JP7135916B2 - laminate - Google Patents

Description

The present disclosure relates to laminates.

2. Description of the Related Art In recent years, with the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as power sources for these devices has been emphasized. In addition, in the automobile industry and the like, development of high-output and high-capacity batteries for electric vehicles or hybrid vehicles is underway.
In the field of batteries such as lithium ion batteries, all-solid-state batteries have been developed in which a solid electrolyte is used instead of an electrolyte solution containing an organic solvent as an electrolyte interposed between a positive electrode active material layer and a negative electrode active material layer. there is An all-solid-state battery does not use a combustible organic solvent in the battery, so it is thought that the safety device can be simplified and the manufacturing cost and productivity are excellent. In an all-solid-state battery, each layer is arranged so as to be in contact with each other, since conduction is achieved by physical contact between the layers.

Patent Literature 1 describes that lamination misalignment is suppressed by bonding a positive electrode foil and a positive electrode active material layer with a thermoplastic resin.

Patent Document 2 describes providing a conductive adhesive layer between a positive electrode active material layer and a separator.

JP 2017-204377 A Japanese Unexamined Patent Application Publication No. 2017-216160

An electrode in which a current collector and an active material layer are adhered with a resin has a problem that the resin cannot follow the expansion and contraction during charging and discharging of the battery, and cracks may occur in the electrode.
In view of the above circumstances, an object of the present disclosure is to provide a laminate that can suppress cracking of electrodes.

The present disclosure is a laminate having a current collector, an active material layer, and an electrolyte layer in this order,
Provided is a laminate, wherein the current collector and the active material layer are bonded via an adhesive having an elastic modulus of 1000 MPa or less.

The present disclosure can provide a laminate that can suppress cracking of electrodes.

It is a cross-sectional schematic diagram which shows an example of the laminated body of this indication. It is a cross-sectional schematic diagram which shows an example of the battery unit of the all-solid-state battery of this indication.

The present disclosure is a laminate having a current collector, an active material layer, and an electrolyte layer in this order,
Provided is a laminate, wherein the current collector and the active material layer are bonded via an adhesive having an elastic modulus of 1000 MPa or less.

In the present disclosure, by using an adhesive having an elastic modulus of 1000 MPa or less, it is possible to provide a laminate capable of suppressing cracking of electrodes.

FIG. 1 is a cross-sectional schematic diagram showing an example of the laminate of the present disclosure.
A laminate 100 of the present disclosure has a current collector 10, an active material layer 11, and an electrolyte layer 12 in this order.
In the laminate 100 of the present disclosure, the current collector 10 and the active material layer 11 are bonded together via an adhesive 13 having an elastic modulus of 1000 MPa or less.

The elastic modulus of the adhesive may be 1000 MPa or less, preferably 500 MPa or less, and the lower limit is preferably 0.1 MPa or more from the viewpoint of further increasing the adhesion between the current collector and the active material layer.
As the elastic modulus, the storage elastic modulus at a temperature of 25° C., which can be measured based on JIS K 7198 (Plastics—Test method for dynamic mechanical properties, Part 4, Tensile vibration) was used.

As the adhesive, for example, an adhesive containing at least an adhesive resin and optionally containing a conductive substance or the like can be mentioned.
Examples of adhesive resins include silicone resins and polyolefin resins such as ethylene-vinyl acetate copolymer (EVA) and low-density polyethylene (LDPE).
In the present disclosure, the adhesive may have peelable adhesiveness or may have adhesiveness that is difficult to peel off.
As the adhesive, a commercially available product may be used, and for example, one commercially available as an adhesive or pressure-sensitive adhesive may be appropriately selected and used.

Examples of conductive substances that may be contained in the adhesive include powders such as carbon powders and aluminum powders. When the adhesive is present in the entire overlapping region of the current collector and the active material layer that adhere to each other, the adhesive may be an adhesive containing a conductive substance. It is preferable from the point that conduction with is improved.
In the adhesive containing a conductive substance, the content of the conductive substance is not particularly limited. , the volume resistivity is preferably adjusted to 10×10 ³ Ω/cm or less.
When the conductive substance is carbon powder, the content of the carbon powder in the adhesive is preferably 1% by mass to 10% by mass when the total mass of the adhesive is 100% by mass. .

