Battery

Abstract

This invention provides a battery that enhances safety by suppressing particle detachment from electrodes while forming them using a dry process. [Solution] A battery comprising a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode each have a current collector and a composite layer formed on the current collector and containing an active material and a binder, and at least one of the composite layers of the positive electrode and the negative electrode further contains particulate inhibitors 7 that inhibit current flow at the positive electrode or the negative electrode when the positive electrode or the negative electrode reaches a predetermined temperature or higher, and the inhibitors 7 have a detachment suppression structure 72 that suppresses detachment from the composite layer.

Description

Technical Field

[0001] The present invention relates to a battery.

Background Art

[0002] In recent years, batteries such as lithium-ion secondary batteries have been suitably used as power sources for driving vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). For this type of battery, a design has been made to enhance safety so that the current can be interrupted during abnormal heat generation due to overcharging or the like (see, for example, Patent Documents 1 to 3).

[0003] The battery described in Patent Document 1 includes a positive electrode including a first positive electrode active material layer formed on a positive electrode current collector and a second positive electrode active material layer formed on the first positive electrode active material layer. The first positive electrode active material layer contains a volume expansion resin that expands in volume at a high temperature during overcharging, and the volume expansion resin acts as an insulating layer by melting and expanding at a high temperature to interrupt the current.

[0004] The battery described in Patent Document 2 includes an active material layer containing a thermally expandable carbon material. The thermally expandable carbon material expands at a high temperature to increase the internal resistance of the battery and interrupt the current.

[0005] The battery described in Patent Document 3 includes an active material layer containing a thermal expansion powder that causes volume expansion at a predetermined temperature or higher.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The active material layers described in Patent Documents 1 to 3 are formed by coating a slurry, in which the active material and particles such as volume-expanding resin are dispersed in a dispersion medium, onto a current collector and drying it. Such wet processes are costly in terms of the recovery of the solvent used and the energy required for drying, so dry processes that do not use solvents are attracting attention. In a dry process, a mixed powder containing the active material and a binder is rolled, and a composite film made of the mixed powder bonded or bound by the binder is adhered to the current collector. However, when an active material layer containing particles such as volume-expanding resin is formed by a dry process, there is a concern that the particles will not be easily fixed to the composite film by the binder, causing them to detach from the composite film and preventing the desired function from being performed.

[0008] This invention has been made in view of the above circumstances, and aims to provide a battery that enhances safety by suppressing particle detachment from the electrodes while forming the electrodes by a dry process. [Means for solving the problem]

[0009] The characteristic configuration of the battery according to the present invention for achieving the above objective is: A battery comprising a positive electrode and a negative electrode, The positive electrode and the negative electrode each comprise a current collector and a composite layer formed on the current collector, which includes an active material and a binder. At least one of the composite material layers of the positive electrode and the negative electrode further contains particulate inhibitors that inhibit current flow at the positive electrode or the negative electrode when the positive electrode or the negative electrode reaches a predetermined temperature or higher. The distinguishing feature of the inhibitor is that it has a delamination-preventing structure that suppresses its detachment from the composite layer.

[0010] According to the above-described characteristic configuration, even if the composite layer containing the inhibitor is formed by roll molding or the like, the detachment suppression structure prevents the inhibitor from detaching from the composite layer, thus allowing a sufficient amount of inhibitor to be included in the composite layer. For this reason, even when the composite layer is formed on the current collector by a dry process, it is a highly safe battery that can inhibit current flow at the positive or negative electrode when the temperature exceeds a predetermined level.

[0011] Further characteristic features of the battery according to the present invention are: The distinguishing feature of the inhibitor is that it is a thermally expandable particle that expands in volume above the predetermined temperature.

[0012] According to the above characteristic configuration, when the positive or negative electrode reaches a predetermined temperature or higher, the thermally expandable particles expand in volume, physically separating the active materials that are in contact with each other, or the active materials from the current collector. This inhibits current flow at the positive or negative electrode, suppressing malfunctions such as battery rupture or damage caused by abnormal heat generation, and thereby enhancing safety.

