Battery module

Abstract

In a battery module 1 in which current collector plates 6 are attached to each of the electrode foils 3 on both outer surfaces of a flat-shaped battery cell 2 via adhesive 7, the heat generated inside the battery module is to be efficiently dissipated. [Solution] In a battery module in which a current collector plate is attached to each of the electrode foils on both outer surfaces of a flat-shaped battery cell via adhesive, a conductive adhesive application area 7e and a heat dissipation adhesive application area 7h are provided between each electrode foil and current collector plate on both outer surfaces, and at least a portion of the area of ​​the other outer surface that is opposite the conductive adhesive application area on one of the outer surfaces is the heat dissipation adhesive application area.

Description

Technical Field

[0001] The present invention relates to a battery module, and more particularly to a battery module in which battery cells have a flat plate structure and current collectors are attached to electrode foils on both sides thereof.

Background Art

[0002] In a battery module such as a lithium-ion secondary battery, a single cell has a laminated structure in which a positive electrode active material layer coated on an electrode foil (positive electrode foil) that may be a metal foil and a negative electrode active material layer coated on an electrode foil (negative electrode foil) that may be a metal foil face each other with a separator (in the case of a liquid-based battery) or a solid electrolyte layer (in the case of an all-solid-state battery) immersed in an electrolytic solution interposed therebetween, and a configuration in which a plurality of such single cells are stacked is known. Also, in a battery module having such a configuration, a configuration (bipolar battery) in which the positive electrode foil and the negative electrode foil of adjacent cells are integrated and the stacked cells are connected in series is also known. Various configurations have been proposed for various problems that can occur in such a battery module. For example, in Patent Document 1, it has been proposed to incorporate a heat dissipating material in a side resin frame in order to efficiently dissipate heat inside the battery. In Patent Document 2, in an electrode for an all-solid-state battery having a current collector and an electrode layer, in order to reduce the resistance of the all-solid-state battery, where the contact surface between the current collector and the electrode layer is adhered by an adhesive layer, the adhesive layer is composed of a plurality of adhesive lines arranged in a stripe shape at the contact surface, and the ratio (B / A) of the coating width B (mm) of the adhesive lines to the electrical conductivity A (mS) of the electrode layer is set to 75.00 or less, the distance C (mm) between adjacent adhesive lines is set to be greater than 0.2 mm and 7 mm or less, and the ratio (B / C) of the coating width B of the adhesive lines to the distance C between adjacent adhesive lines is set to 2.00 or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] In the battery module described above, the series-connected battery cells are flat in shape, and a configuration is known in which current collector plates, which constitute part of the outer casing housing the battery module, are attached to the outer electrode foils of the cells on both sides of the cell row. In some cases, a conductive adhesive is used to attach the current collector plates to the outer electrode foils of the cell row. However, such conductive adhesives may not have very high thermal conductivity, and in that case, if the heat generated inside the battery module is not properly dissipated, the internal core temperature tends to rise, raising concerns about a decrease in battery life and a reduction in safety performance.

[0005] In view of the above circumstances, the main object of the present invention is to enable efficient dissipation of heat generated inside a battery module in which a current collector plate is attached to each of the electrode foils on both outer surfaces of a flat-shaped battery cell via an adhesive.

[0006] In this regard, research by the inventors of the present invention has shown that, regarding the application of adhesive between the electrode foils on both outer surfaces of the flat-shaped battery module and the current collector, if a conductive adhesive application area and a heat-dissipating adhesive (highly thermally conductive adhesive) application area are provided on each outer surface of the battery module, and if the heat-dissipating adhesive is applied to at least a portion of the area on the other surface facing the conductive adhesive application area on one surface, it is found that the conductivity between the electrode foils and the current collector (due to the use of conductive adhesive) on both outer surfaces of the battery module is ensured, while heat inside the battery module is more evenly and effectively dissipated in the direction of the battery module's surface. This finding is utilized in the present invention. [Means for solving the problem]

[0007] According to the present invention, the above problem is solved by a battery module in which a current collector plate is attached to each of the electrode foils on both outer surfaces of a flat-plate shaped battery cell via an adhesive, wherein a conductive adhesive application area and a heat dissipation adhesive application area are provided between each of the electrode foils on both outer surfaces and the current collector plate, and at least a portion of the area of ​​the other outer surface facing the conductive adhesive application area on one of the outer surfaces is the heat dissipation adhesive application area.

