KR102003342B1 - Copper foil for negative electrode current collector of lithium secondary battery, negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Abstract

(Problem) An excellent charge-discharge cycle characteristic is obtained.
A negative electrode current collecting copper foil for a lithium ion secondary battery, comprising a negative electrode active material layer formed on at least one surface thereof and provided on a negative electrode for a lithium ion secondary battery, wherein when the negative electrode active material layer is provided on a negative electrode for a lithium ion secondary battery, A plastic deformation restraining layer formed on the plastic deformation suppressing layer and the negative electrode active material layer for suppressing plastic deformation due to volume change of the negative electrode active material layer and a stress which alleviates the stress due to volume change of the negative electrode active material layer And a mitigating layer.

Description

Technical Field The present invention relates to a negative electrode current collecting copper foil for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

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

BACKGROUND ART Lithium-ion secondary batteries are used for communication devices such as mobile phones, notebook computers, power tools, hybrid cars, electric vehicles, and large-scale power storage facilities. The lithium ion secondary battery is mainly composed of a positive electrode, a negative electrode, a separator for insulating the positive electrode and the negative electrode, and an electrolyte capable of moving lithium (Li +) ions between the positive electrode and the negative electrode.

The negative electrode for a lithium ion secondary battery includes, for example, a negative electrode collector (negative electrode collector) and a negative electrode active material layer (negative electrode active material layer) bonded to the negative electrode collector. As the negative electrode current collector, for example, a copper foil is used. In addition to the negative electrode active material such as carbon or graphite, a conductive additive such as acetylene black, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyimide (PI) And contains a binder.

As described above, a carbon-based material such as carbon has been mainly used as an anode active material. However, in the lithium ion secondary battery using the carbon-based material, the charging / discharging capacity almost reaches the theoretical value of 372 mAh / g, making it difficult to further increase the capacity. Therefore, in order to further increase the capacity, practical use of a negative electrode active material mainly using, for example, tin (Sn) or 4200 mAh / g of silicon (Si) having a theoretical charge / discharge capacity of 990 mAh / g has been studied.

A high capacity negative electrode active material composed mainly of Sn or Si is alloyed (alloyed) with lithium (Li) at the time of charging, so that the volume expands greatly and shrinks at the time of discharging. For example, the volume change rate of Si is 400%, which is significantly larger than that of conventional graphite of 110%. Therefore, in the negative electrode current collecting copper foil holding the negative electrode active material layer containing them, a large stress is generated due to charging and discharging. As a result, the negative electrode active material layer is peeled off from the negative current collecting copper foil, and the electrical connection between the negative current collecting copper foil and the negative electrode active material is deteriorated, which may result in deterioration of the battery capacity. Otherwise, the anode current collecting copper foil is elongated, and there is a high possibility of causing an internal short circuit.

Thus, for example, Patent Documents 1 and 2 employ a method of using a material having a high modulus of elasticity as a binder to relieve the stress applied to the negative electrode current collector. That is, Patent Document 1 proposes a negative electrode for a lithium secondary battery using an alloy powder containing Sn as an active material particle and a thermoplastic resin having a modulus of elasticity of 3.0 GPa or more as a binder (binder). Accordingly, when the active material particles expand / contract due to charging / discharging, deformation of the entire negative electrode active material layer can be reduced.

Patent Document 2 proposes a negative electrode in which a negative electrode active material is a powder material made of Si or an Si alloy and a mixed slurry containing a polyimide resin as a binder is coated on a current collector, followed by drying and heat treatment. Further, as described in Patent Document 2, for a binder having a high modulus of elasticity such as a polyimide resin, heat treatment is often performed for about 10 hours at around 400 degrees. Thereby promoting the imidization of the polyimide resin, for example.

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

Patent Document 1: Japanese Patent Application Laid-Open No. 2007-149604 Patent Document 2: JP-A-2005-317309 Patent Document 3: Japanese Patent No. 4438541

However, as in Patent Documents 1 and 2, the use of a binder having a high modulus of elasticity is not sufficient for expansion / contraction of the negative electrode active material. As described above, the copper foil serving as the negative electrode current collector is softened by the heat treatment for the binder and easily plastic-deformed. When the plastic deformation occurs, the negative electrode active material layer is peeled or removed from the negative electrode current collector by repeated charging and discharging, and the charge-discharge cycle characteristic is deteriorated. As a result, the electrical connection between the negative electrode current collector and the negative electrode active material is deteriorated, and battery capacity may be deteriorated. Also in this case, the lifetime of the lithium ion secondary battery is shortened.

In Patent Document 3, the tensile strength is improved by the hard cobalt plated layer or the like, but when the copper foil can not withstand all the stress of the volume expansion of the negative electrode active material layer, plastic deformation occurs. Further, it is not clear how the cobalt plated layer or the cobalt-nickel alloy plated layer is formed on the surface of the copper foil, which will affect the characteristics of the battery.

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

According to a first aspect of the present invention, there is provided a negative electrode current collector copper foil for a lithium ion secondary battery, which is provided on a negative electrode for a lithium ion secondary battery,

When the negative electrode for a lithium ion secondary battery is provided,

A plastic deformation suppressing layer (plastic deformation suppressing layer) which is formed on at least one surface of the negative active material layer and suppresses plastic deformation due to volume change of the negative electrode active material layer,

A stress relaxation layer (stress relaxation layer) disposed between the plastic deformation suppression layer and the negative electrode active material layer for relaxing the stress due to volume change of the negative electrode active material layer

An anode current collecting copper foil for a lithium ion secondary battery is provided.

According to the second aspect of the present invention,

1. An anode current collecting copper foil for a lithium ion secondary battery, comprising a negative electrode active material layer formed on at least one surface thereof and provided on a negative electrode for a lithium ion secondary battery,

When the negative electrode for a lithium ion secondary battery is provided,

Wherein the anode active material layer is formed on at least one surface side of the anode active material layer and has a crystal structure with a small average particle diameter and a fine crystal grain,

And a crystal structure having crystal grains disposed between the small crystal structure layer and the negative active material layer and having an average grain size larger than that of the small crystal structure layer,

An anode current collecting copper foil for a lithium ion secondary battery is provided.

