Current collector, electrode plate, and battery

Abstract

This current collector (100) is provided with a substrate (101) and a coating layer (102) that coats the substrate (101), the coating layer (102) contains conductive carbon (103) and a first binder (104), the first binder (104) contains an aromatic super-engineering plastic, and the moisture content of the current collector (100) calculated on the basis of moisture generated from the current collector (100) when heated at 200 DEG C is 200 ppm by mass or less.

Description

Technical Field

[0001] The present disclosure relates to a current collector, an electrode plate, and a battery. Background Art

[0002] A current collector is an indispensable component in electrochemical devices such as batteries and capacitors. An electrode layer such as an active material layer is disposed on the current collector. The adhesion between the current collector and the electrode layer affects the performance of the electrochemical device. As a current collector capable of improving the adhesion, a current collector having a substrate and a coating layer is known.

[0003] Patent Document 1 describes a current collector for a storage device formed by forming a coating layer on one or both sides of a sheet-like metal substrate. The coating layer contains a powdery carbon material and a binder. The binder contains polyvinylidene fluoride (PVDF). The adhesion between the metal substrate and the active material layer is improved by the coating layer.

[0004] Patent Document 2 describes a current collector having a polymer layer containing a carbon material on the surface of a substrate. It is disclosed that the water content of the current collector is 275 ppm or less in terms of the water content measured by the Karl Fischer method.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-190527

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2010-3614 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] An object of the present disclosure is to provide a current collector suitable for achieving both the productivity of an electrochemical device and the high-temperature characteristics of the electrochemical device.

[0011] Means for Solving the Problems

[0012] The present disclosure provides a current collector including a substrate and a coating layer covering the substrate, the coating layer containing a conductive carbon and a first binder, the first binder containing an aromatic super engineering plastic, and the water content of the current collector calculated based on the water generated from the current collector when heated at 200°C being 200 mass ppm or less.

[0013] Effects of the Invention

[0014] According to the present disclosure, it is possible to provide a current collector suitable for achieving both the productivity of an electrochemical device and the high-temperature characteristics of the electrochemical device. Brief Description of the Drawings

[0015] Figure 1 Cross-sectional view of the current collector according to Embodiment 1.

[0016] Figure 2 Cross-sectional view of the electrode plate according to Embodiment 2.

[0017] Figure 3 Cross-sectional view of the battery according to Embodiment 3.

[0018] Figure 4 Cross-sectional view of the battery according to the modification. Detailed Description of the Invention

[0019] (Insight underlying the present disclosure)

[0020] In most cases, electrochemical devices do not like the presence of moisture. This is because the reaction of water with the electrolyte or the reaction of water with the active material promotes the deterioration of the electrochemical device. For example, in the case of a lithium secondary battery, the presence of moisture has an adverse effect on the cycle characteristics. In particular, when the lithium secondary battery is stored at a high temperature or operated, the adverse effect becomes significant.

[0021] As described in Patent Document 1 and Patent Document 2, PVDF is generally used as the material for the coating layer of the existing current collector. It is considered that PVDF is suitable for the production of current collectors with a low moisture content because of its lack of hygroscopicity.

[0022] On the other hand, in the manufacture of electrochemical devices, an electrode paste is often applied to the current collector to form a coating film, the coating film is dried, and the coating film is compressed. Thereby, an electrode having a current collector and an electrode layer is formed. Among them, since the size of the coating film cannot be made exactly the same as the size of the coating layer of the current collector, the coating film is smaller than the coating layer of the current collector. That is, sometimes the coating layer of the current collector has a portion not covered by the coating film. Therefore, when the coating film is compressed, the coating layer of the current collector may adhere to production equipment such as a press. In this case, in order to maintain the production equipment, the production line must be temporarily stopped. Stopping the production line means a deterioration in productivity.

[0023] Adhesion of the coating layer to the production equipment is likely to occur when a resin with slightly poor heat resistance such as PVDF is used for the coating layer of the current collector. Consider using a resin with excellent heat resistance for the coating layer, but such a resin sometimes shows a high moisture content due to unreacted components. That is, simply replacing PVDF with a resin with excellent heat resistance may deteriorate the high-temperature characteristics of the electrochemical device.

[0024] Therefore, a technique for balancing the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device is needed.

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0026] (Embodiment 1)

[0027] Figure 1 FIG. 7 is a cross-sectional view of the current collector 100 according to Embodiment 1. The current collector 100 includes a substrate 101 and a coating layer 102. The substrate 101 is coated with the coating layer 102. The coating layer 102 is in contact with the substrate 101. The coating layer 102 contains conductive carbon 103 and a first binder 104. The first binder 104 contains an aromatic super engineering plastic. The amount of moisture calculated based on the moisture generated from the current collector 100 during heating at 200°C is 200 mass ppm or less. The moisture can be measured by the Karl Fischer method.

[0028] According to the above configuration, even when the member including the current collector 100 is compressed at a high temperature during the manufacture of the electrochemical device, adhesion between the coating layer and the press can be suppressed, so the productivity of the electrochemical device can be improved. Furthermore, by controlling the moisture content of the current collector 100, deterioration of electrode materials such as active materials and electrolytes can be suppressed, so the high-temperature characteristics of the electrochemical device can be improved. For example, the high-temperature cycle characteristics of the battery can be improved. According to the present embodiment, both the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device can be achieved.

[0029] If the moisture content during heating at 200°C is adjusted to 200 mass ppm or less, the high-temperature characteristics of the electrochemical device can be improved.

[0030] The current collector 100 can be used, for example, in electrode plates of electrochemical devices such as batteries and capacitors. The battery can be a non-aqueous electrolyte battery or a solid battery. The current collector 100 is particularly suitable for all-solid secondary batteries.

[0031] <Current Collector>

[0032] In the current collector 100, the coating layer 102 contains an aromatic super engineering plastic.

[0033] The amount of moisture calculated based on the moisture generated from the current collector 100 during heating at 200°C can be 1 mass ppm or more and 180 mass ppm or less, can be 5 mass ppm or more and 150 mass ppm or less, can be 10 mass ppm or more and 100 mass ppm or less, or can be 20 mass ppm or more and 80 mass ppm or less.

[0034] The moisture generated during heating can be determined using a moisture measurement device based on the coulometric titration method. The principle of moisture measurement is based on the Karl Fischer method. For example, using a moisture measurement device (CA-310) manufactured by Nitto Seiko Analysis Co., Ltd., the moisture (μg) generated from the current collector 100 when heated from 100 °C to 200 °C or 300 °C is measured. The ratio of the moisture (μg) to the mass (g) of the current collector 100 is the moisture content (μg / g = mass ppm).

[0035] The moisture content calculated based on the moisture generated from the current collector 100 during heating at 300 °C can be 1 mass ppm or more and 400 mass ppm or less, or 5 mass ppm or more and 300 mass ppm or less, or 10 mass ppm or more and 200 mass ppm or less, or 20 mass ppm or more and 150 mass ppm or less. By adjusting the moisture content during heating at 300 °C to 1 mass ppm or more and 400 mass ppm, the long-term cycle characteristics of the electrochemical device can be improved.

[0036] The current collector 100 has, for example, a plate-like or foil-like shape. The thickness of the current collector 100 can be 0.1 μm or more and 1 mm or less, or 1 μm or more and 100 μm or less, or 10 μm or more and 50 μm or less. When the thickness of the current collector 100 is 0.1 μm or more, the strength of the current collector 100 is increased, so breakage of the current collector 100 is suppressed. When the thickness of the current collector 100 is 1 mm or less, the energy density of the electrochemical device can be increased by lightening the current collector 100. That is, by appropriately adjusting the thickness of the current collector 100, the electrochemical device can be stably manufactured and the energy density of the electrochemical device can be increased.

[0037] The tensile strength of the current collector 100 is, for example, 120 N / mm 2 or more. With such a configuration, even if the member including the current collector 100 is compressed at a high temperature, breakage of the current collector is suppressed, and the productivity of the electrochemical device can be further improved. The tensile strength of the current collector 100 can be 150 N / mm 2 or more, or 200 N / mm 2 or more, or 250 N / mm 2 or more. There is no particular limitation on the upper limit of the tensile strength of the current collector 100. The upper limit is, for example, 800 N / mm 2 .

[0038] <Coating layer>

[0039] The coating layer 102 can entirely coat the main surface of the substrate 101, or can partially coat the main surface of the substrate 101. The "main surface" refers to the surface of the substrate 101 having the largest area. The shape of the coating layer 102 can be dot-shaped, strip-shaped, etc.

[0040] Examples of the conductive carbon 103 contained in the coating layer 102 include graphite-based materials such as natural graphite and artificial graphite, carbon black-based materials such as acetylene black (AB) and Ketjen black (KB), conductive fiber-based materials such as carbon fiber (CF), vapor-grown carbon fiber (VGCF (registered trademark)), carbon nanotubes (CNT), and nano-carbon-based materials such as graphene. As the conductive carbon, one conductive carbon selected from the above can be used alone, or two or more conductive carbons selected from the above can be used.

[0041] The first binder 104 contained in the coating layer 102 includes aromatic super engineering plastics. The so-called aromatic super engineering plastics refer to engineering plastics that contain aromatic rings in the main chain skeleton and can be continuously used at a temperature of 150 °C or higher. Examples of aromatic super engineering plastics include polybenzimidazole (PBI), polyimide (PI), polyetherketoneetherketoneketone (PEKEKK), polyamideimide (PAI), polyetheretherketone (PEEK), polyetherketone (PEK), liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), polysulfone (PSU), polyparaphenylene (PPP), polyarylate (PAR), etc. As the first binder 104, a mixture containing two or more selected from the above can be used. Aromatic super engineering plastics exhibit high heat resistance. Therefore, when the aromatic super engineering plastics are contained in the coating layer 102 as the first binder 104, even if the member including the current collector 100 is compressed at a high temperature, the coating layer 102 is not easily adhered to production equipment such as a press. As a result, the productivity of the electrochemical device is improved.

[0042] The aromatic super engineering plastics can contain at least one selected from polyimide and polyethersulfone.

