Solid state battery

Abstract

The invention relates to a solid state battery. The solid-state battery includes a plurality of unit electrode stacks. The unit electrode laminates each include at least a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer. The solid-state battery further comprises an adhesive layer between the two unit electrode laminated bodies adjacent to each other. The product of the area ratio (unit: area%) of the adhesive layer on the surface of the unit electrode laminate that is in contact with the adhesive layer and the thickness (unit: mm) of the unit electrode laminate is 12 or less.

Description

Technical Field

[0001] This disclosure relates to a solid-state battery. Background Technology

[0002] For example, the battery described in Japanese Patent Application Publication No. 2020-140932 (JP2020-140932A) is a battery in which the current collector layer and the active material layer in the unit electrode stack are bonded together by an adhesive layer.

[0003] JP2020-140932A discloses an all-solid-state battery comprising two or more stacked battery cells with unipolar structures. Each of the stacked battery cells has the following configuration: a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, a second current collector layer, a second active material layer, a solid electrolyte layer, a first active material layer, and a first current collector layer are stacked sequentially. Adjacent stacked first current collector layers and first active material layers are bonded together using an adhesive. Summary of the Invention

[0004] When unit electrode stacks are bonded together, uneven thickness of active material layers, etc., may cause stress between layers, leading to interlayer delamination.

[0005] This disclosure is made in view of the foregoing, and the purpose of this disclosure is to provide a solid-state battery that exhibits superior performance in suppressing interlayer delamination within the cell electrode stack.

[0006] The means to solve the above problems include the following aspects.

[0007] <1> A solid-state battery includes multiple unit electrode laminates. Each unit electrode laminate includes at least a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer. The solid-state battery also includes an adhesive layer between two adjacent unit electrode laminates. The product of the area ratio of the adhesive layer on the surface of the unit electrode laminate in contact with the adhesive layer and the thickness of the unit electrode laminate is less than 12. The area ratio is expressed in percentage areas (%). The thickness is expressed in millimeters.

[0008] <2> According to <1> In the solid-state battery, the thickness of the unit electrode stack is 0.15 mm to 1 mm.

[0009] <3> According to <1> In solid-state batteries, the adhesive layer is conductive.

[0010] <4> According to <1> In a solid-state battery, the product of the area ratio of the adhesive layer on the surface of the unit electrode stack in contact with the adhesive layer and the thickness of the unit electrode stack is 8 or more and 12 or less.

[0011] According to this disclosure, a solid-state battery with excellent performance in suppressing interlayer delamination within the unit electrode stack can be provided. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein:

[0013] Figure 1 This is a schematic partial cross-sectional view of a solid-state battery according to an embodiment of the present disclosure. Detailed Implementation

[0014] In the following, a solid-state battery according to this disclosure will be described in detail with reference to the accompanying drawings. The figures shown below are schematic diagrams, and the dimensions and shapes of the parts have been appropriately enlarged for understanding.

[0015] solid-state batteries

[0016] The solid-state battery according to this disclosure comprises multiple unit electrode stacks. Each unit electrode stack includes at least a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer. The solid-state battery also includes an adhesive layer between two adjacent unit electrode stacks. The product of the area ratio (in area %) of the adhesive layer on the surface of the unit electrode stack in contact with the adhesive layer and the thickness (in mm) of the unit electrode stack is 12 or less.

[0017] In the following description, a solid-state battery according to this disclosure will be described with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic partial cross-sectional view of a solid-state battery according to an embodiment of the present disclosure.

[0019] Figure 1 The solid-state battery 10 contains multiple unit electrode stacks 22.

[0020] Figure 1 The unit electrode stack 22 includes a first current collector layer 12, a first active material layer 14, a solid electrolyte layer 16, a second active material layer 18, a second current collector layer 12, a second active material layer 18, a solid electrolyte layer 16, a first active material layer 14, and a third current collector layer 12.

[0021] The configuration of the layers in the unit electrode stack 22 in this disclosure is not particularly limited, as long as the unit electrode stack 22 includes at least a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer. The unit electrode stack 22 can be […]. Figure 1 The stack shown may also be a stack comprising a first current collector layer 12, a first active material layer 14, a solid electrolyte layer 16, a second active material layer 18, and a second current collector layer 12.

