounting component by configuring a circuit board so as to have an optimum outer shape for usage thereof without restricting the size of the circuit board to the area of a terrace section. The present invention provides a battery pack including a secondary-battery pouch cell 1 and a circuit board 2 connected to the pouch cell 1, wherein: the pouch cell 1 includes a planar terrace section 6 in which positive and negative electrode tabs 3 are sandwiched by two insulating films 10 and pulled out to the outside; the circuit board 2 has an electronic component 13 for realizing a protection circuit of the pouch cell 1 mounted on a surface thereof, and has a first region 2A laminated on an upper surface of the terrace section 6 and a second region 2B arranged outside the terrace section 6; positive and negative metal plates 8 formed by welding the positive and negative electrode tabs 3 thereto are arranged on a lower surface of the second region 2B by being electrically connected to a wiring pattern 9; and the positive and negative electrode tabs 3 are pulled out from the terrace section 6 in a planar manner and distal-end sections thereof are welded to the positive and negative metal plates 8

Description

Battery pack

[0001] The present disclosure relates to a pouch cell battery pack, and more particularly to a battery pack in which a circuit board is disposed on a terrace portion of a pouch cell.

[0002] Pouch cells have been developed as thin secondary batteries. These pouch cells have two electrode tabs sandwiched between two insulating films and extended to the outside. Pouch cells with this structure have the advantage of being thinner than secondary batteries with metal exterior cans. Technology has been developed to manufacture thin battery packs using thin pouch cells (see Patent Document 1).

[0003] Japanese Patent No. 6743312 Japanese Patent Application Laid-Open No. 2005-183157

[0004] The thin battery pack described in Patent Document 1 has positive and negative electrode tabs sandwiched between terrace sections formed by stacking two insulating films and extending to the outside. The positive and negative electrode tabs extending from the terrace sections are electrically connected to a circuit board. The circuit board is mounted with electronic components of a protection circuit that controls the charging and discharging of the pouch cells, improving the safety of the battery pack. The terrace sections have side walls on both sides. The side walls are also formed by stacking two insulating films, and the circuit board is located in the area surrounded by the side edges and the terrace sections. In battery packs where the circuit board is located on the terrace sections, the electrode tabs are U-bent and the circuit board is located on the terrace sections. Because the U-bent electrode tabs are bent with a small curvature radius, the stress on the bent section is large, resulting in issues such as breakage of the electrode tabs. Furthermore, the restoring force of the bent electrode tabs can cause the circuit board to move away from the terrace sections and become misaligned. Furthermore, because the circuit board is located inside the terrace sections and side walls, battery packs with this structure are subject to size restrictions on the circuit board. Circuit boards cannot be made large, and the mounting area for electronic components is therefore limited. Therefore, in battery packs used for a variety of purposes, it is difficult to create an ideal wiring pattern on the circuit board and mount enough electronic components.

[0005] The battery pack of Patent Document 2 has a circuit board located outside the terrace portion, allowing the electrode tabs to be connected to the circuit board without bending them in a U-shape. In this battery pack, the electrode tabs extending from the terrace portion are connected to both sides of the circuit board without bending them in a U-shape, preventing localized stress on the bent portions of the electrode tabs. However, in this battery pack, the circuit board and the terrace portion are located on the same plane, and the circuit board is located outside the terrace portion, which creates a problem of the circuit board increasing the overall size of the battery pack. Since pouch cell battery packs are primarily used as power sources for portable devices, reducing the overall size to make them convenient for portability is an essential requirement, making miniaturization an extremely important issue. Furthermore, in this battery pack, the positive and negative electrode tabs are connected to both sides of the circuit board, which limits the mounting area of ​​electronic components mounted on the surface of the circuit board. Circuit boards with limited mounting area for electronic components due to electrode tabs require an even larger overall size to accommodate the necessary electronic components, which further increases the overall size of the battery pack.

[0006] The present disclosure has been developed with the objective of further resolving the above-mentioned problems, and one of the objectives of the present disclosure is to provide a pouch cell battery pack that eliminates the localized stress caused by bending of the electrode tabs, and in which the size of the circuit board is not restricted by the area of ​​the terrace portion, and the circuit board can be placed both inside and outside the terrace portion, thereby achieving an optimal external shape for the application, an ideal wiring pattern, and ideal mounting components.

