JP5327016B2 - Battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve cooling efficiency unevenness of a plurality of battery cells in a battery pack using the battery cells which have terminals on both ends in a longitudinal direction. <P>SOLUTION: A battery module includes the battery cells with terminals on both ends of the same in a longitudinal direction, and a resin cover layer covering an outer circumference surface of the battery cells and provided with electric insulation and thermal conductivity functions. The resin cover layer has contact faces which make plane contact with resin cover layers of other adjoining battery modules, and recessed grooves as continuous extensions of the contact faces, and when the battery pack arrangement is made, tunnel-like cooling passages are formed by a plurality of recessed grooves. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a battery module constituting one unit of an assembled battery used in a hybrid vehicle or an electric vehicle.

  Nickel / hydrogen secondary batteries, lithium ion secondary batteries, and the like used as drive power sources for electric vehicles are required to have a high energy density and are required to have a small mounting space. Therefore, it is common to use a battery pack in which a plurality of single battery cells are assembled. For example, several tens to several tens of V single battery cells having a rectangular parallelepiped shape are connected in series, and these are put in one package to form an assembled battery. This assembled battery is mounted, for example, in the lower part of the rear seat, the trunk room, or the like.

  By the way, the performance and life of the assembled battery greatly depend on the temperature environment, and the deterioration is remarkable at a high temperature. Therefore, a cooling passage communicating with the atmosphere is formed on the surface of the single battery cell, and air in the passenger compartment is introduced into the cooling passage, or the air from the air conditioner is forcibly introduced.

  On the other hand, in a nickel-hydrogen secondary battery or the like, it is inevitable that the unit cell having a rectangular parallelepiped shape expands during charging and the widest side surface expands outward in an arc shape. If it becomes like this, in the assembled battery which assembled | stacked the single battery cell which makes a rectangular parallelepiped shape, the wall surfaces which oppose may contact in a small contact area, and a big stress may concentrate on a contact part.

  Therefore, for the purpose of uniforming the internal pressure of each single battery cell and making the charge / discharge characteristics of each single battery cell uniform, the single battery cells are arranged in a state in which a predetermined load is applied and restrained under pressure. ing. For example, in an assembled battery device introduced in Japanese Patent Application Laid-Open No. 2009-176464, single battery cells and plate-like heat conducting members are alternately arranged, and one constraining plate is placed on each end in the thickness direction. In addition, the two restraining plates are tightened in the direction approaching each other by the restraining rod. By tightening the two constraining plates in a direction approaching each other, the plurality of single battery cells can be brought close to each other via the heat conducting member, and expansion can be regulated by applying a load to each single battery cell.

  Further, according to this assembled battery device, the soft heat conductive member is compressed by the single battery cells on both sides, and the contact surface of the heat conductive member is in close contact with the widest side surface of the single battery cell. The heat of the single battery cell conducted from the close contact surface of the heat conducting member is transferred from the matrix made of a soft material having thermal conductivity and electrical insulation to the fiber member, and is transferred in the length direction of the fiber to be the heat radiating surface. And is radiated from the heat radiation surface to the heat radiation space. JP-A-2000-306560 describes a battery pack in which single battery cells are in close contact with each other through silicone rubber.

  As described above, in the case of a rectangular unit battery cell, it can be brought into close contact via a plate-like heat conductive member or silicone rubber, and expansion can be prevented by heat radiation. However, in the case of a cylindrical round single battery cell, another device is required to dissipate heat.

  For example, in Japanese Patent Application Laid-Open No. 2007-066773, a plurality of round unit cells are adjoined in a parallel posture in a state of being accommodated in a heat conduction cylinder, and adjacent heat conduction cylinders are connected by a thermal runaway prevention wall. An assembled battery is described in which a part of the surface of the heat conducting cylinder is cut away to form a heat dissipation region. According to this assembled battery, heat radiation can be regulated by the thermal runaway prevention wall and heat can be radiated in the heat radiation area, so that the heat of the single battery cell can be regulated to move to the adjacent single battery cell, and thermal runaway can be prevented. Can be suppressed.

