Battery pack

Abstract

To provide a battery pack that can reduce the possibility of variations in the characteristics and lifespan of each battery. [Solution] A battery pack according to one embodiment of this technology comprises a plurality of batteries, a holder capable of supporting the plurality of batteries, a case capable of housing the plurality of batteries and the holder, and a fixing member disposed between at least one of the end faces of each battery and the inner wall of the case. The fixing member is an elastic porous layer. In the fixing member, the compression ratio (thickness before compression / thickness after compression) of the first portion facing one or more high-heat-generating batteries that have relatively high temperatures in the heat distribution of the plurality of batteries when the battery pack is in use is higher than the compression ratio (thickness before compression / thickness after compression) of the second portion facing one or more low-heat-generating batteries that have relatively low temperatures in the heat distribution.

Description

Technical Field

[0001] This technology relates to a battery pack.

Background Art

[0002] Since electronic devices are widely popular, the development of batteries as power sources applied to such electronic devices has been underway. In this case, in order to handle a plurality of batteries easily and safely, a battery pack including the plurality of batteries has been proposed.

[0003] Regarding technologies related to the configuration of a battery pack, various studies have been made. For example, Patent Document 1 discloses a technology for discharging heat accumulated in a battery pack to the outside.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when there is a variation in the temperature of each battery when a current is passed through a plurality of batteries included in a battery pack, there is a possibility that variations will occur in the characteristics and lifespan of each battery. It is desirable to provide a battery pack capable of reducing the possibility of variations in the characteristics and lifespan of each battery.

Means for Solving the Problems

[0006] A battery pack relating to the first aspect of this technology comprises a plurality of batteries and a holder capable of supporting the plurality of batteries in one or more layers. The battery pack further comprises a case capable of housing the plurality of batteries and the holder, and a fixing member disposed between at least one of the end faces of each battery and the inner wall of the case. The fixing member is an elastic porous layer. In the fixing member, the compression ratio (thickness before compression / thickness after compression) of the first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the plurality of batteries when the battery pack is in use, is higher than the compression ratio (thickness before compression / thickness after compression) of the second portion facing one or more low-heat-generating batteries, which have relatively lower temperatures in the heat distribution.

[0007] A battery pack relating to a second aspect of this technology comprises a plurality of batteries and a holder capable of supporting the plurality of batteries in one or more layers. The battery pack further comprises a case capable of housing the plurality of batteries and the holder, and a fixing member disposed between at least one of the end faces of each battery and the inner wall of the case. The fixing member is an elastic porous layer. In the fixing member, the void density of a first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the plurality of batteries when the battery pack is in use, is lower than the void density of a second portion facing one or more low-heat-generating batteries, which have relatively lower temperatures in the heat distribution. [Effects of the Invention]

[0008] In the battery pack relating to the first aspect of this technology, in the fixing member which is an elastic porous layer, the compression ratio (thickness before compression / thickness after compression) of the first portion facing one or more high-heat-generating batteries that have relatively higher temperatures in the heat distribution of the batteries during use of the battery pack is higher than the compression ratio (thickness before compression / thickness after compression) of the second portion facing one or more low-heat-generating batteries that have relatively lower temperatures in the heat distribution of the batteries during use of the battery pack. As a result, the path for conducting heat emitted from the batteries in the case to the case is mainly provided in the first portion facing one or more high-heat-generating batteries that have relatively higher temperatures in the heat distribution of the batteries during use of the battery pack. As a result, the temperature distribution of the batteries in the case becomes more uniform compared to when no fixing member is provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery can be reduced.

[0009] In the battery pack relating to the second aspect of this technology, in the fixing member which is an elastic porous layer, the void density of the first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the batteries during use of the battery pack, is lower than the void density of the second portion facing one or more low-heat-generating batteries, which have relatively lower temperatures in the heat distribution. As a result, the path for conducting heat emitted from the batteries in the case to the case is mainly provided in the first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the batteries during use of the battery pack. Consequently, the temperature distribution of the batteries in the case becomes more uniform compared to the case where no fixing member is provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a diagram showing an example of a perspective view configuration of a battery pack according to the first embodiment of this technology. [Figure 2] Figure 2 shows an example of a perspective view of a battery module, which is one of the components contained in the battery pack shown in Figure 1. [Figure 3]Figure 3 shows an example of the unfolded, oblique view configuration of the battery pack shown in Figure 1. [Figure 4] Figure 4 shows an example of the cross-sectional configuration of the holder shown in Figure 2. [Figure 5] Figure 5 is a diagram showing a plan view example of the battery pack in Figure 1 with either the upper or lower case removed. [Figure 6] Figure 6 shows an example of the cross-sectional configuration of the battery pack shown in Figure 5. [Figure 7] Figure 7(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 3 before compression. Figure 7(B) shows an example of the planar configuration of the heat transfer material in Figure 7(A). [Figure 8] Figure 8(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 3 after compression. Figure 8(B) shows an example of the planar configuration of the heat transfer material in Figure 8(A). [Figure 9] Figure 9 shows a modified example of the cross-sectional configuration near the battery end face in the battery pack shown in Figure 1. [Figure 10] Figure 10 shows a modified example of the planar configuration of the battery pack in Figure 1, with either the upper or lower case removed. [Figure 11] Figure 11 is a diagram showing an example of the cross-sectional configuration of the battery pack shown in Figure 10. [Figure 12] Figure 12(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 10 before compression. Figure 12(B) shows an example of the planar configuration of the heat transfer material in Figure 12(A). [Figure 13] Figure 13(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 10 after compression. Figure 13(B) shows an example of the planar configuration of the heat transfer material in Figure 13(A). [Figure 14] Figure 14 shows an example of a modified cross-sectional configuration near the battery end face in the battery pack shown in Figure 10. [Figure 15] Figure 15 shows a modified example of the planar configuration of the battery pack in Figure 1, with either the upper or lower case removed. [Figure 16] Figure 16 is a diagram showing an example of the cross-sectional configuration of the battery pack shown in Figure 15. [Figure 17] FIG. 17(A) is a diagram showing a cross-sectional configuration example of the heat transfer material in the state before compression in FIG. 15. FIG. 17(B) is a diagram showing a plan configuration example of the heat transfer material in FIG. 17(A). [Figure 18] FIG. 18(A) is a diagram showing a cross-sectional configuration example of the heat transfer material in the state after compression in FIG. 15. FIG. 18(B) is a diagram showing a plan configuration example of the heat transfer material in FIG. 18(A). [Figure 19] FIG. 19 is a diagram showing a modified example of the cross-sectional configuration near the battery end face in the battery pack of FIG. 15. [Figure 20] FIG. 20 is a diagram showing a modified example of the plan configuration in the state where the upper case or the lower case is removed in the battery pack of FIG. 1. [Figure 21] FIG. 21 is a diagram showing a cross-sectional configuration example of the battery pack of FIG. 20. [Figure 22] FIG. 22(A) is a diagram showing a cross-sectional configuration example of the heat transfer material in the state before compression in FIG. 20. FIG. 22(B) is a diagram showing a plan configuration example of the heat transfer material in FIG. 22(A). [Figure 23] FIG. 23(A) is a diagram showing a cross-sectional configuration example of the heat transfer material in the state after compression in FIG. 20. FIG. 23(B) is a diagram showing a plan configuration example of the heat transfer material in FIG. 23(A). [Figure 24] FIG. 24 is a diagram showing a modified example of the cross-sectional configuration near the battery end face in the battery pack of FIG. 20. [Figure 25] FIG. 25 is a diagram showing a perspective configuration example of the battery pack according to the second embodiment of the present technology. [Figure 26] FIG. 26 is a diagram showing a perspective configuration example of a battery module which is one of the contents of the battery pack of FIG. 25. [Figure 27] FIG. 27 is a diagram showing an exploded perspective configuration example of the battery pack of FIG. 25. [Figure 28] FIG. 28 is a diagram showing a perspective configuration example of the battery in FIG. 27. [Figure 29] FIG. 29 is a diagram showing a plan configuration example in the state where the upper case or the lower case is removed in the battery pack of FIG. 25. [Figure 30]Figure 30 is a diagram showing an example of the cross-sectional configuration of the battery pack shown in Figure 25. [Figure 31] Figure 31(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 29 before compression. Figure 31(B) shows an example of the planar configuration of the heat transfer material in Figure 31(A). [Figure 32] Figure 32(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 29 after compression. Figure 32(B) shows an example of the planar configuration of the heat transfer material in Figure 31(A). [Figure 33] Figure 33 shows a modified example of the planar configuration of the battery pack in Figure 25, with either the upper or lower case removed. [Figure 34] Figure 34 is a diagram showing an example of the cross-sectional configuration of the battery pack shown in Figure 33. [Figure 35] Figure 35(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 33 before compression. Figure 35(B) shows an example of the planar configuration of the heat transfer material in Figure 35(A). [Figure 36] Figure 36(A) shows an example of the cross-sectional configuration of the heat transfer material in Figure 33 after compression. Figure 36(B) shows an example of the planar configuration of the heat transfer material in Figure 36(A). [Modes for carrying out the invention]

[0011] The embodiments for implementing this technology will be described in detail below with reference to the drawings. The order of explanation is as follows. 1. First Embodiment 1-1. Composition 1-2. Effects 2. Modified form of the first embodiment 3. Second Embodiment 3-1. Composition 3-2. Effects 4. Modified form of the second embodiment

[0012] <1. First Embodiment> First, we will describe the battery pack 1 of the first embodiment of this technology.

[0013] The battery pack 1 described here is a power source equipped with multiple batteries and is applicable to a variety of uses, such as electronic devices. Details of the applications of battery pack 1 will be described later. The type of battery is not particularly limited and may be either a primary battery or a secondary battery. The type of secondary battery is not particularly limited, but specifically, it may be a lithium-ion secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium ions. The number of batteries is not particularly limited and can be set arbitrarily. The following description will focus on the case where the batteries are secondary batteries (lithium-ion secondary batteries). In other words, the battery pack 1 described below is a power source equipped with multiple secondary batteries.

[0014] [1-1. Structure] Figure 1 shows an example of a perspective view of the battery pack 1 according to the first embodiment of this technology. Figure 2 shows an example of a perspective view of a part of the contents of the battery pack 1. Figure 3 shows an example of a perspective view of the contents of the battery pack 1 in an unfolded state.