According to the third aspect of the present invention,

1. An anode current collecting copper foil for a lithium ion secondary battery, comprising a negative electrode active material layer formed on at least one surface thereof and provided on a negative electrode for a lithium ion secondary battery,

When the negative electrode for a lithium ion secondary battery is provided,

A rolled tissue layer formed on at least one side of the negative active material layer and including a rolled structure produced by rolling;

A recrystallized structure layer disposed between the rolled tissue layer and the negative electrode active material layer and including a recrystallized structure (recrystallized structure) generated by heat treatment at the time of forming the negative electrode active material layer,

An anode current collecting copper foil for a lithium ion secondary battery is provided.

According to the fourth aspect of the present invention,

Wherein the plastic deformation restraining layer and the stress relieving layer each include a different crystal structure,

The average grain size of crystal grains contained in the crystal structure of the stress relieving layer different from the crystal structure of the plastic deformation suppressing layer is larger than the average grain size of the crystal grains contained in the crystal structure of the plastic deformation suppressing layer

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery described in the first aspect.

According to the fifth aspect of the present invention,

The crystal structure included in the plastic deformation suppressing layer is a rolled structure produced by rolling processing,

The crystal structure other than the rolled structure included in the stress relieving layer is a recrystallization structure formed by heat treatment at the time of forming the negative electrode active material layer

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery described in (4).

According to the sixth aspect of the present invention,

When the negative electrode for a lithium ion secondary battery is provided,

And is formed in a rectangular shape,

In at least one of a cross section parallel to one side of the quadrangle and a cross section perpendicular to the cross section,

The area ratio of the area occupied by the recrystallization structure to the entirety of the predetermined cross section is more than 5% but less than 90%

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery as described in the third or fifth aspect.

According to the seventh aspect of the present invention,

Main ingredient of oxygen free copper

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery according to any one of the first to sixth aspects.

According to the eighth aspect of the present invention,

0.01% by mass or more and 0.20% by mass or less of Zr

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery according to any one of the first to seventh aspects.

According to the ninth aspect of the present invention,

There is provided a negative electrode current collecting copper foil for a lithium ion secondary battery according to any one of the first to eighth aspects,

The negative electrode active material layer formed on at least one surface of the negative electrode current collector copper foil for a lithium ion secondary battery and comprising at least one of Si and Sn;

And a tab lead connected to the negative electrode current collecting copper foil for the lithium ion secondary battery

A negative electrode for a lithium ion secondary battery is provided.

According to the tenth aspect of the present invention,

The negative electrode for a lithium ion secondary battery described in the ninth aspect,

A positive electrode for a lithium ion secondary battery,

A separator interposed between the negative electrode for the lithium ion secondary battery and the positive electrode for the lithium ion secondary battery,

A separator interposed between the negative electrode for the lithium ion secondary battery and the positive electrode for the lithium ion secondary battery,

A lithium ion secondary battery is provided.

According to the present invention, there are provided a negative electrode current collecting copper foil for a lithium ion secondary battery and a negative electrode current collecting copper foil for a lithium ion secondary battery excellent in charge-discharge cycle characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating the shape of a crystal structure to be provided in a negative electrode current collecting copper foil for a lithium ion secondary battery according to an embodiment of the present invention. FIG.
2 is a flowchart showing a manufacturing process of a negative electrode current collecting copper foil for a lithium ion secondary battery according to an embodiment of the present invention.
3 is a plan view of a negative electrode for a lithium ion secondary battery according to an embodiment of the present invention.
4 is a perspective sectional view of a lithium ion secondary battery according to an embodiment of the present invention.
5 is a reflection electron image of a negative electrode current collector copper foil for a lithium ion secondary battery according to Examples 1 to 3 and Comparative Example 1, which was observed by a scanning electron microscope on a section perpendicular to the rolling direction.
6 is a reflection electron image obtained by observing a cross section perpendicular to the rolling direction of a negative electrode current collector copper foil for a lithium ion secondary battery according to Comparative Examples 2 and 3 with a 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. In forming the negative electrode active material layer, for example, heat treatment is performed at 400 degrees for about 10 hours. At this time, the negative electrode current collecting copper foil is softened and easily plastic-deformed. The negative electrode current collecting copper foil which has been plastically deformed does not follow the shrinkage of the negative electrode active material layer and causes peeling or dislocation of the negative electrode active material layer. Therefore, for example, a rolled copper foil having high heat resistance (high heat resistance) and high proof strength (high resistance) is considered to be used as the negative electrode current collecting copper foil.

However, the inventors of the present invention have found that it is not sufficient to simply improve the heat resistance and proof stress of the negative electrode current collecting copper foil. That is, while the negative electrode active material layer repeatedly expands / contracts due to charge and discharge, even a negative current collecting copper foil with high strength can not withstand all of the stress and cracks may occur. If there is a groove-shaped defect or the like on the end of the negative current collector copper foil, it may be broken.

As a result of intensive studies, the inventors of the present invention have found that, in a negative electrode current collector copper having a predetermined layer structure (layer structure) when a negative electrode active material layer is formed on at least one side of the negative electrode for a lithium ion secondary battery, And that cracking or breakage of the negative electrode current collector copper foil can be suppressed.

That is, a predetermined layer structure of the negative electrode current collecting copper foil when it is provided on the negative electrode, for example, the plastic deformation suppressing layer formed on at least one surface side of the negative electrode active material layer and the stress It can be a relaxed layer. The plastic deformation suppressing layer is a layer that suppresses the overall plastic deformation of the negative electrode current collecting foil by the volume change of the negative electrode active material layer. The stress relieving layer is a layer for alleviating the stress due to volume change of the negative electrode active material layer. As a result, the negative electrode current collector copper exhibits the above-mentioned excellent effect.

It is conceivable that the layer having a function as the plastic deformation restraining layer and the stress relieving layer may be a combination of layers including different predetermined crystal structures (crystal structures), for example. As an example of another crystal structure, there can be mentioned, for example, a crystal structure in which grain sizes of crystal grains contained therein are different from each other.

