JP5739044B1 - Copper alloy foil for negative electrode current collector of secondary battery, method for producing copper alloy foil for negative electrode current collector of secondary battery, negative electrode for secondary battery, and secondary battery - Google Patents

Abstract

The present invention provides a technique for further suppressing the breakage of a copper alloy foil during charging and discharging of a secondary battery. SOLUTION: It contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin and 0.01% by mass or more of silver, and when both tin and silver are contained, the total of tin and silver The content is 0.20% by mass or less, the balance is made of copper and inevitable impurities, the tensile strength after heating for 1 hour at 200 ° C. is 450 N / mm 2 or more, and the elongation is 2.0% or more. To. [Selection] Figure 1

Description

  The present invention relates to a copper alloy foil, a method for producing the copper alloy foil, a negative electrode for a secondary battery, and a secondary battery.

  The negative electrode of the secondary battery (non-aqueous electrolyte battery) includes, for example, a copper alloy foil as a negative electrode current collector, and a negative electrode active material layer provided on any main surface of the copper alloy foil, including a negative electrode active material. It is equipped with. The negative electrode is formed by applying a slurry containing a negative electrode active material or the like on any main surface of the copper alloy foil, and then heating and drying to provide a negative electrode active material layer. For this reason, the copper alloy foil may be softened by heating when forming the negative electrode. If the copper alloy foil is softened, the copper alloy foil may be broken when the negative electrode active material expands and contracts as the secondary battery is charged and discharged. Then, there exists a technique which suppresses the fracture | rupture of the copper alloy foil at the time of charging / discharging of a secondary battery by raising the tensile strength of the copper alloy foil after heating at the time of forming a negative electrode (for example, patent document 1). reference).

JP 2011-108442 A

  However, after heating for a predetermined time under a predetermined temperature condition, even when the copper alloy foil has a predetermined tensile strength, the negative electrode active material expands and contracts during charge / discharge of the secondary battery, The copper alloy foil may break.

  The objective of this invention is providing the technique which solves the said subject and suppresses the fracture | rupture of the copper alloy foil in the case of charging / discharging of a secondary battery more.

According to one embodiment of the present invention, when 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more of silver is contained, and both tin and silver are contained. The total content of tin and silver is 0.20% by mass or less, the balance is made of copper and inevitable impurities, and the tensile strength after heating at 200 ° C. for 1 hour is 450 N / mm ² or more, A copper alloy foil having an elongation of 2.0% or more is provided.

  According to another aspect of the present invention, when containing at least one of 0.04 mass% or more and 0.20 mass% or less of tin, 0.01 mass% or more of silver, and containing both tin and silver Has a total content of tin and silver of 0.20% by mass or less, a casting step of casting an ingot made of copper and unavoidable impurities as a remainder, and performing predetermined hot rolling on the ingot, A hot rolling step for forming a hot-rolled material, a cold-rolling treatment and an annealing treatment for the hot-rolled material, a first cold-rolling step for forming an annealed material, and the annealed material Manufacturing a copper alloy foil having a second cold rolling step in which cold rolling with a workability of 60% or less is performed continuously a predetermined number of times so that the total workability becomes 95% or more A method is provided.

According to still another aspect of the present invention, it contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more of silver, and contains both tin and silver. In this case, the total content of tin and silver is 0.20% by mass or less, the balance is copper and inevitable impurities, the tensile strength is 450 N / mm ² or more, and the elongation is 2.0% or more. Provided is a negative electrode for a secondary battery, comprising: a negative electrode current collector formed of an alloy foil; and a negative electrode active material layer provided on at least one main surface of the negative electrode current collector and having a negative electrode active material. Is done.

According to still another aspect of the present invention, it contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more of silver, and contains both tin and silver. In this case, the total content of tin and silver is 0.20% by mass or less, the balance is copper and inevitable impurities, the tensile strength is 450 N / mm ² or more, and the elongation is 2.0% or more. A negative electrode current collector formed of an alloy foil; and a negative electrode provided on at least one main surface of the negative electrode current collector and including a negative electrode active material layer having a negative electrode active material; a positive electrode; the negative electrode; A secondary battery is provided that includes a separator that electrically insulates the positive electrode, and a negative electrode, the positive electrode, and a container that contains the separator and into which an electrolyte is injected.

  ADVANTAGE OF THE INVENTION According to this invention, the fracture | rupture of the copper alloy foil in the case of charging / discharging of a secondary battery can be suppressed more.

It is a schematic block diagram of a secondary battery provided with the copper alloy foil concerning one Embodiment of this invention. It is a flowchart which shows the manufacturing process of the copper alloy foil, negative electrode, and secondary battery concerning one Embodiment of this invention.

<One Embodiment of the Present Invention>
The structure of the copper alloy foil according to one embodiment of the present invention will be described.

(1) Configuration of Copper Alloy Foil The copper alloy foil according to this embodiment contains at least one of a predetermined amount of tin (Sn) and a predetermined amount of silver (Ag), with the balance being copper (Cu) and inevitable impurities. It is made up of. Moreover, the copper alloy foil has a tensile strength of 450 N / mm ² or more and an elongation of 2.0% or more after heating for 1 hour at 200 ° C., for example. As described above, the copper alloy foil after the predetermined heat treatment has a predetermined tensile strength and has a predetermined elongation, so that it could not be suppressed only by having the predetermined tensile strength. Can be prevented from breaking. The tensile strength is a value measured based on ASTM International (former American Society for Testing and Materials) E-345. The elongation is a value measured based on IPC-TM-650 2.4.18.

  In the copper alloy foil, at least one of Sn and Ag is preferably dissolved. Thereby, the heat resistance of copper alloy foil can be improved. That is, even if the predetermined heat treatment is performed on the copper alloy foil, the copper alloy foil is less likely to be softened, and the tensile strength can be prevented from decreasing.

  When Sn is contained in the copper alloy foil, the content (concentration) of Sn in the copper alloy foil is preferably 0.04% by mass or more and 0.20% by mass or less, for example, 0.12% by mass or less. More preferably.

If the Sn content is less than 0.04% by mass, the tensile strength of the copper alloy foil may decrease. That is, the tensile strength of the copper alloy foil (hereinafter, also referred to as “H alloy copper alloy foil”) before performing the predetermined heat treatment may be reduced. For example, the tensile strength of the copper alloy foil in the H material state may be less than 450 N / mm ² . In addition, the amount of Sn dissolved in the copper alloy foil may decrease. For example, Sn may react with unavoidable impurities, and Sn may not be dissolved in the copper alloy foil. Compounds produced by the reaction of Sn and inevitable impurities (for example, SnO produced by the reaction of Sn and oxygen (O), one of the inevitable impurities) improve the heat resistance of the copper alloy foil. I can't let you. Therefore, the effect of improving the heat resistance of the copper alloy foil by containing Sn may not be obtained. As a result, desired heat resistance may not be obtained.

By making the Sn content 0.04% by mass or more, the tensile strength of the copper alloy foil in the state of H material can be improved. For example, the tensile strength of the copper alloy foil in the state of H material can be 450 N / mm ² or more. Further, Sn can be dissolved in the copper alloy foil. Thereby, the heat resistance of copper alloy foil can be improved and desired heat resistance can be obtained. Therefore, the fall of the tensile strength of the copper alloy foil after performing predetermined heat processing can be suppressed. For example, the copper alloy foil has a tensile strength of 450 N / mm ² or more even after heating for 1 hour at 200 ° C.

  However, if the Sn content exceeds 0.20% by mass, the conductivity of the copper alloy foil may decrease. Moreover, although the fall of the tensile strength of the copper alloy foil after performing predetermined heat processing with respect to copper alloy foil can be suppressed, even if predetermined heat processing is performed with respect to copper alloy foil, Ductility may not improve. By making Sn content 0.20 mass% or less, the electroconductive fall of copper alloy foil can be suppressed. For example, the conductivity of the copper alloy foil can be 80% IACS or higher. Moreover, the ductility of copper alloy foil can be improved by performing predetermined heat processing with respect to copper alloy foil. That is, the elongation of the copper alloy foil after performing the predetermined heat treatment can be made higher than the elongation of the copper alloy foil in the H material state. For example, the elongation of the copper alloy foil after heating for 1 hour at 200 ° C. can be 2.0% or more. By making Sn content 0.12 mass% or less, the electroconductive fall of copper alloy foil can be suppressed more. For example, the conductivity of the copper alloy foil can be 85% IACS or higher.

  When Ag is contained in the copper alloy foil, the content (concentration) of Ag in the copper alloy foil is, for example, preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and 0 More preferably, it is 10% by mass or less.

