JP2007188746A - Bipolar battery, battery pack, and vehicle mounting their batteries - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery module capable of easily manufacturing by simplifying a series of manufacturing operations, an inexpensive battery pack formed by electrically connecting a plurality of battery modules, and a vehicle mounting their batteries. <P>SOLUTION: A bipolar battery 100 forms a power generation element 160 by alternately stacking a bipolar electrode 230 in which a positive electrode layer 210 is formed on one surface of a current collector 200 and a negative electrode layer 220 on the other side and an electrolyte layer 240 conducting ion exchange between the bipolar electrodes, and the surface roughness of an electrode layer forming part and that of a sealing member sticking part of the current collector are made different. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bipolar battery, an assembled battery, and a vehicle equipped with these batteries, in which the surface roughness of a current collector constituting a bipolar electrode is adjusted.

  In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a stacked bipolar battery that can achieve a high energy density and a high output density.

  A typical bipolar battery includes a battery element in which a plurality of bipolar electrodes are connected in series with an electrolyte layer interposed therebetween. In the bipolar electrode, a positive electrode is formed by providing a positive electrode active material layer on one surface of a current collector, and a negative electrode is formed by providing a negative electrode active material layer on the other surface. A single battery layer is formed by sequentially stacking a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and the single battery layer is sandwiched between a pair of current collectors. Bipolar batteries have the advantage that a current path is short and current loss is small because current flows in the direction of stacking bipolar electrodes in the battery element, that is, the thickness direction of the battery (hereinafter referred to as “stacking direction”).

A metal foil is used for the current collector constituting the bipolar electrode, and the technology (see Patent Document 1) in which the surface roughness Rz of the metal foil is specified to be 3 μm or more, or the surface roughness of the metal foil is 0.1 to A technique (see Patent Document 2) is disclosed in which the thickness is 0.9 μm and the negative electrode current collector is a copper foil or nickel foil obtained by electrolytic plating.
JP 11-297307 A JP-A-5-74479

  In Patent Documents 1 and 2, the surface roughness is defined in order to improve the adhesion of the electrode active material. However, if the surface of the current collector is too rough, the contact resistance increases and the battery characteristics deteriorate. On the other hand, when the battery roughness is emphasized and the surface roughness of the current collector is reduced, the adhesion of the seal member provided so as to surround the periphery of the unit cell layer between the current collectors becomes insufficient.

  The present invention relates to a bipolar battery, an assembled battery, and a battery pack capable of improving the adhesion of a seal member without sacrificing battery characteristics by optimally adjusting the surface roughness of a current collector in a bipolar battery. An object of the present invention is to provide a vehicle equipped with a battery.

To achieve the above object, the present invention provides a bipolar electrode in which a positive electrode layer is formed on one surface of a current collector and a negative electrode layer is formed on the other surface, and an electrolyte that exchanges ions between the bipolar electrodes. In a bipolar battery in which a plurality of layers are alternately stacked to form a power generation element,
The bipolar battery is characterized in that the surface roughness of the electrode layer forming portion of the current collector is different from the surface roughness of the seal member attaching portion.

  According to the present invention, the surface roughness of the electrode layer forming portion of the current collector is different from the surface roughness of the portion where the seal member is applied, and the surface roughness of the portion where the electrode layer is formed and the portion where the seal member is applied is optimum. By adjusting to, the adhesiveness of the seal member can be improved without sacrificing battery characteristics.

  Embodiments of a bipolar battery, an assembled battery, and a vehicle equipped with these batteries according to the present invention will be described below in detail with reference to the drawings. In the drawings cited in the following embodiments, the thickness and shape of each layer constituting the bipolar battery are exaggerated, but this is done to facilitate understanding of the contents of the invention. Yes, it is not consistent with the thickness and shape of each layer of an actual bipolar battery.

