Secondary battery

Abstract

To provide a secondary battery capable of suppressing deterioration in battery performance due to gas generation without passing through a complex operation step.SOLUTION: A secondary battery comprises: at least one battery cell having a negative electrode collector, a negative electrode composition layer, a separator, a positive electrode composition layer, and a positive electrode collector in this order; and an outer casing body that houses at least one battery cell. The negative electrode collector covers a first peripheral part as a peripheral part of the negative electrode composition layer, and comprises a first inclination part that is inclined. The positive electrode collector covers a second peripheral part as a peripheral part of the positive electrode composition layer, and comprises a second inclination part that is inclined. The negative electrode collector and the positive electrode collector can discharge gas generated in the battery cell via the first inclination part and the second inclination part. A foam body is provided between the first inclination part and the outer casing, and between the second inclination part and the outer casing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Secondary batteries such as lithium-ion secondary batteries that can be repeatedly charged and discharged are widely used in various technical fields such as mobile phones, personal computers, electric vehicles, hybrid vehicles, stationary power storage applications, etc. For example, a lithium-ion secondary battery includes a secondary battery cell in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, and an exterior body that covers the secondary battery cell.

[0003] In such a secondary battery, it is known that gas is generated inside the secondary battery cell due to the initial charging, aging, and the like. It is known that the generated gas inhibits the battery reaction and reduces the battery performance. In order to prevent the generated gas from accumulating inside the secondary battery cell, the gas needs to be discharged to the outside. Patent Document 1 describes a configuration for discharging gas. In the technology described in Patent Document 1, a pre-charge is performed before the initial charging of the lithium ion secondary battery 10, and gas is generated inside the lithium ion secondary battery 10. Then, the exterior body 13 of the lithium ion secondary battery 10 is opened, and the gas accumulated inside the lithium ion secondary battery 10 is discharged to the outside. Then, the exterior body 13 is sealed again, and the initial charging of the lithium ion secondary battery 10 is performed.

[0004] However, in the technology described in Patent Document 1, the exterior body 13 had to be opened after pre-charging in order to release the gas generated inside the battery. Also, the exterior body 13 had to be resealed before initial charging, which could complicate the work process. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6637955 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the problems of the conventional techniques as described above. That is, one of the objects of the present invention is to provide a secondary battery capable of suppressing the deterioration of the battery performance due to gas generation without going through such complicated work processes. [Means for solving the problem]

[0007] As a result of extensive research based on the above findings, the present inventors have arrived at the following aspects of the invention. A secondary battery comprising at least one battery cell having, in that order, a negative electrode current collector, a negative electrode composition layer, a separator, a positive electrode composition layer, and a positive electrode current collector, and an exterior housing for housing the at least one battery cell, wherein the negative electrode current collector has a first inclined portion covering a first peripheral portion that is a peripheral portion of the negative electrode composition layer and is inclined, and the positive electrode current collector has a second inclined portion covering a second peripheral portion that is a peripheral portion of the positive electrode composition layer and is inclined, the negative electrode current collector and the positive electrode current collector are capable of releasing gas generated inside the battery cell through the first inclined portion and the second inclined portion, and foam is provided between the first inclined portion and the exterior housing and between the second inclined portion and the exterior housing. Effect of the Invention

[0008] According to the present invention, it is possible to provide a secondary battery capable of suppressing deterioration of battery performance due to gas generation without going through complicated work processes. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a secondary battery according to a first embodiment. [Diagram 2] FIG. 11 is a perspective view illustrating a secondary battery cell according to a second embodiment. [Diagram 3] FIG. 4 is a cross-sectional view illustrating a secondary battery according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a number of embodiments (present embodiments) of the present invention will be described with reference to the drawings. In this specification, the same reference numerals are used for similar components in the drawings. The dimensional ratios of the drawings may be exaggerated for convenience of explanation and may differ from the actual ratios. Planar view indicates that the object is seen from the stacking direction of the secondary battery cells. "And / or" means at least one of the following, and for example, "X and / or Y" means X only, Y only, or X and Y. Unless otherwise specified, the materials exemplified in the following embodiments and modifications may be used alone or in combination of two or more.

