JP2014032929A - Copper foil for current collector and negative electrode collector for lithium ion secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a current collector, capable of satisfying both improvement in adhesion with an active material layer and improvement in bondability with an Ni tab lead, and a negative electrode collector for a lithium ion secondary battery using the copper foil for a current collector.SOLUTION: In a negative electrode collector for a lithium ion secondary battery, an active material layer 17 is formed on a surface of a rolled copper foil 11. The rolled copper foil 11 has a surface on which roughened particles 15 each comprising a copper roughened plating layer and a chromium based coating are formed. The roughened particles have an average particle size of 0.5 μm or more and less than 1.0 μm, and roughened particles 15 having a particle size of 0.2 μm or more and less than 1.5 μm exist 100 particles or more and less than 1,000 particles per 100 μm.

Description

  The present invention relates to a copper foil for a current collector using a rolled copper foil, and a negative electrode current collector for a lithium ion secondary battery using the same.

  With the widespread use of portable devices such as mobile phones and laptop computers, the demand for secondary batteries that are small, have high capacity, and can be repeatedly charged is increasing. In particular, lithium ion secondary batteries are light and have a high energy density per unit weight, making them ideal as power sources for portable devices, and demand growth is expected.

As shown in Patent Documents 1 to 4, the lithium ion secondary battery includes a positive electrode, a negative electrode, a separator that is interposed between the positive electrode and the negative electrode, and insulates both, and lithium (Li ⁺ ) between the positive electrode and the negative electrode. It is mainly composed of an electrolyte solution that allows ions to move.

  The negative electrode includes, for example, a negative electrode active material containing a negative electrode active material such as carbon-based, Si-based (Patent Document 2), Sn-based (Patent Document 3) on a copper foil for a collector using a rolled copper foil as a base material. It is comprised from the negative electrode collector which formed the material layer. The positive electrode is composed of a positive electrode current collector in which a positive electrode active material layer such as lithium cobalt oxide is formed on an aluminum foil or the like.

  After these negative electrode current collectors, separators, and positive electrode current collectors are stacked in order, and a predetermined number of turns are wound, connection terminals (tab leads) for inputting and outputting power to the negative electrode current collector and the positive current collector are welded. The lithium ion secondary battery is formed by being housed in a battery container, injecting an electrolyte solution into the battery container and sealing it.

  Properties required for a negative electrode current collector for lithium ion secondary batteries based on copper foil are (1) adhesion between the negative electrode active material layer and the copper foil, and (2) bonding between the copper foil and the Ni tab lead. There is sex.

  As for (1), there is a method in which roughening particles are deposited on a copper foil to perform surface treatment for forming irregularities to give an anchor effect (Patent Document 2). Regarding (2), there is a method of providing an effect by forming a chromium-based film on the surface of the copper foil (Patent Document 4).

JP 2004-63344 A JP 2002-83594 A JP 2000-243396 A JP 2001-273904 A

  Thus, in constituting the lithium ion secondary battery negative electrode current collector, the adhesion strength between the copper foil and the negative electrode active material layer is highly important. According to conventional knowledge, when using rolled copper foil as a base material, the surface of the rolled copper foil is used to improve the adhesion between the negative electrode active material layer (hereinafter referred to as the active material layer) and the rolled copper foil. It has been considered preferable that the roughened particles provided on the surface have a large particle size.

  However, even if the particle diameters of the roughened particles forming the unevenness are substantially the same, if the number of roughened particles is too small, or if the number of roughened particles is too large, the adhesion is reduced. End up. This is thought to be because the size of the particles of the active material is significantly different from the size of the roughened particles provided on the copper foil, but these relationships are complex and an optimal relationship has not yet been found.

  In addition, the demand for stronger bondability between copper foil and Ni tab lead is increasing in recent years, and it is possible to obtain some strength by forming a chromium-based film on the copper foil, but it is still improved There is room for.

  Therefore, the object of the present invention is to solve the above-mentioned problems and satisfy both the improvement of the adhesion between the active material layer and the current collector copper foil and the improvement of the bondability between the negative electrode current collector copper foil and the Ni tab lead. An object of the present invention is to provide a copper foil for a current collector and a negative electrode current collector for a lithium ion secondary battery using the same.

In order to achieve the above object, according to the first aspect of the present invention,
In the copper foil for current collector that becomes the negative electrode current collector for the lithium ion secondary battery by providing the active material layer,
Rolled copper foil,
Provided on the rolled copper foil, and comprising at least a roughened copper plating layer and a chromium-based film, and roughened particles,
The roughened particles have an average particle size of 0.5 μm or more and less than 1.0 μm, and there are 100 or more and less than 1000 roughened particles of 0.2 μm or more and less than 1.5 μm per 100 μm ^2. A copper foil for a current collector is provided.

According to a second aspect of the invention,
A copper foil for a current collector according to a first aspect is provided, wherein the rolled copper foil is made of oxygen-free copper containing 0.015 mass% or more and 0.030 mass% or less of Zr.

