Battery pack

A battery pack is a battery pack that is configured by arranging plural chargeable-dischargeable single cells in a specified direction. Each of the plural single cells includes: an electrode body including a positive electrode and a negative electrode; and a box-shaped battery case accommodating the electrode body and an electrolyte. The two adjacent single cells in the battery pack are provided with gas discharge valves in mutually opposing surfaces of the battery cases, each of the gas discharge valves discharging gas that is produced in the battery case. In the battery cases provided in the two adjacent single cells, the gas discharge valves that are provided in the mutually opposing surfaces are disposed at positions that do not overlap each other when seen in an arrangement direction of the single cells.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-251810 filed on Dec. 26, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a battery pack.

2. Description of Related Art

One of power storage elements such as a lithium-ion secondary battery, a nickel-metal hydride battery, another type of a secondary battery, and a capacitor, each of which is lightweight and has high energy density, is selected as a single cell, and the plural single cells are connected in series to form a battery pack. Being a power supply with high output, such a battery pack is preferably used as an in-vehicle power supply or a power supply for a personal computer and a portable terminal. One example of the battery pack is disclosed in Japanese Patent No. 05966457 (JP 05966457 B). The battery pack is configured by arranging plural units of square-shaped single cells and connecting positive-electrode terminals and negative-electrode terminals, each pair of which is provided in each of the single cells, in series. In such a battery pack, the plural single cells are reversely disposed such that the positive-electrode terminals and the negative-electrode terminals are alternately disposed. A gas discharge valve (a safety valve) is provided on an upper surface of a battery case in each of the single cells, so as to discharge gas that is produced in the battery during overcharging.

SUMMARY

In order to improve the energy density of each of the single cells, as shown inFIG. 11, the inventors have considered to increase dimensions of each single cell1in a lateral direction X and a vertical direction Y and reduce a dimension thereof in a thickness direction (an arrangement direction of each of the single cells at a time when the battery pack is formed) Z. However, when the single cell1is made low profile by reducing the dimension of the single cell1in the thickness direction Z, it is difficult to dispose the gas discharge valve on a lateral surface2of the battery case in dimension wise. In this case, there is no other way than to form the gas discharge valve on a wide surface (a surface of each of the battery cases on which the battery cases oppose each other at the time when the battery pack is formed)3of the battery case, and a formation position of the gas discharge valve is required to be a position at which the gas discharge valve has no negative effect on the gas discharge valve of the adjacent single cell and at which the gas discharge valve can efficiently discharge the gas produced in the battery case in a state where the battery pack is formed.

The disclosure provides a battery pack that is configured by arranging plural chargeable-dischargeable single cells in a specified direction and that can efficiently discharge gas from a gas discharge valve even when the gas discharge valve is formed on a wide surface of a battery case (a surface of each of the battery cases on which the battery cases oppose each other at a time when the battery pack is formed).

A battery pack provided by the disclosure is a battery pack that is configured by arranging plural chargeable-dischargeable single cells in a specified direction. Each of the plural single cells includes: an electrode body including a positive electrode and a negative electrode; and a box-shaped battery case accommodating the electrode body and an electrolyte. In the battery pack disclosed herein, the two adjacent single cells of the battery pack are provided with gas discharge valves in mutually opposing surfaces of the battery cases, each of the gas discharge valves discharging gas that is produced in the battery case. In the battery cases provided in the two adjacent single cells, the gas discharge valves that are provided in the mutually opposing surfaces are characterized to be disposed at positions that do not overlap each other when seen in an arrangement direction of the single cells.

In this specification, the “single cell” is a term that indicates each of power storage elements that are mutually connected in series to constitute the battery pack, and includes batteries and capacitors of various compositions unless otherwise particularly limited. A “secondary battery” refers to a general battery that can repeatedly be charged, and includes storage batteries such as a lithium-ion secondary battery and a nickel-metal hydride battery. The power storage element that constitutes the lithium-ion secondary battery is a typical example that is included in the “single cell” referred herein. A lithium-ion secondary battery module that is configured by including a plurality of such single cells is a typical example of the “battery pack” disclosed herein.