[0011] First Embodiment <Secondary battery> A secondary battery according to this embodiment will be described. FIG. 1 is a cross-sectional view showing a secondary battery (secondary battery 100) according to a first embodiment. The secondary battery 100 is used in the form of a battery pack in which a plurality of secondary battery cells (hereinafter simply referred to as battery cells) are combined to form a module. As shown in FIG. 1, the secondary battery 100 includes four layers of stacked secondary battery cells (battery cells 5), a high-voltage tab 50, an exterior body 60, and a foam body 70. Although a case in which a plurality of battery cells 5 (four layers here) are stacked is illustrated, the number of stacked battery cells 5 may be a single one. The number of stacked battery cells 5 is appropriately determined in consideration of battery performance such as a required battery capacity. Hereinafter, an example in which the secondary battery 100 according to this embodiment is configured as a lithium-ion secondary battery will be described.

[0012] The battery cell 5 will be described. As shown in FIG. 1, the battery cell 5 has an elongated elliptical shape with ends slightly protruding toward the left and right in a cross-sectional view. The battery cell 5 includes a positive electrode 1, a negative electrode 2, a separator 30, and a frame 40. The positive electrode 1 includes a positive electrode current collector 10 and a positive electrode composition layer 11 arranged on the lower surface of the positive electrode current collector 10 in the figure (the surface (first surface) on the negative electrode 2 side). The negative electrode 2 includes a negative electrode current collector 20 and a negative electrode composition layer 21 arranged on the upper surface of the negative electrode current collector 20 in the figure (the surface (second surface) on the positive electrode 1 side). In the battery cell 5, the positive electrode composition layer 11 and the negative electrode composition layer 21 are arranged so as to face each other via the separator 30, and the positive electrode 1, the separator 30, and the negative electrode 2 are stacked in this order from the top in FIG. 1.

[0013] The positive electrode collector 10 is a resin collector (resin collector) that has a rectangular shape in a plan view and contains a conductive resin, which is a conductive polymer material. For example, a matrix resin to which a conductive agent is added as necessary can be used as the conductive polymer material of the resin collector. For example, a conductive agent similar to the conductive assistant contained in the coating material that coats the positive electrode active material can be suitably used as the conductive agent constituting the conductive polymer material. The positive electrode collector 10 may further contain a dispersant for the resin collector. The surface of the positive electrode collector 10 may be appropriately plated with metal. The surface of the positive electrode collector 10 has a coated portion where the positive electrode composition layer 11 is disposed and a non-coated portion where the positive electrode composition layer 11 is not disposed. This non-coated portion is also the peripheral portion of the surface of the positive electrode collector 10.

[0014] The negative electrode current collector 20 is a resin current collector that is rectangular in plan view and contains a conductive resin, which is a conductive polymer material. For example, a matrix resin to which a conductive agent is added as necessary can be used as the conductive polymer material of the resin current collector. For example, a conductive agent similar to the conductive assistant contained in the coating material that coats the negative electrode active material can be suitably used as the conductive agent constituting the conductive polymer material. The negative electrode current collector 20 may further contain a dispersant for the resin current collector. The surface of the negative electrode current collector 20 may be appropriately plated with metal. On the surface of the negative electrode current collector 20, there are a coating portion where the negative electrode composition layer 21 is disposed and a non-coated portion where the negative electrode composition layer 21 is not disposed. This non-coated portion is also the peripheral portion of the surface of the negative electrode current collector 20. In the following, the positive electrode current collector 10 and the negative electrode current collector 20 are also simply referred to as electrode current collectors.

[0015] Polyolefin is used as the matrix resin constituting the conductive polymer material. From the viewpoint of electrical stability, it is preferable to use at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO), and it is more preferable to use at least one selected from the group consisting of polyethylene (PE), polypropylene (PP) and polymethylpentene (PMP).