The thickness of the adhesive in the stacking direction of the laminate is not particularly limited, but may be, for example, 0.1 μm or more and 10 μm or less.
If the adhesive is placed on at least part of one surface of the active material layer and at least part of one surface of the current collector in the region where the active material layer and the current collector face each other and overlap, It is not particularly limited, and when the active material layer and the current collector are rectangular, from the viewpoint of improving the adhesiveness, the active material layer and the current collector are arranged at predetermined four corners of the region where the active material layer and the current collector face each other and overlap each other. It is preferable that
The method of disposing the adhesive is not particularly limited, and it may be disposed by coating.
The amount of the adhesive to be applied to the current collector is not particularly limited. The adhesive is applied and a predetermined pressure and/or heat is applied so that the thickness of the adhesive reaches a predetermined thickness.

Specifically, from the viewpoint of ease of handling, the adhesive is preferably capable of compressing a spherical adhesive with a diameter of 1 mm to a thickness of 0.1 to 10 μm.

[Active material layer]
The active material layer forming the laminate may be a positive electrode active material layer or a negative electrode active material layer.
When the active material layer constituting the laminate is the positive electrode active material layer, the current collector is the positive electrode current collector, and when the active material layer constituting the laminate is the negative electrode active material layer, the current collector is , is the negative electrode current collector.

[Positive electrode active material layer]
The positive electrode active material layer contains a positive electrode active material, and may contain a solid electrolyte, a conductive material, a binder, and the like as optional components.

As the positive electrode active material, for example, Li _x M _y O _z (M is a transition metal element, x = 0.02 to 2.2, y = 1 to 2, z = 1.4 to 4). can be mentioned. In the above general formula, M includes at least one selected from the group consisting of Co, Mn, Ni, V, Fe and Si, and may be at least one selected from the group consisting of Co, Ni and Mn. . Specific examples of such positive electrode active materials include LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li(Ni _{0 .5Mn1.5 ) O4} , _Li2FeSiO4 , _{Li2MnSiO4 and} the _like .
_Examples of positive electrode active materials other than _LixMyOz represented by the general formula include lithium titanate ₍ e.g., _Li4Ti5O12 ), lithium metal _{phosphate ( LiFePO4} , _LiMnPO4 , _LiCoPO4 , _LiNiPO4 ), transition metal oxides ( _V2O5 , _MoO3 ), _TiS2 , _LiCoN , Si, _{SiO2 , Li2SiO3} , _Li4SiO4 , and lithium storage intermetallic compounds ₍ e.g. _Mg2Sn , _Mg2Ge , Mg ₂ Sb, Cu ₃ Sb) and the like.
Although the shape of the positive electrode active material is not particularly limited, it may be particulate.
A coat layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed.
Li ion conductive oxides include, for example, LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , Li ₃ PO ₄ and the like.
The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but may be, for example, within the range of 10% by mass to 100% by mass.
Examples of the solid electrolyte used for the positive electrode active material layer include solid electrolytes similar to those used for the electrolyte layer described later. The content ratio of the solid electrolyte in the positive electrode active material layer is not particularly limited.

As the conductive material, a known material can be used, and examples thereof include carbon materials, metal particles, and the like. Examples of the carbon material include at least one selected from the group consisting of carbon black such as acetylene black and furnace black, carbon nanotubes, and carbon nanofibers. and at least one selected from the group consisting of carbon nanofibers. The carbon nanotube and carbon nanofiber may be VGCF (vapor grown carbon fiber). Metal particles include particles of Al, Ni, Cu, Fe, SUS, and the like. The content of the conductive material in the positive electrode active material layer is not particularly limited.

