JP5918623B2 - Method for producing negative electrode current collector copper foil for lithium ion secondary battery, method for producing negative electrode for lithium ion secondary battery, and method for producing lithium ion secondary battery - Google Patents

Description

  The present invention relates to a negative electrode current collector copper foil for a lithium ion secondary battery, a negative electrode comprising such a negative electrode current collector copper foil for a lithium ion secondary battery, and a lithium ion secondary battery.

Lithium ion secondary batteries are used, for example, in communication devices such as mobile phones, notebook computers, power tools, hybrid cars, electric vehicles, large-scale power storage facilities, and the like. Lithium ion secondary batteries are mainly composed of a positive electrode, a negative electrode, a separator that insulates the positive electrode from the negative electrode, and an electrolyte that enables lithium (Li ⁺ ) ions to move between the positive electrode and the negative electrode.

  A negative electrode for a lithium ion secondary battery includes, for example, a negative electrode current collector and a negative electrode active material layer bound to the negative electrode current collector. For example, a copper foil is used as the negative electrode current collector. In the negative electrode active material layer, in addition to a negative electrode active material such as carbon and graphite, conductive assistants such as acetylene black, polyvinylidene fluoride (PVDF), styrene / butadiene rubber (SBR), polyimide (PI), and the like are bonded. Contains a dressing.

  As described above, carbon-based materials such as carbon have been mainly used as the negative electrode active material. However, in a lithium ion secondary battery using a carbon-based material, the charge / discharge capacity almost reaches the theoretical value of 372 mAh / g, and it is difficult to increase the capacity beyond this. Therefore, for the purpose of further increasing the capacity, practical application of a negative electrode active material mainly using tin (Sn) with a theoretical value of charge / discharge capacity of 990 mAh / g, silicon (Si) with 4200 mAh / g, etc. has been studied. Yes.

  These high-capacity negative electrode active materials mainly composed of Sn, Si, and the like are alloyed with lithium (Li) during charging and expand in volume, and contract during discharge. For example, the volume change rate of Si is 400%, which is significantly larger than that of conventional graphite of 110%. For this reason, a big stress generate | occur | produces with charging / discharging in the negative electrode current collection copper foil holding the negative electrode active material layer containing these. As a result, the negative electrode active material layer peels off from the negative electrode current collector copper foil, and the electrical connection between the negative electrode current collector copper foil and the negative electrode active material may deteriorate, leading to a decrease in battery capacity. Or a negative electrode current collection copper foil will extend | stretch, and there exists a possibility that an internal short circuit will be raise | generated.

  Therefore, for example, Patent Documents 1 and 2 employ a technique of relaxing stress applied to the negative electrode current collector copper foil using a high elastic modulus material as a binder. That is, Patent Document 1 proposes a negative electrode for a lithium secondary battery using an alloy powder containing Sn as active material particles and using a thermoplastic resin having an elastic modulus of 3.0 GPa or more as a binder. Yes. Thereby, when the active material particles expand / contract due to charge / discharge, the deformation of the entire negative electrode active material layer can be reduced.

  Further, in Patent Document 2, the negative electrode active material is a powder material made of Si or Si alloy, and a negative electrode that has been subjected to heat treatment by applying a mixture slurry containing a polyimide resin as a binder onto a current collector and drying the mixture. Proposed. Note that, as disclosed in Patent Document 2, a high-modulus binder such as polyimide resin is often subjected to heat treatment at around 400 ° C. for about 10 hours. Thereby, for example, imidization of a polyimide resin is promoted.

On the other hand, for example, Patent Document 3 proposes a copper foil for a negative electrode current collector in which a hard cobalt plating layer or a cobalt-nickel alloy plating layer is formed on the surface. Thereby, even after the heat treatment with respect to the binder, a decrease in tensile strength due to softening of the copper foil can be suppressed, and the charge / discharge cycle can be improved.

JP 2007-149604 A JP 2005-317309 A Japanese Patent No. 4438541

  However, as in Patent Documents 1 and 2, just using a binder with a high elastic modulus is not sufficient for the expansion and contraction of the negative electrode active material. This is because, as described above, the copper foil as the negative electrode current collector is softened by the heat treatment on the binder and is easily plastically deformed. When plastic deformation occurs, the negative electrode active material layer is peeled off from the negative electrode current collector due to repeated charge / discharge, and the charge / discharge cycle characteristics are deteriorated. Thereby, the electrical connection between the negative electrode current collector and the negative electrode active material is deteriorated, and the battery capacity may be reduced. In this case, the life of the lithium ion secondary battery is shortened.

  In Patent Document 3, although the tensile strength is improved by a hard cobalt plating layer or the like, plastic deformation occurs when the copper foil cannot withstand the volume expansion stress of the negative electrode active material layer. In addition, it is not certain what kind of effect the characteristics of the battery have by providing a cobalt plating layer or a cobalt-nickel alloy plating layer on the surface of the copper foil.

  An object of the present invention is to provide a negative electrode current collector copper foil for a lithium ion secondary battery excellent in charge / discharge cycle characteristics, a negative electrode including the negative electrode current collector copper foil for the lithium ion secondary battery, and a lithium ion secondary battery. That is.

According to a first aspect of the invention,
A negative electrode current collector copper foil for a lithium ion secondary battery in which a negative electrode active material layer is formed on at least one side and incorporated in a negative electrode for a lithium ion secondary battery,
When incorporated in the negative electrode for lithium ion secondary battery,
The negative electrode active material layer is formed on at least one side, and a plastic deformation suppressing layer for suppressing plastic deformation due to a volume change of the negative electrode active material layer;
A negative current collector copper for a lithium ion secondary battery, comprising: a stress relaxation layer disposed between the plastic deformation suppression layer and the negative electrode active material layer and relieving stress due to a volume change of the negative electrode active material layer A foil is provided.

According to a second aspect of the invention,
A negative electrode current collector copper foil for a lithium ion secondary battery in which a negative electrode active material layer is formed on at least one side and incorporated in a negative electrode for a lithium ion secondary battery,
When incorporated in the negative electrode for lithium ion secondary battery,
The negative electrode active material layer is formed on at least one side, a small grain structure layer including a crystal structure having a small average grain size and fine crystal grains,
A large crystal structure layer including a crystal structure that is disposed between the small crystal structure layer and the negative electrode active material layer and has a crystal grain having an average grain size larger than that of the crystal grains of the small crystal structure layer. A negative electrode current collector copper foil for a lithium ion secondary battery is provided.

