Composite substrate for rechargeable lithium battery, method for preparing same, and rechargeable lithium battery including same

Abstract

Disclosed examples include a composite substrate for a rechargeable lithium battery, a method of preparing the composite substrate, and a rechargeable lithium battery including the composite substrate, the composite substrate including: a support layer including a polymer film; and a metal layer disposed on the support layer and including at least one of copper and a copper oxide. The metal layer includes: a first metal layer on a surface of the support layer and including an adhesion enhancer and first copper; and a second metal layer on the first metal layer and including second copper. The adhesion enhancer includes: a first portion chemically bonded to a surface of the support layer and including a hydroxyalkylene group; and a second portion comprising an amine group configured to adsorb the first copper.

Description

[0001] This patent application claims priority to Korean Patent Application No. 10-2024-0124611, filed on September 12, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates herein to a composite substrate for a rechargeable lithium battery and a rechargeable lithium battery including the composite substrate. Background Technology

[0003] The increasing use of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles) has driven a sharp rise in demand for rechargeable batteries with high energy density and high capacity. Therefore, improving the performance of rechargeable lithium batteries may be beneficial.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode, each containing active material that allows lithium ions to be inserted into and extracted, and an electrolyte solution, and generates electrical energy from redox reactions that occur when lithium ions are inserted into or extracted from the positive and negative electrodes. Summary of the Invention

[0005] Examples of this disclosure include composite substrates for rechargeable lithium batteries that exhibit improved adhesive strength between a metal layer and a support layer comprising a polymer film.

[0006] Examples of this disclosure also include rechargeable lithium batteries incorporating the composite substrate that exhibit desired or improved stability.

[0007] Example embodiments of the present invention include a composite substrate for a rechargeable lithium-ion battery, the composite substrate comprising: a support layer comprising a polymer film; and a metal layer on the support layer, comprising at least one of copper, copper oxide, and combinations thereof. The metal layer comprises: a first metal layer on the surface of the support layer and comprising an adhesion enhancer and a first copper; and a second metal layer on the first metal layer and comprising a second copper. The adhesion enhancer comprises: a first portion chemically bonded to the surface of the support layer and comprising a hydroxyalkylene group; and a second portion comprising an amine group configured to adsorb the first copper.

[0008] In an exemplary embodiment of the present invention, a method for preparing a composite substrate for a rechargeable lithium battery includes: modifying the surface of a support layer; forming a first metal layer comprising a first copper on the modified surface of the support layer; and forming a second metal layer comprising a second copper on the first metal layer. Forming the first metal layer includes: bonding a first compound comprising a glycidyl group to the modified surface of the support layer; bonding a second compound comprising an amino group to one end of the first compound to form an adhesion enhancer; impregnating the support layer with a first solution comprising first copper ions; and impregnating the support layer with a second solution comprising a reducing agent to reduce the first copper ions.

[0009] In an exemplary embodiment of the present invention, a rechargeable lithium battery includes a composite substrate for a rechargeable lithium battery and a battery cell on the composite substrate, wherein the battery cell includes a first active material layer on a metal layer, a separator on the first active material layer, a second active material layer on the separator, and a metal substrate on the second active material layer. Attached Figure Description

[0010] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present invention; Figures 2 to 5 Each of these is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment; Figure 6 This is a cross-sectional view illustrating a rechargeable lithium battery including a composite substrate according to an exemplary embodiment of the present invention; Figure 7 It is shown Figure 6 A cross-sectional view of the composite substrate; Figure 8 It is Figure 7 The enlarged image of M; Figure 9 This is a cross-sectional view illustrating surface modification of the support layer according to an exemplary embodiment of the present invention; Figure 10 It is Figure 9 The magnified image of N; Figure 11 This is a conceptual diagram illustrating the bonding of a first compound to the surface of a support layer according to an exemplary embodiment of the present invention; Figure 12 This is a conceptual diagram illustrating the adhesion enhancer bonded to the surface of the support layer according to an exemplary embodiment of the present invention; Figure 13This is a conceptual diagram illustrating the process of forming a first metal layer and a second metal layer according to an exemplary embodiment of the present invention; Figure 14 It is Figure 13 The enlarged image of O; Figure 15 This is a conceptual diagram illustrating the interaction between an adhesion enhancer and copper ions according to an exemplary embodiment of the present invention; Figure 16 It is Figure 13 The enlarged image of P; Figure 17 It is Figure 13 The enlarged image of Q; and Figure 18 This is a flowchart illustrating a method for preparing a composite substrate for a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0011] To fully understand the structure and effects of the present invention, exemplary embodiments of the invention have been described with reference to the accompanying drawings. However, it should be noted that the present invention is not limited to the following exemplary embodiments and can be implemented in various forms and with various modifications. The exemplary embodiments provided herein are intended to make the invention thorough and complete, and to fully convey the scope of the invention to those skilled in the art.