[0015] The battery pack 1 comprises, for example, an outer case 10 and a battery module 20 housed in the outer case 10, as shown in Figures 1 and 2. The battery pack 1 further comprises, for example, tabs 50a and 50b, two heat transfer materials 60, and a control board 70, as shown in Figures 1, 2, and 3. The outer case 10 corresponds to a specific example of the "case" according to one embodiment of the present disclosure. The heat transfer material 60 corresponds to a specific example of the "fixing member" according to one embodiment of the present disclosure.

[0016] The outer casing 10 is composed of a lower case 10a and an upper case 10b, as shown in Figure 3, for example. The lower case 10a and the upper case 10b are stacked on top of each other to form a housing space for the battery module 20. The outer casing 10 is capable of housing the battery module 20. The outer casing 10 (for example, the lower case 10a) is provided with an external terminal 11 connected to the control board 70. Multiple batteries 30, described later, are connected to the external terminal 11 via the control board 70.

[0017] The outer casing 10 is made of a resin material such as polyethylene (PE), polypropylene (PP), polycarbonate (PC), modified polyphenylene ether (mPPE), polyamide (PA), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer resin (ABS), or polyacetal (POM). The outer casing 10 may also be made of a resin material in which a conductive material such as a metal or conductive filler is dispersed. In this case, the resin material may be one of the resin materials described above.

[0018] The battery pack 1 has a discharge mode in which it supplies power output from the battery module 20 to a load via the external terminal 11. The battery pack 1 may also have a charge mode in which it stores power supplied via the external terminal 11 from a power source connected to the external terminal 11 in the battery module 20. If the battery 30 is a secondary battery, the control board 70 switches between the discharge mode and the charge mode depending on the type of connected object connected to the external terminal 11. If the battery 30 is a primary battery, the control board 70 performs only the discharge mode. The control board 70 is in contact with the upper surface of the battery holder 40, for example. The control board 70 is fixed to the upper surface of the battery holder 40 by, for example, pressure fixing, screw fixing, adhesive fixing, or ultrasonic welding.

[0019] The battery module 20 includes a plurality of batteries 30 and a battery holder 40 capable of supporting the plurality of batteries 30. The battery holder 40 corresponds to a specific example of the "holder" according to one embodiment of the present disclosure. The plurality of batteries 30 are electrically connected to each other via tabs 50a and 50b. The plurality of batteries 30 are connected to each other in series by tabs 50a and 50b, for example. However, the connection configuration of the plurality of batteries 30 is not limited to the above. For example, if a plurality of batteries 30 that are part of the plurality of batteries 30 are connected to each other in series by tabs 50a and 50b, and further, the plurality of batteries 30 connected to each other in series are referred to as a series unit, the plurality of series units may be connected to each other in parallel by tabs 50a and 50b.

[0020] Tabs 50a and 50b are made of, for example, metal lead plates. Each battery 30 is either a primary or secondary battery. If each battery 30 is a secondary battery, the type of secondary battery is not particularly limited, but specifically, it is a lithium-ion secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium ions. The following description will focus on the case where each battery 30 is a secondary battery (lithium-ion secondary battery). That is, the battery pack 1 described below is a power source equipped with multiple secondary batteries.

[0021] The battery 30 has a first end face S1 and a second end face S2 that face each other. The battery 30 extends in a first direction in which the first end face S1 and the second end face S2 face each other. Tabs 50a and 50b are positioned opposite each other in the first direction with multiple batteries 30 in between. Hereinafter, in each battery 30, the end face facing tab 50a will be referred to as the first end face S1, and the end face facing tab 50b will be referred to as the second end face S2. In other words, the multiple batteries 30 are arranged so that the first end face S1 of each battery 30 faces a common direction (the direction of tab 50a).

[0022] The battery 30 has a positive electrode 31 and a negative electrode 32. The positive electrode 31 is provided on either the first end face S1 or the second end face S2. The negative electrode 32 is provided on the end face of the first end face S1 or the second end face S2 that does not have the positive electrode 31. Figure 3 illustrates a configuration in which, of the 10 batteries 30, the positive electrode 31 is provided on the first end face S1 of 5 batteries 30, and the negative electrode 32 is provided on the first end face S1 of the remaining 5 batteries 30. The battery 30 has a cylindrical shape, for example, with the first end face S1 and the second end face S2 extending in a first direction opposite to each other, and the first end face S1 and the second end face S2 are each, for example, circular in shape. The shape of the battery 30 is not limited to a cylindrical shape. The shapes of the first end face S1 and the second end face S2 are not limited to circular shapes. The positive electrode 31 is made of a metal material. The positive electrode 31 has a protruding shape at the end face of the battery 30. The negative electrode 32 is made of a metal material. The negative electrode 32 forms a flat surface at the end face of the battery 30.

[0023] Assume that multiple batteries 30 are arranged in a two-dimensional direction (a second direction and a third direction perpendicular to both the first and second directions) that is perpendicular to the longitudinal direction (first direction) of the batteries 30. In this case, the first end face S1 of each battery 30 provided in the battery pack 1 is located in the first plane, and the second end face S2 of each battery 30 provided in the battery pack 1 is located in the second plane. Tab 50a is in contact with multiple electrodes located in the first plane, either directly or via a conductive material such as solder. Tab 50b is in contact with multiple electrodes located in the second plane, either directly or via a conductive material such as solder.

[0024] In this specification, "extension direction of the battery 30" means the direction parallel to the direction in which the first end face S1 and the second end face S2 face each other, when the battery 30 has a columnar shape in which the first end face S1 and the second end face S2 extend in directions opposite to each other. In this specification, "arrangement direction of the battery 30" means the direction perpendicular to the direction in which the first end face S1 and the second end face S2 face each other, when the battery 30 has a columnar shape in which the first end face S1 and the second end face S2 extend in directions opposite to each other.

[0025] The holder 40 is composed of a pair of holders 40a and 40b, as shown in Figures 3 and 4. Both holders 40a and 40b have a common structure. Figure 4 shows an example of the cross-sectional configuration of holder 40b.

[0026] Holders 40a and 40b each have a side plate portion 41, for example, as shown in Figure 4. The side plate portion 41 of holder 40a and the side plate portion 41 of holder 40b are positioned opposite each other in the extending direction (first direction) of each battery 30, with multiple batteries 30 in between. In holders 40a and 40b, the side plate portion 41 has an opening 42 at a location facing the positive electrode 31 and negative electrode 32 of each battery 30. Therefore, the positive electrode 31 or negative electrode 32 is exposed at the opening 42. Tab 50a is positioned close to the side plate portion 41 of holder 40a. Tab 50a contacts the positive electrode 31 or negative electrode 32 of each battery 30 directly or via a conductive material such as solder through the opening 42 of holder 40a. Tab 50b is positioned close to the side plate portion 41 of holder 40b. The tab 50b is in contact with the positive electrode 31 or negative electrode 32 of each battery 30, either directly or via a conductive material such as solder, through the opening 42 of the holder 40b.

[0027] Each holder 40a and 40b further has a support portion 43 that supports multiple batteries 30 in a layered manner with predetermined gaps between them, for example, as shown in Figure 4. Figure 4 illustrates how the support portion 43 is provided to support multiple batteries 30 in two layers: the lowest layer and the uppermost layer. The lowest layer is the layer at the very bottom when the battery pack 1 (battery module 20) is viewed from the direction shown in Figure 4. Alternatively, the lowest layer is the layer closest to the lower case 10a. The uppermost layer is the layer at the very top when the battery pack 1 (battery module 20) is viewed from the direction shown in Figure 4. Alternatively, the uppermost layer is the layer closest to the upper case 10b.

[0028] A side plate portion 41 is connected to one end of the support portion 43, and the other end of the support portion 43 is an opening 44. The support portion 43 is provided with a housing portion 45 connected to the opening 42 and the opening 44. A portion of the battery 30 is housed in the housing portion 45. The housing portion 45 is structured to accommodate multiple batteries 30 with the first end face S1 of each battery 30 facing a common direction (the direction of the tab 50a). If the battery 30 is cylindrical in shape extending in the first direction, the housing portion 45 is provided with, for example, a cylindrical void extending in the first direction.

[0029] The holder 40 (40a, 40b) is made of a resin material such as polyethylene (PE), polypropylene (PP), polycarbonate (PC), modified polyphenylene ether (mPPE), polyamide (PA), polybutylene terephthalate (PBT), copolymer synthetic resin of acrylonitrile-butadiene-styrene (ABS), or polyacetal (POM). The wall thickness of the holder 40 (40a, 40b) is preferably within a range that allows for easy molding, for example, 0.5 mm to 5 mm.

[0030] Figure 5 shows a plan view example of the battery pack 1 with the lower case 10a or upper case 10b removed. Figure 6 shows a cross-sectional view example of the battery pack 1. Figure 6 illustrates how a holder 40 (holder 40a) is provided to support 10 batteries 30 in two layers, the lowest and the uppermost layer. In Figure 6, five batteries 30 (30a, 30b, 30c, 30d, 30e) are arranged in a row in the upper layer, and five batteries 30 (30f, 30g, 30h, 30i, 30j) are arranged in a row in the lower layer. In Figure 6, the three batteries 30 in the center of the upper layer (30b, 30c, 30d) and the three batteries 30 in the center of the lower layer (30g, 30h, 30i) correspond to the multiple central batteries located in the center of each layer. In Figure 6, the two batteries 30 (30a, 30e) at both ends of the upper section and the two batteries 30 (30f, 30j) at both ends of the lower section correspond to multiple peripheral batteries, which are different from the multiple central batteries located in the center of each layer.

[0031] Tab 50a and one of the heat transfer materials 60 are positioned between the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the side plate portion 41 of the holder 40a. The inner wall W1 refers to the portion of the inner wall of the outer case 10 (lower case 10a and upper case 10b) that faces the side plate portion 41 of the holder 40a. Tab 50a is positioned between the side plate portion 41 of the holder 40a and the heat transfer material 60. The heat transfer material 60 is positioned between the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50a. The heat transfer material 60 is in contact with the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50a. The heat transfer material 60 is compressed by the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the side plate portion 41 and tab 50a of the holder 40a. If the tab 50a is formed in a planar shape, the heat transfer material 60 is compressed by the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50a.