In the battery cases provided in the above-described adjacent single cells, the gas discharge valves, which are provided in the mutually opposing surfaces, each discharge the gas produced in the battery case when a pressure inside the battery case reaches a specified value, for example. In the case where such gas discharge valves are formed at positions that overlap each other when seen in the arrangement direction of the single cells, the gas that is discharged from the gas discharge valve of one of the adjacent single cells blown onto the gas discharge valve of the other of the adjacent single cells. As a result, the gas discharge valve of the other of the adjacent single cells possibly suffers from a negative effect. In addition, in the case where both of the gas discharge valves are actuated simultaneously, discharge of the gas from both of the gas discharge valves is mutually inhibited. As a result, there is a possibility that the gas produced in each of the battery cases cannot efficiently be discharged. Thus, such a case is not preferred. In the battery pack of the disclosure with the above configuration, the gas discharge valves, which are provided in the mutually opposing surfaces of the battery cases, are disposed at the positions that do not overlap each other when seen in the arrangement direction. Thus, the gas that is discharged from the gas discharge valve of one of the adjacent single cells is less likely to be blown onto the gas discharge valve of the other of the adjacent single cells. In addition, even in the case where both of the gas discharge valves are actuated simultaneously, the discharge of the gas is less likely to be mutually inhibited. Therefore, it is possible to provide the battery pack with this configuration that is less likely to cause inconvenience as described above and is high in reliability.

In the battery pack, a direction that is a perpendicular direction to a lateral direction and a vertical direction, each of which follows an outer shape of the single cell, may be the arrangement direction in which the single cells are arranged in the battery pack, and, in the lateral direction, the gas discharge valve may be disposed at a position that is offset from a center line of the battery case.

In the battery pack, in the lateral direction, length from a center of the gas discharge valve to the center line may be greater than length from the center of the gas discharge valve to an outer edge of the gas discharge valve.

In the battery pack, the length from the center of the gas discharge valve to the center line may be 1.5 times or more than the length from the center of the gas discharge valve to the outer edge of the gas discharge valve.

DETAILED DESCRIPTION OF EMBODIMENTS

A description will hereinafter be made on an embodiment of the disclosure with reference to the drawings. Note that matters other than those specifically mentioned in this specification and matters required for implementation of the disclosure (for example, a general configuration and a general manufacturing process of an electrode body, neither of which characterizes the disclosure) can be acknowledged as design matters of a person skilled in the art that are based on the related art in this field. The disclosure can be implemented on the basis of contents disclosed in this specification and common general technical knowledge in this field. In addition, in the following drawings, members and portions that exert the same effects are denoted by the same reference numerals. Furthermore, dimensional relationships (length, width, thickness, and the like) in each of the drawings do not necessarily reflect actual dimensional relationships.

A chargeable-dischargeable secondary battery is preferably used as a single cell for a battery pack according to the disclosure, and the battery pack is preferably formed by connecting plural units of such single cells in series. A configuration of each of the single cells is not particularly limited. Each of a nickel-metal hydride battery, an electric double-layered capacitor, and the like is exemplified as the single cell that has a preferred configuration for the implementation of the disclosure. A lithium-ion secondary battery has a particularly preferred configuration of the single cell for the implementation of the disclosure. Because the lithium-ion secondary battery is a secondary battery with high energy density that can realize high output, a high-performance battery pack, in particular, a high-performance in-vehicle battery pack (battery module) can be constructed thereof. Although there is no intention of particularly limiting a battery configuration to that of the lithium-ion secondary battery, the disclosure will hereinafter be described in detail by using the lithium-ion secondary battery as an example of the battery configuration.

The battery pack is configured by arranging the plural chargeable-dischargeable single cells in a specified direction. Similar to the single cell that is equipped in the battery pack of the related art, each of the plural single cells typically includes: the electrode body that is equipped with specified battery constituent materials (an active material for each of positive/negative electrodes, a current collector for each of the positive/negative electrodes, a separator, an electrolyte, and the like); and a box-shaped battery case that accommodates the electrode body.

FIG. 1is a perspective view of a single cell (a lithium-ion secondary battery)100that constitutes the battery pack according to this embodiment,FIG. 2is a plan view thereof,FIG. 3is a side view thereof,FIG. 4is another side view thereof,FIG. 5is a cross-sectional schematic view that is taken along V-V inFIG. 2, andFIG. 6is a cross-sectional schematic view that is taken along VI-VI inFIG. 2.FIG. 7is a view that illustrates a positive electrode20, a negative electrode30, and a separator40that constitute an electrode body10in each of the single cells100. In the following description, along an outer shape of the single cell100, an X-direction, a Y-direction, and a Z-direction that is a perpendicular direction to the X-direction and the Y-direction are respectively referred to as a lateral direction, a vertical direction, and a thickness direction. Here, the thickness direction Z corresponds to a direction in which the single cells100are arranged in the battery pack (an arrangement direction). Note that these are merely directions defined for the purpose of convenience and thus do not limit an installation aspect of the lithium-ion secondary battery100in any respects.