According to a third aspect of the invention,
A negative electrode current collector copper foil for a lithium ion secondary battery in which a negative electrode active material layer is formed on at least one side and incorporated in a negative electrode for a lithium ion secondary battery,
When incorporated in the negative electrode for lithium ion secondary battery,
The negative electrode active material layer is formed on at least one side, and includes a rolled structure layer including a rolled structure generated by rolling,
A recrystallized structure layer that is disposed between the rolled structure layer and the negative electrode active material layer and includes a recrystallized structure generated by a heat treatment when forming the negative electrode active material layer. A negative electrode current collector copper foil for a secondary battery is provided.

According to a fourth aspect of the invention,
Each of the plastic deformation suppression layer and the stress relaxation layer includes different crystal structures,
The average grain size of the crystal grains contained in the crystal structure of the stress relaxation layer, which is different from the average grain diameter of the crystal grains contained in the crystal structure of the plastic deformation suppression layer. The negative electrode current collection copper foil for lithium ion secondary batteries as described in a 1st aspect with large is provided.

According to a fifth aspect of the present invention,
The crystal structure contained in the plastic deformation suppressing layer is a rolled structure generated by rolling,
The lithium ion according to the fourth aspect, wherein the crystal structure that is included in the stress relaxation layer and is different from the rolled structure is a recrystallized structure that is generated by heat treatment when forming the negative electrode active material layer. A negative electrode current collector copper foil for a secondary battery is provided.

According to a sixth aspect of the present invention,
When incorporated in the negative electrode for lithium ion secondary battery,
It is formed in a rectangular shape,
In at least one of a cross section parallel to one side of the rectangular shape and a cross section orthogonal to the cross section,
The negative electrode current collector copper foil for a lithium ion secondary battery according to the third or fifth aspect, wherein an area ratio of a region occupied by the recrystallized structure with respect to the entire predetermined cross section is more than 5% and less than 90% Is done.

According to a seventh aspect of the present invention,
The negative electrode current collection copper foil for lithium ion secondary batteries in any one of the 1st-6th aspect which has oxygen-free copper as a main component is provided.

According to an eighth aspect of the present invention,
The negative electrode current collection copper foil for lithium ion secondary batteries in any one of the 1st-7th aspect containing 0.01 mass% or more and 0.20 mass% or less of Zr is provided.

According to a ninth aspect of the present invention,
The negative electrode current collector copper foil for a lithium ion secondary battery according to any one of the first to eighth aspects is incorporated,
The negative electrode active material layer formed on at least one surface of the negative electrode current collector copper foil for the lithium ion secondary battery and containing at least one of Si and Sn;
There is provided a negative electrode for a lithium ion secondary battery comprising a tab lead connected to the negative electrode current collector copper foil for the lithium ion secondary battery.

According to a tenth aspect of the present invention,
A negative electrode for a lithium ion secondary battery according to the ninth aspect;
A positive electrode for a lithium ion secondary battery;
A separator inserted between the negative electrode for lithium ion secondary battery and the positive electrode for lithium ion secondary battery;
There is provided a lithium ion secondary battery comprising: a negative electrode for a lithium ion secondary battery in which the separator is inserted; and a positive electrode for a lithium ion secondary battery accommodated therein and a container in which an electrolyte solution is enclosed.

  ADVANTAGE OF THE INVENTION According to this invention, the negative electrode current collector copper foil for lithium ion secondary batteries excellent in charging / discharging cycling characteristics, the negative electrode provided with the negative electrode current collector copper foil for lithium ion secondary batteries, and a lithium ion secondary battery are provided. .

It is a schematic diagram which illustrates the mode of the crystal structure which the negative electrode current collection copper foil for lithium ion secondary batteries which concerns on one Embodiment of this invention is equipped. It is a flowchart which shows the manufacturing process of the negative electrode current collection copper foil for lithium ion secondary batteries which concerns on one Embodiment of this invention. It is a top view of the negative electrode for lithium ion secondary batteries which concerns on one Embodiment of this invention. It is a perspective sectional view of a lithium ion secondary battery concerning one embodiment of the present invention. It is the reflected electron image which observed the cross section perpendicular | vertical to the rolling direction of the negative electrode current collection copper foil for lithium ion secondary batteries which concerns on Embodiments 1-3 and the comparative example 1 with the scanning electron microscope. It is the reflection electron image which observed the cross section perpendicular | vertical to the rolling direction of the negative electrode current collection copper foil for lithium ion secondary batteries which concerns on the comparative examples 2 and 3 with the scanning electron microscope.

<Knowledge obtained by the present inventors>
As described above, the negative electrode active material layer is formed on at least one surface of the negative electrode current collector copper foil for a lithium ion secondary battery. When forming the negative electrode active material layer, for example, heat treatment is performed at 400 ° C. for about 10 hours. At this time, the negative electrode current collector copper foil is softened and is easily plastically deformed. The plastically deformed negative electrode current collector copper foil can no longer follow the contraction of the negative electrode active material layer, and causes the negative electrode active material layer to peel off or drop off. Thus, for example, it is conceivable to use a rolled copper foil having high heat resistance and high yield strength as the negative electrode current collector copper foil.

  However, the present inventors have found that it is insufficient to simply improve the heat resistance and proof strength of the negative electrode current collector copper foil. That is, while the negative electrode active material layer repeatedly expands and contracts due to charge and discharge, even a high yield strength negative electrode current collector copper foil may not withstand stress and may crack. If there is a notch-like defect or the like at the end of the negative electrode current collector copper foil, it may break.

  As a result of intensive studies, the present inventors have found that when a negative electrode active material layer is formed on at least one side and incorporated into a negative electrode for a lithium ion secondary battery, the negative electrode current collector copper foil having a predetermined layer structure has a negative electrode active material. It has been found that peeling and dropping of layers can be suppressed, and cracks and breaks of the negative electrode current collector copper foil can be suppressed.

That is, the predetermined layer structure of the negative electrode current collector copper foil when incorporated into the negative electrode is, for example, a plastic deformation suppression layer in which the negative electrode active material layer is formed on at least one side, a plastic deformation suppression layer, and a negative electrode active material layer. It can be set as the stress relaxation layer arrange | positioned between. The plastic deformation suppression layer is a layer that suppresses the overall plastic deformation of the negative electrode current collector copper foil due to the volume change of the negative electrode active material layer. The stress relaxation layer is a layer that relaxes stress due to volume change of the negative electrode active material layer. Thereby, a negative electrode current collection copper foil exhibits the above-mentioned outstanding effect.

  As such a layer having a function as a plastic deformation suppression layer and a stress relaxation layer, for example, a configuration in which layers each having a predetermined crystal structure different from each other is combined can be considered. As an example of the different crystal structures, for example, crystal structures having different crystal grain sizes can be cited.