[0032] Tab 50b and the other heat transfer material 60 are positioned between the inner wall W2 of the outer case 10 (lower case 10a and upper case 10b) and the side plate portion 41 of the holder 40b. The inner wall W2 refers to the portion of the inner wall of the outer case 10 (lower case 10a and upper case 10b) that faces the side plate portion 41 of the holder 40b. Tab 50b is positioned between the side plate portion 41 of the holder 40b and the heat transfer material 60. The heat transfer material 60 is positioned between the inner wall W2 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50b. The heat transfer material 60 is in contact with the inner wall W2 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50b. The heat transfer material 60 is compressed by the inner wall W2 of the outer case 10 (lower case 10a and upper case 10b) and the side plate portion 41 and tab 50b of the holder 40b. If the tab 50b is formed in a planar shape, the heat transfer material 60 is compressed by the inner wall W1 of the outer case 10 (lower case 10a and upper case 10b) and the tab 50b.

[0033] The inner walls W1 and W2 each have a protrusion 12 at a location facing the central portion 60X (described later) of the heat transfer material 60. The protrusion 12 is provided at a location facing one or more high-heat generating batteries that are relatively hotter in the heat distribution of the multiple batteries 30 when the battery pack 1 is in use (during charging or discharging) in a state where the heat transfer material 60 is not provided and there is an air gap G between the outer case 10 and the holder 40. The heat distribution of the multiple batteries 30 when the battery pack 1 is in use (during charging or discharging) can be confirmed by attaching a thermocouple to the surface of each battery 30 and measuring the temperature change of each battery 30 while charging and discharging each battery 30, or by photographing all the batteries 30 inside the outer case 10 with a thermal camera during charging and discharging and measuring the temperature change.

[0034] Of the inner walls W1 and W2, the areas where the protrusions 12 are not formed are surfaces that are lower in height than the protrusions 12, and are the base of the protrusions 12 or flat surfaces. Of the inner walls W1 and W2, the areas where the protrusions 12 are not formed are mainly located in places where the heat transfer material 60 is not provided and where there is an air gap G between the outer case 10 and the holder 40, and the heat distribution of the multiple batteries 30 during use (charging or discharging) is in a location that faces one or more low-heat generating batteries that are relatively lower in temperature.

[0035] In Figure 6, the multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i) in the center of each layer correspond to one specific example of "one or more high-heat generating batteries." The reason why the multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i) in the center of each layer correspond to high-heat generating batteries with relatively high temperatures in the heat distribution described above is that the heat emitted from each battery 30 tends to accumulate in the central part of each layer.

[0036] The heat transfer material 60 has a high-compression section 60a and a low-compression section 60b. The high-compression section 60a is provided in the central portion 60X (described later) of the heat transfer material 60. As described later, the high-compression section 60a includes multiple high-compression voids 62a as multiple voids 62. The low-compression section 60b is provided in the peripheral portion 60Y (described later) of the heat transfer material 60. As described later, the low-compression section 60b includes multiple low-compression voids 62b as multiple voids 62.

[0037] Next, the heat transfer material 60 will be described with reference to Figures 6, 7, and 8. Figure 7(A) shows an example of the cross-sectional configuration of the heat transfer material 60 before it is installed inside the outer casing 10 (hereinafter referred to as the "pre-compression state"). Figure 7(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 7(A). Figure 8(A) shows an example of the cross-sectional configuration of the heat transfer material 60 after it has been installed inside the outer casing 10 (hereinafter referred to as the "post-compression state"). Figure 8(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 8(A).

[0038] The heat transfer material 60 supports the battery module 20 within the battery holder 40 via tabs 50a or 50b. The heat transfer material 60 also serves as a heat conduction path that transmits (dissipates) heat generated from the multiple batteries 30 within the battery holder 40 to the outer casing 10. The heat transfer material 60 is composed of a resin member 61 with a higher thermal conductivity than gases such as air or nitrogen. The resin member 61 is an elastic porous layer and contains numerous voids 62. In the resin member 61, the numerous voids 62 may be connected to each other or provided independently of each other. The voids 62 are filled with gases such as air or nitrogen. The resin member 61 is composed of, for example, urethane foam, polyethylene foam, EVA foam, or rubber sponge.

[0039] In its uncompressed state, the heat transfer material 60 is in the form of a sheet with a thickness that is approximately uniform regardless of location, as shown in Figure 7(A), for example. In the uncompressed state of the heat transfer material 60, the portion facing "one or more high-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the central portion 60X. Also, in the uncompressed state of the heat transfer material 60, the portion facing "one or more low-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the peripheral portion 60Y.

[0040] The central portion 60X is, for example, the area facing multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i), and is the area surrounded by the peripheral portion 60Y, as shown in Figure 7(B). The central portion 60X corresponds to one specific example of the "first part" of one embodiment of the present disclosure. The peripheral portion 60Y corresponds to one specific example of the "second part" of one embodiment of the present disclosure. In the heat transfer material 60 before compression, the thickness of the central portion 60X is Dx, and the thickness of the peripheral portion 60Y is Dy. Also, in the heat transfer material 60 before compression, the void density of the central portion 60X is Nx, and the void density of the peripheral portion 60Y is Ny. The thicknesses Dx and Dy are approximately equal to each other. The void densities Nx and Ny are approximately equal to each other.

[0041] When the heat transfer material 60 is installed inside the outer case 10, it is compressed in the thickness direction by the side plate portion 41 and at least the tab 50a or tab 50b, and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b). In the heat transfer material 60, the central portion 60X is compressed by the side plate portion 41 and at least the tab 50a or tab 50b, and the protrusion 12. As a result, a recess 63 corresponding to the shape of the protrusion 12 is formed in the central portion 60X, for example, as shown in Figure 8(A). As a result, the void 62 inside the central portion 60X is compressed, becoming a flattened, highly compressed void 62a compressed in the thickness direction of the central portion 60X. Consequently, the central portion 60X becomes a highly compressed portion 60a. Let Da be the thickness of the central portion 60X at this time, and let Na be the void density of the central portion 60X.

[0042] In the heat transfer material 60, the peripheral portion 60Y is compressed by at least the tab 50a or tab 50b among the side plate portion 41 and the inner wall W1 or inner wall W2 where the protrusion 12 has not yet been formed. As a result, the peripheral portion 60Y forms a shape corresponding to the inner wall W1 or inner wall W2 where the protrusion 12 has not yet been formed, as shown in Figure 8(A), for example. As a result, the void 62 within the peripheral portion 60Y is slightly compressed, becoming a slightly flattened, low-compression void 62b that is slightly compressed in the thickness direction of the peripheral portion 60Y. Consequently, the peripheral portion 60Y becomes a low-compression portion 60b. Let the thickness of the peripheral portion 60Y at this time be Db, and the void density of the peripheral portion 60Y be Nb.

[0043] In the heat transfer material 60, the compression ratio of the central portion 60X (thickness Dx before compression / thickness Da after compression) is higher than that of the peripheral portion 60Y (thickness Dy before compression / thickness Db after compression). Also, in the compressed state of the heat transfer material 60, the void density Na of the central portion 60X is lower than that of the peripheral portion 60Y (void density Nb). In the heat transfer material 60, the thermal conductivity of the central portion 60X and the peripheral portion 60Y changes before and after compression. In particular, the thermal conductivity of the central portion 60X changes significantly before and after compression. In the compressed state of the heat transfer material 60, the thermal conductivity of the central portion 60X is higher than that of the peripheral portion 60Y. In other words, the heat transfer material 60 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 20 over heat emitted from "one or more low-heat-generating batteries" in the battery module 20, making it possible to achieve a more uniform heat distribution among the multiple batteries 30 when the battery pack 1 is in use compared to when the heat transfer material 60 is not provided.

[0044] [1-2. Effects] Next, I will explain the effects of battery pack 1.

[0045] Due to the widespread use of electronic devices, the development of batteries as power sources for these devices is progressing. In this case, battery packs containing multiple batteries have been proposed to facilitate easy and safe handling of these batteries. Various studies have been conducted on technologies related to the configuration of battery packs. For example, Patent Document 1 discloses a technology for releasing heat accumulated inside a battery pack to the outside. However, if there is variation in the temperature of each battery when current is passed through the multiple batteries contained in a battery pack, there is a possibility that variations will occur in the characteristics and lifespan of each battery.

[0046] On the other hand, in this embodiment, in the heat transfer material 60 which is an elastic porous layer, the compression ratio (thickness before compression / thickness after compression) of the central portion 60X is higher than the compression ratio (thickness before compression / thickness after compression) of the peripheral portion 60Y. As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the central portion 60X. As a result, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0047] In this embodiment, in the heat transfer material 60, which is an elastic porous layer, the void density Na of the central portion 60X when compressed is lower than the void density Nb of the peripheral portion 60Y when compressed. As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the central portion 60X. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0048] In this embodiment, the heat transfer material 60 is in contact with at least tab 50a or tab 50b of the side plate portion 41 of holder 40a or holder 40b and tab 50a or tab 50b. This allows heat generated from "one or more high-heat generating batteries" in the battery module 20 to be efficiently transferred (dissipated) to the outer casing 10 via the heat transfer material 60. As a result, the temperature distribution of the multiple batteries 30 in the outer casing 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0049] In this embodiment, the inner walls W1 and W2 of the outer case 10 (lower case 10a and upper case 10b) are provided with protrusions 12 at locations facing the central portion 60X. As a result, the central portion 60X of the heat transfer material 60 is compressed by the protrusions 12, so that the thermal conductivity of the central portion 60X of the heat transfer material 60 becomes higher than that of the peripheral portion 60Y. Consequently, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be efficiently transferred (dissipated) to the outer case 10 via the heat transfer material 60. Therefore, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0050] <2. Modified form of the first embodiment> Next, a modified example of the battery pack 1 according to the first embodiment will be described.

[0051] (Variation A) Figure 9 shows a modified example of the cross-sectional configuration near the battery end face in the battery pack 1. In the first embodiment, the heat transfer material 60 may be in contact with the side plate portion 41 of the holder 40a or holder 40b, the tab 50a or tab 50b, and the end of each battery 30, as shown in Figure 9. In this case, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be transmitted (dissipated) to the outer casing 10 more efficiently via the heat transfer material 60 than in the first embodiment. As a result, the temperature distribution of the multiple batteries 30 in the outer casing 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0052] (Torture B) Figure 10 shows a modified example of the planar configuration of the battery pack 1 with the lower case 10a or upper case 10b removed. Figure 11 shows an example of the cross-sectional configuration of the battery pack 1 in Figure 10. In the first embodiment, the inner walls W1 and W2 may each have a protrusion 12 at a location facing the peripheral portion 60Y of the heat transfer material 60, rather than the central portion 60X of the heat transfer material 60, as shown in Figure 10. In this case, the locations of the inner walls W1 and W2 where the protrusion 12 is not formed are each provided at a location facing the central portion 60X of the heat transfer material 60, rather than the peripheral portion 60Y of the heat transfer material 60, as shown in Figure 10.