  If the Ag content is less than 0.01% by mass, the tensile strength of the copper alloy foil in the H material state may be lowered. In addition, the amount of Ag dissolved in the copper alloy foil may decrease. For example, Ag may react with inevitable impurities, and Ag may not be dissolved in the copper alloy foil. A compound produced by a reaction between Ag and an inevitable impurity (for example, AgO produced by a reaction between Ag and one of the inevitable impurities) can improve the heat resistance of the copper alloy foil. Can not. Therefore, the effect of improving the heat resistance of the copper alloy foil by containing Ag may not be obtained. As a result, desired heat resistance may not be obtained.

By making the Ag content 0.01% by mass or more, the tensile strength of the copper alloy foil in the state of H material can be improved. For example, the tensile strength of the copper alloy foil in the state of H material can be 450 N / mm ² or more. Further, Ag can be dissolved in the copper alloy foil. Thereby, the heat resistance of copper alloy foil can be improved and desired heat resistance can be obtained. Therefore, the fall of the tensile strength of the copper alloy foil after performing predetermined heat processing can be suppressed. For example, the tensile strength of the copper alloy foil after heating for 1 hour under the condition of 200 ° C. can be 450 N / mm ² or more. By making the content of Ag 0.03% by mass or more, the heat resistance of the copper alloy foil can be further improved while further improving the tensile strength of the copper alloy foil in the H material state. For example, the tensile strength of the copper alloy foil in the state of H material is set to 480 N / mm ² or more, and the tensile strength of the copper alloy foil after heating for 1 hour at 200 ° C. is set to 480 N / mm ² or more. it can.

  However, Ag is an expensive element. Therefore, if the content of Ag exceeds 0.10% by mass, the ductility of the copper alloy foil may not be improved even if a predetermined heat treatment is performed on the copper alloy foil. Moreover, the manufacturing cost of copper alloy foil may become high. Moreover, even if it is a case where content of Ag is made more than 0.10 mass%, the tensile strength of the copper alloy foil of the state of H material, and the heat resistance of copper alloy foil are respectively Ag content of 0.1. It is almost the same as the copper alloy foil of 10% by mass. That is, an effect commensurate with the manufacturing cost may not be obtained. By making Ag content 0.10 mass% or less, the ductility of copper alloy foil after performing predetermined heat processing with respect to copper alloy foil can be improved. That is, the elongation of the copper alloy foil after performing the predetermined heat treatment can be made higher than the elongation of the copper alloy foil in the H material state. For example, the elongation after heating for 1 hour at 200 ° C. can be 2.0% or more. Moreover, it can suppress that the manufacturing cost of copper alloy foil becomes high.

  When both Sn and Ag are contained in the copper alloy foil, the contents of Sn and Ag are within the above-mentioned predetermined ranges, respectively, and the total of the contents of Sn and Ag (Sn and Ag) The total content) is preferably 0.20% by mass or less.

  When the total content of Sn and Ag exceeds 0.20% by mass, the conductivity of the copper alloy foil may be lowered. Moreover, even if it performs predetermined heat processing with respect to copper alloy foil, the ductility of copper alloy foil may not improve. By making the total content of Sn and Ag 0.20% by mass or less, a decrease in conductivity of the copper alloy foil can be suppressed. For example, the conductivity of the copper alloy foil can be 80% IACS or higher. Moreover, the ductility of copper alloy foil can be improved by performing predetermined heat processing with respect to copper alloy foil. That is, the elongation of the copper alloy foil after performing the predetermined heat treatment can be made higher than the elongation of the copper alloy foil in the H material state. For example, the elongation after heating for 1 hour at 200 ° C. can be 2.0% or more.

  As a base material of the copper alloy foil, for example, oxygen-free copper (OFC) having a purity of 99.9% or more may be used. Thereby, the quantity of O as an inevitable impurity contained in copper alloy foil can be reduced. Therefore, the amount of oxide produced in the copper alloy foil can be reduced. Specifically, it is possible to suppress the generation of SnO or AgO due to the reaction of O with Sn or Ag in the copper alloy foil. In addition, by reducing the amount of Sn and Ag that react with O in the copper alloy foil, the amount of Sn and Ag dissolved in the copper alloy foil can be increased without increasing the content of Sn and Ag. it can.

(2) Configuration of Negative Electrode Next, the configuration of the negative electrode in which the above-described copper alloy foil is used as the negative electrode current collector will be described. The negative electrode is formed by providing a negative electrode active material layer on at least one main surface of a copper alloy foil as a negative electrode current collector. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may further contain a conductive additive, a binder, and the like.

  The contents of the negative electrode active material, the conductive additive, and the binder (binder) in the negative electrode active material layer can be appropriately adjusted according to the characteristics required for the negative electrode. The content of the negative electrode active material in the negative electrode active material layer is preferably 60% by mass or more and 98% by mass or less, and the content of the conductive auxiliary agent is preferably 0% by mass or more and 20% by mass or less. The content of is preferably 2% by mass or more and 10% by mass or less. In addition, that content of a conductive support agent is 0 mass% means that a conductive support agent is not contained in a negative electrode active material layer.

  As the negative electrode active material, a compound that can occlude or desorb (release) an electrolyte (for example, lithium (Li) ion) in an electrolytic solution used in a secondary battery 10 described later is used. For example, as a negative electrode active material, carbonaceous materials such as graphite, carbon fiber, coke, spherical carbon, metals such as Li, Sn, silicon (Si), lithium titanium oxide, tin oxide, silicon oxide, tungsten oxide At least one of metal compounds such as lithium compounds, lithium tin alloys, lithium silicon alloys and the like is used. In particular, at least a part of the negative electrode active material contained in the negative electrode active material layer is preferably a metal compound or a lithium alloy containing at least one of Sn metal, Si metal, Sn, and Si, for example. Thereby, the capacity | capacitance of the below-mentioned secondary battery 10 can be made larger.

  As the conductive auxiliary agent, for example, carbon-based fine particles such as acetylene black and ketjen black, and graphite-based fine particles can be used. Thereby, the electroconductivity of a negative electrode can be stabilized more.

  As the binder, for example, polyvinylidene fluoride (PVDF), polyimide (PI), polyamideimide (PAI), or water-dispersed styrene butadiene rubber (SBR) can be used.

(3) Configuration of Secondary Battery Subsequently, the configuration of the secondary battery including the above-described negative electrode will be described with reference to FIG. 1 using a coin cell type lithium ion secondary battery as an example. FIG. 1 is a schematic cross-sectional view of a secondary battery 10 according to the present embodiment.

  As shown in FIG. 1, the secondary battery 10 includes a container. The container includes an upper container 11A including a top plate and a side plate provided so as to surround the side surface of the top plate, and a lower container 11B including a side plate provided so as to surround the side surface of the bottom plate and the bottom plate. Each of the upper container 11A and the lower container 11B is made of, for example, stainless steel. The top plate of the upper container 11A and the bottom plate of the lower container 11B are each formed in a circular shape. 11 A of upper containers are formed so that the plane area of the top plate of 11 A of upper containers may become smaller than the plane area of the bottom plate of the lower container 11B. The upper container 11A and the lower container 11B are arranged so that at least a part of the side plate of the upper container 11A is accommodated in the lower container 11B.

  Between the side plate of the upper container 11A and the side plate of the lower container 11B, a gasket 12 is provided so as to fill a space between the side plate of the upper container 11A and the side plate of the lower container 11B. That is, the gasket 12 is formed to function as a container lid. The gasket 12 is made of, for example, polypropylene. Thereby, while being able to seal a container, the insulation between upper container 11A and lower container 11B can be ensured.

  The upper container 11A includes a copper alloy foil 13A as a negative electrode current collector and a negative electrode active material layer 13B. The negative electrode 13 formed, for example, in a disk shape is accommodated and held therein. Specifically, the negative electrode 13 is accommodated in the upper container 11A so that the negative electrode active material layer 13B faces the bottom plate of the lower container 11B. That is, the upper container 11 </ b> A also functions as a negative electrode case that houses the negative electrode 13. The upper container 11A is provided with a negative electrode terminal.

  The lower container 11B accommodates and holds a positive electrode 14 described later. Specifically, the positive electrode 14 is accommodated in the lower container 11B such that a positive electrode active material layer 14B described later faces the top plate of the upper container 11A. That is, the lower container 11B also functions as a positive electrode case that houses and holds the positive electrode 14. The lower container 11B is provided with a positive electrode terminal.

The positive electrode (counter electrode) 14 is formed, for example, by providing a positive electrode active material layer 14B containing a positive electrode active material on at least one main surface of a positive electrode current collector (metal foil) 14A. The positive electrode 14 is formed in a disk shape, for example. As the positive electrode current collector 14A, for example, an aluminum (Al) foil can be used. As the positive electrode active material, for example, a metal composite oxide containing lithium (Li) such as lithium cobaltate (LiCoO ₂ ) or manganese spinel (LiMn ₂ O ₄ ) can be used.