[0043] The imidization rate of the polyimide can be 90% or more. An imidization rate of 90% or more means that the amount of polyamic acid contained in the polyimide is small. Polyamic acid has a carboxylic acid group and easily adsorbs water. In addition, water is released during cyclization. Therefore, by having an imidization rate of 90% or more, that is, reducing the content of polyamic acid, the moisture content of the current collector 100 can be reduced. The imidization rate of the polyimide can be 95% or more, and the imidization rate can be 99% or more.

[0044] The so-called imidization rate refers to the reaction rate of the imidization reaction in which polyamic acid, which is a precursor of polyimide, is heated to form polyimide produced by thermal imidization. The imidization rate of polyimide can be determined using a Fourier transform infrared spectrophotometer (FT-IR) by the total reflection measurement method (ATR method). For example, it can be measured using a small-sized FT-IR (ALPHAII) manufactured by Bruker Corporation. More specifically, the absorbance (a -1 ) around 1350 cm CN derived from the CN stretching vibration of the polyimide contained in the surface of the coating layer 102 and the absorbance (a -1 ) around 1500 cm Ar derived from the benzene ring skeleton are obtained. Next, a sample treated under the conditions of temperature and time for completely imidizing the polyimide to be measured (imidization rate: 100%) is prepared, and the absorbance (A -1 ) around 1350 cm CN derived from the CN stretching vibration and the absorbance (A -1 ) around 1500 cm Ar derived from the benzene ring skeleton are obtained. Then, the imidization rate is obtained using the following calculation formula.

[0045] Imidization rate (%) = [(a CN / a Ar ) / (A CN / A Ar )]×100

[0046] Polyimide has a tendency to exhibit higher heat resistance. Therefore, if polyimide is used, the effect of suppressing the adhesion of the coating layer 102 to the production equipment is improved. As a result, the productivity of the electrochemical device is further improved. As the polyimide, a soluble polyimide capable of preparing a polyimide solution can be used. Soluble polyimide can easily produce polyimide with a high imidization rate, and thus is more excellent from the viewpoint of reducing the moisture content.

[0047] Polyethersulfone has a tendency to exhibit higher heat resistance. Therefore, if polyethersulfone is used, the effect of suppressing the adhesion of the coating layer 102 to the production equipment is improved. As a result, the productivity of the electrochemical device is further improved.

[0048] The first adhesive 104 may contain a supplementary adhesive other than aromatic super engineering plastics. Alternatively, the first adhesive 104 may be an aromatic super engineering plastic. In other words, the first adhesive 104 may contain only aromatic super engineering plastics.

[0049] Examples of the supplementary binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, hexyl polyacrylate, polymethacrylic acid, polymethyl methacrylate (PMMA), ethyl polymethacrylate, hexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyethersulfone, polyether ketone, polyetherether ketone, polyphenylene sulfide, hexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, ethyl cellulose, etc. As the supplementary binder, a copolymer synthesized from two or more monomers selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, isoprene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylate, acrylic acid, and hexadiene may also be used. As the supplementary binder, one selected from the above may be used alone, or a mixture containing two or more selected from the above may be used.

[0050] From the viewpoint of excellent adhesiveness, the supplementary binder may contain an elastomer. An elastomer refers to a polymer having rubber elasticity. The elastomer used as the binder may be a thermoplastic elastomer or a thermosetting elastomer. As the elastomer, in addition to the above-mentioned styrene-based elastomer, butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), acrylate-butadiene rubber (ABR), etc. may be mentioned. A mixture containing two or more selected from the above may be used.

[0051] The content rate of the first binder 104 in the coating layer 102 is not particularly limited. For example, it is 20% by mass or more and 95% by mass or less, may also be 40% by mass or more and 90% by mass or less, or may also be 55% by mass or more and 85% by mass or less. When the content rate of the first binder 104 is 95% by mass or less, the conductivity of the coating layer 102 is improved, and thus high output of the electrochemical device can be achieved. When the content rate of the first binder 104 is 20% by mass or more, the peeling of the coating layer 102 is likely to be suppressed because the first binder 104 and the like are sufficiently present.

[0052] The coating layer 102 may contain a conductive material other than the conductive carbon 103. Examples of the conductive material other than the conductive carbon include conductive fiber materials such as metal fibers, conductive powder materials such as carbon fluoride and aluminum, conductive whisker materials such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene.

[0053] The coating layer 102 may contain other elements or components in addition to the conductive carbon 103 and the first binder 104. The other elements or components may be added to the coating layer 102 due to contamination or the like. For example, an inevitable oxide film or the like may be formed on a part of the surface of the coating layer 102. That is, the coating layer 102 may contain inevitable oxides or the like.

[0054] The coating layer 102 can be produced, for example, by a method of sputtering the material of the coating layer 102 onto the surface of the substrate 101. The coating layer 102 can be produced by coating a solution or dispersion containing the material of the coating layer 102 on the surface of the substrate 101. The coating of the solution or dispersion can be carried out using a gravure coater, a slot die coater, or the like.

[0055] There is no particular limitation on the mass per unit area of the coating layer 102. For example, it can be 0.01 g / m 2 or more and 5 g / m 2 or less, and can also be 0.1 g / m 2 or more and 3 g / m 2 or less, and can also be 0.5 g / m 2 or more and 2 g / m 2 or less. When the mass per unit area is 0.01 g / m 2 or more, contact between the substrate 101 and the electrode layer can be prevented, and thus corrosion of the substrate 101 can be suppressed. When the mass per unit area is 5 g / m 2 or less, the resistance of the coating layer 102 is reduced, and for an electrochemical device, operation at high output can be easily carried out.

[0056] There is no particular limitation on the thickness of the coating layer 102. For example, it can be 0.001 μm or more and 10 μm or less, can also be 0.01 μm or more and 5 μm or less, and can also be 0.1 μm or more and 3 μm or less. When the thickness of the coating layer 102 is 0.001 μm or more, contact between the substrate 101 and the electrode layer can be prevented, and thus corrosion of the substrate 101 can be suppressed. When the thickness of the coating layer 102 is 10 μm or less, the resistance of the coating layer 102 is reduced, and for an electrochemical device, operation at high output can be easily carried out.

[0057] <Substrate>

[0058] The substrate 101 has, for example, a foil-like or plate-like shape. As the material of the substrate 101, a metal or an alloy can be used. As the metal, aluminum, iron, nickel, copper, etc. can be cited. As the alloy, aluminum alloy, stainless steel (SUS), etc. can be cited. The substrate 101 may contain aluminum or an aluminum alloy.

[0059] The substrate 101 may contain aluminum as a main component. "The substrate 101 contains aluminum as a main component" means that the content rate of aluminum in the substrate 101 is 50% by mass or more. Aluminum is a light metal with high electrical conductivity. Therefore, the electrode plate 1000 having the substrate 101 containing aluminum as a main component can improve the mass energy density of the electrochemical device. The substrate 101 containing aluminum as a main component may further contain elements other than aluminum. It should be noted that when the substrate 101 contains only aluminum, that is, when the content rate of aluminum in the substrate 101 is 100%, the strength of the substrate 101 sometimes decreases. Therefore, the substrate 101 may contain elements other than aluminum. The content rate of aluminum in the substrate 101 may be 99% by mass or less, or may be 90% by mass or less.

[0060] The substrate 101 may contain an aluminum alloy. The aluminum alloy is light and has high strength. Therefore, the current collector 100 having the substrate 101 containing the aluminum alloy can realize an electrochemical device having both high mass energy density and high durability. The aluminum alloy is not particularly limited, and examples thereof include Al-Cu alloy, Al-Mn alloy, Al-Mn-Cu alloy, Al-Fe-Cu alloy, etc.

[0061] As the material of the substrate 101, an Al-Mn alloy can be used. The Al-Mn alloy has high strength and excellent formability and corrosion resistance. Therefore, the current collector 100 having the substrate 101 containing the Al-Mn alloy can improve the cycle characteristics of the electrochemical device.

[0062] The thickness of the substrate 101 is not particularly limited. For example, it is 0.1 μm or more and 50 μm or less, or may be 1 μm or more and 30 μm or less. When the thickness of the substrate 101 is 0.1 μm or more, the strength of the substrate 101 is improved, and thus breakage of the substrate 101 is suppressed. When the thickness of the substrate 101 is 50 μm or less, the mass of the substrate 101 is reduced, and the mass energy density of the electrochemical device can be improved.

[0063] (Embodiment 2)

[0064] Figure 2 It is a cross-sectional view of the electrode plate 1000 according to Embodiment 2. The electrode plate 1000 in Embodiment 2 includes a current collector 100 and an electrode layer 110. The current collector 100 refers to those described in Embodiment 1. The coating layer 102 of the current collector 100 is provided between the substrate 101 and the electrode layer 110 and is in contact with the substrate 101 and the electrode layer 110, respectively. The electrode layer 110 contains a second binder 113.

[0065] According to the electrode plate 1000, even when the electrode plate 1000 is compressed at a high temperature during the manufacture of the electrochemical device, adhesion between the coating layer 102 and the press can be suppressed, so the productivity of the electrochemical device can be improved. Furthermore, by controlling the moisture content of the current collector 100, deterioration of materials such as the active material 112 and the solid electrolyte 111 can be suppressed, so the high-temperature characteristics of the electrochemical device can be improved. Typically, the high-temperature cycle characteristics of the battery can be improved. According to the present embodiment, the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device can be balanced.

[0066] The electrode layer 110 may include the solid electrolyte 111, may include the active material 112, or may include both. The electrode plate 1000 is suitable for an electrochemical device, particularly a battery, that includes at least one selected from the solid electrolyte 111 and the active material 112 in the electrode layer 110.

[0067] <Solid electrolyte>

[0068] The solid electrolyte 111 may include a sulfide solid electrolyte. The sulfide solid electrolyte may include lithium. By using a sulfide solid electrolyte having lithium as the solid electrolyte 111, a lithium secondary battery using the electrode plate 1000 including the sulfide solid electrolyte can be manufactured.

[0069] The solid electrolyte 111 may include a solid electrolyte other than a sulfide solid electrolyte, such as an oxide solid electrolyte, a halide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte. Alternatively, the solid electrolyte 111 may be a sulfide solid electrolyte. In other words, the solid electrolyte 111 may include only a sulfide solid electrolyte.

[0070] In the present disclosure, the so-called "oxide solid electrolyte" refers to a solid electrolyte containing oxygen. The oxide solid electrolyte may further include an anion other than oxygen as an anion other than sulfur and a halogen element.