That is, in this case, the average grain size of the crystal grains contained in the crystal structure of the stress relaxation layer, which is different from the crystal structure of the plastic deformation suppressing layer, is larger than the average grain size of the crystal grains contained in the crystal structure of the plastic deformation suppressing layer, . That is to say, the layer structure of each layer can be formed by, for example, a small crystal structure layer (small grain crystal structure layer) having at least one side of the anode active material layer and having a crystal structure with a small average grain size and fine crystal grains, (Large-grain crystal structure layer) including a crystal structure having crystal grains disposed between the anode active material layers and having an average particle size larger than that of the small crystal structure layers.

As described above, when the average grain size in the crystal structure is small and the crystal grains are relatively fine, it is a layer resistant to high-strength and plastic deformation. On the contrary, if the crystal grains are relatively large, the layer is soft and excellent in followability, thereby being a layer for relaxing the stress.

The crystal structure having fine crystal grains as described above is, for example, a rolled structure produced by rolling processing. As a crystal structure having relatively large crystal grains, for example, a recrystallized structure produced by a heat treatment at the time of forming the negative electrode active material layer is conceivable. That is, each layer, for example, a negative electrode active material layer is formed on at least one surface side, and a rolled tissue layer including a rolled structure formed by rolling processing, and a rolled structure layer disposed between the rolled tissue layer and the negative electrode active material layer and forming a negative electrode active material layer And a recrystallized structure layer including a recrystallized structure produced by heat treatment at the time of heat treatment.

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

In the present specification, the negative electrode current collecting copper foil refers to a state before a negative electrode for a lithium ion secondary battery is prepared in principle. At this time, the negative electrode current collecting copper foil may not have a predetermined layer structure as described above, unlike the state after being provided on the negative electrode. As a state before a predetermined layer structure, for example, there is a state in which only a rolled structure is mainly provided as a crystal structure. Therefore, in the present specification, the negative electrode current collector copper foil indicates a state of being constituted by a rolled structure as a main crystal structure.

However, in the present specification, the negative electrode current collecting copper foil may be provided after being provided in the negative electrode for a lithium ion secondary battery, that is, it may indicate that it has a predetermined layer structure. Specifically, there is a case where the negative electrode current collecting copper foil is in a state of having the plastic deformation suppressing layer and the stress relieving layer. Alternatively, the negative electrode current collecting copper foil may have a state of having a small grain structure layer and an opposite grain structure layer. Alternatively, there may be a case where the negative electrode current collecting copper foil is in a state of having the rolled tissue layer and the recrystallized tissue layer.

≪ One embodiment of the present invention &

(1) A schematic configuration of a 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 a negative electrode 1 for a lithium ion secondary battery according to the present embodiment. 4 is a perspective sectional view of the lithium ion secondary battery 50 according to the present embodiment.

As shown in Fig. 4, the lithium ion secondary battery 50 has a battery extrac- tion bottle 5 as a container filled with an electrolyte solution not shown in the figure. The battery extrapolation cylinder 5 is provided with a negative electrode 1 (hereinafter, simply referred to as a "negative electrode 1") for a lithium ion secondary battery having a tab lead 12 and a lithium An anode 2 for an ion secondary battery (hereinafter also simply referred to as " anode 2 ") is accommodated in a state in which the separator 3 is interposed therebetween.

3, the negative electrode 1 is made of a negative electrode current collecting copper foil 10 for a lithium ion secondary battery (hereinafter, simply referred to as "negative electrode current collecting copper foil 10") and a single- And an anode active material layer (11) formed on the anode active material layer. The tab lead 12 is directly connected to the exposed region 10s of the negative electrode current collector copper foil 10. Detailed configuration of the lithium ion secondary battery 50 and the cathode 1 for a lithium ion secondary battery will be described later.

(2) Negative current collecting copper foil for lithium ion secondary battery

Next, a negative electrode current collecting copper foil 10 for a lithium ion secondary battery according to an embodiment of the present invention, that is, a current collecting copper foil 10 provided in the negative electrode 1 and having a predetermined layer structure will be described. In the present embodiment, the predetermined layer structure to be provided in the negative electrode current collecting copper foil 10 is a re-crystallization structure which is formed by the rolling process produced by the rolling process and the heat treatment at the time of forming the negative electrode active material layer 11 .

The negative electrode current collector copper foil 10 is, for example, a rolled copper foil having a thickness of 20 m or less and formed in a long shape having a rolled surface as a main surface. For example, the long side direction (longitudinal direction) of the negative electrode current collector copper foil 10 is the rolling direction, that is, the extending direction at the time of rolling, and the short side direction is 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, for example, oxygen-free copper (OFC) is used. The copper alloy material contains zirconium (Zr) in an amount of, for example, 0.01 mass% or more and 0.20 mass% or less.

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 the element, for example, iron (Fe), tin (Sn), zinc (Zn), nickel (Ni), aluminum (Al) and the like are added in an amount of 1.0% by mass or more and 5.0% Zn, Ni, silicon (Si), chromium (Cr) or the like is added in an amount of 0.1% by mass or more and 1.0% by mass or less.

The negative electrode current collector copper foil 10 is configured so that the negative electrode active material layer 11 is formed on at least one surface thereof and is provided in the negative electrode 1 for a lithium ion secondary battery. As described above, the current-collecting copper foil 10, which is provided in the negative electrode 1 and not to have a predetermined layer structure, is provided with, for example, only a rolled structure.

The negative electrode current collector copper foil 10 has a structure in which a negative electrode active material layer 11 is formed on at least one side of the negative electrode 1 and a rolled tissue layer as a plastic deformation suppressing layer is formed between the rolled tissue layer and the negative electrode active material layer 11 And a recrystallized structure layer as a stress relaxation layer to be disposed. The rolled tissue layer is constituted, for example, to include a rolled structure and suppress plastic deformation due to volume change of the anode active material layer 11. [ Further, the recrystallized structure layer includes, for example, a recrystallized structure and is configured to alleviate the stress due to the volume change of the anode active material layer 11. [ The shape of each layer is illustrated in Fig.

1 is a schematic diagram illustrating the shapes of a rolled tissue layer 10p and a recrystallized structure layer 10r to be provided in the negative electrode current collecting copper foil 10 when the negative electrode 1 is provided. The schematic diagram of Fig. 1 shows a cross section parallel to the short side direction of the negative current collector copper foil 10. 1 shows an example in which a recrystallized structure layer 10r is formed on both sides of the rolled structure layer 10p.