[0012] It is understood here that when a component is referred to as being "on" another component, the component may be "directly on" that other component, or there may be an intermediate third component. Furthermore, in the accompanying drawings, the thickness of the components may be exaggerated for the purpose of effectively describing the technical content. The same reference numerals always refer to the same elements.

[0013] Unless otherwise stated herein, singular expressions may include plural expressions. Furthermore, unless otherwise stated, the phrase “A or B” may mean “A but not B,” “B but not A,” or “A and B.” The term “including” and / or variations thereof as used herein do not exclude the presence or addition of one or more other components.

[0014] As used herein, the term "combination of them (the combination of them)" may refer to mixtures, stacks, complexes, copolymers, alloys, blends or reaction products.

[0015] Unless otherwise defined herein, particle size may be the average particle size. Furthermore, particle size is defined as the average particle size (D50), which represents the diameter of particles at a cumulative volume of approximately 50 vol% in the particle size distribution. The average particle size (D50) can be measured by methods known to those skilled in the art, for example, by a particle size analyzer, images from a transmission electron microscope (TEM), or images from a scanning electron microscope (SEM). Alternatively, the average particle size (D50) can be measured using a measuring device employing dynamic light scattering, wherein data analysis is performed to count the number of particles in each particle size range, and the average particle size (D50) value can then be calculated. Additionally, laser scattering methods can be used to measure the average particle size. In measurements using laser diffraction, for example, the target particles are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., the MT 3000 available from Microtrac) and irradiated with ultrasound at a power of about 60 W and about 28 kHz. The average particle size (D50) based on the particle size distribution in the measuring device can then be calculated.

[0016] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0017] Figure 1 This is a simplified conceptual diagram illustrating a rechargeable lithium battery according to an exemplary embodiment of the present invention. (Refer to...) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte solution ELL.

[0018] The positive electrode 10 and the negative electrode 20 can be separated from each other by a diaphragm 30. The diaphragm 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be in contact with the electrolyte solution ELL. The positive electrode 10, the negative electrode 20 and the diaphragm 30 can be immersed in the electrolyte solution ELL.

[0019] The electrolyte solution ELL may be or include a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte solution ELL, lithium ions can move toward the positive electrode 10 or the negative electrode 20 through the membrane 30.

[0020] Positive electrode 10 The positive electrode 10 for a rechargeable lithium battery may include a current collector COL1 and a positive electrode active material layer AML1 on the current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material, and may also include a binder and / or a conductive material.

[0021] For example, the positive electrode 10 may also include an additive configured as a sacrificial positive electrode.

[0022] Relative to 100 wt% of the positive electrode active material layer AML1, the positive electrode active material layer AML1 may comprise approximately 90 wt% to approximately 99 wt% of the positive electrode active material. Relative to 100 wt% of the positive electrode active material layer AML1, the amounts of binder and conductive material may each range from approximately 0.5 wt% to approximately 5 wt%.

[0023] The binder can be configured to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector COL1. Typical examples of binders may be or include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but embodiments of the invention are not limited thereto.

[0024] Conductive materials may be included to impart conductivity to the electrodes. Any material that does not cause chemical changes and is an electronically conductive material can be used in the battery. Examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0025] Al can be included as the current collector COL1, but the exemplary embodiments of the present invention are not limited thereto.

[0026] Positive electrode active material The positive electrode active material layer AML1 may include compounds capable of reversibly inserting and deintercalating lithium (lithiation intercalation compounds) as positive electrode active materials. For example, it may include at least one of lithium and a composite oxide of a metal such as or including at least one of cobalt, manganese, nickel and combinations thereof.

[0027] The composite oxide can be or includes lithium transition metal composite oxides, and examples include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0028] For example, it may include compounds represented by any of the following formulas. Li aA 1-b X b O 2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Mr 2-b X b O 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni 1-b-c Mr b X c O 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0≤e≤0.1);Li a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mr 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mr 1-g G g PO4(0.90≤a≤1.8,0≤g≤0.5);Li (3-f) Fe2(PO4)3(0≤f≤2);Li a FePO4(0.90≤a≤1.8).

[0029] In the above formula, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0030] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, wherein the nickel content of the high-nickel positive electrode active material is about 80 mol% or more, about 85 mol% or more, about 90 mol% or more, about 91 mol% or more, or about 94 mol% or more, relative to 100 mol% of metal other than lithium from lithium transition metal complex oxides. High-nickel positive electrode active materials can achieve high capacity and are therefore suitable for high-capacity, high-density rechargeable lithium batteries.

[0031] negative electrode 20 The negative electrode 20 for a rechargeable lithium battery may include a current collector COL2 and a negative electrode active material layer (or “negative electrode coating”) AML2 on the current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material and may also include a binder and / or a conductive material.

[0032] For example, the negative electrode active material layer AML2 may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0 wt% to about 5 wt% of conductive material.