[0071] In the present disclosure, the so-called "halide solid electrolyte" refers to a solid electrolyte containing a halogen element and not containing sulfur. In the present disclosure, the so-called solid electrolyte not containing sulfur refers to a solid electrolyte represented by a compositional formula not containing a sulfur element. Therefore, a solid electrolyte having a very small amount of sulfur component, for example, a solid electrolyte having sulfur of 0.1 mass% or less, is included in the solid electrolyte not containing sulfur. The halide solid electrolyte may further include oxygen as an anion other than the halogen element.

[0072] As the sulfide solid electrolyte, for example, Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li10 GeP2S 12 etc. LiX, Li2O, MO can be added to the above-mentioned substances. q , Li p MO q etc. Element X in "LiX" is at least one selected from F, Cl, Br, and I. "MO q " and "Li p MO q " Element M is at least one selected from P, Si, Ge, B, Al, Ga, In, Fe, and Zn. "MO q " and "Li p MO q " p and q are each independently natural numbers.

[0073] As the sulfide solid electrolyte, for example, Li2S-P2S5-based glass ceramics can be used. LiX, Li2O, MO q , Li p MO q etc. can be added, and two or more selected from LiCl, LiBr, and LiI can be added. Since the Li2S-P2S5-based glass ceramics are relatively soft materials, the electrode plate 1000 containing the Li2S-P2S5-based glass ceramics can be used to manufacture a battery with high durability.

[0074] As the oxide solid electrolyte, for example, NASICON-type solid electrolytes represented by LiTi2(PO4)3 and its elemental substitution products, perovskite-type solid electrolytes of the (LaLi)TiO3 system, and Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4 and their elemental substitution products, garnet-type solid electrolytes represented by Li7La3Zr2O 12 and its elemental substitution products, Li3PO4 and its N substitution products, glasses and glass ceramics based on Li-B-O compounds such as LiBO2 and Li3BO3 and added with Li2SO4, Li2CO3, etc.

[0075] The halide solid electrolyte contains, for example, Li, M1, and X. M1 is at least one selected from metal elements and metalloid elements other than Li. X is at least one selected from F, Cl, Br, and I. The halide solid electrolyte has high thermal stability, so it can improve the safety of the battery. Furthermore, since the halide solid electrolyte does not contain sulfur, it can control the generation of hydrogen sulfide gas.

[0076] In the present disclosure, "metalloid element" refers to B, Si, Ge, As, Sb, and Te.

[0077] In the present disclosure, the "metal element" refers to all elements contained in Groups 1 to 12 of the periodic table except hydrogen, and all elements contained in Groups 13 to 16 of the periodic table except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se.

[0078] That is, in the present disclosure, the "metalloid element" and the "metal element" are a group of elements that can become cations when forming an inorganic compound with a halogen element.

[0079] For example, the halide solid electrolyte may be a material represented by the following compositional formula (1).

[0080] Li α M1 β X γ Formula (1)

[0081] In the above compositional formula (1), α, β, and γ are each independently a value greater than 0. γ can be 4, 6, etc.

[0082] According to the above configuration, the ionic conductivity of the halide solid electrolyte will be improved. Therefore, the ionic conductivity of the electrode plate 1000 can be improved. When the electrode plate 1000 is used in a battery, the cycle characteristics of the battery can be further improved.

[0083] In the above compositional formula (1), the element M1 may contain Y (=yttrium). That is, the halide solid electrolyte may contain Y as a metal element.

[0084] The halide solid electrolyte containing Y can be represented by, for example, the following compositional formula (2).

[0085] Li a Me b Y c X6 Formula (2)

[0086] In formula (2), a, b, and c may satisfy a + mb + 3c = 6, and c > 0. The element Me is at least one selected from metal elements and metalloid elements other than Li and Y. m represents the valence of the element Me. It should be noted that when the element Me contains multiple elements, mb is the sum of the product of the composition ratio of each element and the valence of the element. For example, when Me contains element Me1 and element Me2, the composition ratio of element Me1 is b1, the valence of element Me1 is m1, the composition ratio of element Me2 is b2, and the valence of element Me2 is m2, mb is represented by m1b1 + m2b2. In the above compositional formula (2), the element X is at least one selected from F, Cl, Br, and I.

[0087] The element Me can be, for example, at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, Gd, and Nb.

[0088] As the halide solid electrolyte, for example, the following materials can be used. According to the following materials, the ionic conductivity of the solid electrolyte 111 is further improved, and the output characteristics of the battery can be further improved.

[0089] The halide solid electrolyte can be a material represented by the following compositional formula (A1).

[0090] Li 6-3d Y d X6 Formula (A1)

[0091] In the compositional formula (A1), the element X is at least one selected from Cl, Br, and I. In the compositional formula (A1), d satisfies 0 < d < 2.

[0092] The halide solid electrolyte can be a material represented by the following compositional formula (A2).

[0093] Li3YX6 Formula (A2)

[0094] In the compositional formula (A2), the element X is at least one selected from Cl, Br, and I.

[0095] The halide solid electrolyte can be a material represented by the following compositional formula (A3).

[0096] Li 3-3δ Y 1+δ Cl6 Formula (A3)

[0097] In the compositional formula (A3), δ satisfies 0 < δ ≤ 0.15.

[0098] The halide solid electrolyte can be a material represented by the following compositional formula (A4).

[0099] Li 3-3δ Y 1+δ Br6 Formula (A4)

[0100] In the compositional formula (A4), δ satisfies 0 < δ ≤ 0.25.

[0101] The halide solid electrolyte can be a material represented by the following compositional formula (A5).

[0102] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y Formula (A5)

[0103] In the compositional formula (A5), the element Me is at least one selected from Mg, Ca, Sr, Ba, and Zn.

[0104] Furthermore, in the above compositional formula (A5), the following conditions are satisfied:

[0105] -1 < δ < 2,

[0106] 0 < a < 3,

[0107] 0 < (3 - 3δ + a),

[0108] 0 < (1 + δ - a),

[0109] 0 ≤ x ≤ 6,

[0110] 0 ≤ y ≤ 6, and (x + y) ≤ 6.

[0111] The halide solid electrolyte can be a material represented by the following compositional formula (A6).

[0112] Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y Formula (A6)

[0113] In the compositional formula (A6), the element Me is at least one selected from Al, Sc, Ga, and Bi. Furthermore, in the above compositional formula (A6), the following conditions are satisfied:

[0114] -1 < δ < 1,

[0115] 0 < a < 2,

[0116] 0 < (1 + δ - a),

[0117] 0 ≤ x ≤ 6,

[0118] 0 ≤ y ≤ 6, and (x + y) ≤ 6.

[0119] The halide solid electrolyte can be a material represented by the following compositional formula (A7).

[0120] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y Formula (A7)

[0121] In the above compositional formula (A7), the element Me is at least one selected from Zr, Hf, and Ti. Furthermore, in the above compositional formula (A7), the following conditions are satisfied:

[0122] -1 < δ < 1,

[0123] 0 < a < 1.5,

[0124] 0 < (3 - 3δ - a),

[0125] 0 < (1 + δ - a),

[0126] 0 ≤ x ≤ 6,

[0127] 0 ≤ y ≤ 6, and

[0128] (x + y) ≤ 6.

[0129] The halide solid electrolyte may be a material represented by the following compositional formula (A8).

[0130] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y Compositional formula (A8)

[0131] In the compositional formula (A8), the element Me is at least one selected from Ta and Nb.

[0132] Furthermore, in the above compositional formula (A8), the following are satisfied:

[0133] -1 < δ < 1,

[0134] 0 < a < 1.2,

[0135] 0 < (3 - 3δ - 2a),

[0136] 0 < (1 + δ - a),

[0137] 0 ≤ x ≤ 6,

[0138] 0 ≤ y ≤ 6, and

[0139] (x + y) ≤ 6.

[0140] The halide solid electrolyte may be a compound containing Li, M2, O (oxygen), and X2. The element M2 includes, for example, at least one selected from Nb and Ta. Additionally, X2 is at least one selected from F, Cl, Br, and I.

[0141] The compound containing Li, M2, X2, and O (oxygen) may be represented, for example, by the compositional formula: Li x M2O y X2 5+x-2y where x may satisfy 0.1 < x < 7.0. y may satisfy 0.4 < y < 1.9.

[0142] As a halide solid electrolyte, more specifically, for example, Li3Y(Cl, Br, I)6, Li 2.7 Y 1.1 (Cl, Br, I)6, Li2Mg(F, Cl, Br, I)4, Li2Fe(F, Cl, Br, I)4, Li(Al, Ga, In)(F, Cl, Br, I)4, Li3(Al, Ga, In)(F, Cl, Br, I)6, Li3(Ca, Y, Gd)(Cl, Br, I)6, Li 2.7 (Ti, Al)F6, Li 2.5 (Ti, Al)F6, Li(Ta, Nb)O(F, Cl)4, etc. It should be noted that in the present disclosure, when an element in a formula is represented as "(Al, Ga, In)", this notation means at least one element selected from the group of elements within the parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one selected from Al, Ga, and In". The same applies to other elements.

[0143] As a polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound can have an ethylene oxide structure. The polymer compound having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further improved. As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, etc. can be used. The lithium salt can be used alone or two or more can be used in combination.

[0144] As a complex hydride solid electrolyte, for example, LiBH4-LiI, LiBH4-P2S5, etc. can be used.

[0145] The shape of the solid electrolyte 111 is not particularly limited and can be needle-shaped, spherical, ellipsoidal, etc. The shape of the solid electrolyte 111 can be particulate.

[0146] When the shape of the solid electrolyte 111 is particulate (e.g., spherical), the median diameter of the solid electrolyte 111 can be 0.1 μm or more and 5 μm or less, or can be 0.5 μm or more and 3 μm or less. When the median diameter of the solid electrolyte 111 is 0.1 μm or more, the dispersibility of the electrode composition (slurry) for manufacturing the electrode plate 1000 is improved and a denser structure can be obtained. When the median diameter of the solid electrolyte 111 is 5 μm or less, the electrode plate 1000 has high surface smoothness and a denser structure can be obtained.

[0147] The so-called median diameter refers to the particle diameter at which the cumulative volume in the particle size distribution based on volume is equal to 50%. The particle size distribution based on volume is obtained by the laser diffraction scattering method. The same applies to the following other materials.