[0013] Further characteristic features of the battery according to the present invention are: The aforementioned inhibitor consists of an outer shell made of resin material and a binder dissolving solution sealed inside.

[0014] According to the above characteristic configuration, when the positive or negative electrode reaches a predetermined temperature or higher, the outer shell expands and ruptures, or the outer shell ruptures due to the increase in internal pressure caused by the vaporization of the binder dissolution liquid, causing the binder dissolution liquid sealed inside the inhibitor to leak into the asphalt mixture layer. As a result, the binder in the asphalt mixture layer dissolves due to the leaked binder dissolution liquid, increasing the electrical resistance between the active materials and thereby inhibiting current flow at the positive or negative electrode.

[0015] Further characteristic features of the battery according to the present invention are: The aforementioned detachment prevention structure is a covering portion that covers the inhibitory material, The coating portion contains a binder.

[0016] According to the above characteristic configuration, it becomes possible to fix the inhibitor in the composite material layer by the coating portion containing the binder. As a result, the dropout of the inhibitor from the composite material layer is suppressed, so that even when the composite material layer is formed on the current collector by a dry process, when the positive electrode or the negative electrode reaches a predetermined temperature or higher, the energization in these can be inhibited and the safety can be enhanced.

[0017] A further characteristic configuration of the battery according to the present invention is The coating portion further includes a conductive material.

[0018] According to the above characteristic configuration, an increase in electrical resistance due to the addition of the inhibitor to the composite material layer can be suppressed. Further, by using a fibrous substance such as carbon nanotubes as the conductive material, the conductive material is likely to adhere to or entangle with the active material and the binder, so that it is also possible to suppress the dropout of the inhibitor from the composite material layer.

[0019] A further characteristic configuration of the battery according to the present invention is The aspect ratio of the inhibitor is 3 or more.

[0020] According to the above characteristic configuration, when forming the composite material layer, it is easy to orient the inhibitor so that the longitudinal direction of the inhibitor is parallel to the horizontal plane of the current collector. Therefore, when the positive electrode or the negative electrode reaches a predetermined temperature or higher, it is easy to peel the active material from the current collector. As a result, it is possible to suppress the occurrence of problems such as rupture and breakage of the battery due to abnormal heat generation and enhance the safety.

Effects of the Invention

[0021] As described above, according to the battery according to the present invention, it is possible to suppress the dropout of particles from the electrode and enhance the safety while forming the electrode by a dry process.

Brief Description of the Drawings

[0022] [Figure 1] It is an exploded perspective view of a secondary battery. [Figure 2] It is a perspective view showing an electrode body with a part developed. [Figure 3] This is a schematic diagram showing the arrangement of the positive electrode, negative electrode, and separator. [Figure 4] This is a cross-sectional view of the inhibitor according to the first embodiment. [Figure 5] This is a cross-sectional view of the inhibitor according to the second embodiment. [Figure 6] This is a cross-sectional view of an inhibitor according to another embodiment. [Modes for carrying out the invention]

[0023] Hereinafter, a battery according to an embodiment of the present invention will be described with reference to the drawings. In the following description, a lithium-ion secondary battery will be used as an example. Furthermore, in order to clarify the explanation, the descriptions and drawings below have been simplified as appropriate.

[0024] [First Embodiment] [Overview of secondary battery 1] Figure 1 is an exploded perspective view of a secondary battery 1 equipped with an electrode body 20. As shown in Figure 1, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 12, battery terminals PS and NS consisting of metal external terminals 25 and 26 and current collector terminals 30 and 31, and an electrode body 20. The secondary battery 1 is a sealed type secondary battery in which the electrode body 20 and current collector terminals 30 and 31 are housed inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 12, and then an electrolyte is injected into the inside of the case body 11.

[0025] [Configuration of battery case 10] As shown in Figure 1, the battery case 10 consists of a case body 11 with a roughly rectangular parallelepiped shape and an open top, and a sealing plate 12 that seals the opening of the case body 11. In this embodiment, both the case body 11 and the sealing plate 12 are made of aluminum, but are not limited to this. Various metals and alloys can be appropriately selected for the case body 11 and the sealing plate 12 depending on the type and application of the battery.