As shown inFIG. 1toFIG. 7, the lithium-ion secondary battery100includes a battery case50, the electrode body10, a gas discharge valve60, an liquid injection hole70, a positive electrode terminal80, a negative electrode terminal82, and the electrolyte, which is not shown.

The battery case50is a container that accommodates the electrode body10and the electrolyte. In this embodiment, the battery case50has a box-shaped outer shape (an angled rectangular parallelepiped shape). The battery case50includes an almost flat case body52and a sealing plate54. The case body52is formed in a concave shape that can accommodate the electrode body10. In the case body52, of surfaces that constitute the case body52, the surface with the largest area (a wide surface) is opened. In this embodiment, one of the surfaces of the case body52in the thickness direction Z is opened. The case body52also has a flange portion52athat is attached to a peripheral edge of an opening portion52b. The sealing plate54is a flat plate-shaped member that closes the opening portion52bof the case body52. The sealing plate54is attached to the case body52in a manner to cover the opening portion52bof the case body52. The case body52and the sealing plate54are disposed to oppose each other in the thickness direction Z with the electrode body10being held therebetween. The flange portion52awhich is provided in the case body52and the sealing plate54are joined to each other by seal welding. In this way, the battery case50is tightly sealed. A material of the battery case50is a metallic material such as aluminum or steel. The battery case50can be set to have 0.3 mm or greater in thickness (wall thickness), for example, and can typically be set to have 0.3 mm to 1 mm in thickness.

The concave case body52has: a flat surface56on which the electrode body10is disposed; and a lateral wall surface57that is raised from the flat surface56so as to surround the electrode body10disposed on the flat surface56. When seen in the thickness direction Z, the flat surface56has a rectangular shape that is defined by a first side58a, a second side58bthat opposes the first side58a, a third side58cthat is orthogonal to the first side58a, and a fourth side58dthat is orthogonal to the first side58aand opposes the third side58c. The lateral wall surface57is formed along the four sides (the first side58a, the second side58b, the third side58c, and the fourth side58d) of the flat surface56so as to surround the electrode body10, which is disposed on the flat surface56.

The flat surface56is also formed in a step shape (an uneven shape) that includes: a wide portion56a, a distance of which from the sealing plate54is long, and a narrow portion56b, a distance of which from the sealing plate54is shorter than that of the wide portion56a. The wide portion56aof the flat surface56is a portion in which the electrode body10is disposed. The wide portion56aof the flat surface56opposes the electrode body10, which is accommodated in the battery case50. A distance L2(FIG. 6) between the wide portion56aof the flat surface56and the sealing plate54is substantially the same as thickness of the electrode body10in the thickness direction Z. The distance L2between the wide portion56aof the flat surface56and the sealing plate54can be set to 3 mm to 20 mm, for example, and can typically be set to 5 mm to 15 mm. The narrow portion56bof the flat surface56is connected to the wide portion56avia a step55(FIG. 6). The narrow portion56bof the flat surface56is a portion in which the gas discharge valve60is formed. The narrow portion56bof the flat surface56does not oppose the electrode body10, which is accommodated in the battery case50. In this embodiment, the narrow portion56bof the flat surface56is formed along one end side of the flat surface56(the first side58aherein) in the vertical direction Y. When compared to the wide portion56a, the narrow portion56bof the flat surface56is formed to be projected to the sealing plate54side. A distance L1(FIG. 6) between the narrow portion56bof the flat surface56and the sealing plate54is shorter than the distance L2between the wide portion56aand the sealing plate54(L1<L2). The distance L1between the narrow portion56band the sealing plate54is approximately ⅘ or shorter of the distance L2between the wide portion56aand the sealing plate54(that is, L1/L2≤0.8), and is preferably 3/5 or shorter thereof (that is, L1/L2≤0.6). Although a lower limit of L1/L2is not particularly limited, for example, L1/L2≥0.3 can be realized, and L1/L2≥0.5 can typically be realized.