The rolled structure contained in the rolled structure layer 10p is a crystal structure produced by rolling processing when the above-described copper alloy material is rolled to manufacture the negative electrode current collector copper foil 10. The rolled structure has relatively fine grains having an average grain size of, for example, 0.3 占 퐉 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 but less than 1.0 μm. As shown in Fig. 1, the crystal grains in the rolled structure are pressed against the pressing direction at the time of rolling, that is, the thickness direction of the negative electrode current collecting copper foil 10 in addition to the fine grains so that the grain shape is flat or needle- ). Such a crystal structure is characterized in that it has a high resistance and, for example, it is difficult to reach the plastic deformation by repeating the elastic deformation according to the volume change of the anode active material layer 11. [

The recrystallized structure contained in the recrystallized structure layer 10r can be obtained by forming the negative electrode active material layer 11 on the negative electrode current collecting copper foil 10 by the above heat treatment to form the negative electrode current collecting copper foil 10 Is a crystalline structure produced by recrystallization of a part of the rolled structure. The recrystallized structure has relatively large crystal grains having an average grain size of 3 mu m or more, for example. Alternatively, the range of the grain size of the crystal grains contained in the recrystallized structure is, for example, 1.0 μm or more and 10.0 μm or less. As shown in Fig. 1, the crystal grains in the recrystallized structure are composed of not only large grain size but also individual crystal grains in the form of equiaxed (or equiaxial) aggregates with almost no gap therebetween and are divided by relatively clear grain boundaries It has a mosaic pattern (patch shape). This crystal structure allows a certain extent of elongation due to the volume change of the negative electrode active material layer 11, so that a buffering action occurs between the negative electrode active material layer 11 and the rolled tissue layer 10p and also imparts softness to the negative electrode current collector copper foil 10.

The average grain size of the crystal grains contained in the rolled structure and the recrystallized structure was determined by the "quadrature method" of "new grain size crystal grain size test method" prescribed in JIS H0501 . That is, a value obtained from the number of crystal grains contained in a predetermined area in the crystal structure.

In the state where the recrystallized structure is provided, the ratio of the area occupied by the recrystallized structure to the entire cross section in the cross section perpendicular to the short side direction of the elongated negative electrode current collector copper foil 10, that is, perpendicular to the rolling direction is, for example, 5% And less than 90%. Alternatively, the area ratio may be 10% or more and 80% or less. In the case where a recrystallized structure is formed only on one surface of the negative electrode current collecting copper foil 10, the area ratio may be shifted to the lower limit within the range, for example. If the area ratio is satisfied, the recrystallized structure layer may contain a rolled structure as well as a recrystallized structure. In other words, the recrystallized structure layer may be a substantially homogeneous layer made of only a recrystallized structure, or may be a layer in which a rolled structure remains in an island shape in a recrystallized structure, or a layer in which a recrystallized structure is formed in an island shape in a rolled structure .

However, there is a tendency that similar crystal structures are arranged in the rolling direction, so that even if a sufficient amount of recrystallized structure is formed as a whole, the area ratio mentioned above does not necessarily satisfy the above-mentioned area ratio in the section parallel to the rolling direction .

(3) Manufacturing method of anode current collecting copper foil for lithium ion secondary battery

Next, a method for manufacturing the negative electrode current collecting copper foil 10 for a lithium ion secondary battery, that is, a method for manufacturing the current collecting copper foil 10, which is provided in the negative electrode 1 and has a predetermined layer structure, will be described with reference to Fig. 2 . 2 is a flowchart showing the manufacturing process of the negative electrode current collecting copper foil 10 according to the present embodiment.

(Copper alloy material preparing step (S10))

As shown in Fig. 2, first, an ingot (ingot) as a copper alloy material to be a raw material is prepared. Such an ingot is, for example, oxygen free copper, for example, 0.01 to 0.20 mass% of zirconium (Zr) is added as a copper material, and these ingots are melted and cast. The additive such as Fe, Sn, Zn, Ni, Al, Si and Cr may be appropriately added in addition to Zr in the above-mentioned predetermined concentration range.

(Hot rolling step (S20))

Next, the ingot is subjected to hot rolling to form a plate material. Further, it is preferable to perform a heat treatment for homogenizing the segregation occurring in the casting structure prior to the hot rolling step (S20).

(Repeating step (S30))

Subsequently, a cold rolling step (S31) and an annealing step (S32) are repeated a plurality of times (S30) for the plate subjected to hot rolling.

The cold rolling step (S31) is, for example, 50% or more in processing. Here, the processing degree is represented by TB = the thickness of the object to be processed (plate material of copper) before the cold rolling step (S31) and the thickness of the object to be processed after the cold rolling step (S31) (TB-TA) / TB] x 100.

In the annealing step (S32), annealing is applied to the plate material subjected to work hardening (work hardening) by cold rolling to anneal the plate material, thereby alleviating the work hardening. This is repeated a predetermined number of times to obtain a copper wire (copper wire) called " raw cloth ". When an additive or the like for adjusting the heat resistance is added to the copper material, the temperature condition of the annealing treatment is appropriately changed in accordance with the heat resistance of the copper material.

In the repeating step (S30), the annealing step (S32) during the repetition is called an " intermediate annealing step ". The annealing step (S32) performed immediately before the final cold rolling step (S40), which will be described later, is referred to as a "final annealing step" or a "raw sheet annealing step".

(Final cold rolling step (S40))

Next, a final cold rolling step (S40) is performed on the raw paper on which the repeated step (S30) has been performed to obtain a rolled copper foil having a predetermined thickness, for example, 20 占 퐉 or less. At this time, the degree of processing is set to, for example, 82% or more and 90% or less, so that the crystal grains in the raw paper are made finer and the work distortion is sufficiently accumulated to sufficiently develop the high-

As a result, high strength (grain refinement enhancement) due to fine crystal grains in the crystal structure occurs, and an effect of suppressing plastic deformation in the rolled structure layer 10p occurs. In addition, due to the processing strain (processing strengthening) accumulated in the rolled tissue layer 10p by rolling, the rolled tissue layer 10p has a higher strength and an effect of suppressing plastic deformation is further enhanced.