[0016] In the case where a resin collector is formed by adding a conductive agent to a matrix resin, the conductive agent is composed of a conductive filler. The conductive filler may be metals [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.], carbon-based materials [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.)], or mixtures thereof, among which carbon-based materials are preferred. If the conductive filler is a carbon-based material, it is possible to prevent the metals originating from the negative electrode collector 20 and the positive electrode collector 10 from being mixed into the negative electrode active material and the positive electrode active material. In particular, this leads to suppression of characteristic deterioration in the positive electrode active material.

[0017] Such conductive fillers may be used alone or in combination of two or more. The conductive filler may be an alloy or metal oxide of the above-mentioned metal. The conductive filler may be a particulate ceramic material or a resin material coated with a conductive material composed of the above-mentioned metal by plating or the like.

[0018] The positive electrode composition layer 11 has a rectangular shape in a plan view and contains a positive electrode active material. Examples of the positive electrode active material include composite oxides of lithium and transition metals. Examples of the lithium transition metal composite oxides include composite oxides containing one type of transition metal (LiCoO2, LiNiO2, LiAlMnO4, LiMnO2, and LiMn2O4, etc.), composite oxides containing two types of transition metal elements (for example, LiFeMnO4, LiNi 1-x Co x O2, LiMn 1-y Co y O2, LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2) and composite oxides containing three or more metal elements [e.g. LiM a M' b M'' c O2(M, M' and M'' are different transition metal elements and satisfy a+b+c=1. For example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), etc.], lithium-containing transition metal phosphates (e.g., LiFePO4, LiCoPO4, LiMnPO4, and LiNiPO4), transition metal oxides (e.g., MnO2 and V2O5), transition metal sulfides (e.g., MoS2 and TiS2), and conductive polymers (e.g., polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole). The positive electrode active material may be a combination of two or more of the above-mentioned lithium transition metal composite oxides. The lithium-containing transition metal phosphate may be one in which a part of the transition metal site is replaced with another transition metal.

[0019] The positive electrode composition layer 11 may contain, in addition to the positive electrode active material, a coating resin, a conductive assistant such as metal or carbon, an electrolyte solution containing an electrolyte salt, and the like. The positive electrode active material may be coated with a coating material containing a coating resin and a conductive assistant. In addition, the positive electrode composition layer 11 may or may not contain conductive fibers such as carbon fibers.

[0020] The negative electrode composition layer 21 has a rectangular shape in a plan view and includes a negative electrode active material. Examples of the negative electrode active material include carbon-based materials [graphite, hard carbon (hardly graphitizable carbon), amorphous carbon, resin baked bodies (e.g., phenolic resins and furan resins baked and carbonized, etc.), cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), and carbon fibers, etc.], silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composites (carbon particles whose surfaces are coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles whose surfaces are coated with carbon and / or silicon carbide, silicon carbide, etc.), and silicon alloys (silicon- Examples of the conductive material include aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, and silicon-tin alloys), conductive polymers (e.g., polyacetylene and polypyrrole), metals (tin, aluminum, zirconium, and titanium), metal oxides (titanium oxide and lithium-titanium oxide), and metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, and lithium-aluminum-manganese alloys), as well as mixtures of these with carbon-based materials.

[0021] The negative electrode composition layer 21 may contain, in addition to the negative electrode active material, a coating resin, a conductive assistant such as metal or carbon, an electrolyte solution containing an electrolyte salt, and the like. The negative electrode active material may be coated with a coating material containing a coating resin and a conductive assistant. The negative electrode composition layer 21 may or may not contain conductive fibers such as carbon fibers. Hereinafter, the positive electrode composition layer 11 and the negative electrode composition layer 21 are also simply referred to as electrode composition layers.

[0022] The separator 30 has a rectangular shape in a plan view, and may be, for example, a porous sheet made of polymer or fiber that absorbs and retains an electrolytic solution or a gel polymer electrolyte, etc. A nonwoven fabric separator, etc. may also be used.

