Method of manufacturing high-entropy alloy from lithium-ion battery cathode wastes using hydrogen plasma arc reduction

Abstract

The present invention relates to a method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma atmosphere in a hydrogen atmosphere. More specifically, the invention relates to a method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma atmosphere in a hydrogen atmosphere, characterized by using high-temperature arc plasma generated in a hydrogen atmosphere to reduce a high-entropy alloy from LiNi0.8Co0.1Mn0.1O2 (NCM811; Lithium Nickel Cobalt Manganese Oxide), LiCoO2 (LCO; Lithium Cobalt Oxide), LiFePO4 (LFP; Lithium Iron Phosphate), etc. contained in the spent lithium battery cathode material. According to the present invention, through a process of plasma reduction of spent lithium battery cathode materials, it is possible to not only recover valuable metals but also design high-entropy alloys with desired characteristics from the spent battery cathode materials in a single step. In particular, since high-entropy alloys with excellent mechanical and thermal properties can be obtained directly through this process, there is an effect of obtaining high-value-added metals from spent lithium battery cathode materials.

Description

Technology Field

[0001] The present invention relates to a method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma atmosphere, and more specifically, to a method for reducing LiNi contained in the spent lithium battery cathode material using high-temperature arc plasma generated in a hydrogen atmosphere. 0.8 Co 0.1 Mn 0.1 The present invention relates to a method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma in a hydrogen atmosphere, characterized by producing a high-entropy alloy reduced from O2 (NCM811; Lithium Nickel Cobalt Manganese Oxide), LiCoO2 (LCO; Lithium Cobalt Oxide), LiFePO4 (LFP; Lithium Iron Phosphate), etc. Background Technology

[0002] Currently, as interest in eco-friendly energy gains global attention, the volume of waste batteries is rapidly increasing alongside the rise in the use of secondary batteries. According to statistical surveys, electric vehicle sales in 2023 reached 14 million units, a sixfold increase compared to 2018; consequently, the number of scrapped vehicles is projected to reach 4.11 million in 2030 and 42.77 million in 2040.

[0003] Next-generation waste battery recycling technology can alleviate environmental issues and raw material supply shortages, and reduce dependence on overseas imports of cathode materials, which are currently landfilled only in specific countries. Global companies and research institutions are devoting significant effort to developing waste battery recycling technologies, and the battery recycling market is projected to grow to approximately 200 trillion won by 2040.

[0004] In the case of lithium batteries utilized as cathode materials for conventional lithium batteries, High Ni cathode materials are mainly used in Korea, and LiNi 0.6 Co 0.2 Mn 0.2O2(NCM622), LiNi 0.7 Co 0.2 Mn 0.1 O2(NCM721), LiNi 0.8 Co 0.1 Mn 0.1 Cathode materials such as O2 (NCM811) are primarily used. In China, which has a high volume of battery production, inexpensive LiFePO4 (LFP) is the main cathode material. Both NCM batteries and LFP materials contain valuable metals such as Ni and Co, as well as metals such as Fe, which are widely used in everyday life. Furthermore, metals like Ni, Co, and Fe have numerous applications, including the ability to be used as high-entropy (super invar) superalloys. It is expected that recycling and utilizing the metals present in these battery powders will create a significant impact.

[0005] The prior patents related to waste lithium battery recycling technology currently in use are as follows.

[0006] Methods include a method for crushing and dry heat-treating cell-unit batteries and separating them through particle size separation and magnetic separation (Patent Application No. 10-2023-0038360), a method for recovering precursors such as Ni, Co, and Mn using strong sulfates (Patent Application No. 10-2021-0122698), a method for controlling the alloy size of Ni using sulfuric acid and a complex heat treatment process (Patent Application No. 10-2022-0130603), a method for extracting Co using a complex process in an acidic atmosphere utilizing a mixed solvent (Patent Application No. 10-2022-0029821), a method for obtaining lithium hydroxide through a relatively complex process (Patent Application No. 10-2020-0166203), and a method for recovering cathode material particles using an oxygen atmosphere and sodium hydroxide (Patent Application No. 10-2021-0120343).

