Battery module

Abstract

[Problem] In a structure having a laminate in which battery cells and plate-shaped members are alternately stacked, the plate-shaped members follow the load changes caused by the expansion and contraction of the battery cells. [Solution] A battery module having a laminate in which a battery cell and an insulating material are alternately laminated in a first direction, wherein the insulating material has an elastic member that contacts a laminated surface facing the first direction among the surfaces of the case, and the elastic member has a first elastic body that contacts the periphery of the laminated surface formed in a frame shape when viewed from the first direction, and a second elastic body that contacts the periphery, is provided on the inner side of the first elastic body when viewed from the first direction, is formed in an approximately square shape to face the center of the laminated surface, and contacts the center, wherein the hardness of the first elastic body is higher than the hardness of the second elastic body, and the second elastic body is composed of a material having the characteristic that its hardness decreases at high temperatures and its hardness increases at low temperatures.

Description

Technology Field

[0001] The present invention relates to a battery module. Background Technology

[0002] Patent Document 1 discloses a battery module comprising a plurality of battery cells and a partition member disposed between adjacent battery cells, wherein the partition member has an expansion and contraction region that follows the expansion and contraction of the battery cells. Prior art literature

[0003] Japanese Patent Publication No. 2014-002907 The problem to be solved

[0004] However, in the configuration described in Patent Document 1, in order for the partition members to follow the expansion or contraction when the battery cell expands or contracts, it was necessary for a plurality of partition members to be fastened by a fastening member. The configuration described in Patent Document 1 requires a structure in which a plurality of partition members are fastened by a fastening member, and it was not intended to envision a structure in which a plurality of partition members are not fastened by a fastening member.

[0005] The present invention, made in consideration of the above circumstances, aims to provide a battery module in which a plate-shaped member can follow load changes caused by the expansion and contraction of a battery cell in a structure having a laminate in which a battery cell and a plate-shaped member are alternately stacked. means of solving the problem

[0006] The present invention is a battery module comprising a battery cell in which an electrode body is accommodated inside a case, and a laminate in which the battery cell and an insulating material in the form of a plate are alternately laminated in a first direction. The insulating material has an elastic member that contacts a laminated surface facing the first direction among the surfaces of the case. The elastic member is formed in a frame shape along the periphery of the laminated surface when viewed from the first direction and has a first elastic body that contacts the periphery, and a second elastic body that is provided inside the first elastic body when viewed from the first direction, is formed in a roughly square shape to face the central part of the laminated surface, and contacts the central part. The hardness of the first elastic body is higher than the hardness of the second elastic body, and the second elastic body is composed of a material having the characteristic that its hardness decreases at high temperatures and increases at low temperatures. Effects of the invention

[0007] In the present invention, in a structure having a laminate in which battery cells and plate-shaped members are alternately stacked, the plate-shaped members can follow the load change caused by the expansion and contraction of the battery cells. Brief explanation of the drawing

[0008] FIG. 1 is a schematic drawing showing a battery module in an embodiment. Figure 2 is a cross-sectional view showing a battery cell and an insulating material. Figure 3 is a diagram showing the case where the insulating material is viewed in the lamination direction. Figure 4 is a diagram illustrating the case where the battery cell is expanded. Figure 5 is a drawing for explaining the first elastic body. Figure 6 is a drawing for explaining the second elastic body. FIG. 7 is a cross-sectional view showing an insulating material in a modified example. Figure 8 is a drawing for explaining the insulating material of a modified example. Figure 9 is a diagram illustrating the case where a battery cell in contact with an insulating material of a deformation example is expanded. Specific details for implementing the invention

[0009] Hereinafter, a battery module in an embodiment of the present invention will be described in detail. Furthermore, the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a schematic diagram showing a battery module in an embodiment. The battery module (1) is included in a battery pack mounted on an electric vehicle such as a plug-in hybrid vehicle (PHEV) or an electric vehicle (BEV). The battery pack mounted on the electric vehicle has a plurality of battery modules (1). The battery module (1) is a battery containing a plurality of single cells. The battery module (1) is a high-voltage battery and also a high-capacity battery.

[0011] A battery module (1) comprises a plurality of battery cells (2) and a plurality of insulating materials (3). The battery module (1) has a laminate (4) in which the battery cells (2) and insulating materials (3) are alternately stacked in a first direction. The first direction is the same direction as the stacking direction of the laminate (4). The first direction corresponds to the X direction.