  A separator 15 is provided between the negative electrode 13 and the positive electrode 14. Specifically, the separator 15 is disposed so as to be interposed between the negative electrode active material layer 13B and the positive electrode active material layer 14B. The separator 15 is preferably formed so that the plane area is larger than the plane areas of the negative electrode 13 and the positive electrode 14. For example, the separator 15 may be formed so that the diameter is longer than the diameters of the negative electrode 13 and the positive electrode 14. Thereby, the negative electrode 13 and the positive electrode 14 can be insulated more reliably. The separator 15 is made of, for example, a porous synthetic resin film. Specifically, the separator 15 is preferably formed of a polyolefin polymer porous film (porous film). For example, the separator 15 may be formed of a porous film of polyethylene or polypropylene. Thereby, the separator 15 can hold | maintain electrolyte solution because the below-mentioned electrolyte solution enters into the hole of a porous film.

  An electrolytic solution is injected into the container. The electrolytic solution is generated by dissolving an electrolyte in an organic solvent. The content (concentration) of the electrolyte in the electrolytic solution can be appropriately adjusted according to the use of the secondary battery 10, the type of the organic solvent, and the like.

  As the organic solvent, for example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane compounds and the like can be used. In particular, as the organic solvent, at least one non-aqueous solvent selected from the group consisting of carbonates and ethers may be used. As the organic solvent, for example, propylene carbonate, ethylene carbonate (EC), 1,2-dimethoxyethane, dimethyl carbonate (DMC), diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, or a mixed solvent thereof may be used. Since these organic solvents have a high dielectric constant, low viscosity, and excellent electrolyte solubility, the charge / discharge efficiency of the secondary battery 10 can be improved.

As the electrolyte, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ inorganic salts, derivatives of these inorganic salts, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN At least one of (SO ₂ C ₂ F ₅ ) ₂ , organic salts of LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and derivatives of these organic salts may be used. Thereby, the battery performance of the secondary battery 10 can be improved. Further, even when the secondary battery 10 is used in a temperature range other than room temperature, higher battery performance can be maintained.

  In the electrolytic solution, additives other than the electrolyte such as vinylene carbonate (VC) may be added.

(4) Manufacturing method of copper alloy foil, negative electrode, and secondary battery Next, the manufacturing method of the copper alloy foil, negative electrode, and secondary battery concerning this embodiment is demonstrated using FIG. FIG. 2 is a flowchart showing the manufacturing process of the copper alloy foil, the negative electrode, and the secondary battery according to this embodiment.

<Copper alloy foil forming step (S10)>
For example, a copper alloy foil is formed using a melt casting method.

(Casting process (S11))
Cu (for example, oxygen-free copper) as a base material is melted in a nitrogen atmosphere using, for example, a high-frequency melting furnace or the like to produce a molten copper. Subsequently, in a nitrogen atmosphere using a high-frequency melting furnace or the like, a predetermined amount (for example, 0.04 mass% or more and 0.20 mass% or less) of Sn, a predetermined amount (for example, 0.01 mass%) in a molten copper. At least one of the above Ag) is added and mixed to produce a molten copper alloy. In addition, when adding both Sn and Ag, it is good to add so that the total content (total addition amount) of Sn and Ag may be 0.20 mass% or less. Then, the molten copper alloy thus produced is poured into a mold and then cooled, and contains at least one of 0.04 mass% to 0.20 mass% Sn and 0.01 mass% or more Ag. When both Sn and Ag are contained, the total content of Sn and Ag is 0.20% by mass or less, and a copper alloy ingot having a predetermined shape made of copper and inevitable impurities is cast. (Melting).

(Hot rolling process (S12))
After the casting step (S11) is completed, a pretreatment for homogenizing segregation occurring in the ingot, that is, in the cast structure is performed. As the pretreatment, a heat treatment for holding the ingot for a predetermined time may be performed in a temperature range equal to or higher than a temperature at which the crystal structure in the ingot becomes a homogeneous solid solution in an equilibrium state. For example, the ingot may be heated for 30 minutes or longer under conditions of 800 ° C. or higher and 950 ° C. or lower.

  Hot rolling is performed on the pretreated ingot. Specifically, the ingot is heated at a predetermined degree of processing (for example, the total degree of processing is 95%) in a state where the temperature of the ingot is maintained in the temperature range heated in the pretreatment (that is, 800 ° C. or more and 950 ° C. or less). Hot rolling is performed to form a hot rolled material having a predetermined thickness (for example, 12 mm).

(First cold rolling step (S13))
After the hot rolling step (S12) is completed, the first cold rolling treatment and the recrystallization annealing treatment are performed on the hot rolling material to form a recrystallization annealing material having a predetermined thickness. Specifically, the first cold at which the total degree of work becomes, for example, 40% to 70% by repeatedly performing cold rolling with a degree of work of about 10% to 20% continuously for a predetermined number of times. The hot rolling treatment and the recrystallization annealing treatment are alternately repeated a predetermined number of times to form a recrystallization annealing material having a predetermined thickness (for example, 0.15 mm to 1.0 mm). The recrystallization annealing treatment is preferably performed so that the grain size of the crystal grains after annealing (after recrystallization) becomes a predetermined grain size (for example, 10 μm to 20 μm). For example, as the recrystallization annealing treatment, heat treatment may be performed for several seconds to several hours in a furnace that is in a temperature range of 600 ° C. to 900 ° C.

(Second cold rolling step (S14))
After the first cold rolling step (S13) is completed, a second cold rolling process is performed in which the recrystallized annealed material is cold rolled a predetermined number of times to obtain a copper having a predetermined thickness (for example, 20 μm or less). An alloy foil is formed. As the second cold rolling process, by repeating cold rolling in which the degree of work r at one time is, for example, 60% or less, preferably 40% or less and 5% or more, the total work degree R is, for example, It is preferable to perform a process of 95% or more. In addition, when performing multiple times of cold rolling as 2nd cold rolling process, multiple times of cold rolling are performed continuously, without interposing a recrystallization annealing process between each cold rolling.

When cold rolling with a degree of work r of more than 60% is performed, the amount of processing heat generated during cold rolling may increase. Therefore, during cold rolling, the recrystallization annealed material or rolled material that is cold-rolled may be heated by processing heat. For example, the rolled material may be heated to a temperature at which recrystallization occurs. In addition, a rolling material means the recrystallization annealing material after performing at least 1 cold rolling in a 2nd cold rolling process (S14). When recrystallization occurs in the rolled material, the strength (tensile strength) of the formed copper alloy foil (that is, the copper alloy foil in the H material state) may be reduced. For example, the tensile strength of the copper alloy foil in the state of H material may not be 450 N / mm ² or more. In addition, when cold rolling with a degree of work r of more than 60% is performed, a crystal structure different from a normal rolled structure (crystalline structure generated in the rolled material by performing cold rolling) in the rolled material May occur. For example, a crystal structure (shear band) that obliquely crosses in the thickness direction of the rolled material may occur in the rolled material. The shear band existing in the rolled material hinders the alignment of crystal planes and tends to be the starting point of fracture. Therefore, even when the second cold rolling process in which the total degree of work is 95% or more is performed, the ductility of the copper alloy foil after the predetermined heat treatment cannot be improved. is there. For example, the elongation of the copper alloy foil after heating for 1 hour at 200 ° C. may not be 2.0% or more.

By setting the workability r of one cold rolling to 60% or less, the amount of processing heat generated during cold rolling can be reduced. Therefore, it can suppress that recrystallization arises in a rolling material. As a result, it can suppress that the tensile strength of the formed copper alloy foil (copper alloy foil of the state of H material) falls. For example, the tensile strength of the copper alloy foil in the state of H material can be 450 N / mm ² or more. Moreover, the crystal orientation of the rolled material can be enhanced. For example, it can suppress that a shear band arises in a rolling material. Therefore, the ductility of the copper alloy foil after performing the predetermined heat treatment can be improved. For example, the elongation of the copper alloy foil after heating for 1 hour at 200 ° C. can be 2.0% or more. By setting the working degree r of one cold rolling to 40% or less, the amount of processing heat generated during cold rolling can be further reduced. Therefore, it can suppress more that recrystallization arises in a rolling material. Moreover, it can suppress more that a shear band arises in a rolling material.

  However, if the working degree r of one cold rolling is less than 5%, the number of cold rolling operations repeated until the total working degree R becomes, for example, 95% or more may increase. As a result, the manufacturing cost of the copper alloy foil may increase. This can be eliminated by setting the working degree r of one cold rolling to 5% or more. Therefore, an increase in the manufacturing cost of the copper alloy foil can be suppressed.

