Battery pack

Abstract

To improve a discharge characteristic under a low temperature environment.SOLUTION: A battery pack 10 disclosed, comprises: the n of cell unit 20 (n is three or more integer numbers); and a heat insulation material 30 arranged so as to surround the n of cell units 20 respectively one by one. The n of cell units 20 is arranged so that all of the number of adjacent cell units 20 does not become the same. A thermal resistance value of the heat insulation material 30 corresponding to each cell unit 20 is smaller as being larger the number of adjacent cell units 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a battery pack. [Background technology]

[0002] Conventionally, there is known a battery pack (or battery pack) that comprises multiple batteries and spacers provided between adjacent batteries (for example, Patent Document 1). In the battery pack of Patent Document 1, the spacers between the batteries in the center are thicker than the spacers between the batteries at the ends. In other words, the latter have a greater thermal resistance than the former. This is said to reduce the temperature difference within the battery pack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4641737 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the battery pack in Patent Document 1 has a small thermal resistance value for the spacers between the batteries at the ends. Therefore, when the battery pack is used in a low-temperature environment, the temperature of the batteries at the ends may become too low, making it difficult to discharge a large current. In this situation, one of the objectives of the present disclosure is to improve the discharge characteristics in a low-temperature environment. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a battery pack, comprising n cell units (n is an integer of 3 or more) and insulating materials arranged to surround each of the n cell units, the n cell units being arranged such that the number of adjacent cell units is not all the same, and the thermal resistance value of the insulating material corresponding to each cell unit is smaller as the number of adjacent cell units increases. Effect of the Invention

[0006] According to the present disclosure, it is possible to improve the discharge characteristics in a low-temperature environment. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view illustrating a battery pack according to a first embodiment. [Diagram 2] FIG. 11 is a plan view illustrating a battery pack according to a second embodiment. [Diagram 3] FIG. 11 is a plan view illustrating a battery pack according to a third embodiment. [Figure 4] FIG. 11 is a plan view illustrating a battery pack according to a fourth embodiment. [Diagram 5] FIG. 13 is a plan view illustrating a battery pack according to a modified example of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An embodiment of a battery pack according to the present disclosure will be described below with reference to an example. However, the present disclosure is not limited to the example described below. In the following description, specific values ​​and materials may be exemplified, but other values ​​and materials may be applied as long as the effects of the present disclosure are obtained.

[0009] A battery pack according to the present disclosure includes n cell units (n is an integer of 3 or more) and a thermal insulator corresponding to each cell unit.

[0010] Each of the n cell units may be composed of a single cell or multiple cells. The shape of the cells constituting each cell unit can be set arbitrarily, and may be, for example, cylindrical or rectangular. The n cell units are arranged so that the number of adjacent cell units is not all the same. In other words, the n cell units are arranged so that at least one is adjacent to s cell units (s is an integer of 1 or more) and at least another is adjacent to t cell units (t is an integer of 1 or more different from s). Note that both s and t are smaller than n.

[0011] Here, in this specification, "adjacent" refers to a positional relationship between any pair of cell units in which the insulating materials corresponding to each cell unit are adjacent to each other with no gaps at least in part. The positional relationship may be a positional relationship in which the insulating materials corresponding to each cell unit are in contact with each other. Furthermore, a sheet material may be interposed between the insulating materials corresponding to each cell unit so as to be in contact with each insulating material.

[0012] The heat insulating materials are arranged so as to surround each of the n cell units. The heat insulating materials may be provided one by one for each cell unit, or multiple heat insulating materials may be provided for each cell unit, or a combination of these may be used. At least n heat insulating materials are provided. The heat insulating materials may be provided on the side surfaces of the corresponding cell units.

[0013] The thermal resistance value of the insulation material corresponding to each cell unit is smaller as the number of adjacent cell units (hereinafter also referred to as the "number of adjacent units") increases. For example, if a cell unit is adjacent to one cell unit and another cell unit is adjacent to two cell units, the thermal resistance value of the insulation material corresponding to the latter cell unit will be smaller than the thermal resistance value of the insulation material corresponding to the former cell unit. The thermal resistance value of an insulation material is expressed as d / λ[m where the thermal conductivity of the insulation material is λ[W / (m K)] and the thickness of the insulation material is d[m]. 2 ·K / W].

[0014] By providing insulation around each cell unit, the heat generated by the cell unit itself is stored during discharge in a low-temperature environment, raising the temperature of the cell unit, improving the discharge characteristics in low-temperature environments.