[0007] A battery pack according to one embodiment of the present disclosure includes a pouch cell of a secondary battery and a circuit board connected to the pouch cell, and has all of the following configurations (a) to (e): (a) The pouch cell includes a planar terrace portion formed by sandwiching positive and negative electrode tabs between two insulating films and extending to the outside; (b) The circuit board has electronic components mounted on its surface that implement a protection circuit for the pouch cell; (c) The circuit board includes a first region laminated on the upper surface of the terrace portion and a second region disposed outside the terrace portion; (d) The circuit board includes positive and negative metal plates, to which the positive and negative electrode tabs are welded, disposed on the lower surface of the second region and electrically connected to the wiring patterns; and (e) The positive and negative electrode tabs are extended from the terrace portion in a planar manner, with their tips welded to the positive and negative metal plates.

[0008] The battery pack of the present invention has the advantage of eliminating the localized stress caused by bending the electrode tabs, and furthermore, the size of the circuit board is not restricted by the area of ​​the terrace portion, and the circuit board can be placed both inside and outside the terrace portion, allowing for an optimal external shape for the application, an ideal wiring pattern, and ideal mounted components.

[0009] Fig. 2 is an enlarged cross-sectional view of a main portion of a battery pack according to an embodiment of the present disclosure. Fig. 3 is a plan view of a battery assembly consisting of a circuit board and pouch cells of the battery pack shown in Fig. 1. Fig. 4 is a bottom view of a battery assembly consisting of a circuit board and pouch cells of the battery pack shown in Fig. 1. Fig. 5 is a perspective view of the battery assembly shown in Fig. 1, in which a circuit board is arranged on a terrace portion, as viewed from below. Fig. 6 is a perspective view of the battery assembly shown in Fig. 1, in which a circuit board is arranged on a terrace portion, as viewed from above. Fig. 7 is an enlarged cross-sectional view of an area where an electrode tab is laser welded to a metal plate of the circuit board of the battery pack of Fig. 1.

[0010] The present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms incorporating these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts with the same reference numerals appearing in multiple drawings indicate the same or equivalent parts or components. Furthermore, the embodiments described below are illustrative examples of the technical concept of the present invention and do not limit the scope of the present invention. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the content described in one embodiment or example may also be applicable to other embodiments or examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0011] The embodiments of the present disclosure may be specified by the following configurations and features. A battery pack according to one embodiment of the present disclosure includes a pouch cell of a secondary battery and a circuit board connected to the pouch cell, and includes all of the following configurations (a) to (e): (a) The pouch cell includes a planar terrace portion formed by sandwiching positive and negative electrode tabs between two insulating films and extending to the outside. (b) The circuit board has electronic components mounted on its surface that implement a protection circuit for the pouch cell. (c) The circuit board includes a first region laminated on the upper surface of the terrace portion and a second region disposed outside the terrace portion. (d) The circuit board includes positive and negative metal plates, to which the positive and negative electrode tabs are welded, disposed on the lower surface of the second region and electrically connected to the wiring pattern. (e) The positive and negative electrode tabs are extended from the terrace portion in a planar manner, and their tips are welded to the positive and negative metal plates.

[0012] In the above-described battery pack, the positive and negative electrode tabs extending from the pouch cell are arranged in a planar manner and welded to the metal plate of the circuit board, eliminating the need to bend the electrode tabs at a small radius of curvature to electrically connect them to the circuit board arranged on the surface of the terrace portion of the pouch cell, thereby eliminating the localized stress caused by bending the electrode tabs. Furthermore, the above-described battery pack is configured with a first region in which the circuit board is stacked on the terrace portion and a second region protruding from the terrace portion, and a metal plate is provided on the underside of the second region, to which the tips of the electrode tabs extending in a planar manner from the terrace portion are welded. This means that the size of the circuit board is not limited by the area of ​​the terrace portion. Circuit boards that are not limited in size have the advantage of being able to have an optimal outer shape for the application, an ideal wiring pattern, and mount components that realize ideal circuit configurations, such as electronic components that realize protection circuits.