In addition, the workability r of one cold rolling is calculated | required from following (Formula 1). Note that equation (1), t ₀ is the thickness of the rolled material before rolling one cold (or recrystallization annealed material), t is the rolled material after the rolling one cold Is the thickness.
(Equation 1)
Degree of processing r (%) = {(t ₀ −t) / t ₀ } × 100

  The total workability R of the cold rolling performed in the second cold rolling treatment is preferably 95% or more, more preferably 97% or more, further preferably 98% or more, and 99.5% or less. Is more preferable.

As the total working degree R increases, the rolled material can be work-hardened by cold rolling, and the tensile strength of the copper alloy foil to be formed can be increased. For example, when the total workability R exceeds 80%, the tensile strength of the copper alloy foil in the H material state can be set to 450 N / mm ² or more. However, if the total workability R is less than 95%, the ductility of the copper alloy foil in the H material state may not be improved. Moreover, when the total workability R is less than 95%, it is possible to suppress a decrease in the tensile strength of the copper alloy foil after performing the predetermined heat treatment, but even if the predetermined heat treatment is performed, the copper alloy foil Ductility may not be improved. By setting the total workability R to 95% or more, the ductility of the copper alloy foil in the state of H material can be improved. In addition, the ductility of the copper alloy foil after the predetermined heat treatment is improved more than the copper alloy foil in the state of the H material while suppressing a decrease in the tensile strength of the copper alloy foil after the predetermined heat treatment. Can be made. For example, the elongation can be 2.0% or more while the tensile strength of the copper alloy foil after heating for 1 hour at 200 ° C. is 450 N / mm ² or more. By setting the total workability R to 97% or more, the ductility of the copper alloy foil in the H material state can be further improved. Therefore, the elongation of the copper alloy foil after heating for 1 hour under the condition of 200 ° C. can be, for example, 2.5% or more. By setting the total workability R to 98% or more, the ductility of the copper alloy foil in the H material state can be further improved. Therefore, the elongation of the copper alloy foil after heating for 1 hour under the condition of 200 ° C. can be, for example, 3.0% or more.

  However, a rolled material that has been work-hardened by performing a predetermined number of cold rollings and has a high tensile strength is more difficult to be further reduced by cold rolling with a degree of processing of 60% or less. Sometimes. For example, when the total workability R exceeds 99.5%, the reduction amount of the rolled material that is reduced by one cold rolling is extremely reduced. Therefore, if a cold rolling process with a total workability exceeding 99.5% is to be performed, the number of cold rolling operations (that is, the number of rolling passes) may have to be extremely increased. Therefore, the manufacturing cost of the copper alloy foil may increase. By making the total workability 99.5% or less, it is possible to suppress an increase in the manufacturing cost of the copper alloy foil.

The total processing degree R is obtained from the following (Equation 2). In (Equation 2), T ₀ is a recrystallized annealed material before the second cold rolling step (S14) (that is, a recrystallized annealed material after the first cold rolling step (S13) is completed). T is the thickness of the rolled material (that is, copper alloy foil) when the cold rolling process in the second cold rolling step (S14) is completed.
(Equation 2)
Total processing rate R (%) = {(T ₀ −T) / T ₀ } × 100

<Negative electrode forming step (S20)>
When the copper alloy foil forming step (S10) is completed, a negative electrode active material layer is formed on at least one main surface of the copper alloy foil by, for example, a coil-to-coil continuous line.

  First, for example, a negative electrode active material and a binder are added to a predetermined solvent, and a slurry for forming the negative electrode active material is generated (prepared). Specifically, a predetermined amount (for example, 9.8 parts by mass) of a silicon-based compound as a negative electrode active material and a predetermined amount (for example, 87.0 parts by mass) of graphite (graphite powder), and a predetermined amount as a binder. (For example, 1.5 parts by mass) CBC and a predetermined amount (for example, 1.7 parts by mass) SBR are dispersed in a solvent (for example, water or an organic solvent such as N-methyl-2-pyrrolidone (NMP)). Mix to produce a slurry. In addition, you may add a conductive support agent in a slurry as needed.

  Then, the produced | generated slurry is apply | coated on at least any main surface of copper alloy foil, for example using an applicator. Thereafter, the slurry on the copper alloy foil is dried for a predetermined time under the condition of a predetermined temperature to evaporate the solvent in the slurry, thereby forming a negative electrode active material layer. For example, under conditions of 70 ° C. or higher and 200 ° C. or lower, the copper alloy foil coated with the slurry is held for 1 hour or less (for example, for several minutes to several tens of minutes) and dried, and the negative electrode active material layer is formed on the copper alloy foil. Form.

  And the laminated body of copper alloy foil and a negative electrode active material layer is press-molded, and a negative electrode plate is formed. Thereafter, the negative electrode plate is sheared to form the negative electrode plate into a predetermined shape, and then dried under a predetermined temperature for a predetermined time to form a negative electrode. For example, using a circular cutter with a diameter of 14 mm, the negative electrode plate is sheared to form the negative electrode plate into a disc shape, and then the disc-shaped negative electrode plate is subjected to 6 at 120 ° C. Vacuum drying for a period of time forms a negative electrode.

<Secondary battery forming step (S30)>
When the negative electrode forming step (S20) is completed, for example, a coin-type lithium ion secondary battery (for example, CR2025 type) is formed as the secondary battery. First, a negative electrode, a positive electrode including a positive electrode active material layer, and a separator formed of, for example, a polyethylene porous film are accommodated in a container. For example, in a dry box, the negative electrode active material layer and the positive electrode active material layer face each other, and the negative electrode active material layer and the positive electrode active material layer are placed between the negative electrode active material layer and the positive electrode active material layer. Place it in a coin-shaped container.

Then, an electrolyte is dissolved in an organic solvent to prepare an electrolytic solution. For example, as an organic solvent, 30% by volume of ethylene carbonate (EC), 50% by volume of methyl ethyl carbonate (MEC), and 20% by volume of methyl propionate are mixed to prepare a mixed solvent. Then, for example, 1 mol / liter of LiPF ₆ is dissolved as an electrolyte in the mixed solvent to prepare an electrolytic solution. And electrolyte solution is inject | poured in the container which accommodated the negative electrode, the positive electrode, and the separator, and electrolyte solution is impregnated to a negative electrode active material layer and a positive electrode active material layer, respectively. Thereafter, a gasket is attached and sealed, and the container is sealed to form a secondary battery.

(5) Effects according to the present embodiment According to the present embodiment, the following one or more effects are achieved.

(A) According to the copper alloy foil according to the present embodiment, it contains at least one of a predetermined amount of Sn and a predetermined amount of Ag, the balance is made of Cu and inevitable impurities, and is heated at 200 ° C. for 1 hour. Later tensile strength is 450 N / mm ² or more, and elongation is 2.0% or more. As described above, when the copper alloy foil according to the present embodiment is used as the negative electrode current collector of the secondary battery to form the negative electrode, the heating during the formation of the negative electrode (for example, on the copper alloy foil) Even when the heat treatment for forming the negative electrode active material layer is performed under the severest conditions of 200 ° C. for 1 hour, it has high tensile strength and high elongation. . Therefore, according to this embodiment, for example, a negative electrode current collector formed of a copper alloy foil having a tensile strength of 450 N / mm ² or more and an elongation of 2.0% or more, and a negative electrode active material layer, The negative electrode of the secondary battery provided can be formed.

(B) As described above, the copper alloy foil according to the present embodiment has a predetermined tensile strength and a predetermined elongation after performing a predetermined heat treatment. Thereby, when copper alloy foil is used, for example as a negative electrode collector of a secondary battery, it can control that copper alloy foil breaks by expansion and contraction of a negative electrode active material at the time of charge and discharge of a secondary battery. . That is, the copper alloy foil after performing the predetermined heat treatment has not only the predetermined tensile strength but also the predetermined elongation, and thus cannot be suppressed by the copper alloy foil having the predetermined tensile strength. The breakage of the copper alloy foil can be suppressed.

That is, in a secondary battery in which the copper alloy foil is used as a negative electrode current collector by having a tensile strength of 450 N / mm ² or more after the copper alloy foil is heated at 200 ° C. for 1 hour. Even when the stress generated by the expansion and contraction of the negative electrode active material is applied to the copper alloy foil (negative electrode current collector) as the secondary battery is charged and discharged, the copper alloy foil is deformed by the stress. Or breaking.