[0023] The frame 40 is annular in plan view and is provided between the peripheral portion of the surface of the positive electrode current collector 10 and the peripheral portion of the surface of the negative electrode current collector 20. The frame 40 is arranged so as to cover the side portion of the positive electrode composition layer 11 and the side portion of the negative electrode composition layer 21. The frame 40 may be made of any material that is durable against the electrolyte, and is preferably a thermosetting polymer material. An example of the thermosetting polymer material is an epoxy resin that is highly durable and easy to handle. Although not shown in the cross-sectional view of FIG. 1, the frame 40 extends in the front-rear direction (depth direction) and left-right direction of FIG. 1.

[0024] The secondary battery 100 also includes a strong electric tab 50. The strong electric tab 50 is, for example, a substantially plate-shaped metal member (e.g., copper). The strong electric tab 50 is in surface contact with a portion of the current collector of the battery cells 5 located in the lowermost and uppermost layers, and is used to extract current from the stacked battery cells 5. The current collector with which the strong electric tab 50 is in surface contact is also the current collector of the outermost layer.

[0025] The secondary battery 100 also includes an exterior body 60. The exterior body 60 houses the battery cell 5 inside and prevents the intrusion of liquids such as water present outside the exterior body 60. The exterior body 60 can be, for example, an aluminum laminate film or aluminum laminate sheet in which a metal material such as aluminum is covered with an insulating material. The battery cell 5 is placed on the exterior body 60, and the upper and side surfaces of the battery cell 5 are covered and sealed by the exterior body 60, so that the battery cell 5 is suitably housed in the exterior body 60. A part of the high-voltage tab 50 is sealed so as to be exposed from the exterior body 60 and is drawn out to the outside of the exterior body 60. The inside of the exterior body 60 is depressurized relative to atmospheric pressure. The depressurization of the inside of the exterior body 60 facilitates gas release to the outside of the battery cell 5. Here, the atmospheric pressure refers to standard atmospheric pressure (101.325 kPa).

[0026] The secondary battery 100 also includes a foam 70. The foam 70 is housed inside the exterior body 60. The foam 70 is arranged so as to contact the end (periphery (hereinafter also simply referred to as the peripheral part of the battery cell 5)) of the battery cell 5 in a direction intersecting the thickness direction of the battery cell 5. The foam 70 is a molded product formed by finely dispersing gas in a resin material such as polyethylene, polystyrene, polypropylene, or polyurethane. Representative manufacturing methods include an extrusion foaming method and a bead foaming method.

[0027] The materials of the components of the secondary battery 100 are not limited to the above-mentioned materials, and various materials can be used.

[0028] <Resin collector capable of releasing gas> A case where gas is generated inside the battery cell 5 due to the initial charging of the secondary battery 100, aging, or the like will be described. As described above, the battery cell 5 has the positive electrode 1 capable of releasing lithium and the negative electrode 2 capable of absorbing lithium. The battery cell 5 is charged (or discharged) by the movement of lithium from the positive electrode 1 to the negative electrode 2 (or from the negative electrode 2 to the positive electrode 1) via the electrolyte. During the initial charging process, a coating called an SEI (Solid Electrolyte Interphase) coating is formed on the surface of the negative electrode 2 by the decomposition of the electrolyte, etc. Gases such as hydrogen, hydrocarbons, and carbon oxides are generated inside the battery cell 5 due to chemical reactions such as when this SEI coating is formed. The amount of gas generated increases when a predetermined voltage is applied.

[0029] Here, the positive electrode current collector 10 and the negative electrode current collector 20 are resin current collectors containing a conductive resin, which is a conductive polymer material, as described above. The resin used for the positive electrode current collector 10 and the negative electrode current collector 20 has countless fine voids at the molecular level, which allows gas (air) to be released. By using resin current collectors as the positive electrode current collector 10 and the negative electrode current collector 20, when gas is generated inside the battery cell 5, the gas is released to the outside of the battery cell 5 through the surface of the positive electrode current collector 10 and the surface of the negative electrode current collector 20. This prevents inhibition of the battery reaction caused by the gas generated inside the battery cell 5, and maintains the battery performance. In addition, as long as a conductive material has fine voids that allow gas to be released, there is room for it to be used as an electrode current collector.