[0033] The binder can be configured to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the current collector COL2. The binder may include at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0034] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, and combinations thereof.

[0035] The waterborne adhesive may be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxygenated alcohol, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0036] When an aqueous binder is included as the negative electrode binder, a cellulose compound capable of imparting viscosity may be further included. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0037] Dry adhesives can be or include polymeric materials capable of forming fibers. For example, dry adhesives can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0038] Conductive materials may be included to impart conductivity to the electrodes. Any material that does not cause a chemical change and is an electronically conductive material can be used in the battery. Examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0039] The current collector COL2 may be or include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0040] Negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 may include at least one of the following: materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and transition metal oxides.

[0041] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Examples of crystalline carbon may include at least one of graphite, such as irregular, planar, flake, spherical, or fibrous natural or artificial graphite, and examples of amorphous carbon may include at least one of soft carbon, hard carbon, mesophase pitch carbides, coke, etc.

[0042] The lithium metal alloy includes an alloy of lithium and a metal such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0043] The material capable of doping / dedoping lithium can be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof), and combinations of at least one of them. The Sn-based negative electrode active material can be or include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0044] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite can be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon can also be located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0045] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0046] The Si-based negative electrode active material or the Sn-based negative electrode active material can be included in combination with a carbon-based negative electrode active material.

[0047] Diaphragm 30 Depending on the type of rechargeable lithium battery, a separator 30 can be present between the positive electrode 10 and the negative electrode 20. The separator 30 can include at least one of polyethylene, polypropylene, polyvinylidene fluoride, and a multi-layer film of two or more layers thereof, for example, a mixed multi-layer film such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, a polypropylene / polyethylene / polypropylene trilayer separator, etc.

[0048] The separator 30 can include a porous substrate and a coating layer containing an organic material, an inorganic material, or a combination thereof on one or two surfaces of the porous substrate.

[0049] The porous substrate may be or include a polymer membrane, which is formed or includes a copolymer or mixture of two or more of the following polymers, said polymers being at least one of polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene.

[0050] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0051] Inorganic materials may include, but are not limited to, inorganic particles containing at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0052] Organic and inorganic materials can be mixed in a coating layer, or a coating layer containing organic materials and a coating layer containing inorganic materials can be stacked together.

[0053] Electrolyte solution ELL Electrolyte solutions (ELLs) used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0054] Non-aqueous organic solvents can be constructed as media for transporting ions that participate in the electrochemical reactions of a battery.

[0055] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0056] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0057] Ester solvents may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0058] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include at least one of ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether groups); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane; sulfolane, etc.

[0059] Non-aqueous organic solvents may be included alone or in combination of two or more solvents.

[0060] Furthermore, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and included, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0061] Lithium salts dissolved in organic solvents are configured to supply lithium ions in batteries, enabling rechargeable lithium batteries to operate fundamentally and improving lithium ion transport between the positive and negative electrodes. Typical examples of lithium salts may include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0062] Rechargeable lithium batteries Rechargeable lithium batteries can be classified according to their shape as cylindrical batteries, prismatic batteries, pouch batteries, or coin-shaped batteries, etc. Figures 2 to 5 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment, and Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type battery is shown. (See reference) Figures 2 to 5The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 3 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode terminal 70 shown, or for example Figure 4 The positive electrode terminal 71 and negative electrode terminal 72 shown herein form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0063] Figure 6 This is a cross-sectional view illustrating a rechargeable lithium battery including a composite substrate according to an exemplary embodiment of the present invention. Figure 7 It is shown Figure 6 A cross-sectional view of the composite material. Figure 8 It is Figure 7 The image is an enlarged version of M. For simplicity, the reference above is no longer provided. Figures 1 to 5 The description of the provided rechargeable lithium battery is a duplicate of any other description.

[0064] Reference Figure 6 The diagram shows a composite substrate CPS, a first battery cell CEL1 on one surface of the composite substrate CPS, and a second battery cell CEL2 on the other surface of the composite substrate CPS. Figure 6 The first battery cell CEL1, the second battery cell CEL2, and the composite substrate CPS can form a dual-cell battery. Figure 6 The first battery cell CEL1, the second battery cell CEL2, and the composite substrate CPS can form the above-mentioned reference. Figures 2 to 5 The electrode assembly 40 is described.

[0065] The first battery cell CEL1 and the second battery cell CEL2 may each include a first active material layer ACT1, a separator 30, a second active material layer ACT2, and a metal substrate MES. The second active material layer ACT2 may be disposed on a composite substrate CPS. The first active material layer ACT1 may be spaced apart from the second active material layer ACT2, with the separator 30 located between them. The metal substrate MES may be disposed on the first active material layer ACT1.