[0015] In addition, cell units with a large number of adjacent units have a higher temperature than cell units with a small number of adjacent units because they have a harder time dissipating heat. In other words, temperature variations are likely to occur between cell units with a large number of adjacent units and cell units with a small number of adjacent units. If this temperature variation is large, the life of the battery pack will be shortened.

[0016] In contrast, in the battery pack of the present disclosure, the thermal resistance value of the insulating material of a cell unit with a large number of adjacent units is smaller than the thermal resistance value of the insulating material of a cell unit with a small number of adjacent units. Therefore, a cell unit with a large number of adjacent units, which is likely to become hot, is more likely to dissipate heat to the surrounding cell units. The temperature rise of the cell unit with a large number of adjacent units is suppressed, and the temperature variation within the battery pack is reduced. This makes it possible to extend the life of the battery pack.

[0017] As described above, according to the present disclosure, it is possible to improve the discharge characteristics in a low-temperature environment in a battery pack including a plurality of cell units, and further to extend the life of such a battery pack.

[0018] The thermal resistance values ​​of the insulating materials corresponding to cell units having the same number of adjacent units may be the same. However, it is difficult to make the thermal conductivity and thickness of multiple insulating materials strictly equal. Therefore, in this specification, even if there is an error of about ±5% in the thermal resistance values ​​of multiple insulating materials, they are considered to be the same. For example, when the thermal resistance values ​​of one and the other insulating materials are A and B (A>B), respectively, if the ratio of (AB) to A is 5% or less, the thermal resistance values ​​are considered to be the same. Note that the thermal resistance values ​​of the insulating materials corresponding to cell units having the same number of adjacent units may be different.

[0019] The thermal resistance of the insulation is 0.005m 2 ·K / W or more and 0.057m 2 By setting the thermal resistance value of the insulating material in this range, the discharge characteristics of the battery pack in a low-temperature environment can be further improved, and excessive temperature rise of the battery pack can be easily suppressed. The thermal resistance value of the insulating material is preferably 0.006 m 2 K / W or more and 0.056m 2 ·K / W or less is acceptable.

[0020] The battery pack may further include a thermally conductive sheet provided in contact with each cell unit. Such a thermally conductive sheet promotes thermal conduction between the cell units, thereby reducing temperature variation within the battery pack. This allows the battery pack to have a longer life. The thermal conductivity of the thermally conductive sheet is higher than that of the insulating material, and may be, for example, 1.0 W / (m·K) or more.

[0021] The thermally conductive sheet may be provided on at least one of the one end side and the other end side of the cell unit, or may be provided on both sides. In the latter case, the thermal conduction between the cell units is more promoted than when the thermally conductive sheet is provided only on one end side of the cell unit. Therefore, the temperature variation in the battery pack can be further reduced, and the life of the battery pack can be further extended. The one end side and the other end side of the cell unit usually correspond to one and the other end faces, not to the side faces of the cells constituting the cell unit. Such end faces may correspond to the opening and the bottom of the cell case. A terminal member may be connected to the end face. The thermally conductive sheet may be in direct contact with the cell, or may be in contact with the terminal member.

[0022] The cell unit may include one to four cells. The cell unit may include five or more cells. The cell unit may be composed of at least one cylindrical cell. The cell includes, for example, a cylindrical cell case with a bottom, an electrode group housed in the cell case, and an electrolyte. The cell may be, but is not limited to, a primary battery, a secondary battery, a capacitor, a lithium ion capacitor, or the like. The secondary battery may be an alkaline storage battery (or a nickel-metal hydride storage battery), a non-aqueous electrolyte secondary battery, or the like.

[0023] An example of a battery pack according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the battery pack of the example described below. The components of the battery pack of the example described below can be modified based on the above description. The matters described below may also be applied to the above embodiment. Among the components of the battery pack of the example described below, components that are not essential to the battery pack according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual members.

[0024] First Embodiment As shown in FIG. 1, the battery pack 10 of the first embodiment includes three cell units 20 and a thermal insulator 30 corresponding to each cell unit 20.

[0025] Each cell unit 20 is composed of one cylindrical cell (cylindrical cell) 21. The central axis of the cell 21 extends in a direction perpendicular to the plane of the paper in FIG. 1. The cell 21 may be any type of primary or secondary battery. The cell 21 in this embodiment is a nickel-metal hydride storage battery.

[0026] The three cell units 20 are arranged so that the number of adjacent cell units 20 (number of adjacent units) are not all the same. Specifically, the three cell units 20 are arranged in a straight line. The cell unit 20 in the middle has two adjacent units. The two cell units 20 at both ends have one adjacent unit. Note that in each figure, the insulation material 30 corresponding to the cell units 20 with the same number of adjacent units is hatched with the same type of pattern.