Examples of binders include rubber binders such as butadiene rubber, hydrogenated butadiene rubber, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, and ethylene propylene rubber, polyvinylidene fluoride ( PVdF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluoride-based binders such as fluororubber, polyolefin-based thermoplastic resins such as polyethylene, polypropylene, and polystyrene, imide resins such as polyimide and polyamideimide; amide resins such as polyamide; acrylic resins such as polymethyl acrylate and polyethyl acrylate; and methacrylic resins such as polymethyl methacrylate and polyethyl methacrylate. . The content of the binder in the positive electrode active material layer is not particularly limited.

Although the thickness of the positive electrode active material layer is not particularly limited, it may be, for example, 0.1 μm or more and 1000 μm or less.

[Positive collector]
A known metal material that can be used as a battery current collector can be used for the positive electrode current collector. Examples of such metal materials include SUS, Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In.
The shape of the positive electrode current collector is not particularly limited, and various shapes such as a foil shape and a mesh shape can be used.
The positive electrode current collector may have a positive electrode lead for connection with an external terminal.

The positive electrode current collector may have a coat layer containing a conductive material such as Ni, Cr, or C (carbon) on at least part of the surface of the metal foil containing the metal. By having the coat layer, it is possible to suppress an increase in internal resistance due to the formation of a passive film on the surface of the positive electrode current collector.
The coat layer contains at least a conductive material, and if necessary, may further contain other components such as a binder. Examples of the binder that the coating layer may contain include the same binders that the positive electrode active material layer may contain. Also, the coat layer may be a plated layer or a deposited layer made of a conductive material.
As a specific example of the coating layer, for example, it contains 15% by mass of C (carbon) as a conductive material, further contains 85% by mass of polyvinylidene fluoride (PVDF) as a binder, and has a volume resistivity of 1×. A carbon coating layer of 10 ³ Ωcm to 10×10 ³ Ωcm, preferably 5×10 ³ Ωcm can be mentioned.
Although the thickness of the coat layer is not particularly limited, it can be, for example, about 10 μm.
It is preferable that the coat layer is arranged on the surface of the positive electrode current collector in a region where the positive electrode current collector and the positive electrode active material layer, which are adhered to each other, overlap, from the viewpoint of easily suppressing an increase in the internal resistance of the battery. . Among them, when the positive electrode current collector and the positive electrode active material layer that are adhered to each other have a portion that is in direct contact without an adhesive, at least part of the surface of the positive electrode current collector that is in direct contact with the positive electrode active material layer In addition, it is preferable to have a coat layer.

[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material, and may contain a solid electrolyte, a conductive material, a binder, and the like as optional components.

Conventionally known materials can be used as the negative electrode active material, and examples thereof include Li simple substance, lithium alloys, carbon, Si simple substances, Si alloys, and Li ₄ Ti ₅ O ₁₂ (LTO).
Lithium alloys include LiSn, LiSi, LiAl, LiGe, LiSb, LiP, and LiIn.
Examples of Si alloys include alloys with metals such as Li, and may be alloys with at least one metal selected from the group consisting of Sn, Ge, and Al.
The shape of the negative electrode active material is not particularly limited, but may be, for example, particulate or thin film.
When the negative electrode active material is particles, the average particle diameter (D50) of the particles is, for example, preferably 1 nm or more and 100 μm or less, more preferably 10 nm or more and 30 μm or less.

Examples of the conductive material, binder, and solid electrolyte contained in the negative electrode active material layer are the same as those contained in the positive electrode active material layer described above.

[Negative electrode current collector]
As the negative electrode current collector, a metal material similar to the metal material used as the positive electrode current collector can be used.
The form of the negative electrode current collector is not particularly limited, and may be the same form as the positive electrode current collector.
The negative electrode current collector may have a negative electrode lead for connection with an external terminal.

[Electrolyte layer]
The electrolyte layer may be a separator layer in which a separator or the like is impregnated with an electrolytic solution, or may be a solid electrolyte layer containing a solid electrolyte, and the current collector and the active material layer are excellent in recyclability and repairability. From a viewpoint, a solid electrolyte layer is preferable. Examples of separators include nonwoven fabrics, porous membranes, and the like.