  Moreover, in the secondary battery in which the copper alloy foil is used as a negative electrode current collector by having a high elongation of 2.0% or more after the copper alloy foil is heated at 200 ° C. for 1 hour or more, Even when the negative electrode active material expands during charging, the copper alloy foil extends to follow the expansion of the negative electrode active material. For example, even when the negative electrode active material expands when the secondary battery is charged, the negative electrode active material expands until the laminate of the negative electrode, the positive electrode, and the separator accommodated in the container comes into contact with the inner wall of the container. The copper alloy foil extends to follow the expansion of the material. Therefore, it can suppress more that a copper alloy foil fractures.

(C) In the secondary battery in which the copper alloy foil is used as the negative electrode current collector, it is possible to suppress the negative electrode active material from dropping from the copper alloy foil by suppressing the breakage of the copper alloy foil. As a result, the lifetime of the secondary battery can be further extended.

(D) In the case of containing at least one of 0.04% by mass or more and 0.20% by mass or less of Sn or 0.01% by mass or more of Ag in the copper alloy foil and containing both Sn and Ag. Can improve the strength of the copper alloy foil in the state of H material by making the total content of Sn and Ag 0.20% by mass or less. For example, the tensile strength of the copper alloy foil in the state of H material can be 450 N / mm ² or more. Moreover, it can suppress that the electroconductivity of copper alloy foil falls. For example, the conductivity of the copper alloy foil can be 80% IACS or higher.

(E) Moreover, Sn is contained in the copper alloy foil by containing at least one of 0.04% by mass or more and 0.20% by mass or less of Sn and 0.01% by mass or more of Ag in the copper alloy foil. At least one of Ag can be dissolved. Thereby, the heat resistance of copper alloy foil can be improved. Therefore, even if the predetermined heat treatment is performed on the copper alloy foil, the copper alloy foil is hardly softened. For example, the copper alloy foil is less likely to be softened by heating when forming a negative electrode by forming a negative electrode active material layer on the copper alloy foil. Thereby, even after performing the predetermined heat treatment, the copper alloy foil has a predetermined tensile strength. For example, the tensile strength of the copper alloy foil after heating for 1 hour under the condition of 200 ° C. can be 450 N / mm ² or more. Moreover, the ductility of copper alloy foil can be improved by performing predetermined heat processing with respect to copper alloy foil. That is, the elongation of the copper alloy foil after performing the predetermined heat treatment can be made higher than the elongation of the copper alloy foil in the H material state. For example, the elongation after heating for 1 hour at 200 ° C. can be 2.0% or more. As a result, the effects (a) to (c) can be obtained.

(F) By making content of Ag in copper alloy foil into 0.10 mass% or less, it can suppress that the manufacturing cost of copper alloy foil becomes high.

(G) By using oxygen-free copper as a base material, the amount of oxides such as SnO and AgO produced in the copper alloy foil can be reduced. Therefore, the heat resistance of the copper alloy foil can be further improved. As a result, the effects (a) to (c) can be obtained more. In addition, by reducing the amount of Sn and Ag that react with O in the copper alloy foil, the amount of Sn and Ag dissolved in the copper alloy foil can be increased without increasing the content of Sn and Ag. it can. Therefore, the effects (a) to (c) and (e) can be further obtained.

(H) In the second cold rolling step (S14), cold rolling with a single workability of 60% or less is performed without interposing heat treatment so that the total workability is 95% or more. The cold rolling process is performed continuously several times. Thereby, the anisotropy of the mechanical characteristic of copper alloy foil can be reduced. Therefore, the ductility of the copper alloy foil in the H material state can be improved. In addition, the ductility of the copper alloy foil after the predetermined heat treatment is improved from the ductility of the copper alloy foil in the H material state while suppressing the decrease in the tensile strength of the copper alloy foil after the predetermined heat treatment. Can be made. For example, the tensile strength of the copper alloy foil in the state of H material is set to 450 N / mm ² or more, and the tensile strength of the copper alloy foil after heating for 1 hour at 200 ° C. is set to 450 N / mm ² or more. However, the elongation of the copper alloy foil can be made 2.0% or more.

(I) It can suppress more that the manufacturing cost of copper alloy foil becomes high by making the total work degree of the cold rolling performed by a 2nd cold rolling process (S14) 99.5% or less.

(J) As described above, the copper alloy foil according to the present embodiment is effective when used as a negative electrode current collector included in a negative electrode of a secondary battery. Moreover, the copper alloy foil according to the present embodiment is effective when a material capable of increasing the charge / discharge capacity of the secondary battery is used as the negative electrode active material. In other words, it is effective when a large-capacity negative electrode active material having a large expansion and contraction due to insertion and extraction of Li ions, which are electrolytes contained in the electrolyte solution of the secondary battery, is used as the negative electrode active material. Specifically, this is effective when a negative electrode active material having a theoretical capacity larger than that of the carbon material is used. For example, this is particularly effective when a material containing a metal that can be alloyed with Li, such as Si or Sn, is used as the negative electrode active material.

(K) The copper alloy foil according to the present embodiment is particularly effective when a negative electrode active material layer having a large theoretical capacity and a high ratio of the negative electrode active material that expands and contracts greatly when the secondary battery is charged is formed. It is. According to the copper alloy foil according to the present embodiment, the negative electrode active material expands at the time of charging the secondary battery as described above, so that even when a larger stress load is applied, the breakage can be suppressed. .

(L) The copper alloy foil according to the present embodiment is particularly effective when used for a small and lightweight secondary battery. That is, it is particularly effective when it is necessary to reduce the thickness of the copper alloy foil as the negative electrode current collector. The copper alloy foil according to the present embodiment has a high tensile strength even if the thickness is reduced. For example, even if the thickness of the copper alloy foil is 20 μm or less, it has a tensile strength of 450 N / mm ² or more in the state of H material. Therefore, even when a high-tension load is applied to the copper alloy foil when applying the slurry for forming the negative electrode active material layer on the copper alloy foil in the negative electrode forming step (S20), the foil of the copper alloy foil The occurrence of cutting can be suppressed. Moreover, the copper alloy foil according to the present embodiment has high heat resistance even when the thickness is reduced. Therefore, the effects (a) to (c) and (e) can be obtained.

Hereafter, the conventional copper foil and copper alloy foil are demonstrated for reference. When forming a negative electrode using copper foil in copper foil formed from tough pitch copper or oxygen-free copper as a base material (that is, pure copper foil made of Cu and inevitable impurities without containing other elements in the base material) Due to this heating, recrystallization may occur in the copper foil, and the copper foil may be softened. For example, the tensile strength of the copper foil after heating for 1 hour at 200 ° C. may decrease to around 200 N / mm ² . In the secondary battery including the softened copper foil, the copper foil may be deformed or broken due to the stress generated by the expansion and contraction of the negative electrode active material as the secondary battery is charged and discharged. is there.

Further, conventionally, a copper alloy foil containing 0.05 mass% or more and 0.22 mass% or less of Sn and 0.1 mass% or less of Ag, with the balance being Cu and inevitable impurities, Ag, chromium ( 0.01% by mass in total of at least one of Cr), Fe, indium (In), Ni, P, Si, Sn, tellurium (Te), titanium (Ti), zinc (Zn), and zirconium (Zr) There exists copper alloy foil which improved heat resistance, such as copper alloy foil which contains 0.50 mass% or less and the remainder consists of Cu and an unavoidable impurity. These copper alloy foils have a tensile strength in the state of H material of 450 N / mm ² or more, and a tensile strength after heating for 30 minutes at 300 ° C. is 400 N / mm ² or more. However, these copper alloy foils are formed by a general rolled copper foil manufacturing method (rolling method). It is known that the ductility of the formed copper alloy foil is reduced by a general rolling method. For example, the elongation of the copper alloy foil after performing a predetermined heat treatment may be about 1%. As described above, the conventional copper alloy foil may not have both high tensile strength and high elongation after a predetermined heat treatment. Therefore, when such a copper alloy foil is used for a negative electrode current collector of a secondary battery, the negative electrode active material expands when the secondary battery is charged, and the copper alloy foil may break. There is.

On the other hand, according to the present embodiment, the tensile strength after heating for 1 hour under the condition of 200 ° C. containing at least one of a predetermined amount of Sn and a predetermined amount of Ag, the balance being Cu and inevitable impurities. Is 450 N / mm ² or more, and the elongation is 2.0% or more. For this reason, the above-mentioned subject can be solved effectively.

(Other embodiments of the present invention)
As mentioned above, although one Embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change suitably.

  In the above-described embodiment, the pretreatment is performed in the hot rolling step (S12). However, the pretreatment may be performed as necessary. That is, the preprocessing may be omitted.

  In the above-described embodiment, the first cold rolling step (S13) and the second cold rolling step (S14) are performed, but the present invention is not limited to this. For example, the first cold rolling step (S13) may be performed as necessary and may be omitted.