[0026] In this embodiment, the sealing plate 12 has a shape corresponding to the shape of the opening of the case body 11 and is configured to seal the opening of the case body 11.

[0027] [Battery terminal configuration PS, NS] In this embodiment, the secondary battery 1 is equipped with a positive external terminal 25 and a negative external terminal 26 as external terminals, and a positive current collector terminal 30 and a negative current collector terminal 31 as current collector terminals. The positive battery terminal PS is composed of the positive external terminal 25 and the positive current collector terminal 30, and the negative battery terminal NS is composed of the negative external terminal 26 and the negative current collector terminal 31. In this embodiment, the positive external terminal 25 and the positive current collector terminal 30 are made of aluminum, and the negative external terminal 26 and the negative current collector terminal 31 are made of copper, but the materials of these terminals are not particularly limited, and various metals and alloys with good conductivity can be used.

[0028] Furthermore, in this embodiment, the secondary battery 1 includes a positive electrode insulating member (not shown), a negative electrode insulating member (not shown), a positive electrode gasket 32, and a negative electrode gasket 33, all of which are made of insulating material. In this embodiment, PFA resin is used as the insulating material, but the invention is not limited to this.

[0029] The positive electrode current collector terminal 30 has a positive electrode current collector portion 30a extending downward from the back surface of a flat surface (not shown). The negative electrode current collector terminal 31 has a negative electrode current collector portion 31a extending downward from the back surface of a flat surface (not shown). The tip of the positive electrode current collector portion 30a is joined to a positive electrode terminal joint portion 21, which will be described later, and the tip of the negative electrode current collector portion 31a is joined to a negative electrode terminal joint portion 22, which will be described later.

[0030] Although a detailed explanation will be omitted, in the secondary battery 1 of this embodiment, the positive electrode external terminal 25 and the negative electrode external terminal 26 are insulated from the sealing plate 12 by a positive electrode gasket 32 ​​and a negative electrode gasket 33, respectively, and the positive electrode current collector terminal 30 and the negative electrode current collector terminal 31 are insulated from the sealing plate 12 by a positive electrode insulating member and a negative electrode insulating member, respectively.

[0031] [Configuration of electrode body 20] The electrode body 20 is composed of a positive electrode 4, a negative electrode 5, a separator 6, etc. The electrode body 20 may be a laminate formed by stacking the positive electrode 4 and the negative electrode 5 with the separator 6 in between, or it may be a wound body formed by stacking long strip-shaped positive electrode 4 and negative electrode 5 with the same strip-shaped separator 6 in between, winding them up, and compressing them into a flat shape. The electrode body 20 according to this embodiment is a wound body as shown in Figure 2, for example. A positive electrode terminal joint portion 21 to which the positive electrode current collector terminal 30 is joined is formed on one end of the electrode body 20 in the winding axis direction, and a negative electrode terminal joint portion 22 to which the negative electrode current collector terminal 31 is joined is formed on the other end.

[0032] In this embodiment, the electrode body 20 is housed inside the case body 11 in a position where its thickness and longitudinal directions are parallel to the horizontal direction, while covered with an insulating film. Furthermore, the electrode body 20 and the case body 11 are insulated from each other by an insulating film (not shown).

[0033] As shown in Figures 2 and 3, the positive electrode 4 of the electrode body 20 is a strip-shaped electrode having a positive electrode current collector 41 (an example of a current collector) and a positive electrode composite layer 42 (an example of a composite layer) formed on both sides of the positive electrode current collector 41. The positive electrode current collector 41 is, for example, aluminum foil. An uncoated portion 43 is formed on one end of the positive electrode current collector 41 in the longitudinal direction, where the positive electrode composite layer 42 is not formed. In the secondary battery 1 of this embodiment, the portion of the electrode body 20 consisting of the uncoated portion 43 is used as the positive electrode terminal joint portion 21. The positive electrode composite layer 42 is obtained by bonding a composite film that forms the positive electrode composite layer 42 onto the positive electrode current collector 41.