[0066] The first active substance layer ACT1 can be referenced above. Figure 1 The described active material layer is either AML1 (positive electrode) or AML2 (negative electrode). The second active material layer ACT2 can be any one of the above-described active material layers. Figure 1 The first active material layer ACT1 and the second active material layer AML2 are described. In an exemplary embodiment of the invention, the first active material layer ACT1 may be the positive electrode active material layer AML1, and the second active material layer ACT2 may be the negative electrode active material layer AML2. The metal substrate MES may be as described above. Figure 1 The described current collectors are COL1 or COL2.

[0067] The composite substrate CPS may include a support layer SPL and a third metal layer MEL3 and a fourth metal layer MEL4, each disposed on one side of the support layer SPL. The support layer SPL may constitute about 20 wt% to about 30 wt% of the composite substrate CPS.

[0068] The third metal layer MEL3 of the composite substrate CPS can contact the second active material layer ACT2 of the first battery cell CEL1. The fourth metal layer MEL4 of the composite substrate CPS can contact the second active material layer ACT2 of the second battery cell CEL2. The third metal layer MEL3 and the fourth metal layer MEL4 of the composite substrate CPS can correspond to the above reference. Figure 1 The described current collectors are COL1 or COL2.

[0069] The support layer SPL may comprise a polymer membrane. For example, the support layer SPL may have a thickness ranging from about 2 μm to about 10 μm. For example, the support layer SPL may comprise at least one of a polyethylene membrane, a polypropylene membrane, a polyvinylidene chloride membrane, and a multilayer membrane comprising combinations thereof. The support layer SPL may have desired or improved ion permeability and desired or improved mechanical strength.

[0070] The third metal layer MEL3 and the fourth metal layer MEL4 may each include at least one of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, iron, iron alloy, silver, and silver alloy.

[0071] In an exemplary embodiment of the present invention, the third metal layer MEL3 and the fourth metal layer MEL4 may each have a thickness ranging from about 0 μm to about 5 μm. For example, the third metal layer MEL3 and the fourth metal layer MEL4 may each have a thickness ranging from about 200 nm to about 5 μm. The support layer SPL may have a thickness ranging from about 2 μm to about 10 μm. The thickness of the support layer SPL may be greater than the thickness of each of the third metal layer MEL3 and the fourth metal layer MEL4.

[0072] The composite substrate CPS may include a first terminal ENP1 at one end. The metal substrate MES of the first battery cell CEL1 may include a second terminal ENP2 at one end. The metal substrate MES of the second battery cell CEL2 may include a third terminal ENP3 at one end.

[0073] A first connector TAB1 can be disposed at the first end ENP1 of the composite substrate CPS. The first connector TAB1 may include a first connecting portion UPP1, a second connecting portion UPP2, and an extension portion EXP. The first connecting portion UPP1 can contact the third metal layer MEL3 of the composite substrate CPS. The second connecting portion UPP2 can contact the fourth metal layer MEL4 of the composite substrate CPS. The extension portion EXP can connect the first connecting portion UPP1 and the second connecting portion UPP2 together. The extension portion EXP can extend substantially horizontally from the first end ENP1 toward the first direction D1.

[0074] The third metal layer MEL3 and the fourth metal layer MEL4 can be electrically connected via the first connector TAB1. The first connector TAB1 can be configured to transmit or apply a common voltage to the third metal layer MEL3 and the fourth metal layer MEL4.

[0075] The second terminal tab TAB2 can be disposed at the second terminal ENP2 of the metal substrate MES of the first battery cell CEL1. The second terminal tab TAB2 can be configured to transmit or apply voltage to the metal substrate MES of the first battery cell CEL1. The third terminal tab TAB3 can be disposed at the third terminal ENP3 of the metal substrate MES of the second battery cell CEL2. The third terminal tab TAB3 can be configured to transmit or apply voltage to the metal substrate MES of the second battery cell CEL2.

[0076] The first connector TAB1 can form the above reference. Figures 2 to 4 The positive electrode terminal (or positive electrode lead terminal) and negative electrode terminal (or negative electrode lead terminal) described herein. The second terminal TAB2 and the third terminal TAB3 can constitute the above-mentioned reference. Figures 2 to 4 The other of the positive electrode terminal block (or positive electrode lead terminal block) and negative electrode terminal block (or negative electrode lead terminal block) described.

[0077] Reference Figure 7 and Figure 8The support layer SPL may include multiple joints BA. Each of the multiple joints BA may have an irregular shape and may have a three-dimensional structure. For example, each of the multiple joints BA may include a protrusion in a direction substantially perpendicular to the surface PW_U of the support layer SPL (e.g., a third direction D3) and / or in a direction parallel to the surface of the support layer SPL (e.g., a first direction D1 or a second direction D2). The multiple joints BA may be spaced apart along the first direction D1 and / or the second direction D2.

[0078] The third metal layer MEL3 and the fourth metal layer MEL4 can be disposed on both surfaces of the support layer SPL. Each of the third metal layer MEL3 and the fourth metal layer MEL4 may include a first metal layer MEL1 and a second metal layer MEL2 on the first metal layer MEL1.