JP 2009-176464 A JP 2000-306560 A Japanese Patent Laid-Open No. 2007-066773

  However, in the assembled battery described in Patent Document 3, since the plurality of single battery cells are arranged in the heat dissipation area, the most upstream single battery cell is efficiently cooled when the cooling air is supplied. As a result, the temperature of the cooling air rises, so that there is a problem that the cooling efficiency is lower in the downstream unit battery cell. That is, the variation in cooling between the single battery cells becomes large, and since the single battery cell that is difficult to be cooled becomes a resistor, the performance of the entire assembled battery is deteriorated in accordance with the characteristics of the single battery cell that is most difficult to be cooled.

  The present invention has been made in view of such circumstances, and in an assembled battery using battery cells having terminals at both ends in the longitudinal direction, it is possible to uniformly cool by eliminating variations in cooling efficiency of a plurality of battery cells. Doing so is an issue to be solved.

A feature of the battery module of the present invention that solves the above-mentioned problems is comprised of a battery cell having terminals at both ends in the longitudinal direction, and a resin cover layer that is coated on the outer peripheral surface of the battery cell and has electrical insulation and thermal conductivity. The battery module is a battery module formed by stacking a plurality of layers so that the central axis directions are parallel to each other, and the resin cover layer contacts the resin cover layer of another adjacent battery module. The resin cover layer is composed of a matrix having electrical insulation and a filler having a higher thermal conductivity than the matrix. , filler oriented in the direction from the surface of the battery cell without a short fiber form the contact surface, contact surface each other when the plurality of battery modules is the battery assembly is stacked adjacent with contacts From the number of grooves in the cooling passage of the tunnel-shaped is formed.

  According to the battery module of the present invention, the contact surfaces of the resin cover layer are in contact with each other when the battery module is assembled. Since this resin cover layer has electrical insulation and thermal conductivity, the electrical insulation is satisfied, and the temperature difference between the battery cells is reduced by thermal conduction. In addition, the battery cell can be cooled via each resin cover layer by circulating a refrigerant such as the atmosphere through the tunnel-like cooling passage. Therefore, the variation in cooling efficiency is eliminated, and each battery cell in the assembled battery can be cooled uniformly, so that the life of the charge / discharge characteristics can be extended.

It is a perspective view of the battery module which concerns on one Example of this invention. It is sectional drawing of the battery module which concerns on one Example of this invention. It is sectional drawing of the metal mold | die which manufactures the battery module which concerns on one Example of this invention. It is a perspective view of the assembled battery which consists of a battery module which concerns on one Example of this invention. It is a perspective view of the battery module which concerns on the 2nd Example of this invention. It is a perspective view of the assembled battery which consists of a battery module which concerns on the 2nd Example of this invention. It is a perspective view of the battery module which concerns on the 3rd Example of this invention. It is a perspective view of the assembled battery which consists of a battery module which concerns on the 3rd Example of this invention. It is a front view of the assembled battery which consists of a battery module which concerns on the 3rd Example of this invention. It is a front view of the assembled battery which consists of a battery module which concerns on the 4th Example of this invention.

  The battery module of the present invention includes a battery cell and a resin cover layer. The battery cell has terminals at both ends in the longitudinal direction, for example, round or square in cross section, and various secondary batteries such as nickel metal hydride battery and lithium ion battery can be used.

  The resin cover layer is coated on the outer peripheral surface of the battery cell and has electrical insulation and thermal conductivity. As this resin cover layer, a layer composed of a matrix having electrical insulation and a filler contained in the matrix and having a higher thermal conductivity than the matrix can be used. As the matrix having electrical insulation, thermoplastic resins such as polypropylene, polyethylene, ABS, polystyrene, polycarbonate, and acrylic resin, or thermosetting resins such as epoxy resin, phenol resin, and melamine resin can be used. In addition, EPDM, natural rubber, thermoplastic elastomer, or the like may be used if the shape rigidity can be secured by the filler.