[0148] The specific surface area of the solid electrolyte 111 can be 0.1 m 2 / g or more and 100 m 2 / g or less, and can also be 1 m 2 / g or more and 10 m 2 / g or less. When the specific surface area of the solid electrolyte 111 is 0.1 m 2 / g or more and 100 m 2 / g or less, the dispersibility of the electrode composition (slurry) for manufacturing the electrode plate 1000 is improved, and a denser structure can be obtained. The specific surface area can be measured by the BET multipoint method using a gas adsorption amount measuring device.

[0149] The ionic conductivity of the solid electrolyte 111 can be 0.01 mS / cm 2 or more, and can also be 0.1 mS / cm 2 or more, and can also be 1 mS / cm 2 or more. When the ionic conductivity of the solid electrolyte 111 is 0.01 mS / cm 2 or more, the output characteristics of the battery can be improved.

[0150] <Active material>

[0151] The active material 112 contains a material having the property of storing and releasing metal ions (such as lithium ions). The active material 112 includes, for example, a positive electrode active material or a negative electrode active material. When the electrode plate 1000 contains the active material 112, a lithium secondary battery can be manufactured using the electrode plate 1000.

[0152] The active material 112 includes, for example, a material having the property of storing and releasing metal ions (such as lithium ions) as a positive electrode active material. As the positive electrode active material, transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, and their lithium-containing compounds can be mentioned. As the lithium-containing transition metal oxide, Li(NiCoAl)O2, Li(NiCoMn)O2, LiCoO2, etc. can be mentioned. When using a lithium-containing transition metal oxide as the positive electrode active material, for example, the manufacturing cost of the electrode plate 1000 can be reduced, and the average discharge voltage of the battery can be increased. Li(NiCoAl)O2 means containing Ni, Co, and Al at an arbitrary ratio. Li(NiCoMn)O2 means containing Ni, Co, and Mn at an arbitrary ratio.

[0153] The median diameter of the positive electrode active material may be 0.1 μm or more and 100 μm or less, or may be 1 μm or more and 10 μm or less. When the median diameter of the positive electrode active material is 0.1 μm or more, in the electrode plate 1000, the active material 112 and the solid electrolyte 111 can be well dispersed. Thereby, the charge-discharge characteristics of the battery are improved. When the median diameter of the positive electrode active material is 100 μm or less, the lithium diffusion rate in the positive electrode active material is increased. Therefore, the battery can operate at a high output.

[0154] The active material 112 contains, for example, a material having the property of absorbing and releasing metal ions (such as lithium ions) as the negative electrode active material. Examples of the negative electrode active material include metal materials, carbon materials, oxides, nitrides, tin compounds, and silicon compounds. The metal material may be a single metal or an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, carbon in the middle of graphitization, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. By using silicon (Si), tin (Sn), silicon compounds, tin compounds, etc., the capacity density of the battery can be increased. By using an oxide compound containing titanium (Ti) or niobium (Nb), the safety of the battery can be improved.

[0155] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less, or may be 1 μm or more and 10 μm or less. When the median diameter of the negative electrode active material is 0.1 μm or more, in the electrode plate 1000, the active material 112 and the solid electrolyte 111 can be well dispersed. Thereby, the charge-discharge characteristics of the battery are improved. When the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion rate in the negative electrode active material is increased. Therefore, the battery can operate at a high output.

[0156] In order to reduce the interfacial resistance between each active material and the solid electrolyte, the positive electrode active material and the negative electrode active material can be coated with a coating material. That is, a coating layer can be provided on the surfaces of the positive electrode active material and the negative electrode active material. The coating layer is a layer containing the coating material. As the coating material for the coating layer, a material with low electronic conductivity can be used. As the coating material for the coating layer, oxide materials, oxide solid electrolytes, halide solid electrolytes, sulfide solid electrolytes, etc. can be used. The positive electrode active material and the negative electrode active material can be coated with only one coating material selected from the above materials. That is, for the coating layer, a coating layer formed of only one coating material selected from the above materials can be provided. Alternatively, two or more coating materials selected from the above materials can be used to provide two or more coating layers.

[0157] Examples of the oxide material as the coating material for the coating layer include SiO2, Al2O3, TiO2, B2O3, Nb2O5, WO3, ZrO2, etc.

[0158] As the oxide solid electrolyte as the coating material for the coating layer, the oxide solid electrolytes exemplified previously can be used. For example, Li-Nb-O compounds such as LiNbO3, Li-B-O compounds such as LiBO2 and Li3BO3, Li-Al-O compounds such as LiAlO2, Li-Si-O compounds such as Li4SiO4, Li-S-O compounds such as Li2SO4, Li-Ti-O compounds such as Li4Ti5O 12 etc., Li-Zr-O compounds such as Li2ZrO3, Li-Mo-O compounds such as Li2MoO3, Li-V-O compounds such as LiV2O5, Li-W-O compounds such as Li2WO4, Li-P-O compounds such as LiPO4, etc. The oxide solid electrolyte has high potential stability. Therefore, by using the oxide solid electrolyte as the coating material, the cycle characteristics of the battery can be further improved.

[0159] As the halide solid electrolyte as the coating material for the coating layer, the halide solid electrolytes exemplified previously can be used. For example, Li-Y-Cl compounds such as LiYCl6, Li-Y-Br-Cl compounds such as LiYBr2Cl4, Li-Ta-O-Cl compounds such as LiTaOCl4, Li 2.7 Ti 0.3 Al 0.7 F6 and other Li-Ti-Al-F compounds, etc. The halide solid electrolyte has high ionic conductivity and high potential stability. Therefore, by using the halide solid electrolyte as the coating material, the cycle characteristics of the battery can be further improved.

[0160] As the sulfide solid electrolyte as the coating material for the coating layer, the sulfide solid electrolytes exemplified previously can be used. For example, Li-P-S compounds such as Li2S-P2S5, etc. The sulfide solid electrolyte has high ionic conductivity and low Young's modulus. Therefore, by using the sulfide solid electrolyte as the coating material, uniform coating can be achieved, and the cycle characteristics of the battery can be further improved.

[0161] <Second Adhesive>

[0162] The second adhesive 113 can improve the adhesiveness between the particles of the solid electrolyte 111 and the active material 112 in the electrode plate 1000. In addition, it can improve the adhesiveness between the electrode layer 110 and the current collector 100 in the electrode plate 1000. As the second adhesive 113, the supplementary adhesives described in Embodiment 1 can be used.

[0163] The second adhesive 113 may contain a styrenic elastomer. A styrenic elastomer refers to an elastomer containing repeating units derived from styrene. A repeating unit refers to the molecular structure derived from a monomer, and is sometimes also referred to as a structural unit. Since the styrenic elastomer has excellent flexibility and elasticity, it is suitable as an adhesive for the electrode plate 1000. There is no particular limitation on the content ratio of the repeating units derived from styrene in the styrenic elastomer, for example, it is 5% by mass or more and 70% by mass or less.

[0164] The styrenic elastomer may be a block copolymer containing a first block composed of repeating units derived from styrene and a second block composed of repeating units derived from a conjugated diene. Examples of the conjugated diene include butadiene and isoprene. The repeating units derived from the conjugated diene may be hydrogenated. That is, the repeating units derived from the conjugated diene may have an unsaturated bond such as a carbon-carbon double bond, or may not have an unsaturated bond such as a carbon-carbon double bond. The block copolymer may have an arrangement of a triblock composed of two first blocks and one second block. The block copolymer may be an ABA-type triblock copolymer. In this triblock copolymer, the A block corresponds to the first block, and the B block corresponds to the second block. The first block functions as a hard segment, for example. The second block functions as a soft segment, for example.

[0165] Examples of the styrenic elastomer include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-butadiene rubber (HSBR), etc. The second adhesive 113 may contain SBR or SEBS as the styrenic elastomer. As the second adhesive 113, a mixture containing two or more selected from the above may be used. Since the styrenic elastomer has excellent flexibility and elasticity, it is suitable as an adhesive for the electrode layer 110.

[0166] The styrenic elastomer may be a styrenic triblock copolymer. Examples of the styrenic triblock copolymer include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), etc. These styrenic triblock copolymers are sometimes referred to as styrenic thermoplastic elastomers. These styrenic triblock copolymers tend to be soft and have high strength.

[0167] The styrenic elastomer may include a styrene-ethylene / butylene-styrene block copolymer (SEBS). Since SEBS has excellent flexibility and elasticity and excellent filling properties during hot compression, it is particularly suitable as an adhesive for the electrode layer 110.

[0168] The styrenic elastomer may include a modifying group. The so-called modifying group refers to a functional group that chemically modifies all of the repeating units contained in the polymer chain, a part of the repeating units contained in the polymer chain, or the terminal portion of the polymer chain. The modifying group can be introduced into the polymer chain through substitution reactions, addition reactions, etc. The modifying group includes, for example, elements such as O, N, S, F, Cl, Br, F with relatively high electronegativity, and Si, Sn, P with relatively low electronegativity. By using a modifying group containing such elements, polarity can be imparted to the polymer. Examples of the modifying group include a carboxyl group, an acid anhydride group, an acyl group, a hydroxyl group, a sulfo group, a thioalkyl group, a phosphoric acid group, a phosphonic acid group, an isocyanate group, an epoxy group, a silyl group, an amino group, a nitrile group, a nitro group, etc. A specific example of the acid anhydride group is a maleic anhydride group. As the modifying group, it can be a functional group that can be introduced by reacting a modifier generated from the following compounds. Examples of the compound as the modifier include an epoxy compound, an ether compound, an ester compound, an isocyanate compound, an isothiocyanate compound, an isocyanuric acid derivative, a carbonyl compound containing an amino group, a vinyl compound containing an amino group, an epoxy compound containing an amino group, a mercapto derivative, a thiocarbonyl compound, a silicon halide compound, an epoxy silicon compound, a vinylated silicon compound, an alkoxysilane compound, an alkoxysilane compound containing an amino group, a tin halide compound, an organotin carboxylate compound, a phosphite compound, a phosphine compound, etc. In the second adhesive 113, when the styrenic elastomer contains the above-mentioned modifying group, the peel strength between the electrode layer 110 and the current collector 100 can be improved through the interaction with the current collector 100.