(First embodiment)
FIG. 1 is a perspective view showing a bipolar battery according to a first embodiment of the present invention. The bipolar battery 100 has a rectangular flat shape as shown in the figure, and a positive electrode tab 120 </ b> A and a negative electrode tab 120 </ b> B for extracting electric power are drawn out from both sides thereof. The power generation element 160 is wrapped by an outer packaging material (for example, a laminate film) 180 of the bipolar battery 100, and its peripheral four sides are heat-sealed. The power generation element 160 is sealed with the positive electrode tab 120A and the negative electrode tab 120B pulled out. Yes.

  FIG. 2 is a cross-sectional view showing a laminated structure of the bipolar battery 100 of the first embodiment. FIG. 3 shows a manufacturing process of the bipolar battery 100 of the first embodiment, (A) is a cross-sectional view of a current collector, (B) is a cross-sectional view of an electrode material application process, and (C) is a press working process. Sectional drawing, (D) is a sectional view of the sticking step of the seal member, and (F) is a sectional view in a laminated state.

  The bipolar battery 100 according to the first embodiment can be formed using various lamination methods such as a slurry coating method and a printing method. In this embodiment, the power generation element 160 is formed using the slurry coating method. To do.

  The current collector 200 used in the present embodiment is, for example, aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), stainless steel (SUS), molybdenum (Mo), niobium (Nb), or the like. The conductive metal foil is selected from the following. The surface roughness Ra of the metal foil is 1 μm or less.

As shown in FIGS. 3A and 3B, first, positive electrode slurry is applied to the central portion of the current collector (for example, SUS foil) 200 other than the seal member pasting portion, and dried to form the positive electrode layer 210. To do. As the positive electrode slurry, for example, a mixture of a positive electrode active material such as LiMn ₂ O _{4 and} a conductive assistant such as acetylene black, a binder such as PVDF, and a slurry viscosity adjusting solvent such as NMP is used. The coating thickness of the positive electrode slurry is preferably 20 μm or less.

  Next, a negative electrode slurry is applied to the entire opposite surface of the current collector (SUS foil) 200 to which the positive electrode layer 210 is applied, and dried to form the negative electrode layer 220. As the negative electrode slurry, for example, a mixture of a negative electrode active material such as hard carbon, a binder such as PCDF, and a slurry viscosity adjusting solvent such as NMP is used. The coating thickness of the negative electrode slurry is preferably 20 μm or less.

  In this manner, the positive electrode layer 210 and the negative electrode layer 220 are formed on both surfaces of the current collector (SUS foil) 200, whereby the bipolar electrode 230 is formed.

  After the bipolar electrode 230 is formed, as shown in FIG. 3C, the entire surface of the bipolar electrode 230 is pressed (roughened) using roll presses 280A and 280B having a roll surface with a surface roughness Ra of 1 μm or more. Surface processing). Then, the surface roughness Ra of the portion where the surface of the current collector (SUS foil) 200 around the positive electrode layer 210 is exposed is processed to a roughness of 1 μm or more, and this portion is the seal member pasting portion 200A. In the first embodiment, since both the entire surfaces of the bipolar electrode 230 are pressed, portions where the positive electrode layer 210 and the negative electrode layer 220 are formed are also pressed (roughened), but the electrode layer forming portion originally has surface roughness. Therefore, only the density of the positive electrode layer 210 and the negative electrode layer 220 is increased, and the roughness is not affected, and the contact resistance between the electrode layers 210 and 220 and the current collector 200 is reduced.

  Next, as shown in FIG. 3D, a rectangular frame-shaped seal member 260 is applied to the seal member affixed portion 200A that is exposed around the positive electrode layer 210 and has a surface roughness Ra of 1 μm or more. Affix it. As a method for attaching the seal member 260, for example, any method in which a thermoplastic resin is thermally fused or a thermosetting resin is applied and solidified by heating can be used.

Also, using a microporous membrane made of PP or a non-woven fabric separator, seal portions such as silicon rubber having a predetermined height are arranged on both sides of the predetermined portion from the outer periphery of the outer periphery of the separator. The gel electrolyte layer is held in the central portion of the separator by immersing a pregel solution to be the electrolyte layer 240 inside the portion and thermally polymerizing in an inert atmosphere. For example, a polymer (copolymer of polyethylene oxide and polypropylene oxide), EC + DMC (1: 3), 1.0 MLi (C ₂ F ₅ SO ₂ ) ₂ N, and a polymerization initiator (BDK) were mixed in the pregel solution. Use things.