The gas discharge valve60is configured to discharge gas that is produced in the battery case50when a pressure inside the battery case50reaches a specified value. As shown inFIG. 2andFIG. 6, the gas discharge valve60is disposed in the narrow portion56bof the flat surface56of the case body52. In addition, the gas discharge valve60is disposed at a position that is offset from a center line C of the battery case50(that is, an intermediate line of the flat surface56between the third side58cand the fourth side58d) to the third side58cside in the lateral direction X. In this embodiment, in the lateral direction X, length D from a center A of the gas discharge valve60to the above center line C is greater than length d from the center A of the gas discharge valve60to an outer edge B of the gas discharge valve60(that is, D>d). For example, the length D from the center A of the gas discharge valve60to the center line C is preferably 1.5 times or more than the length d from the center A of the gas discharge valve60to the outer edge B of the gas discharge valve60(that is, D/d≥1.5), and is further preferably twice or more than the length d from the center A of the gas discharge valve60to the outer edge B of the gas discharge valve60(that is, D/d≥2). Although an upper limit of D/d is not particularly limited, for example, the upper limit of D/d can be set to satisfy D/d≤4 (typically D/d≤3). The length d from the center A of the gas discharge valve60to the outer edge B of the gas discharge valve60can be 3 mm to 15 mm, for example, and can typically be 5 mm to 10 mm.

The configuration of the gas discharge valve60itself is not particularly limited as long as the gas discharge valve60can discharge the gas, which is produced in the battery case50, when the pressure inside the battery case50reaches the specified value. For example, as shown inFIG. 6, the gas discharge valve60can have such a structure that a thin portion62is provided in a portion (the narrow portion56bof the flat surface56herein) of the battery case50. A notched groove64may be formed in the thin portion62. In this case, when the pressure inside the battery case50reaches the specified value, the thin portion62is fractured. In this way, the gas, which is produced in the battery, can be discharged to the outside of the battery through the gas discharge valve60. Alternatively, the gas discharge valve60may include a valve body that is fractured at a time when the pressure inside the battery case50reaches the specified value. In this case, when the pressure inside the battery case50reaches the specified value, the valve body is fractured. In this way, the gas, which is produced in the battery, can be discharged to the outside of the battery through the gas discharge valve60.

As shown inFIG. 1toFIG. 6, similar to the above-described gas discharge valve60, the positive electrode terminal80and the negative electrode terminal82are disposed in the narrow portion56bof the flat surface56of the case body52. The positive electrode terminal80is electrically connected to the positive electrode20of the electrode body10. The negative electrode terminal82is electrically connected to the negative electrode30of the electrode body10. In the lateral direction X, the positive electrode terminal80and the negative electrode terminal82are disposed line-symmetrically about the center line C of the battery case50. The positive electrode terminal80is disposed on the third side58cside from the center line C. The negative electrode terminal82is disposed on the fourth side58dside from the center line C. The liquid injection hole70is also provided in the narrow portion56bof the flat surface56of the case body52. In the narrow portion56bof the flat surface56, the liquid injection hole70is disposed at a position that is offset to the fourth side58dside from the above center line C. The liquid injection hole70is used to inject the liquid electrolyte (an electrolytic solution) therefrom. A cap is attached to the liquid injection hole70, and the liquid injection hole70is sealed in an airtight manner.

The electrode body10and the electrolyte are accommodated in the battery case50. As shown inFIG. 7, the electrode body10is the electrode body of a laminated type (a laminated electrode body) herein. The electrode body10includes plural rectangular positive electrode sheets20and plural rectangular negative electrode sheets30. The positive electrode sheets20and the negative electrode sheets30are laminated in insulated states via the separator40. A lamination direction of the electrode body10is the thickness direction Z herein.

The positive electrode sheet20includes a positive-electrode current collector22and a positive-electrode active material layer24that is formed on each surface of the positive-electrode current collector22. For example, metal foil that is suited for the positive electrode can preferably be used as the positive-electrode current collector22. In this embodiment, aluminum foil is used as the positive-electrode current collector22. In the illustrated example, the positive-electrode active material layers24are respectively supported on both of the surfaces of the positive-electrode current collector22. In addition, in the lateral direction X and the vertical direction Y, the positive-electrode active material layer24is formed to have the same width as total width of the positive-electrode current collector22.