[0079] A first metal layer MEL1 may be disposed on the surface of the support layer SPL and may include an adhesion enhancer and a first copper. The first metal layer MEL1 may have a thickness in the range of about 2 nm to about 5 nm. The adhesion enhancer may be chemically bonded to the surface of the support layer SPL and may be chemically bonded to multiple bonding portions BA.

[0080] The adhesion enhancer may include a first portion and a second portion, the first portion being chemically bonded to the surface of the support layer SPL and comprising a hydroxyalkylene group, and the second portion comprising an amine group configured to adsorb a first copper group. The hydroxyalkylene group may represent a hydroxyl functional group (-OH) and an alkylene chain (C... n H 2n The structure is a bonded structure. An amino group can represent a group that includes an amine functional group. For example, an amino group can represent an alkyl group (C10) that includes an amine functional group (e.g., -NH- or -NH2). n H 2n+1 ) or alkylene (C n H 2n ).

[0081] Adhesion enhancers may include compounds of Formula 1 below.

[0082] Formula 1:

[0083] Group "R1" is or includes direct bonding or C1 to C1 bonds. 10Any of the alkylene groups, and "n" can be a natural number equal to or greater than 1 or an integer in the range of about 0 to about 10. For example, "n" can be an integer in the range of about 1 to about 10. The wavy line shown in Formula 1 can represent a portion of the functional group on the surface of the support layer SPL or a portion of the polymer chemically bonded to the surface of the support layer SPL. For example, the wavy line can represent a functional group including oxygen (e.g., -O) on the surface of the plurality of junctions BA. 2- The part of the chemical bond (-COOH or -OH).

[0084] The first part may include the following formula 2.

[0085] Formula 2:

[0086] As described above, the wavy line adjacent to R1 can represent the portion chemically bonded to functional groups on the surface of the support layer SPL or to the attached polymer on the surface of the support layer SPL. Another wavy line can represent the portion chemically bonded to the second portion.

[0087] The second part may include the following formula 3.

[0088] Formula 3:

[0089] The wavy line shown in Formula 3 can represent the portion chemically linked to the first part. The amino group in the second part can stabilize the copper ion. For example, the copper ion can be stabilized by an amino group having a free electron pair that can bond to the copper ion. For example, the copper ion can be stabilized by forming a chelate through coordination bonding with the amino group. As described below, the second part can cause the first copper ion to adsorb onto the adhesion enhancer.

[0090] The second metal layer MEL2 may include a second copper layer. The second metal layer MEL2 may have a greater thickness than the first metal layer MEL1. The second metal layer MEL2 may have a thickness in the range of about 150 nm to about 3 μm. The adhesive strength between the support layer SPL and the third metal layer MEL3 (or the fourth metal layer MEL4) may be in the range of about 700 N / m to about 1200 N / m.

[0091] According to an exemplary embodiment of the present invention, the first metal layer MEL1 may include an adhesion enhancer. The adhesion enhancer may include a first portion and a second portion, the first portion comprising a hydroxyalkylene group and the second portion comprising an amino group configured to adsorb first copper. Copper ions can be stably adsorbed onto the adhesion enhancer via the second portion. The support layer SPL and the metal layers MEL3 and MEL4 may provide desired or improved adhesive strength via the first and second portions.

[0092] Figures 9 to 17 This is a cross-sectional view illustrating a method for preparing a composite material for a rechargeable lithium battery according to an exemplary embodiment of the present invention. For the sake of simplicity, references to the above are provided without redundancy. Figures 1 to 8 The description of the rechargeable lithium battery is repeated.

[0093] Reference Figure 9 A support layer SPL comprising a polymer film can be provided. The surface of the support layer SPL can be modified. The surface modification step PS can include, for example, performing plasma treatment or acid treatment. Plasma treatment can include, for example, oxygen and argon.

[0094] Reference Figure 10 The modified surface of the support layer SPL can include multiple bonding portions BA of the support layer SPL. Each of the multiple bonding portions BA can have an irregular shape and a three-dimensional structure. The multiple bonding portions BA can be formed by physical stimulation through plasma or chemical stimulation through acid treatment.

[0095] Each of the multiple junctions BA may include oxygen-containing functional groups on its surface. Oxygen-containing functional groups may include, for example, -O. 2- At least one of -OH and -COOH.

[0096] Reference Figure 11 The first compound C1, including a glycidyl group, can be bonded (e.g., chemically bonded) to the modified surface of the support layer SPL. One end of the first compound C1, excluding the epoxy functional group, can be chemically bonded to the modified surface of the support layer SPL. The first compound C1 can be chemically bonded to oxygen-containing functional groups in each of a plurality of junctions. For example, the first compound C1 can be chemically bonded to -O. 2- The first compound C1 may be or include at least one of, for example, glycidyl methacrylate, glycidyl methyl ether, polyglycidyl methacrylate, and combinations thereof.

