Secondary batteries and modules

Abstract

To provide a secondary battery with excellent heat dissipation efficiency of the electrode body and a module equipped therewith. [Solution] A secondary battery and a module comprising an electrode body having a current collector, an active material layer and a separator layer, and a metal casing body housing the electrode body, wherein at least a portion of the metal casing body facing the side surface of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state.

Description

Technical Field

[0001] The present disclosure relates to secondary batteries and modules.

Background Art

[0002] A secondary battery includes an electrode body (also referred to as an electrode assembly) and a case (hereinafter also referred to as an “outer package”) that houses the electrode body. As the outer package, there are a metal outer package made of metal and a laminate outer package made of multiple layers of laminate sheets. Patent Document 1 discloses a rectangular can body for a secondary battery, wherein the thickness of one surface of the can body is thicker than the thickness of the surface adjacent to the one surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The heat dissipation of a secondary battery is an important factor that affects battery life and output. In particular, the heat generated by the electrode body in the discharge state needs to be released to the outside through the outer package, and from this perspective of heat dissipation, the metal outer package is excellent. To enhance the heat dissipation of the electrode body in the discharge state, it is important to ensure the contact between the metal outer package and the electrode body. However, in a conventional secondary battery, in the discharge state, the side surface (i.e., the thickness direction side surface) facing the stacking direction of the electrode body tends to bend outward, and a gap tends to form between the metal outer package and the electrode body. Therefore, it is difficult to ensure the contact between the metal outer package and the electrode body, and the heat dissipation efficiency tends to be low. In addition, since an insulating material is arranged between the side surface of the electrode body and the metal outer package, the heat dissipation efficiency further decreases by the thickness of the insulating material, or the number of battery units that can be accommodated in the module cannot be sufficiently ensured, resulting in a decrease in structural efficiency.

[0005] This disclosure has been made in light of the circumstances described above. One embodiment of this disclosure aims to solve the problem of providing a secondary battery and module with excellent heat dissipation efficiency of the electrode body. [Means for solving the problem]

[0006] The following embodiments are included as means for solving the above problems.

[0007] <1> An electrode body comprising a current collector, an active material layer and a separator layer, A metal casing housing the electrode body, Equipped with, A secondary battery in which at least a portion of the metal casing facing the side surface of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state. <2> At least a portion of the metal casing facing the side surface of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a free state, <1> The secondary battery described above. <3> The portion of the metal casing facing the pair of sides of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state. <1> or <2> The secondary battery described above. <4> An insulating material is disposed between the side surface of the electrode body on the current collector side and the portion of the metal casing facing the side surface of the electrode body on the current collector side. <1> ~ <3> A rechargeable battery as described in one of the following. <5> The aforementioned <1> ~ <4> A module comprising multiple rechargeable batteries as described in one of the following documents. [Effects of the Invention]

[0008] According to this disclosure, a secondary battery and module with excellent heat dissipation efficiency of the electrode body are provided. [Brief explanation of the drawing]

[0009] [Figure 1]Figure 1 is a schematic cross-sectional view of a conventional secondary battery in its charged state. [Figure 2] Figure 2 is a schematic cross-sectional view of a conventional secondary battery in its discharge state. [Figure 3] Figure 3 is a schematic cross-sectional view of the secondary battery according to this disclosure in its charged state. [Figure 4] Figure 4 is a schematic cross-sectional view of the discharge state of the secondary battery according to this disclosure. [Figure 5] Figure 5 is a schematic diagram showing an example of a method for creating a recessed shape in the metal casing of a secondary battery according to this disclosure. [Figure 6] Figure 6 is a perspective view of the module relating to this disclosure. [Figure 7] Figure 7 is a top view of the module relating to this disclosure with the case cover removed. [Figure 8] Figure 8 is a schematic diagram showing the free state of the metal casing in the secondary battery according to this disclosure. [Figure 9] Figure 9 is a schematic diagram showing an example of a stacked electrode configuration. [Modes for carrying out the invention]

[0010] The following description illustrates one embodiment and does not limit the scope of this disclosure. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In numerical ranges described stepwise in this disclosure, an upper or lower limit described in one numerical range may be replaced by an upper or lower limit in another numerical range described stepwise.

[0011] <Secondary battery> The secondary battery according to this disclosure comprises an electrode body having a current collector, an active material layer and a separator layer, and a metal casing that houses the electrode body, wherein at least a portion of the metal casing that faces the side of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state.