[0053] The protrusion 12 is provided at a location facing "one or more high-heat-generating batteries". In this modified example, the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends correspond to one specific example of "one or more high-heat-generating batteries". Of the inner walls W1, W2, the areas where the protrusion 12 is not formed are provided at locations facing "one or more low-heat-generating batteries". In this modified example, the multiple batteries 30 (30b, 30c, 30d, 30f, 30g, 30h) in the center correspond to one specific example of "one or more low-heat-generating batteries".

[0054] In Figure 11, the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer correspond to one specific example of "one or more high-heat-generating batteries." Two possible reasons why the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer correspond to high-heat-generating batteries with relatively high temperatures in the heat distribution described above are as follows. It should be noted that there may also be other reasons besides the two below that cause the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer to correspond to high-heat-generating batteries with relatively high temperatures in the heat distribution described above.

[0055] • Cause #1 The current flowing through tab 50a or tab 50b causes localized high temperatures at the ends of tab 50a or tab 50b that face multiple batteries 30 (30a, 30e, 30f, 30j) at each layer. • Cause #2 The battery holder 40 is supported within the outer case 10 by protrusions that project toward the outer case 10, which are provided on the surface near the multiple batteries 30 (30b, 30c, 30d) in the center of the lowest layer of the battery holder 40, and the heat emitted from each battery 30 is transmitted (dissipated) to the outer case 10 through these protrusions.

[0056] Next, the heat transfer material 60 related to this modified example will be described with reference to Figures 11, 12, and 13. Figure 12(A) shows an example of the cross-sectional configuration of the heat transfer material 60 before it is installed inside the outer case 10 (hereinafter referred to as the "pre-compression state"). Figure 12(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 12(A). Figure 13(A) shows an example of the cross-sectional configuration of the heat transfer material 60 after it has been installed inside the outer case 10 (hereinafter referred to as the "post-compression state"). Figure 13(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 13(A).

[0057] In its uncompressed state, the heat transfer material 60 is in the form of a sheet with a thickness that is approximately uniform regardless of location, as shown in Figure 12(A), for example. In the uncompressed state of the heat transfer material 60, the portion facing "one or more high-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the peripheral portion 60Y. Also, in the uncompressed state of the heat transfer material 60, the portion facing "one or more low-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the central portion 60X. In this modified example, the central portion 60X corresponds to a specific example of the "second part" of one embodiment of the present disclosure. The peripheral portion 60Y corresponds to a specific example of the "first part" of one embodiment of the present disclosure.

[0058] The central portion 60X is, for example, the area facing multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i), and is sandwiched between two peripheral portions 60Y, as shown in Figure 12(B). In the heat transfer material 60 before compression, let the thickness of the central portion 60X be Dx and the thickness of the peripheral portion 60Y be Dy. Also, in the heat transfer material 60 before compression, let the void density of the central portion 60X be Nx and the void density of the peripheral portion 60Y be Ny. The thicknesses Dx and Dy are approximately equal to each other. The void densities Nx and Ny are approximately equal to each other.

[0059] When the heat transfer material 60 is installed inside the outer case 10, it is compressed in the thickness direction by at least tab 50a or tab 50b of the side plate portion 41 and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b). In the heat transfer material 60, the peripheral portion 60Y is compressed by at least tab 50a or tab 50b of the side plate portion 41 and the convex portion 12. As a result, a recess 63 corresponding to the convex portion 12 is formed in the peripheral portion 60Y, for example, as shown in Figure 13(A). As a result, the void 62 in the peripheral portion 60Y is compressed, becoming a flattened, highly compressed void 62a compressed in the thickness direction of the peripheral portion 60Y. Let Db be the thickness of the peripheral portion 60Y at this time, and let Nb be the void density of the peripheral portion 60Y.

[0060] In the heat transfer material 60, the central portion 60X is compressed by at least tab 50a or tab 50b of the side plate portion 41 and the inner wall W1 or inner wall W2 where the protrusion 12 has not yet been formed. As a result, the central portion 60X forms a shape corresponding to the inner wall W1 or inner wall W2 where the protrusion 12 has not yet been formed, as shown in Figure 13(A), for example. As a result, the void 62 within the central portion 60X is slightly compressed, becoming a slightly flattened, low-compression void 62b that is slightly compressed in the thickness direction of the central portion 60X. Let Da be the thickness of the central portion 60X at this time, and let Na be the void density of the central portion 60X.

[0061] In the heat transfer material 60, the compression ratio of the peripheral portion 60Y (thickness Dy before compression / thickness Db after compression) is higher than that of the central portion 60X (thickness Dx before compression / thickness Da after compression). Also, in the compressed state of the heat transfer material 60, the void density Nb of the peripheral portion 60Y is lower than that of the central portion 60X (void density Na). In the heat transfer material 60, the thermal conductivity of the central portion 60X and the peripheral portion 60Y changes before and after compression. In particular, the thermal conductivity of the peripheral portion 60Y changes significantly before and after compression. In the compressed state of the heat transfer material 60, the thermal conductivity of the peripheral portion 60Y is higher than that of the central portion 60X. In other words, the heat transfer material 60 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 20 over heat emitted from "one or more low-heat-generating batteries" in the battery module 20, making it possible to achieve a more uniform heat distribution among the multiple batteries 30 when the battery pack 1 is in use compared to when the heat transfer material 60 is not provided.

[0062] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the compression ratio (thickness before compression / thickness after compression) of the peripheral portion 60Y is higher than that of the central portion 60X (thickness before compression / thickness after compression). As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the peripheral portion 60Y. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0063] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the void density Nb of the peripheral portion 60Y when compressed is lower than the void density Na of the central portion 60X when compressed. As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the peripheral portion 60Y. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0064] In this modified example, protrusions 12 are provided on the inner walls W1 and W2 of the outer case 10 (lower case 10a and upper case 10b) at locations facing the peripheral portion 60Y. As a result, the peripheral portion 60Y of the heat transfer material 60 is compressed by the protrusions 12, so that the thermal conductivity of the peripheral portion 60Y of the heat transfer material 60 becomes higher than that of the central portion 60X. Consequently, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be efficiently transferred (dissipated) to the outer case 10 via the heat transfer material 60. Therefore, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0065] In this modified example, the heat transfer material 60 may be in contact with the side plate portion 41 of the holder 40a or holder 40b, the tab 50a or tab 50b, and the end of each battery 30, for example, as shown in Figure 14. In this case, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be more efficiently transferred (dissipated) to the outer casing 10 via the heat transfer material 60. As a result, the temperature distribution of the multiple batteries 30 in the outer casing 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0066] (Extreme C) Figure 15 shows a modified example of the planar configuration of the battery pack 1 with the lower case 10a or upper case 10b removed. Figure 16 shows an example of the cross-sectional configuration of the battery pack 1 in Figure 15. In the first embodiment, the protrusions 12 may be omitted from the inner walls W1 and W2, and the inner walls W1 and W2 may be generally flat surfaces.

[0067] The heat transfer material 60 according to this modified example has a high-compression section 60c and a low-compression section 60d. The high-compression section 60c is provided in the central portion 60Z (described later) of the heat transfer material 60. The high-compression section 60c includes a plurality of high-compression voids 62c as a plurality of voids 62, as described later. The low-compression section 60d is provided in the peripheral portion 60W (described later) of the heat transfer material 60. The low-compression section 60d includes a plurality of low-compression voids 62b as a plurality of voids 62, as described later. The central portion 60Z corresponds to a specific example of the "first part" of one embodiment of this disclosure. The peripheral portion 60W corresponds to a specific example of the "second part" of one embodiment of this disclosure.

[0068] Next, the heat transfer material 60 related to this modified example will be described with reference to Figures 16, 17, and 18. Figure 17(A) shows an example of the cross-sectional configuration of the heat transfer material 60 before it is installed inside the outer case 10 (hereinafter referred to as the "pre-compression state"). Figure 17(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 17(A). Figure 18(A) shows an example of the cross-sectional configuration of the heat transfer material 60 after it has been installed inside the outer case 10 (hereinafter referred to as the "post-compression state"). Figure 18(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 18(A).

[0069] In its uncompressed state, the heat transfer material 60 is a sheet with protrusions 64 at predetermined locations, as shown in Figure 17(A). In the uncompressed state of the heat transfer material 60, the portion facing "one or more high-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the central portion 60Z. In the uncompressed state of the heat transfer material 60, the portion facing "one or more low-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the peripheral portion 60W.

[0070] The central portion 60Z is, for example, the area facing multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i), and is the area surrounded by the peripheral portion 60W, as shown in Figure 17(B). In the heat transfer material 60 before compression, the thickness of the central portion 60Z is Dz, and the thickness of the peripheral portion 60W is Dw. Also, in the heat transfer material 60 before compression, the void density of the central portion 60Z is Nz, and the void density of the peripheral portion 60W is Nw. The thickness Dz is greater than the thickness Dw. The void densities Nz and Nw are approximately equal to each other.

[0071] When the heat transfer material 60 is installed inside the outer case 10, it is compressed in the thickness direction by the side plate portion 41 and at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b). In the heat transfer material 60, the central portion 60Z including the protrusion 64 is compressed by the side plate portion 41 and at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2. As a result, in the central portion 60Z, for example, as shown in Figure 18(A), the protrusion 64 is crushed and disappears. This compresses the void 62 in the central portion 60Z, creating a flattened, highly compressed void 62c compressed in the thickness direction of the central portion 60Z. Consequently, the central portion 60Z becomes a highly compressed portion 60c. Let Dc be the thickness of the central portion 60Z, and let Nc be the void density of the central portion 60Z.

[0072] In the heat transfer material 60, the peripheral portion 60W is compressed by at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2, among the side plate portion 41 and tab 50a or tab 50b. As a result, the voids 62 within the peripheral portion 60W are slightly compressed, becoming slightly flattened, low-compression voids 62d that are slightly compressed in the thickness direction of the peripheral portion 60W. Consequently, the peripheral portion 60W becomes a low-compression portion 60d. Let Dd be the thickness of the peripheral portion 60W at this time, and let Nd be the void density of the peripheral portion 60W.