[0007] Conventional battery recycling methods, such as the technology described above, apply a process in which waste lithium batteries are crushed and ground into black powder and recycled using wet and dry methods. However, wet and dry methods have problems in that the process is complex, time-consuming, and has a low yield, and is not environmentally friendly because it generates toxic gases and involves repeated oxidation and reduction processes.

[0008] These differences can be summarized as follows.

[0009] Prior art number Differences from the present invention Patent Application No. 10-2023-0038360 The complex processes of crushing, grinding, freezing, and heat treatment Patent Application No. 10-2022-0130603 Use of sulfuric acid and complex heat treatment processes Patent Application No. 10-2022-0029821 Co extraction method utilizing a complex process in an acidic atmosphere using a mixed solvent Patent Application No. 10-2021-0122698 It is not true recycling through eco-friendly reduction using very strong sulfates. Patent Application No. 10-2021-0120343 Recovery of cathode material particles through a method involving an oxygen atmosphere and sodium hydroxide Patent Application No. 10-2020-0166203 Obtaining lithium hydroxide through a complex process

[0011] The present invention presents a Hydrogen Plasma Reduction (HPR) method that extracts Ni, Co, and Fe from waste batteries very quickly and simply by utilizing hydrogen and a plasma arc, deviating from conventional methods applied in the prior art that are harmful to the environment, such as strong acids and strong bases, and are complex and time-consuming.

[0012] However, there exists a prior patent that applies a technology for reducing and separating waste metals using conventional plasma reduction technology, which differs from the present invention as follows.

[0013] The invention of Patent Application No. 10-2019-0128689 is technically different from the present invention in that it utilizes plasma to process waste aluminum (metal) and extracts high-purity aluminum without using hydrogen, and in the case of waste aluminum, aluminum metal is extracted from metal rather than ceramic.

[0014] Furthermore, the inventions of Patent Applications No. 10-2016-0025143 and No. 10-2014-0047960 utilized metallic titanium in the technology for reducing impurities in titanium by generating arc plasma in a hydrogen atmosphere, and in the case of recovering copper from copper-containing waste, they utilized hydrogen generated from LPG gas in addition to recovering metal from metal, which differs from the present invention in that hydrogen is directly added.

[0015] In addition, the invention of Patent Application No. 10-1998-0058249 presents a technology for recovering valuable metals from industrial waste using plasma; however, this invention also does not use hydrogen and differs in that waste batteries are compositionally different from industrial waste.

[0016] Prior art number Differences from the present invention Patent Application No. 10-2019-0128689 Extracting metal from metal. Hydrogen is not used when utilizing plasma. Patent Application No. 10-2016-0025143 Extracting metal from metal. Patent Application No. 10-2014-0047960 Extracting metal from metal. Utilizing LPG gas when using plasma. Patent Application No. 10-1998-0058249 Industrial waste and waste batteries have different compositions, and hydrogen is not used when utilizing plasma.

[0018] Meanwhile, high-entropy alloys are alloys composed of at least four major elements in equal or nearly similar compositional ratios, and they possess excellent mechanical and thermal properties. As the number of constituent elements increases, the configurational entropy (ΔS) increases, and the Gibbs free energy (ΔG) decreases. Furthermore, they are gaining attention in the metals field because properties such as mechanical, thermal, magnetic, and corrosion resistance can be controlled depending on which elements are added and in what quantities.

[0019] FeCoNiCu high-entropy alloys are alloys that possess soft magnetic properties and excellent mechanical properties, such as high strength and ductility. Various combinations of high-entropy alloys, including FeCoNiCu, FeCoNiMnAl, and FeCoNiCuAl, can be derived from waste battery materials. Due to their soft magnetic properties and excellent mechanical characteristics, such as high ductility and strength even at cryogenic temperatures, these high-entropy alloys are materials with very high industrial value, suitable for applications such as ships and pipes for polar regions, cryogenic liquid gas transport containers, electric generators, electric motors, electromagnets, and magnetic shielding materials. Prior art literature

[0020] (Patent Document 0001) KR 10-2021-0045212 A(Patent Document 0002) KR 10-1771842 B1(Patent Document 0003) KR 10-1553475 B1(Patent Document 0004) KR 10-2000-0042150 A The problem to be solved

[0021] The present invention, aimed at solving the aforementioned problems, provides a method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma environment in a hydrogen atmosphere, which enables the rapid and efficient recovery of valuable metals contained in the spent lithium battery cathode material and the simultaneous production of a high-entropy alloy.