  That is, in this case, the average grain size contained in the crystal structure of the stress relaxation layer, which is different from the crystal grain structure of the plastic deformation suppression layer, than the average grain size of the crystal grains contained in the crystal structure of the plastic deformation suppression layer. Each layer is configured to have a large particle size. That is, the layer structure of each layer includes, for example, a small crystal structure layer including a crystal structure in which a negative electrode active material layer is formed on at least one side and has a small average particle size and fine crystal grains, and a small crystal structure layer and a negative electrode active layer. A large grain structure layer including a crystal structure having a crystal grain which is disposed between the material layers and has an average grain size larger than that of the crystal grains of the small grain structure layer can be obtained.

  Thus, when the average grain size in the crystal structure is small and the crystal grains are relatively fine, a layer having high proof stress and hardly undergoing plastic deformation is formed. On the other hand, when the crystal grains are relatively large, the layer is flexible and has excellent followability and relaxes the stress.

  In addition, as the crystal structure having fine crystal grains as described above, for example, a rolled structure generated by rolling is conceivable. Further, as a crystal structure having relatively large crystal grains, for example, a recrystallized structure generated by heat treatment when forming the negative electrode active material layer can be considered. That is, each layer is disposed between a rolled structure layer and a negative electrode active material layer, each of which includes, for example, a negative electrode active material layer formed on at least one side and including a rolled structure generated by rolling, and the negative electrode active material And a recrystallized structure layer including a recrystallized structure generated by a heat treatment when forming the layer.

  The present invention is based on the knowledge thus found by the inventors.

  In addition, in this specification, a negative electrode current collection copper foil points out the thing of the state before incorporating in the negative electrode for lithium ion secondary batteries in principle. At this time, the negative electrode current collector copper foil may not have the predetermined layer structure as described above, unlike the state after being incorporated into the negative electrode. As a state before the predetermined layer structure is obtained, for example, there is a state in which only a rolled structure is mainly provided as a crystal structure. Therefore, in this specification, the negative electrode current collector copper foil may refer to a state in which the main crystal structure is composed of a rolled structure.

  However, in this specification, the negative electrode current collector copper foil may refer to a negative electrode current collector copper foil that has been incorporated into a negative electrode for a lithium ion secondary battery, that is, a negative layer structure. Specifically, the negative electrode current collector copper foil sometimes refers to a negative electrode current collector copper foil having a state in which a plastic deformation suppression layer and a stress relaxation layer are provided. Alternatively, the negative electrode current collector copper foil may refer to a negative electrode current collector copper foil that has a state of having a small crystal structure layer and a large crystal structure layer. Alternatively, the negative electrode current collector copper foil may refer to a layer having a rolled structure layer and a recrystallized structure layer.

<One Embodiment of the Present Invention>
(1) Schematic Configuration of Lithium Ion Secondary Battery First, a schematic configuration of a lithium ion secondary battery according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a plan view of the negative electrode 1 for a lithium ion secondary battery according to this embodiment. FIG. 4 is a perspective sectional view of the lithium ion secondary battery 50 according to this embodiment.

  As shown in FIG. 4, the lithium ion secondary battery 50 includes a battery insertion can 5 as a container in which an electrolyte solution (not shown) is enclosed. The battery insertion can 5 includes a negative electrode 1 for a lithium ion secondary battery (hereinafter simply referred to as “negative electrode 1”) having a tab lead 12 and a positive electrode 2 for a lithium ion secondary battery (hereinafter referred to as “negative electrode 1”). (Also simply referred to as “positive electrode 2”) is accommodated with the separator 3 inserted therebetween.

  Further, as shown in FIG. 3, the negative electrode 1 is formed on a negative electrode current collector copper foil 10 for lithium ion secondary batteries (hereinafter, also simply referred to as “negative electrode current collector copper foil 10”), for example, on one side or both sides thereof. Negative electrode active material layer 11. The above-described tab lead 12 is directly connected to the exposed region 10 s of the negative electrode current collector copper foil 10. Detailed configurations of the lithium ion secondary battery 50 and the negative electrode 1 for a lithium ion secondary battery will be described later.

(2) Negative electrode current collector copper foil for lithium ion secondary battery Next, the negative electrode current collector copper foil for lithium ion secondary battery 10 according to an embodiment of the present invention, that is, a predetermined layer structure incorporated in the negative electrode 1 The current collector copper foil 10 before becoming will be described. In the present embodiment, the predetermined layer structure that the negative electrode current collector copper foil 10 includes is a rolled structure generated by rolling and a recrystallized structure generated by heat treatment when forming the negative electrode active material layer 11. Suppose that

  The negative electrode current collector copper foil 10 is, for example, a rolled copper foil that is formed in a long shape having a rolled surface as a main surface and has a thickness of 20 μm or less. For example, the longitudinal direction of the negative electrode current collector copper foil 10 is the rolling direction, that is, the extending direction during rolling, and the short direction is the direction perpendicular to the rolling direction.

  The negative electrode current collector copper foil 10 is made of, for example, a copper alloy material. As the copper (Cu) material in the copper alloy material, for example, oxygen-free copper (OFC) is used. The copper alloy material contains, for example, 0.01 mass% or more and 0.20 mass% or less of zirconium (Zr).

  In addition to Zr, an element having an effect of improving the heat resistance and proof stress of the negative electrode current collector copper foil 10 may be contained. As such an element, for example, iron (Fe), tin (Sn), zinc (Zn), nickel (Ni), aluminum (Al) or the like is added in an amount of 1.0% by mass or more and 5.0% by mass or less. , Fe, Sn, Zn, Ni, silicon (Si), chromium (Cr), or the like may be added in an amount of 0.1% by mass to 1.0% by mass.

  The negative electrode current collector copper foil 10 is configured such that the negative electrode active material layer 11 is formed on at least one surface and is incorporated into the negative electrode 1 for a lithium ion secondary battery. As described above, the current collector copper foil 10 before being incorporated into the negative electrode 1 and having a predetermined layer structure is, for example, in a state mainly including only a rolled structure.

  Further, when the negative electrode current collector copper foil 10 is incorporated into the negative electrode 1, a rolled structure layer as a plastic deformation suppressing layer in which the negative electrode active material layer 11 is formed on at least one side, a rolled structure layer, and the negative electrode active material layer 11. And a recrystallized structure layer as a stress relaxation layer disposed between the layers. The rolled structure layer includes, for example, a rolled structure and is configured to suppress plastic deformation due to a volume change of the negative electrode active material layer 11. The recrystallized structure layer includes, for example, a recrystallized structure, and is configured to relieve stress due to volume change of the negative electrode active material layer 11. The state of each layer is illustrated in FIG.