[0027] The heat insulating materials 30 are arranged so as to surround each of the three cell units 20. In this embodiment, three heat insulating materials 30 are provided, one for each cell unit 20. Note that multiple heat insulating materials 30 may be provided for each cell unit 20.

[0028] The thermal resistance value of the insulating material 30 corresponding to each cell unit 20 decreases as the number of adjacent units increases. Specifically, the thermal resistance value of the insulating material 30 corresponding to the central cell unit 20 (i.e., the cell unit 20 with two adjacent units) is smaller than the thermal resistance value of the insulating material 30 corresponding to the cell units 20 on both ends (i.e., the cell unit 20 with one adjacent unit). In this embodiment, the former value is 0.006 m 2 ·K / W, the latter value is 0.028m 2 -K / W.

[0029] Such a difference in thermal resistance value is realized by a difference in the constituent material of the insulating material 30. In this embodiment, the insulating material 30 corresponding to the central cell unit 20 is made of polyvinyl chloride (PVC) (thermal conductivity: 0.170 W / (m·K)). The insulating materials 30 corresponding to the cell units 20 at both ends are made of glass wool insulating material (thermal conductivity: 0.036 W / (m·K)). The thickness of each insulating material 30 is 1.0 mm. Such a thin insulating material 30 can also be called an insulating sheet. The difference in thermal resistance value of the insulating material 30 may be realized by a difference in the thickness of the insulating material 30, or may be realized by a combination of a difference in thickness and a difference in the constituent material.

[0030] Second Embodiment A second embodiment will be described. The battery pack 10 of this embodiment differs from the first embodiment in the number of cell units 20. The following mainly describes the differences from the first embodiment.

[0031] As shown in FIG. 2, the battery pack 10 of the second embodiment includes four cell units 20 and a thermal insulator 30 corresponding to each cell unit 20.

[0032] The four cell units 20 are arranged in a straight line. The two central cell units 20 have a neighboring unit number of 2. The two end cell units 20 have a neighboring unit number of 1.

[0033] The thermal resistance value of the insulating material 30 corresponding to each cell unit 20 decreases as the number of adjacent units increases. Specifically, the thermal resistance value of the insulating material 30 corresponding to the central cell unit 20 (i.e., the cell unit 20 with two adjacent units) is smaller than the thermal resistance value of the insulating material 30 corresponding to the cell units 20 on both ends (i.e., the cell unit 20 with one adjacent unit). In this embodiment, the former value is 0.006 m 2 ·K / W, the latter value is 0.028m 2 -K / W.

[0034] In this embodiment, the insulation material 30 corresponding to the central cell unit 20 is made of PVC with a thickness of 1.0 mm (thermal conductivity: 0.170 W / (m K)). The insulation materials 30 corresponding to the cell units 20 on both ends are made of glass wool insulation with a thickness of 1.0 mm (thermal conductivity: 0.036 W / (m K)).

[0035] Third Embodiment A third embodiment will be described below. The battery pack 10 of this embodiment differs from the first embodiment in the number and arrangement of the cell units 20. The following mainly describes the differences from the first embodiment.

[0036] As shown in FIG. 3, the battery pack 10 of the third embodiment includes seven cell units 20 and a thermal insulator 30 corresponding to each cell unit 20.

[0037] The seven cell units 20 are arranged in a staggered pattern. Specifically, the seven cell units 20 consist of one cell unit 20 arranged in the center and six cell units 20 arranged point-symmetrically around it. The central cell unit 20 has six adjacent units. The other cell units 20 have three adjacent units.

[0038] The thermal resistance value of the insulating material 30 corresponding to each cell unit 20 decreases as the number of adjacent units increases. Specifically, the thermal resistance value of the insulating material 30 corresponding to the central cell unit 20 (i.e., the cell unit 20 with six adjacent units) is smaller than the thermal resistance value of the insulating material 30 corresponding to the other cell units 20 (i.e., the cell unit 20 with three adjacent units). In this embodiment, the former value is 0.006 m 2 ·K / W, the latter value is 0.056m 2 -K / W.

[0039] In this embodiment, the insulation material 30 corresponding to the central cell unit 20 is made of PVC with a thickness of 1.0 mm (thermal conductivity: 0.170 W / (m K)). The insulation materials 30 corresponding to the other cell units 20 are made of nanosilica insulation with a thickness of 1.0 mm (thermal conductivity: 0.018 W / (m K)).