[0008] In the above configuration, the "battery cell" may be a cell of a non-aqueous secondary battery, and is typically a cell of a lithium-ion secondary battery. As already mentioned, a single cell has a laminated structure in which a positive electrode foil and a negative electrode foil, which may be metal foils in a normal manner, are coated with a positive electrode active material layer and a negative electrode active material layer, respectively, and are facing each other with a separator (in the case of a liquid-based battery) or a solid electrolyte layer (in the case of an all-solid-state battery) in which they are immersed in an electrolyte. Multiple single cells are superimposed on a battery cell. In this specification, the term "battery cell" refers not only to a single cell but also to a laminate of multiple cells. Furthermore, with the exception of the outer electrode foils of the outermost cells of the multiple superimposed cells, the positive electrode foil and negative electrode foil of each cell may, together with the negative electrode foil and positive electrode foil of the adjacent cell, form a bipolar electrode. The positive electrode foil, negative electrode foil, positive electrode active material layer, negative electrode active material layer, and electrolyte layer (separator or solid electrolyte layer immersed in electrolyte) may be formed in a conventional manner. The "current collector plate" may be a metal plate such as aluminum. The "conductive adhesive" is an adhesive with high electrical conductivity, for example, with a volume resistivity of 2.0 × 10⁻⁶. -6 Adhesives with a thermal conductivity of (Ω·m) or less are selected (high thermal conductivity is not required). A "heat-dissipating adhesive" is an adhesive with high thermal conductivity; for example, one with a thermal conductivity of 2.1 W / (m·K) or higher is selected (high electrical conductivity is not required). The application area of ​​the conductive adhesive may be the minimum area that does not affect battery performance. The thickness of the adhesive layer may be 0.1 to 3 mm, etc.

[0009] Furthermore, in the present invention, as described above, a conductive adhesive coating area and a heat-dissipating adhesive coating area are provided between the electrode foil and the current collector plate on each of the outer surfaces of the battery cell. The conductive adhesive coating area and the heat-dissipating adhesive coating area are provided such that at least a portion of the area of ​​the other outer surface facing the conductive adhesive coating area on one of the outer surfaces is the heat-dissipating adhesive coating area. As can be understood from the calculation experiment example described later, the amount of heat dissipated is greater than when the entire adhesive is a conductive adhesive, and the unevenness of heat dissipation in the planar direction of the battery cell is eliminated (the temperature becomes approximately uniform), resulting in better heat dissipation.

[0010] In the above configuration, the areas coated with conductive adhesive and the areas coated with heat-dissipating adhesive may be arranged alternately in a striped pattern, for example. Calculation experiments have shown that if the area on one of the outer surfaces of the battery cell that is opposite the area coated with conductive adhesive is coated with heat-dissipating adhesive, then uniform heat dissipation can be obtained in the planar direction of the battery cell, regardless of the width of the coated area. [Effects of the Invention]

[0011] Thus, according to the configuration of the present invention, in a battery module in which current collector plates are attached to the electrode foils on both sides of a flat-shaped battery cell via adhesive, by using a heat-dissipating adhesive as part of the adhesive, and by providing areas of heat-dissipating adhesive on both outer surfaces of the battery cell opposite the areas of conductive adhesive, heat can be dissipated evenly and effectively in the planar direction of the battery module. The configuration of the present invention is also advantageous in that good heat dissipation can be easily obtained because it only requires adjusting the areas of conductive adhesive and heat-dissipating adhesive.