[0073] In the heat transfer material 60, the compression ratio of the central portion 60Z (thickness Dz before compression / thickness Dc after compression) is higher than that of the peripheral portion 60W (thickness Dw before compression / thickness Dd after compression). Also, in the compressed state of the heat transfer material 60, the void density Nc of the central portion 60Z is lower than that of the peripheral portion 60W. In the heat transfer material 60, the thermal conductivity of the central portion 60Z and the peripheral portion 60W changes before and after compression. In particular, the thermal conductivity of the central portion 60Z changes significantly before and after compression. In the compressed state of the heat transfer material 60, the thermal conductivity of the central portion 60Z is higher than that of the peripheral portion 60W. In other words, the heat transfer material 60 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 20 over heat emitted from "one or more low-heat-generating batteries" in the battery module 20, making it possible to achieve a more uniform heat distribution among the multiple batteries 30 when the battery pack 1 is in use compared to when the heat transfer material 60 is not provided.

[0074] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the compression ratio of the central portion 60Z (thickness Dz before compression / thickness Dc after compression) is higher than that of the peripheral portion 60W (thickness Dw before compression / thickness Dd after compression). As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the central portion 60Z. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0075] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the void density Nc of the central portion 60Z when compressed is lower than the void density Nd of the peripheral portion 60W when compressed. As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the central portion 60X. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0076] In this modified example, a protrusion 64 is provided in the central portion 60Z of the heat transfer material 60 before compression. As a result, when the heat transfer material 60 is placed between the side plate portion 41 and tab 50a or tab 50b and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b), the central portion 60Z including the protrusion 64 is compressed, so that the thermal conductivity of the central portion 60Z of the heat transfer material 60 becomes higher than that of the peripheral portion 60W. As a result, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be efficiently transferred (dissipated) to the outer case 10 via the heat transfer material 60. Therefore, the temperature distribution of the multiple batteries 30 in the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0077] (Variation D) Figure 19 shows one modified example of the cross-sectional configuration near the battery end faces in the battery pack 1. In modified example C, the heat transfer material 60 may be in contact with the side plate portion 41 of the holder 40a or holder 40b, the tab 50a or tab 50b, and the end of each battery 30, as shown in Figure 19. In this case, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be transmitted (dissipated) to the outer casing 10 more efficiently via the heat transfer material 60 than in modified example C. As a result, the temperature distribution of the multiple batteries 30 in the outer casing 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0078] (Variation E) Figure 20 shows a modified plan view of the battery pack 1 with the lower case 10a or upper case 10b removed. Figure 21 shows an example of the cross-sectional view of the battery pack 1 in Figure 20. In modified example C, the heat transfer material 60 may have a low-compression portion 60d in the central portion 60Z and a high-compression portion 60c in the peripheral portion 60W, for example, as shown in Figure 20. In this modified example, the central portion 60Z corresponds to a specific example of the "second part" of one embodiment of the present disclosure. The peripheral portion 60W corresponds to a specific example of the "first part" of one embodiment of the present disclosure.

[0079] In Figure 21, the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer correspond to one specific example of "one or more high-heat generating batteries." Two possible reasons why the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer correspond to high-heat generating batteries with relatively high temperatures in the heat distribution described above are as follows. It should be noted that there may also be other reasons besides the two below that cause the multiple batteries 30 (30a, 30e, 30f, 30j) at both ends of each layer to correspond to high-heat generating batteries with relatively high temperatures in the heat distribution described above.

[0080] • Cause #1 The current flowing through tab 50a or tab 50b causes localized high temperatures at the ends of tab 50a or tab 50b that face multiple batteries 30 (30a, 30e, 30f, 30j) at each layer. • Cause #2 The battery holder 40 is supported within the outer case 10 by protrusions that project toward the outer case 10, which are provided on the surface near the multiple batteries 30 (30b, 30c, 30d) in the center of the lowest layer of the battery holder 40, and the heat emitted from each battery 30 is transmitted (dissipated) to the outer case 10 through these protrusions.

[0081] Next, the heat transfer material 60 related to this modified example will be described with reference to Figures 21, 22, and 23. Figure 22(A) shows an example of the cross-sectional configuration of the heat transfer material 60 before it is installed inside the outer case 10 (hereinafter referred to as the "pre-compression state"). Figure 22(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 22(A). Figure 23(A) shows an example of the cross-sectional configuration of the heat transfer material 60 after it has been installed inside the outer case 10 (hereinafter referred to as the "post-compression state"). Figure 23(B) shows an example of the planar configuration of the heat transfer material 60 in Figure 23(A).

[0082] In its uncompressed state, the heat transfer material 60 is a sheet with protrusions 64 at predetermined locations, as shown in Figure 22(A). In the uncompressed state of the heat transfer material 60, the portion facing "one or more high-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the peripheral portion 60W. Also, in the uncompressed state of the heat transfer material 60, the portion facing "one or more low-heat generating batteries" when the heat transfer material 60 is installed inside the outer casing 10 is referred to as the central portion 60Z.

[0083] The central portion 60Z is, for example, the area facing multiple batteries 30 (30b, 30c, 30d, 30g, 30h, 30i), and is sandwiched between two peripheral portions 60W, as shown in Figure 22(B). In the heat transfer material 60 before compression, the thickness of the central portion 60Z is Dz, and the thickness of the peripheral portion 60W is Dw. Also, in the heat transfer material 60 before compression, the void density of the central portion 60Z is Nz, and the void density of the peripheral portion 60W is Nw. The thickness Dz is smaller than the thickness Dw. The void densities Nz and Nw are approximately equal to each other.

[0084] When the heat transfer material 60 is installed inside the outer case 10, it is compressed in the thickness direction by the side plate portion 41 and at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b). In the heat transfer material 60, the peripheral portion 60W including the protrusion 64 is compressed by the side plate portion 41 and at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2. As a result, in the peripheral portion 60W, for example, as shown in Figure 23(A), the protrusion 64 is crushed and disappears. This compresses the void 62 within the peripheral portion 60W, resulting in a flattened, highly compressed void 62c compressed in the thickness direction of the peripheral portion 60W. Consequently, the peripheral portion 60W becomes a highly compressed portion 60c. Let Dd be the thickness of the peripheral portion 60W at this time, and let Nd be the void density of the peripheral portion 60W.

[0085] In the heat transfer material 60, the central portion 60Z is compressed by at least tab 50a or tab 50b, and the inner wall W1 or inner wall W2, among the side plate portion 41 and tab 50a or tab 50b. As a result, the void 62 within the central portion 60Z is slightly compressed, becoming a slightly flattened, low-compression void 62d that is slightly compressed in the thickness direction of the central portion 60Z. Consequently, the central portion 60Z becomes a low-compression portion 60d. Let Dc be the thickness of the central portion 60Z at this time, and let Nc be the void density of the central portion 60Z.

[0086] In the heat transfer material 60, the compression ratio of the peripheral portion 60W (thickness Dw before compression / thickness Dd after compression) is higher than that of the central portion 60Z (thickness Dz before compression / thickness Dc after compression). Also, in the compressed state of the heat transfer material 60, the void density Nd of the peripheral portion 60W is lower than that of the central portion 60Z (void density Nc). In the heat transfer material 60, the thermal conductivity of the central portion 60Z and the peripheral portion 60W changes before and after compression. In particular, the thermal conductivity of the peripheral portion 60W changes significantly before and after compression. In the compressed state of the heat transfer material 60, the thermal conductivity of the peripheral portion 60W is higher than that of the central portion 60Z. In other words, the heat transfer material 60 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 20 over heat emitted from "one or more low-heat-generating batteries" in the battery module 20, making it possible to achieve a more uniform heat distribution among the multiple batteries 30 when the battery pack 1 is in use compared to when the heat transfer material 60 is not provided.

[0087] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the compression ratio of the peripheral portion 60W (thickness Dw before compression / thickness Dd after compression) is higher than that of the central portion 60Z (thickness Dz before compression / thickness Dc after compression). As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the peripheral portion 60W. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0088] In this modified example, in the heat transfer material 60, which is an elastic porous layer, the void density Nd of the peripheral portion 60W when compressed is lower than the void density Nc of the central portion 60Z when compressed. As a result, the path for conducting heat emitted from the multiple batteries 30 inside the outer case 10 to the outer case 10 is mainly provided in the peripheral portion 60W. Consequently, the temperature distribution of the multiple batteries 30 inside the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0089] In this modified example, a protrusion 64 is provided on the peripheral portion 60W of the heat transfer material 60 before compression. As a result, when the heat transfer material 60 is placed between the side plate portion 41 and tab 50a or tab 50b and the inner wall W1 or inner wall W2 of the outer case 10 (lower case 10a and upper case 10b), the peripheral portion 60W including the protrusion 64 is compressed, so that the thermal conductivity of the peripheral portion 60W of the heat transfer material 60 becomes higher than that of the central portion 60Z. As a result, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be efficiently transferred (dissipated) to the outer case 10 via the heat transfer material 60. Therefore, the temperature distribution of the multiple batteries 30 in the outer case 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0090] In this modified example, the heat transfer material 60 may be in contact with the side plate portion 41 of the holder 40a or holder 40b, the tab 50a or tab 50b, and the end of each battery 30, for example, as shown in Figure 24. In this case, the heat emitted from "one or more high-heat-generating batteries" in the battery module 20 can be more efficiently transferred (dissipated) to the outer casing 10 via the heat transfer material 60. As a result, the temperature distribution of the multiple batteries 30 in the outer casing 10 can be made more uniform compared to the case where the heat transfer material 60 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 30 can be reduced.

[0091] <3. Second Embodiment> Next, we will describe a battery pack 2 of a second embodiment of this technology.

[0092] The battery pack 2 described here is a power source equipped with multiple batteries and is applicable to a variety of uses, such as electronic devices. Details of the applications of battery pack 2 will be described later. The type of battery is not particularly limited and may be either a primary battery or a secondary battery. The type of secondary battery is not particularly limited, but specifically, it may be a lithium-ion secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium ions. The number of batteries is not particularly limited and can be set arbitrarily. The following description will focus on the case where the batteries are secondary batteries (lithium-ion secondary batteries). In other words, the battery pack 2 described below is a power source equipped with multiple secondary batteries.

[0093] [3-1. Structure] Figure 25 shows an example of a perspective view of the battery pack 2 according to the second embodiment of this technology. Figure 26 shows an example of a perspective view of a part of the contents of the battery pack 2. Figure 27 shows an example of a perspective view of the contents of the battery pack 2 in an unfolded state.