[0013] In a battery pack according to another embodiment of the present disclosure, the circuit board can have the electronic components of the protection circuit mounted on the upper surface thereof. The battery pack has a feature that the area surrounded by the terrace portion and both side walls of the pouch cell can be used as a space for arranging the electronic components of the protection circuit, and the circuit board can be arranged on the terrace portion.

[0014] In a battery pack according to another embodiment of the present disclosure, electronic components mounted on the upper surface of a circuit board can be disposed without protruding from the upper surface level of the pouch cell. The above-described battery pack has a feature that pouch cells having circuit boards disposed on terrace portions can be housed in the outer case by efficiently utilizing the internal space of the outer case. This is because a battery assembly of pouch cells having circuit boards with electronic components mounted on their upper surfaces disposed on terrace portions can be housed in the outer case without increasing the internal width of the outer case housing the pouch cells.

[0015] In another embodiment of the battery pack of the present disclosure, one electrode tab of the pouch cell is made of aluminum, and the metal plate to which the aluminum electrode tab is welded can be an aluminum plate with a nickel-plated upper surface. This battery pack has the advantage that the aluminum electrode tab can be reliably and stably electrically connected to the circuit board. This is because the aluminum electrode tab is laminated on the metal plate of the aluminum plate with a nickel-plated upper surface, and a laser beam is irradiated onto the electrode tab, allowing for reliable laser welding between the electrode tab and the metal plate.

[0016] In another embodiment of the battery pack of the present disclosure, one electrode tab of the pouch cell is made of aluminum and the other electrode tab is made of nickel, and the metal plate formed by welding both the aluminum electrode tab and the nickel electrode tab can be an aluminum plate with a nickel-plated upper surface. This battery pack has the advantage that both the aluminum electrode tab and the nickel electrode tab can be reliably and stably electrically connected to the circuit board. This is because the aluminum electrode tab and the nickel electrode tab can be laminated on a metal plate whose upper surface is nickel-plated, and a laser beam can be irradiated onto the electrode tab to reliably laser-weld the electrode tab and the metal plate.

[0017] In a battery pack according to another embodiment of the present disclosure, the area of ​​the first region of the circuit board can be 80% or more of the terrace portion. The above-described battery pack has the advantage that the circuit board can be optimized in area and shape depending on the application, an ideal wiring pattern can be realized, and electronic components of a protection circuit that realizes an ideal circuit configuration can be mounted.

[0018] A battery pack according to another embodiment of the present disclosure may include an outer case that houses a battery assembly including a circuit board disposed on a terrace portion and an electrode tab of a pouch cell electrically connected to the circuit board (Embodiment 1).

[0019] The battery pack 100 shown in FIGS. 1 to 5 includes a pouch cell 1 and a circuit board 2 connected to an electrode tab 3 of the pouch cell 1 .

[0020] As shown in FIG. 1 , the pouch cell 1 has a battery element 4, in which positive and negative electrodes are laminated between two insulating films 10. In the pouch cell 1, both the top and bottom surfaces of the battery element 4 are covered with two insulating films 10. However, the two insulating films 10 covering both surfaces can be used by folding one film back at one edge of the battery element 4 to form two films covering both surfaces. The two insulating films 10 are joined and welded to a laminated portion 5 laminated on the outside of the battery element 4. The insulating film 10 is a plastic film that tightly contacts the laminated portion 5 laminated on the outside of the battery element 4 to keep the interior airtight. Note that the insulating film 10 does not need to be a single layer and may be multi-layered. The battery element 4 of the pouch cell 1 is preferably a lithium polymer battery. However, the present disclosure does not specify that the battery element 4 of the pouch cell 1 is a lithium polymer battery, and any secondary battery can be used in which an insulating film 10 can be laminated on both sides of the battery element 4 and the insulating film 10 can be joined on the outside of the battery element 4.

