JP2022104116A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery which can suppress a short circuit owing to a foreign metal, and which can suppress the heat generation owing to a short circuit even if being short circuited.SOLUTION: An all-solid battery comprises an electrode body having a positive electrode collector foil, a positive electrode layer, a solid electrolyte layer, a negative electrode layer and a negative electrode current collector foil which are laminated in this order. In the all-solid battery, the positive electrode layer is laminated so as to be disposed on an inner side with respect to the solid electrolyte layer and the negative electrode layer; an insulator layer is disposed on a part of a face of the positive electrode collector foil on a positive electrode layer side, and the part is opposed to at least an end portion of the solid electrolyte layer and negative electrode layer; and the insulator layer has an adhesive layer and a ceramic layer, and the ceramic layer is stuck to the positive electrode collector foil through the adhesive layer.SELECTED DRAWING: Figure 1

Description

The present application relates to an all-solid-state battery.

In the field of lithium-ion batteries, the development of all-solid-state batteries equipped with solid electrolytes is being promoted from the viewpoint of improving safety as compared with non-aqueous electrolyte batteries.

Normally, an all-solid-state battery includes an electrode body in which a positive electrode current collector foil, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector foil are laminated in this order, and from the viewpoint of suppressing Li precipitation, a positive electrode body is provided. The layers are arranged and laminated inside the solid electrolyte layer and the negative electrode layer. Then, since there is a gap between the positive electrode foil and the solid electrolyte layer and the negative electrode layer, there is a possibility that the positive electrode current collector foil and the solid electrolyte layer or the negative electrode layer may come into contact with each other due to vibration or impact to cause a short circuit. There is.

In response to this problem, Patent Documents 1 to 5 describe an insulating layer made of an insulating resin on the surface of the positive electrode collector foil on the positive electrode layer side from the viewpoint of preventing contact between the positive electrode current collector foil and the solid electrolyte layer and the negative electrode layer. And the technology of covering the side surface of the electrode body with an insulating resin are disclosed.

Japanese Unexamined Patent Publication No. 2020-1253536 Japanese Unexamined Patent Publication No. 2015-103249 Japanese Unexamined Patent Publication No. 2018-49696 Japanese Unexamined Patent Publication No. 2020-4528 Japanese Unexamined Patent Publication No. 2019-12148

When an insulating layer made of an insulating resin is provided on the surface of the positive electrode current collector foil on the positive electrode layer side, such an insulating resin is easily damaged when a concentrated load is applied from the outside. Therefore, for example, in an all-solid-state battery during manufacturing. The insulating layer may be damaged by the metal foreign matter mixed in, resulting in a short circuit. When a short circuit occurs, the heat generated causes the all-solid-state battery to become unsafe. In addition, the insulating layer is deformed, peeled off, or disappears due to heat generation, and the short-circuited portion expands, so that the amount of heat generated by the short-circuit is further increased, and the unsafe state is exacerbated.

Therefore, in view of the above circumstances, an object of the present application is to provide an all-solid-state battery capable of suppressing a short circuit due to a metallic foreign substance and suppressing heat generation due to the short circuit even in the case of a short circuit.

In the present disclosure, as one means for solving the above problems, an all-solid-state battery including a positive electrode current collector foil, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and an electrode body in which negative electrode current collector foils are laminated in this order. The positive electrode layer is arranged and laminated inside the solid electrolyte layer and the negative electrode layer, and is a surface of the positive electrode current collector foil on the positive electrode layer side, and is at least an end portion of the solid electrolyte layer and the negative electrode layer. Provided is an all-solid-state battery in which an insulating layer is arranged in a facing portion, the insulating layer has an adhesive layer and a ceramics layer, and the ceramics layer is adhered to a positive electrode current collector foil via the adhesive layer.

The all-solid-state battery of the present disclosure is provided with a ceramic layer as an insulating layer. Since the ceramic layer has high hardness, it is less likely to be damaged than the resin material. Therefore, according to the all-solid-state battery of the present disclosure, it is possible to suppress damage to the insulating layer due to metal foreign matter and suppress short circuit due to the damage.

Further, even when the insulating layer is damaged by a metal foreign substance and a short circuit occurs, the ceramic layer is an insulating layer or a high resistance layer, so that heat generation in the short circuit portion is suppressed. Further, since the ceramic layer has high heat resistance and deformation due to heat generation is suppressed, the expansion of short-circuited portions is suppressed. Further, since the insulating layer has an adhesive layer and the ceramic layer is adhered to the positive electrode current collector foil via the adhesive layer, the ceramic layer is suppressed from peeling off and the short circuit portion is suppressed from spreading. Therefore, according to the all-solid-state battery of the present disclosure, even when a short circuit is caused by a metal foreign substance, heat generation due to the short circuit can be suppressed.