FIG. 1 is a schematic view illustrating the appearance of a rolled structure layer 10p and a recrystallized structure layer 10r that the negative electrode current collector copper foil 10 will have when incorporated into the negative electrode 1. FIG. The schematic diagram of FIG. 1 shows a cross section parallel to the short direction of the negative electrode current collector copper foil 10. Moreover, in FIG. 1, the rolling structure layer 10p
This shows an example in which the recrystallized structure layer 10r is formed on both sides.

  The rolled structure contained in the rolled structure layer 10p is a crystalline structure generated by rolling when the above-described copper alloy material is rolled to produce the negative electrode current collector copper foil 10. The rolled structure has relatively fine crystal grains having an average grain size of, for example, 0.3 μm or less. Alternatively, the range of the grain size of the crystal grains contained in the rolled structure is, for example, more than 0.01 μm and less than 1.0 μm. As shown in FIG. 1, the crystal grains in the rolled structure are fine and are crushed in the pressing direction during rolling, that is, in the thickness direction of the negative electrode current collector copper foil 10, so that the grain shape is flattened. Or it is acicular (fibrous). Such a crystal structure has a high proof stress, and is characterized in that it repeatedly undergoes elastic deformation according to, for example, a volume change of the negative electrode active material layer 11 and hardly reaches plastic deformation.

  The recrystallized structure contained in the recrystallized structure layer 10r is obtained by forming the negative electrode active material layer 11 on the negative electrode current collector copper foil 10 by the above-described heat treatment to produce the negative electrode current collector copper foil 10 when the negative electrode 1 is manufactured. This is a crystal structure that is generated by recrystallization of a part of the rolling structure that constitutes the structure. The recrystallized structure has relatively large crystal grains having an average grain size of, for example, 3 μm or more. Or the range of the particle size of the crystal grain contained in a recrystallized structure is 1.0 micrometer or more and 10.0 micrometers or less, for example. As shown in FIG. 1, the crystal grains in the recrystallized structure have a large grain size, and equiaxed individual crystal grains gather together with almost no gap and are separated by a relatively clear grain boundary. (Patch-like). Such a crystal structure allows a certain amount of elongation due to the volume change of the negative electrode active material layer 11, provides a buffering action with the rolled structure layer 10 p, and gives the negative electrode current collector copper foil 10 flexibility.

  In addition, the average particle diameter of the crystal grains contained in the rolled structure and the recrystallized structure is a value obtained by the “quadrature method” of the “copper grain size test method” defined in JIS H0501. That is, it is a value obtained from the number of crystal grains included in a predetermined area in the crystal structure.

  In the state having the recrystallized structure, the area ratio of the region occupied by the recrystallized structure to the entire cross section in the cross section parallel to the short direction of the long negative electrode current collector copper foil 10, that is, perpendicular to the rolling direction is For example, it is more than 5% and less than 90%. Alternatively, the area ratio may be 10% or more and 80% or less. Moreover, when a recrystallized structure is produced | generated only on the single side | surface of the negative electrode current collection copper foil 10, the area ratio may be near the minimum in these ranges, for example. As long as this area ratio is satisfied, the recrystallized structure layer may contain not only the recrystallized structure but also a rolled structure. In other words, the recrystallized structure layer may be a substantially homogeneous layer consisting only of the recrystallized structure, and a layer in which the rolled structure remains in an island shape in the recrystallized structure or a recrystallized structure in the rolled structure. A layer generated in an island shape may be used.

  However, since similar crystal structures tend to be arranged in the rolling direction, even if a sufficient amount of recrystallized structure is generated as a whole, the above-mentioned area ratio is not necessarily obtained in a cross section parallel to the rolling direction. It does not always meet.

(3) Method for Producing Negative Electrode Current Collected Copper Foil for Lithium Ion Secondary Battery Next, referring to FIG. A method for manufacturing the current collector copper foil 10 before the predetermined layer structure is obtained will be described. FIG. 2 is a flowchart showing a manufacturing process of the negative electrode current collector copper foil 10 according to this embodiment.

(Copper alloy material preparation step S10)
As shown in FIG. 2, first, an ingot (ingot) as a copper alloy material as a raw material is prepared. Such an ingot uses, for example, oxygen-free copper as a copper material, and for example, 0.01 mass% or more and 0.20 mass% or less of zirconium (Zr) is added, and these are melted and cast. Alternatively, in addition to Zr, for example, Fe, Sn, Zn, Ni within the above-mentioned predetermined concentration range
, Al, Si, Cr, etc. may be added as appropriate.

(Hot rolling process S20)
Next, hot rolling is performed on the above-described ingot to form a plate material. Prior to the hot rolling step S20, it is desirable to perform a heat treatment for homogenizing segregation occurring in the cast structure.

(Repetition step S30)
Then, the repetition process S30 which repeats cold rolling process S31 and annealing process S32 in multiple times with respect to the board | plate material which gave the hot rolling process is performed.

The cold rolling step S31 is performed with a working degree of, for example, 50% or more. Here, the processing degree of the cold rolling step S31 before the workpiece thickness of the (sheet of copper) and T _B, and the thickness of the cold working object after the rolling step S31 to T _A, processed Degree (%) = [(T _B −T _A ) / T _B ] × 100.

  In the annealing step S32, the above-described plate material that has been cold-rolled and work hardened is subjected to an annealing treatment to anneal the plate material, thereby relaxing the work hardening. By repeating this a predetermined number of times, a copper strip called “dough” is obtained. When an additive for adjusting heat resistance is added to the copper material, the temperature condition of the annealing treatment is appropriately changed according to the heat resistance of the copper material.

  In addition, in the repetition process S30, the annealing process S32 in the middle of the repetition is referred to as an “intermediate annealing process”. Further, the annealing step S32 performed at the end of the repetition, that is, immediately before the final cold rolling step S40 described later is referred to as a “final annealing step” or a “dough annealing step”.

(Final cold rolling process S40)
Next, the final cold rolling step S40 is performed on the dough subjected to the repeating step S30 to obtain a rolled copper foil having a predetermined thickness, for example, 20 μm or less. At this time, the degree of work is set to, for example, 82% or more and 90% or less, the crystal grains in the dough are refined, and the work distortion is sufficiently accumulated to sufficiently develop the rolling structure with high yield strength.

  Thereby, high strength (crystal grain refinement strengthening) occurs due to fine crystal grains in the crystal structure, and an effect of suppressing plastic deformation of the rolled structure layer 10p occurs. In addition, the rolled structure layer 10p is also strengthened by processing strain (work strengthening) accumulated in the rolled structure layer 10p by rolling, and the effect of suppressing plastic deformation is further enhanced.

  The fabric subjected to the above steps may be subjected to predetermined surface treatment such as roughening treatment and rust prevention treatment.