  As the filler, one having electrical insulation and higher thermal conductivity than the matrix is used. Such fillers include carbon fillers such as carbon black, carbon fiber, petroleum coke, graphite, and carbon nanotubes, or alumina, zirconia, magnesia, aluminum nitride, boron nitride, silicon nitride, silicon carbide, boron carbide, etc. Ceramics can be used. While the thermal conductivity of the matrix is generally less than 1 W / m · K, the thermal conductivity of carbon-based fillers and ceramics mostly exceeds 1 W / m · K, and many of them exceed 100 W / m · K. Therefore, both can be suitably used.

  As the amount of the filler increases, the thermal conductivity improves, but on the other hand, the elasticity of the resin cover layer decreases. Accordingly, the carbon filler is preferably in the range of 5 to 40% by volume, and the ceramic filler is preferably in the range of 5 to 60% by volume, although it varies depending on the type of matrix and filler. It is particularly preferable to use a mixed filler of carbon fibers that are easily oriented by a magnetic field application molding method described later and ceramic powder that is a diamagnetic material. As the carbon fiber, a pitch-based carbon fiber having a higher thermal conductivity than the PAN-based carbon fiber is preferable.

  The resin cover layer has a contact surface that comes into surface contact with the resin cover layer of another adjacent battery module, and a concave groove that extends continuously from the contact surface. When a plurality of battery modules are stacked to form an assembled battery, the contact surfaces come into contact with each other, and a tunnel-like cooling passage is formed from a plurality of adjacent concave grooves.

  The resin cover layer has a prismatic shape such as a regular triangle, square, or regular hexagon in cross section. For example, when the resin cover layer has a square pillar shape with a square cross section, a battery cell is arranged at the center of the axis to constitute the battery module of the present invention. The four flat surfaces extending in parallel to the axial direction of the battery cells serve as contact surfaces. When assembled, the battery cells contact adjacent battery modules at the contact surfaces.

  For example, in the case of a prismatic resin cover layer having a square cross section, at least one concave groove orthogonal to the axial direction may be formed on at least two of the four contact surfaces parallel to each other. . If it does in this way, when it is set as an assembled battery, the recessed groove | channel of adjacent battery modules will connect, and the tunnel-shaped channel | path orthogonal to an axial direction will be formed. In this case, it is preferable to form a plurality of concave grooves in two parallel contact surfaces of the resin cover layer of one battery module.

  Moreover, if a groove extending parallel to the axial direction of the battery cell is formed at the four corners where the four contact surfaces intersect, the grooves between the adjacent four battery modules when assembled into a battery pack are formed. Are connected to each other to form a tunnel-shaped passage extending parallel to the axial direction. By circulating a refrigerant such as the atmosphere through the tunnel-shaped passage, the four adjacent battery modules can be uniformly and efficiently cooled. In this way, since the refrigerant can flow along the axial direction of the battery cell, the cooling efficiency is improved as compared with the case where the concave groove orthogonal to the axial direction is formed.

  To cover the battery cell with the resin cover layer, a method of storing the battery cell in a separately formed resin cover layer can be adopted, but the battery cell and the resin are removed in order to eliminate the air layer serving as a heat insulating layer. It is desirable to be in close contact with the cover layer. Therefore, it is desirable to use a method in which the battery cells are arranged in a mold for forming the resin cover layer and the resin cover layer is integrally formed.

  When molding a resin cover layer from a molding material containing a matrix and a filler, it is desirable to mold while applying a magnetic field. In this way, since the filler is oriented along the magnetic field lines, a cluster in which the filler powder is arranged along the magnetic field lines is formed in the resin cover layer. Therefore, heat becomes easy to move through the cluster, thermal conductivity is improved, and heat dissipation is also improved. Since the optimum value of the magnetic field strength varies depending on the viscosity of the molding material, the aspect ratio of the filler powder, etc., it is necessary to determine the optimum value by trial and error within the above-described content range. A strong magnetic field of 1 Tesla or higher is preferable.