[0012] The battery cell (2) is a prismatic cell. The battery cell (2) is composed of a lithium-ion secondary battery. In the battery module (1), a plurality of battery cells (2) are arranged side by side in a stacking direction.

[0013] The insulating material (3) is a spacer placed between adjacent battery cells (2) in the stacking direction. The insulating material (3) is a plate-shaped member that contacts the surface of the battery cell (2).

[0014] The laminate (4) is constrained by a constraining member, such as a constraining band. A constraining force in the stacking direction from the constraining member is applied to the laminate (4). By this constraining force, the laminate (4) is integrally held and supported. A constraining force is applied to the battery cell (2) from the insulating material (3).

[0015] FIG. 2 is a cross-sectional view showing a battery cell and an insulating material. The battery cell (2) comprises an electrode body (5), a case (6), a current collector (7), an external terminal (8), and an electrolyte. The insulating material (3) comprises a first elastic body (11) and a second elastic body (12).

[0016] The electrode body (5) is a flat wound body formed by winding a laminate in which a positive electrode sheet and a negative electrode sheet are laminated with a separator interposed therebetween. The electrode body (5) comprises a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator. Before winding, the laminate is laminated in the thickness direction in the order of a positive electrode sheet, a separator, a negative electrode sheet, and a separator. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is a long positive electrode substrate. The positive electrode active material layer is provided on the positive electrode current collector. The positive electrode current collector includes a positive electrode side uncoated portion at one end in the width direction where the positive electrode active material layer is not formed and the positive electrode current collector is exposed. The positive electrode side uncoated portion forms a positive electrode current collection section by winding the positive electrode sheet. A current collection member (7) on the positive electrode side is connected to the positive electrode current collection section. The current collector (7) on the positive side is electrically connected to an external terminal (8) that serves as the positive terminal. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is a long negative electrode substrate. The negative electrode active material layer is provided on the negative electrode current collector. The negative electrode current collector includes a negative electrode side uncoated portion where the negative electrode active material layer is not formed at the other end in the width direction and the negative electrode current collector is exposed. The negative electrode side uncoated portion forms a negative electrode current collection section by winding the negative electrode sheet. The current collector (7) on the negative side is connected to the negative electrode current collection section. The current collector (7) on the negative side is electrically connected to an external terminal (8) that serves as the negative terminal. The separator of the electrode body (5) is a porous resin member for holding and supporting the electrolyte between the positive electrode sheet and the negative electrode sheet. The separator is a nonwoven fabric with high insulating properties. As the electrode body (5) is immersed in the electrolyte, the electrolyte penetrates from the end of the separator toward the center of the separator.

[0017] The case (6) is a case that accommodates the electrode body (5). The case (6) is formed in a roughly rectangular shape. The case (6) is a metal case. For example, the case (6) is composed of aluminum or an aluminum alloy. The case (6) has a pair of laminated surfaces (6a) facing the thickness direction of the battery cell (2). The laminated surfaces (6a) are surfaces that receive a restraining force from the outside of the battery cell (2). The laminated surfaces (6a) are pressed by the insulating material (3) in the state of the laminated body (4). The inner surface of the case wall portion with the laminated surfaces (6a) as the outer surface faces the flat surface of the electrode body (5) in the lamination direction. The case (6) has a case body and a cover body. The case body is a housing having an opening at the top. The cover body is joined to the case body to block the opening of the case body. The case body and the cover body are joined by welding. The interior of the case (6) is sealed. The electrode body (5), the current collector (7), and the electrolyte are contained inside the case (6).

[0018] The current collector (7) is a pair of metal parts connected to both ends of the electrode body (5). For example, the current collector (7) is composed of a metal foil or a metal current collector terminal. The current collector (7) includes a positive electrode current collector and a negative electrode current collector. The positive electrode current collector is positioned at one end of the case (6) in the width direction and is bonded to the positive electrode current collector of the electrode body (5). The positive electrode current collector is made of aluminum. The negative electrode current collector is positioned at the other end of the case (6) in the width direction and is bonded to the negative electrode current collector of the electrode body (5). The negative electrode current collector is made of copper. Additionally, the width direction of the case (6) is the same direction as the width direction of the battery cell (2) and coincides with the Y direction. The thickness direction of the battery cell (2) coincides with the X direction. The height direction of the battery cell (2) coincides with the Z direction.