[0030] <Slope of electrode current collector> The battery cell 5 has a portion (gas release portion) from which gas generated inside is particularly likely to be released, which will now be described in detail.

[0031] As shown in FIG. 1, in the secondary battery 100, a plurality of battery cells 5 (four layers in the illustrated example) are stacked. For example, the upper surface of the positive electrode collector 10 of the second battery cell 5 from the top layer in FIG. 1 is in contact with the lower surface of the negative electrode collector 20 of the first battery cell 5. Similarly, the lower surface of the negative electrode collector 20 of the second battery cell 5 is in contact with the upper surface of the positive electrode collector 10 of the third battery cell 5. Furthermore, these contacting portions are compressed by atmospheric pressure. Of the surfaces of the electrode collectors of each battery cell 5 (the surfaces of the positive electrode collector 10 and the negative electrode collector 20), there is a risk that smooth gas release will be difficult in the upper and lower surface portions that are in a non-exposed state due to contact and compression.

[0032] 1, the thickness of the peripheral portion of the battery cell 5 is adjusted to be tapered. Specifically, the peripheral portion of the battery cell 5 is inclined so that the thickness of the battery cell 5 becomes thinner from the center of the battery cell 5 toward the peripheral portion in a cross-sectional view. With this configuration, the peripheral portion of each battery cell 5 is exposed without contact or pressure.

[0033] In the example of FIG. 1, the total thickness of the negative electrode current collector 20, the negative electrode composition layer 21, the separator 30, the positive electrode current collector 10, and the positive electrode composition layer 11 is thicker than the total thickness of the positive electrode current collector 10, the frame 40, and the negative electrode current collector 20. Therefore, as shown in FIG. 1, the electrode current collector is formed based on the difference in the total thicknesses, and has a slope 5a that is inclined so that the thickness of the battery cell 5 becomes thinner from the center of the battery cell 5 toward the periphery. The slope 5a is an inclined portion that covers the end (peripheral portion) of the electrode composition layer in a direction intersecting the thickness direction of the electrode composition layer. Specifically, the negative electrode current collector 20 covers the peripheral portion (first peripheral portion) of the negative electrode composition layer 21 and has an inclined slope portion (first inclined portion). The positive electrode current collector 10 covers the peripheral portion (second peripheral portion) of the positive electrode composition layer 11 and has an inclined slope portion (second inclined portion). In other words, the peripheral edge of the battery cell 5 has the above-mentioned inclined slope 5a. The slope may be flat, or may be curved in a convex or concave shape.

[0034] The sloped surface 5a is exposed without contact or pressure, and therefore allows gas to be released more smoothly than the upper and lower surface portions of the surface of the electrode current collector of the battery cell 5. Furthermore, while the sloped surface 5a is narrower than the upper and lower surface portions of the surface of the electrode current collector of the battery cell 5, it is provided on the entire peripheral portion (four sides) of the battery cell 5. Therefore, the sloped surface 5a has a sufficiently large area as a gas release portion, allowing gas to be released smoothly. This prevents inhibition of the battery reaction caused by gas generated inside the battery cell 5, and maintains battery performance.

[0035] <Foam> As described above, the secondary battery 100 includes the foam 70. The foam 70 is provided in the space between the slope 5a of the positive electrode current collector 10 and the exterior body 60, and between the slope 5a of the negative electrode current collector 20 and the exterior body 60. The method for providing the foam 70 may be, for example, a method for filling and molding the material of the foam 70 by a predetermined method when the battery cell 5 is covered and sealed with the exterior body 60. The method for providing the foam 70 may be, for example, a method for producing a molded product by previously molding the material of the foam 70 into a predetermined shape (for example, a shape that fits the space) by a known method, and inserting the molded product when the battery cell 5 is covered and sealed with the exterior body 60. The foam 70 may also be inserted into the space by another method. The foam 70 is provided in the space without any gaps, but may be provided in the space with some gaps.