It is a schematic diagram of the stacking direction cross section of the all-solid-state battery 100. It is a figure which shows the state of the short circuit by a metal foreign substance when the conventional insulating layer (insulating resin) is used. It is a figure which shows the state of the short circuit by a metal foreign substance when the insulating layer 70 is used. It is the result of the calorific value evaluation of an Example and a comparative example.

The all-solid-state battery of the present disclosure will be described with reference to the all-solid-state battery 100, which is an embodiment. FIG. 1 is a schematic view of a cross section of the all-solid-state battery 100 in the stacking direction.

As shown in FIG. 1, the all-solid-state battery 100 includes an electrode body 60 in which a positive electrode collector foil 10, a positive electrode layer 20, a solid electrolyte layer 30, a negative electrode layer 40, and a negative electrode current collector foil 50 are laminated in this order. The electrode body 60 defines an essential electrode structure for constituting an all-solid-state battery. Therefore, the number of the electrode bodies 60 may be one, but may be a plurality from the viewpoint of improving the battery performance. Further, a component may be shared between one electrode body 60 and another electrode body 60. For example, in FIG. 1, two electrode structures 60 share one negative electrode current collector foil 50.

The positive electrode layer 20 is arranged and laminated inside the solid electrolyte layer 30 and the negative electrode layer 40. Specifically, as shown in FIG. 1, one (other) end of the positive electrode layer 20 is arranged and laminated inside the one (other) end of the solid electrolyte layer 30 and the negative electrode layer 40. In other words, the positive electrode layer 20 is designed so that the area of the surface in the stacking direction is smaller than that of the solid electrolyte layer 30 and the negative electrode layer 40, and the entire positive electrode layer 20 is arranged inside the solid electrolyte layer 30 and the negative electrode layer 40. And laminated. This is because it is desirable to make the area of the negative electrode layer 40 larger than the area of the positive electrode layer 20 from the viewpoint of Li precipitation.

In such a case, a gap exists between the surface of the positive electrode collector foil 10 on the positive electrode layer 20 side and the solid electrolyte layer 30 and the negative electrode layer 40, and the positive electrode current collector foil 10 is subjected to vibration, impact, or the like. There is a risk that the solid electrolyte layer 30 or the negative electrode layer 40 may come into contact with each other to cause a short circuit. In order to deal with such a problem, the all-solid-state battery 100 has an insulating layer 70 on the surface of the positive electrode current collector foil 10 on the positive electrode layer 20 side, at least on a portion facing the ends of the solid electrolyte layer 30 and the negative electrode layer 40. It is arranged.

Here, the insulating layer 70 has conventionally been made of an insulating resin. However, since the insulating resin is easily damaged, for example, the insulating layer may be damaged by a metallic foreign substance mixed in the all-solid-state battery during manufacturing, resulting in a short circuit. When a short circuit occurs, the heat generated causes the all-solid-state battery to become unsafe. In addition, the insulating layer is deformed, peeled off, or disappears due to heat generation, and the short-circuited portion expands, so that the amount of heat generated by the short-circuit is further increased and the unsafe state is exacerbated.

This will be further described with reference to FIG. As shown in FIG. 2A, the insulating layer may be damaged by the metal foreign matter existing in the all-solid-state battery. In such a case, a short circuit occurs through the metal foreign matter. Then, as shown in FIG. 2B, heat generation due to a short circuit causes deformation, peeling, or disappearance of the insulating layer (insulating resin). Then, as shown in FIG. 2C, the short-circuited portion expands. As described above, when the short-circuited portion spreads, the amount of heat generated by the short-circuited increases, and the unsafe state of the entire solid-state battery further worsens.

On the other hand, in the all-solid-state battery 100, in order to solve the problem related to such metal foreign matter, the adhesive layer 71 and the ceramic layer 72 are provided on the insulating layer 70, and the positive electrode current collector foil 10 is made of ceramics via the adhesive layer 71. A structure in which the layer 72 is adhered is adopted.