  As shown in FIG. 3 (F), the power generation element 160 is formed by stacking the positive electrode and the negative electrode so that they face each other with the electrolyte layer 240 of the separator therebetween, and the stacking is repeated. Thus, the power generation element 160 in which the five-layer unit cells 150 as shown in FIG. 2 are stacked is formed. In addition, the positive electrode terminal electrode and the negative electrode terminal electrode are prepared by applying the positive electrode layer 210 only on one surface and attaching the seal member 260 or applying the negative electrode layer 220 thereto.

  As described above, the electrolyte layer 240 is preferably formed of a gel solute. By using a gel electrolyte as the electrolyte layer 240, it is possible to prevent leakage, and to prevent a liquid junction, which is a problem peculiar to the dual electrode type secondary battery, to realize a highly reliable stacked battery. Can do.

  Here, the difference between the all solid polymer electrolyte and the polymer gel electrolyte will be described. A polymer gel electrolyte is an all-solid polymer electrolyte such as PEO (polyethylene oxide) containing an electrolyte solution usually used in a lithium ion battery. Moreover, what hold | maintained electrolyte solution in polymer frame | skeleton which does not have lithium ion conductivity like PVDF, PAN, and PMMA also corresponds to a polymer gel electrolyte. The ratio of the polymer and the electrolyte constituting the polymer gel electrolyte is wide. When 100% of the polymer is an all-solid polymer electrolyte and 100% of the electrolyte is a liquid electrolyte, all of the intermediates correspond to the polymer gel electrolyte. On the other hand, the all solid electrolytes include all electrolytes having Li ion conductivity such as polymers or inorganic solids. In the present invention, the solid electrolyte includes all of polymer gel electrolyte, all solid polymer electrolyte, and inorganic solid electrolyte.

  In addition, it is preferable to use a lithium-transition metal composite oxide for the positive electrode active material and a carbon or lithium-transition metal composite oxide for the negative electrode active material, so that a bipolar battery excellent in capacity and output characteristics can be obtained. Can be realized.

  The lowermost negative electrode terminal pole of the power generation element 160 is connected to the negative electrode tab 120B, and the uppermost positive electrode terminal electrode is connected to the positive electrode tab 120A (see FIG. 1). Since the power generating element 160 shown in FIG. 2 has five unit cells 150 connected in series, a voltage five times that of the unit cell 150 appears between the positive electrode tab 120A and the negative electrode tab 120B.

  In the present embodiment, the power generation element 160 is configured with a set of five unit cells 150. However, the number of stacks of the unit cells 150 constituting the power generation element 160 is not limited to the present embodiment. .

  Finally, the separator including the bipolar electrode 230 and the electrolyte layer 240 is covered and sealed with a laminate film 180 as an exterior material, and laminated with the positive electrode tab 120A and the negative electrode tab 120B being pulled out as shown in FIG. The portions on the four sides of the outer periphery of the film 180 are heat-sealed.

  According to the bipolar battery 100 of the first embodiment, the surface roughness of the portion where the electrode layers 210 and 220 of the current collector 200 are formed and the portion 200A of the sticking portion 260 of the seal member 260 are different. Specifically, the positive electrode layer 210 and the negative electrode layer 220 are respectively formed on both surfaces of the current collector 200 having a surface roughness Ra of 1 μm or less before press processing (rough surface processing) (see FIG. 3B). . The reason why the surface roughness Ra of the portions where the positive electrode layer 210 and the negative electrode layer 220 are formed is adjusted to 1 μm or less is that the smaller surface roughness is desirable from the viewpoint of improving battery characteristics. On the other hand, the entire surfaces of the bipolar electrode 230 having the positive electrode layer 210 and the negative electrode layer 220 are pressed (roughened) by roll presses 280A and 280B having a roll surface with a surface roughness Ra of 1 μm or more. The exposed portion of the current collector 200 is processed to a roughness of 1 μm or more (see FIG. 3C). The exposed portion of the current collector 200 becomes a seal member pasting portion 200A. The reason why the surface roughness Ra of the affixed portion 200A of the seal member 260 is adjusted to 1 μm or more is that it is desirable that the surface roughness is rough from the viewpoint of improving adhesion. By using the current collector 200 having different surface roughnesses in the same plane as described above, the surface roughnesses of the portions where the electrode layers 210 and 220 are formed and the portion 200A where the seal member 260 is attached are optimized. The adhesion of the seal member 260 can be improved without sacrificing battery characteristics.