  In the above-described embodiment, a plurality of cold rolling processes are continuously performed in the second cold rolling step (S14), but the present invention is not limited to this. That is, in the second cold rolling step (S14), a copper alloy foil having a predetermined thickness may be formed by performing a cold rolling process with a predetermined degree of processing once.

  In the above embodiment, the negative electrode is accommodated and held in the upper container 11A, and the positive electrode is accommodated and held in the lower container 11B. However, the present invention is not limited to this. For example, the upper container 11A may contain and hold the positive electrode, and the lower container 11B may contain and hold the negative electrode.

  In the above-described embodiment, a coin-type lithium ion secondary battery has been described as an example of the secondary battery, but the present invention is not limited to this. For example, as a container included in the secondary battery, a cylindrical or square container may be used, and a wound body in which a laminate of a negative electrode, a separator, and a positive electrode is wound may be accommodated in the container. .

  Next, examples of the present invention will be described, but the present invention is not limited thereto.

<Preparation of sample>
The copper alloy foil which is each sample of samples 1-39 was produced, respectively.

(Sample 1)
In sample 1, oxygen-free copper was used as a base material. Then, oxygen-free copper was heated to a predetermined temperature (for example, 1100 ° C.) and melted in a nitrogen atmosphere using a high-frequency melting furnace to melt (generate) a molten copper. Subsequently, a predetermined amount of Sn was added and mixed in the copper melt under a nitrogen atmosphere while maintaining the heating of the copper melt in the high-frequency melting furnace, thereby melting the copper alloy melt. Thereafter, a molten copper alloy was poured into a predetermined mold and cooled to cast an ingot having a predetermined shape. That is, an ingot containing 0.04% by mass of Sn and the balance of Cu and inevitable impurities was produced. The content (concentration) of Sn in the ingot is a result of analyzing the concentration of Sn in the ingot by inductively coupled plasma emission spectroscopy (ICP-AES).

  Next, after heating the ingot for 3 hours under the condition of a predetermined temperature (for example, 900 ° C.), hot rolling with a work degree of 95% is performed before the temperature of the ingot is lowered, and hot rolling with a thickness of 12 mm is performed. A material was prepared. After the hot rolled material was cooled to a predetermined temperature (for example, about room temperature), a first cold rolling process was performed on the hot rolled material. As the first cold rolling treatment, cold rolling in which the degree of workability of one time (one pass) is 10 to 20% and the total degree of workability is 60 to 75% by continuously repeating a predetermined number of times. The treatment and the recrystallization annealing treatment were alternately repeated a predetermined number of times. Thereby, a recrystallized annealing material having a thickness of 1 mm was produced.

  Thereafter, cold rolling in which the degree of work at one time is 60% or less is continuously performed a predetermined number of times (14 times) on the recrystallized annealed material until the total degree of work reaches 99.0%. Cold rolling treatment was performed. Specifically, as the second cold rolling process, a cold rolling process with a rolling pass schedule shown in A of Table 2 below was performed. As a result, a copper alloy foil having a thickness of 0.010 mm (10 μm) was produced, and this was used as Sample 1.

(Samples 2 to 39)
In Samples 2 to 39, the Sn content and the Ag content in the copper alloy foil were as shown in Table 1 below, respectively. The content of Sn and the content of Ag in the copper alloy foil were changed by adjusting the addition amounts of Sn and Ag added to the molten copper. The sample 26 is a copper foil (pure copper foil) made of Cu and inevitable impurities. That is, in the sample 26, an ingot was formed without adding Sn and Ag into the molten copper. In Samples 2 to 39, the rolling pass schedule was as shown in Tables 1 and 2, respectively. Otherwise, a copper alloy foil was prepared in the same manner as Sample 1. These were designated as samples 2 to 39, respectively.

<Evaluation of characteristics of copper alloy foil>
About the copper alloy foil of samples 1-39, the characteristic of the copper alloy foil was performed, respectively. Specifically, electrical conductivity, tensile strength, elongation, and heat resistance were evaluated as characteristics of the copper alloy foil.

(Measurement of conductivity)
The electrical conductivity of each copper alloy foil of Samples 1 to 39 was measured, and the electrical conductivity was evaluated. The conductivity was measured based on a conductivity measuring method based on JIS H0505. The results are shown in Table 1 above.

(Measurement of tensile strength and elongation before heat treatment)
The tensile strength and elongation of each copper alloy foil of Samples 1 to 39 were measured. That is, the tensile strength and elongation of each copper alloy foil of samples 1 to 39 in the state of H material were measured. The tensile strength was measured according to ASTM International E-345. Specifically, test pieces having a predetermined size (width: 12.5 mm, length: 230 mm) were prepared from the copper alloy foils (copper foils) of Samples 1 to 39, respectively. And the distance between the grips which hold | maintain the test piece with which the apparatus which measures tensile strength is set to 125 mm, the tensile speed was 5 mm / min, and the tensile stress was added to the rolling direction of each test piece about each test piece. Each tensile strength was measured. Moreover, the measurement of elongation was performed based on IPC-TM-650 2.4.18. Specifically, test pieces having a predetermined size (width: 12.5 mm, length: 230 mm) were prepared from the copper alloy foils (copper foils) of Samples 1 to 39, respectively. Subsequently, the test piece is held between grips (chucks) included in the apparatus for measuring elongation. Then, using the load cell with which the apparatus which measures elongation is used, the tensile speed was 5 mm / min, and each test piece was extended in the direction parallel to the rolling direction until fracture occurred in each test piece. And the movement distance of the load cell when the fracture | rupture occurred in each test piece was detected. And the elongation of each test piece was calculated from the following (Equation 3). The measurement results of tensile strength and elongation are shown in Table 1 as tensile strength and elongation before heat treatment, respectively.
(Equation 3)
Elongation (%) = (distance traveled by load cell before break / distance between chucks) × 100

(Evaluation of heat resistance)
Evaluation of heat resistance was performed by measuring the tensile strength after heating each copper alloy foil (copper foil) of Samples 1 to 39 at 200 ° C. for 1 hour. In addition, the measuring method of tensile strength is the same as the measuring method of the tensile strength of the copper alloy foil before the above-mentioned heat processing. Table 1 shows the measurement results of the tensile strength after performing the predetermined heat treatment. Note that the smaller the difference between the tensile strength before the heat treatment (that is, in the state of the H material) and the tensile strength after the heat treatment, the better the heat resistance.

(Evaluation of ductility)
The ductility was evaluated by measuring the elongation after heating the copper alloy foils (copper foils) of Samples 1 to 39 under the condition of 200 ° C. for 1 hour, respectively. In addition, the measuring method of elongation is the same as the measuring method of the elongation of the copper alloy foil before the above-mentioned heat treatment. Table 1 shows the measurement results of the elongation after performing the predetermined heat treatment. A larger difference between the elongation before the heat treatment and the elongation after the heat treatment indicates that the ductility of the copper alloy foil (copper foil) is improved.

<Evaluation of secondary battery characteristics>
The characteristics of the secondary batteries formed using the copper alloy foils of Samples 1 to 39 were evaluated. Specifically, as the characteristics of the secondary battery, the area change rate of the negative electrode, the presence / absence of a broken portion of the negative electrode, and the presence / absence of a dropped portion of the negative electrode active material were evaluated.

(Preparation of negative electrode)
First, a negative electrode active material layer was formed on any main surface of each of the copper alloy foils (copper foils) of Samples 1 to 39 to produce negative electrodes. Specifically, 45 parts by mass of flaky graphite powder as a negative electrode active material, 5 parts by mass of silicon monoxide (SiO), 2 parts by mass of SBR as a binder, and 20 thickener aqueous solutions. The slurry for the negative electrode active material layer (paste) was produced by kneading and dispersing the mass part. The thickener aqueous solution was produced by dissolving 99 parts by mass of water with respect to 1 part by mass of CMC as a thickener. Subsequently, on the main surface (one surface) of each of the copper alloy foils (copper foils) of Samples 1 to 39, the generated slurry for the negative electrode active material layer has a thickness of 100 μm by the doctor blade method. It was applied as follows. Thereafter, each of the copper alloy foils (copper foils) of Samples 1 to 39 coated with the slurry for the negative electrode active material layer was heated at 200 ° C. for 1 hour and dried. Thereby, a negative electrode active material layer having a thickness of 100 μm was formed on each copper alloy foil (copper foil) of Samples 1 to 39. And the thickness of the negative electrode active material layer was adjusted to 50 micrometers by pressurizing a negative electrode active material layer. Then, the negative electrode (negative electrode plate) of the predetermined shape was produced by performing a punching process with respect to the laminated body of copper alloy foil and a negative electrode active material layer.