Since the ceramic layer 72 has a high hardness and is less likely to be damaged than the resin material, it is possible to suppress damage to the insulating layer due to metal foreign matter and to suppress short circuit due to the damage. Further, even when the insulating layer 70 is damaged by a metal foreign substance and a short circuit occurs, the ceramic layer 72 is an insulating layer or a high resistance layer, so that heat generation in the short circuit portion is suppressed. Further, since the ceramic layer 72 has high heat resistance and deformation due to heat generation is suppressed, the expansion of short-circuited portions is suppressed. Further, the insulating layer 70 has an adhesive layer 71 for adhering the ceramic layer 72 and the positive electrode current collector foil 10. Therefore, the peeling of the ceramic layer 72 is suppressed, and the expansion of the short-circuited portion is suppressed. Therefore, according to the all-solid-state battery 100, even when a short circuit is caused by a metal foreign substance, the amount of heat generated by the short circuit can be suppressed.

This will be further described with reference to FIG. As shown in FIG. 3A, even if the ceramic layer 72 is provided, the insulating layer 70 may be damaged by the metal foreign matter existing in the all-solid-state battery 100. However, even in such a case, as shown in FIG. 3B, it is possible to suppress the expansion of the short-circuited portion by the above-mentioned action, so that the heat generation due to the short-circuited can be suppressed.

Here, consider the case where the insulating layer is made of only ceramics. Although ceramics have high hardness, they are easily broken by brittleness. Therefore, the insulating layer made of only ceramics may be peeled off from the starting point when a local force is applied by a metallic foreign substance and a scratch or a defect is generated. Then, since the positive electrode current collector foil is exposed, the short-circuit suppressing effect of the insulating layer is impaired. It is easy to imagine that such problems are more likely to occur as the ceramics become thinner. Therefore, when the insulating layer is made of only ceramics, it is necessary to adjust the insulating layer so as to have a certain thickness in order to suppress peeling due to metal foreign matter.

On the other hand, the insulating layer 70 of the all-solid-state battery 100 has an adhesive layer 71 that adheres the positive electrode current collector foil 10 and the ceramic layer 72 in addition to the ceramic layer 72. Therefore, even if the ceramic layer 72 is damaged by a metal foreign substance, the adhesive layer 71 suppresses the peeling of the ceramic layer 72. Therefore, according to the all-solid-state battery 100, the insulating layer 70 can be thinned while ensuring safety.

Hereinafter, each configuration of the electrode body 60 will be described.

<Positive current collector foil 10, negative electrode current collector foil 50>
The positive electrode current collector foil 10 and the negative electrode current collector foil 50 may be made of a metal foil, a metal mesh, or the like. Metal leaf is particularly preferable. Examples of the metal constituting the positive electrode current collector foil 10 and the negative electrode current collector foil 50 include SUS, Al, and Ni. The thickness of each of the positive electrode current collector foil 10 and the negative electrode current collector foil 50 is not particularly limited and may be the same as before. For example, the range is 0.1 μm or more and 1 mm or less.

<Positive electrode layer 20>
The positive electrode layer 20 contains at least a positive electrode active material. As the positive electrode active material, a known positive electrode active material applicable to a lithium ion all-solid-state battery may be used. For example, a lithium-containing composite oxide such as lithium cobalt oxide and lithium nickel nickel oxide can be used. The particle size of the positive electrode active material is not particularly limited, but is, for example, in the range of 5 to 50 μm. The content of the positive electrode active material in the positive electrode layer 20 is, for example, in the range of 50% by weight to 99% by weight. The surface of the positive electrode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, or a lithium phosphate layer.

Here, the "particle size" as used herein means the particle size (D ₅₀ ) at an integrated value of 50% in the volume-based particle size distribution measured by the laser diffraction / scattering method.

The positive electrode layer 20 may optionally include a solid electrolyte. Examples of the solid electrolyte include an oxide solid electrolyte and a sulfide solid electrolyte. A sulfide solid electrolyte is preferable. Examples of the oxide solid electrolyte include Li ₇ La ₃ Zr ₂ O ₁₂ , Li _7-x La ₃ Zr _1-x Nb _x O ₁₂ , Li ₃ PO ₄ , Li _{3 + x} PO _4-x N _x (LiPON), and the like. Can be mentioned. Examples of the sulfide solid electrolyte include Li ₃ PS ₄ , Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Si ₂ S-P ₂ S ₅ , Li. ₂ SP ₂ S ₅ -LiI-LiBr, LiI-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ S- P ₂ S ₅ -GeS ₂ and the like can be mentioned. The content of the solid electrolyte in the positive electrode layer 20 is not particularly limited, but is, for example, in the range of 1% by weight to 50% by weight.