[0169] The styrenic elastomer may include a modifying group having a nitrogen atom. The so-called modifying group having a nitrogen atom is a nitrogen-containing functional group, and examples include an amino group such as an amine compound. The position of the modifying group can be at the polymer chain end. The styrenic elastomer can be, for example, a terminal amine-modified styrenic elastomer. The styrenic elastomer can be, for example, a styrenic elastomer having a nitrogen atom at at least one end of the polymer chain and having a star polymer structure centered on a nitrogen-containing alkoxysilane substituent.

[0170] The weight average molecular weight (M w)It can be 200,000 or more. The weight-average molecular weight of the styrenic elastomer can be 300,000 or more, can also be 500,000 or more, can also be 800,000 or more, and can also be 1,000,000 or more. The upper limit value of the weight-average molecular weight is, for example, 1,500,000. By the weight-average molecular weight of the styrenic elastomer being 200,000 or more, the particles of the solid electrolyte 111 and the active material 112 can be bonded with sufficient bonding strength. By the weight-average molecular weight of the styrenic elastomer being 1,500,000 or less, the ion conduction between the particles of the solid electrolyte 111 is not easily hindered by the second binder 113, and the output characteristics of the battery can be improved. The weight-average molecular weight of the styrenic elastomer can be determined, for example, by gel permeation chromatography (GPC) measurement using polystyrene as a standard sample. In other words, the weight-average molecular weight is a value converted using polystyrene. In GPC measurement, chloroform can be used as an eluent. When two or more peaks are observed in the graph obtained by GPC measurement, the weight-average molecular weight calculated from the entire peak range including each peak can be regarded as the weight-average molecular weight of the styrenic elastomer.

[0171] In the styrenic elastomer, the ratio of the degree of polymerization m of the repeating unit derived from styrene to the degree of polymerization n of the repeating unit other than styrene is defined as m:n. In this case, in the styrenic elastomer, the mole fraction (φ) of the repeating unit derived from styrene can be calculated using φ = m / (m + n). In the styrenic elastomer, the mole fraction (φ) of the repeating unit derived from styrene can be obtained, for example, by proton nuclear magnetic resonance ( 1 1H-NMR) measurement.

[0172] In the styrenic elastomer, the mole fraction (φ) of the repeating unit derived from styrene can be 0.02 or more and 0.55 or less, and can also be 0.1 or more and 0.3 or less. By the mole fraction (φ) of the styrenic elastomer being 0.02 or more, the strength of the electrode layer 110 can be improved. By the mole fraction (φ) of the styrenic elastomer being 0.55 or less, the flexibility of the electrode layer 110 can be improved.

[0173] The second binder 113 may contain a binder other than the styrenic elastomer. Or, the second binder 113 may be a styrenic elastomer. In other words, the second binder 113 may contain only the styrenic elastomer.

[0174] <Electrode layer>

[0175] The electrode layer 110 includes a second binder 113. The electrode layer 110 may further include a solid electrolyte 111, may include an active material 112, or may include both. According to this configuration, while maintaining sufficient strength of the electrode layer 110, the ionic conductivity inside the electrode layer 110 is increased, and the battery can operate at a high output.

[0176] The median diameter of the solid electrolyte 111 contained in the electrode layer 110 may be smaller than the median diameter of the active material 112. Thus, the solid electrolyte 111 and the active material 112 can be well dispersed.

[0177] In the electrode layer 110, for the volume ratio "v1:100 - v1" of the active material 112 and the solid electrolyte 111, 30 ≤ v1 ≤ 95 may be satisfied. v1 represents the volume ratio of the active material 112 when the total volume of the active material 112 and the solid electrolyte 111 contained in the electrode layer 110 is set to 100. When 30 ≤ v1 is satisfied, it is easy to ensure sufficient energy density for the battery. When v1 ≤ 95 is satisfied, the battery can operate more easily at a high output.

[0178] The thickness of the electrode layer 110 may be 10 μm or more and 500 μm or less. When the thickness of the electrode layer 110 is 10 μm or more, it is easy to ensure sufficient energy density for the battery. When the thickness of the electrode layer 110 is 500 μm or less, the battery can operate more easily at a high output.

[0179] In the electrode layer 110, the ratio of the second binder 113 to the solid electrolyte 111 may be 0.1 mass% or more and 10 mass% or less, may be 0.5 mass% or more and 8 mass% or less, or may be 1 mass% or more and 5 mass% or less. When the ratio of the second binder 113 to the solid electrolyte 111 is 0.1 mass% or more, there is a tendency to bond more particles of the solid electrolyte 111 using the second binder 113. Thus, the film strength of the electrode layer 110 can be increased. When the ratio of the second binder 113 to the solid electrolyte 111 is 10 mass% or less, in the electrode layer 110, there is a tendency to improve the contact between the particles of the solid electrolyte 111. Thus, the ionic conductivity of the electrode layer 110 can be increased.

[0180] In the electrode layer 110, the ratio of the second binder 113 to the active material 112 may be 0.03% by mass or more and 4% by mass or less, may be 0.15% by mass or more and 2% by mass or less, or may be 0.3% by mass or more and 1% by mass or less. When the ratio of the second binder 113 to the active material 112 is 0.03% by mass or more, there is a tendency to bond more particles of the active material 112 using the second binder 113. Thereby, the film strength of the electrode layer 110 can be improved. When the ratio of the second binder 113 to the active material 112 is 4% by mass or less, in the electrode layer 110, there is a tendency for the contact between the particles of the active material 112 to be improved. Thereby, the output characteristics of the battery can be improved.

[0181] For the purpose of improving electron conductivity, the electrode layer 110 may further contain a conductive aid. As the conductive aid, for example, graphite-based materials such as natural graphite and artificial graphite, carbon black-based materials such as acetylene black and Ketjen black, conductive fiber-based materials such as carbon fiber and metal fiber, conductive powder-based materials such as carbon fluoride and aluminum, conductive whisker-based materials such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene can be cited. If a carbon material is used as the conductive aid, cost reduction can be achieved.

[0182] For the purpose of improving the dispersibility of the solid electrolyte 111 and the active material 112, the electrode layer 110 may contain a dispersant. The dispersant may be a low molecular weight dispersant or a high molecular weight dispersant. As the dispersant, for example, commercially available dispersants, wetting agents, or surfactants can be used.

[0183] In the electrode layer 110, the dispersant may contain an amine compound. The amine compound is suitable for improving the dispersibility of the solid electrolyte 111. As the amine compound, for example, aliphatic amines such as methylamine and dimethylamine, aromatic amines such as aniline, and heterocyclic amines such as imidazole and imidazoline can be cited.

[0184] In the electrode layer 110, the dispersant may contain imidazoline or an imidazoline derivative. Imidazoline or an imidazoline derivative is more suitable for improving the dispersibility of the solid electrolyte 111. As the imidazoline derivative, for example, 1-hydroxyethyl-2-alkenyl imidazoline can be cited.

[0185] In the electrode layer 110, the ratio of the mass of the dispersant to the mass of the solid electrolyte 111 is not particularly limited. For example, it is 0.001% by mass or more and 10% by mass or less, and may also be 0.01% by mass or more and 1.0% by mass or less. When the ratio of the mass of the dispersant is 0.001% by mass or more, the dispersibility of the solid electrolyte 111 can be improved in the electrode layer 110. When the ratio of the mass of the dispersant is 10% by mass or less, a decrease in the ionic conductivity of the solid electrolyte 111 can be suppressed.

[0186] [Method for manufacturing electrode plate]

[0187] The electrode plate 1000 can be manufactured, for example, by the following method. First, an electrode composition containing a solid electrolyte 111, an active material 112, and a second binder 113 for forming the electrode layer 110 is prepared. As the electrode composition, a slurry in which the solid electrolyte 111, the active material 112, and the second binder 113 are dispersed in a solvent can be used. As the solvent, a solvent that does not react with the solid electrolyte 111, such as an aromatic hydrocarbon-based solvent like tetralin, can be used. Next, the electrode composition is coated on the coating layer 102 of the current collector 100. As the method for coating the electrode composition, an extrusion coating method, a gravure coating method, a doctor blade method, a rod coating method, a spraying method, an electrostatic coating method, etc. can be cited. By drying the obtained coating film, the electrode layer 110 is formed, and the electrode plate 1000 can be obtained. The drying method of the coating film is not particularly limited. For example, the coating film can be dried by heating the coating film at a set temperature of 80°C or higher and 150°C or lower using warm air / hot air drying. It should be noted that the method of coating the electrode composition on the coating layer 102 to form the electrode layer 110 is sometimes called a wet coating method.

[0188] (Embodiment 3)

[0189] Figure 3 FIG. is a cross-sectional view of the battery 2000 according to Embodiment 3. The battery 2000 includes a negative electrode 201, a positive electrode 203, and an electrolyte layer 202.

[0190] At least one selected from the negative electrode 201 and the positive electrode 203 includes the electrode plate 1000 in Embodiment 2. That is, at least one selected from the negative electrode 201 and the positive electrode 203 has an electrode layer 110 and a current collector 100.

[0191] The electrolyte layer 202 is located between the negative electrode 201 and the positive electrode 203.

[0192] According to the above configuration, the battery 2000 of Embodiment 3 can improve the output characteristics.

[0193] As Figure 3 shown, in the battery 2000, the negative electrode 201 can be the electrode plate 1000 in Embodiment 2. In this case, the negative electrode 201 has the electrode layer 110 and the current collector 100 described in Embodiment 2. Hereinafter, the battery 2000 in which the negative electrode 201 is the electrode plate 1000 will be described. However, the battery 2000 is not limited to the following manner. In the battery 2000, the positive electrode 203 can be the electrode plate 1000 in the above Embodiment 2.

[0194] According to the above configuration, the output characteristics of the battery 2000 can be further improved.

[0195] The electrolyte layer 202 is a layer containing an electrolyte material. As the electrolyte material, for example, a solid electrolyte can be cited. That is, the electrolyte layer 202 can be a solid electrolyte layer. As the solid electrolyte contained in the electrolyte layer 202, the solid electrolytes exemplified as the solid electrolyte 111 can be used. For example, a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, a polymer solid electrolyte, a complex hydride solid electrolyte, etc. can be used.

[0196] The electrolyte layer 202 may contain a solid electrolyte as a main component. The electrolyte layer 202 may contain a solid electrolyte in a mass ratio of 70% or more (70 mass% or more) with respect to the whole of the electrolyte layer 202.