[0036] Since foam 70 is a molded product formed by finely dispersing gas in a specific resin material, there are voids (air bubbles) inside foam 70. Foam 70 is placed so as to contact the periphery of battery cell 5. Therefore, gas released from the periphery of battery cell 5 can be stored in the voids. Note that the number and size of voids in foam 70 may be adjusted depending on the amount of gas generated.

[0037] The foam 70 is preferably a hard molded product. When the battery cell 5 is covered and sealed with the exterior body 60, the inside of the exterior body 60 is depressurized with respect to atmospheric pressure. If the foam 70 is not provided, for example, the exterior body 60 may come into close contact with the slope 5a during depressurization, and the peripheral portion of the battery cell 5 may be deformed. The foam 70 is configured to be able to maintain its own shape even after the pressure inside the exterior body 60 is reduced. By providing such a foam 70, the space inside the exterior body 60 is maintained (kept), making the peripheral portion of the battery cell 5 less likely to deform. In addition, the foam 70 also serves as a buffer material that protects the battery cell 5 from external impacts and the like of the secondary battery 100. This prevents inhibition of the battery reaction caused by the gas generated inside the battery cell 5, and maintains the battery performance. The foam 70 may be compressed to an extent that the hardness can be almost maintained by the depressurization inside the exterior body 60.

[0038] Second Embodiment FIG. 2 is a perspective view showing a secondary battery cell according to a second embodiment. In a plan view, the four corners of the frame 40 are defined as corners, the outer peripheral sides of the corners are defined as corners, and the inner peripheral sides of the corners are defined as corners. For ease of explanation, FIG. 2 shows a state in which a part of the positive electrode current collector 10 is rolled up, and also shows an enlarged view of the corners of the frame 40 (areas surrounded by circles in the figure). Note that the second embodiment is substantially the same as the secondary battery and secondary battery cell (battery cell 5) of the first embodiment, and therefore only the differences will be described and illustrated.

[0039] As shown in FIG. 2, the battery cell 5 has a rectangular parallelepiped shape as a whole. The battery cell 5 includes two of the above-mentioned frames 40. The frames 40 are provided between the non-covered portion (peripheral portion) of the surface of the positive electrode current collector 10 and the non-covered portion (peripheral portion) of the surface of the negative electrode current collector 20. One frame 40 is disposed so as to cover the side surface of the positive electrode composition layer 11, and has an upper surface (third surface) on the side of the surface of the positive electrode current collector 10. The other frame 40 is disposed so as to cover the side surface of the negative electrode composition layer 21 (not shown), and has an upper surface (third surface) on the side of the surface of the negative electrode current collector 20. Grooves 41 are formed in the upper surface (third surface) on the side of the surface of the positive electrode current collector 10 and the upper surface (third surface) on the side of the surface of the negative electrode current collector 20.

[0040] As shown in FIG. 2, the groove 41 is disposed at the corner of the frame body 40 in a plan view and is meandering. Although not shown in FIG. 2, the groove 41 is also formed at the opposite corner of the frame body 40. That is, one frame body 40 has two grooves 41. The groove 41 is formed from corner to corner of the frame body 40, one end of the groove 41 is disposed at the corner of the frame body 40, and the other end of the groove 41 is disposed at the corner of the frame body 40. The groove 41 is meandering like a continuous U-shape that is rotated 90 degrees around the axis counterclockwise or clockwise alternately. The groove 41 is formed by pressing or the like from the upper surface of the frame body 40 in a predetermined depth direction and a predetermined width direction. The cross-sectional shape of the groove 41 is, for example, approximately V-shaped.