  As described above, the negative electrode current collector copper foil 10 for a lithium ion secondary battery composed of a rolled structure as a main crystal structure is manufactured.

  In addition, the state of the recrystallized structure produced | generated by the heat processing at the time of formation of the negative electrode active material layer 11 mentioned later is influenced by various conditions in the manufacturing process of the above-mentioned negative electrode current collector copper foil 10. Specifically, for example, the degree of processing in the final cold rolling step S40, the temperature of the rolling processing oil, the strain rate and strain distribution, the concentration distribution of additive elements and impurity elements in the copper alloy material, and the solid solution state of these elements , Precipitation state and the like. Therefore, in the above-described manufacturing process, these conditions are adjusted as appropriate so that a desired recrystallized structure can be obtained.

In particular, when Zr is contained as an additive, a phenomenon in which a recrystallized structure is generated mainly only in the vicinity of the surface of the negative electrode current collector copper foil 10 is easily exhibited, and includes a rolled structure layer and a recrystallized structure layer. The above configuration is easily obtained.

(4) Manufacturing method of negative electrode for lithium ion secondary battery Next, the manufacturing method of the negative electrode 1 for lithium ion secondary batteries provided with the structure shown in FIG. 3 is demonstrated. By performing this manufacturing method, the negative electrode current collector copper foil 10 is incorporated in the negative electrode 1 and has a predetermined layer structure.

(Slurry application process)
First, a method of applying a slurry to the negative electrode current collector copper foil 10 and performing pressure bonding will be described. Such a process is performed using an apparatus such as an applicator that applies slurry to the negative electrode current collector copper foil 10 by, for example, a continuous line of a coil-to-coil system.

  Specifically, for example, a negative electrode active material, a binder solution, and a slurry obtained by kneading a conductive aid as necessary are applied to one or both surfaces of the negative electrode current collector copper foil 10 and are uniformed to a substantially uniform thickness. For example, it is dried at 70 ° C. to 130 ° C. for several minutes to several tens of minutes.

  As the negative electrode active material contained in the slurry, for example, an alloy such as Si or Sn, or a powder such as a compound can be used. The diameter of each powder is, for example, several μm to several tens of μm. As the binder solution, a solution of an imide resin such as polyimide (PI) or a precursor of another resin can be used.

(Heat treatment process)
Next, for example, using an infrared heating furnace or the like, the negative electrode current collector copper foil 10 to which the slurry is pressure-bonded is subjected to a heat treatment for a long time at a temperature higher than the temperature of the thermoplastic region of the binder component. Specifically, heat treatment at 350 ° C. to 450 ° C. is performed for 1 hour to 16 hours. At this time, heat treatment is performed in a non-oxidizing atmosphere such as nitrogen (N ₂ ) gas or argon (Ar) gas, for example, in vacuum (under reduced pressure). As a result, for example, the binder component made of a precursor such as an imide-based resin solidifies as the imidization reaction proceeds while entering the irregularities of the negative electrode active material particles. Thereby, the negative electrode active material layer 11 containing a binder such as a negative electrode active material and an imidized polyimide resin is formed on one surface or both surfaces of the negative electrode current collector copper foil 10.

  In addition, by such heat treatment, a part of the crystal structure in the negative electrode current collector copper foil 10 is recrystallized to generate a recrystallized structure. When such recrystallization occurs, the processing strain generated during rolling is substantially eliminated, and the effect of stress relaxation due to the recrystallized structure occurs. In addition, since the relatively large crystal grains in the recrystallized structure allow elongation due to volume expansion of the negative electrode active material layer 11, an effect of stress relaxation occurs.

  As described above, the negative electrode active material layer 11 is formed on at least one side, and the rolled structure layer as the plastic deformation suppressing layer that suppresses plastic deformation due to the volume change of the negative electrode active material layer 11, the rolled structure layer, and the negative electrode active material layer 11. And a recrystallized structure layer as a stress relieving layer that relieves stress due to volume change of the negative electrode active material layer 11.

  That is, for example, when the negative electrode active material layer 11 is formed only on one surface of the negative electrode current collector copper foil 10, a recrystallized structure layer is generated on at least the surface of the rolled structure layer on which the negative electrode active material layer 11 is formed. Will be. However, at this time, a recrystallized structure layer may be generated on both sides of the rolled structure layer, including the side where the negative electrode active material layer 11 is not formed.

For example, when the negative electrode active material layer 11 is formed on both surfaces of the negative electrode current collector copper foil 10, it is preferable that a recrystallized structure layer is formed on both surfaces of the rolled structure layer. However, at this time, even if the recrystallized structure layer is generated only on one side of the rolled structure layer, the predetermined effect of relieving the stress due to the volume change of the negative electrode active material layer 11 can be obtained.

  For example, when the negative electrode active material layer 11 is formed only on one side, a recrystallized structure layer is generated only on the side of the negative electrode current collector copper foil 10 where the negative electrode active material layer 11 is formed. A method of performing heat treatment in a sufficiently lowered state can be employed. At such a low temperature, the negative electrode current collector copper foil 10 is heated from the side where the negative electrode active material layer 11 is formed, or the temperature on the side where the negative electrode active material layer 11 is not formed is further lowered than the other side to perform heat treatment. Apply.

(Tab lead connection process)
Next, a method for connecting the tab lead 12 to the negative electrode current collector copper foil 10 will be described with reference to FIG.

  As shown in FIG. 3, the negative electrode active material layer 11 is formed on one side or both sides, and the negative electrode current collector copper foil 10 separated into strips along the rolling direction, for example, has at least one end on one side or both sides. It has an exposed region 10s where the material layer 11 is not formed. The tab lead 12 is connected to the exposed region 10 s of the negative electrode current collector copper foil 10 by welding, for example, in order to make an electrical connection with the battery outer can 5 provided in the lithium ion secondary battery 50.

  That is, the exposed region 10 s of the negative electrode current collector copper foil 10 and the tab lead 12 made of, for example, Ni or Ni-plated copper are overlaid, for example, with an ultrasonic welding machine while applying a predetermined pressure and load energy, The welding process is performed with a load time of. Thereby, the negative electrode current collection copper foil 10 and the tab lead 12 are connected.

  As described above, the negative electrode current collector copper foil 10 for a lithium ion secondary battery provided with a rolled structure layer and a recrystallized structure layer, the negative electrode active material layer 11 formed on at least one surface or both surfaces of the negative electrode current collector copper foil 10, The negative electrode 1 for lithium ion secondary batteries provided with the tab lead 12 connected to the negative electrode current collection copper foil 10 is manufactured.

(5) Manufacturing Method of Lithium Ion Secondary Battery Next, a manufacturing method of the lithium ion secondary battery 50 will be described with reference to FIG.