  Further, it is also preferable to use a short fiber shape as the filler powder. This is because the short fiber powder is more easily oriented in the longitudinal direction than the particulate powder by applying a magnetic field, and the thermal conductivity in the longitudinal direction is higher than that in the short direction. Such short fiber shaped fillers include ultra-high molecular weight polyethylene fibers with a thermal conductivity of about 60 W / mK in the longitudinal direction, aluminum fibers with a thermal conductivity of about 240 W / mK, and a thermal conductivity of about 1015 W. / mK alumina fiber, aluminum nitride fiber with the same thermal conductivity of about 300 to 400 W / mK, titanium fiber with the same thermal conductivity of about 22 W / mK, boron nitride fiber with the same thermal conductivity of about 250 W / mK, etc. It can be illustrated. Among them, ultrahigh molecular weight polyethylene fibers having the same thermal conductivity of about 60 W / mK are particularly preferable materials because they have electrical insulation properties.

  The orientation direction of the filler in the resin cover layer is preferably oriented at least in a direction orthogonal to the axial direction of the battery module, and is preferably oriented radially around the battery cell. For example, if the resin cover layer is integrally formed with the battery cell as the N pole and the mold as the S pole, the filler can be easily oriented radially.

  Hereinafter, the present invention will be described specifically by way of examples.

  FIG. 1 shows a battery module according to an embodiment of the present invention. This battery module includes a battery cell 1 having a cylindrical shape and a resin cover layer 2 coated on the outer peripheral surface of the battery cell 1. The battery cell 1 is a lithium ion battery, with a positive electrode exposed at one end and a negative electrode exposed at the other end.

  The resin cover layer 2 has a shape in which four corners of a prism having a square cross section are scraped into a circular arc shape, and four long planes extending in parallel to the axial direction of the battery cell 1 corresponding to the four sides of the square. 20 and four concave grooves 21 having a circular arc cross section formed between adjacent long planes 20. As shown in the cross section of FIG. 2, the resin cover layer 2 is made of an epoxy resin matrix 22 and an ultrahigh molecular weight polyethylene fiber (“Dyneema” manufactured by Toyobo Co., Ltd.) having a thermal conductivity of about 60 W / mK. ) Short fibers 23. The short fibers 23 are oriented radially around the battery cell 1.

  This battery module was manufactured as follows. First, a molding material comprising 50% by volume of the short fiber 23 is prepared, which is composed of the short fiber 23 of ultra high molecular weight polyethylene fiber (“Dyneema” manufactured by Toyobo) and an epoxy resin. As shown in FIG. 3, the outer cylinder 10 of the battery cell 1 is placed in a mold 3 composed of an upper mold 30 and a lower mold 31, and the molding material is melted and injection molded into a cavity 32 so that the outer cylinder 10 is integrated. The resin cover layer 2 is formed.

  At the time of molding, magnets are arranged so that the inside of the outer cylinder 10 has an N pole and the outer periphery of the cavity 32 has an S pole, and molding is performed while applying a 2 Tesla magnetic field to the cavity 32. The short fibers 23 contained in the molding material are oriented in the longitudinal direction in the direction of the magnetic field, and are oriented radially around the battery cell 1. After molding, an electrode material and an electrolyte material are sealed in the outer cylinder 10, and a positive electrode and a negative electrode are formed at both ends to form a battery module.

  As shown in FIG. 4, the obtained battery modules are stacked in a rectangular parallelepiped shape so that the long flat surfaces 20 of adjacent battery modules come into contact with each other, and fastened with a band (not shown) to form an assembled battery. The In the assembled battery, the long flat surfaces 20 are brought into contact with each other and are in close contact with each other, and a plurality of tunnel-like cooling passages 24 are formed by combining four concave grooves 21 and opening at both ends. The battery pack is housed in a casing 4 that is open so that both battery cells 1 are connected in series as shown by the wavy line in FIG. 4 and both end faces having openings of the electrode terminals and the cooling passage 24 are exposed. used.