[0021] The pouch cell 1 has a rectangular outer shape, and an insulating film 10 is laminated along the outer edge of the battery element 4 to form a laminated portion 5. The pouch cell 1 has two insulating films 10 hermetically joined at the laminated portion 5 by adhesive bonding, welding, or other methods. The pouch cell 1 is preferably used by folding one insulating film 10 along one edge of the battery element 4 to cover both sides of the battery element 4. In a pouch cell 1 with this structure, the insulating film 10 is folded along one edge of the battery element 4, so that one side of the rectangle does not have a laminated portion 5, but three sides have laminated portions 5. However, the pouch cell 1 can also have a structure in which laminated portions 5 are provided around the four outer edges of the rectangle. This pouch cell 1 is manufactured by overlapping two separated insulating films 10 on both sides of the battery element 4 and joining them at the laminated portions 5 on the four sides around the battery element 4. Furthermore, even if the battery element 4 of the pouch cell 1 is rectangular, the outer shape may be different from a rectangle depending on how the electrode tab 3 is removed or how the laminated portion 5 is folded. Therefore, the outer shape of the pouch cell 1 may be a shape other than a rectangle, such as a polygon, an oval, a polygon with partially curved portions, a regular shape, or an irregular shape.

[0022] In the pouch cell 1 of FIG. 1, the insulating film 10 laminated on the underside of the battery element 4 is flat or nearly flat, and the insulating film 10 laminated on the upper surface of the battery element 4 is folded downward along the periphery of the battery element 4 and laminated on the insulating film 10 on the lower surface to form a terrace portion 6.

[0023] The pouch cell 1 in FIGS. 2 and 3 has a terrace portion 6 on one side of the periphery. The terrace portion 6 is a laminated portion 5 of the insulating film 10 that protrudes outward from the battery element 4. The terrace portion 6 is arranged in a plane parallel to both sides of the battery element 4. In the pouch cell 1 shown in the cross-sectional view of FIG. 1, the terrace portion 6 is arranged on the bottom side of the battery element 4. Furthermore, the pouch cell 1 shown in the figure has side walls 7 connected to both sides of the terrace portion 6. As shown in the perspective views of FIGS. 4 and 5, the side walls 7 are formed by bending the laminated portions 5 protruding on both sides of the battery element 4 at 90 degrees so as to fit along the side surfaces of the battery element 4. In a terrace portion 6 of this shape, the side walls 7 on both sides function as reinforcing ribs, thereby increasing the bending strength of the terrace portion 6.

[0024] In the pouch cell 1, positive and negative electrode tabs 3 are insulated and sandwiched between a terrace portion 6 that is part of the laminated portion 5. As shown in Figure 4, the electrode tabs 3 are airtightly sandwiched between two insulating films 10 of the terrace portion 6 and extended to the outside of the terrace portion 6. The positive electrode tab 3 is made of aluminum, and the negative electrode tab 3 is made of nickel. The positive and negative electrode tabs 3 are directly laser-welded to a metal plate 8 fixed to the surface of the circuit board 2, for electrical connection.

[0025] The circuit board 2 is mounted with electronic components 13 that implement a protection circuit for the pouch cell 1. The circuit board 2 in FIGS. 1 and 2 comprises a first region 2A laminated on the upper surface of the terrace portion 6 and a second region 2B protruding outward from the terrace portion 6 and disposed outside the terrace portion 6. In the circuit board 2 disposed on the upper surface of the terrace portion 6, the area of ​​the first region 2A can be 80% or more of the terrace portion. The area of ​​the first region 2A can be almost the entire terrace portion 6 excluding the electrode tabs 3. The first region 2A can be disposed up to the outer periphery of the terrace portion 6, thereby reducing the area constraints of the circuit board 2 and achieving an optimal area and shape for the intended use of the circuit board 2, allowing for an ideal wiring pattern and sufficient mounting of electronic components 13.