[0022] The number of stacked cell electrode stacks 22 in the solid-state battery 10 according to this disclosure is not particularly limited, as long as there are two or more, and can be, for example, 10 to 100.

[0023] The shape and size of the solid-state battery 10 according to this disclosure can be appropriately selected based on the number of stacked unit electrode layers 22, the desired shape, etc.

[0024] Figure 1 The solid-state battery 10 further includes an adhesive layer 20 between two adjacent unit electrode stacks 22. By providing the adhesive layer, interlayer delamination within the unit electrode stack can be suppressed. In particular, delamination of the active material layer (more specifically, the negative electrode active material layer) can be suppressed.

[0025] The adhesive layer 20 is preferably a layer that bonds the current collector layer 12 of the two unit electrode stacks 22.

[0026] There are no particular restrictions on the material of the adhesive layer 20, and known adhesives, tapes, adhesive films, etc. can be used.

[0027] The material of the adhesive layer 20 can be, for example, an adhesive or a thermoplastic resin, such as an acrylic resin, polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), butadiene rubber (BR), or styrene-butadiene rubber (SBR).

[0028] As thermoplastic resins, polyolefin resins can be used, and specific examples include low-density polyethylene (LDPE), ethylene-vinyl acetate copolymer resin (EVA), and polyimide (PI).

[0029] The adhesive layer 20 preferably has electrical properties.

[0030] There are no particular restrictions on the conductive material that imparts conductivity to the adhesive layer 20, and known conductive materials such as acetylene black, carbon black, or graphite can be used.

[0031] The thickness of the adhesive layer 20 is not particularly limited, but is preferably 10 μm to 1 mm, and more preferably 20 μm to 200 μm.

[0032] In the solid-state battery 10 according to this disclosure, the product of the area ratio (in area%) of the adhesive layer 20 on the surface of the unit electrode stack 22 in contact with the adhesive layer 20 and the thickness (in mm) of the unit electrode stack 22 is 12 or less. From the viewpoint of suppressing interlayer delamination within the unit electrode stack, this product is preferably 5 or more and 12 or less, more preferably 8 or more and 12 or less, and particularly preferably 9 or more and 11 or less.

[0033] From the viewpoint of suppressing interlayer delamination within the unit electrode stack, the area ratio of the adhesive layer 20 on the surface of the unit electrode stack 22 that contacts the adhesive layer 20 is preferably 10% or more and less than 100%, more preferably 30% to 85%, and particularly preferably 40% to 70%.

[0034] From the viewpoint of suppressing interlayer delamination within the unit electrode stack, the thickness T of the unit electrode stack 22 is preferably 0.10 mm to 2 mm, more preferably 0.15 mm to 1 mm, and particularly preferably 0.15 mm to 0.30 mm.

[0035] The solid-state battery 10 according to this disclosure may include a laminate sheet that covers the stack of the unit electrode stack 22 and the side members (e.g., terminals) and is thermally welded to the side members.

[0036] Components of a battery

[0037] The solid-state battery 10 according to this disclosure includes at least a first current collector layer 12 and a second current collector layer 12, and may also include a third current collector layer, a fourth current collector layer, etc.

[0038] The current collector layer 12, which includes a first current collector layer 12, a second current collector layer 12, etc., can be made of, for example, aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. The thickness of the current collector layer 12 can be, for example, from 1 μm to 100 μm.

[0039] The thicknesses of the current collector layer 12, the first active material layer 14, the second active material layer 18, etc., are the average values ​​measured at 10 appropriately selected points.

[0040] Preferably, one of the first active material layer 14 and the second active material layer 18 is a positive electrode active material layer, and the other is a negative electrode active material layer.

[0041] The positive electrode active material layer contains a positive electrode active material capable of storing and releasing charge carriers such as lithium ions. As the positive electrode active material, any material suitable for use as a positive electrode active material in lithium-ion secondary batteries can be used, such as lithium composite metal oxides having a layered rock salt structure, metal oxides having a spinel structure, or polyanionic compounds. Two or more positive electrode active materials can be used in combination. In this embodiment, the positive electrode active material layer contains olivine-type lithium iron phosphate (LiFePO4) as a composite oxide.