[0022] In addition, the present invention aims to provide a method for producing a high-entropy alloy by reducing spent lithium battery cathode materials in an arc plasma in a hydrogen atmosphere, which enables the direct production of a high-entropy alloy with excellent properties while reprocessing oxidized cathode materials of NCM, LCO, and LFP batteries in an environmentally friendly manner. means of solving the problem

[0023] The present invention, devised to solve the aforementioned problems, comprises a method for manufacturing a high-entropy alloy from a cathode material of a spent lithium battery using an arc plasma, the method comprising: a first step of preparing a cathode material pellet using the cathode material contained in the spent lithium battery; a second step of preparing a copper pellet using a negative electrode current collector contained in the spent lithium battery; a third step of exposing a mixture of the cathode material pellet and the copper pellet to a plasma arc to induce a reduction reaction; and a fourth step of separating the plasma-reduced high-entropy alloy from impurity particles.

[0024] In the first step above, the cathode material pellet is composed of a mixture of NCM, LCO, and LFP, wherein the NCM, LCO, and LFP are mixed in a weight ratio of (5.5~8):(4~6):(1.5~3.5).

[0025] The first step is characterized by grinding the cathode material, which is composed of a mixture of the NCM, the LCO, and the LFP, into a powder form, and compressing the cathode material processed into a powder form in a mold to form pellets.

[0026] In the second step above, the copper pellet is characterized by using a negative electrode current collector in the form of copper foil contained in the waste lithium battery by pelletizing it.

[0027] The copper contained in the above NCM, above LCO, above LFP, and above copper pellets is mixed in a weight ratio of (5.5~8):(4~6):(1.5~3.5):(4.5~7).

[0028] The above third step is characterized by introducing the anode material mixed with the anode material pellet and the copper pellet into a hydrogen plasma reduction device (100) and reducing the anode material in a hydrogen atmosphere.

[0029] The above hydrogen plasma reduction device (100) comprises: a chamber (102) having a space formed inside; a cathode (104) installed on the inner upper surface of the chamber (102); an anode (106) installed on the inner bottom surface of the chamber (102); a power supply unit connected to the cathode (104) and the anode (106) to supply power; a supply tank (108) for supplying gas for plasma generation; and a gas inlet (110) formed on one side of the chamber (102) and connected to a gas pipe connected to the supply tank (108).

[0030] The above supply tank (108) is characterized by storing hydrogen and argon gas and supplying them into the interior of the chamber (102).

[0031] The above supply tank (108) is characterized by supplying gas containing 90% argon and 10% hydrogen.

[0032] It further includes a fifth step of washing and post-treating the separated high-entropy alloy.

[0033] The high-entropy alloy comprises iron, cobalt, nickel, and copper, wherein the iron has a composition ratio of 25 at% to 28 at%, the cobalt has a composition ratio of 22 at% to 24 at%, the nickel has a composition ratio of 23 at% to 25 at%, and the copper has a composition ratio of 25 at% to 27 at%. Effects of the invention

[0034] According to the present invention, through a process of plasma reduction of spent lithium battery cathode materials, it is possible to not only recover valuable metals but also design high-entropy alloys with desired characteristics from the spent battery cathode materials in a single step. In particular, since high-entropy alloys with excellent mechanical and thermal properties can be obtained directly through this process, there is an effect of obtaining high-value-added metals from spent lithium battery cathode materials.