[0026] The circuit board 2 has a metal plate 8 fixed to the underside of the second region 2B. The metal plate 8 is electrically connected to the wiring pattern 9 of the circuit board 2, and the electrode tabs 3 laser-welded to the surface are electrically connected to the wiring pattern 9, thereby connecting to electronic components 13 that implement a protection circuit for the pouch cell 1. The electrode tabs 3 are connected to the wiring pattern 9 on the upper surface via the laser-welded metal plate 8. The electrode tabs 3 are extended in a planar shape from the terrace portion 6, and their tips are laser-welded to the metal plate 8. The enlarged cross-sectional view of FIG. 6 illustrates an enlarged view in the thickness direction of the region of the pouch cell 1 where the electrode tabs 3 are welded to the metal plate 8. As shown in FIG. 6, the electrode tabs 3 extended in a planar shape from the terrace portion 6 and connected to the metal plate 8 are slightly deviated from a planar shape due to the difference in thickness between the insulating film 10 and the metal plate 8. However, both the insulating film 10 and the metal plate 8 are thin, and the difference in thickness is extremely small, so that the thicknesses of the two are substantially equal. Therefore, the electrode tab 3 extends substantially in a plane and can be laser welded to the metal plate 8 .

[0027] The circuit board 2 has a copper foil wiring pattern 9 on the surface of a printed wiring board 11, such as an epoxy board or a phenol board. Furthermore, a metal plate 8 is fixed to the second region 2B of the circuit board 2, which is the region where the tips of the electrode tabs 3 are connected. The circuit board 2 in FIG. 6 has the electrode tabs 3 connected to its underside, so the metal plate 8 is fixed to the underside of the circuit board 2. The metal plate 8 can be electrically connected to the wiring pattern 9 by a method such as soldering. Furthermore, the circuit board 2 can be connected to a connector for connecting to an electrical device via lead wires. Furthermore, a structure in which positive and negative output terminals are fixed to the circuit board 2 and the output terminals are exposed on the surface of the exterior case 14 for connection to other electrical devices can also be used.

[0028] The metal plate 8 to which the electrode tab 3 is laser-welded is electrically connected and fixed to the copper foil of the wiring pattern 9 provided on the surface of the circuit board 2. The metal plate 8 is thicker than the metal foil of the electrode tab 3. For example, the film thickness of the electrode tab 3 can be 0.01 mm or more and 0.06 mm or less, and the thickness of the metal plate 8 can be, for example, 13 times or more, preferably 15 times or more, that of the electrode tab 3, for example, approximately 1 mm. A metal plate 8 thicker than the electrode tab 3 can stably electrically connect the electrode tab 3 to the wiring pattern 9 of the circuit board 2. For example, an aluminum plate with a nickel-plated surface can be used as the metal plate 8 to stably laser-weld both the aluminum electrode tab 3 and the nickel electrode tab 3 and to reduce electrical resistance. However, the metal plate 8 can also be a metal plate 8 made of other metals such as iron with a nickel-plated surface, or the entire metal plate can be a nickel plate. The nickel-plated aluminum metal plate 8 has the advantage of being able to stably laser-weld the aluminum foil used in the positive electrode tab 3 of the pouch cell 1.

[0029] The enlarged cross-sectional view of Figure 6 shows an enlarged cross-sectional view of a circuit board 2 in which the electrode tabs 3 can be efficiently laser-welded to the metal plate 8. The circuit board 2 in this figure has a reflective metal foil 12 below the metal plate 8 that efficiently reflects the laser beam. The circuit board 2 in this figure has the metal plate 8 disposed on its upper surface, and the reflective metal foil 12 disposed on its lower surface in a position facing the metal plate 8. The reflective metal foil 12 is disposed in a position facing the metal plate 8, and reflects the laser beam that has penetrated the metal plate 8. The reflective metal foil 12 can be realized by the copper foil of the wiring pattern 9. The reflective metal foil 12 made of copper foil can be easily provided as part of the wiring pattern 9 of the circuit board 2.