The raw paper that has undergone the above steps may be subjected to predetermined surface treatment such as roughening treatment and rust prevention treatment.

Thus, the negative electrode current collecting copper foil 10 for a lithium ion secondary battery constituted by a rolled structure is produced as a main crystal structure.

The state of the recrystallized structure produced by the heat treatment at the time of forming the negative electrode active material layer 11 to be described later is influenced by various conditions in the manufacturing process of the negative electrode current collector copper foil 10 described above. Concretely, for example, the processing degree in the final cold rolling step (S40), the temperature distribution of the rolling mill, the distortion rate and the distortion distribution, the concentration distribution of the additive elements and the impurity elements in the copper alloy material, And the precipitation state. Therefore, in order to obtain a desired recrystallized structure, these conditions are appropriately adjusted in the above-described manufacturing process.

Particularly, when Zr is contained as an additive, the phenomenon that the recrystallized structure is mainly generated only in the vicinity of the surface of the negative electrode current collector copper foil 10 is likely to be developed, and the above-described structure including the rolled structure layer and the recrystallized structure layer is easily obtained.

(4) Manufacturing method of negative electrode for lithium ion secondary battery

Next, a method of manufacturing the negative electrode 1 for a lithium ion secondary battery having the structure shown in Fig. 3 will be described. By performing this manufacturing method, the negative electrode current collecting copper foil 10 is provided in the negative electrode 1 and has a predetermined layer structure.

(Slurry application step)

First, a method of applying slurry to the negative electrode current collecting copper foil 10 and pressing it will be described. This step is carried out by using an apparatus such as an applicator for applying the slurry to the negative electrode current collecting copper foil 10 by a continuous line of a coil / twin / coil system, for example.

Specifically, for example, a slurry obtained by kneading a negative electrode active material, a binder solution and, if necessary, a conductive auxiliary agent is applied to one surface or both surfaces of the negative electrode current collector copper foil 10, For example, it is dried at 70 to 130 degrees for several minutes to several tens minutes.

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

(Heat treatment process)

Next, the negative electrode current collecting copper foil 10 on which the slurry is pressed is subjected to a heat treatment for a long time at a high temperature which is higher than the temperature of the thermoplastic region of the binder component, for example, by using an infrared ray heater or the like. Concretely, the heat treatment at 350 ° C or higher and 450 ° C or lower is performed for 1 hour to 16 hours. At this time, heat treatment is performed in a non-oxidizing (non-oxidizing) atmosphere such as nitrogen (N ₂ ) gas or argon (Ar) gas under vacuum (under reduced pressure). As a result, for example, a binder component comprising a precursor such as an imide resin is inserted into the concave and convex portions of the anode active material particle, and the imidization reaction proceeds and solidifies. Thus, a negative electrode active material layer 11 including a negative electrode active material and a binder such as imidized polyimide resin is formed on one surface or both surfaces of the negative electrode current collector copper foil 10.

Part of the crystal structure in the negative electrode current collecting copper foil 10 is recrystallized by such heat treatment to produce a recrystallized structure. As such recrystallization occurs, the processing strain generated during rolling is substantially eliminated, and the effect of stress relaxation by the recrystallized structure occurs. Also, since the relatively large crystal grains in the recrystallized structure allow stretching due to the volume expansion of the negative electrode active material layer 11, the effect of stress relaxation also occurs.

As described above, the negative electrode active material layer 11 is formed on at least one side and a rolling structure layer as a plastic deformation suppressing layer for suppressing plastic deformation due to volume change of the negative electrode active material layer 11 and a rolled structure layer as a rolled tissue layer and a negative electrode active material layer 11 And a recrystallized structure layer as a stress relaxation layer that relaxes the stress due to the 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 side of the negative electrode current collecting copper foil 10, a recrystallized structure layer is formed at least on the surface of the rolled tissue layer where the negative electrode active material layer 11 is formed. However, a recrystallized structure layer may be formed on both surfaces of the rolled tissue layer, including the surface side where the negative electrode active material layer 11 is not formed at this time.

When the negative electrode active material layer 11 is formed on both surfaces of the negative electrode current collecting copper foil 10, it is preferable that a recrystallized structure layer is formed on both surfaces of the rolled tissue layer. However, even if a recrystallized structure layer is formed only on one side of the rolled tissue layer at this time, a predetermined effect of relaxing the stress due to volume change of the negative electrode active material layer 11 is obtained.

In order to form a recrystallized structure layer only on the side where the negative electrode active material layer 11 is formed in the negative electrode current collector copper foil 10, for example, when the negative electrode active material layer 11 is formed on only one side, A method of performing the heat treatment in a state sufficiently lowered can be adopted. In such a low temperature, the temperature of the side where the negative electrode current collecting foil 10 is heated from the side where the negative electrode active material layer 11 is formed or the side where the negative electrode active material layer 11 is not formed is made lower than the other side, Conduct.

(Tap lead connecting step)

Next, a method of connecting the tab lead 12 to the negative electrode current collecting 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 surface or both surfaces. For example, the negative electrode current collecting copper foil 10, which is rectangularly divided along the rolling direction, has at least one anode active material layer And an exposed region 10s where the layer 11 is not formed. The tab lead 12 is welded to the exposed region 10s of the negative electrode current collecting copper foil 10 by, for example, welding in order to make electrical connection with the battery extrapolation cylinder 5 provided in the lithium ion secondary battery 50 .

That is, the exposed region 10s of the negative electrode current collecting copper foil 10 and the tab leads 12 made of, for example, Ni or Ni-plated copper are superimposed, and a predetermined pressing force and load energy are applied by, for example, The welding process is performed at a predetermined load time. Whereby the negative electrode current collector 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 having a rolled tissue layer and a recrystallized tissue layer, a negative electrode active material layer 11 formed on at least one surface or both surfaces of the negative electrode current collector copper foil 10, And a tab lead 12 connected to the tab lead 12. The negative electrode 1 for a lithium ion secondary battery is manufactured.

(5) Manufacturing method of lithium ion secondary battery

Next, a method of manufacturing the lithium ion secondary battery 50 will be described with reference to FIG.