The solid electrolyte layer contains at least a solid electrolyte.
Solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and the like.
Examples of sulfide solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S—SiS ₂ , LiX—Li ₂ S—SiS ₂ , LiX—Li ₂ SP ₂ S ₅ , LiX—Li ₂ O—Li ₂ SP ₂ S ₅ , LiX—Li ₂ SP ₂ O ₅ , LiX—Li ₃ PO ₄ —P ₂ S ₅ , Li ₃ PS ₄ and the like. The above description of "Li ₂ SP _{2 S 5 " means a material obtained by using a raw material composition containing Li 2 S and P 2 S 5 , and} the same applies to other descriptions. "X" in LiX above represents a halogen element. One or more kinds of LiX may be contained in the raw material composition containing LiX. When two or more types of LiX are included, the mixing ratio of the two or more types is not particularly limited.
As the sulfide-based solid electrolyte, for example, Li ₂ S and P ₂ S ₅ are added so that the mass ratio of Li ₂ S and P ₂ S ₅ (Li ₂ S/P ₂ S ₅ ) is 0.5 or more. and a sulfide-based solid electrolyte prepared by mixing. In addition, a sulfide-based solid electrolyte prepared by mixing Li ₂ S and P ₂ S ₅ so that the mass ratio of Li ₂ S:P ₂ S ₅ is 70:30 is preferable from the viewpoint of ion conductivity. Used.
The molar ratio of each element in the sulfide-based solid electrolyte can be controlled by adjusting the content of each element in the raw material. Also, the molar ratio and composition of each element in the sulfide-based solid electrolyte can be measured, for example, by ICP emission spectrometry.

The sulfide-based solid electrolyte may be sulfide glass, crystallized sulfide glass (glass ceramics), or a crystalline material obtained by solid-phase reaction treatment of a raw material composition. .
The crystalline state of the sulfide-based solid electrolyte can be confirmed, for example, by subjecting the sulfide-based solid electrolyte to powder X-ray diffraction measurement using CuKα rays.

Sulfide glass can be obtained by subjecting a raw material composition (for example, a mixture of Li ₂ S and P ₂ S ₅ ) to amorphous processing. Examples of amorphous processing include mechanical milling. The mechanical milling may be dry mechanical milling or wet mechanical milling, but the latter is preferred. This is because the raw material composition can be prevented from sticking to the walls of the container or the like.
Mechanical milling is not particularly limited as long as it is a method of mixing the raw material composition while applying mechanical energy. Among them, a ball mill is preferable, and a planetary ball mill is particularly preferable. This is because the desired sulfide glass can be efficiently obtained.

Glass-ceramics can be obtained, for example, by heat-treating sulfide glass.
The heat treatment temperature may be any temperature higher than the crystallization temperature (Tc) observed by thermal analysis measurement of sulfide glass, and is usually 195° C. or higher. On the other hand, the upper limit of the heat treatment temperature is not particularly limited.
The crystallization temperature (Tc) of sulfide glass can be measured by differential thermal analysis (DTA).
The heat treatment time is not particularly limited as long as the desired crystallinity of the glass-ceramics is obtained. is mentioned.
The method of heat treatment is not particularly limited, but for example, a method using a kiln can be mentioned.

Examples of oxide solid electrolytes include Li _6.25 La ₃ Zr ₂ Al _0.25 O ₁₂ , Li ₃ PO ₄ and Li _3+x PO _4-x N _x (LiPON).

The shape of the solid electrolyte is preferably particulate from the viewpoint of ease of handling.
The average particle diameter (D50) of the particles of the solid electrolyte is not particularly limited, but the lower limit is preferably 0.5 μm or more, and the upper limit is preferably 2 μm or less.
Solid electrolytes can be used singly or in combination of two or more. Moreover, when using 2 or more types of solid electrolytes, you may mix 2 or more types of solid electrolytes.