[0034] The negative electrode 5 of the electrode body 20 is a strip-shaped electrode having a negative electrode current collector 51 (an example of a current collector) and a negative electrode composite material layer 52 (an example of a composite material layer) formed on both sides of the negative electrode current collector 51. The negative electrode current collector 51 is, for example, copper foil. An uncoated portion 53 is formed on the other longitudinal end of the negative electrode current collector 51, which is located on the opposite side of one longitudinal end of the positive electrode current collector 41, where the negative electrode composite material layer 52 is not formed. In the secondary battery 1 of this embodiment, the portion of the electrode body 20 consisting of the uncoated portion 53 is used as the negative electrode terminal joint 22, similar to the positive electrode terminal joint 21. The negative electrode composite material layer 52 is obtained by bonding a composite material film that forms the negative electrode composite material layer 52 onto the negative electrode current collector 51.

[0035] The separator 6 is positioned to insulate the positive electrode composite layer 42 of the positive electrode 4 from the negative electrode composite layer 52 of the negative electrode 5. In this embodiment, the separator 6, negative electrode 5, separator 6, and positive electrode 4 are stacked in this order, and in a view in the stacking direction, the positive electrode composite layer 42 and the negative electrode composite layer 52 overlap with the separator 6. The separator 6 can be made of an insulating material that allows ions to pass through (for example, a porous insulating resin material).

[0036] [Composition of the positive electrode composite layer] The positive electrode composite layer 42 contains a positive electrode active material and a binder. The positive electrode active material can be any known compound that can be used in the positive electrode 4. The binder is not limited to any particular type as long as it can bond the active materials together or between the active materials and the current collector, for example, fine powder of PVdF-based material, PTFE, polyolefin, etc. Two or more of these may be used as the binder. Because the positive electrode composite layer 42 contains a binder, the positive electrode composite layer 42 can be formed on the positive electrode current collector 41 by a dry process rather than a wet process. The positive electrode composite layer 42 may also contain additives such as conductive additives.

[0037] The positive electrode active material is preferably present in an amount of 50 to 98% by weight of the total weight of the positive electrode composite layer 42, more preferably 70 to 98% by weight, and more preferably 90 to 98% by weight. The binder is preferably present in an amount of 1 to 30% by weight of the total weight of the positive electrode composite layer 42, more preferably 1 to 10% by weight, and more preferably 1 to 3% by weight.

[0038] The positive electrode composite layer 42 further contains particulate inhibitor 7 that inhibits current flow at the positive electrode 4 when the positive electrode 4 reaches a predetermined temperature (e.g., 80°C) or higher. As shown in Figure 4, the inhibitor 7 has thermally expandable resin particles 71 that expand in volume above the predetermined temperature, and a covering portion 72 that covers the particles 71. The particles 71 can be, for example, polyethylene, polypropylene, polyethylene vinyl acetate, etc. The particles 71 may be selected from more than one of these types. By including the inhibitor 7 in the positive electrode composite layer 42, when the positive electrode 4 reaches a predetermined temperature or higher, the particles 71 expand in volume, separating the positive electrode active materials that are in contact with each other in the positive electrode composite layer 42, or suppressing contact between the positive electrode active materials and the positive electrode current collector 41, thereby inhibiting current flow. This suppresses abnormal heat generation in the secondary battery 1 and enhances safety.

[0039] The particle size of the inhibitor 7 is preferably less than or equal to the particle size of the positive electrode active material, for example, 1 mm or less, and preferably 50 to 100 μm. The shape of the inhibitor 7 is not particularly limited and may be spherical or angular, but it is preferable that it be ellipsoidal. If the inhibitor 7 is ellipsoidal, when rolling the composite film containing the inhibitor 7 and positive electrode active material to form a film, or when bonding the composite film onto the positive electrode current collector 41, the longitudinal direction of the inhibitor 7 is easily oriented parallel to the upper surface of the positive electrode current collector 41. Therefore, the presence of the inhibitor 7 between the positive electrode current collector 41 and the positive electrode active material makes it easier to separate the positive electrode active material from the positive electrode current collector 41 due to the volume expansion of the particles 71. If the inhibitor 7 is ellipsoidal, its aspect ratio is preferably 3 or greater. If the aspect ratio is 3 or greater, it is easier to orient the longitudinal direction of the inhibitor 7 parallel to the upper surface of the positive electrode current collector 41, and it is possible to suppress an increase in the resistance of the secondary battery 1. Furthermore, if the aspect ratio is too high, it may become difficult to separate the positive electrode active materials in a direction parallel to the upper surface of the positive electrode current collector 41, so the aspect ratio should be 10 or less.