The positive-electrode active material layer24contains a positive-electrode active material, a conductive material, and a binder. One type or two or more types of materials that are used as the lithium-ion secondary battery in the related art can be used for the positive-electrode active material without any particular limitation. As one example, a lithium-transition metal composite oxide with a layer structure that can be expressed by a general expression LiMeO2(Me contains at least one type of transition metal elements such as Ni, Co, and Mn) is used, and examples of such a lithium-transition metal composite oxide are LiNi1/3Co1/3Mn1/3O2(a lithium-nickel-cobalt-manganese composite oxide), LiNiO2(a lithium-nickel composite oxide), and LiCoO2(a lithium-cobalt composite oxide). In addition to the positive-electrode active material described above, the positive-electrode active material layer24can contain the conductive material such as acetylene black (AB) and the binder such as polyvinylidene fluoride (PVDF) or styrene-butadiene rubber (SBR).

The positive electrode sheet20has a projected portion26that is not formed with the positive-electrode active material layer24and is projected outward from a portion of the positive electrode sheet20that is formed with the positive-electrode active material layer24. Because the positive-electrode active material layer24is not formed in this projected portion26, the positive-electrode current collector22is exposed in the projected portion26. A positive-electrode current collection tab26is formed by this projected portion26. The positive-electrode current collection tab26extends outward from an end of the positive-electrode active material layer24.

The negative electrode sheet30includes a negative-electrode current collector32and a negative-electrode active material layer34that is formed on each surface of the negative-electrode current collector32. For example, metal foil that is suited for the negative electrode can preferably be used as the negative-electrode current collector32. In this embodiment, copper foil is used as the negative-electrode current collector32. In the illustrated example, the negative-electrode active material layers34are respectively supported on both of the surfaces of the negative-electrode current collector32. In addition, in the lateral direction X and the vertical direction Y, the negative-electrode active material layer34is formed to have the same width as total width of the negative-electrode current collector32.

The negative-electrode active material layer34contains a negative-electrode active material, a thickener, the binder, and the like. One type or two or more types of the materials that are used for the lithium-ion secondary battery in the related art can be used as the negative-electrode active material without any particular limitation. Examples of the negative-electrode active material are carbon-based materials such as graphite carbon and amorphous carbon, the lithium-transition metal composite oxide, and a lithium-transition metal nitride. In addition to such a negative-electrode active material, the binder such as polyvinylidene fluoride (PVDF) or styrene-butadiene rubber (SBR) and the thickener such as carboxymethyl cellulose (CMC) can be added to the negative-electrode active material layer34.

The negative electrode sheet30has a projected portion36that is not formed with the negative-electrode active material layer34and is projected outward from a portion of the negative electrode sheet30that is formed with the negative-electrode active material layer34. Because the negative-electrode active material layer34is not formed in this projected portion36, the negative-electrode current collector32is exposed in the projected portion36. A negative-electrode current collection tab36is formed by this projected portion36.

The separator40is a member that separates the positive electrode sheet20and the negative electrode sheet30from each other. In this example, the separator40is formed of a sheet material that has plural minute holes and specified width. For example, either one of a separator with a single-layer structure and a separator with a laminated structure, each of which is formed from a porous polyolefin resin, can be used as the separator40.

As described above, the laminated electrode body10is formed by laminating the plural positive electrode sheets20, the plural negative electrode sheets30, and the plural separators40. More specifically, the laminated electrode body10is configured by alternately laminating the positive electrode sheets20and the negative electrode sheets30via the separators40in a lamination direction (the thickness direction Z herein) so as to form plural layers. In addition, the laminated electrode body10has a laminated portion where the positive-electrode active material layer24and the negative-electrode active material layer34overlap each other via the separator40. This laminated portion is a portion where charge carriers (lithium ions herein) are transferred between the positive-electrode active material layer24and the negative-electrode active material layer34via the separator40, and is a portion that contributes to charging/discharging of the single cell100.