In the present disclosure, unless otherwise specified, the average particle diameter of particles is the volume-based median diameter (D50) measured by laser diffraction/scattering particle size distribution measurement. In the present disclosure, the median diameter (D50) is the diameter (volume average diameter) at which the cumulative volume of particles is half (50%) of the total volume when the particles are arranged in order from the smallest particle size.

The content ratio of the solid electrolyte in the solid electrolyte layer is not particularly limited.

The solid electrolyte layer may contain a binder that binds the solid electrolytes together from the viewpoint of exhibiting plasticity. As such a binder, the binder etc. which can be contained in the positive electrode layer mentioned above can be illustrated. However, in order to make it easier to increase the output of the battery, from the viewpoint of preventing excessive aggregation of the solid electrolyte and making it possible to form a solid electrolyte layer having a uniformly dispersed solid electrolyte, the solid electrolyte layer The content of the binder to be contained is preferably 5.0% by mass or less.

The thickness of the solid electrolyte layer is appropriately adjusted depending on the configuration of the battery and is not particularly limited, and is usually 0.1 μm or more and 1 mm or less.
The solid electrolyte layer may be formed by, for example, pressing powder of the solid electrolyte layer material containing the solid electrolyte and, if necessary, other components.

[Laminate production method]
The method for producing the laminate of the present disclosure is not particularly limited as long as it is a method capable of obtaining the above-described laminate of the present disclosure.
The method for manufacturing a laminate according to the present disclosure may have, for example, (1) a bonding step, (2) a pressing step, and (3) an adhesive placement step.

(1) Joining Step The joining step is a step of preparing at least an active material layer and an electrolyte layer and joining these layers to obtain a joined body.
The method of joining the active material layer and the electrolyte layer is not particularly limited. For example, the active material layer may be formed on the support, and the electrolyte layer may be further formed thereon. Alternatively, the active material layer and the electrolyte layer may be bonded by forming the active material layer and the electrolyte layer on separate supports and transferring the electrolyte layer to the active material layer. The pressure applied to each layer when transferring each layer is not particularly limited, but may be about 100 MPa.
In addition, the bonded body may be a bonded body in which at least the active material layer and the electrolyte layer are bonded, and the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer are arranged in this order according to the purpose. It may be a conjugate.
The method of forming the active material layer is not particularly limited, but examples include a method of pressure-molding a powder of an electrode mixture containing an active material and, if necessary, other components.
Further, as another example of the method of forming the active material layer, an electrode mixture paste containing an active material, a solvent and, if necessary, other components is prepared, and the electrode mixture paste is applied to a support such as a solid electrolyte layer. and drying the electrode mixture paste.
Solvents used in the electrode mixture paste include, for example, butyl acetate, heptane, N-methyl-2-pyrrolidone, and the like.
The method of applying the electrode mixture paste onto one surface of the support such as the solid electrolyte layer is not particularly limited, and includes a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, and a roll coating method. method, gravure coating method, screen printing method, and the like.
As the support, a material having self-supporting properties can be appropriately selected and used, and there is no particular limitation. For example, a metal foil or the like can be used.

(2) Pressing step The pressing step is a step of pressing the joined body in the stacking direction of the joined body with a predetermined pressure.
The pressure when pressing the joined body may be, for example, more than 20 MPa and less than or equal to 600 MPa.
The temperature at which the joined body is pressed is not particularly limited, and may be appropriately adjusted so as to be lower than the deterioration temperature of the materials contained in the joined body.
The method of applying pressure when pressing the joined body is not particularly limited, but examples thereof include a method of applying pressure using a flat plate press, a roll press, or the like.

(3) Adhesive placement step In the adhesive placement step, a current collector is prepared, and an adhesive is applied to at least one surface of the current collector or the surface of the active material layer of the assembly opposite to the electrolyte layer. It is a step of arranging and adhering the current collector and the active material layer via an adhesive to obtain a laminate. The laminate forms part or all of the layer structure of the battery, and the layer structure can be appropriately changed according to the purpose, as long as the laminate has at least a current collector, an active material layer, and an electrolyte layer. , a battery unit to be described later, or a battery unit laminate.