[0040] Fourth Embodiment A fourth embodiment will be described below. The battery pack 10 of this embodiment differs from the first embodiment in the configuration, number, and arrangement of the cell units 20. The following mainly describes the differences from the first embodiment.

[0041] As shown in FIG. 4, the battery pack 10 of the fourth embodiment includes 16 cell units 20 and a thermal insulator 30 corresponding to each cell unit 20.

[0042] Each cell unit 20 is composed of four cylindrical cells 21. In each cell unit 20, the four cells 21 are arranged in a lattice pattern.

[0043] The 16 cell units 20 are arranged in a lattice pattern. The four central cell units 20 have four adjacent units. The eight peripheral cell units 20 adjacent to the four central cell units 20 have three adjacent units. The four corner cell units 20 have two adjacent units.

[0044] The thermal resistance value of the insulating material 30 corresponding to each cell unit 20 decreases as the number of adjacent units increases. Specifically, the thermal resistance value of the insulating material 30 corresponding to the four central cell units 20 (i.e., cell units 20 with four adjacent units) is smaller than the thermal resistance value of the insulating material 30 corresponding to the eight peripheral cell units 20 adjacent thereto (i.e., cell units 20 with three adjacent units). In this embodiment, the former value is 0.006 m 2 ·K / W, the latter value is 0.028m 2 -K / W.

[0045] The thermal resistance value of the insulating material 30 corresponding to the four corner cell units 20 (i.e., the cell units 20 with two adjacent units) is greater than the thermal resistance value of the insulating material 30 corresponding to the eight peripheral cell units 20 adjacent to the four central cell units 20. The thermal resistance value of the insulating material 30 corresponding to the four corner cell units 20 is 0.056 m 2 -K / W.

[0046] In this embodiment, the insulation material 30 corresponding to the four central cell units 20 is made of 1.0 mm thick PVC (thermal conductivity: 0.170 W / (m·K)). The insulation material 30 corresponding to the eight peripheral cell units 20 adjacent to the four central cell units 20 is made of 1.0 mm thick glass wool insulation (thermal conductivity: 0.036 W / (m·K)). The insulation material 30 corresponding to the four corner cell units 20 is made of 1.0 mm thick nanosilica insulation (thermal conductivity: 0.018 W / (m·K)).

[0047] Variation of the Fourth Embodiment A modified version of the fourth embodiment will be described below. The battery pack 10 of this modified version differs from the fourth embodiment in that it includes a thermally conductive sheet 40. The following mainly describes the differences from the fourth embodiment.

[0048] As shown in FIG. 5, the battery pack 10 of the modified example of the fourth embodiment includes two thermally conductive sheets 40 having a substantially rectangular shape. One thermally conductive sheet 40 is provided on one end side of the cell unit 20 (the front side in FIG. 5). The other thermally conductive sheet 40 is provided on the other end side of the cell unit 20 (the back side in FIG. 5). Each thermally conductive sheet 40 is in contact with each cell unit 20. Such a thermally conductive sheet 40 reduces temperature variation between the cell units 20. Note that the other thermally conductive sheet 40 is not shown in FIG. 5. Each thermally conductive sheet 40 may be in direct contact with a cell 21 constituting each cell unit 20, or may be in contact with a terminal member (not shown) connected to each cell 21.

[0049] In this embodiment, each thermally conductive sheet 40 is made of silicone rubber (thermal conductivity: 1.7 W / (m·K)) having a thickness of 0.85 mm. EXAMPLES

[0050] The battery packs 10 of Examples 1 to 7 and Comparative Examples 1 to 38 were evaluated for the relationship between the thermal resistance value of each heat insulating material 30 and the performance of the battery packs 10. The performance of the battery pack 10 refers to the discharge time and lifespan. Each cell 21 included in the battery pack 10 is composed of a nickel-metal hydride storage battery (rated capacity 3100 mAh).

[0051] The evaluation conditions for examining the discharge time in a low-temperature environment were as follows: charging for 16 hours at a current of 0.1 It per cell 21 in an atmosphere at 20° C., leaving it in an atmosphere at −20° C. for 3 hours, and then discharging in an atmosphere at −20° C. with a current of 2 It per cell 21 until the electromotive force of the battery pack 10 dropped to 0.8 V × number of series. If the discharge time was 16 minutes or longer, the discharge performance of the battery pack 10 was deemed to be good.