[0012] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention. [Brief explanation of the drawing]

[0013] [Figure 1]Figure 1 is a schematic cross-sectional view of a battery module to which this embodiment is applied. [Figure 2] Figure 2(A) is a schematic perspective view of a battery module model used in a computational experiment to verify the effectiveness of this embodiment. Figure 2(B) is a schematic cross-sectional view of the battery module model showing points where the temperature in the battery module was referenced in the computational experiment. Figures 2(C) to (E) are schematic cross-sectional views of the battery module model showing the areas where conductive adhesive and heat-dissipating adhesive are applied in the adhesive layer of the battery module, as set in the computational experiment (the shaded area is inside the battery cell). (C) is the case where the adhesive layer is uniformly treated as an area of ​​conductive adhesive, (D) is the case where the areas where conductive adhesive and heat-dissipating adhesive are applied on both sides of the battery module face areas of the same type of adhesive, and (E) is the case where the areas where conductive adhesive and heat-dissipating adhesive are applied on both sides of the battery module face areas of different adhesives. [Figure 3] Figure 3(A) shows an example of measured values ​​of the time change in the amount of heat generated inside a battery when both terminals of a charged battery module are short-circuited. Figure 3(B) shows an example of measured values ​​of the temperature change at the center of a battery when both terminals of a charged battery module are short-circuited. [Figure 4] Figures 4(A) and (B) show the calculated temperature distribution on the center plane in the thickness direction of a battery cell 10 seconds after short-circuiting both electrodes of a charged battery module in a calculation experiment. (A) shows the results when the adhesive layer of the battery module is uniformly coated with conductive adhesive, and when coated areas of conductive adhesive and heat-dissipating adhesive of various widths on both sides of the battery module face areas coated with the same type of adhesive. (B) shows the results when coated areas of conductive adhesive and heat-dissipating adhesive of various widths on both sides of the battery module face areas coated with different adhesives. [Explanation of Symbols]

[0014] 1…Battery module, 2…Battery cell, 3…Electrode foil, 4+…Positive electrode active material, 4-…Negative electrode active material layer, 5…Separator, 6…Current collector plate, 7…Adhesive layer, 7e…Coated area of ​​conductive adhesive, 7h…Coated area of ​​heat-dissipating adhesive, p…Temperature reference point [Best Mode for Carrying Out the Invention]

[0015] The present invention will be described in detail below with reference to the attached figures, with reference to several preferred embodiments. In the figures, the same reference numerals indicate the same parts.

[0016] Battery module configuration As schematically depicted in Figure 1, in the battery module 1 to which this embodiment is applied, a battery cell 2 is formed by superimposing multiple single cells, each consisting of a positive electrode active material layer 4+ and a negative electrode active material layer 4- coated on the surface of an electrode foil 3, facing each other across an electrolyte layer (a separator 5 immersed in an electrolyte or a solid electrolyte layer). In the battery cell 2 of this embodiment, with the exception of the outermost electrode foils 3 of the two outermost cells, the positive electrode foil and negative electrode foil of each cell form a bipolar electrode, each integrated with the negative electrode foil and positive electrode foil of the adjacent cell, and the cells are connected in series in the battery cell 2. The electrode foils 3, positive electrode active material layer 4+, negative electrode active material layer 4-, electrolyte layer or separator 5 may be of a form that is common in this art. Specifically, to put it simply, the electrode foil 3 may be a commonly used metal foil such as aluminum foil or nickel foil with a thickness of several tens of micrometers; the positive electrode active material layer 4+ may be a mixture of commonly used positive electrode active materials such as NCM (nickel-cobalt-manganate lithium), LFP (lithium iron phosphate), or LMFP (lithium iron manganese phosphate) with a conductive additive such as carbon black and a binder such as PVdF (polyvinylidene fluoride), applied to a layer with a thickness of several tens of millimeters; and the negative electrode active material layer 4- may be a mixture of commonly used negative electrode active materials such as graphite (natural or artificial) with a binder such as SBR / CMC (styrene-butadiene rubber / carboxymethylcellulose), applied to a layer with a thickness of several tens of millimeters. The separator 5 may be formed of a lithium ion permeable resin film with a thickness of approximately 20 μm. The electrolyte filled between the electrode foils is appropriately selected depending on the type of battery. For example, in the case of a non-aqueous lithium-ion battery, it may be a non-aqueous solvent in which LiPF6 (lithium hexafluoride phosphate) is dissolved at 1M in a non-aqueous solvent consisting of a 1:1:1 mixture of EC (ethyl carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate). Although not shown in the diagram, the periphery of the electrode foil 3 and the separator 5 is sealed with a sealing material made of resin.