[0040] The coating portion 72 covering the particles 71 contains a binder that can adhere to or bind to other components in the positive electrode composite layer 42. Since the coating portion 72 is fixed to the positive electrode composite layer 42 by the binder, the detachment of the inhibitor 7 from the positive electrode composite layer 42 is suppressed. In other words, the coating portion 72 according to this embodiment functions as a detachment suppression structure that suppresses the detachment of the inhibitor 7 from the positive electrode composite layer 42. Because the inhibitor 7 has a detachment suppression structure, even if the positive electrode composite layer 42 is formed on the positive electrode current collector 41 by a dry process, the inhibitor 7 can be included in the positive electrode composite layer 42, and the inhibitor 7 can exert its function in the secondary battery 1. The binder is not limited to any specific material as long as it can adhere to the active materials to each other or to the active materials and to the current collector, similar to the binder described above. For example, fine powder of PVdF-based material, PTFE, polyolefin, etc. can be used. Two or more types selected from these may be used as the binder. It is best to use a binder different from the one used for binding.

[0041] The coating portion 72 is obtained by immersing or coating the particles 71 in a binder such as PVDF after molding the particles 71 and then drying it. The thickness of the coating portion 72 is not particularly limited, but if it is too thick, the volume of the inhibitor 7 will increase, so it is preferable that the thickness be such that it can adhere to or bind to other components in the positive electrode composite layer 42.

[0042] The coating portion 72 may further contain a conductive material. The conductive material may be, for example, carbon nanotubes or carbon nanohorns. By including a conductive material in the coating portion 72, the increase in electrical resistance caused by adding the inhibitor 7 to the positive electrode composite layer 42 can be suppressed. Furthermore, by using a fibrous material such as carbon nanotubes as the conductive material, the conductive material is more likely to become entangled with other particles in the positive electrode composite layer 42, and the detachment of the inhibitor 7 is more easily suppressed. In other words, if the conductive material is fibrous, it also contributes to suppressing detachment. The conductive material is fixed in a shape that becomes entangled on the surface of the coating portion 72 by applying the conductive material to the inhibitor 7 on which the coating portion 72 is formed.

[0043] The inhibitor 7 is preferably present in an amount of 1 to 30% by weight relative to the total weight of the positive electrode composite layer 42, more preferably 1 to 10% by weight, and more preferably 1 to 5% by weight.

[0044] [Composition of the negative electrode composite layer] The negative electrode composite layer 52, like the positive electrode composite layer 42, contains a negative electrode active material, the binder described above, and the inhibitor 7 described above. The inclusion of the binder in the negative electrode composite layer 52 allows the negative electrode composite layer 52 to be formed on the negative electrode current collector 51 by a dry process rather than a wet process. Furthermore, the inclusion of the inhibitor 7 in the negative electrode composite layer 52 inhibits the conductivity of the negative electrode 5 due to the volume expansion of the inhibitor 7 when the negative electrode 5 exceeds a predetermined temperature, thereby enhancing the safety of the secondary battery 1. In addition, the presence of a covering portion 72 in the inhibitor 7 prevents the inhibitor 7 from falling off the sheet-like negative electrode 5.