  In the first embodiment, the entire surface of the bipolar electrode 230 only needs to be pressed during the rough surface processing of the seal member pasting portion 200A, so that the processing is not complicated and can be easily realized. Furthermore, in the first embodiment, unlike the second and third embodiments, which will be described later, the roughening is performed after the electrode layers 210 and 220 are formed, so that the electrode layers 210 and 220 can be easily formed.

(Second Embodiment)
4A and 4B show a manufacturing process of the bipolar battery 100A according to the second embodiment of the present invention, in which FIG. 4A is a plan view and a sectional view of a current collector, FIG. 4B is a plan view and a sectional view of a grinding process, (C) is a plan view and a sectional view of the electrode layer forming step, and (D) is a plan view and a sectional view of the sealing material attaching step.

  In the bipolar battery 100A of the second embodiment, a current collector (for example, a SUS foil) formed of the same material as that of the first embodiment and having a surface roughness Ra of 1 μm or less is used (FIG. 4). (See (A)). First, as shown in FIG. 4 (B), a predetermined portion is ground from the outer sides of the outer peripheral portion of one side of the current collector 200 with a file or the like so that the surface roughness Ra becomes 1 μm or more. Process. The roughened portion becomes a seal member pasting portion 200A. Next, as shown in FIG. 4C, the positive electrode slurry is applied to the inner central portion of the seal member pasting portion 200 </ b> A on one side of the current collector 200 and dried to form the positive electrode layer 210. Thereafter, as shown in FIG. 4D, a seal member 260 is attached to the seal member attaching portion 200A with a gap from the positive electrode layer 210 by thermal welding or the like. In the second embodiment, the seal member 260 is pasted so as to protrude from the periphery of the current collector 200.

  Although not shown in the drawings, after applying the seal member 260, the negative electrode slurry is applied to the entire opposite surface of the current collector 200 to which the positive electrode layer 210 has been applied, and dried to form the negative electrode layer 220. Is completed. In the same way as in the first embodiment, the power generation element is formed by laminating the positive electrode and the negative electrode so as to face each other with the electrolyte layer of the separator interposed therebetween, and forming a unit cell. A power generation element having a number of stacks is formed. The lowermost negative electrode terminal pole of the power generation element is connected to the negative electrode tab 120B, the uppermost positive electrode terminal electrode is connected to the positive electrode tab 120A (see FIG. 1), and the bipolar battery 100A of the second embodiment is formed. Complete.

  According to the second embodiment, since a predetermined portion is ground from the outer sides of the outer peripheral portion of one side of the current collector 200 and the surface roughness Ra is set to 1 μm or more, a roll press is performed. Such a large-scale apparatus is not required, can cope with cost reduction, and is easy to manufacture.

(Third embodiment)
FIG. 5 shows a manufacturing process of the bipolar battery 100B according to the third embodiment of the present invention, in which (A) is a plan view and a sectional view of a current collector, (B) is a plan view and a sectional view of a masking process, (C) is a plan view and a cross-sectional view of the surface treatment process, and (D) is a plan view and a cross-sectional view in a state where the mask is removed.