  That is, according to the assembled battery using the battery module of this embodiment, the battery modules are in close contact with each other, and the resin cover layer 2 has high thermal conductivity due to the radially oriented short fibers 23. Further, each battery module is surrounded by four cooling passages 24 extending parallel to the axial direction of the battery cell 1. Therefore, if cooling air is supplied to the cooling passage 24, the variation in the cooling efficiency of the plurality of battery cells arranged in each battery module can be eliminated and the cooling can be performed uniformly, thereby extending the life of the charge / discharge characteristics. Can do. Further, since the assembled battery has a rectangular outer shape, the assembling property is improved.

  FIG. 5 shows a battery module of this embodiment, and FIG. 6 shows an assembled battery formed by stacking the battery modules. The battery module of the present embodiment includes a battery cell 1 similar to that of the first embodiment, and a resin cover layer 5 covered on the outer peripheral surface of the battery cell 1.

  The resin cover layer 5 is formed of a prism having a substantially square cross section, and a long flat surface 50 is formed on a pair of side surfaces facing each other, and a pair of side surfaces intersecting the long flat surface 50 is on the axial direction of the battery cell 1. A plurality of intersecting grooves 51 are formed respectively. The concave groove 51 is open to the long flat surface 50 on both sides. The resin cover layer 5 is formed of the same matrix and short fibers as in Example 1, and the short fibers are radially oriented with the battery cell 1 as the center.

  This battery module is laminated in the vertical direction so that the concave grooves 51 of adjacent battery modules face each other and the surfaces other than the concave grooves 51 are in close contact with each other, and the long flat surfaces 50 are in close contact with each other to open the concave grooves 51. The assembled battery shown in FIG. 6 is formed by laminating in the lateral direction so that the two communicate with each other. In this assembled battery, a plurality of tunnel-like cooling passages 52 are formed in which the concave grooves 51 communicate with each other in the lateral direction. This assembled battery is used by being housed in a casing that is open so that both battery cells 1 are connected in series as in Example 1 and both end faces having openings of electrode terminals and cooling passages 52 are exposed. .

  That is, according to the assembled battery using the battery module of this embodiment, the battery modules are in close contact with each other, and the resin cover layer 5 has high thermal conductivity due to the radially oriented short fibers. Further, each battery module is surrounded by a plurality of cooling passages 52. Therefore, the variation in the cooling efficiency of the plurality of battery cells 1 arranged in each battery module is eliminated, and the battery cells 1 can be uniformly cooled, so that the life of the charge / discharge characteristics can be extended. Further, since the assembled battery has a rectangular outer shape, the assembling property is improved.

  FIG. 7 shows a battery module of this example, and FIG. 8 shows an assembled battery in which the battery modules are stacked. The battery module of the present embodiment includes a battery cell 1 similar to that of the first embodiment, and a resin cover layer 6 coated on the outer peripheral surface of the battery cell 1.

  The resin cover layer 6 is a prism having a regular hexagonal cross section. A long flat surface 60 is formed on each of three pairs of side surfaces facing each other, and a circular arc shape extending from one end surface to the other end surface at a portion where the long flat surfaces 60 intersect each other. Each of the concave grooves 61 is formed. The resin cover layer 5 is formed of the same matrix and short fibers as in Example 1, and the short fibers are radially oriented with the battery cell 1 as the center.

  As shown in FIG. 8, a plurality of the battery modules are stacked to form an assembled battery so that the long flat surfaces 60 of adjacent battery modules come into contact with each other. In this assembled battery, the long flat surfaces 60 are in contact with each other and are in close contact with each other. As shown in FIG. 9, a plurality of tunnel-shaped cooling passages 62 are formed by combining three concave grooves 61 and opening at both ends. This battery pack is used with the battery cells 1 connected in series as shown by the wavy line in FIG.