[0094] The battery pack 2 comprises, for example, an outer case 110 and a battery module 120 housed in the outer case 110, as shown in Figures 25 and 26. The battery pack 2 further comprises, for example, a tab 150, two heat transfer materials 160, and a control board 170, as shown in Figures 25, 26, and 27. The outer case 110 corresponds to one specific example of the "case" according to one embodiment of the present disclosure. The heat transfer materials 160 correspond to one specific example of the "fixing member" according to one embodiment of the present disclosure.

[0095] The outer casing 110 is composed of a lower case 110a and an upper case 110b, as shown in Figure 27, for example. The lower case 110a and the upper case 110b are stacked on top of each other to form a housing space for the battery module 120. The outer casing 110 is capable of housing the battery module 120. The outer casing 110 (for example, the lower case 110a) is provided with an external terminal 111 connected to a control board 170. Multiple batteries 130, described later, are connected to the external terminal 111 via the control board 170.

[0096] The outer casing 110 is made of a resin material such as polyethylene (PE), polypropylene (PP), polycarbonate (PC), modified polyphenylene ether (mPPE), polyamide (PA), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer resin (ABS), or polyacetal (POM). The outer casing 110 may also be made of a resin material in which a conductive material such as a metal or conductive filler is dispersed. In this case, the resin material may be one of the resin materials described above.

[0097] The battery pack 2 has a discharge mode in which it supplies power output from the battery module 120 to a load via the external terminal 111. The battery pack 2 may also have a charge mode in which it stores power supplied via the external terminal 111 from a power source connected to the external terminal 111 in the battery module 120. If the battery 130 is a secondary battery, the control board 170 switches between the discharge mode and the charge mode depending on the type of connected object connected to the external terminal 111. If the battery 130 is a primary battery, the control board 170 performs only the discharge mode. The control board 170 is in contact with the upper surface of the battery holder 140, for example. The control board 170 is fixed to the upper surface of the battery holder 140 by, for example, pressure fixing, screw fixing, adhesive fixing, or ultrasonic welding.

[0098] The battery module 120 includes a plurality of batteries 130 and a battery holder 140 capable of supporting the plurality of batteries 130. The battery holder 140 corresponds to a specific example of the "holder" according to one embodiment of the present disclosure. The plurality of batteries 130 are electrically connected to each other via tabs 150. The plurality of batteries 130 are connected in series to each other, for example, by tabs 150. However, the connection configuration of the plurality of batteries 30 is not limited to the above. For example, if a plurality of batteries 130 that are part of the plurality of batteries 130 are connected in series to each other by tabs 150, and further, the plurality of batteries 130 connected in series to each other are referred to as a series unit, the plurality of series units may be connected in parallel to each other by tabs 150.

[0099] Tab 150 is made of, for example, a metal lead plate. Each battery 130 is a rectangular laminate film type battery. Each battery 130 is either a primary or secondary battery. If each battery 130 is a secondary battery, the type of secondary battery is not particularly limited, but specifically, it could be a lithium-ion secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium ions. The following description will focus on the case where each battery 130 is a secondary battery (lithium-ion secondary battery). That is, the battery pack 2 described below is a power source equipped with multiple secondary batteries.

[0100] The battery 130 has a first end face S3 and a second end face S4 that face each other, as shown in Figure 28, for example. The battery 130 extends in a first direction in which the first end face S3 and the second end face S4 face each other. The tab 150 is positioned opposite the first end face S3 of each battery 130. In other words, the multiple batteries 130 are arranged so that the first end face S3 of each battery 130 faces a common direction (the direction of the tab 150).

[0101] The battery 130 has a positive electrode 131 and a negative electrode 132. The positive electrode 131 and the negative electrode 132 are provided on the first end face S3. The battery 130 has a plate shape in which the first end face S3 and the second end face S4 extend in a first direction facing each other, and the first end face S3 and the second end face S4 are each, for example, rectangular in shape. The positive electrode 131 and the negative electrode 132 are made of metal material. The positive electrode 131 and the negative electrode 132 have a shape that protrudes from the first end face S3.

[0102] Multiple batteries 130 are stacked in the thickness direction of the batteries 130. The thickness direction of the batteries 130 refers to the direction in which the top surface and the bottom surface of the batteries 130 face each other. The top surface of the batteries 130 refers to the top surface of the batteries 130 when the battery module 120 is housed in the outer case 110. The bottom surface of the batteries 130 refers to the bottom surface of the batteries 130 when the battery module 120 is housed in the outer case 110. The first end face S3 of each battery 130 provided in the battery pack 2 is arranged in a first plane, and the second end face S4 of each battery 130 provided in the battery pack 2 is arranged in a second plane. The tab 150 is in contact with multiple electrodes arranged in the first plane, either directly or via a conductive material such as solder.

[0103] The holder 140 is composed of a pair of holders 140a and 140b, as shown in Figures 26 and 27, for example. Both holders 140a and 140b have a common structure. Holder 140a is capable of accommodating the portion of each battery 130 that faces the first end face S3. Holder 140a is provided with an opening 141 at a location facing the positive electrode 131 and negative electrode 132 of the battery 130.

[0104] Holders 140a and 140b each have a side plate portion 142. The side plate portion 142 of holder 140a and the side plate portion 142 of holder 140b are positioned opposite each other in the extending direction (first direction) of each battery 130, with multiple batteries 130 in between. In holder 140a, the side plate portion 142 has an opening 141 at a location facing the positive electrode 131 and negative electrode 132 of each battery 130. Therefore, the positive electrode 131 and negative electrode 132 are exposed at the opening 141. The tab 150 is positioned close to the side plate portion 142 of holder 140a. The tab 150 contacts the positive electrode 131 and negative electrode 132 of each battery 130 directly or via a conductive material such as solder through the opening 141 of holder 140a.

[0105] Each holder 140a and 140b is capable of supporting multiple batteries 130 in a layered manner with predetermined gaps between them. Figure 26 illustrates how holders 140a and 140b support multiple batteries 130 stacked in the thickness direction of the batteries 130. Holders 140 (140a, 140b) are made of resin materials such as polyethylene (PE), polypropylene (PP), polycarbonate (PC), modified polyphenylene ether (mPPE), polyamide (PA), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer resin (ABS), and polyacetal (POM). The wall thickness of holders 140a and 140b is preferably within a range that allows for easy molding, for example, 0.5 mm to 5 mm.

[0106] Figure 29 shows a plan view example of the battery pack 2 with the lower case 110a or upper case 110b removed. Figure 30 shows a cross-sectional view example of the battery pack 2. Figure 30 illustrates how a holder 140 (holder 140a) is provided to support five batteries 130 in a stacked state. Figure 30 illustrates how the five batteries 130 (130a, 130b, 130c, 130d, 130e) are arranged in a row. In Figure 30, the three batteries 130 (130b, 130c, 130d) in the center of the arrangement direction correspond to a plurality of central batteries arranged in the center of the arrangement direction. In Figure 30, the two batteries 130 (130a, 130e) at both ends of the arrangement direction correspond to a plurality of peripheral batteries different from the plurality of central batteries arranged in the center of the arrangement direction.

[0107] Tab 150 and one of the heat transfer materials 160 are positioned between the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b) and the side plate portion 142 of the holder 140a. Inner wall W3 refers to the portion of the inner wall of the outer case 110 (lower case 110a and upper case 110b) that faces the side plate portion 142 of the holder 140a. Tab 150 is positioned between the side plate portion 142 of the holder 140a and the heat transfer material 160. Heat transfer material 160 is positioned between the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b) and the tab 150. Heat transfer material 160 is in contact with the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b) and the tab 150. The heat transfer material 160 is compressed by the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b) and the side plate portion 142 and tab 150 of the holder 140a. If the tab 150 is formed in a planar shape, the heat transfer material 160 is compressed by the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b) and the tab 150.

[0108] The other heat transfer material 160 is positioned between the inner wall W4 of the outer case 110 (lower case 110a and upper case 110b) and the side plate portion 142 of the holder 140b. The inner wall W4 refers to the portion of the inner wall of the outer case 110 (lower case 110a and upper case 110b) that faces the side plate portion 142 of the holder 140b. The heat transfer material 160 is in contact with the inner wall W4 of the outer case 110 (lower case 110a and upper case 110b) and the side plate portion 142 of the holder 140b. The heat transfer material 160 is compressed by the inner wall W4 of the outer case 110 (lower case 110a and upper case 110b) and the side plate portion 142 of the holder 140b.

[0109] Each of the inner walls W3 and W4 has a protrusion 112 at a location facing the central portion 160X (described later) of the heat transfer material 160. The protrusion 112 is provided at a location facing one or more high-heat generating batteries that are relatively hotter in the heat distribution of the multiple batteries 130 when the battery pack 2 is in use (during charging or discharging) in a state where the heat transfer material 160 is not provided and there is an air gap G between the outer case 110 and the holder 140.

[0110] Of the inner walls W3 and W4, the areas where the protrusions 112 are not formed are surfaces that are lower in height than the protrusions 112, and are the base of the protrusions 112 or flat surfaces. Of the inner walls W3 and W4, the areas where the protrusions 112 are not formed are mainly located in areas where the heat transfer material 160 is not provided and where there is an air gap G between the outer case 110 and the holder 140, and the heat distribution of the multiple batteries 130 during use (charging or discharging) is in a location that faces one or more low-heat generating batteries that are relatively lower in temperature.

[0111] In Figure 30, the multiple batteries 130 (130b, 130c, 130d) in the center of the array direction correspond to one specific example of "one or more high-heat generating batteries." The reason why the multiple batteries 130 (130b, 130c, 130d) in the center of the array direction correspond to high-heat generating batteries with relatively higher temperatures in the above heat distribution is that the heat emitted from each battery 130 tends to accumulate in the central part of the array direction.

[0112] The heat transfer material 160 has a high-compression section 160a and a low-compression section 160b. The high-compression section 160a is provided in the central portion 160X (described later) of the heat transfer material 160. The high-compression section 160a includes multiple high-compression voids 162a as multiple voids 162, as described later. The low-compression section 160b is provided in the peripheral portion 160Y (described later) of the heat transfer material 160. The low-compression section 160b includes multiple low-compression voids 162b as multiple voids 162, as described later.