  First, the negative electrode 1 for lithium ion secondary batteries and the positive electrode 2 for lithium ion secondary batteries are overlapped via the separator 3, and the winding body 4 wound around the core which is not shown in figure is manufactured. The positive electrode 2 is connected to a positive electrode current collector metal foil for a lithium ion secondary battery, a positive electrode active material layer formed on, for example, both surfaces of the positive electrode current collector metal foil (both not shown), and the positive electrode current collector metal foil Tab lead 22. The metal which comprises positive electrode current collection metal foil is lithium (Li), aluminum (Al), another metal etc., for example. The positive electrode active material layer is made of, for example, a metal composite oxide containing Li. The separator 3 is made of, for example, a porous resin.

  Next, a lower insulating plate (not shown) and the wound body 4 are accommodated in this order in a battery extrapolation can 5 as a container. Subsequently, after inserting a mandrel (core metal) (not shown) into the center of the wound body 4 and housing the upper insulating plate in the battery outer can 5, the groove 6 is formed (grooved) in the battery outer can 5. . Thereafter, drying is performed to remove moisture in the battery extrapolation can 5. When the inside of the battery extra can 5 is sufficiently dried, an electrolyte solution (not shown) is injected. Next, a gasket 7 is mounted in the vicinity of the groove 6 of the battery insertion can 5, the tab lead 12 of the negative electrode 1 is welded to the battery external insertion can 5, and the tab lead 22 of the positive electrode 2 is welded to the terminal 8 t provided on the cap 8. 8 is crimped (crimped) on the battery extrapolation can 5 to enclose the electrolyte.

  As described above, the lithium ion secondary battery including the battery insertion can 5 in which the negative electrode 1 for the lithium ion secondary battery and the positive electrode 2 for the lithium ion secondary battery with the separator 3 interposed therebetween are accommodated and the electrolyte is enclosed. 50 is manufactured.

  Here, the cylindrical lithium ion secondary battery 50 shown in FIG. 4 has been described as an example, but the lithium ion secondary battery may have other forms such as a square type and a laminate type. Along with this, the negative electrode 1 and the positive electrode 2 can also take various forms such as a wound type as described above or a laminated type.

  A shape that can be taken by the negative electrode current collector copper foil for a lithium ion secondary battery when incorporated in a negative electrode for a lithium ion secondary battery mainly includes a rectangular shape cut in parallel along the rolling direction. The rectangular shape is a rectangular shape including a square shape, and includes a long shape wound in the above-described roll shape.

  In confirming the presence or absence of the recrystallized structure and the existence ratio (area ratio in the cross section) of the negative electrode current collector copper foil 10 after being cut into such a rectangular shape, the rolling direction may not be specified. As described above, similar crystal structures are arranged in the rolling direction. Therefore, for example, when the recrystallized structure is scattered in the form of islands in the rolled structure layer, the recrystallized structure may be deviated if the extracted cross section happens to be parallel to the rolling direction. In this case, although a sufficient recrystallized structure is generated, no recrystallized structure is observed at all.

  However, even if the rolling direction cannot be specified, if two cross sections, a cross section parallel to one side of the negative electrode current collector copper foil 10 cut into a rectangular shape and a cross section orthogonal to the cross section, are observed. In either case, information on a cross section perpendicular to the rolling direction can be obtained. The rolled structure and the recrystallized structure can be discriminated by the average particle diameter of the crystal grains in each crystal structure, the shape, whether it is a fibrous structure or a mosaic structure, and the like.

  However, as described above, there are cases where the recrystallized structure layer varies depending on the location, for example, is scattered in an island shape in the rolled structure. Therefore, in order to determine the presence or absence of the recrystallized structure, it is necessary to continuously observe the cross section at least over 50 μm in the width direction of the cross section.

  In the negative electrode current collector copper foil 10 of this embodiment, a recrystallized structure is observed in at least one of the two cross sections, and the area ratio of the region occupied by the recrystallized structure with respect to the entire predetermined cross section is, for example, 5%. It may be less than 90% or 10% to 80%. When the recrystallized structure is generated only on one side, it may be closer to the lower limit within these ranges.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

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

(A) That is, in this embodiment, when the negative electrode current collector copper foil 10 is incorporated in the negative electrode 1, a rolled structure layer 10p as a plastic deformation suppression layer in which the negative electrode active material layer 11 is formed on at least one side, And a recrystallized structure layer 10r as a stress relaxation layer disposed between the structure layer 10p and the negative electrode active material layer 11.

The rolled structure layer 10p, which has been strengthened by grain refinement strengthening or work strengthening, withstands the stress caused by the volume change of the negative electrode active material layer 11 and repeats elastic deformation, thereby suppressing plastic deformation of the negative electrode current collector copper foil 10. be able to. Therefore, peeling and dropping of the negative electrode active material layer 11 from the negative electrode current collector copper foil 10 can be suppressed. Moreover, it can suppress that the negative electrode current collection copper foil 10 extends | stretches or wavy, and an internal short circuit generate | occur | produces in the lithium ion secondary battery 50.

  Further, the recrystallized structure layer 10r having large crystal grains that are substantially free from processing distortion and that allow elongation is relieved by following the volume change of the negative electrode active material layer 11, and the negative electrode active material layer 11 and A buffering action is produced between the rolled structure layer 10p. Therefore, it can suppress that a crack arises in the negative electrode current collection copper foil 10, or the negative electrode current collection copper foil 10 breaks.

(B) Moreover, in this embodiment, each layer which has a different function of suppression of plastic deformation and stress relaxation is formed in the negative electrode current collector copper foil 10. Thereby, in order to give such a different function, it is not necessary to add an extra structure to the negative electrode current collector copper foil 10, for example, and the structure of the negative electrode current collector copper foil 10 and the negative electrode 1 can be simplified.

(C) In this embodiment, the rolled structure layer 10p is a layer including a rolled structure generated by rolling, and the recrystallized structure layer 10r is a regenerated structure generated by heat treatment when the negative electrode active material layer 11 is formed. It is a layer containing a crystal structure. This makes it possible to form these layers relatively easily without significantly changing existing processes or increasing the number of processes.

(D) In this embodiment, the recrystallized structure is generated by heat treatment when forming the negative electrode active material layer 11. Thereby, the process of generating a recrystallized structure can be combined with the process of forming the negative electrode active material layer 11, and further efficiency can be achieved.

(E) Moreover, in this embodiment, it is comprised so that the area ratio of the area | region where a recrystallized structure occupies with respect to the whole cross section may become more than 5% and less than 90% in the cross section perpendicular | vertical to a rolling direction. Since the area ratio of the region occupied by the recrystallized structure is, for example, more than 5%, the recrystallized structure layer 10r can sufficiently relax the stress. Moreover, since the area ratio is, for example, less than 90%, it is possible to prevent the negative electrode current collector copper foil 10 from being stretched due to the charge / discharge cycle, and peeling of the negative electrode active material layer 11 or internal short circuit.