In the adhesive placement step, for example, the adhesive is placed on one side of the current collector, and the active material layer of the joined body is adhered to one side of the current collector to form the first current collector and the first active material layer. , the electrolyte layer, and the second active material layer may be laminated in this order. Then, if necessary, a second current collector may be adhered to the surface of the second active material layer opposite to the electrolyte layer side with an adhesive to form a battery unit. Furthermore, a second laminate having a layer structure similar to that of the first laminate is prepared, and the third laminate of the second laminate is provided on the surface opposite to the second active material layer of the second current collector. The active material layers may be adhered via an adhesive to form a battery unit laminate. In this case, when the first active material layer is the positive electrode active material layer, the second active material layer may be the negative electrode active material layer, and the third active material layer may be the positive electrode active material layer. Alternatively, it may be a negative electrode active material layer.

Further, in the adhesive placement step, the adhesive is placed on both sides of the current collector, and the active material layers of the joined body are adhered to both sides of the current collector to form a first active material layer and a first electrolyte layer. , the second active material layer, the first current collector, the third active material layer, the second electrolyte layer, and the fourth active material layer in this order. Then, a second current collector may be further adhered to the surface of the first active material layer opposite to the first electrolyte layer side with an adhesive to form a battery unit. A battery unit may be formed by further adhering a third current collector to the surface of the active material layer 4 opposite to the surface facing the second electrolyte layer with an adhesive. Furthermore, a fourth laminate having a layer structure similar to that of the third laminate is prepared, and the fifth laminate of the fourth laminate is provided on the surface opposite to the first active material layer of the second current collector. The active material layers may be adhered via an adhesive to form a battery unit laminate. In this case, when the first active material layer and the fourth active material layer are the positive electrode active material layers, the second active material layer and the third active material layer are the negative electrode active material layers, and the fifth active material layer is the negative electrode active material layer. The active material layer may be a positive electrode active material layer or a negative electrode active material layer.

Further, the adhesive disposing step is preferably performed after the above (2) pressing step when ensuring that the current collector and the active material layer can be peeled off.
In the adhesive placement step, the method of placing the adhesive on at least one surface of the current collector or the surface of the active material layer of the assembly opposite to the electrolyte layer is, for example, a method of applying a paste adhesive. , and a method of attaching a film or sheet adhesive. Film- or sheet-like adhesives include, for example, double-sided tapes.
Among them, the method of applying a paste-like adhesive is preferable because the thickness of the adhesive can be easily reduced and the pressure can be applied evenly during pressing. When the adhesive is a solid thermoplastic adhesive such as a pellet type, it can be applied while being heated and melted using a hot-melt applicator, for example. A paste-type thermoplastic adhesive containing a solvent can be applied at room temperature, and can be solidified by drying the solvent after application.

When the adhesive is placed on the current collector or the active material layer, it may be placed so that at least part of the region where the current collector and the active material layer overlap is adhered.
The adhesive pressure when bonding the current collector and the active material layer is preferably weaker than the pressing pressure in the above (2) pressing step, from the viewpoint of suppressing the occurrence of cracks in the active material layer and the current collector. 1 to 20 MPa is preferred.

When the adhesive is a thermoplastic adhesive, for example, the bonded body of the current collector and the active material layer before bonding is heated and pressed in the stacking direction, and then cooled to bond the current collector and the active material layer. and can be glued together. Since the thermoplastic adhesive is melted by heating and then solidified by cooling, the current collector and the active material layer are adhered by the adhesive.
When the adhesive contains EVA, the heating temperature when the bonded body of the current collector and the active material layer before bonding is pressed in the stacking direction while being heated can be, for example, about 140°C. When the agent contains a silicone resin, the temperature can be, for example, about 20 to 25°C.