The positive electrode layer 20 may optionally include a conductive auxiliary agent. Examples of the conductive auxiliary agent include carbon materials such as acetylene black, ketjen black, and vapor phase carbon fiber (VGCF), and metal materials such as nickel, aluminum, and stainless steel. The content of the conductive auxiliary agent in the positive electrode layer 20 is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

The positive electrode layer 20 may optionally include a binder. Examples of the binder include butadiene rubber (BR), butylene rubber (IIR), acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and the like. .. The content of the binder in the positive electrode layer 20 is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

The thickness of the positive electrode layer 20 is not particularly limited and may be appropriately set according to the desired battery performance. For example, the range is 0.1 μm or more and 1 mm or less.

The method for producing the positive electrode layer 20 is not particularly limited, and the positive electrode layer 20 can be produced by a known method. For example, the positive electrode layer 20 can be manufactured by mixing the materials constituting the positive electrode layer together with a solvent to form a slurry, applying the slurry to the base material or the positive electrode current collector foil 10 and drying the slurry.

<Solid electrolyte layer 30>
The solid electrolyte layer 30 contains a solid electrolyte. As the solid electrolyte, the same type as the solid electrolyte used for the positive electrode layer 20 can be used. The content of the solid electrolyte in the solid electrolyte layer is, for example, in the range of 50% by weight to 99% by weight.

The solid electrolyte layer 30 may optionally include a binder. As the binder, the same type of binder as that used for the positive electrode layer 20 can be used. The content of the binder in the solid electrolyte layer 30 is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

The method for producing the solid electrolyte layer 30 is not particularly limited, and the solid electrolyte layer 30 can be produced by a known method. For example, the solid electrolyte layer 30 can be produced by mixing the materials constituting the solid electrolyte layer 30 together with a solvent to form a slurry, applying the slurry to the substrate, and drying the slurry.

<Negative electrode layer 40>
The negative electrode layer 40 contains at least a negative electrode active material. As the negative electrode active material, a known negative electrode active material applicable to a lithium ion all-solid-state battery may be used. For example, silicon-based active materials such as Si and Si alloys, carbon-based active materials such as graphite and hard carbon, various oxide-based active materials such as lithium titanate, and lithium-based active materials such as metallic lithium and lithium alloys are used. be able to. The particle size of the negative electrode active material is not particularly limited, but is, for example, in the range of 5 to 50 μm. The content of the negative electrode active material in the negative electrode layer 40 is, for example, in the range of 30% by weight to 90% by weight.

The negative electrode layer 40 may optionally include a solid electrolyte. As the solid electrolyte, the same type as the solid electrolyte used for the positive electrode layer 20 can be used. The content of the solid electrolyte in the negative electrode layer 40 is not particularly limited, but is, for example, in the range of 10% by weight to 70% by weight.

The negative electrode layer 40 may optionally include a conductive auxiliary agent. As the conductive auxiliary agent, the same kind as the conductive auxiliary agent used for the positive electrode layer 20 can be used. The content of the conductive auxiliary agent in the negative electrode layer 40 is not particularly limited, but is, for example, in the range of 0.1% by weight to 20% by weight.

The negative electrode layer 40 may optionally include a binder. As the binder, the same kind of binder as the conductive auxiliary agent used for the positive electrode layer 20 can be used. The content of the binder in the negative electrode layer 40 is not particularly limited, but is, for example, in the range of 0.1% by weight to 10% by weight.

The thickness of the negative electrode layer 40 is not particularly limited, and may be appropriately set according to the desired battery performance. For example, the range is 0.1 μm or more and 1 mm or less.

The method for producing the negative electrode layer 40 is not particularly limited, and the negative electrode layer 40 can be produced by a known method. For example, the negative electrode layer 40 can be manufactured by mixing the materials constituting the negative electrode layer 40 together with a solvent to form a slurry, applying the slurry to the base material or the negative electrode current collector foil 50, and drying the slurry.