[0041] The upper surface of one frame 40 is in contact with the peripheral portion of the surface of the positive electrode current collector 10. The upper surface of the other frame 40 is in contact with the peripheral portion of the surface of the negative electrode current collector 20. As a result, when gas is generated inside the battery cell 5, the gas is released to the outside of the battery cell 5 through the grooves 41. In addition, two grooves 41 are arranged per frame 40, for a total of four grooves on the positive electrode 1 side and the negative electrode 2 side, so that gas can be released efficiently. In addition, since the grooves 41 are formed in the meandering shape, it is difficult for the electrolyte solution and the like to leak from the positive electrode composition layer 11 and the negative electrode composition layer 21.

[0042] Fig. 3 is a cross-sectional view showing a secondary battery according to the second embodiment. As shown in Fig. 3, the secondary battery 100 includes a four-layer stacked rectangular parallelepiped battery cell 5, a high-voltage tab 50, an exterior body 60, and a foam body 70. The frame body 40 of the battery cell 5 includes the groove 41.

[0043] Of the surfaces of the electrode current collectors of each battery cell 5 (the surface of the positive electrode current collector 10 and the surface of the negative electrode current collector 20), the upper and lower surface portions that are not exposed due to contact and pressure may have difficulty in smoothly releasing gas. In addition, the peripheral portion of each battery cell 5 is not exposed due to contact and pressure. However, in this embodiment, when gas is generated inside each battery cell 5, the gas can be released to the outside of the battery cell 5 through the groove 41 of the frame 40. In addition, since the foam 70 is disposed so as to contact the peripheral portion of the battery cell 5, the released gas is stored inside the foam 70. As a result, inhibition of the battery reaction caused by the gas generated inside the battery cell 5 is suppressed, and the battery performance is maintained.

[0044] The groove 41 is configured to be meandering to prevent leakage of the electrolyte, etc., as described above, but may be further configured to prevent leakage. For example, the surface of the groove 41 is provided with a liquid-repellent (water-repellent) coating layer having a property of repelling liquid. By applying a coating agent to the surface of the groove 41 to perform a liquid-repellent treatment, the coating layer (film) formed on the surface of the groove 41 exhibits liquid repellency. This repels the electrolyte, etc., making it even more difficult for the electrolyte to leak, and making it easier to release only gas. Examples of the coating agent include fluorine-based agents such as [product name "Fluorosurf (registered trademark)" manufactured by Fluoro Technology Co., Ltd.] and [product name "Surflon (registered trademark)" manufactured by AGC Seimi Chemical Co., Ltd.]. Other examples of the coating agent include [product name "JC Coat (registered trademark)" manufactured by Taiyo Yuden Chemical Technology Co., Ltd.]. Note that the coating agent may be configured other than the liquid-repellent coating layer.

[0045] <Modification> The frame body 40 may be configured by combining two frame body members each having an L-shape or a U-shape in a plan view. The two frame body members have, for example, the same shape and structure and have concave and convex shapes at both ends. The frame body 40 is configured such that the concave and convex shapes of one frame body member and the concave and convex shapes of the other frame body member are fitted together. By fitting the concave and convex shapes of the frame body members together in this manner, the meandering groove 41 may be formed at the boundary between the two frame body members.

[0046] The frame 40 may have a groove having an uneven shape different from that of the groove 41, which is formed by press working or the like at a position different from that of the groove 41 on the surface of the frame 40. The groove having an uneven shape different from that of the groove 41 may be configured to release gas when it is disposed on the surface (first surface) of the positive electrode current collector 10 and / or the surface (second surface) of the negative electrode current collector 20.

[0047] Although the groove 41 has the above-mentioned serpentine shape formed from corner to corner of the frame 40 in a plan view, it may have a different shape as long as the electrolyte solution and the like are less likely to leak out. For example, the groove 41 may have a zigzag shape formed by zigzagging back and forth from corner to corner of the frame 40 in a plan view. The groove 41 may also have a complex labyrinth shape.

[0048] Although the groove 41 is formed in a predetermined depth direction and a predetermined width direction from the upper surface of the frame 40, other configurations are also acceptable as long as the electrolyte and the like are less likely to leak out. For example, the groove 41 may be provided deeper in the depth direction, or may be provided so as to be wider in the width direction. In addition, there may be gaps scattered between the two frame members, or the two frame members may not be in contact with each other.