[0097] Reference Figure 12 An adhesion enhancer AE can be formed on the surface of the support layer SPL. A second compound, including an amine group, can be bonded to the epoxy functional groups of the first compound to form the adhesion enhancer AE. For example, the second compound can be or include diethylenetriamine (DETA). The adhesion enhancer AE can be formed via the following reaction formula 1.

[0098] Reaction 1:

[0099] Group R1 is or includes direct bonding or C1 to C1 bonds. 10Any of the alkylene groups, and "n" can be a natural number equal to or greater than 1 or an integer in the range of 0 to 10.

[0100] The formation of the adhesion enhancer AE can be carried out at a temperature ranging from about 60°C to about 80°C. That is, reaction formula 1 above can be carried out at a temperature ranging from about 60°C to about 80°C. The wavy lines shown in reaction formula 1 above can represent portions that are chemically bonded to functional groups or polymers on the surface of the support layer SPL.

[0101] Reference Figure 13 , Figure 14 and Figure 15 The support layer SPL can be impregnated with a first solution SL1 comprising first copper ions. The first copper ions can be adsorbed onto the adhesion enhancer AE. The first solution SL1 can include a first metal salt and a catalyst, the first metal salt comprising the first copper ions Cu1. The first metal salt can be or include at least one of, for example, CuSO4 and CuCl2. The first metal salt in the first solution SL1 can be present, for example, at a concentration in the range of about 0.12 M to about 0.25 M. The catalyst can be or include at least one of, for example, palladium (Pd) and platinum (Pt). The first solution can have a pH in the range of about 3 to about 5. When the pH of the first solution meets the above-mentioned numerical range, the amount of first copper ions adsorbed onto the adhesion enhancer AE can be increased and can be adsorbed substantially uniformly.

[0102] The first copper ion Cu1 can be stabilized by the second part of the adhesion enhancer AE. The first copper ion Cu1 can be stabilized by the amino group (e.g., -NH- or -NH2) of the second part. For example, the first copper ion Cu1 can be stabilized by an amino group having a free electron pair that can bond with the first copper ion Cu1. For example, the first copper ion Cu1 can be stabilized by forming a chelate through coordination bonding with the amino group.

[0103] Reference Figure 13 and Figure 16 A first metal layer MEL1 can be formed. Forming the first metal layer MEL1 may include impregnating the support layer SPL with a second solution SL2 containing a reducing agent.

[0104] The reducing agent may include at least one of, for example, formaldehyde, glucose, sodium hypophosphite, and boron compounds. The second solution SL2 may also include a complexing agent, a stabilizer, and a pH adjuster. The complexing agent may include, for example, ethylenediaminetetraacetic acid (EDTA). The stabilizer may include, for example, at least one of triethanolamine (TEA) and 2,2'-bipyridine. The pH adjuster may include, for example, NaOH. The second solution SL2 may have a pH in the range of, for example, from about 11 to about 13. When the pH of the second solution SL2 meets the numerical range described above, the first metal layer MEL1 may be formed substantially uniformly on the surface of the support layer SPL.

[0105] Reference Figure 13 and Figure 17 A second metal layer MEL2 can be formed on the first metal layer MEL1. Forming the second metal layer MEL2 may include impregnating the support layer SPL and the first metal layer MEL1 on the support layer SPL with a third solution SL3 containing second copper ions.

[0106] Reference Figure 17 The formation of the second metal layer MEL2 can be performed, for example, by an electroplating process. The support layer SPL and the first metal layer MEL1 on the support layer SPL can be connected to the negative electrode, and a copper electrode containing second copper ions can be included as the positive electrode. In this case, a constant voltage in the range of about 5V to about 15V can be applied.

[0107] The third solution SL3 may further include an electrolyte, a complexing agent, and a pH adjuster. The electrolyte may include at least one of, for example, copper sulfate (CuSO4), sulfuric acid (H2SO4), hydrochloric acid (HCl), copper chloride (CuCl2), and acetic acid (C2H4O2). The complexing agent may include, for example, EDTA. The pH adjuster may include, for example, at least one of, hydrochloric acid, acetic acid, sulfuric acid, and citric acid. The third solution SL3 may have a pH in the range of, for example, from about 0.5 to about 2.5. When the pH of the third solution SL3 meets the above-mentioned numerical range, the second metal layer MEL2 can be substantially uniformly formed on the first metal layer MEL1.

[0108] The first metal layer MEL1 and the second metal layer MEL2 may include the same metal (e.g., copper), so the second metal layer MEL2 can be stably formed on the first metal layer MEL1.