  In the bipolar battery 100B of the third embodiment, a current collector (for example, a SUS foil) that is formed of the same material as that of the first and second embodiments and has a surface roughness Ra of 1 μm or less is also used. (See FIG. 5A). First, as shown in FIG. 5B, masking is performed on a portion of the current collector 200 that does not require surface treatment on one side. Specifically, a rectangular mask 290 is attached to the central portion excluding a predetermined portion from the outer sides of the outer peripheral portion of the current collector 200. Next, as shown in FIG. 5C, a surface treatment is performed on a portion exposed from the mask 290, that is, a predetermined portion from the outer sides of the outer peripheral portion of the current collector 200, and the surface roughness Ra becomes 1 μm or more. To roughen the surface. The surface treatment may be a mechanical treatment such as sand blasting, wire brush, or file, in addition to chemical treatment such as etching. The portion roughened by this surface treatment becomes a seal member pasting portion 200A. The material of the mask 290 is appropriately selected according to the type of surface treatment to be roughened. After completion of the surface treatment, cleaning is performed as necessary, and as shown in FIG. 5D, the mask 290 attached to the central portion inside the seal member attaching portion 200A on one side of the current collector 200 is removed. .

  Although not shown, the positive electrode slurry 210 is formed by applying the positive electrode slurry to the portion where the mask 290 has been removed, that is, the central portion inside the seal member attaching portion 200A, and drying. Thereafter, as in the second embodiment, a seal member is attached to the seal member attaching portion 200A with a gap from the positive electrode layer 210 by thermal welding or the like. After the sealing member is pasted, the negative electrode slurry is applied to the entire opposite surface of the current collector 200 to which the positive electrode layer 210 has been applied, and dried to form the negative electrode layer 220, thereby completing the bipolar electrode. As in the first and second embodiments, the power generation element is formed by stacking the positive electrode and the negative electrode so that the electrolyte layer of the separator faces each other to form a unit cell, and repeating such stacking A power generation element having a desired number of layers is formed. The lowermost negative electrode terminal pole of the power generation element is connected to the negative electrode tab 120B, the uppermost positive electrode terminal electrode is connected to the positive electrode tab 120A (see FIG. 1), and the bipolar battery 100B of the third embodiment is formed. Complete.

  According to the third embodiment, since masking is performed on a portion of the current collector 200 that does not require surface treatment, the surface treatment can be selectively performed only on the seal member pasting portion 200A to roughen the surface. It is easy to manufacture because it can cope with cost reduction.

  In the first to third embodiments described above, the seal member pasting portion 200A is roughened, but instead of roughening the surface roughness, at least the seal member pasting portion 200A is perforated. Further, processing such as scaly processing or baking of fine powder having the same composition as the material of the current collector 200 may be performed.

(Fourth embodiment)
Bipolar batteries 100 (100A, 100B) described above are connected in series or in parallel to form a battery module 250 (see FIG. 6), and a plurality of battery modules 250 are connected in series or in parallel. Thus, the assembled battery 300 can also be formed. The illustrated battery module 250 is obtained by stacking a plurality of the bipolar batteries 100 and storing them in a module case, and connecting the bipolar batteries 100 in parallel. FIG. 6 shows a plan view (FIG. A), a front view (FIG. B), and a side view (FIG. C) of an assembled battery 300 according to the fourth embodiment of the present invention. The battery modules 250 are connected to each other using an electrical connection means such as a bus bar, and the battery modules 250 are stacked in a plurality of stages using a connection jig 310. How many bipolar batteries 100 are connected to create the battery module 250 and how many battery modules 250 are stacked to create the assembled battery 300 are determined by the battery capacity of the vehicle (electric vehicle) to be mounted. Depending on the output.

  As described above, the assembled battery 300 in which a plurality of battery modules 250 are connected in series and parallel can obtain high capacity and high output, and the reliability of each battery module 250 is high. It is possible to maintain long-term reliability. Further, even if some of the assembled battery modules 250 fail, repair can be performed by simply replacing the failed part.

(Fifth embodiment)
FIG. 7 is a schematic configuration diagram showing an automobile 400 as a vehicle according to the fifth embodiment of the present invention. The above-described bipolar battery 100, battery module 250, and / or assembled battery 300 can be mounted on a vehicle such as an automobile or a train and used as a power source for driving an electric device such as a motor.