[0113] Next, the heat transfer material 160 will be described with reference to Figures 30, 31, and 32. Figure 31(A) shows an example of the cross-sectional configuration of the heat transfer material 160 before it is installed inside the outer case 110 (hereinafter referred to as the "pre-compression state"). Figure 31(B) shows an example of the planar configuration of the heat transfer material 160 in Figure 31(A). Figure 32(A) shows an example of the cross-sectional configuration of the heat transfer material 160 after it has been installed inside the outer case 110 (hereinafter referred to as the "post-compression state"). Figure 32(B) shows an example of the planar configuration of the heat transfer material 160 in Figure 32(A).

[0114] The heat transfer material 160 supports the battery module 120 within the battery holder 140, either directly or via the tab 150. The heat transfer material 160 also serves as a heat conduction path that transmits (dissipates) heat generated from the multiple batteries 130 within the battery holder 140 to the outer casing 110. The heat transfer material 160 is composed of a resin member 161 with a higher thermal conductivity than gases such as air or nitrogen. The resin member 161 is an elastic porous layer and contains numerous voids 162. In the resin member 161, the numerous voids 162 may be connected to each other or provided independently of each other. The voids 162 are filled with gases such as air or nitrogen. The resin member 161 is composed of, for example, urethane foam, polyethylene foam, EVA foam, or rubber sponge.

[0115] In its uncompressed state, the heat transfer material 160 is in the form of a sheet with a thickness that is approximately uniform regardless of location, as shown in Figure 31(A), for example. In the uncompressed state of the heat transfer material 160, the portion facing "one or more high-heat generating batteries" when the heat transfer material 160 is installed inside the outer casing 110 is referred to as the central portion 160X. Also, in the uncompressed state of the heat transfer material 160, the portion facing "one or more low-heat generating batteries" when the heat transfer material 160 is installed inside the outer casing 110 is referred to as the peripheral portion 160Y.

[0116] The central portion 160X is, for example, the area facing multiple batteries 130 (130b, 130c, 130d), and is the area surrounded by the peripheral portion 160Y, as shown in Figure 31(B). The central portion 160X corresponds to one specific example of the "first part" of one embodiment of the present disclosure. The peripheral portion 160Y corresponds to one specific example of the "second part" of one embodiment of the present disclosure. In the heat transfer material 160 in its pre-compression state, the thickness of the central portion 160X is Dx, and the thickness of the peripheral portion 160Y is Dy. Also, in the heat transfer material 160 in its pre-compression state, the void density of the central portion 160X is Nx, and the void density of the peripheral portion 160Y is Ny. The thicknesses Dx and Dy are approximately equal to each other. The void densities Nx and Ny are approximately equal to each other.

[0117] When the heat transfer material 160 positioned on the holder 140a side is installed inside the outer case 110, it is compressed in the thickness direction by at least the tab 150 of the side plate portion 142 and the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b). In the heat transfer material 160 positioned on the holder 140a side, the central portion 160X is compressed by at least the tab 150 of the side plate portion 142 and the convex portion 112. As a result, a recess 163 corresponding to the shape of the convex portion 112 is formed in the central portion 160X, for example, as shown in Figure 32(A). As a result, the void 162 in the central portion 160X is compressed, becoming a flattened, highly compressed void 162a compressed in the thickness direction of the central portion 160X. Consequently, the central portion 160X becomes a highly compressed portion 160a. Let Da be the thickness of the central portion 160X, and let Na be the void density of the central portion 160X.

[0118] When the heat transfer material 160 positioned on the holder 140b side is installed inside the outer case 110, it is compressed in the thickness direction by the side plate portion 142 and the inner wall W4 of the outer case 110 (lower case 110a and upper case 110b). In the heat transfer material 160 positioned on the holder 140b side, the central portion 160X is compressed by the side plate portion 142 and the convex portion 112. As a result, a recess 163 corresponding to the shape of the convex portion 112 is formed in the central portion 160X, for example, as shown in Figure 32(A). As a result, the void 162 in the central portion 160X is compressed, becoming a flattened, highly compressed void 162a compressed in the thickness direction of the central portion 160X. Consequently, the central portion 160X becomes a highly compressed portion 160a. Let Da be the thickness of the central portion 160X at this time, and Na be the void density of the central portion 160X.

[0119] In the heat transfer material 160 positioned on the holder 140a side, the peripheral portion 160Y is compressed by at least the tab 150 of the side plate portion 142 and the portion of the inner wall W3 where the protrusion 112 has not yet been formed. As a result, the peripheral portion 160Y forms a shape corresponding to the portion of the inner wall W3 where the protrusion 112 has not yet been formed, as shown in Figure 32(A), for example. As a result, the void 162 within the peripheral portion 160Y is slightly compressed, becoming a slightly flattened, low-compression void 162b that is slightly compressed in the thickness direction of the peripheral portion 160Y. ​​Consequently, the peripheral portion 160Y becomes a low-compression portion 160b. Let Db be the thickness of the peripheral portion 160Y at this time, and let Nb be the void density of the peripheral portion 160Y.

[0120] In the heat transfer material 160 positioned on the holder 140b side, the peripheral portion 160Y is compressed by the side plate portion 142 and the unformed portion of the inner wall W3 where the protrusion 112 is located. As a result, a shape corresponding to the unformed portion of the inner wall W4 where the protrusion 112 is located is formed in the peripheral portion 160Y, for example, as shown in Figure 32(A). Consequently, the void 162 within the peripheral portion 160Y is slightly compressed, resulting in a slightly flattened, low-compression void 162b that is slightly compressed in the thickness direction of the peripheral portion 160Y. ​​As a result, the peripheral portion 160Y becomes a low-compression portion 160b. Let Db be the thickness of the peripheral portion 160Y at this time, and let Nb be the void density of the peripheral portion 160Y.

[0121] In the heat transfer material 160, the compression ratio of the central portion 160X (thickness Dx before compression / thickness Da after compression) is higher than that of the peripheral portion 160Y (thickness Dy before compression / thickness Db after compression). Also, in the compressed state of the heat transfer material 160, the void density Na of the central portion 160X is lower than that of the peripheral portion 160Y (void density Nb). In the heat transfer material 160, the thermal conductivity of the central portion 160X and the peripheral portion 160Y changes before and after compression. In particular, the thermal conductivity of the central portion 160X changes significantly before and after compression. In the compressed state of the heat transfer material 160, the thermal conductivity of the central portion 160X is higher than that of the peripheral portion 160Y. In other words, the heat transfer material 160 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 120 over heat emitted from "one or more low-heat-generating batteries" in the battery module 120, making the heat distribution of the multiple batteries 130 during use of the battery pack 2 more uniform compared to when the heat transfer material 160 is not provided.

[0122] [3-2. Effects] Next, I will explain the effects of battery pack 2.

[0123] In this embodiment, in the heat transfer material 160, which is an elastic porous layer, the compression ratio (thickness before compression / thickness after compression) of the central portion 160X is higher than that of the peripheral portion 160Y (thickness before compression / thickness after compression). As a result, the path for conducting heat emitted from the multiple batteries 130 inside the outer case 110 to the outer case 110 is mainly provided in the central portion 160X. Consequently, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0124] In this embodiment, in the heat transfer material 160, which is an elastic porous layer, the void density Na of the central portion 160X when compressed is lower than the void density Nb of the peripheral portion 160Y when compressed. As a result, the path for conducting heat emitted from the multiple batteries 130 inside the outer case 110 to the outer case 110 is mainly provided in the central portion 160X. Consequently, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0125] In this embodiment, the heat transfer material 160 positioned on the holder 140a side is in contact with at least the tab 150 of the side plate portion 142 and tab 150 of the holder 140a or holder 140b. This allows heat generated from "one or more high-heat-generating batteries" in the battery module 120 to be efficiently transferred (dissipated) to the outer casing 110 via the heat transfer material 160. As a result, the temperature distribution of the multiple batteries 130 in the outer casing 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0126] In this embodiment, the inner walls W3 and W4 of the outer case 110 (lower case 110a and upper case 110b) are provided with protrusions 112 at locations facing the central portion 160X. As a result, the central portion 160X of the heat transfer material 160 is compressed by the protrusions 112, so that the thermal conductivity of the central portion 160X of the heat transfer material 160 becomes higher than that of the peripheral portion 160Y. ​​Consequently, the heat emitted from "one or more high-heat-generating batteries" in the battery module 120 can be efficiently transferred (dissipated) to the outer case 110 via the heat transfer material 160. Therefore, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0127] <4. Modified form of the second embodiment> Next, a modified example of the battery pack 2 according to the second embodiment will be described.

[0128] Figure 33 shows a modified example of the planar configuration of the battery pack 2 with the lower case 110a or upper case 110b removed. Figure 34 shows an example of the cross-sectional configuration of the battery pack 2 in Figure 33. In the second embodiment, the inner walls W3 and W4 may each have a protrusion 112 at a location facing the peripheral portion 160Y of the heat transfer material 160, rather than the central portion 160X of the heat transfer material 160, as shown in Figure 33. The locations of the inner walls W3 and W4 where the protrusion 112 is not formed are each provided at a location facing the central portion 160X of the heat transfer material 160, rather than the peripheral portion 160Y of the heat transfer material 160, as shown in Figure 33.

[0129] The protrusion 112 is provided at a location facing "one or more high-heat-generating batteries". In this modified example, the multiple batteries 130 (130a, 130e) at both ends correspond to one specific example of "one or more high-heat-generating batteries". Of the inner walls W3, W4, the areas where the protrusion 112 is not formed are provided at locations facing "one or more low-heat-generating batteries". In this modified example, the multiple batteries 130 (130b, 130c, 130d) in the center correspond to one specific example of "one or more low-heat-generating batteries".

[0130] In Figure 34, the multiple batteries 130 (130a, 130e) at both ends in the direction of arrangement correspond to one specific example of "one or more high-heat generating batteries." Two possible reasons why the multiple batteries 130 (130a, 130e) at both ends in the direction of arrangement correspond to high-heat generating batteries with relatively high temperatures in the heat distribution described above are as follows. It should be noted that there may also be other reasons besides the two below that cause the multiple batteries 130 (130a, 130e) at both ends in the direction of arrangement to correspond to high-heat generating batteries with relatively high temperatures in the heat distribution described above.