[0042] The negative electrode active material layer can be made of any element, alloy, or compound capable of storing and releasing charge carriers such as lithium ions, without any particular limitation. Examples of negative electrode active materials include Li, carbon, metal compounds, elements and compounds capable of alloying with lithium. Examples of carbon include natural graphite, artificial graphite, hard carbon (difficult-to-graphitize carbon), and soft carbon (easily-graphitize carbon). Examples of artificial graphite include highly oriented graphite and mesophase carbon microspheres. Examples of elements capable of alloying with lithium include silicon and tin. In this embodiment, the negative electrode active material layer contains graphite as a carbon-based material.

[0043] The positive and negative active material layers may each further contain conductive additives, binders, electrolytes (polymer matrix, ion-conducting polymer, electrolyte solution, etc.) to increase conductivity, and electrolyte support salts (lithium salts) to increase ion conductivity. There are no particular limitations on the components contained in the positive and negative active material layers, their blending ratio, or their thickness, and suitable reference can be made to known knowledge regarding lithium-ion secondary batteries. The thickness of each positive and negative active material layer is, for example, from 2 μm to 150 μm. Known methods, such as roll coating, can be used to form the positive or negative active material layer on the surface of the current collector layer 12. To improve the thermal stability of the positive or negative active material layer, a heat-resistant layer may be provided on the surface of the current collector layer 12 (one or both sides) or on the surface of the positive or negative active material layer. The heat-resistant layer contains, for example, inorganic particles and binders, and may also contain additives such as thickeners.

[0044] Conductive additives are added to increase the conductivity of the positive or negative electrode active material layer. Examples of conductive additives include acetylene black, carbon black, or graphite.

[0045] Examples of adhesives include fluorinated resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamide-imide; alkoxysilyl-containing resins; acrylic resins such as poly(meth)acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinkers; and starch-acrylic acid graft polymers. These adhesives can be used alone or in combination. Solvents can be, for example, water or N-methyl-2-pyrrolidone (NMP).

[0046] A separator is a component disposed between the positive and negative active material layers to separate them, thereby preventing short circuits caused by contact between the two electrodes and allowing charge carriers such as lithium ions to pass through. When bipolar electrodes are stacked, the separator prevents short circuits between adjacent bipolar electrodes.

[0047] The solid electrolyte layer 16 can be, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains the electrolyte. Examples of materials for the solid electrolyte layer 16 include polypropylene, polyethylene, polyolefins, and polyesters. The solid electrolyte layer 16 can have a single-layer or multi-layer structure. A multi-layer structure can include, for example, an adhesive layer, a ceramic layer used as a heat-resistant layer, etc. The solid electrolyte layer 16 can be impregnated with an electrolyte, or the solid electrolyte layer 16 itself can be composed of an electrolyte such as a polymeric electrolyte or an inorganic electrolyte.

[0048] Examples of electrolytes impregnated in a membrane include liquid electrolytes (electrolytes) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, and polymer gel electrolytes containing an electrolyte retained in a polymer matrix.

[0049] When the solid electrolyte layer 16 is impregnated with electrolyte, the electrolyte salt can be a known lithium salt, such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, or LiN(CF3SO2)2. As a non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, or ethers can be used. Two or more of these known solvent materials can be used in combination.

[0050] The side member can be a current collector side member. A current collector side member is a side member that includes a current collector portion in at least a portion. The current collector portion is electrically connected, for example, to the tab of a battery. The current collector side member can be entirely a current collector portion, or it can be a portion of a current collector portion. Examples of materials for the side member include metals such as stainless steel (SUS). The shape of the side member is not particularly limited and can be, for example, a cuboid shape.

[0051] The laminate comprises at least a metal layer, and preferably further comprises a solderable resin layer on the surface of the metal layer near the side member. The laminate may also comprise a protective layer on the surface of the metal layer opposite to the side member.

[0052] Examples of materials for the weldable resin layer include olefin resins such as polypropylene (PP) or polyethylene (PE). Examples of materials for the metal layer include aluminum, aluminum alloys, and stainless steel. Examples of materials for the protective layer include polyethylene terephthalate (PET) and nylon.