[0035] In addition, by utilizing a hydrogen atmosphere plasma reduction process, the reduction efficiency is increased and the process speed is accelerated compared to the conventional method using Ar gas, and the rapid reaction speed enables the production of high-entropy alloys. Brief explanation of the drawing

[0036] FIG. 1 is a flowchart showing the process of a method for manufacturing a high-entropy alloy according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing a reaction process carrying out the process illustrated in FIG. 1. Figure 3 is a conceptual diagram showing the detailed structure of a plasma chamber. Figure 4 shows an SEM image and EDS analysis results of a high-entropy alloy produced by the present invention. Figure 5 shows the XRD analysis results of the high-entropy alloy produced by the present invention. Figure 6 shows SEM and EBSD images of a high-entropy alloy produced by the present invention. Specific details for implementing the invention

[0037] Hereinafter, with reference to the drawings, a "method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma atmosphere" according to an embodiment of the present invention will be described.

[0038] FIG. 1 is a flowchart showing the process of a method for manufacturing a high-entropy alloy according to an embodiment of the present invention, FIG. 2 is a conceptual diagram showing the reaction process carrying out the process shown in FIG. 1, and FIG. 3 is a conceptual diagram showing the detailed structure of a plasma chamber.

[0039] To carry out the high-entropy alloy manufacturing method of the present invention, a five-step process as shown in FIG. 1 is performed.

[0040] First, as a first step, a cathode material contained in a waste lithium battery is prepared. (S102) In the present invention, a high-entropy alloy was manufactured using NCM, LCO, and LFP cathode materials, but other cathode materials may be used.

[0041] The entire assembly, including the aluminum anode and the anode active material coated thereon, is separated from the spent lithium battery. When separating the anode material from the spent lithium battery, it is preferable to separate the anode material itself, excluding the negative electrode and separator contained within the battery cell. Since various methods can be applied to the technology for separating the anode material from the spent lithium battery, the present invention does not specifically limit the separation method.

[0042] The separated cathode material may contain a binder.

[0043] It is preferable to grind the separated cathode material into a powder form, and to grind it appropriately to a size suitable for introduction into a plasma chamber.

[0044] It is desirable to shape the crushed cathode material powder into a form optimized for the plasma reduction reaction. In the case of cathode material processed into powder form, it may be fed directly without processing, but it is preferable to pelletize the cathode material using a mold with a diameter of approximately 10 mm to 20 mm and feed it into the reduction chamber. Most preferably, pelletization can be carried out by compressing approximately 200 mg or more of cathode material to a pressure of 600 MPa or more using a mold with a diameter of 13 mm.

[0045] In the present invention, copper is mixed with pelletized cathode material powder. It is preferable to use copper from materials contained in spent lithium batteries, and in the present invention, high-purity copper foil used as a negative electrode current collector is used. Since the copper current collector is obtained in the form of a metal lump, it can be pelletized for use. Copper pellets are exposed to plasma together with NCM, LCO, and LFP mixed pellets. At this time, the mixing ratio is preferably set by weight as NCM:LCO:LFP:Cu = (5.5~8):(4~6):(1.5~3.5):(4.5~7). Most preferably, the composition is configured so that NCM:LCO:LFP:Cu = 6:5:2.4:6. However, the mixing ratio may vary when using actual cathode materials and copper current collectors from spent lithium batteries.

[0046] It is known that the magnetism of high-entropy alloys increases as the copper content increases. Therefore, by adding more copper, the magnetism of high-entropy alloys can be enhanced, thereby increasing their industrial utility value in applications such as electric generators, electric motors, and magnetic shielding materials.

[0047] As the next step, the cathode pellet and copper pellet are exposed to a plasma arc in a hydrogen atmosphere to induce a reduction reaction. (S106)

[0048] The initial state cathode material powder and copper pelletized in the previous step are introduced into a hydrogen plasma reduction device (100) to remove oxygen through a reduction reaction.

[0049] A hydrogen plasma reduction device (100) has a cathode (104) and an anode (106) installed inside a chamber (102), and a supply tank (108) for injecting gas for plasma generation may be provided on the outside. A gas pipe connected to the supply tank (108) is connected to a gas inlet (110) formed on one side of the chamber (102), and hydrogen and argon gases supplied from the supply tank (108) flow into the chamber (102) through the gas inlet (110).

[0050] A pressure gauge (112) and a thermometer (114) for measuring internal pressure and temperature, respectively, may be installed in the chamber (102).