[0197] According to the above configuration, the charge-discharge characteristics of the battery 2000 can be improved.

[0198] The electrolyte layer 202 contains a solid electrolyte as a main component and may further contain inevitable impurities, or starting materials, by-products, and decomposition products used in synthesizing the solid electrolyte.

[0199] The electrolyte layer 202 may contain a solid electrolyte in a mass ratio of 100% (100 mass%) with respect to the whole of the electrolyte layer 202 except for inevitably mixed-in impurities.

[0200] According to the above configuration, the charge-discharge characteristics of the battery 2000 can be further improved.

[0201] The electrolyte layer 202 may contain two or more of the materials listed as solid electrolytes. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0202] The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 202 is 1 μm or more, the possibility of short circuit between the negative electrode 201 and the positive electrode 203 is reduced. When the thickness of the electrolyte layer 202 is 300 μm or less, the battery 2000 can easily operate at high output. That is, if the thickness of the electrolyte layer 202 is appropriately adjusted, the safety of the battery 2000 can be sufficiently ensured, and the battery 2000 can operate at high output.

[0203] There is no particular limitation on the shape of the solid electrolyte contained in the battery 2000. The shape of the solid electrolyte can be needle-like, spherical, ellipsoidal, etc. The shape of the solid electrolyte can be particulate.

[0204] The positive electrode 203 may include an electrolyte material, for example, a solid electrolyte may be included. As the solid electrolyte, the solid electrolytes exemplified as the materials constituting the electrolyte layer 202 may be used. According to the above configuration, the ionic conductivity (e.g., lithium ion conductivity) inside the positive electrode 203 is improved, and the battery 2000 can operate at high output.

[0205] The positive electrode 203 includes, for example, a material having the property of storing and releasing metal ions (e.g., lithium ions) as a positive electrode active material. As the positive electrode active material, the materials exemplified in Embodiment 2 may be used.

[0206] The median diameter of the positive electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the positive electrode active material is 0.1 μm or more, in the positive electrode 203, the positive electrode active material and the solid electrolyte can be well dispersed. Thereby, the charge-discharge characteristics of the battery 2000 are improved. When the median diameter of the positive electrode active material is 100 μm or less, the lithium diffusion rate inside the positive electrode active material is increased. Therefore, the battery 2000 can operate at high output.

[0207] The median diameter of the positive electrode active material may be larger than the median diameter of the solid electrolyte. Thereby, the solid electrolyte and the positive electrode active material can be well dispersed.

[0208] In the positive electrode 203, for the volume ratio "v2: 100 - v2" of the positive electrode active material and the solid electrolyte, 30 ≤ v2 ≤ 95 may be satisfied. v2 represents the volume ratio of the positive electrode active material when the total volume of the positive electrode active material and the solid electrolyte contained in the positive electrode 203 is set to 100. When 30 ≤ v2 is satisfied, it is easy to ensure sufficient energy density for the battery 2000. When v2 ≤ 95 is satisfied, it is easier for the battery 2000 to operate at high output.

[0209] The thickness of the positive electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 203 is 10 μm or more, it is easy to ensure sufficient energy density for the battery 2000. When the thickness of the positive electrode 203 is 500 μm or less, it is easier for the battery 2000 to operate at high output.

[0210] In order to reduce the interface resistance with the solid electrolyte, the positive electrode active material may be coated with a coating material. As the coating material, a material with low electronic conductivity may be used. As the coating material, an oxide material, an oxide solid electrolyte, etc. may be used. As the coating material, the materials exemplified in Embodiment 2 may be used.

[0211] For the purpose of improving the adhesion between particles, at least one selected from the electrolyte layer 202 and the positive electrode 203 may contain a binder. As the binder, the materials exemplified in Embodiment 2 can be used. One binder can be used alone, or two or more binders can be used in combination.

[0212] As the binder, from the viewpoint of excellent adhesiveness, an elastomer can be used. An elastomer refers to a polymer having elasticity. The elastomer used as the binder can be a thermoplastic elastomer or a thermosetting elastomer. The binder may contain a thermoplastic elastomer. As the elastomer, the materials exemplified in Embodiment 2 can be used. When the binder contains an elastomer, for example, high filling can be achieved for the electrolyte layer 202 or the positive electrode 203 by thermal compression during the manufacture of the battery 2000.

[0213] For the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery 2000, at least one selected from the electrode layer 110 of the negative electrode 201, the electrolyte layer 202, and the positive electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid.

[0214] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, a cyclic carbonate solvent, a chain carbonate solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, a fluorine solvent, etc. can be used. As the cyclic carbonate solvent, ethylene carbonate, propylene carbonate, butylene carbonate, etc. can be cited. As the chain carbonate solvent, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc. can be cited. As the cyclic ether solvent, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, etc. can be cited. As the chain ether solvent, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc. can be cited. As the cyclic ester solvent, γ-butyrolactone, etc. can be cited. As the chain ester solvent, methyl acetate, etc. can be cited. As the fluorine solvent, fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoromethyl ethyl carbonate, difluoromethyl carbonate, etc. can be cited. As the non-aqueous solvent, one non-aqueous solvent selected from the above can be used alone, or a mixture of two or more non-aqueous solvents selected from the above can be used.

[0215] In the non-aqueous electrolyte, at least one fluorine solvent selected from fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoromethyl ethyl carbonate, and difluoromethyl carbonate may be contained.

[0216] As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)

[0217] (SO2C4F9), LiC(SO2CF3)3, etc. As the lithium salt, one lithium salt selected from the above can be used alone, or a mixture of two or more lithium salts selected from the above can be used. The concentration of the lithium salt in the non-aqueous electrolyte can be 0.5 mol / L or more and 2 mol / L or less.

[0218] As the gel electrolyte, a material containing a non-aqueous electrolyte in a polymer material can be used. Examples of the polymer material include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a polymer having an ethylene oxide bond, and the like.

[0219] The cation constituting the ionic liquid can be an aliphatic chain-like quaternary cation such as tetraalkylammonium and tetraalkylphosphonium, an aliphatic cyclic ammonium such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium, and piperidinium, a nitrogen-containing heterocyclic aromatic cation such as pyridinium and imidazolium, etc. The anion constituting the ionic liquid can be PF6 - 、BF4 - 、SbF6 - 、AsF6 - 、SO3CF3 - 、N(SO2F)2 - 、N(SO2CF3)2 - 、N(SO2C2F5)2 - 、N(SO2CF3)(SO2C4F9) - 、C(SO2CF3)3 - etc. The ionic liquid can contain a lithium salt.

[0220] For the purpose of improving the electronic conductivity, at least one of the electrode layer 110 of the negative electrode 201 and the positive electrode 203 can contain a conductive assistant. As the conductive assistant, the materials exemplified in Embodiment 2 can be used.

[0221] For the purpose of improving the dispersibility of the solid electrolyte and the active material, at least one of the electrode layer 110 of the negative electrode 201 and the positive electrode 203 can contain a dispersant. As the dispersant, the materials exemplified in Embodiment 2 can be used.

[0222] Examples of the shape of the battery 2000 include coin type, cylindrical type, square type, sheet type, button type, flat type, laminated type, etc.

[0223] The battery 2000 can be manufactured, for example, by the following method. First, a current collector 100, a material for forming the electrode layer 110, a material for forming the electrolyte layer 202, a material for forming the positive electrode 203, and a current collector for the positive electrode 203 are respectively prepared. Using them, a laminate in which the negative electrode 201, the electrolyte layer 202, and the positive electrode 203 are sequentially arranged is produced by a known method. Thereby, the battery 2000 can be manufactured.

[0224] Figure 4 FIG. is a cross-sectional view of the battery 2001 according to the modification. The battery 2001 can be a laminate of a plurality of batteries 2000. The battery 2001 can be manufactured by the following method. A negative electrode (first negative electrode 211) in which the electrode layer 110 is laminated on the current collector 100 having the coating layer 102 disposed on both surfaces of the substrate 101, the first electrolyte layer 212, and the first positive electrode 213 are sequentially arranged. On the other hand, an electrode layer 110 (second negative electrode 221), a second electrolyte layer 222, and a second positive electrode 223 are sequentially arranged on the surface of the current collector 100 on the opposite side of the surface on which the first negative electrode 211 is laminated. Thereby, a laminate in which the first positive electrode 213, the first electrolyte layer 212, the first negative electrode 211, the current collector 100, the second negative electrode 221, the second electrolyte layer 222, and the second positive electrode 223 are sequentially arranged is obtained. The battery 2001 can be manufactured by pressure molding of this laminate using a press at a high temperature, for example, at a temperature of 120 ° C or higher and 195 ° C or lower. According to such a method, a laminate of two batteries 2000 can be produced while suppressing warping of the battery, and a high-output battery 2001 can be manufactured with higher efficiency. It should be noted that in the production of the battery 2001, there is no particular limitation on the order in which the respective members are laminated. For example, after the first negative electrode 211 and the second negative electrode 221 are disposed on the current collector 100, the first electrolyte layer 212, the second electrolyte layer 222, the first positive electrode 213, and the second positive electrode 223 are sequentially laminated, whereby a laminate of two batteries 2000 can be produced. Further, by separately preparing a plurality of batteries 2001 and a current collector for the positive electrode and alternately laminating the battery 2001 and the positive electrode current collector, a laminate of the battery 2000 can be manufactured. By using such a method, the battery 2000 can be laminated with high efficiency.

[0225] (Other embodiments)

[0226] (Supplementary note)

[0227] Based on the description of the above embodiments, the following technology is disclosed.

[0228] (Technology 1)

[0229] A current collector, which is a current collector having a substrate and a coating layer that coats the substrate, the coating layer containing conductive carbon and a first binder, the first binder containing an aromatic super engineering plastic, and the water content of the current collector calculated based on the water generated from the current collector when heated at 200°C being 200 mass ppm or less.

[0230] According to such a configuration, it is possible to balance the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device.

[0231] (Technology 2)

[0232] The current collector according to Technology 1, wherein the tensile strength of the current collector is 120 N / mm 2 or more. According to such a configuration, even if the member including the current collector is compressed at a high temperature, breakage of the current collector is suppressed, and the productivity of the electrochemical device can be further improved.