[0109] Figure 18 This is a flowchart illustrating a method for preparing a composite substrate for a rechargeable lithium battery according to an example embodiment. Figure 18In this method 1800, operations 1810, 1820, and 1830 are included. Operation 1810 includes modifying the surface of the support layer. For example, modifying the surface of the support layer includes performing at least one of plasma treatment and acid treatment. In another example, the modified surface of the support layer includes -O 2- At least one of -OH and -COOH. In the example, the support layer comprises a polymer film, and the polymer film comprises at least one of a polyethylene film, a polypropylene film, a polyvinylidene chloride film, and a multilayer film comprising a combination thereof.

[0110] Operation 1820 includes forming a first metal layer comprising a first copper on a modified surface of a support layer. For example, forming the first metal layer includes: bonding a first compound comprising a glycidyl group to the modified surface of the support layer; bonding a second compound comprising an amino group to one end of the first compound to form an adhesion enhancer; impregnating the support layer with a first solution comprising first copper ions; and impregnating the support layer with a second solution comprising a reducing agent to reduce the first copper ions. In an example, the first solution has a pH in the range of about 3 to about 5. For example, the reducing agent in the second solution includes at least one selected from formaldehyde, glucose, sodium hypophosphite, and a boron compound. In another example, the formation of the adhesion enhancer is performed at a temperature in the range of about 60°C to about 80°C.

[0111] In the example, the adhesion enhancer includes compounds of formula 1: Formula 1:

[0112] R1 includes direct bonding or C1 to C1 bonding. 10 One of the alkylene groups, and n is a natural number equal to or greater than 1. In the example, n equals 2.

[0113] Operation 1830 includes forming a second metal layer containing a second copper on the first metal layer. In an example, forming the second metal layer includes impregnating a support layer and the first metal layer on the support layer with a third solution containing second copper ions. For example, the third solution further includes an electrolyte, a complexing agent, and a pH adjuster, wherein the electrolyte includes at least one selected from copper sulfate (CuSO4), sulfuric acid (H2SO4), hydrochloric acid (HCl), copper chloride (CuCl2), and acetic acid (C2H4O2).

[0114] The present invention is described below by way of examples and comparative examples.

[0115] Example 1 Prepare a 2 μm thick polypropylene film as a support layer. Treat the surface of the support layer with oxygen plasma and argon plasma. Impregnate the plasma-treated support layer with a solution containing 0.1 M glycidyl methacrylate and using ethanol as a solvent. Impregnate the support layer with a solution containing 0.2 M diethylenetriamine and using water as a solvent, and then heat to 80°C to form an adhesion enhancer on the support layer.

[0116] Subsequently, the support layer was impregnated with a first solution comprising 0.12 M CuSO4 and palladium (Pd). Then, the support layer was impregnated with a second solution comprising formaldehyde, EDTA, TEA, and NaOH to form the first metal layer. The second solution was prepared by mixing 0.1 M formaldehyde, 0.01 M EDTA, 0.02 M TEA, and 0.2 M NaOH. The second solution had a pH of 11. The first metal layer had a thickness of 3 nm.

[0117] The first metal layer and the support layer were impregnated with a third solution. The third solution was prepared by mixing 0.12 M CuSO4, 0.01 M EDTA, and 0.15 M acetic acid. A negative electrode was connected to a positive electrode made of copper metal on the first metal layer and the support layer, and a constant voltage of 6 V was applied. Subsequently, a second metal layer was formed on the first metal layer. The first and second metal layers had a total thickness of 12 μm.

[0118] Example 2 The composite substrate was prepared in the same manner as in Example 1, except that a polyethylene film was used as a support layer.

[0119] Comparison Example 1 A 2 μm thick polypropylene film was prepared as a support layer. A first metal layer made of a nickel-chromium alloy was deposited onto the support layer by a sputtering process. The nickel-chromium alloy had a thickness of 13 μm. Subsequently, a second metal layer was formed in the same manner as in Example 1.

[0120] Comparison Example 2 A 2 μm thick polyethylene film was prepared as a support layer. A first metal layer made of a nickel-chromium alloy was deposited onto the support layer by a sputtering process. The nickel-chromium alloy had a thickness of 13 μm. Subsequently, a second metal layer was formed in the same manner as in Example 1.

[0121] Evaluation Example The support layer was fixed, and the first metal layer was pulled at a 90° angle. The bond strength was measured according to ASTM D6862. The results of the bond strength evaluation are shown in Table 1 below.

[0122] Table 1:

[0123] Referring to Table 1, Example 1 was found to exhibit greater adhesive strength than Comparative Example 1. Similarly, Example 2 was found to exhibit greater adhesive strength than Comparative Example 2. Therefore, the composite substrate according to the exemplary embodiment of the present invention has greater stability.

[0124] According to an exemplary embodiment of the present invention, the composite substrate may include a support layer and a metal layer.

[0125] The metal layer may include a first metal layer containing an adhesion enhancer.

[0126] Adhesion enhancers may include a first portion comprising a hydroxyalkylene group and a second portion comprising an amine group configured to adsorb a first copper group.