[0051] Typically, the cathode (104) can be installed on the inner upper surface of the chamber (102) and extend vertically through the upper surface. The anode (106) is installed on the inner bottom surface of the chamber (102), and the anode material (10) before reduction can be placed on the anode (106). In the present invention, a mixture of anode material pellets and copper pellets is referred to as the 'anode material (10)'.

[0052] A power supply unit (not shown in the drawing) is connected to the cathode (104) and the anode (106), and power is supplied from the power supply unit to generate plasma between the cathode (104) and the anode (106).

[0053] When power is supplied to the cathode (104) and the anode (106) while supplying a plasma gas, such as argon gas, through the gas inlet (110), an arc is generated at the electrical contact, changing the argon gas into a plasma state. The heat generated from the plasma melts the anode material (10) placed on the anode (106) before reduction, and the hydrogen supplied along with the argon gas causes a reduction reaction. The hydrogen combines with the oxygen bonded to the iron (Fe) and is discharged, leaving the anode material after reduction. The high-entropy alloy remains as a metallic element inside the anode material after reduction.

[0054] In the present invention, after placing the anode material (10) inside a Cu water-cooled chamber (maintained at 20°C), an arc plasma is generated in an argon and hydrogen mixed gas atmosphere while supplying a gas containing 90% argon and 10% hydrogen to reduce the oxide anode material (10) at a very high temperature.

[0055] It is preferable to set the pressure inside the chamber (102) to be in the range of -0.8 bar to -0.4 bar during the reduction reaction. It is also preferable to set the distance between the anode material specimen to be reduced and the plasma node to be about 1 cm. Furthermore, it is preferable to set the time for generating a plasma arc to cause the reduction reaction to occur to be 2 to 10 seconds.

[0056] In order to obtain a sufficient amount of high-entropy alloy from the cathode material (10) introduced, it is desirable to repeat the above plasma reduction reaction 2 to 6 times while setting the pressure, time, and distance between the cathode material specimen and the plasma node to be the same.

[0057] In the next step, the high-entropy alloy produced through the plasma reduction reaction and the impurity particles are separated (S108). When the high-entropy alloy produced through the plasma reduction reaction is contained within the anode material (10) in powder form, the pure high-entropy alloy can be collected by applying impact to the reduced powder.

[0058] Figure 4 shows an SEM image and EDS analysis results of a high-entropy alloy produced by the present invention, Figure 5 shows the XRD analysis results of a high-entropy alloy produced by the present invention, and Figure 6 shows an SEM image and EBSD image of a high-entropy alloy produced by the present invention.

[0059] The composition of an ideal quaternary high-entropy alloy must be synthesized such that each element is equal to or close to 25 at%. As a result of analyzing the alloy produced and collected by the manufacturing method of the present invention using scanning electron microscopy energy-dispersive X-ray spectroscopy, it was confirmed that the compositions of Fe, Co, Ni, and Cu were approximately 27 at%, 23 at%, 24 at%, and 26 at%, respectively, which is the composition of an ideal quaternary high-entropy alloy. Furthermore, since phosphorus (P), which is introduced into the alloy from LFP powder and adversely affects alloy performance (such as reduced ductility), was not detected, it was confirmed that the alloy can be obtained solely through hydrogen plasma exposure without an additional dephosphorization process.

[0060] In addition, it is known that in the case of high-entropy alloys, alloying elements must be dissolved in a single crystal structure such as FCC (Face-Centered Cubic) or BCC (Body-Centered Cubic). It has been reported that the FeCoNiCu high-entropy alloy has an FCC crystal structure. Through the X-ray diffraction test results in Fig. 5, it can be seen that the FeCoNiCu alloy synthesized using the technology of the present invention has an FCC single phase.

[0061] As shown in Fig. 6, it can be confirmed that it has an FCC single crystal structure in the results of Electron Back Scatter Diffraction (EBSD) analysis.