[0019] The external terminal (8) is a pair of metal parts provided on the cover body and positioned at both ends in the width direction of the case (6). The external terminal (8) is connected to a current collecting member (7) and exposed to the outside of the case (6). The external terminal (8) includes a positive terminal and a negative terminal. The positive terminal is positioned at one end in the width direction of the case (6) and is electrically connected to the positive current collecting member. The negative terminal is positioned at the other end in the width direction of the case (6) and is electrically connected to the negative current collecting member.

[0020] In a battery module (1) configured in this manner, since there is a gap between the electrode body (5) and the case (6) inside the battery cell (2), if the electrode body (5) shakes due to external inputs such as vibration or shock, stress is applied to the current collector (7), and there is a risk that the current collector (7) may be damaged. This phenomenon is likely to occur when the coefficient of linear expansion is significantly reduced under low temperature conditions, or when energy is not supplied to the battery cell (2) under low SOC conditions and the electrode body (5) shrinks. Conversely, under high temperature conditions or high SOC conditions, the battery cell (2) tends to expand, and a load is applied to the case (6) as it expands from the inside to the outside. Therefore, as charging and discharging are repeated, a load is repeatedly applied to the restraining member, and there is a risk of fatigue failure. In order to hold and support the electrode body (5) from the outside of the battery cell (2), it is necessary to use a material with hardness in the insulating material (3) to press the electrode body (5) from the outside to the inside. In contrast, in order to absorb deformation of the battery cell (2), the insulating material (3) must be made of a soft material to absorb the load. To satisfy these two conflicting functions, the insulating material (3) is provided with a first elastic body (11) made of a hard material and a second elastic body (12) made of a soft material. In this case, if the thickness of the elastic body increases and the module length becomes longer, the mounting capability of the battery module (1) deteriorates, and if the module weight increases, vehicle performance deteriorates. Therefore, in the battery module (1), the two elastic bodies are combined in a single insulating material (3) so as not to overlap in the thickness direction, thereby satisfying the two conflicting requirements while suppressing the size and weight. The insulating material (3) is configured to achieve two conflicting uses.

[0021] The insulating material (3) absorbs load or shock to prevent damage or cracking caused by stress on the components of the battery module (1) when the battery cell (2) expands under high SOC or high temperature. The insulating material (3) fixes the electrode body (5) to prevent the electrode body (5) inside the case (6) from moving relatively due to external force when the battery cell (2) shrinks under low SOC or low temperature, and to prevent the current collector member (7) connecting the external terminal (8) and the electrode body (5) from being damaged and causing poor current conduction.

[0022] The insulating material (3) is composed of an elastic member comprising a first elastic body (11) and a second elastic body (12). The elastic member contacts a stacking surface (6a) facing the stacking direction among the surfaces of the case (6). The elastic member is a flat plate facing the battery cell (2) in the stacking direction and is formed to be approximately the same size as the stacking surface (6a). The elastic member is formed in a shape where the entire surface contacts the stacking surface (6a). Since the elastic member has a temperature dependence on hardness, it is composed of a material that becomes soft with lower hardness under high temperature conditions and hard with higher hardness under low temperature conditions. The first elastic body (11) and the second elastic body (12) are composed of a resin containing an elastic component, such as an elastomer, in order to absorb the amount of deformation during the expansion of the battery cell (2) and to hold and support the electrode body (5) during the contraction of the battery cell (2).

[0023] The first elastic body (11) is an elastic body for holding and supporting the electrode body (5). The first elastic body (11) is harder than the second elastic body (12). The hardness of the first elastic body (11) is higher than the hardness of the second elastic body (12). As shown in FIG. 3, the insulating material (3) is formed in a square shape when viewed from the stacking direction. The first elastic body (11) is formed in a square frame shape to form the periphery of the insulating material (3). As shown in FIG. 2, the thickness of the first elastic body (11) is the same as the thickness of the second elastic body (12). The first elastic body (11) is formed in a frame shape along the periphery of the stacking surface (6a) when viewed from the stacking direction. The first elastic body (11) contacts the periphery of the stacking surface (6a). As illustrated in FIG. 2, since it is necessary to hold and support the electrode body (5) at low SOC or low temperature, a first elastic body (11) made of a hard material is disposed in the part that contacts the periphery of the laminated surface (6a). In addition, FIG. 2 illustrates a case where the battery cell (2) is shrunken.