[0017] The above-described battery cell 2 is housed in an exterior body (not shown). Collector plates 6 are adhered to the electrode foils 3 on both outer surfaces of the battery cell 2 via adhesive layers 7, respectively. The collector plate 6 may be a metallic plate member such as an aluminum plate about 3 mm thick, for example. Typically, the periphery of the collector plate 6 is surrounded by a laminate wrapping material, covering the side surface of the battery cell and sealed at the periphery, whereby the battery cell 2 is sealed in an exterior body composed of the collector plate 6 and the laminate wrapping material.

[0018] In the adhesive layer 6 between the collector plate 6 and the electrode foils 3 on both outer surfaces of the battery cell 2, basically, since it is necessary to electrically conduct the collector plate 6 and the electrode foil 3, a conductive adhesive is used as the adhesive. However, as described in the section of the summary of the invention, the conductive adhesive may not have a very high thermal conductivity. If only such an adhesive is used to form the adhesive layer 7, heat dissipation from the inside of the battery cell may become insufficient. Therefore, in the present embodiment, while ensuring sufficient conductivity between the collector plate 6 and the electrode foil 3, in order to increase the thermal conductivity in the adhesive layer 7, heat-dissipating adhesive application regions (adhesives with low conductivity but high thermal conductivity) are provided in the adhesive layers 7 on both outer surfaces of the battery cell 2, and improvement of the heat dissipation effect from the inside of the battery cell 2 is achieved. That is, in the adhesive layer 7, a conductive adhesive application region and a heat-dissipating adhesive application region are provided. At that time, according to the research of the inventors of the present embodiment, if the conductive adhesive application region and the heat-dissipating adhesive application region are arranged such that at least a part of the region on the other side of the two outer surfaces facing the conductive adhesive application region on one of the two outer surfaces of the battery cell becomes the heat-dissipating adhesive application region, it is found that the heat dissipation amount becomes larger than when all of the adhesives are conductive adhesives, and heat dissipation unevenness in the surface direction of the battery cell disappears. Therefore, in the present embodiment, as schematically depicted in FIG. 1 (see the arrow in the figure), the region of one outer surface of the battery cell facing the portion that is the conductive adhesive application region 7e on one outer surface of the battery cell is arranged with the heat-dissipating adhesive application region 7h.

[0019] In the configuration of the above-described present embodiment, for the conductive adhesive, for example, the volume resistivity is 2.0×10-6 Those with a value below (Ω·m) are selected (the thermal conductivity does not have to be high). "For the heat-dissipating adhesive, for example, those with a thermal conductivity of 2.1 W / (m·K) or more are selected (the electrical conductivity does not have to be high). The application area of the conductive adhesive may be the minimum area that does not affect the battery performance. The thickness of the adhesive layer may be 0.1 to 3 mm, etc.

[0020] Calculation experiment example The effectiveness of this embodiment was confirmed by the following calculation experiment examples. It should be understood that the following experiment examples illustrate the effectiveness of this embodiment and do not limit the scope of the present invention.

[0021] First, prior to the calculation experiment, in a battery module employing the bipolar electrode foil as described above, the time change of the temperature at the center of the battery when the electrodes were short-circuited externally from a charged state was confirmed. Specifically, a battery module in a state of SOC100% was placed in an environment of 25°C, and a resistance of 5 mΩ was connected between the electrodes to short-circuit them, and the temperature at the center portion in the thickness direction of the battery was measured together with the generated heat amount. FIG. 3(A) shows the time change of the generated heat amount from the start of the short circuit, and FIG. 3(B) shows the time change of the temperature at the center portion in the thickness direction of the battery from the start of the short circuit. According to this, under the above conditions, it was found that the temperature became substantially maximum at 10 seconds after the start of the short circuit.