  That is, according to the assembled battery using the battery module of the present embodiment, the battery modules are in close contact with each other, and the resin cover layer 6 has high thermal conductivity due to radially oriented short fibers. Further, each battery module is surrounded by a plurality of cooling passages 62 extending parallel to the axial direction of the battery cell 1. Therefore, the variation in the cooling efficiency of the plurality of battery cells 1 arranged in each battery module is eliminated, and the battery cells 1 can be uniformly cooled, so that the life of the charge / discharge characteristics can be extended.

  FIG. 10 shows a front view of an assembled battery in which the battery modules of this example are stacked. The battery module of the present embodiment includes a battery cell 1 similar to that of the first embodiment and a resin cover layer 7 coated on the outer peripheral surface of the battery cell 1.

  The resin cover layer 7 is a prism having a regular triangular cross section. A long flat surface 70 is formed on three side surfaces, and a concave groove 71 having a circular arc cross section extending from one end surface to the other end surface is formed at a portion where the long flat surfaces 70 intersect. Each is formed. The resin cover layer 7 is formed of the same matrix and short fibers as in Example 1, and the short fibers are radially oriented with the battery cell 1 as the center.

  As shown in FIG. 10, a plurality of battery modules are stacked to form an assembled battery so that the long planes 70 of adjacent battery modules come into contact with each other. In this assembled battery, the long flat surfaces 70 come into contact with each other and are in close contact with each other, and a plurality of tunnel-shaped cooling passages 72 are formed by combining six concave grooves 71 and opening at both ends. This battery pack is used with the battery cells 1 connected in series as shown by the wavy line in FIG.

  That is, according to the assembled battery using the battery module of this embodiment, the battery modules are in close contact with each other, and the resin cover layer 7 has high thermal conductivity due to the radially oriented short fibers. Further, each battery module is surrounded by three cooling passages 72 extending in parallel to the axial direction of the battery cell 1. Therefore, the variation in the cooling efficiency of the plurality of battery cells 1 arranged in each battery module is eliminated, and cooling can be performed uniformly.

  Further, according to the assembled battery using the battery module of the present embodiment, the cross-sectional area of the cooling passage 72 can be made larger than that of the other embodiments, so that the ventilation resistance is reduced and the cooling efficiency is improved.

  By stacking a plurality of battery modules of the present invention into an assembled battery, it can be used for home appliances, personal computers, etc., in addition to hybrid vehicles, plug-in hybrid vehicles, electric vehicles, and the like.

1: Battery cell 2: Resin cover layer
20, 50, 60, 70: Long flat surface (contact surface)
21,51,61,71: Groove
22: Matrix
23: Short fiber
24,52,62,72: Cooling passage

Claims (5)

A battery cell having terminals at both ends in the longitudinal direction and a resin cover layer coated on the outer peripheral surface of the battery cell and having electrical insulation and thermal conductivity, and a plurality of such that the central axis directions are parallel to each other A battery module that is assembled into a battery pack by being laminated,
The resin cover layer has a contact surface that comes into surface contact with the resin cover layer of another adjacent battery module, and a concave groove that extends continuously to the contact surface.
The resin cover layer includes an electrically insulating matrix and a filler that is contained in the matrix and has a higher thermal conductivity than the matrix, and the filler has a short fiber shape and extends from the surface of the battery cell to the corresponding contact surface. Oriented in the direction to go,
A battery module characterized in that when a plurality of battery modules are stacked to form an assembled battery, corresponding contact surfaces come into contact with each other, and a tunnel-like cooling passage is formed from a plurality of adjacent concave grooves.   The battery module according to claim 1, wherein the concave groove extends in parallel with a central axis direction of the battery cell.   The cross section of the resin cover layer cut by a plane orthogonal to the central axis direction of the battery cell has a polygonal shape, and the concave groove having a circular arc cross section is formed at a corner of the polygonal cross section. The battery module according to claim 2. The battery module according to claim 3, wherein the polygonal cross section of the resin cover layer is a square. The battery module according to claim 3, wherein the polygonal cross section of the resin cover layer is a regular hexagon.

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