[0045] In the negative electrode composite layer 52, similar to the positive electrode composite layer 42, the negative electrode active material is preferably present in an amount of 50 to 98% by weight relative to the total weight of the negative electrode composite layer 52, more preferably 70 to 98% by weight, and more preferably 90 to 98% by weight. The binder is preferably present in an amount of 1 to 30% by weight relative to the total weight of the negative electrode composite layer 52, more preferably 1 to 10% by weight, and more preferably 1 to 3% by weight. The inhibitor 7 is preferably present in an amount of 1 to 30% by weight relative to the total weight of the negative electrode composite layer 52, more preferably 1 to 10% by weight, and more preferably 1 to 5% by weight.

[0046] [Method for manufacturing electrodes] Next, the manufacturing method of the electrode body 20 will be described. First, the manufacturing methods of the positive electrode 4 and negative electrode 5 of the electrode body 20 will be described. The positive electrode 4 and negative electrode 5 are obtained by adhering a strip-shaped composite film, which forms the positive electrode composite layer 42 or the negative electrode composite layer 52, to the positive electrode current collector 41 or the negative electrode current collector 51. The composite film is formed by dry mixing the active material of the positive or negative electrode, a binder, and an inhibitor 7 using a mixing device such as a mixer or blender, and then rolling the mixed mixture with a calender roll. In the composite film formation process, the active materials are adhered or bound to each other by the binder contained in the composite film. At this time, the coating portion 72 of the inhibitor 7 is also adhered or bound to the active material, and the inhibitor 7 is fixed in the composite film. Therefore, even if the composite film is bonded to the positive electrode current collector 41 or the negative electrode current collector 51 and the positive electrode composite layer 42 or the negative electrode composite layer 52 is formed by a dry process, the detachment of the inhibitory material 7 from the positive electrode composite layer 42 and the negative electrode composite layer 52 can be suppressed.

[0047] The strip-shaped composite film is cut to a predetermined size to match the size of the current collectors 41 and 51 of the positive electrode 4 or negative electrode 5, and then bonded to the surface of the current collectors 41 and 51 by, for example, a hot roll press. This forms the positive electrode 4 or negative electrode 5. Subsequently, the positive electrode 4 and negative electrode 5 are stacked via a separator 6, and the electrode body 20 is obtained by winding them together (see Figure 2).

[0048] [Second Embodiment] The inhibitor 7 according to the second embodiment will be described with reference to Figure 5. The inhibitor 7 according to the second embodiment consists of an outer shell 73 made of resin material, a binder dissolving solution 74 sealed inside the outer shell 73, and a covering portion 72 that covers the surface of the outer shell 73. The other components are the same as in the first embodiment, so the same components as in the first embodiment will not be described.

[0049] The outer shell 73 is made of a material that expands in volume above a predetermined temperature, similar to the particles 71. For example, polyethylene, polypropylene, polyethylene vinyl acetate, etc., can be used. The outer shell 73 has a space inside, and the binder dissolving solution 74 is sealed in this space. The shape of the outer shell 73 is not particularly limited as long as it has a space inside; it may be spherical, ellipsoidal, or non-spherical, such as an amorphous shape. It may also have multiple spaces inside. The particle size of the outer shell 73 is preferably less than or equal to the particle size of the active material of the positive electrode 4 or the negative electrode 5, for example, 1 mm or less, and preferably 50 to 100 μm.

[0050] The binder dissolving solution 74 is a polar solvent such as n-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), or dimethyl sulfoxide (DMSO). By contacting the binder, such as PVdF, contained in the composite material layers 42 and 52 of the positive electrode 4 or negative electrode 5, the binder is dissolved, thereby breaking the bond between the active materials of the positive or negative electrode.

[0051] The binder dissolving solution 74 leaks into the composite layers 42 and 52 of the positive electrode 4 or negative electrode 5 when the positive electrode 4 or negative electrode 5 reaches a predetermined temperature or above, either by the outer shell 73 expanding and rupturing, or by the outer shell 73 rupturing due to the increase in internal pressure caused by the vaporization of the binder dissolving solution 74. This increases the internal resistance of the composite layers 42 and 52 of the positive electrode 4 or negative electrode 5, blocking the conductive path. The thickness of the outer shell 73 should be such that it expands above a predetermined temperature or ruptures due to internal pressure.