As shown inFIG. 1toFIG. 7, the laminated electrode body10is attached to the electrode terminals80,82that are provided on the battery case50(in this example, in the narrow portion56bof the flat surface56of the case body52). The laminated electrode body10is inserted in the case body52from the opening portion52bof the case body52. The laminated electrode body10is accommodated in the battery case50in a state where the lamination direction of the electrode body10matches the thickness direction Z (a state where the positive electrodes, the negative electrodes, and the separators are in parallel with the sealing plate54). In addition, in the laminated electrode body10, the positive-electrode current collection tabs26of the plural positive electrode sheets20, which are repeatedly laminated, are stacked in the lamination direction of the laminated electrode body10and are projected from an end surface of the laminated portion. These projected positive-electrode current collection tabs26are gathered in the lamination direction. Then, a positive-electrode lead terminal (not shown) is attached to a portion where the positive-electrode current collection tabs26are gathered, and is electrically connected to the above-described positive electrode terminal80. Furthermore, in the laminated electrode body10, the negative-electrode current collection tabs36of the plural negative electrode sheets30, which are repeatedly laminated, are stacked in the lamination direction of the laminated electrode body10and projected from the end surface of the laminated portion. These projected negative-electrode current collection tabs36are gathered in the lamination direction. Then, a negative-electrode lead terminal (not shown) is attached to a portion where the negative-electrode current collection tabs36are gathered, and is electrically connected to the above-described negative electrode terminal82. Such a laminated electrode body10is accommodated in an almost flat internal space of the case body52from the opening portion52bof the case body52. After the laminated electrode body10is accommodated in the case body52, the opening portion52bof the case body52is closed by the sealing plate54.

The electrolyte typically assumes a liquid state at a normal temperature (for example, 25° C.), and is preferred to always assume the liquid state within a use temperature range (for example, −20° C. to 60° C.). A solution that is produced by dissolving or dispersing a supporting electrolyte (for example, lithium salts, sodium salts, magnesium salts, and the like; and lithium salts in the lithium-ion secondary battery) in a nonaqueous solvent can preferably adopted as the electrolyte. As the supporting electrolyte, the supporting electrolyte that is used for the general lithium-ion secondary battery can appropriately be selected and adopted. For example, lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, Li(CF3SO2)2N, or LiCF3SO3can be used. Of these, LiPF6can preferably be adopted.

As the nonaqueous solvent, any of organic solvents that include various types of carbonates, ethers, esters, nitriles, sulfones, and lactones used for the general lithium-ion secondary battery can be used without any particular limitation. Specific examples of the nonaqueous solvent are ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

Next, a description will be made on a battery pack200according to this embodiment with additional reference toFIG. 8andFIG. 9.FIG. 8is a side view of the battery pack200, andFIG. 9is a view that illustrates a positional relationship among the gas discharge valves60of the single cells100in the battery pack200.

As shown inFIG. 8andFIG. 9, the battery pack200is configured by connecting a plurality (typically 6 or more (for example, 6 to 100), preferably 30 or more, further preferably 50 or more, even more preferably 60 or more) of the single cells100in series. In the battery case50that is provided in each of the single cells100, the positive electrode terminal80, which is electrically connected to the positive electrode20of the electrode body10, and the negative electrode terminal82, which is electrically connected to the negative electrode30, are provided. The positive electrode terminal80of one of the adjacent single cells100is electrically connected to the negative electrode terminal82of the other of the adjacent single cells100by an inter-terminal connector (not shown). More specifically, the plural single cells100are arranged in a state of being reversely directed in an alternate manner such that the positive electrode terminals80and the negative electrode terminals82of the plural single cells100are alternately disposed (the positive electrode terminal80of the single cell100is disposed next to the negative electrode terminal82of the adjacent single cell100). Thus, the plural single cells100are arranged such that the plural single cells100are reversely directed in the alternate manner so as to allow the case bodies52of the battery cases50provided in the single cells100oppose each other and to allow the sealing plates54of the battery cases50provided in the single cells100oppose each other.

A restraint member that collectively restrains the plural single cells100is disposed around the arranged single cells100. More specifically, paired end plates210A,210B are disposed at both ends of a group of the plural single cells100in the arrangement direction Z (on outer sides of single cells100A,100H that are located on outermost sides). In addition, a restraint band212is attached to the paired end plates210A,210B in a manner to run across the paired end plates210A,210B. Then, the above group of the single cells100is restrained in the arrangement direction by tightening and fixing ends of the restraint band212to the paired end plates210A,210B by screws214. In this way, the battery pack200can be constructed.