[0049] As described above, the secondary battery according to the present embodiment has been described. However, it goes without saying that a person skilled in the art can appropriately add, modify, or omit the present embodiment within the scope of the technical concept thereof.

[0050] The secondary battery has been described as a lithium ion battery. However, it may be other secondary batteries such as a lead acid battery, an all-solid-state battery, a semi-solid battery, a nickel-metal hydride battery, etc. For example, a battery cell of an all-solid-state lithium ion battery uses a solid electrolyte instead of the liquid electrolyte. In this battery cell, the separator 30 is not required, and the positive electrode 1 to the negative electrode 2 are filled with the solid electrolyte. The positive electrode composition layer 11 is in a state in which a positive electrode active material is interposed in this solid electrolyte. The negative electrode composition layer 21 is in a state in which a negative electrode active material is interposed in this solid electrolyte. The details and materials of each component constituting this battery cell are the same as those of each component constituting the battery cell 5 according to this embodiment. [Industrial Applicability]

[0051] By using the secondary battery according to this embodiment in, for example, an electric vehicle or a hybrid vehicle, a long driving distance per charge and a long life can be achieved. [Explanation of symbols]

[0052] 1 positive electrode 2 negative electrode 5 Battery Cells 5a Slope 10 Positive electrode current collector 11 Positive electrode composition layer 20 Negative electrode current collector 21 Negative electrode composition layer 30 Separator 40 Frame 41 Groove 50 High voltage tab 60 Exterior body 70 Foam 100 Secondary battery (lithium ion battery)

Claims

1. At least one battery cell having, in order, a negative electrode current collector, a negative electrode composition layer, a separator, a positive electrode composition layer, and a positive electrode current collector; an exterior body that houses the at least one battery cell; A secondary battery comprising: the negative electrode current collector includes a first inclined portion that covers a first peripheral portion that is a peripheral portion of the negative electrode composition layer and is inclined, the positive electrode current collector includes a second inclined portion that covers a second peripheral portion that is a peripheral portion of the positive electrode composition layer and is inclined, The negative electrode current collector and the positive electrode current collector may release gas generated inside the battery cell through the first inclined portion and the second inclined portion, a foam is provided between the first inclined portion and the exterior body and between the second inclined portion and the exterior body; Secondary battery.

2. the first inclined portion and the second inclined portion are inclined such that a thickness of the battery cell becomes thinner from a center of the battery cell toward a periphery thereof, The secondary battery according to claim 1 .

3. the battery cell includes a frame provided between a peripheral portion of a surface of the negative electrode current collector and a peripheral portion of a surface of the positive electrode current collector, a total thickness of the negative electrode current collector, the negative electrode composition layer, the separator, the positive electrode current collector, and the positive electrode composition layer is greater than a total thickness of the positive electrode current collector, the frame, and the negative electrode current collector; The secondary battery according to claim 1 .

4. The pressure inside the foam is reduced relative to atmospheric pressure. The secondary battery according to claim 1 .

5. at least one battery cell including: a positive electrode having a positive electrode current collector having a first surface, and a positive electrode composition layer provided on the first surface such that a peripheral portion of the first surface is exposed; a negative electrode having a negative electrode current collector having a second surface that serves as the positive electrode, and a negative electrode composition layer provided on the second surface such that a peripheral portion of the second surface is exposed; and a frame provided between the peripheral portion of the first surface and the peripheral portion of the second surface, covering at least a portion of a side surface of the positive electrode composition layer and a side surface of the negative electrode composition layer; an exterior body that houses the at least one battery cell; A secondary battery comprising: the frame has a third surface on the side of the first surface and the side of the second surface, the third surface being provided with a groove extending from an inner peripheral edge to an outer peripheral edge of the frame; A foam body is provided between the third surface of the frame body and the exterior body. Secondary battery.

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