[0053] The thickness of the solderable resin layer is, for example, 40 μm or more and 100 μm or less. The thickness of the metal layer is, for example, 30 μm or more and 60 μm or less. The thickness of the protective layer is, for example, 20 μm or more and 60 μm or less. The total thickness of the laminate is, for example, 70 μm or more and 220 μm or less.

[0054] The battery includes a resin layer (e.g., an electrode membrane) disposed on the surfaces of a pair of sides of a side member. The resin layer is configured to cover a portion of the surface of the side member and is interposed between the side member and the laminate.

[0055] Examples of materials for the resin layer include olefin resins, such as polypropylene (PP) or polyethylene (PE). The thickness of the resin layer is, for example, greater than 40 μm and less than 100 μm.

[0056] Solid-state batteries according to this disclosure are typically lithium-ion rechargeable batteries. These batteries are used as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. In particular, the batteries are preferably used as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Solid-state batteries according to this disclosure can also be used as power sources for mobile bodies other than vehicles (e.g., trains, ships, and aircraft), or for electrical products such as information processing equipment.

[0057] This disclosure is not limited to the embodiments described above. The embodiments described above are exemplary, and anything having a configuration that is substantially the same as the technical concept described in the claims of this disclosure and having similar functions and effects is included within the technical scope of this disclosure.

[0058] The present disclosure will be described in detail below by way of examples. The following examples are not intended to limit the application of the present disclosure.

[0059] Example 1

[0060] 1. Formation of the negative electrode active material layer

[0061] Polyvinylidene fluoride (PVdF), negative electrode active material particles (lithium titanate (LTO) particles), and sulfide solid electrolyte (Li2S-P2S5 glass-ceramic) were added to a polypropylene container and stirred for 30 minutes using an ultrasonic dispersant. The mixture was then coated onto both sides of an aluminum foil at a width of 64 mm.

[0062] 2. Formation of the solid electrolyte layer

[0063] Heptane, butadiene rubber (BR), and a sulfide solid electrolyte (Li2S-P2S5 glass-ceramic) were added to a polypropylene container and stirred for 15 minutes using an ultrasonic disperser. The mixture was then coated in the center of an aluminum foil (120 mm wide) with a width of 70 mm.

[0064] 3. Formation of the positive electrode active material layer

[0065] The positive electrode active material particles (main phase Li) were coated in air using a rolling fluidized bed coating machine (manufactured by Powrex). 1.15 Co 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 particles are coated with lithium niobate and fired in an air atmosphere to produce positive electrode active material particles with a lithium niobate coating.

[0066] Polyvinylidene fluoride (PVdF), the obtained positive electrode active material particles, sulfide solid electrolyte (Li2S-P2S5 glass ceramic), and vapor-grown carbon fiber (VGCF, manufactured by Showa Denko) were added to a polypropylene container and stirred for 20 minutes using an ultrasonic dispersion device. The mixture was then coated in the center of an aluminum foil (120 mm wide).

[0067] 4. Preparation of the three-layer electrode

[0068] The obtained negative electrode active material layer, solid electrolyte layer, and positive electrode active material layer are cut into 80mm lengths. The solid electrolyte layer is rolled onto both sides of the laminate of negative electrode active material layer / aluminum foil / negative electrode active material layer at 0.4t / cm to align the center positions of the coated portions, and the aluminum foil is peeled off to transfer the solid electrolyte layer.

[0069] Then, the positive electrode active material layer is rolled onto each solid electrolyte layer at 0.4 t / cm, and the aluminum foil is peeled off to transfer the positive electrode active material layer.

[0070] 5. Densification

[0071] The obtained laminate was densified at 165℃ and 5t / cm to obtain a laminate with a thickness of 150μm.

[0072] Then, a polyimide (PI) strip cut to a width of 2 mm (thickness of 80 μm) is attached to a position 23 mm from the end of the foil.

[0073] In addition, the positive electrode active material layer is cut into areas with a width of 60 mm and a length of 60 mm.