  In order to mount the assembled battery 300 on the electric vehicle 400, the battery pack 300 is mounted under the seat in the center of the vehicle body of the electric vehicle 400 as shown in FIG. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and driving performance.

  In the present invention, not only the assembled battery 300 but also only the battery module 250 may be mounted depending on the intended use, or the assembled battery 300 and the battery module 250 may be mounted in combination. . Further, as the vehicle on which the assembled battery or the assembled battery module of the present invention can be mounted, the above-described electric vehicle and hybrid car are preferable, but are not limited thereto.

  The present invention can be effectively used in the field of bipolar batteries.

1 is a perspective view showing a bipolar battery according to a first embodiment of the present invention. It is sectional drawing which shows the laminated structure of the bipolar battery of 1st Embodiment. FIGS. 3A and 3B are cross-sectional views of a current collector, FIG. 3B is a cross-sectional view of an electrode material application step, and FIG. Sectional drawing of a process, FIG.3 (D) is sectional drawing of the sticking process of a sealing member, FIG.3 (F) is sectional drawing of a lamination | stacking state. 4A and 4B show a manufacturing process of a bipolar battery according to a second embodiment of the present invention, in which FIG. 4A is a plan view and a sectional view of a current collector, and FIG. 4B is a plan view and a sectional view of a grinding process. 4 (C) is a plan view and a cross-sectional view of the electrode layer forming step, and FIG. 4 (D) is a plan view and a cross-sectional view of the sealing material attaching step. FIG. 5A shows a plan view and a sectional view of a current collector, FIG. 5B is a plan view and a sectional view of a masking step, and shows a manufacturing process of a bipolar battery according to a third embodiment of the present invention. 5 (C) is a plan view and a cross-sectional view of the surface treatment process, and FIG. 5 (D) is a plan view and a cross-sectional view in a state where the mask is removed. It is a schematic block diagram of the assembled battery which concerns on the 4th Embodiment of this invention. It is a figure which shows the state by which the assembled battery which concerns on the 5th Embodiment of this invention was mounted in the vehicle.

Explanation of symbols

100, 100A, 100B bipolar battery,
120A positive electrode tab,
120B negative electrode tab,
150 cells,
160 power generation elements,
180 exterior material,
200 current collector,
200A seal member pasting part,
210 positive electrode layer,
220 negative electrode layer,
230 bipolar electrodes,
240 electrolyte layer,
250 battery module,
260 sealing member,
280A, 280B roll press,
290 mask,
300 battery packs,
310 connection jig,
400 vehicles.

Claims (7)

A bipolar electrode in which a positive electrode layer is formed on one surface of the current collector and a negative electrode layer is formed on the other surface, and a plurality of electrolyte layers that perform ion exchange between the bipolar electrodes are alternately stacked. In the bipolar battery forming the power generation element,
A bipolar battery characterized in that the surface roughness of the electrode layer forming portion of the current collector is different from that of the seal member attaching portion.   2. The bipolar battery according to claim 1, wherein the surface roughness of the electrode layer forming portion of the current collector is 1 μm or less.   3. The bipolar battery according to claim 1, wherein a surface roughness of a portion where the seal member is attached to the current collector is 1 μm or more. 4.   A surface roughness of at least a seal member pasting portion of a current collector having a surface roughness of 1 μm is roughened to adjust the surface roughness of the seal member pasting portion to 1 μm or more, and then a sealant is pasted on the seal member pasting portion The bipolar battery according to any one of claims 1 to 3.   The entire current collector on which the positive electrode layer and the negative electrode layer are formed is pressed by a roll press having a surface roughness of 1 μm or more, and the surface roughness of the seal member pasting portion is adjusted to 1 μm or more. 4. The bipolar battery according to 4.   An assembled battery comprising a plurality of the bipolar batteries according to claim 1 connected to each other.   A vehicle comprising the bipolar battery according to claim 1 or the assembled battery according to claim 6 as a power source.

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