[0052] The evaluation conditions for examining the lifespan were as follows: per cycle, charging was performed at a current of 1 It per cell 21 in an atmosphere at 20° C. until the voltage of the battery pack 10 reached −ΔV=5 mV×number of series from the peak or until 1 hour and 12 minutes had elapsed, leaving the battery pack 10 for 20 minutes in an atmosphere at 20° C., discharging was performed at a current of 1 It per cell 21 in an atmosphere at 20° C. until the electromotive force of the battery pack 10 dropped to 1.0 V×number of series, and then leaving the battery pack 10 for 30 minutes in an atmosphere at 20° C. Then, the battery pack 10 was deemed to have good lifespan performance if the number of cycles was 1000 or more while satisfying the condition that the discharge capacity was 60% or more of the initial discharge capacity.

[0053] In the battery packs 10 of Examples 1 to 3 and Comparative Examples 1 to 6, the arrangement of the cell units 20 is the same as that of the above-mentioned embodiment 1. That is, in the battery packs 10, three cell units 20, each consisting of one cell 21, are arranged in a straight line. The evaluation results of Examples 1 to 3 and Comparative Examples 1 to 6, performed under the above-mentioned evaluation conditions, are shown in Table 1.

[0054] In each table, "RN" refers to the thermal resistance value (unit: m 2In each table, the thermal resistance is 0.056m 2 The insulation material 30 of the K / W is made of nano-silica insulation material with a thickness of 1 mm and a thermal resistance value of 0.028 m 2 The heat insulation material 30 of .K / W is made of glass wool heat insulation material with a thickness of 1 mm and has a thermal resistance of 0.006m 2 The insulation material 30 of the ·K / W is made of 1mm thick PVC. In each table, the unit of discharge time is minutes and the unit of life is cycles.

[0055] [Table 1]

[0056] As can be seen from Table 1, the battery packs 10 of Examples 1 to 3 have good discharge performance and life performance, whereas the battery packs 10 of Comparative Examples 1 to 6 have poor at least one of the discharge performance and life performance.

[0057] In the battery packs 10 of Examples 4 to 6 and Comparative Examples 7 to 12, the arrangement of the cell units 20 is the same as that of the above-mentioned embodiment 3. That is, in the battery packs 10, seven cell units 20, each consisting of one cell 21, are arranged in a staggered pattern with one cell unit 20 at the center. The evaluation results of Examples 4 to 6 and Comparative Examples 7 to 12, performed under the above-mentioned evaluation conditions, are shown in Table 2.

[0058] [Table 2]

[0059] As can be seen from Table 2, the battery packs 10 of Examples 4 to 6 have good discharge performance and life performance, whereas the battery packs 10 of Comparative Examples 7 to 12 have poor at least one of the discharge performance and life performance.

[0060] In the battery packs 10 of Example 7 and Comparative Examples 13 to 38, the arrangement of the cell units 20 is the same as that of the above-mentioned embodiment 4. That is, in the battery packs 10, 16 cell units 20, each consisting of four cells 21, are arranged in a lattice pattern. The evaluation results of Example 7 and Comparative Examples 13 to 38, which were performed under the above-mentioned evaluation conditions, are shown in Table 3.

[0061] [Table 3]

[0062] As can be seen from Table 3, the battery pack 10 of Example 7 has good discharge performance and life performance, whereas the battery packs 10 of Comparative Examples 13 to 38 have poor at least one of the discharge performance and life performance. [Industrial Applicability]

[0063] The present disclosure can be used in battery packs. [Explanation of symbols]

[0064] 10: Battery pack 20: Cell unit 21: Cell 30: Insulation 40: Thermally conductive sheet

Claims

1. n cell units (n is an integer of 3 or more); a heat insulating material disposed so as to surround each of the n cell units; Equipped with The n cell units are arranged such that the numbers of adjacent cell units are not all the same, A battery pack, wherein the thermal resistance value of the insulating material corresponding to each of the cell units is smaller as the number of adjacent cell units increases.

2. The battery pack according to claim 1 , wherein the thermal resistance values ​​of the insulating materials corresponding to the cell units having the same number of adjacent cell units are the same.

3. The thermal resistance of the insulating material is 0.005 m 2 ・K / W is larger than 0.057m 2 The battery pack according to claim 1 or 2, wherein the rated current is smaller than K / W.

4. The battery pack according to any one of claims 1 to 3, further comprising a thermally conductive sheet provided so as to be in contact with each of the cell units.

5. The battery pack according to claim 4 , wherein the thermally conductive sheet is provided on at least one of one end side and the other end side of the cell unit.

6. The battery pack according to any one of claims 1 to 5, wherein the cell unit includes 1 to 4 cells.

7. The battery pack according to any one of claims 1 to 6, wherein the cell unit is composed of cylindrical cells.

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