[0012] FIG. 1 is a schematic cross-sectional view of a conventional secondary battery in a charged state. FIG. 2 is a schematic cross-sectional view of a conventional secondary battery in a discharged state. As shown in FIGS. 1 and 2, the conventional secondary battery 100 includes a metal exterior body 50 that houses an electrode body 10 and an insulating material 20. Although not shown, in FIGS. 1 and 2, the conventional secondary battery 100 has a metal cylindrical body in which the metal exterior body 50 has a space for housing the electrode body 10 and the insulating material 20, and the electrode body 10 is a plate-like body. In the conventional secondary battery 100 shown in FIGS. 1 and 2, an insulating material 20 is disposed between a portion of the metal exterior body 50 that faces a pair of side surfaces on the current collector side of the electrode body 10. As shown in FIG. 1, in the conventional secondary battery 100 in a charged state, due to the expansion and size design of the electrode body 10, the metal exterior body 50 and the insulating material 20 are in full contact. When this conventional secondary battery 100 is in a discharged state, as shown in FIG. 2, the electrode body 10 contracts, and following this, the insulating material 20 and the metal exterior body 50 are separated and no longer in contact. Therefore, the heat dissipation efficiency of the electrode body 10 tends to be low. Also, when the insulating material 20 tries to follow the contraction of the electrode body 10 in the discharged state, a gap occurs between the electrode body 10 and the metal exterior body 50, making it difficult to sufficiently secure the number of battery units that can be accommodated in the module, and the structural efficiency tends to be low.

[0013] According to the present disclosure, by having the above configuration, along with the contraction of the electrode body in the discharged state, at least a part of the portion of the metal exterior body that faces the side surface on the current collector side of the electrode body is deformed so as to be recessed toward the electrode body side, and a contact point between the metal exterior body and the electrode body is ensured. As a result, the heat dissipation efficiency of the electrode body is excellent. Also, according to the present disclosure, the number of battery units that can be accommodated in the module is sufficiently ensured, and the structural efficiency is also excellent. Further, by deforming at least a part of the metal exterior body that faces the side surface on the current collector side of the electrode body so as to be recessed toward the electrode body side, the absorbability of dimensional variations that occur during the manufacture of the electrode body is also excellent.

[0014] In the present disclosure, the “free state” refers to a state in which no mechanical load such as pressure is applied from the outside to the metal exterior body.

[0015] FIG. 3 is a schematic cross-sectional view of the secondary battery according to the present disclosure in a charged state. FIG. 4 is a schematic cross-sectional view of the secondary battery according to the present disclosure in a discharged state. FIG. 8 is a schematic view of the metal exterior of the secondary battery according to the present disclosure in a free state. As shown in FIGS. 3 and 4, the secondary battery 100 includes a metal exterior 50 that houses an electrode body 10 and an insulating material 20. The insulating material 20 is disposed between the electrode body 10 and the metal exterior 50.

[0016] As shown in FIG. 8, in the free state, at least a part of the portion of the metal exterior 50 facing the side surface of the electrode body 10 on the current collector side in the electrode body 10 is concave toward the electrode body side. As shown in FIG. 3, in the charged state of the secondary battery 100 of the present disclosure, the metal exterior 50 is deformed so as to follow the expansion of the electrode body 10, and the contact area between the metal exterior 50 and the insulating material 20 increases. Although the configuration at the lower part of the drawing is omitted for convenience in FIGS. 3 and 4, the metal exterior 50 is a cylindrical metal body having a space in which the electrode body 10 and the insulating material 20 are housed, and the electrode body 10 is a plate-like body. In addition, in this specification, the “cylindrical body” is a concept including a configuration composed of a metal can and a metal can lid. As shown in FIG. 4, when the secondary battery 100 of the present disclosure is in a discharged state, as the electrode body 10 contracts due to heat dissipation, the shape of the metal exterior 50 returns to the shape according to the free state. That is, in the metal exterior 50, at least a part of the portion of the metal exterior facing the side surface of the electrode body on the current collector side is concave toward the electrode body side in the discharged state. In this concave shape, since the insulating material 20 and the metal exterior 50 are partially in contact, it is considered that the heat dissipation of the electrode body 10 becomes efficient through the contact portion.

[0017] The metal casing 50 only needs to have a shape in which at least a portion of the metal casing 50 facing the side of the electrode body 10 on the current collector side is recessed toward the electrode body 10 when in a discharge state. However, from the viewpoint of further improving the heat dissipation efficiency of the electrode body 10, for example, it is preferable that the side opposite to the side on which the cooling system is located when the module comprising the electrode body 10 is made is recessed, and it is even more preferable that both sides (i.e., the portions of the metal casing facing the pair of sides of the electrode body on the current collector side) are recessed.