[0024] The second elastic body (12) is an elastic body that receives stress from the battery cell (2). The second elastic body (12) is softer than the first elastic body (11). As shown in FIGS. 2 and 3, the second elastic body (12) is provided inside the first elastic body (11). The first elastic body (11) and the second elastic body (12) are integrated. The second elastic body (12) is formed in a roughly square shape when viewed from the stacking direction. The second elastic body (12) faces the central part of the stacking surface (6a) in the stacking direction. The second elastic body (12) contacts the central part of the stacking surface (6a). As shown in FIG. 4, when the battery cell (2) expands, the second elastic body (12) is elastically deformed to absorb the amount of deformation caused by the expansion of the battery cell (2). The second elastic body (12) is composed of a material having the characteristic that its hardness decreases at high temperatures and increases at low temperatures. That is, the second elastic body (12) is composed of a material having a temperature dependence of hardness.

[0025] The insulating material (3) has a material with temperature-dependent hardness placed in the inner portion that contacts the central portion of the laminated surface (6a) and holds and supports the case (6). Since the battery cell (2) swells at high SOC or high temperature and needs to absorb this amount of deformation, a second elastic body (12) made of a material with temperature-dependent hardness is placed in the portion that contacts the central portion of the laminated surface (6a). Since the load on the battery cell (2) varies with temperature, as the temperature increases, the battery cell (2) swells, and the load received by the insulating material (3) also increases.

[0026] The insulating material (3) can be utilized in the same shape by changing the material of the elastic body according to the battery capacity or the method of use of the vehicle. When the temperature is high, the battery cell (2) expands, and when the temperature is low, the battery cell (2) contracts. When the SOC is high, the battery cell (2) expands, and when the SOC is low, the battery cell (2) contracts. When the battery cell (2) has deteriorated over time, it expands, and when it is new, it contracts. The SOC, years of use, number of charge / discharge cycles, and battery capacity are also factors that affect the load received by the insulating material (3). It is preferable that the first elastic body (11) and the second elastic body (12) be made of a material with appropriate hardness according to these factors. In order to become an appropriate insulating material (3) depending on the usage method or characteristics of the battery cell (2), the hardness ratio of the material of the outer first elastic body (11) and the material of the inner second elastic body (12) is mapped, so that it can correspond to the same shape for any usage method or battery cell (2). For the first elastic body (11) and the second elastic body (12), materials whose hardness changes with temperature are utilized, so that the function can be maintained even when the usage temperature is increased.

[0027] As shown in FIGS. 5 and 6, even when a battery module (1) is mounted on a vehicle of any type, a relationship is established in which the hardness of the first elastic body (11) is higher than the hardness of the second elastic body (12).

[0028] As illustrated in FIG. 5, the hardness of the first elastic body (11) increases as the cell capacity increases. When the cell capacity is small, the number of charge / discharge cycles of the battery cell (2) increases, and swelling occurs due to fluctuations in SOC, so the material of the first elastic body (11) becomes softer than when the cell capacity is large. When the operating temperature is high, swelling occurs due to fluctuations in the temperature of the battery cell (2), so the material of the first elastic body (11) becomes softer than when the operating temperature is low. The material constituting the first elastic body (11) can be determined according to the type of electric vehicle in which the battery module (1) is mounted.

[0029] As illustrated in FIG. 6, the hardness of the second elastic body (12) increases as the cell capacity increases. When the cell capacity is small, the number of charge and discharge cycles of the battery cell (2) increases, and swelling occurs due to fluctuations in SOC, so the material of the second elastic body (12) becomes softer than when the cell capacity is large. When the operating temperature is high, swelling occurs due to fluctuations in the temperature of the battery cell (2), so the material of the second elastic body (12) becomes softer than when the operating temperature is low. The material constituting the second elastic body (12) can be determined according to the type of electric vehicle in which the battery module (1) is mounted. When the cell capacity is large, the number of expansion and contraction cycles until EOL is large, so the absorption amount is increased with a soft material.