(F) Moreover, in this embodiment, it observes about two cross sections, the cross section parallel to one side of the negative electrode current collection copper foil 10 cut out to the rectangular shape, and the cross section orthogonal to the cross section. Thereby, in the negative electrode current collector copper foil 10 after being cut out, it is possible to determine whether or not a desired recrystallized structure has been generated even in a situation where it is difficult to specify the rolling direction.

(G) Moreover, in this embodiment, the negative electrode current collection copper foil 10 is comprised from the rolled copper foil which has an oxygen free copper as a main component. Thus, for example, by using a material that can easily obtain high heat resistance and high yield strength compared to tough pitch copper and electrolytic copper, plastic deformation of the negative electrode current collector copper foil 10 is further suppressed, and the negative electrode active material layer 11 Dropout and the like can be suppressed.

(H) Moreover, in this embodiment, the negative electrode current collection copper foil 10 contains 0.01 mass% or more and 0.20 mass% or less of Zr. As a result, a phenomenon in which a recrystallized structure is generated mainly only in the vicinity of the surface of the negative electrode current collector copper foil 10 is easily expressed, and the configuration of the present embodiment including the rolled structure layer 10p and the recrystallized structure layer 10r is obtained. easy. Further, solid solution strengthening occurs due to the solid solution of Zr in the base material Cu, and the strength of the negative electrode current collector copper foil 10 as a whole can be improved.

(I) In the present embodiment, the degree of processing in the final cold rolling step S40 is set to 82% or more and 90% or less. As a result, the crystal grains in the dough can be made fine, and the processing strain can be sufficiently accumulated to sufficiently develop a rolled structure with high yield strength. Further, since the degree of work is suppressed to 90% or less, the area ratio occupied by the recrystallized structure can be suppressed to, for example, less than 90% during the heat treatment.

  Various evaluation results performed on the negative electrode current collector copper foil for lithium ion secondary batteries according to examples of the present invention will be described below.

(1) Manufacture of negative electrode current collector copper foil First, negative electrode current collector copper foils according to Examples 1 to 3 and Comparative Examples 1 to 3 were manufactured according to the procedure described below.

  Specifically, among HCL copper foils (HCL is a registered trademark) manufactured by Hitachi Cable, Ltd., which is a rolled copper foil using oxygen-free copper as a base material, 12 μm thick HCL02Z (Cu—Zr) foil (Zr is 0) Example 1 by applying the configuration of the above-described embodiment to the configuration of 0.02% by mass, the balance being Cu and inevitable impurities), and variously changing the rolling conditions and the like within a range in which the same configuration as this configuration is obtained It was set as the negative electrode current collection copper foil which concerns on ~ 3. Moreover, it was set as the negative electrode current collection copper foil which concerns on the comparative example 1 by changing rolling conditions etc. variously so that the range which remove | deviates from the structure concerned may be included. Further, 12 μm-thick tough pitch copper (TPC) foil (Cu purity 99.9% by mass) manufactured by Hitachi Cable, Ltd. was used as Comparative Example 2, and 10 μm-thick electrolytic foil was used as Comparative Example 3.

  In addition, when an example of the working degree in the final cold rolling process is given, in Example 2, the working degree is 88%.

(2) Measurement of negative electrode current collector copper foil Next, various measurements were performed on these negative electrode current collector copper foils.

  First, these negative electrode current collector copper foils were heat-treated at 400 ° C. for 10 hours, and then a cross section perpendicular to the rolling direction was observed with a scanning electron microscope to obtain reflected electron images. This heat treatment condition simulates the heat treatment condition when forming the negative electrode active material layer.

  Moreover, the negative electrode active material layer was actually formed on one surface of the negative electrode current collector copper foil before the heat treatment, and various measurements were performed.

First, silicon monoxide (SiO) powder manufactured by Osaka Titanium Technology Co., Ltd. is used as the negative electrode active material, acetylene black is used as the conductive auxiliary agent, and a commercially available polyimide (PI) varnish (PI precursor N-) is used as the binder. Methylpyrrolidone (NMP) solution) was used. These were kneaded for 1 hour with a kneader manufactured by Sinky Co., Ltd. at a mass mixing ratio excluding the solvent content of SiO: acetylene black: polyimide = 80: 5: 15 to prepare a slurry. This was applied to one side of the negative electrode current collector copper foil using an applicator and dried. Thereafter, the maximum temperature was set to 400 ° C. and heated for 10 hours in a nitrogen (N ₂ ) atmosphere.

  Thus, a negative electrode active material layer having a thickness of 15 μm was formed on one surface of the negative electrode current collector copper foil.

Next, an electrolytic solution LIPASTE-EDMC / PF1 manufactured by Toyama Pharmaceutical Co., Ltd. was placed in a glass beaker in a glove box under an argon (Ar) gas atmosphere. Furthermore, the negative electrode current collection copper foil in which the negative electrode active material layer was formed, and the metal lithium (Li) board were immersed in electrolyte solution. In this state, a charge / discharge test was performed using a battery charge / discharge device HJ-1001 SM8A manufactured by Hokuto Denko Corporation. Specifically, 1 C discharge was performed at 0 V to 1 V (vs. Li / Li ⁺ ), and resting for 20 minutes, similarly 1 C discharging and resting for 20 minutes were repeated. After 50 cycles, the adhesion state of the negative electrode active material layer and the presence or absence of deformation of the negative electrode current collector copper foil were observed.

Separately, a negative electrode current collector copper foil having the negative electrode active material layer formed on one side is 2 cm ^2.
Punched into a circle. This circular negative electrode current collector copper foil was used as a negative electrode, a metal Li plate was used as a positive electrode, and a single electrode cell was assembled through a separator manufactured by Celguard Co., Ltd. As the cell, an HS cell manufactured by Hosen Co., Ltd. was used. As the electrolytic solution, an electrolytic solution LIPASTE-EDMC / PF1 manufactured by Toyama Pharmaceutical Co., Ltd. was used. The assembly work was performed in a glove box with an Ar gas atmosphere. Under the same charge / discharge conditions as described above, a cycle test of 100 cycles was performed, and the discharge capacity retention rate was measured. Moreover, the cell after a test was disassembled and the electrode shape was visually observed.