[0233] (Technology 3)

[0234] The current collector according to Technology 1 or 2, wherein the aromatic super engineering plastic includes at least one selected from polyimide and polyethersulfone. Polyimide and polyethersulfone tend to exhibit higher heat resistance. Therefore, if at least one selected from polyimide and polyethersulfone is used, the effect of suppressing adhesion of the coating layer to the production equipment is improved.

[0235] (Technology 4)

[0236] The current collector according to Technology 3, wherein the imidization rate of the polyimide is 90% or more. According to such a configuration, the water content of the current collector can be reduced.

[0237] (Technology 5)

[0238] The current collector according to any one of Technologies 1 to 4, wherein the substrate includes aluminum or an aluminum alloy. According to such a configuration, not only can the peel strength between the electrode layer and the current collector be improved, but also the mass energy density of the electrochemical device can be improved.

[0239] (Technology 6)

[0240] The current collector according to any one of Technologies 1 to 5, wherein the water content is 100 mass ppm or less. According to such a configuration, it is easy to balance the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device.

[0241] (Technology 7)

[0242] An electrode plate, comprising: the current collector according to any one of Technologies 1 to 6; and an electrode layer containing a second binder and disposed on the current collector.

[0243] According to such a configuration, it is possible to balance the productivity of the electrochemical device and the high-temperature characteristics of the electrochemical device.

[0244] (Technique 8)

[0245] The electrode plate according to Technique 7, wherein the second binder contains a styrene-based elastomer. The styrene-based elastomer is excellent in flexibility and elasticity, and thus is suitable as a binder for the electrode layer. In addition, the peel strength between the electrode layer and the current collector can be improved.

[0246] (Technique 9)

[0247] The electrode plate according to Technique 7 or 8, wherein the electrode layer further contains a solid electrolyte. The electrode plate of the present disclosure is suitable for an electrochemical device, particularly a battery, in which the electrode layer contains a solid electrolyte.

[0248] (Technique 10)

[0249] The electrode plate according to Technique 9, wherein the solid electrolyte contains a sulfide solid electrolyte. The sulfide solid electrolyte is particularly suitable as the solid electrolyte of the electrode layer because of its more excellent ionic conductivity and formability.

[0250] (Technique 11)

[0251] A battery comprising: a positive electrode, a negative electrode, and an electrolyte layer located between the positive electrode and the negative electrode, wherein at least one selected from the positive electrode and the negative electrode contains the electrode plate according to any one of Techniques 7 to 10.

[0252] According to such a configuration, it is possible to provide a battery that balances productivity and high-temperature cycle characteristics. The output characteristics of such a battery are also excellent.

[0253] Examples

[0254] Hereinafter, the details of the present disclosure will be described using examples and comparative examples. It should be noted that the current collector, electrode plate, and battery of the present disclosure are not limited to the following examples.

[0255] <Example 1-1>

[0256] [Fabrication of Current Collector]

[0257] A coating was prepared by kneading conductive carbon, a first binder, and a solvent. As the conductive carbon, carbon black and graphite were used. As the first binder, soluble polyimide (PI) was used. Next, the coating was applied to one side of an aluminum alloy foil (A3003 foil, thickness: 15 μm) to form a coating film. The coating film was dried at 165 °C to form a coating layer. Further, the coating was applied to the other side of the aluminum alloy foil to form a coating film. The coating film was dried at 165 °C to form a coating layer. Thus, a current collector having coating layers on both sides was fabricated. The mass per unit area of each coating layer was 1.3 g / m 2 ². Then, the moisture content of the current collector was adjusted by leaving the current collector standing in an argon glove box with a dew point of -60 °C or lower for more than one week. Thus, the current collector of Example 1-1 was obtained.

[0258] <Example 1-2>

[0259] A current collector of Example 1-2 was fabricated in the same manner as in Example 1-1, except that polyether sulfone (PES) was used as the first binder. In the current collector of Example 1-2, the mass per unit area of each coating layer was 1.3 g / m 2 ².

[0260] <Comparative Example 1-1>

[0261] A current collector of Comparative Example 1-1 was fabricated in the same manner as in Example 1-1, except that polyvinylidene fluoride (PVDF) was used as the first binder. In the current collector of Comparative Example 1-1, the mass per unit area of each coating layer was 0.94 g / m 2 ².

[0262] <Comparative Example 1-2>

[0263] A current collector of Comparative Example 1-2 was fabricated in the same manner as in Example 1-1, except that a polyimide varnish was used as the first binder. In the current collector of Comparative Example 1-2, the mass per unit area of each coating layer was 0.64 g / m 2 ². The polyimide varnish is a polyamic acid solution, which is a precursor of polyimide. In Comparative Example 1-2, when the coating was applied to the aluminum alloy foil and heated, an imidization reaction occurred.

[0264] [Measurement of moisture content by the Karl Fischer method]

[0265] For the current collectors of the examples and comparative examples, the moisture content was measured by the Karl Fischer method using the following method.

[0266] For the measurement of the moisture content, the following method was implemented using a moisture vaporization device (manufactured by Nitto Seiko Analysis Co., Ltd., VA-300) and a moisture measurement device (manufactured by Nitto Seiko Analysis Co., Ltd., CA-310) installed in a drying chamber with a dew point below -40°C. Under a nitrogen gas flow of 250 ml / min, the moisture content of the current collector cut into 120 mm × 150 mm at 100°C was measured based on the coulometric titration method. Next, the temperature of the current collector was increased, and the moisture content at each temperature of 125°C, 150°C, 175°C, 200°C, 225°C, 250°C, 275°C, and 300°C was measured. The cumulative moisture content (μg) up to 200°C and the cumulative moisture content (μg) up to 300°C were determined, and the ratio of each to the mass (g) of the current collector (μg / g = mass ppm) was calculated as the moisture content (rate).

[0267] [Measurement of Tensile Strength]

[0268] For the current collectors of the examples and comparative examples, the tensile strength was measured by the following method.

[0269] For the measurement of the tensile strength, at atmospheric pressure and room temperature, using a load-displacement measurement unit (manufactured by IMADA Co., Ltd., FSA-0.5K-500N), the following method was implemented. The load (unit: N) when the current collector cut into a width of 10 mm was stretched at a speed of 20 mm / min was continuously recorded until the current collector broke, and the maximum load was determined. The value obtained by dividing the maximum load by the cross-sectional area of the current collector (mm 2 ) was regarded as the tensile strength of the current collector (unit: N / mm 2 ).

[0270] [Evaluation of Productivity]

[0271] For the examples and comparative examples, the following method was used to simulate the compression process at high temperature during battery manufacturing, and the productivity of the battery was evaluated.

[0272] The following operation was carried out in an argon glove box with a dew point below -60°C. The current collector cut into 90 mm × 150 mm was clamped with two 10-μm-thick SUS foils to obtain a test piece. Using a roll press heated to 180°C, the test piece was pressed under the conditions of an in-line pressure of 3.6 t / cm and a speed of 0.2 m / min. By visual inspection, it was confirmed whether the current collector after high-temperature pressing was adhered to the SUS foil. In Table 1, a circle (〇) indicates no adhesion and good productivity. A cross (×) indicates adhesion and poor productivity.

[0273] [Evaluation of High-Temperature Cycling Characteristics]

[0274] Using the current collectors of the examples and comparative examples, batteries were fabricated, and the high-temperature cycling characteristics were evaluated.

[0275] [Manufacture of Battery]

[0276] In a drying chamber with a dew point of -50°C or lower, using a slot die coater, a negative electrode active material layer composed of Li4Ti5O 12 (LTO), Li2S-P2S5-based glass-ceramic (LPS), solution-polymerized styrene-butadiene rubber (modified SBR, manufactured by Asahi Kasei Corporation, Asaprene Y031), a dispersant (1-hydroxyethyl-2-vinylimidazoline, manufactured by BYK Corporation, DISPERBYK-109), and vapor-grown carbon fiber (manufactured by Showa Denko KK, VGCF-H) was formed on a nickel foil (15 μm thick). Next, an electrolyte layer composed of LPS, modified SBR, and a dispersant was formed on the negative electrode. Next, a positive electrode active material layer composed of lithium nickel cobalt aluminate (NCA) coated with LiNbO3, LPS, modified SBR, vapor-grown carbon fiber, acetylene black (manufactured by DENKA Company Limited, DENKABLACK Li, Li-435), and a dispersant was formed on the electrolyte layer. Thus, a laminate including a nickel foil (negative electrode current collector), a negative electrode active material layer, an electrolyte layer, and a positive electrode active material layer in this order was manufactured.

[0277] In an argon glove box with a dew point of -60°C or lower, the laminate was cut into a size of 20 mm × 20 mm square. Next, the laminate, the current collector of the example or comparative example (positive electrode current collector), and a silicone rubber film were laminated in a mold in this order to manufacture an electrode plate. The electrode plate was compression-molded at a pressure of 580 MPa at 160°C. The silicone rubber film was removed, and the peripheral ends of the electrode plate were cut off using a shearing machine. Copper foils with tabs were attached to the negative electrode current collector and the positive electrode current collector, respectively. The battery was manufactured by vacuum-sealing the electrode plate in a container formed of an aluminum laminated film.

[0278] [Charge and Discharge Test]

[0279] The metal plates, battery, silicone rubber sheet, and metal plate were clamped in sequence, and 1 bolt was tightened with a torque of 2 N·m, thereby binding the battery with a pressure of approximately 1 MPa and disposing it in a constant temperature bath at 25°C. Next, it was charged at a constant current with a current value of 0.1 C rate relative to the actual capacity of the positive electrode active material (lithium nickel cobalt aluminate) until the voltage reached 2.7 V. Then, it was charged at a constant voltage of 2.7 V and the charging was ended with a current value of 0.01 C rate. Then, it was discharged at a constant current of 0.1 C rate until the voltage reached 1.5 V and then discharged at a constant voltage of 1.5 V until 0.01 C rate. Next, it was charged at a constant current of 0.333 C rate until the voltage reached 2.7 V and then charged at a constant current of 0.01 C rate until the voltage reached 2.7 V. Next, it was discharged at a constant current of 0.333 C rate until the voltage reached 1.5 V and then discharged at a constant current of 0.01 C rate until the voltage reached 1.5 V. Then, the temperature of the constant temperature bath was changed to 80°C and a high-temperature cycle test was carried out under the following conditions. First, it was charged at a constant current of 5 C rate until the voltage reached 2.7 V and then charged at a constant voltage of 2.7 V until 0.33 C rate. Next, it was discharged at a constant current of 1 C rate until the voltage reached 1.82 V. The discharge capacity measured at this time was regarded as the initial discharge capacity. The above charge and discharge at high temperature were repeated 20 times. The ratio of the 20th discharge capacity to the initial discharge capacity was regarded as the discharge capacity retention rate. The results are shown in Table 1.