<Insulation layer 70>
The insulating layer 70 is a surface of the positive electrode current collector foil 10 on the positive electrode layer 20 side, and is arranged at least on a portion facing the ends of the solid electrolyte layer 30 and the negative electrode layer 40. This is to suppress contact between the positive electrode current collector foil 10 and the solid electrolyte layer 30 and the negative electrode layer 40. From the viewpoint of further suppressing contact, it is preferably arranged in the following range. In FIG. 1, in the left-right direction (width direction), a portion facing the end portion of the solid electrolyte layer 30 and the negative electrode layer 40 is included, and the solid electrolyte layer 30 and the negative electrode layer 40 are arranged in the range of 0.1 mm to 50 mm. Regarding the back front direction (direction orthogonal to the stacking direction and the width direction), the positive electrode current collector foil 10 is arranged over the back front direction. The thickness (length in the stacking direction) of the insulating layer 70 shall be equal to or less than the thickness of the positive electrode layer 20. The thickness of the insulating layer 70 is 1 μm or more. More preferably, it is 30 μm to 60 μm.

As described above, the insulating layer 70 has an adhesive layer 71 and a ceramic layer 72, and the ceramic layer 72 is adhered to the positive electrode current collector foil 10 via the adhesive layer 71. The adhesive layer 71 is made of a known resin-based binder. The thickness of the adhesive layer 71 shall be 0.5 μm or more and less than half the thickness of the entire insulating layer 70. It is preferably 10 μm to 20 μm. The ceramic layer 72 is made of ceramics. Specifically, it is a known ceramic material such as alumina. The thickness of the ceramic layer 72 shall be 0.5 μm or more and less than half the thickness of the entire insulating layer 70. It is preferably 15 μm or more and 50 μm or less. Further, the ceramic layer 72 is preferably formed thicker than the adhesive layer 71.

The insulating layer 70 can be manufactured by first forming the ceramic layer 72 and then coating the ceramic layer 72 with a resin-based binder to form the adhesive layer 71. The insulating layer 70 can be arranged on the positive electrode current collecting foil 10 by attaching the insulating layer 70 to a predetermined position of the positive electrode current collecting foil 10 via the adhesive layer 71.

Hereinafter, the all-solid-state battery of the present disclosure will be further described with reference to Examples.

The ceramic tape (insulating layer) on which the adhesive layer and the ceramic layer were formed was attached to a predetermined position on the positive electrode current collector foil (Al foil). Next, a polypropylene sheet (simulated cell) is prepared, a resin sheet is sandwiched between the above-mentioned positive electrode current collector foil and negative electrode current collector foil (Ni foil), and the resin sheet is sealed with a laminated sheet to prepare an evaluation battery according to an example. did.

An evaluation battery according to a comparative example was produced by the same method as described above except that the insulating layer was replaced with a polyimide tape (insulating resin tape).

In the prepared evaluation batteries according to the Examples and Comparative Examples, a needle was pierced from the positive electrode current collector foil (Al foil) side toward the portion where the insulating layer was arranged to cause a short circuit. At this time, the calorific value was calculated from the current flowing from the external power source connected in parallel with the evaluation battery and the voltage drop set by the external power source. The results are shown in FIG.

As shown in FIG. 4, the calorific value (about 80 W) of the example was lower than the calorific value (about 125 W) of the comparative example.

The calorific value (W) is defined as the calorific value (J) per second. Assuming that the amount of heat required to reach the temperature at which the battery is short-circuited and becomes unsafe is X (J), the larger the value of the calorific value (W), the shorter the time to reach X (J). .. Even if the heat dissipation of the battery is taken into consideration, the smaller the amount of heat generated, the smaller the amount of heat given to the short-circuited portion of the battery, and therefore the higher the safety. In addition, even if the heat generation continues, the time to reach an unsafe state becomes long, so that a time grace can be obtained, and further higher safety can be ensured by combining with other safety mechanisms.

Therefore, it was found that the examples can suppress the calorific value due to the short circuit and can ensure the safety as compared with the comparative examples.

10 Positive electrode collector foil 20 Positive electrode layer 30 Solid electrolyte layer 40 Negative electrode layer 50 Negative electrode collector foil 60 Electrode body 70 Insulation layer 71 Adhesive layer 72 Ceramic layer 100 All-solid-state battery

Claims (1)

An all-solid-state battery including an electrode body in which a positive electrode collector foil, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode collector foil are laminated in this order.
The positive electrode layer is arranged and laminated inside the solid electrolyte layer and the negative electrode layer.
An insulating layer is arranged on the surface of the positive electrode current collector foil on the positive electrode layer side, at least on a portion facing the end of the solid electrolyte layer and the negative electrode layer.
The insulating layer has an adhesive layer and a ceramic layer, and the ceramic layer is adhered to the positive electrode current collector foil via the adhesive layer.
All-solid-state battery.

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