First, a negative electrode 1 for a lithium ion secondary battery and a positive electrode 2 for a lithium ion secondary battery are stacked with a separator 3 interposed therebetween, and wound around a winding core not shown in the drawing, . The positive electrode 2 is composed of a positive electrode current collecting metal foil for a lithium ion secondary battery and a positive electrode active material layer formed on both surfaces of the positive electrode current collecting foil (none of which are shown in the drawing), tab leads 22 connected to the positive electrode current collecting foil . The metal constituting the positive collector metal foil is, for example, lithium (Li), aluminum (Al) or other metals. The positive electrode active material layer is made of, for example, a metal complex oxide containing Li. The separator 3 is made of, for example, porous resin.

Next, the lower insulation plate and the winding body 4, which are not shown in the drawing, are received in order in the battery extempter cylinder 5 as a container. Subsequently, a mandrel (core) not shown in the drawing is inserted into the center of the winding body 4, and the upper insulating plate is accommodated in the battery extrapolation cylinder 5, and then the groove 6 is formed in the battery extrapolation cylinder 5 . Thereafter, drying is performed to remove moisture in the battery extrac- tion bottle 5. When the battery extrapolation cylinder 5 is sufficiently dried, an electrolyte solution not shown in the drawing is injected. Next, the gasket 7 is mounted in the vicinity of the groove 6 of the battery extrapolation cylinder 5, and the tab lead 12 of the cathode 1 is inserted into the battery extrapolation cylinder 5 and the tab lead of the anode 2 22 are welded to the terminal 8t of the cap 8 and the cap 8 is crimped to the battery extrapolation cylinder 5 to seal the electrolyte.

As described above, the negative electrode 1 for a lithium ion secondary battery and the positive electrode 2 for a lithium ion secondary battery in which the separator 3 is interposed are accommodated, and a lithium ion The secondary battery 50 is manufactured.

Here, the cylindrical lithium ion secondary battery 50 shown in FIG. 4 is described as an example, but the lithium ion secondary battery may have other shapes such as a rectangular shape or a laminate shape. Accordingly, the negative electrode 1 and the positive electrode 2 can adopt various forms such as the winding type or the lamination type as described above.

The negative electrode current collecting copper foil for a lithium ion secondary battery when it is provided on a negative electrode for a lithium ion secondary battery is mainly a rectangle separated in parallel along the rolling direction. The term " rectangle " refers to a rectangular shape including a square shape, and also includes a shape of an elongated shape wound in the form of a roll.

For the negative electrode current collector copper foil 10 cut out in such a rectangular shape, the rolling direction may not be particularly specified in confirming the presence or absence (presence or absence) or existence ratio (area ratio in cross section) of the recrystallized structure. As described above, similar crystal structures are arranged in the rolling direction. Therefore, for example, in the case where the recrystallized structure is dotted in the shape of an island in the rolled tissue layer, there may be a case in which the recrystallized structure deviates from the finished cross section in parallel with the rolling direction. In this case, even though a sufficient recrystallized structure is formed, no recrystallized structure is observed at all.

However, even if the rolling direction can not be specially designated, if observing is made for two cross sections of a cross section parallel to one side of the rectangular cross section of the negative current collecting copper foil 10 and a cross section orthogonal to the cross section, Information of a cross section perpendicular to the direction is obtained. The rolled structure and the recrystallized structure can be determined by the average grain size and shape of the crystal grains in each crystal structure, the fibrous structure, the mosaic structure, and the like.

However, as described above, it may be considered that the recrystallized structure layer may have a deviation depending on the place, for example, dotted in the shape of an island 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 over at least 50 mu m in the width direction of the cross section.

In the negative electrode current collector copper foil 10 of the present embodiment, there is a recrystallized structure in at least one of the two sections, and the area ratio of the area occupied by the recrystallized structure to the entire predetermined cross section is, for example, more than 5% Less than 90% or 10% or more and 80% or less. In the case where the recrystallized structure is formed only on one side, it may be a value which is shifted to the lower limit within the range.

Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, but can be variously changed without departing from the gist of the present invention.

(6) Effects of the present embodiment

According to the present embodiment, one or a plurality of effects shown below can be obtained.

(a) In other words, in this embodiment, when the negative electrode current collecting copper foil 10 is provided on the negative electrode 1, a rolled tissue layer 10p as a plastic deformation restraining layer formed on at least one surface of the negative electrode active material layer 11, And a recrystallized structure layer 10r as a stress relaxation layer disposed between the rolled structure layer 10p and the negative electrode active material layer 11. [

The rolled tissue layer 10p having a high strength due to grain refinement or processing strengthening repeatedly undergoes elastic deformation while resisting the stress due to volume change of the negative electrode active material layer 11 to suppress plastic deformation of the negative electrode current collector copper foil 10 can do. Therefore, it is possible to suppress the peeling or dislocation of the negative electrode active material layer 11 from the negative electrode current collector copper foil 10. It is possible to suppress the occurrence of an internal short circuit in the lithium ion secondary battery 50 because the negative electrode current collector copper foil 10 is stretched or wrinkled.

The recrystallized structure layer 10r having large crystal grains allowing substantially no processing strain and also allowing elongation to follow the change in the volume of the negative electrode active material layer 11 relaxes the stress so that the negative electrode active material layer 11 and the rolled- (10p). ≪ / RTI > Therefore, cracks can be generated in the negative electrode current collecting copper foil 10, or the negative current collecting copper foil 10 can be prevented from being broken or broken.

(b) In the present embodiment, each layer having a function different from that of suppressing plastic deformation and stress relaxation is formed in the negative electrode current collecting copper foil 10. Accordingly, in order to impart these different functions, it is not necessary to add a redundant structure to the negative electrode current collecting copper foil 10, for example, and the structure of the negative current collecting copper foil 10 and the negative electrode 1 can be simplified.

(c) In the present embodiment, the rolled tissue layer 10p is a layer including a rolled structure produced by rolling processing, and the recrystallized structure layer 10r is formed by heat treatment at the time of forming the negative electrode active material layer 11 Lt; RTI ID = 0.0 > recrystallized < / RTI > As a result, these layers can be relatively easily formed without significantly changing existing processes or significantly increasing the number of processes.

(d) In this embodiment, the recrystallized structure is formed by the heat treatment at the time of forming the negative electrode active material layer 11. As a result, the step of forming the recrystallized structure can be used also as the step of forming the negative electrode active material layer 11, thereby further improving the efficiency.