[0030] The reflective metal foil 12 adheres its laser beam reflecting surface to the circuit board 2, preventing oxidation of the reflecting surface. The reflective metal foil 12, which does not oxidize its reflecting surface, efficiently reflects the laser beam over a long period of time without experiencing a decrease in laser beam reflectivity due to an oxide film. The reflective metal foil 12, which efficiently reflects the laser beam, prevents itself from being melted by the irradiated laser beam, thereby preventing the laser beam from penetrating the circuit board 2. The method of laser welding the electrode tab 3 to the metal plate 8 uses a laser beam that can reflect the laser beam off the reflective metal foil 12 and avoid the drawback of the laser beam penetrating the circuit board 2. A YAG laser, for example, is used for laser welding the electrode tab 3. The reflective metal foil 12 made of copper foil, which can be provided as part of the wiring pattern 9, has a high reflectivity of approximately 90% for a YAG laser. Copper absorbs only approximately 10% of the laser beam energy, which is approximately one-third the laser beam energy absorbed by nickel. The circuit board 2 having the reflective metal foil 12 made of copper foil has the reflective metal foil 12 formed on a part of the copper foil of the wiring pattern 9, and effectively utilizes the unique physical property of the copper foil provided as the wiring pattern 9 on the circuit board 2, that is, the unique physical property of the copper foil that does not melt with a laser beam, thereby preventing harmful effects caused by the laser beam penetrating the circuit board 2.

[0031] The circuit board 2 is mounted with electronic components 13 that implement a protection circuit for the pouch cell 1. In Fig. 1, the electronic components 13 of the protection circuit are mounted on the upper surface of the circuit board 2. The electronic components 13 protrude and are fixed to the upper surface of the circuit board 2, which has electrode tabs 3 connected to its lower surface. The protection circuit may be, for example, a circuit that controls charge / discharge current to protect the pouch cell 1 from overcharging or overdischarging, a circuit that detects an overcurrent and cuts off the current, or a circuit that cuts off the current when the pouch cell 1 reaches an abnormally high temperature.

[0032] The present disclosure eliminates the localized stress caused by bending the electrode tabs, and further allows the circuit board to be positioned both inside and outside the terrace portion without restricting the size of the circuit board to the area of ​​the terrace portion, making it possible to effectively use it as a pouch cell battery pack that can achieve an optimal external shape for the application, an ideal wiring pattern, and ideal mounting components.

[0033] DESCRIPTION OF SYMBOLS 100... Battery pack 1... Pouch cell 2... Circuit board 2A... First region 2B... Second region 3... Electrode tab 4... Battery element 5... Laminated portion 6... Terrace portion 7... Side wall 8... Metal plate 9... Wiring pattern 10... Insulating film 11... Printed wiring board 12... Reflective metal foil 13... Electronic component 14... Outer case

Claims

1. A battery pack comprising a pouch cell of a secondary battery and a circuit board connected to the pouch cell, and comprising all of the following configurations (a) to (e): (a) The pouch cell is configured by covering the upper and lower surfaces of a battery element with insulating films, and has planar terrace portions formed by positive and negative electrode tabs sandwiched between the insulating films on the upper and lower surfaces of the battery element and extending to the outside. (b) The circuit board has electronic components mounted on its surface that implement a protection circuit for the pouch cell. (c) The circuit board has a first region laminated on the upper surface of the terrace portion and a second region disposed outside the terrace portion. (d) The circuit board has positive and negative metal plates, to which the positive and negative electrode tabs are welded, disposed on the lower surface of the second region and electrically connected to wiring patterns. (e) The positive and negative electrode tabs are extended in a planar manner from the terrace portion, and their tips are welded to the positive and negative metal plates.

2. A battery pack according to claim 1, wherein the circuit board has the electronic components of the protection circuit mounted on its upper surface.

3. A battery pack according to claim 2, wherein the electronic components mounted on the upper surface of the circuit board are arranged so as not to protrude above the upper surface level of the pouch cell.

4. A battery pack as described in claim 1, wherein the electrode tab on one side of the pouch cell is made of aluminum, and the metal plate to which the aluminum electrode tab is welded is an aluminum plate with a nickel-plated upper surface.

5. A battery pack as described in claim 1, wherein the electrode tab on one of the pouch cells is made of aluminum and the electrode tab on the other is made of nickel, and the metal plate to which both the aluminum electrode tab and the nickel electrode tab are welded is an aluminum plate with a nickel-plated upper surface.

6. A battery pack according to any one of claims 1 to 5, wherein the area of ​​the first region of the circuit board is 80% or more of the area of ​​the terrace portion.

7. A battery pack according to claim 1, comprising an exterior case in which a battery assembly is placed inside, the battery assembly comprising the circuit board disposed on the terrace portion and the electrode tabs of the pouch cell electrically connected to the circuit board.

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