[0018] In Figures 3 and 4, the insulating material 20 is placed between the current collector-side surface of the electrode body 10 and the portion of the metal casing facing the current collector-side surface of the electrode body 10. However, it is preferable that the insulating material be placed between each of the two current collector-side surfaces and the portions of the metal casing facing them. The insulating material 20 may also be provided in a manner that covers all of the sides of the electrode body 10.

[0019] The method for manufacturing the secondary battery according to this disclosure is not particularly limited, and known methods for manufacturing secondary batteries can be applied. Figure 5 is a schematic diagram showing an example of a method for creating a recessed shape in the metal casing of the secondary battery according to this disclosure. As shown in Figure 5, both sides in the thickness direction of the secondary battery 100 in the discharged state are clamped with a pair of clamps 60. A retainer 70 is placed on one of the faces of the secondary battery 100 that are facing each other in the thickness direction. Although not shown, pressing members are adjacent to the pair of clamps 60. Although not shown, when creating a shape in which the portion of the metal casing 50 facing the pair of sides on the current collector side of the electrode body of the secondary battery 100 is recessed toward the electrode body 10 when in the discharged state, the pair of retainers 70 are placed so as to be in contact with the pair of sides. As shown in Figure 5, when the secondary battery 100 is pressed from the direction of the arrow via the clamps 60 with a pressing member or the like, the area where the retainer 70 is placed is recessed toward the side where the electrode body 10 is provided.

[0020] [Electrode body] The electrode body is not particularly limited as long as it comprises a current collector, an active material layer, and a separator layer, and known electrode bodies used in secondary batteries can be applied. Examples of electrode bodies include electrode stacks. An electrode stack is composed of multiple electrodes stacked with separators in between. The electrodes may, for example, have a stack of multiple bipolar electrodes.

[0021] Figure 9 schematically shows an example of the configuration of the laminated structure included in the electrode body. Figure 9 is a schematic diagram showing an example of the laminated structure of the electrode body. The electrode body 200 shown in Figure 9 consists of a positive electrode 90, a negative electrode 92, and a separator 85 (an example of a separator) placed between the positive electrode 90 and the negative electrode 92. The positive electrode 90 consists of a positive electrode active material layer 90A (an example of an active material layer) and a positive electrode current collector 90B (an example of a current collector). The negative electrode 92 consists of a negative electrode active material layer 92A (an example of an active material layer) and a negative electrode current collector 92B (an example of a current collector).

[0022] [Metal exterior] The metal casing is made of metal. Examples of metal materials include aluminum, aluminum alloys, stainless steel, copper, copper alloys, and nickel steel. The metal casing positioned in contact with the positive electrode foil and the metal casing positioned in contact with the negative electrode foil in the electrode body may be made of the same material or different materials. The thickness of the positive electrode metal casing and the negative electrode metal casing is, for example, 0.05 mm to 2.00 mm.

[0023] From the viewpoint of providing superior heat dissipation efficiency for the electrode body and superior structural efficiency when incorporated into a module, it is preferable that at least a portion of the metal casing facing the side of the electrode body on the current collector side is shaped to be recessed toward the electrode body during discharge, and to be shaped to be recessed toward the electrode body during both the discharged state and the free state.

[0024] From the viewpoint of providing superior heat dissipation efficiency for the electrode body and superior structural efficiency when incorporated into a module, it is preferable that at least a portion of the metal casing facing the current collector side of the electrode body is shaped to be recessed toward the electrode body when discharged, and that at least a portion of the metal casing facing the pair of current collector side of the electrode body is shaped to be recessed toward the electrode body when discharged.

[0025] [Insulating materials] In secondary batteries, from the viewpoint of battery performance, it is preferable that an insulating material is placed between the current collector-side surface (more preferably a pair of surfaces) of the electrode body and the portion of the metal casing facing the current collector-side surface of the electrode body. The insulating material may also be provided between all surfaces of the electrode body (i.e., in addition to the current collector-side surface of the electrode body, the surfaces in the stacking direction of the electrode body) and the portion of the metal casing facing all of the aforementioned surfaces.

[0026] Examples of insulating materials include copolymers such as styrene-ethylene-ethylene-propylene-styrene block copolymers and styrene-butadiene-styrene block copolymers; elastomers such as styrene-butadiene rubber, butadiene rubber, and nitrile rubber; fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene; acrylic resins such as polymethyl acrylate and polymethyl methacrylate resin; and polyimide, polyamide, polyvinyl chloride, polyethernitrile, polyethylene, polypropylene, polyacrylonitrile, poly(meth)acrylic acid, hydroxyethylcellulose, and polyvinyl alcohol. The insulating materials may be used individually or in combination of two or more types.