[All-solid battery]
Laminates of the present disclosure can be used as part or all of a variety of battery layer configurations.
Moreover, the laminate of the present disclosure may have a layer structure that functions as an all-solid-state battery.
The all-solid-state battery of the present disclosure includes a positive electrode including a positive electrode active material layer and a positive electrode current collector, a negative electrode including a negative electrode active material layer and a negative electrode current collector, and between the positive electrode active material layer and the negative electrode active material layer and a solid electrolyte layer to be disposed, and may be a battery unit laminate including two or more battery units.
The number of battery units included in the battery unit laminate is not particularly limited, and may be, for example, 2 to 50.

In the battery unit of the present disclosure, at least one of the positive electrode or the negative electrode current collector and the active material layer may be bonded via an adhesive. It is preferable that the layer and the positive electrode current collector are adhered via an adhesive, and that the negative electrode active material layer and the negative electrode current collector are adhered via the adhesive.

FIG. 2 is a cross-sectional schematic diagram showing an example of a battery unit of the all-solid-state battery of the present disclosure.
As shown in FIG. 2, the battery unit 200 includes a positive electrode 40 including a positive electrode current collector 20 and a positive electrode active material layer 21, a negative electrode 41 including a negative electrode current collector 24 and a negative electrode active material layer 23, and a positive electrode active material layer. 21 and a negative electrode active material layer 23, the positive electrode active material layer 21 is adhered to the positive electrode current collector 20 via an adhesive 13, and the negative electrode active material layer 23 is , and the negative electrode current collector 24 via the adhesive 13 .

The all-solid-state battery optionally includes a positive electrode, a negative electrode, and an outer casing housing a solid electrolyte layer.
The shape of the exterior body is not particularly limited, but a laminate type or the like can be mentioned.
The material of the exterior body is not particularly limited as long as it is stable in the electrolyte, and examples thereof include polypropylene, polyethylene, polyethylene terephthalate (PET), and resins such as acrylic resin. One type of resin may be used for the exterior body, or a plurality of types may be used in combination.

All-solid-state batteries include all-solid-state lithium batteries that utilize the deposition-dissolution reaction of metallic lithium as the negative electrode reaction, all-solid-state lithium-ion batteries in which lithium ions move between the positive and negative electrodes, all-solid-state sodium batteries, and all-solid-state magnesium. A battery, an all-solid calcium battery, etc. can be mentioned, and an all-solid lithium ion battery may be used. Moreover, the all-solid-state battery may be a primary battery or a secondary battery.
Examples of the shape of the all-solid-state battery include coin type, laminate type, cylindrical type, rectangular type, and the like.

The pressure applied to the all-solid-state battery when the all-solid-state battery of the present disclosure is used can be, for example, 1 MPa or more and 45 MPa or less, and the pressure applied to the all-solid-state battery when the all-solid-state battery is not in use is For example, it can be 0 MPa or more and 1 MPa or less.

Methods for pressurizing an all-solid-state battery include, for example, mechanical pressurization and gas pressurization.
Examples of mechanical pressurization include a method of driving a motor to apply pressure in the stacking direction of the all-solid-state battery via a ball screw, and a method of driving a motor to apply pressure in the stacking direction of the all-solid-state battery via hydraulic pressure. mentioned. In the mechanical pressurization, after pressurizing or depressurizing the all-solid-state battery to a predetermined pressure, by fixing the moving part of the machine with a mechanical stopper, the energy consumption associated with driving the motor can be minimized.
Gas pressurization includes, for example, a method of pressurizing the all-solid-state battery via a pressurized gas from a pre-mounted gas cylinder.

The all-solid-state battery of the present disclosure is used, for example, as a power source mounted on a vehicle or a power source for driving portable electronic devices, etc., but is not limited to these uses.
Vehicles to which the all-solid-state battery of the present disclosure is applied are not limited to electric vehicles that are equipped with a battery and no engine, and include hybrid vehicles that are equipped with both a battery and an engine.