[0022] Therefore, in the calculation experiment for confirming the effectiveness of this embodiment, the temperature distribution in the plane direction of the battery module at the time point 10 seconds after the short circuit of the battery module in which the adhesive layer was formed under various conditions was observed.

[0023] In the calculation, for a 1 / 4 region of the rectangular battery module 1 as shown in FIG. 2(A), the specific heat, thermal conductivity, and density of each part in the battery module with the specifications described below were set. Assuming that Joule heat was generated in the battery cell part due to the short circuit, the temperatures of each reference point p in the plane direction (x direction) at the center in the thickness direction of the battery cell part 2 as depicted in FIG. 2(B) at the time point 10 seconds after the short circuit were calculated using the finite element method.

[0024] The specifications for the battery module model are based on a typical lithium-ion battery as follows (see Figure 1). Positive electrode: LFP (thickness 0.3 mm), Negative electrode: Graphite (thickness 0.3 mm), Separator: PE single layer (thickness 0.02 mm), Electrolyte: EC / DMC / EMC + LiPF6, Electrode foil: Al (40 μm) and Cu (10 μm) laminated together (thickness 0.06 mm), Capacity: 24 Ah, Current collector plate: Al (thickness 0.06 mm).

[0025] Furthermore, the adhesive layer between the electrode foils on both outer surfaces of the cell and the current collector plate was set to a thickness of 1 mm. In the adhesive layer, the following cases were set: as shown in Figure 2(C), conductive adhesive 7e is applied to the entire adhesive layer; as shown in Figure 2(D), conductive adhesive 7e and heat-dissipating adhesive 7h are alternately applied to the electrode foils on both outer surfaces of the battery cell in a predetermined width w, and the same type of adhesive is applied to opposing regions on both outer surfaces; and as shown in Figure 2(E), conductive adhesive 7e and heat-dissipating adhesive 7h are alternately applied to the electrode foils on both outer surfaces of the battery cell in a predetermined width w, and different adhesives are applied to opposing regions on both outer surfaces. The thermal conductivity of the adhesive in the adhesive layer was set to 1.4 W / mK for the conductive adhesive and 3.0 W / mK for the heat-dissipating adhesive.

[0026] Referring to Figures 4(A) and (B), when a heat-dissipating adhesive was applied to the adhesive layer, the temperature inside the battery cell was reduced in both cases compared to when the conductive adhesive 7e was applied to the entire adhesive layer (w=0). Furthermore, when the same type of adhesive was applied to opposing regions on both outer surfaces of the battery cell, as shown in Figure 4(A), temperature unevenness occurred from the center outward, depending on the width of the applied region (w=1cm, 2cm, 3cm). In contrast, when different adhesives were applied to opposing regions on both outer surfaces of the battery cell, as shown in Figure 4(B), the temperature was approximately uniform from the center outward, regardless of the width of the applied region (w=1cm, 2cm, 3cm) (in Figure 4(B), the results for w=1cm, 2cm, and 3cm were all consistent). Specifically, it was shown that when conductive adhesive 7e and heat-dissipating adhesive 7h are alternately applied to the electrode foils on both outer surfaces of a battery cell at an arbitrary width, and different adhesives are applied to opposing regions on both outer surfaces, heat can be dissipated evenly and effectively in the planar direction of the battery module.

[0027] Thus, in the configuration of this embodiment described above, in a battery module in which current collector plates are attached to each of the electrode foils on both sides of a flat-shaped battery cell via adhesive, by using a heat-dissipating adhesive as part of the adhesive and providing an area for applying the heat-dissipating adhesive opposite the area for applying the conductive adhesive, heat can be dissipated evenly and effectively in the planar direction of the battery module.

[0028] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A battery module in which a current collector plate is attached to each of the electrode foils on both outer surfaces of a flat-shaped battery cell via an adhesive, wherein a conductive adhesive application area and a heat dissipation adhesive application area are provided between each of the electrode foils on both outer surfaces and the current collector plate, and at least a portion of the area of ​​the other outer surface that is opposite the conductive adhesive application area on one of the outer surfaces is the heat dissipation adhesive application area.

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