(e) In this embodiment, the area ratio of the area occupied by the recrystallized structure to the entire cross section in the cross section perpendicular to the rolling direction is more than 5% but less than 90%. The area ratio of the area occupied by the recrystallized structure is, for example, more than 5%, so that the stress can be sufficiently relaxed by the recrystallized structure layer 10r. In addition, since the area ratio is less than 90%, for example, elongation along the charge / discharge cycle occurs in the negative electrode current collecting copper foil 10, so that peeling of the negative electrode active material layer 11 and occurrence of internal short circuit can be suppressed.

(f) In the present embodiment, observations are made on two cross sections of a cross section parallel to one side of the negative current collecting copper foil 10 cut in a rectangular shape and a cross section orthogonal to the cross section. Thus, it is possible to determine whether or not a desired recrystallized structure is formed even in a situation where it is difficult to specify the rolling direction in the negative electrode current collecting copper foil 10 after cutting.

(g) In the present embodiment, the negative electrode current collecting copper foil 10 is constituted by a rolled copper foil containing oxygen-free copper as a main component. As described above, for example, by using a material which is higher in heat resistance and high resistance than tough pitch copper or electrolytic copper, the plastic deformation of the negative electrode current collector copper foil 10 is further suppressed and the detachment of the negative electrode active material layer 11 .

(h) In the present embodiment, the negative electrode current collector copper foil 10 contains Zr in an amount of 0.01 mass% or more and 0.20 mass% or less. As a result, the phenomenon that the recrystallized structure is generated only mainly in the vicinity of the surface of the negative electrode current collector copper foil 10 is likely to occur, and the configuration of the present embodiment including the rolled structure layer 10p and the recrystallized structure layer 10r is easily obtained. In addition, solid solution strengthening is caused by solid solution of Zr in Cu which is a base material, so that the strength of the entire negative electrode current collector copper foil 10 can be improved.

(i) In the present embodiment, the degree of processing in the final cold rolling step (S40) is 82% or more and 90% or less. As a result, the crystal grains in the raw paper are made fine and the processing distortion is sufficiently accumulated, so that the rolling structure of high strength can be sufficiently developed. Further, since the degree of processing is suppressed to 90% or less, the area ratio occupied by the recrystallized structure at the time of heat treatment can be suppressed to, for example, less than 90%.

[Example]

Various evaluation results of the negative electrode current collecting copper foil for a lithium ion secondary battery according to the embodiment of the present invention will be described below.

(1) Production of anode current collecting copper foil

First, the negative electrode current collecting copper foils of Examples 1 to 3 and Comparative Examples 1 to 3 were produced according to the procedure described below.

Concretely, HCL02Z (Cu-Zr) foil having a thickness of 12 μm (containing 0.02 mass% of Zr in the HCL copper alloy (HCL registered trademark) of Hitachi Electric Wire Co., Ltd. which is a rolled copper foil made of oxygen- Impurities), and the rolling conditions and the like were variously changed within the range in which the same configuration as that of this configuration was obtained, thereby obtaining the negative electrode current collector copper foils of Examples 1 to 3. Further, the negative electrode current collecting copper foil according to Comparative Example 1 was prepared by varying the rolling conditions and the like so as to include a range deviating from such a configuration. In addition, a tough pitch copper (TPC) foil (Cu purity of 99.9 mass%) of 12 μm thickness manufactured by Hitachi Cable, Ltd. was used as Comparative Example 2, and a 10 μm thick electrolytic foil was used as Comparative Example 3.

As an example of the degree of processing in the final cold rolling step, the degree of processing in Example 2 is 88%.

(2) Measurement of negative electrode current collector copper foil

Next, various measurements were made on these negative current collecting copper foils.

First, these negative electrode current collecting copper foils were subjected to a heat treatment at 400 DEG C for 10 hours, and then a cross section perpendicular to the rolling direction was observed with a scanning electron microscope to obtain a reflection electron image (reflected electron image). This heat treatment condition mimics the heat treatment condition for forming the negative electrode active material layer.

In addition, a negative active material layer was actually formed on one side of the negative electrode current collecting copper foil before the heat treatment and various measurements were made.

(PI) varnish (PI precursor, N-methylpyrrolidone (commercially available from Nippon Kayaku Co., Ltd.) as a binder) was used as an anode active material, silicon oxide (SiO) powder available from Osaka Titanium Technology Co., Ltd., acetylene black was used as a conductive auxiliary, (NMP) solution) was used. The slurry was prepared by kneading for 1 hour by a kneader manufactured by Shinki, Inc. under the conditions of SiO 2: acetylene black: polyimide = 80: 5: 15 at a mass mixing ratio excluding solvent. This was coated on one side of the negative current collector copper foil using an applicator and dried. Then to 400 degrees the maximum temperature was heated under 10 hours, and nitrogen (N ₂₎ atmosphere.

As a result, a negative active material layer having a thickness of 15 占 퐉 was formed on one surface of the negative electrode current collecting copper foil.

Next, in a glove box in an argon (Ar) gas atmosphere, an electrolytic solution LIPASTE-EDMC / PF1 manufactured by Tomiyama Chemical Industry Co., Ltd. was placed in a glass beaker. Further, a negative electrode current collector copper foil having a negative electrode active material layer and a metallic lithium (Li) plate were immersed (immersed) in an electrolytic solution. In this state, a charge and discharge test was conducted using a battery charge / discharge device HJ-1001 SM8A manufactured by Bokuto Seiko Co., Ltd. Specifically, 1 C discharge was performed with 0 V to 1 V (pair Li / Li +), and the battery was discharged (rest) for 20 minutes, discharged at the same time as 1 C, and stopped (rested) for 20 minutes. After 50 cycles, the adhered state of the negative electrode active material layer and the deformation of the negative current collector copper foil were observed.