(Comparative example 1)
As a test cell for an all-solid-state battery, a negative electrode current collector (Cu foil, width 11.74 mm, thickness 35 μm), negative electrode active material layer (width 11.74 mm, thickness 25 μm, negative electrode active material: Si alone), solid electrolyte layer (width 11.74 mm, thickness 15 μm), cathode active material layer (thickness 50 μm, cathode active material: LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), cathode current collector (Al foil, thickness 15 μm thick) were laminated in this order to prepare a laminate. The laminate was then sealed with a transparent PET/PP laminate resin to obtain a test cell.
The positive electrode active material layer of the test cell was placed on the four corners of the surface of the positive electrode active material layer with adhesive (EVA hot melt resin, elastic modulus 1200 MPa, width 2 mm, thickness 10 μm) through the positive electrode current collector. The negative electrode active material layer is adhered to the body, and the negative electrode active material layer is disposed via an adhesive (EVA hot melt resin, elastic modulus 1200 MPa, width 2 mm, thickness 10 μm) arranged at the four corners on the surface of the negative electrode active material layer. is adhered to the negative electrode current collector.
The bonding between each current collector and the active material layer was performed under the conditions of a press pressure of 20 MPa and a temperature of 140.degree.

[Calculation of Volume Expansion Rate of Battery Cell]
The volume of the obtained test cell at SOC 0% (cell voltage 3 V) before the first charge was calculated from the thickness, width, and depth of the cell.
Then, the test cell is charged from SOC 0% (cell voltage 3 V) to SOC 100% (cell voltage 4.5 V), the volume of the test cell when the cell voltage is 3.5 V, and the volume of the test cell when the cell voltage is 4.0 V The volume of the test cell when the cell voltage is 4.5 V is calculated in the same manner as above, and the volume expansion rate of the test cell after charging with respect to the volume of the test cell when the cell voltage is 3 V (before the first charge) It was calculated from the following formula (1).
formula (1)
Volumetric expansion rate (%) =
{(cell volume after charging-cell volume before first charging)/cell volume before first charging}×100
Table 1 shows the results.

[Confirmation of electrode cracks due to charging]
When the volume expansion rate of the test cell is 15%, when it is 30%, and when it is 45%, test cells are prepared, each test cell is disassembled, the positive electrode and the negative electrode are taken out, and the electrode cracks The presence or absence was visually confirmed. Table 2 shows the results.

(Comparative example 2)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 1100 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 1)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 1000 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 2)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 900 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 3)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 800 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 4)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 500 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 5)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 150 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 6)
A test cell similar to that of Comparative Example 1 was prepared except that the adhesive was changed to an EVA-based hot-melt resin having a modulus of elasticity of 20 MPa, and the presence or absence of cracks in the electrode due to charging was checked.

(Example 7)
Comparative Example 1, except that the adhesive was changed to a silicone resin having an elastic modulus of 0.1 MPa, and the adhesion between each current collector and the active material layer was performed under the conditions of a press pressure of 20 MPa and a temperature of 25°C. A similar test cell was prepared, and the presence or absence of cracks in the electrode due to charging was confirmed.

As shown in Table 2, it is clear that if the adhesive has an elastic modulus of 1000 MPa or less, cracking of at least the positive electrode can be prevented even when the all-solid-state battery is charged to an SOC of 100%. It was found that if the adhesive is 500 MPa or less, cracking of both the positive and negative electrodes can be prevented even when the all-solid-state battery is charged to an SOC of 100%.

10 current collector 11 active material layer 12 electrolyte layer 13 adhesive 20 positive electrode current collector 21 positive electrode active material layer 22 solid electrolyte layer 23 negative electrode active material layer 24 negative electrode current collector 40 positive electrode 41 negative electrode 100 laminate 200 battery unit

Claims (1)

A laminate having a current collector, an active material layer and an electrolyte layer in this order,
The current collector and the active material layer are bonded via a silicone resin having an elastic modulus of 0.1 MPa or an ethylene vinyl acetate copolymer (EVA) hot melt resin having an elastic modulus of 20 MPa or more and 500 MPa or less as an adhesive. A laminate characterized by comprising:

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