[0062] As the final fifth step, the separated high-entropy alloy undergoes post-processing steps such as washing. (S110)

[0063] Although preferred embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the technical configuration of the present invention described above may be implemented in other specific forms without altering the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive, and the scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0064] 10 : Cathode material 100 : Hydrogen Plasma Reduction Device 102 : Chamber 104 : Cathode 106 : Anode 108 : Supply tank 110: Gas inlet 112 : Pressure gauge 114 : Thermometer

Claims

Claim 1 A method for producing a high-entropy alloy from a cathode material of a spent lithium battery using an arc plasma, comprising: a first step of preparing a cathode material pellet using a cathode material contained in the spent lithium battery; a second step of preparing a copper pellet using a negative electrode current collector contained in the spent lithium battery; a third step of exposing a mixture of the cathode material pellet and the copper pellet to a plasma arc to induce a reduction reaction; and a fourth step of separating the plasma-reduced high-entropy alloy and impurity particles; a method for producing a high-entropy alloy by arc plasma reduction of a spent lithium battery cathode material in a hydrogen atmosphere. Claim 2 A method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma in a hydrogen atmosphere, wherein, in the first step, the cathode material pellet is composed of a mixture of NCM, LCO, and LFP, and the NCM, LCO, and LFP are mixed in a weight ratio of (5.5~8):(4~6):(1.5~3.5). Claim 3 A method for producing a high-entropy alloy by reducing a waste lithium battery cathode material in an arc plasma in a hydrogen atmosphere, wherein, in the second step, the first step comprises grinding a cathode material composed of a mixture of the NCM, the LCO, and the LFP into a powder form, and compressing the cathode material processed into a powder form in a mold to form pellets. Claim 4 A method for producing a high-entropy alloy by reducing a waste lithium battery cathode material in an arc plasma in a hydrogen atmosphere, wherein, in the second step, the copper pellet is used by pelletizing a negative electrode current collector in the form of copper foil contained in the waste lithium battery. Claim 5 A method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma in a hydrogen atmosphere, characterized in that, in claim 4, the copper contained in the NCM, the LCO, the LFP, and the copper pellet is mixed in a weight ratio of (5.5~8):(4~6):(1.5~3.5):(4.5~7). Claim 6 A method for producing a high-entropy alloy by reducing a waste lithium battery cathode material in an arc plasma in a hydrogen atmosphere, wherein, in the first step, the third step is characterized by introducing the cathode material mixed with the cathode material pellet and the copper pellet into a hydrogen plasma reduction device (100) and reducing the cathode material in a hydrogen atmosphere. Claim 7 In claim 6, the hydrogen plasma reduction device (100) comprises: a chamber (102) in which a space is formed inside; a cathode (104) installed on the inner upper surface of the chamber (102); an anode (106) installed on the inner bottom surface of the chamber (102); a power supply device connected to the cathode (104) and the anode (106) to supply power; a supply tank (108) for supplying gas for plasma generation; and a gas inlet (110) formed on one side of the chamber (102) and connected to a gas pipe connected to the supply tank (108). A method for producing a high-entropy alloy by arc plasma reduction of a waste lithium battery anode material in a hydrogen atmosphere. Claim 8 A method for producing a high-entropy alloy by reducing a waste lithium battery cathode material in an arc plasma atmosphere in a hydrogen atmosphere, wherein, in claim 7, the supply tank (108) stores hydrogen and argon gas and supplies them into the interior of the chamber (102). Claim 9 A method for producing a high-entropy alloy by reducing a spent lithium battery cathode material in an arc plasma atmosphere in a hydrogen atmosphere, wherein, in claim 8, the supply tank (108) supplies a gas containing 90% argon and 10% hydrogen. Claim 10 A method for producing a high-entropy alloy by reducing a waste lithium battery cathode material in an arc plasma in a hydrogen atmosphere, further comprising: a fifth step of washing and post-treating the separated high-entropy alloy in claim 1. Claim 11 A method for producing a high-entropy alloy by arc plasma reduction of a spent lithium battery cathode material in a hydrogen atmosphere, wherein, in claim 1, the high-entropy alloy comprises iron, cobalt, nickel, and copper, wherein the iron has a composition ratio of 25 at% to 28 at%, the cobalt has a composition ratio of 22 at% to 24 at%, the nickel has a composition ratio of 23 at% to 25 at%, and the copper has a composition ratio of 25 at% to 27 at%.

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