[0074] 6. Attachment of the current collector layer

[0075] Acetylene black and acrylic adhesive, used as conductive materials, were weighed at a volume ratio of 20:80. Water was then added to prepare a carbon layer composition. Next, the carbon layer composition was coated onto one side of an aluminum foil at a thickness of 2 μm, and the foil was dried at 100°C for 1 hour to obtain an aluminum foil containing a carbon layer.

[0076] Then, the aluminum foil containing the carbon layer is cut into 57mm wide and 57mm long pieces, heated at 140℃ and 5MPa for 2 minutes, and then attached to both sides of the laminate to obtain a unit electrode laminate.

[0077] 7. Batteryization

[0078] Alternating stacks of unit electrode laminates and adhesive films (adhesive layers) having the adhesive areas shown in Table 1 were stacked, resulting in a total of 20 unit electrode laminates. Terminals were soldered, and the laminates were cell-formed to obtain a solid-state battery.

[0079] interlayer peeling evaluation

[0080] The manufactured solid-state battery was stored in a temperature-controlled chamber at 80°C and then disassembled. The occurrence of interlayer delamination within the unit electrode stack was evaluated. The evaluation results are shown in Table 1.

[0081] Examples 2 and 3 and Comparative Examples 1 and 2

[0082] As shown in Table 1, solid-state batteries were manufactured and evaluated in the same manner as in Example 1, except that the area ratio of the adhesive layer on the surface in contact with the adhesive layer and the thickness of the unit electrode stack were changed.

[0083]

[0084] Example 4

[0085] The processes from “1. Formation of the negative electrode active material layer” to “5. Densification” are performed in the same manner as in Example 1.

[0086] 6. Attachment of the current collector layer

[0087] Acetylene black and acrylic adhesive, used as conductive materials, were weighed at a volume ratio of 20:80. Water was then added to prepare a carbon layer composition. Next, the carbon layer composition was coated onto one side of an aluminum foil at a thickness of 2 μm, and the foil was dried at 100°C for 1 hour to obtain an aluminum foil containing a carbon layer.

[0088] Then, the aluminum foil containing the carbon layer is cut into 57mm wide and 57mm long pieces, heated at 140℃ and 5MPa for 2 minutes, and then attached to both sides of the laminate to obtain a unit electrode laminate.

[0089] 7. Batteryization

[0090] A single-electrode stack, an adhesive film (adhesive layer) with an area of ​​80% of the total area, and another single-electrode stack are stacked together. The center of the single-electrode stack is heated at 140°C and 5 MPa for 2 minutes in a 50 mm × 50 mm block. Then, the adhesive film (adhesive layer) with an area of ​​80% of the total area and another single-electrode stack are further stacked and heated. This process is repeated until a total of 20 single-electrode stacks are stacked. Terminals are soldered, and the stacks are cell-formed to obtain a solid-state battery.

[0091] The solid-state battery obtained in Example 4 was evaluated in the same manner as in Example 1, and no delamination was observed in the cell electrode stack.

[0092] As shown in Table 1 and Example 4, the solid-state batteries of Examples 1 to 4 are excellent in suppressing interlayer delamination within the unit electrode stack. In the solid-state batteries of Comparative Examples 1 and 2, delamination of the negative electrode active material layer occurs within the unit electrode stack.

Claims

1. A solid-state battery comprising multiple stacked unit electrodes, wherein Each of the unit electrode stacks comprises at least a first current collector layer, a first active material layer, a solid electrolyte layer, a second active material layer, and a second current collector layer. The solid-state battery further includes an adhesive layer between two adjacent unit electrode stacks, and On the surface of the unit electrode stack that contacts the adhesive layer, the product of the area ratio of the adhesive layer and the thickness of the unit electrode stack is less than 12. The area ratio is expressed in area % and the thickness is expressed in millimeters.

2. The solid-state battery according to claim 1, wherein, The thickness of the unit electrode stack is 0.15 mm to 1 mm.

3. The solid-state battery according to claim 1, wherein, The adhesive layer is conductive.

4. The solid-state battery according to claim 1, wherein, On the surface of the unit electrode stack that contacts the adhesive layer, the product of the area ratio of the adhesive layer and the thickness of the unit electrode stack is 8 or more and 12 or less.

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