[0131] • Cause #1 The current flowing through tab 150 causes localized high temperatures at the ends of tab 150 facing multiple batteries 130 (130a, 130e) in the arrangement direction. • Cause #2 The battery holder 140 is supported within the outer case 110 by protrusions that project toward the outer case 110, which are provided on the surface near the central multiple batteries 130 (130b, 130c, 130d) in the arrangement direction of the battery holder 140, and the heat emitted from each battery 130 is transmitted (dissipated) to the outer case 110 via these protrusions.

[0132] Next, the heat transfer material 160 related to this modified example will be described with reference to Figures 34, 35, and 36. Figure 35(A) shows an example of the cross-sectional configuration of the heat transfer material 160 before it is installed inside the outer case 110 (hereinafter referred to as the "pre-compression state"). Figure 35(B) shows an example of the planar configuration of the heat transfer material 160 in Figure 35(A). Figure 36(A) shows an example of the cross-sectional configuration of the heat transfer material 160 after it has been installed inside the outer case 110 (hereinafter referred to as the "post-compression state"). Figure 36(B) shows an example of the planar configuration of the heat transfer material 160 in Figure 35(A).

[0133] In its uncompressed state, the heat transfer material 160 is in the form of a sheet with a thickness that is approximately uniform regardless of location, as shown in Figure 35(A), for example. In the uncompressed state of the heat transfer material 160, the portion facing "one or more high-heat generating batteries" when the heat transfer material 160 is installed inside the outer casing 110 is referred to as the peripheral portion 60Y. Also, in the uncompressed state of the heat transfer material 160, the portion facing "one or more low-heat generating batteries" when the heat transfer material 160 is installed inside the outer casing 110 is referred to as the central portion 160X.

[0134] The central portion 160X is, for example, the area facing multiple batteries 130 (130b, 130c, 130d), and is the area sandwiched between two peripheral portions 160Y, as shown in Figure 35(B). In the heat transfer material 160 before compression, the thickness of the central portion 160X is Dx, and the thickness of the peripheral portion 160Y is Dy. Also, in the heat transfer material 160 before compression, the void density of the central portion 160X is Nx, and the void density of the peripheral portion 160Y is Ny. The thicknesses Dx and Dy are approximately equal to each other. The void densities Nx and Ny are approximately equal to each other.

[0135] When the heat transfer material 160 positioned on the holder 140a side is installed inside the outer case 110, it is compressed in the thickness direction by at least the tab 150 of the side plate portion 142 and the inner wall W3 of the outer case 110 (lower case 110a and upper case 110b). In the heat transfer material 160 positioned on the holder 140a side, the peripheral portion 160Y is compressed by at least the tab 150 of the side plate portion 142 and the convex portion 112. As a result, a recess 163 corresponding to the shape of the convex portion 112 is formed in the peripheral portion 160Y, for example, as shown in Figure 36(A). Consequently, the void 162 within the peripheral portion 160Y is compressed, becoming a flattened, highly compressed void 162a compressed in the thickness direction of the peripheral portion 160Y. Let Db be the thickness of the peripheral portion 160Y at this time, and let Nb be the void density of the peripheral portion 160Y.

[0136] In the heat transfer material 160, the central portion 160X is compressed by at least the tab 150 among the side plate portions 142 and tab 150, and by the unformed portions of the inner wall W3 where the protrusions 112 are located. As a result, the central portion 160X forms a shape corresponding to the unformed portions of the inner wall W3 where the protrusions 112 are located, as shown in Figure 36(A), for example. Consequently, the voids 162 within the central portion 160X are slightly compressed, resulting in slightly flattened, low-compression voids 162b that are slightly compressed in the thickness direction of the central portion 160X. Let Da be the thickness of the central portion 160X at this time, and Na be the void density of the central portion 160X.

[0137] In the heat transfer material 160, the compression ratio of the peripheral portion 160Y (thickness Dy before compression / thickness Db after compression) is higher than that of the central portion 160X (thickness Dx before compression / thickness Da after compression). Also, in the compressed state of the heat transfer material 160, the void density Nb of the peripheral portion 160Y is lower than that of the central portion 160X (void density Na). In the heat transfer material 160, the thermal conductivity of the central portion 160X and the peripheral portion 160Y changes before and after compression. In particular, the thermal conductivity of the peripheral portion 160Y changes significantly before and after compression. In the compressed state of the heat transfer material 160, the thermal conductivity of the peripheral portion 160Y is higher than that of the central portion 160X. In other words, the heat transfer material 160 prioritizes the dissipation of heat emitted from "one or more high-heat-generating batteries" in the battery module 120 over heat emitted from "one or more low-heat-generating batteries" in the battery module 120, making the heat distribution of the multiple batteries 130 during use of the battery pack 2 more uniform compared to when the heat transfer material 160 is not provided.

[0138] In this modified example, in the heat transfer material 160, which is an elastic porous layer, the compression ratio (thickness before compression / thickness after compression) of the peripheral portion 160Y is higher than that of the central portion 160X (thickness before compression / thickness after compression). As a result, the path for conducting heat emitted from the multiple batteries 130 inside the outer case 110 to the outer case 110 is mainly provided in the peripheral portion 160Y. ​​Consequently, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0139] In this modified example, in the heat transfer material 160, which is an elastic porous layer, the void density Nb of the peripheral portion 160Y when compressed is lower than the void density Na of the central portion 160X when compressed. As a result, the path for conducting heat emitted from the multiple batteries 130 inside the outer case 110 to the outer case 110 is mainly provided in the peripheral portion 160Y. ​​Consequently, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. Therefore, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0140] In this modified example, protrusions 112 are provided on the inner walls W3 and W4 of the outer case 110 (lower case 110a and upper case 110b) at locations facing the peripheral portion 160Y. ​​As a result, the peripheral portion 160Y of the heat transfer material 160 is compressed by the protrusions 112, so that the thermal conductivity of the peripheral portion 160Y of the heat transfer material 160 becomes higher than that of the central portion 160X. Consequently, the heat emitted from "one or more high-heat-generating batteries" in the battery module 120 can be efficiently transferred (dissipated) to the outer case 110 via the heat transfer material 160. Therefore, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. From the above, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0141] In the second embodiment described above, the protrusion 112 may be omitted, and the heat transfer material 160 described in Figures 15, 17(A), (B), and 17(A), (B) may be used. Also, in a modified example of the second embodiment described above, the protrusion 112 may be omitted, and the heat transfer material 160 described in Figures 20, 22(A), (B), and 23(A), (B) may be used. Even in this case, similar to the second embodiment described above and the modified example of the second embodiment described above, the temperature distribution of the multiple batteries 130 inside the outer case 110 can be made more uniform compared to the case where the heat transfer material 160 is not provided. As a result, the possibility of variations in the characteristics and lifespan of each battery 130 can be reduced.

[0142] Although the present technology has been described above with reference to several embodiments and their variations, the present technology is not limited to the embodiments described above, and various modifications are possible. Furthermore, the effects described herein are merely illustrative, and the effects of the present technology are not limited to those described herein. Therefore, other effects may be obtained with respect to the present technology. [Explanation of symbols]

[0143] 1,2…Battery pack, 10,110…Outer case, 10a,110a…Lower case, 10b,110b…Upper case, 11,111…External terminal, 12…Protrusion, 20,120…Battery module, 30,130…Battery, 31,131…Positive electrode, 32,132…Negative electrode, 40,140…Battery holder, 40a,40b,140a,140b…Holder, 41,141…Side plate, 42…Opening, 43…Support part, 44…Opening, 45…Housing part, 50a,50b,150…Tab, 60,160… Heat transfer material, 60a, 60c, 160a... High compression section, 60b, 60d, 160b... Low compression section, 60X, 60Z, 160X... Central section, 60Y, 60W, 160Y... Peripheral section, 61, 161... Resin component, 62, 162... Void, 62a, 162a... High compression void, 62b, 162b... Low compression void, 63, 163... Recess, 64... Protrusion, 70, 170... Control board, Da, Db, Dw, Dx, Dy, Dz... Thickness, G... Void, S1... First end face, S2... Second end face, W1, W2, W3, W4... Inner wall.

Claims

1. Multiple batteries, A holder capable of supporting the plurality of batteries in one or more layers, A case capable of housing the aforementioned plurality of batteries and the aforementioned holders, A fixing member is disposed between at least one of the end faces of each of the batteries and the inner wall of the case. A battery pack equipped with, The fixing member is an elastic porous layer, In the aforementioned fixing member, the compression ratio (thickness before compression / thickness after compression) of the first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the plurality of batteries when the battery pack is in use, is higher than the compression ratio (thickness before compression / thickness after compression) of the second portion facing one or more low-heat-generating batteries, which have relatively lower temperatures in the heat distribution. Battery pack.

2. Multiple batteries, A holder capable of supporting the plurality of batteries in one or more layers, A case capable of housing the aforementioned plurality of batteries and the aforementioned holders, A fixing member is disposed between at least one of the end faces of each of the batteries and the inner wall of the case. A battery pack equipped with, The fixing member is an elastic porous layer, In the aforementioned fixing member, the void density of the first portion facing one or more high-heat-generating batteries, which have relatively higher temperatures in the heat distribution of the plurality of batteries when the battery pack is in use, is lower than the void density of the second portion facing one or more low-heat-generating batteries, which have relatively lower temperatures in the heat distribution. Battery pack.

3. The first part is a central part of the plurality of batteries that is opposite to one or more central batteries located in the center of each of the layers, The second part is a peripheral portion of the plurality of batteries that faces a plurality of peripheral batteries that are different from the one or more central batteries. The battery pack according to claim 1 or claim 2.

4. The first part is a peripheral portion of the plurality of batteries that is different from the central portion that faces the one or more central batteries located in the center of each of the layers, and that faces a plurality of peripheral batteries. The second part is the central part. The battery pack according to claim 1 or claim 2.

5. The case further comprises a tab positioned between at least one of the end faces of each of the batteries and the inner wall of the case, which is capable of electrically connecting the plurality of batteries. The fixing member is in contact with at least the tab among the tab, the plurality of batteries, and the holder. The battery pack according to any one of claims 1 to 4.

6. The fixing member is in contact with the tab, the plurality of batteries, and the holder. The battery pack according to claim 5.

7. The inner wall of the case has a protrusion at a location facing the first portion of the fixing member. The battery pack according to any one of claims 1 to 6.

8. The fixing member has a protrusion on its first portion when it is removed from the battery pack. The battery pack according to any one of claims 1 to 6.

9. The fixing member is made of urethane foam, polyethylene foam, EVA foam, or rubber sponge. The battery pack according to any one of claims 1 to 8.

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