[0027] The insulating material may further contain additives, and there are no particular restrictions on the type or amount of these additives. For example, insulating particles such as inorganic particles or organic particles may be included.

[0028] <module> The module according to this disclosure is a module comprising a plurality of secondary batteries according to this disclosure. Because the module according to this disclosure comprises secondary batteries according to this disclosure, it has excellent heat dissipation efficiency. In addition, the outward deflection of the side surfaces of the electrode bodies facing the stacking direction (i.e., the side surfaces in the thickness direction) in response to the thermal expansion of the electrode bodies is suppressed, and the restraint between secondary batteries is easily achieved.

[0029] Figure 6 is a perspective view of the module according to this disclosure. Figure 7 is a top view of the module according to this disclosure with the case lid removed. The module 1 according to this disclosure may, for example, include a plurality of secondary batteries 2 and a metal case 40, as shown in Figure 6. The metal case 40 houses the plurality of secondary batteries 2. The module 1 is a rectangular parallelepiped. In this disclosure, the thickness direction of the module 1 is the X-axis direction, the longitudinal direction of the module 1 is the Y-axis direction, and the short direction of the module 1 is the Z-axis direction. The X-axis, Y-axis, and Z-axis are orthogonal to each other. Note that these orientations do not limit the orientation of the batteries and module when used. A pair of voltage terminals 21 and a connector 12 are provided at both ends of the module 1 in the Y-axis direction. A flexible printed circuit board 13, which will be described later, is connected to the connector 12. Although not shown, busbars are welded to both ends of the module 1 in the Y-axis direction. The metal case 40 has a metal case body 101 and a metal case lid 102. The metal case 40 is formed from an aluminum alloy. The metal case 40 is formed, for example, by joining aluminum die-cast parts to both ends of an aluminum alloy extruded material by laser welding or the like.

[0030] As shown in Figure 7, multiple secondary batteries 2 are housed inside module 1 in an arranged manner. Although not shown, adjacent secondary batteries 2 may be restrained by restraints or the like, or they may be bonded to each other. A flexible printed circuit board (FPC) 13 is placed on top of the secondary batteries 2. The flexible printed circuit board 13 is formed in a strip shape with the Y-axis direction as its longitudinal direction, and thermistors 14 are provided at both ends of the flexible printed circuit board 13. In module 1, the thermistors 14 are not bonded to the secondary batteries 2, but are pressed toward the secondary batteries 2 by the metal case lid 102. Although not shown in the figures, one or more cushioning materials are housed inside module 1. For example, the cushioning material is a thin, elastically deformable plate-like member, and is placed between adjacent secondary batteries 2 with the arrangement direction of the secondary batteries 2 as the thickness direction. In this disclosure, as an example, cushioning materials are placed at both ends in the longitudinal direction and in the longitudinal center of module 1.

[0031] Applications of the module relating to this disclosure include, for example, power sources for hybrid vehicles, plug-in hybrid vehicles, electric vehicles, and the like. [Explanation of Symbols]

[0032] 1 Module, 2 Secondary battery, 40 Metal case, 12 Connector, 13 Flexible printed circuit board, 14 Thermistor, 21 Voltage terminal, 101 Metal case body, 102 Metal case lid, 100 Secondary battery, 10 Electrode body, 20 Insulating material, 50 Metal casing, 60 Clamp, 70 Retainer, 200 Electrode body, 90 Positive electrode, 92 Negative electrode, 85 Separator, 90A Positive electrode active material layer, 90B Positive electrode current collector, 92A Negative electrode active material layer, 92B Negative electrode current collector

Claims

1. An electrode body comprising a current collector, an active material layer and a separator layer, A metal casing housing the electrode body, Equipped with, A secondary battery in which at least a portion of the metal casing facing the side surface of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state.

2. The secondary battery according to claim 1, wherein at least a portion of the metal casing facing the side surface of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a free state.

3. The secondary battery according to claim 1, wherein the portion of the metal casing facing the pair of sides of the electrode body on the current collector side is shaped to be recessed toward the electrode body when in a discharge state.

4. The secondary battery according to claim 1, wherein an insulating material is disposed between the side surface of the electrode body on the current collector side and the portion of the metal casing facing the side surface of the electrode body on the current collector side.

5. A module comprising a plurality of secondary batteries as described in any one of claims 1 to 4.

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