Separately, the anode current collecting copper foil having the above-described anode active material layer formed on one surface thereof was punched into a circle of ² cm ² . This circular anode current collecting copper foil was used as a negative electrode, and a metal Li plate was used as an anode to assemble a monopolar cell with a separator manufactured by Celgard Co., Ltd. interposed therebetween. The cell used was HS cell manufactured by BOSEI CO., LTD. As the electrolytic solution, electrolyte LIPASTE-EDMC / PF1 manufactured by Tomiyama Chemical Industries Co., Ltd. was used. The assembling work was carried out in a glove box in an Ar gas atmosphere. A cycle test of 100 cycles was carried out under the same charge and discharge conditions as above to measure the discharge capacity retention rate. The cell after the test was disassembled and the shape of the electrode was visually observed.

(3) Evaluation result of anode current collecting copper foil

5 (a) to 5 (d) show the reflection electron images of the section perpendicular to the rolling direction in the negative electrode current collector copper foils according to Examples 1 to 3 and Comparative Example 1 after the heat treatment. 6 (a) and 6 (b) show the reflection electron images of the section perpendicular to the rolling direction in the negative electrode current collector copper foils of Comparative Examples 2 and 3 after the heat treatment.

As shown in Fig. 5, in Examples 1 to 3 and Comparative Example 1 composed of a rolled copper foil using oxygen-free copper as a base material, a recrystallized structure in which the crystal structure of the surface of the current collecting copper foil greatly grows appears. Also, a thin flat rolled structure appears near the center in the thickness direction.

From the reflectance electron images of FIGS. 5 and 6, the area ratio of the area occupied by the recrystallized structure to the entire cross section in the cross section perpendicular to the rolling direction was determined, 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. The area ratios in Comparative Examples 2 and 3 were all 100%.

Next, Table 1 shows the results of observation 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 current collector copper foil. In the table, " adhesion state of the active material layer " indicates good, & cir & indicates a state in which slight peeling occurs, and X is mostly peeled off. In the results of " determination " based on the adhesion state of the negative electrode active material layer and the deformation of the negative electrode current collecting copper foil, " Good "

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

If the negative electrode current collecting copper foil is not sufficiently left in the negative electrode current collecting copper foil, plastic deformation of the negative electrode current collecting foil is caused to cause peeling of the negative electrode active material layer and internal short circuit in the lithium ion secondary battery.

On the other hand, in Examples 1 to 3 where the area ratio of the area occupied by the recrystallized structure was 75%, 53%, and 10%, the adhesion of the negative electrode active material layer was good. Also, no deformation of the negative current collecting copper foil was observed. It is considered that the recrystallized structure relaxes the stress due to the volume change of the negative electrode active material layer and the rolling structure suppresses the deformation of the negative electrode current collecting copper foil. As a result, it has been found that good results can be obtained when the area ratio of the area occupied by the recrystallized structure is within a predetermined range.

Next, the measurement values of the discharge capacity retention ratios of Example 2 and Comparative Example 2 and the visual observation results of the electrode shape are shown in Table 2 below. In the table, " Good " was determined as " Good " and " Good " was determined as " Bad "

As shown in Table 2, when the area ratio of the area occupied by the recrystallized structure is within a predetermined range, it can be seen that a high discharge capacity retention rate is provided. It can also be seen that deformation of the electrode is not occurring.

1: cathode for lithium ion secondary battery
2: anode for lithium ion secondary battery
3: Separator
4:
5: Battery extrapolator (container)
6: Home
7: Gasket
8: Cap
8t: terminal
10: Negative current collecting copper foil for lithium ion secondary battery
11: Negative electrode active material layer
12, 22: tab lead
50: Lithium ion secondary battery

Claims (10)

A negative electrode current collecting copper foil for a lithium ion secondary battery, comprising a negative electrode active material layer (negative electrode active material layer) formed on at least one surface thereof and provided on a negative electrode for a lithium ion secondary battery,
When the negative electrode for a lithium ion secondary battery is provided,
A plastic deformation suppressing layer (plastic deformation suppressing layer) which is formed on at least one surface of the negative active material layer and suppresses plastic deformation due to volume change of the negative electrode active material layer,
And a stress relieving layer (stress relaxation layer) disposed between the plastic deformation restraining layer and the negative active material layer and mitigating a stress due to volume change of the negative electrode active material layer
Respectively,
Wherein the plastic deformation restraining layer and the stress relieving layer each include a different crystal structure,
The average grain size of crystal grains contained in the crystal structure of the stress relieving layer different from the crystal structure of the plastic deformation suppressing layer is larger than the average grain size of the crystal grains contained in the crystal structure of the plastic deformation suppressing layer
Wherein the negative electrode collector copper foil for a lithium ion secondary battery is characterized in that:
The method according to claim 1,
The crystal structure included in the plastic deformation suppressing layer is a rolled structure produced by rolling processing,
A crystal structure other than the rolled structure is included in the stress relieving layer, and the crystalline structure is a recrystallization structure formed by a heat treatment at the time of forming the negative electrode active material layer
Wherein the negative electrode collector copper foil for a lithium ion secondary battery is characterized in that:
3. The method of claim 2,
When the negative electrode for a lithium ion secondary battery is provided,
And is formed in a rectangular shape,
In at least one of a cross section parallel to one side of the quadrangle and a cross section perpendicular to the cross section,
The area ratio of the area occupied by the recrystallization structure to the entirety of the predetermined cross section is more than 5% but less than 90%
Wherein the negative electrode collector copper foil for a lithium ion secondary battery is characterized in that:
3. The method according to claim 1 or 2,
Wherein the negative electrode collector copper foil for lithium ion secondary batteries contains oxygen free copper.
3. The method according to claim 1 or 2,
And 0.01 to 0.20% by mass of Zr in the negative electrode collector.
A negative electrode current collecting copper foil for a lithium ion secondary battery according to claim 1 or 2,
The negative electrode active material layer formed on at least one surface of the negative electrode current collector copper foil for a lithium ion secondary battery and comprising at least one of Si and Sn;
And a tab lead connected to the negative electrode current collecting copper foil for the lithium ion secondary battery
And a negative electrode for a lithium ion secondary battery.
A negative electrode for a lithium ion secondary battery according to claim 6,
A positive electrode for a lithium ion secondary battery,
A separator interposed between the negative electrode for the lithium ion secondary battery and the positive electrode for the lithium ion secondary battery,
A negative electrode for a lithium ion secondary battery and a positive electrode for a lithium ion secondary battery in which the separator is interposed,
And a lithium ion secondary battery. delete delete delete

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