(Production of secondary battery)
A positive electrode plate (positive electrode) used for a secondary battery was produced. Specifically, 50 parts by mass of LiCoO ₂ powder as a positive electrode active material, 1 part by mass of acetylene black as a conductive additive, and 5 parts by mass of PVDF as a binder are contained in water (solvent). The slurry for the positive electrode active material layer (paste) was produced. Subsequently, the slurry for the positive electrode active material layer generated is 100 μm in thickness by a doctor blade method on any main surface (one side) of the aluminum foil having a thickness of 20 μm as the positive electrode current collector. It was applied as follows. Thereafter, the aluminum foil coated with the slurry for the positive electrode active material layer was heated at 120 ° C. for 1 hour and dried. As a result, a positive electrode active material layer having a thickness of 100 μm was formed on the aluminum foil. And the thickness of the positive electrode active material layer was adjusted to 50 μm by pressurizing the positive electrode active material layer. Thereafter, the laminate of the aluminum foil and the positive electrode active material layer was punched to produce a positive electrode (positive electrode plate) having a predetermined shape.

Using each negative electrode using each copper alloy foil (copper foil) of Samples 1 to 39, a positive electrode, a separator, and an electrolytic solution, a coin cell type lithium ion secondary battery was manufactured. That is, a polypropylene having a thickness of 20 μm between the negative electrode active material layer and the positive electrode active material layer, arranged so that the negative electrode active material layer included in each negative electrode and the positive electrode active material layer included in the positive electrode face each other. A separator made of a resin porous film was sandwiched between the negative electrode, the positive electrode, and the separator. And the laminated body of a negative electrode, a positive electrode, and a separator was accommodated in the coin-shaped container (cell), and the positive electrode and the negative electrode were each electrically connected to the terminal inside a cell. Thereafter, 1 mol / liter of LiPF ₆ as an electrolyte was added to a mixed solvent formed by mixing 30% by volume of EC, 50% by volume of MEC, and 20% by volume of methyl propionate, and an additive. After injecting an electrolyte solution in which 1% by mass of VC was dissolved into the cell, the cell was sealed to produce a secondary battery.

(Rate change rate of negative electrode)
About each secondary battery formed using each copper alloy foil (copper foil) of samples 1-39, the deformation | transformation of the negative electrode after charging / discharging a secondary battery was evaluated. Specifically, the rate of change in the area of the negative electrode after alternately charging and discharging a predetermined number of times (100 times) was measured. The lower the value of the area change rate of the negative electrode, the lower the deformation of the negative electrode.

(Evaluation of presence of breakage and negative electrode active material)
About each secondary battery formed using each copper alloy foil (copper foil) of Samples 1 to 39, after charging / discharging the secondary battery, the location where the copper alloy foil is broken, the negative electrode active material falling off The presence or absence of occurrence of the spots was confirmed visually.

<Evaluation results>
From Samples 1 to 25, a copper alloy foil having a predetermined heat resistance and having a predetermined elongation after a predetermined heat treatment is used as a negative electrode current collector of a secondary battery. It was confirmed that the copper alloy foil can be prevented from being deformed or broken by charging / discharging. For example, a copper alloy foil having a tensile strength of 450 N / mm ² or more after heating for 1 hour at 200 ° C. and an elongation of 2.0% or more was used as the negative electrode current collector. In the secondary battery, it was confirmed that deformation and breakage of the copper alloy foil were suppressed even when the secondary battery was charged and discharged. For example, it was confirmed that the area change rate of the negative electrode after the charge / discharge cycle could be 15% or less. Moreover, it confirmed that the negative electrode active material contained in a negative electrode active material layer can be suppressed from dropping from copper alloy foil by suppressing a deformation | transformation and a fracture | rupture of copper alloy foil.

  That is, the copper alloy foil after performing the predetermined heat treatment has a predetermined tensile strength, so that when the secondary battery is charged / discharged, the negative electrode active material expands and contracts, thereby causing a stress It was confirmed that the alloy foil can be prevented from being deformed or broken. In addition, since the copper alloy foil after the predetermined heat treatment has a predetermined elongation, even when the negative electrode active material expands and contracts when the secondary battery is charged, the negative electrode active material expands. It was confirmed that the copper alloy foil stretched to follow the shrinkage. Therefore, it was confirmed that the copper alloy foil can be further prevented from breaking.

In addition, from Samples 1 to 25, when 0.04% by mass or more and 0.20% by mass or less of Sn, 0.01% by mass or more of Ag is included, and both Sn and Ag are included, Sn and It was confirmed that the copper alloy foil having a total Ag content of 0.20% by mass or less has a high tensile strength of 450 N / mm ² or more in the state of the H material. In addition, each of the copper alloy foils of Samples 1 to 25 has a high heat resistance because the decrease in tensile strength is suppressed even after heating for 1 hour at 200 ° C. confirmed. That is, it was confirmed that the copper alloy foils of Samples 1 to 25 each had a high strength of 450 N / mm ² or more even after heating for 1 hour under the condition of 200 ° C. Moreover, it was confirmed that the copper alloy foils of Samples 1 to 25 each had higher elongation after heating for 1 hour under the condition of 200 ° C. than the elongation of the H material. Moreover, it was confirmed that each of the copper alloy foils of Samples 1 to 25 can increase the elongation of the copper alloy foil to 2.0% or more after heating for 1 hour under the condition of 200 ° C.

  In addition, it was confirmed that the copper alloy foils of Samples 1 to 25 each had a reduced conductivity and the conductivity was 80% IACS or more.

Further, from the samples 1 to 25, as the second cold rolling process, cold rolling in which the degree of work at one time is 60% or less is continuously performed a predetermined number of times so that the total degree of work becomes 95% or more. Thus, even after heating for 1 hour at 200 ° C., it was confirmed that it had a high tensile strength of 450 N / mm ² or more and a high elongation of 2.0% or more.

  From Samples 9 to 12, it was confirmed that the decrease in conductivity of the copper alloy foil can be further suppressed when the content of Sn in the copper alloy foil is 0.12% by mass. For example, it was confirmed that the conductivity of the copper alloy foil could be 85% IACS or higher.

It was confirmed from Samples 15 to 20 that the strength of the copper alloy foil can be further improved when the Ag content in the copper alloy foil is 0.03% by mass or more. That is, it was confirmed that the tensile strength of the copper alloy foil in the state of the H material can be further increased. For example, it was confirmed that the tensile strength of the copper alloy foil could be 480 N / mm ² or more. Moreover, it confirmed that the tensile strength of the copper alloy foil after heating for 1 hour on 200 degreeC conditions became 480 N / mm < ² > or more. Therefore, even when the negative electrode active material expands and contracts when the secondary battery is charged and discharged, even when a greater stress is generated, it is confirmed that the copper alloy foil can be further prevented from being deformed or broken. did. For example, it was confirmed that the area change rate of the negative electrode can be further reduced.

  From Samples 1 to 3, Samples 5 to 8, Samples 10 to 13, Samples 16 to 18, Samples 20 to 23, and Sample 25, the total degree of work R in the second cold rolling process is 97% or more, It was confirmed that the elongation of the copper alloy foil after the predetermined heat treatment can be further improved. For example, it was confirmed that the elongation of the copper alloy foil after heating for 1 hour at 200 ° C. could be 2.5% or more.

From the sample 26, it was confirmed that pure copper foil made of Cu and inevitable impurities has low heat resistance and softens when subjected to predetermined heat treatment. Specifically, the pure copper foil has a tensile strength in the state of H material of 450 N / mm ² or more, but the tensile strength after heating for 1 hour at 200 ° C. decreases to 198 N / mm ^2. I confirmed that it would. Therefore, in the secondary battery formed using the pure copper foil as the negative electrode current collector, it was confirmed that the deformation of the pure copper foil becomes large when the secondary battery is charged. For example, it was confirmed that the area change rate of the negative electrode after the charge / discharge cycle was 35% and exceeded 15%. Moreover, in the negative electrode provided with the softened pure copper foil, fracture | rupture generate | occur | produced in the pure copper foil in the case of charging / discharging of a secondary battery, As a result, it confirmed that the negative electrode active material fell off on pure copper foil.

From comparison between Sample 1 and Sample 27, it was confirmed that the desired heat resistance could not be obtained when the Sn content was less than 0.04 mass%. Specifically, the tensile strength in the state of H material is 477 N / mm ² , but the tensile strength after heating for 1 hour under the condition of 200 ° C. decreases to 204 N / mm ^2. confirmed.

  From the comparison between Samples 11 and 12 and Sample 28, when only Sn is contained in the copper alloy foil, if the Sn content exceeds 0.2% by mass, the heat resistance can be further improved. It was confirmed that the conductivity of the copper alloy foil was lowered. For example, it was confirmed that the conductivity of the copper alloy foil would be less than 80% IACS.