Here, in the above battery pack200, the plural single cells100are arranged such that the plural single cells100are reversely directed in the alternate manner so as to allow the case bodies52of the battery cases50provided in the single cells100oppose each other and to allow the sealing plates54of the battery cases50provided in the single cells100oppose each other. Thus, in the two adjacent single cells100(in the example ofFIG. 8, the single cell100A and a single cell100B, a single cell100C and a single cell100D, a single cell100E and a single cell100F, and a single cell100G and the single cell100H), the gas discharge valves60are disposed on mutually opposing surfaces of the battery cases50(the flat surfaces56of the case bodies52herein).

As shown inFIG. 2andFIG. 9, in the battery pack200according to this embodiment, the gas discharge valve60, which is provided in the battery case50of each of the single cells100, is disposed at the position that is offset from the center line C of the battery case50in the lateral direction X. More specifically, the length D from the center A of the gas discharge valve60to the center line C is greater than the length d from the center A of the gas discharge valve60to the outer edge B of the gas discharge valve60. Just as described, in the cases where the gas discharge valve60is disposed at the position that is offset from the center line C of the battery case50and the length D from the center A of the gas discharge valve60to the center line C is set to be greater than the length d from the center A of the gas discharge valve60to the outer edge B of the gas discharge valve60, in the battery cases50that are provided in the two adjacent single cells100, the gas discharge valves60that are provided on the mutually opposing surfaces (the flat surfaces56of the case bodies52herein) are disposed at positions that do not overlap each other when seen in the arrangement direction Z of the single cells100.

For this reason, unlike a battery structure in the related art shown inFIG. 10, it is possible to suppress various types of inconvenience that possibly occur when each of the gas discharge valves60is provided at a position that overlaps the center line C of the battery case50in the lateral direction X (that is, the gas discharge valves60that are provided on the mutually opposing surfaces of the battery cases50are in turn disposed at positions that overlap each other when seen in the arrangement direction Z). More specifically, when the gas discharge valves60are disposed at the positions that oppose each other when seen in the arrangement direction Z, the gas that is discharged from the gas discharge valve60of one of the adjacent single cells100is blown onto the gas discharge valve60of the other of the adjacent single cells100. In this way, the gas discharge valve60of the other of the adjacent single cells100possibly suffers from a negative effect. In addition, in the case where both of the gas discharge valves60are actuated simultaneously, discharge of the gas from both of the gas discharge valves60is mutually inhibited. As a result, there is a possibility that the gas produced in each of the battery cases50cannot efficiently be discharged. On the contrary, as described above, in the battery pack200according to this embodiment, the gas discharge valves60, which are provided on the mutually opposing surfaces of the battery cases50, are disposed at the positions that do not overlap each other when seen in the arrangement direction Z. Thus, the gas that is discharged from the gas discharge valve60of one of the adjacent single cells100is less likely to be blown onto the gas discharge valve60of the other of the adjacent single cells100. In addition, even in the case where both of the gas discharge valves60are actuated simultaneously, the discharge of the gas from both of the gas discharge valves60is less likely to be inhibited. Therefore, it is possible to provide the battery pack with this configuration that is less likely to cause the inconvenience as described above and is high in reliability.

According to the above battery pack200, the case body52has: the flat surface56on which the electrode body10is disposed; and the lateral wall surface57that is raised from the flat surface56so as to surround the electrode body10disposed on the flat surface56. The flat surface56is formed in the step shape that includes: the wide portion56aon which the electrode body10is disposed; and the narrow portion56b, the distance of which from the sealing plate54is shorter than that of the wide portion56a. The gas discharge valve60is provided in this narrow portion56bof the flat surface56. In the battery pack200with such a configuration, the distance between the sealing plate54and the narrow portion56bof the flat surface56, in which the gas discharge valve60is disposed, is shorter than the distance between the sealing plate54and the wide portion56a. Thus, a certain gap is provided between the narrow portion56bof the flat surface56and the adjacent single cell100. Just as described, because the certain gap is provided between the narrow portion56bof the flat surface56(in turn, the gas discharge valve60that is formed in the narrow portion56b) and the adjacent single cell100, the discharge of the gas from the gas discharge valve60is less likely to be inhibited by the adjacent single cell100. Therefore, the further efficient discharge of the gas can be realized.