[0030] As described above, according to the embodiment, it is possible for the insulating material (3) to follow the load change caused by the expansion and contraction of the battery cell (2) in the laminate (4). In addition, it can cover the environment of SOC or temperature, and can also prevent damage to the battery cell (2) or module components even if the lineup of vehicles increases.

[0031] In addition, the composition of the insulating material (3) is not limited to the structure exemplified in FIG. 2, etc. As shown in FIG. 7, the insulating material (3) may have a structure in which an insulating material (13) is provided inside an elastic member. The insulating material (13) is a plate-shaped member that does not come into contact with the laminated surface (6a).

[0032] As illustrated in FIGS. 7 to 9, the insulating material (3) comprises an insulating material (13) provided on the inner side of the first elastic body (11) and the second elastic body (12). The insulating material (13) is composed of a resin having an elastic component, such as an elastomer, in order to have insulating properties, absorb the amount of deformation when the battery cell (2) expands, and support the electrode body (5) when the battery cell (2) contracts. The insulating material (13) is provided on the inner side of the first elastic body (11) when viewed from the stacking direction and is stacked with the second elastic body (12) in the stacking direction. The insulating material (13) forms an insulating layer on the inner side of the second elastic body (12). The second elastic body (12) includes a first elastic layer that contacts the central part of the battery cell (2) adjacent to one side of the stacking direction, and a second elastic layer that contacts the central part of the battery cell (2) adjacent to the other side of the stacking direction. The second elastic layer is laminated with the first elastic layer by interposing an insulating material (13). Inside the first elastic body (11), a three-layer structure is formed in which the second elastic body (12) as the first elastic layer, the insulating material (13) as the insulating layer, and the second elastic body (12) as the second elastic layer are laminated.

[0033] Additionally, the hardness and material of the second elastic body (12) can be determined by comprehensively considering the cell capacity, SOC, and operating temperature. For example, the hardness of the second elastic body (12) is determined using a hardness coefficient. The hardness coefficient is set for the cell capacity, SOC, and operating temperature, respectively. The relationship between the cell capacity and the hardness coefficient is that the hardness coefficient increases as the cell capacity increases. The relationship between the SOC and the hardness coefficient is that the hardness coefficient decreases as the SOC increases. The relationship between the operating temperature and the hardness coefficient is that the hardness coefficient decreases as the operating temperature increases. The hardness coefficient determined by the cell capacity, the hardness coefficient determined by the SOC, and the hardness coefficient determined by the operating temperature are accumulated, and the hardness of the second elastic body (12) is determined based on the accumulated value. The larger the accumulated value, the higher the hardness. Explanation of the symbols

[0034] 1: Battery module 2: Battery cell 3: Insulating material 4: Laminate 5: Electrode 6: Case 6a: Lamination surface 7: Absence of the Lord 8: External terminal 11: First elastic body 12: Second elastic body 13: Insulation

Claims

Claim 1 A battery module comprising a battery cell in which an electrode is housed inside a case, and a laminate in which the battery cell and an insulating material in the form of a plate are alternately laminated in a first direction, wherein the insulating material has an elastic member that contacts a laminated surface facing the first direction among the surfaces of the case, and the elastic member has a first elastic body that is formed in a frame shape along the periphery of the laminated surface when viewed from the first direction and contacts the periphery, and a second elastic body that is provided inside the first elastic body when viewed from the first direction, is formed in a roughly square shape to face the central part of the laminated surface, and contacts the central part, wherein the hardness of the first elastic body is higher than the hardness of the second elastic body, and the second elastic body is composed of a material having the characteristic that its hardness decreases at high temperatures and increases at low temperatures. Claim 2 A battery module according to claim 1, characterized in that the thickness of the second elastic body is the same as the thickness of the first elastic body. Claim 3 A battery module according to claim 1, wherein the insulating material is provided inside the elastic member and has an insulating material that does not contact the laminated surface, and the insulating material is provided inside the first elastic body when viewed from the first direction and is laminated with the second elastic body in the first direction, and the second elastic body comprises a first elastic layer that contacts the central part of the battery cell adjacent to one side of the first direction, and a second elastic layer that is laminated with the first elastic layer with the insulating material interposed therebetween and contacts the central part of the battery cell adjacent to the other side of the first direction.

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