(3) Evaluation Results of Negative Electrode Current Collecting Copper Foil Reflected electron images of cross sections perpendicular to the rolling direction of the negative electrode current collecting copper foils according to Examples 1 to 3 and Comparative Example 1 after the heat treatment are shown in FIGS. d) respectively. Moreover, the reflected electron image of a cross section perpendicular | vertical to the rolling direction of the negative electrode current collection copper foil which concerns on the comparative examples 2 and 3 after heat processing is shown to Fig.6 (a), (b), respectively.

  As shown in FIG. 5, in Examples 1 to 3 and Comparative Example 1 composed of rolled copper foil using oxygen-free copper as a base material, recrystallization in which the crystal structure of the surface of the current collector copper foil was greatly grown Organization is recognized. Moreover, a slightly flat and fine rolling structure is recognized near the center in the thickness direction.

  From the reflected electron images of FIGS. 5 and 6, the area ratio of the region occupied by the recrystallized structure with respect to the entire cross section in the cross section perpendicular to the rolling direction was obtained, and the following results were obtained. That is, the area ratios in Examples 1 to 3 and Comparative Example 1 were 75%, 53%, 10%, and 5%, respectively. Moreover, the area ratios in Comparative Examples 2 and 3 were all 100%.

  Next, the observation results of the adhesion state of the negative electrode active material layers of Examples 1 to 3 and Comparative Examples 1 to 3 and the presence or absence of deformation of the negative electrode current collector copper foil are shown in Table 1 below. In the table, “adhesion state of the active material layer” was defined as “good”, “△” slightly peeled, and “×” almost peeled. In addition, in the “determination” result based on the adhesion state of the negative electrode active material layer and the presence or absence of deformation of the negative electrode current collector copper foil, ◯ was good and x was bad.

  As shown in Table 1, in Comparative Examples 2 and 3 in which the area ratio of the region occupied by the recrystallized structure was 100%, the negative electrode active material layer was slightly peeled. In Comparative Examples 2 and 3, since deformation of the negative electrode current collector copper foil was also observed, it is considered that the negative electrode active material layer was peeled off due to plastic deformation of the negative electrode current collector copper foil. In Comparative Example 1 in which the area ratio of the region occupied by the recrystallized structure was only 5%, the negative electrode current collector copper foil was not deformed, but peeling of the negative electrode active material layer was confirmed.

  Thus, if there is not enough rolling structure left in the negative electrode current collector copper foil, plastic deformation of the negative electrode current collector copper foil occurs, peeling of the negative electrode active material layer occurs, and the inside of the lithium ion secondary battery It can also cause a short circuit.

  On the other hand, in Examples 1 to 3 where the area ratio of the region occupied by the recrystallized structure was 75%, 53%, and 10%, the adhesion of the negative electrode active material layer was good. Moreover, deformation of the negative electrode current collector copper foil was not observed. This is probably because the recrystallized structure relaxed the stress due to the volume change of the negative electrode active material layer, and the rolled structure suppressed the deformation of the negative electrode current collector copper foil. From the above, it was found that good results can be obtained if the area ratio of the region occupied by the recrystallized structure is within a predetermined range.

  Next, Table 2 below shows the measured values of the discharge capacity retention ratio of Example 2 and Comparative Example 2 and the results of visual observation of the electrode shape. In the table, in the “determination” result based on the discharge capacity retention ratio and the electrode shape, “good” means “good” and “poor” means “bad”.

  As shown in Table 2, it was found that when the area ratio of the region occupied by the recrystallized structure is within a predetermined range, a high discharge capacity retention rate is obtained. It was also found that no electrode deformation occurred.

DESCRIPTION OF SYMBOLS 1 Negative electrode for lithium ion secondary batteries 2 Positive electrode for lithium ion secondary batteries 3 Separator 4 Winding body 5 Battery extrapolation can (container)
6 groove 7 gasket 8 cap 8t terminal 10 negative electrode current collector copper foil for lithium ion secondary battery 11 negative electrode active material layer 12, 22 tab lead 50 lithium ion secondary battery

Claims (5)

Applying and pressure-bonding a slurry containing at least one of Si or Sn to at least one surface of a negative electrode current collector copper foil made of a rolled copper foil;
Forming a negative electrode active material layer by performing a heat treatment on the negative electrode current collector copper foil to which the slurry is pressure-bonded,
A method for producing a negative electrode current collector copper foil for a lithium ion secondary battery incorporated in a negative electrode for a lithium ion secondary battery,
The negative electrode current collector copper foil for the lithium ion secondary battery is :
The negative electrode active material layer is formed on at least one side, and a plastic deformation suppressing layer for suppressing plastic deformation due to a volume change of the negative electrode active material layer;
A stress relaxation layer disposed between the plastic deformation suppression layer and the negative electrode active material layer and relieving stress due to a volume change of the negative electrode active material layer,
The plastic deformation suppression layer and the stress relaxation layer include different crystal structures, respectively, and an average grain size of crystal grains contained in the crystal structure of the plastic deformation suppression layer is different from that of the plastic deformation suppression layer. Is a large average grain size of the crystal grains contained in the different crystal structure of the stress relaxation layer,
The crystal structure included in the plastic deformation suppression layer is a rolled structure generated by rolling, and the crystal structure included in the stress relaxation layer is different from the rolled structure when the negative electrode active material layer is formed. A recrystallized structure to be generated by the heat treatment,
A negative electrode current collector copper foil for a lithium ion secondary battery, wherein an area ratio of a region occupied by the recrystallized structure with respect to the entire predetermined cross section in a cross section perpendicular to the rolling direction is more than 5% and less than 90% Manufacturing method . The method for producing a negative electrode current collector copper foil for a lithium ion secondary battery according to claim 1, wherein the rolled copper foil contains oxygen-free copper as a main component. The said rolled copper foil contains 0.01 mass% or more and 0.20 mass% or less of Zr, The manufacturing method of the negative electrode current collection copper foil for lithium ion secondary batteries of Claim 1 or 2 characterized by the above-mentioned. A negative electrode current collector copper foil for a lithium ion secondary battery produced by the method according to claim 1 is incorporated,
The negative electrode active material layer formed on at least one surface of the negative electrode current collector copper foil for the lithium ion secondary battery and containing at least one of Si and Sn;
And a tab lead connected to the negative electrode current collector copper foil for a lithium ion secondary battery. A method for producing a negative electrode for a lithium ion secondary battery. A negative electrode for a lithium ion secondary battery produced by the method according to claim 4;
A positive electrode for a lithium ion secondary battery;
A separator inserted between the negative electrode for lithium ion secondary battery and the positive electrode for lithium ion secondary battery;
A lithium ion secondary battery comprising: a negative electrode for a lithium ion secondary battery in which the separator is inserted; and a container in which the positive electrode for a lithium ion secondary battery is accommodated and an electrolyte is enclosed. Manufacturing method .