In the above embodiment, the positive electrode terminal80and the negative electrode terminal82are disposed line-symmetrically about the center line C of the battery case50in the lateral direction X. In addition, the gas discharge valve60is disposed at the position that is offset from the center line C of the battery case50in the lateral direction X. In this way, when the single cells100are arranged in the state of being reversely directed in the alternate manner such that the positive electrode terminals80and the negative electrode terminals82of the single cells100are alternately disposed, the gas discharge valves60, which are provided on the mutually opposing surfaces of the battery cases50, are separately disposed in the line-symmetrical manner about the center line C of the battery case50. Therefore, the gas discharge valves60, which are provided at the positions not overlapping each other when seen in the arrangement direction, can easily be realized by only using the single cells100in the same shape.

In the above embodiment, the battery case50has: the concave case body52, one end of which is opened; and the sealing plate54that closes the opening portion52bof the case body52. The plural single cells100are arranged such that the plural single cells100are reversely directed in the alternate manner so as to allow the case bodies52of the battery cases50provided in the single cells100oppose each other and to allow the sealing plates54of the battery cases50provided in the single cells100oppose each other. In this way, for example, even when a worker does not pay special attention to assembly of the single cells100, each of the single cells100can be assembled in a correct direction that is set in advance (that is, a state where the single cells100are reversely directed in the alternate manner such that the positive electrode terminal80of the single cell100is disposed next to the negative electrode terminal82of the adjacent single cell100). Therefore, work efficiency at a time of assembling the battery pack200is improved.

According to the above battery pack200, one of the surfaces of the case body52, which is provided in each of the single cells100, in the thickness direction Z is opened. Just as described, the opening portion52bis provided in the case body52in the thickness direction Z. In this way, compared to a case where an opening is provided in the case body52in the lateral direction X or the vertical direction Y, the case body52can have the large opening. Therefore, even when the single cell100is made low profile by thinning the case body52in the thickness direction Z, the electrode body10can easily be accommodated (inserted) in the battery case50. In one preferred aspect, each of the single cells100, which constitutes the battery pack200, has the smaller dimension in the thickness direction Z than the dimensions in the lateral direction X and the vertical direction Y. In the illustrated example, the dimension of the single cell100in the lateral direction X is smaller than the dimension thereof in the vertical direction Y. In addition, the dimension of the single cell100in the thickness direction Z is smaller than the dimension thereof in the lateral direction X. For example, the dimension of the single cell100in the thickness direction Z can be 1/10 or smaller than 1/10 the dimension thereof in the lateral direction X, and can typically be 1/20 (for example, 1/30 or less than 1/30) the dimension thereof in the lateral direction X. The dimension of the single cell100in the thickness direction Z can be set to 1 mm to 20 mm (typically 5 mm to 10 mm), for example. The dimension of the single cell100in the lateral direction X can be set to 10 cm to 40 cm (typically 15 cm to 30 cm), for example. Such a single cell100that is large and low profile in size does not provide a space where the gas discharge valve60is disposed on the lateral surface of the single cell100. Therefore, application of this configuration yields a high technical value.

The disclosure has been described in detail so far. It should be noted that the above embodiment and examples are merely illustrative and the disclosure disclosed herein includes various modifications and deformations that are made to the above-described specified examples.

For example, in the above embodiment, a case where the gas discharge valve60is provided in the case body52is exemplified. However, the gas discharge valve60is not limited thereto. For example, the gas discharge valve60may be formed in the sealing plate54. In addition, a case where the battery case50has: the concave case body52, the one end of which is opened; and the sealing plate54in the flat plate shape that closes the opening portion52bof the case body52is exemplified. However, the shape of the sealing plate54is not limited to the flat plate shape. For example, the sealing plate54may be a concave sealing plate, one end of which is opened. In this case, the battery can be sealed by overlapping an opening of the sealing plate with the opening portion52bof the case body52and mutually joining peripheral edge portions thereof.

A preferred object to which the technique disclosed herein is applied is not limited to the above-described electrode body10of the laminated type. For example, the preferred object may be a wound electrode body. The wound electrode body includes the positive-electrode current collector22and the negative-electrode current collector32as strip-shaped sheet materials, the positive-electrode current collector22and the negative-electrode current collector32are aligned in a longitudinal direction, the positive-electrode active material layer24and the negative-electrode active material layer34are disposed to oppose each other in a state where the separator40is interposed therebetween, and these components are wound about a winding axis. In such a case, the above-described effects can be obtained.

The above battery pack200can be used in various applications, and can preferably be used as a power source of (a power supply for driving) a motor that is mounted on a vehicle, for example. Although a type of the vehicle is not particularly limited, automobiles such as a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), and an electric vehicle (EV) are typically exemplified.