  From the comparison between Samples 13 and 14 and Sample 29, when only Ag is contained in the copper alloy foil, the desired heat resistance cannot be obtained when the Ag content is less than 0.01% by mass. It was confirmed.

  From the comparison between Sample 25 and Sample 30, when Sn and Ag are contained in the copper alloy foil, if the total content of Sn and Ag exceeds 0.20% by mass, the respective contents of Sn and Ag are predetermined. Even within the range, it was confirmed that the conductivity of the copper alloy foil was lowered. For example, it was confirmed that the conductivity of the copper alloy foil would be less than 80% IACS.

  From the comparison between the samples 1 to 25 and the samples 31 to 36, even when the copper alloy foil contains at least one of a predetermined amount of Sn and a predetermined amount of Ag, the cold rolling performed in the second cold rolling process is performed. If the total degree of work is less than 95%, the elongation of the copper alloy foil after performing the predetermined heat treatment is less than 2.0% even if the degree of work of one cold rolling is 60% or less. I confirmed that it would become. Therefore, in a secondary battery using such a copper alloy foil, when the negative electrode active material expands during charging of the secondary battery, the copper alloy foil cannot follow the expansion of the negative electrode active material, and the copper It was confirmed that the alloy foil would break.

  From the comparison between Samples 1 to 26 and Samples 37 to 39, it is a copper alloy foil containing at least one of a predetermined amount of Sn and a predetermined amount of Ag, and the total workability is 95% in the second cold rolling process. Even when the cold rolling is performed a predetermined number of times as described above, the copper alloy foil after the predetermined heat treatment is performed if the cold rolling exceeding 60% is performed once. It has been confirmed that the elongation of is less than 2.0%.

<Preferred embodiment>
Hereinafter, preferred embodiments of the present invention will be additionally described.

[Appendix 1]
According to one aspect of the invention,
When 0.04 mass% or more and 0.20 mass% or less of tin and 0.01 mass% or more of silver are contained, and both tin and silver are contained, the total content of tin and silver is 0 20% by mass or less, the balance being made of copper and inevitable impurities,
A copper alloy foil having a tensile strength of 450 N / mm ² or more and an elongation of 2.0% or more after heating for 1 hour at 200 ° C. is provided.

[Appendix 2]
The copper alloy foil of appendix 1, preferably,
The silver content is 0.10% by mass or less.

[Appendix 3]
Appendix 1 or 2 copper alloy foil, preferably,
At least one of tin and silver is dissolved.

[Appendix 4]
The copper alloy foil according to any one of appendices 1 to 3, preferably,
Oxygen-free copper is used as a base material.

[Appendix 5]
The copper alloy foil according to any one of appendices 1 to 4, preferably,
Conductivity is 80% IACS or higher.

[Appendix 6]
The copper alloy foil according to any one of appendices 1 to 4, preferably,
The tin content is 0.04 mass% or more and 0.12 mass% or less,
Conductivity is 85% IACS or higher.

[Appendix 7]
The copper alloy foil according to any one of appendices 1 to 6, preferably
The silver content is 0.03% by mass or more.

[Appendix 8]
The copper alloy foil of appendix 7, preferably,
The tensile strength after heating for 1 hour under the condition of 200 ° C. is 480 N / mm ² or more.

[Appendix 9]
The copper alloy foil according to any one of appendices 1 to 8, preferably,
The elongation after heating for 1 hour at 200 ° C. is 2.5% or more.

[Appendix 10]
According to another aspect of the invention,
When 0.04 mass% or more and 0.20 mass% or less of tin and 0.01 mass% or more of silver are contained, and both tin and silver are contained, the total content of tin and silver is 0 A casting step of casting an ingot that is 20% by mass or less and the balance is made of copper and inevitable impurities;
Performing a predetermined hot rolling on the ingot, forming a hot rolled material,
A first cold rolling step in which cold rolling and annealing treatment are alternately repeated a predetermined number of times on the hot rolled material to form an annealed material;
A second cold rolling step in which cold rolling with a workability of 60% or less for the annealed material is continuously performed a predetermined number of times so that the total workability becomes 95% or more; A method for producing a copper alloy foil is provided.

[Appendix 11]
The method for producing a copper alloy foil according to appendix 10, preferably,
In the second cold rolling step, cold rolling is performed a predetermined number of times so that the total workability becomes 97% or more.

[Appendix 12]
A method for producing a copper alloy foil according to appendix 10 or 11, preferably,
In the second cold rolling step, cold rolling is performed a predetermined number of times so that the total workability becomes 99.5% or less.

[Appendix 13]
According to another aspect of the invention,
When 0.04 mass% or more and 0.20 mass% or less of tin and 0.01 mass% or more of silver are contained, and both tin and silver are contained, the total content of tin and silver is 0 A negative electrode current collector formed of a copper alloy foil of 20 mass% or less, the balance being copper and inevitable impurities, a tensile strength of 450 N / mm ² or more, and an elongation of 2.0% or more; ,
There is provided a negative electrode for a secondary battery, comprising a negative electrode active material layer provided on at least one main surface of the negative electrode current collector and having a negative electrode active material.

[Appendix 14]
When 0.04 mass% or more and 0.20 mass% or less of tin and 0.01 mass% or more of silver are contained, and both tin and silver are contained, the total content of tin and silver is 0 A negative electrode current collector formed of a copper alloy foil that is 20 mass% or less, the balance is made of copper and inevitable impurities, the tensile strength is 450 N / mm ² or more, and the elongation is 2.0% or more, And a negative electrode comprising a negative electrode active material layer provided on at least one main surface of the negative electrode current collector and having a negative electrode active material;
A positive electrode;
A separator for electrically insulating the negative electrode and the positive electrode;
A secondary battery is provided that includes the negative electrode, the positive electrode, and the separator, and a container into which an electrolyte is injected.

DESCRIPTION OF SYMBOLS 10 Secondary battery 13 Negative electrode 13A Copper alloy foil 13B Negative electrode active material layer

Claims (6)

Contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more and 0.10% by mass or less of silver, and in the case of containing both tin and silver, tin and silver The total content is 0.20% by mass or less, and the balance consists of copper and inevitable impurities,
Tensile strength after heating for 1 hour at 200 ° C. is 450 N / mm ² or more, and elongation is 2.0% or more.
Copper alloy foil for a negative electrode current collector of a secondary battery . The copper alloy foil for a negative electrode current collector of a secondary battery according to claim 1, wherein the conductivity is 80% IACS or more. A method for producing a copper alloy foil for a negative electrode current collector of a secondary battery having a tensile strength of 450 N / mm ² or more after heating for 1 hour at 200 ° C. and an elongation of 2.0% or more. And
Contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more and 0.10% by mass or less of silver, and in the case of containing both tin and silver, tin and silver A casting step of casting an ingot having a total content of 0.20% by mass or less and the balance of copper and inevitable impurities;
Subjected to hot rolling with respect to the ingot, a hot rolling step of forming a hot-rolled material,
Performing a cold rolling treatment and an annealing treatment on the hot-rolled material to form an annealed material;
A second cold rolling step in which cold rolling with a workability of 60% or less for the annealed material is continuously performed a predetermined number of times so that the total workability becomes 95% or more; Have
A method for producing a copper alloy foil for a negative electrode current collector of a secondary battery . 4. The copper alloy foil for a negative electrode current collector of a secondary battery according to claim 3 , wherein in the second cold rolling step, cold rolling is performed a predetermined number of times so that the total workability becomes 99.5% or less. Production method. Contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more and 0.10% by mass or less of silver, and in the case of containing both tin and silver, tin and silver The total content is 0.20% by mass or less, the balance is made of copper and inevitable impurities, the tensile strength after heating for 1 hour at 200 ° C. is 450 N / mm ² or more, and the elongation is 2 A negative electrode current collector formed of a copper alloy foil of 0.0% or more;
A negative electrode for a secondary battery, comprising: a negative electrode active material layer having a negative electrode active material provided on at least one main surface of the negative electrode current collector. Contains at least one of 0.04% by mass or more and 0.20% by mass or less of tin, 0.01% by mass or more and 0.10% by mass or less of silver, and in the case of containing both tin and silver, tin and silver The total content is 0.20% by mass or less, the balance is made of copper and inevitable impurities, the tensile strength after heating for 1 hour at 200 ° C. is 450 N / mm ² or more, and the elongation is 2 A negative electrode current collector formed of a copper alloy foil of 0.0% or more, and a negative electrode comprising a negative electrode active material layer having a negative electrode active material provided on at least one main surface of the negative electrode current collector; ,
A positive electrode;
A separator for electrically insulating the negative electrode and the positive electrode;
A secondary battery comprising: the negative electrode, the positive electrode, the separator, and a container into which an electrolyte is injected.

Images