[0280] Table 1

[0281]

[0282] As shown in Table 1, although the battery using the current collector of Comparative Example 1-1 exhibited a high discharge capacity retention rate, since polyvinylidene fluoride was used as the first binder for the coating layer, it adhered to the SUS foil when pressed at high temperature.

[0283] Since polyimide was used as the first binder for the coating layer in the current collector of Comparative Example 1-2, it did not adhere to the SUS foil when pressed at high temperature. However, in Comparative Example 1-2, since polyimide from polyimide varnish was used as the first binder, the amount of moisture measured when heated at 200°C greatly exceeded 200 mass ppm. As a result, the battery using the current collector of Comparative Example 1-2 showed a low discharge capacity retention rate.

[0284] The current collectors of Example 1-1 and Example 1-2 contain an aromatic super engineering plastic as the first binder of the coating layer, and the moisture content measured at 200 °C is 200 mass ppm or less. The current collectors of Example 1-1 and Example 1-2 do not bond to the SUS foil even when pressed at high temperatures, showing good productivity. The discharge capacity retention rate of the battery using the current collectors of Example 1-1 and Example 1-2 is superior to that of the battery using the current collector of Comparative Example 1-2. That is, according to Example 1-1 and Example 1-2, a current collector with improved productivity and high-temperature cycle characteristics was obtained.

[0285] [Measurement of imidization rate]

[0286] Using the method described previously, the imidization rate of the polyimide contained in the coating layer of the current collectors of Example 1-1 and Comparative Example 1-2 was measured. As a result, the imidization rate of the polyimide contained in the coating layer of the current collector of Example 1-1 was 100%. The imidization rate of the polyimide contained in the coating layer of the current collector of Comparative Example 1-2 was 82%. It should be noted that a reference sample completely imidized was prepared by heat-treating the current collector in a vacuum atmosphere at 350 °C for 6 hours.

[0287] <Example 2-1>

[0288] [Fabrication of electrode plate]

[0289] In an argon glove box with a dew point of -60 °C or lower, 250 g of LTO was weighed, 136 g of tetralin and 15.0 g of a dispersant solution containing a dispersant at a concentration of 5 mass% were added to prepare a mixed solution. As the dispersant, 1-hydroxyethyl-2-vinylimidazoline was used. As the solvent of the dispersant solution, tetralin was used. For this mixed solution, a bench-top digital ultrasonic homogenizer (manufactured by BRANSON, SONIFIER SFX550) was used to perform dispersion and kneading. Then, 43.4 g of a second binder solution containing a second binder at a concentration of 5 mass%, 2.75 g of vapor-grown carbon fiber (manufactured by Showa Denko K.K., VGCF-H), and 84.0 g of LPS were added to the mixed solution, and dispersion and kneading were performed to prepare a slurry. As the second binder, a mixture containing a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec MP10) and a hydrogenated block copolymer (SEBS, manufactured by KRATON Corporation, G1633) in a mass ratio of 1:1 was used. As the solvent of the second binder solution, tetralin was used. "Tuftec" is a registered trademark of Asahi Kasei Corporation. Next, the slurry was coated on the current collector of Example 1-1, and the obtained coating film was dried in a vacuum atmosphere at 100 °C for 1 hour to fabricate the electrode plate of Example 2-1.

[0290] [Measurement of peel strength]

[0291] The peel strength between the electrode layer of the electrode plate in Example 2-1 and the current collector was measured using a universal material testing machine (manufactured by A&D Company, RTH-1310) in a drying chamber with a dew point of -50°C or lower by the following method. First, the electrode plate cut to a width of 15 mm was bonded to the test plate with double-sided tape. Specifically, the electrode layer of the electrode plate was attached to the test plate via the double-sided tape. Second, using a testing machine equipped with a jig for a 90° peel test with an adhesive tape, the electrode layer was peeled from the current collector at a peel angle of 90° and a peel speed of 5 mm / min. Then, after the start of the measurement, the measured value of the initial 5 mm length peeled from the current collector was not used, and then, the measured values (unit: N) continuously recorded for the electrode layer of the 5 mm length peeled from the current collector were recorded. The average value (Av) obtained by dividing the measured value by the width of the electrode plate was regarded as the peel strength between the electrode layer and the current collector in the electrode plate (unit: N / m).

[0292] [Fabrication of battery]

[0293] In an argon glove box with a dew point of -60°C or lower, the positive electrode and the solid electrolyte sheet were each punched into a size of 20 mm × 20 mm. The positive electrode had a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer included a positive electrode active material layer composed of NCA coated with LiNbO3, LPS, modified SBR, vapor-grown carbon fiber, acetylene black, and a dispersant. As the positive electrode current collector, carbon-coated aluminum foil (manufactured by Showa Denko K.K., SDX (registered trademark)) was used. The solid electrolyte sheet had a solid electrolyte layer disposed on a polyimide substrate. The electrolyte layer included LPS, modified SBR, and a dispersant.

[0294] Next, the positive electrode, the solid electrolyte sheet, and the silicone rubber film were sequentially laminated in a mold to fabricate a laminate. The laminate was pressurized at 80°C and 40 MPa to transfer the solid electrolyte layer onto the positive electrode, thereby fabricating a laminate of the positive electrode and the solid electrolyte layer. After removing the polyimide substrate and the silicone rubber film from the laminate, the electrode plate of Example 2-1 as the negative electrode, the solid electrolyte layer, the positive electrode, and the silicone rubber film were sequentially laminated in a mold to fabricate a power generation element. The power generation element was compression-molded at 160°C and 580 MPa. The silicone rubber film was removed, and the peripheral ends of the power generation element were cut off using a guillotine. Copper foils with tabs were pasted on the negative electrode current collector and the positive electrode current collector respectively. The power generation element was vacuum-sealed in a container formed of an aluminum laminated film to fabricate the battery of Example 2-1.

[0295] [Charge and discharge test]

[0296] Except that the temperature of the high-temperature cycle test was set at 60°C and the charge-discharge cycle was repeated 90 times, the charge-discharge test was carried out in the same manner as in Example 1-1, and the discharge capacity retention rate of the battery of Example 2-1 was measured. The ratio of the 90th discharge capacity to the initial discharge capacity was regarded as the discharge capacity retention rate.

[0297] <Example 2-2>

[0298] Except that an acrylic resin (PMMA, manufactured by Sigma-Aldrich, weight-average molecular weight 15,000) was used as the second binder, the electrode plate and the battery were fabricated in the same manner as in Example 2-1. In addition, the peel strength of the electrode plate and the discharge capacity retention rate of the battery were measured.

[0299] <Comparative Example 2-1>

[0300] Except that the current collector of Comparative Example 1-2 was used, the electrode plate and the battery were fabricated in the same manner as in Example 2-1. In addition, the peel strength of the electrode plate and the discharge capacity retention rate of the battery were measured.

[0301] <Comparative Example 2-2>

[0302] Except that the current collector of Comparative Example 1-2 was used, the electrode plate and the battery were fabricated in the same manner as in Example 2-2. In addition, the peel strength of the electrode plate and the discharge capacity retention rate of the battery were measured.

[0303] The above results are shown in Table 2.

[0304] Table 2

[0305]

[0306] In the current collector of Comparative Example 1-2 used in Comparative Example 2-1 and Comparative Example 2-2, the imidization rate of the polyimide used as the first binder for the coating layer was less than 90%, and the water content of the current collector measured at 200°C greatly exceeded 200 mass ppm. As a result, the batteries of Comparative Example 2-1 and Comparative Example 2-2 showed a low discharge capacity retention rate.

[0307] In the current collector of Example 1-1 used in Example 2-1 and Example 2-2, the imidization rate of the polyimide used as the first binder for the coating layer was 90% or more, and the water content of the current collector measured at 200°C was 200 mass ppm or less. As a result, the batteries of Example 2-1 and Example 2-2 showed a high discharge capacity retention rate.

[0308] As shown in Table 2, in Example 2-2, an electrode plate using PMMA as the second binder contained in the electrode layer was used. However, since the peel strength was very weak, peeling occurred during the installation of the jig before the peel test measurement, and the measurement could not be performed. On the other hand, in Example 2-1, in the case of using an electrode plate using a styrene-based elastomer (a mixture of modified SEBS and SEBS) as the second binder contained in the electrode layer, a high peel strength of 0.5 N / m or more was exhibited.

[0309] Industrial Applicability

[0310] The current collector of the present disclosure can be used in electrochemical devices such as batteries and capacitors.

Claims

1. A current collector, which is a current collector having a substrate and a coating layer covering the substrate, the coating layer containing conductive carbon and a first binder, the first binder containing an aromatic super engineering plastic, and the water content of the current collector calculated based on the water generated from the current collector when heated at 200°C being 200 mass ppm or less.

2. The current collector according to claim 1, wherein, The tensile strength of the current collector is 120 N / mm 2 or more.

3. The current collector according to claim 1, wherein, The aromatic super engineering plastic contains at least one selected from polyimide and polyethersulfone.

4. The current collector according to claim 3, wherein, The imidization rate of the polyimide is 90% or more.

5. The current collector according to claim 1, wherein, The substrate contains aluminum or an aluminum alloy.

6. The current collector according to claim 1, wherein The water content is 100 mass ppm or less.

7. An electrode plate, which comprises: the current collector according to claim 1; and an electrode layer containing a second binder and disposed on the current collector.

8. The electrode plate according to claim 7, wherein, The second binder contains a styrene-based elastomer.

9. The electrode plate according to claim 7, wherein The electrode layer further contains a solid electrolyte.

10. The electrode plate according to claim 9, wherein, The solid electrolyte contains a sulfide solid electrolyte.

11. A battery, which comprises: a positive electrode, a negative electrode, and an electrolyte layer located between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode contains the electrode plate according to claim 7.

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