[0052] The surface of the outer shell 73 is covered by a covering portion 72. Therefore, the covering portion 72 acts as a detachment prevention structure, suppressing the detachment of the inhibitor 7 from the composite layers 42 and 52. As a result, even when the composite layers 42 and 52 are formed by a dry process, the inhibitor 7 can be included in the composite layers 42 and 52, thereby improving the safety of the secondary battery 1.

[0053] The inhibitor 7 according to the second embodiment is obtained by forming an outer shell 73 containing a binder dissolving solution 74 inside, and then coating the surface of the outer shell 73 with a coating portion 72. The outer shell 73 may be formed by an interfacial polymerization method or the like. Specifically, the binder dissolving solution 74 may be dispersed in a dispersion medium, and the atomized binder dissolving solution 74 may be coated with the outer shell 73.

[0054] [Another embodiment] [1] In the above embodiment, the inhibitor 7 is included in both the positive electrode composite layer 42 and the negative electrode composite layer 52, but the inhibitor 7 may be included in either one of them. Either the positive electrode composite layer 42 or the negative electrode composite layer 52 may be formed by a wet process instead of a dry process. That is, it may be obtained by coating a slurry in which the active material of the positive or negative electrode and a binder are dispersed in a solvent onto the current collectors 41, 51 of the positive electrode 4 or the negative electrode 5 and drying it.

[0055] [2] In the above embodiment, the structure for preventing the detachment of the inhibitor 7 is the covering portion 72, but as shown in Figure 6, the detachment prevention structure may be a protrusion 75 formed on the surface of the particle 71. The protrusion 75 has a conical shape with an apex angle of 90 degrees or less. Because the inhibitor 7 has a protrusion 75, the protrusion 75 is more likely to catch on the active material or binder of the positive or negative electrode, thereby preventing the inhibitor 7 from detaching from the composite material layers 42, 52 of the positive electrode 4 or the negative electrode 5. The protrusion 75 may be formed by pouring resin material into a mold capable of forming the protrusion 75, or it may be formed by covering the surface of the particle 71 with the covering portion 72 and fibrousizing the surface.

[0056] [3] In the second embodiment described above, the outer shell 73 is made of a material that expands in volume above a predetermined temperature, but the outer shell 73 may be made of a material that does not expand in volume easily. In this case as well, by changing the thickness of the outer shell 73 and the type of binder dissolving solution 74, the outer shell 73 can be ruptured by the increase in internal pressure due to the vaporization of the binder dissolving solution 74, and the binder dissolving solution 74 can be leaked into the composite layers 42 and 52 in the same manner as described above.

[0057] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Explanation of Symbols]

[0058] 1: Secondary battery (battery) 4: Positive electrode 5: Negative electrode 7: Inhibitor 41: Positive electrode current collector (current collector) 42: Positive electrode composite material layer (compound material layer) 51: Negative electrode current collector (current collector) 52: Negative electrode composite material layer (compound material layer) 71: Particle 72: Covering part 73: Outer shell 74: Binder dissolving solution

Claims

1. A battery comprising a positive electrode and a negative electrode, The positive electrode and the negative electrode each comprise a current collector and a composite layer formed on the current collector, which includes an active material and a binder. At least one of the composite material layers of the positive electrode and the negative electrode further contains particulate inhibitors that inhibit current flow at the positive electrode or the negative electrode when the positive electrode or the negative electrode reaches a predetermined temperature or higher. The aforementioned inhibitor has a delamination-preventing structure that suppresses delamination from the composite layer.

2. The battery according to claim 1, wherein the inhibitor is a thermally expandable particle that expands in volume at a predetermined temperature or higher.

3. The battery according to claim 1, wherein the inhibitor comprises an outer shell made of a resin material and a binder dissolving solution sealed inside.

4. The aforementioned detachment prevention structure is a covering portion that covers the inhibitory material, The battery according to claim 2 or 3, wherein the covering portion includes a binder.

5. The battery according to claim 4, wherein the covering portion further comprises a conductive material.

6. The battery according to claim 4, wherein the aspect ratio of the inhibitor is 3 or more.

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