[0127] The support layer and the first metal layer can be stably bonded through the first part, and copper ions can be stably adsorbed onto the support layer through the second part.

[0128] The support layer and the metal layer can provide the desired or improved adhesive strength through the first part and the second part.

[0129] In addition, rechargeable lithium batteries incorporating this composite substrate can be provided that exhibit the desired or improved stability.

[0130] Although exemplary embodiments of the invention have been described above with reference to the accompanying drawings, the invention can be applied in other specific forms without altering its technical concept or essential characteristics. Therefore, the above exemplary embodiments are to be considered illustrative rather than restrictive in all respects.

Claims

1. A composite substrate for a rechargeable lithium battery, the composite substrate comprising: Support layer, including polymer film; as well as A metal layer, on the support layer, comprising at least one of copper and copper oxide. The metal layer comprises: a first metal layer on the surface of the support layer and including an adhesion enhancer and a first copper layer; and a second metal layer on the first metal layer and including a second copper layer. The adhesion enhancer comprises: a first portion, chemically bonded to the surface of the support layer and comprising a hydroxyalkylene group; and a second portion, comprising an amine group configured to adsorb the first copper.

2. The composite substrate for rechargeable lithium batteries according to claim 1, wherein, The adhesion enhancer comprises the following compound of formula 1: Formula 1: R1 includes direct bonding and C1 to C1 bonding. 10 One of the alkylene groups, and n is an integer in the range of 0 to 10.

3. The composite substrate for rechargeable lithium batteries according to claim 2, wherein, n equals 2.

4. The composite substrate for rechargeable lithium batteries according to claim 1, wherein, The adhesive strength between the metal layer and the support layer is in the range of 700 N / m to 1200 N / m.

5. The composite substrate for a rechargeable lithium battery according to claim 1, wherein, The first metal layer has a thickness in the range of 2 nm to 5 nm.

6. The composite substrate for a rechargeable lithium battery according to claim 1, wherein the composite substrate further comprises a negative electrode coating layer on the metal layer. in, The negative electrode coating layer includes a negative electrode active material, a binder, and a conductive material.

7. The composite substrate for a rechargeable lithium battery according to claim 1, wherein, The polymer film includes at least one of polyethylene film, polypropylene film, polyvinylidene chloride film, and multilayer films comprising combinations thereof.

8. The composite substrate for a rechargeable lithium battery according to claim 1, wherein, The support layer has a thickness in the range of 2 μm to 10 μm.

9. A method for preparing a composite substrate for a rechargeable lithium battery, the method comprising the following steps: The surface of the support layer is modified; A first metal layer comprising a first copper is formed on the modified surface of the support layer; as well as A second metal layer comprising a second copper is formed on the first metal layer. The step of forming the first metal layer includes: A first compound comprising glycidyl groups is bonded to the modified surface of the support layer; A second compound comprising an amine group is bonded to one end of the first compound to form an adhesion enhancer; The support layer is impregnated with a first solution containing first copper ions; and The support layer is impregnated with a second solution containing a reducing agent to reduce the first copper ions.

10. The method according to claim 9, wherein, The step of modifying the surface of the support layer includes performing at least one of plasma treatment and acid treatment.

11. The method according to claim 9, wherein, The modified surface of the support layer includes -O 2- At least one of -OH and -COOH.

12. The method according to claim 9, wherein, The adhesion enhancer comprises a compound of formula 1: Formula 1: R1 includes direct bonding and C1 to C1 bonding. 10 One of the alkylene groups, and n is an integer in the range of 0 to 10.

13. The method according to claim 12, wherein, n equals 2.

14. The method according to claim 9, wherein, The reducing agent in the second solution includes at least one of formaldehyde, glucose, sodium hypophosphite, and boron compounds.

15. The method according to claim 9, in, The step of forming the second metal layer includes impregnating the support layer and the first metal layer on the support layer with a third solution containing second copper ions.

16. The method according to claim 15, wherein, The third solution also includes electrolytes, complexing agents, and pH adjusters, and The electrolyte includes at least one of copper sulfate, sulfuric acid, hydrochloric acid, copper chloride, and acetic acid.

17. The method according to claim 9, wherein, The first solution has a pH in the range of 3 to 5.

18. The method according to claim 9, wherein, The step of forming the adhesion enhancer is performed at a temperature in the range of 60°C to 80°C.

19. The method according to claim 9, wherein, The support layer comprises a polymer film, and The polymer film includes at least one of polyethylene film, polypropylene film, polyvinylidene chloride film, and multilayer films comprising combinations thereof.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The composite substrate according to claim 1; as well as Battery cells, on the composite substrate, in, The battery cell includes: A first active material layer is disposed on the metal layer; A diaphragm is formed on the first active material layer; A second active material layer is disposed on the diaphragm; and A metal substrate is placed on the second active material layer.

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