According to the third aspect of the present invention, between the copper roughening plating layer and the chromium-based film,
A copper foil for a current collector according to the first or second aspect is provided, in which a nickel-cobalt alloy plating thin film of 5 μg / cm ² or more and less than 80 μg / cm ² and a zinc plating thin film are sequentially provided.

  According to a fourth aspect of the present invention, the current collector copper according to any one of the first to third aspects, wherein a base copper plating layer is provided between the rolled copper foil and the copper roughening plating layer. A foil is provided.

  According to a fifth aspect of the present invention, there is provided the current collector copper foil according to any one of the first to third aspects, wherein the chromium-based film is a chromate-treated layer.

  According to the 6th aspect of this invention, the negative electrode electrical power collector for lithium ion secondary batteries which provides an active material layer in the said copper foil for electrical power collectors is provided.

According to a seventh aspect of the present invention, there is provided a method for producing a current collector copper foil according to the first to fourth aspects,
The current density during plating for forming the copper roughening plating layer is 35 A / dm ² or more and 45 A / dm ² or less, the plating time is 1 sec or more and 50 sec or less, and the plating water temperature is 15 ° C. or more and 50 ° C. or less. It is a manufacturing method of the copper foil for electrical power collectors used.

In the present invention, the average particle diameter of the roughened particles formed on the rolled copper foil is 0.5 μm or more and less than 1.0 μm, and the roughened particles having a particle diameter of 0.2 μm or more and less than 1.5 μm are 100 per 100 μm ^2. By setting the number to at least 1,000, it is possible to improve the adhesion between the active material layer and the copper foil, and it is possible to improve the bondability with the Ni tab lead by applying chromate treatment to the surface.

It is sectional drawing which shows one Embodiment of the copper foil for collectors used for the negative electrode collector for lithium ion secondary batteries of this invention. It is principal part sectional drawing which shows one Embodiment of the negative electrode collector for lithium ion secondary batteries of this invention formed using the copper foil for collectors of FIG. Welding with Ni tab leads to copper foils for current collectors of Comparative Examples 1-1 to 1-3, Examples 1-1 to 1-12, and Comparative Examples 2-1 to 2-3 It is a figure which shows the relationship of intensity | strength. Comparative Example I (without the base copper plating layer and copper roughening plating layer), Comparative Example II (with the base copper plating layer and copper roughening plating layer and having an average particle size of 2.0 μm), and Example I (base copper) It is a figure which shows the microscope picture which shows the surface structure of the copper foil for collectors with a plating layer and a copper roughening plating layer, and an average particle diameter of 0.6 micrometer. It is the schematic of the peeling test which evaluates the adhesiveness of the copper foil for collectors, and an active material layer.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

The present invention provides a copper foil for a current collector, which becomes a negative electrode current collector for a lithium ion secondary battery by providing an active material layer, a rolled copper foil, and a copper roughening provided in order on the rolled copper foil Roughened particles comprising a plated layer and a chromium-based film, and the roughened particles have an average particle size of 0.5 μm or more and less than 1.0 μm and 0.2 μm or more and less than 1.5 μm Is a copper foil for a current collector in which 100 or more and less than 1000 are present per 100 μm ² .

  FIG. 1 shows a cross section of a current collector copper foil 10 according to an embodiment of the present invention. The copper foil 10 for current collectors is a base copper plating layer 12 on the surface of a rolled copper foil 11 made of OFC (oxygen-free copper), a dilute alloy based on OFC, or TPC (tough pitch copper). A copper roughening plating layer 13 is provided on the layer 12, and a treatment layer 14 is provided on the copper roughening plating layer 13. The treatment layer 14 includes a nickel-cobalt alloy plating thin film 14a, a galvanization thin film 14b, and a chromate treatment layer 14c.

  The copper roughening plating layer 13 and the treatment layer 14 (that is, the nickel-cobalt alloy plating thin film 14a, the zinc plating thin film 14b, and the chromate treatment layer 14c) form the roughening particles 15. Individual particles forming the copper roughening plating layer 13 are provided so as to be covered with a thin treatment layer 14 of the order of several tens of nanometers. For this reason, it is mainly the copper roughening plating layer 13 that determines the shape and dimensions of the roughening particles 15. The base copper plating layer 12, the nickel-cobalt alloy plating thin film 14a, and the zinc plating thin film 14b may not be provided.

  The interval between the particles forming the roughened copper plating layer need not be uniform. Further, some of the particles may overlap each other. Each layer constituting the treatment layer 14 may not completely cover the bottom of the concave space formed by the at least three particles formed thereunder. That is, it is only necessary to cover at least the vicinity of the top of the convex portion of the particle.

  FIG. 2 shows a schematic view of one embodiment of the negative electrode current collector of the present invention. An active material layer 17 is formed in close contact with the above-described current collector copper foil 10 to form a negative electrode current collector 20 for a lithium ion secondary battery (hereinafter simply referred to as a negative electrode current collector 20). Note that the size of each component is as described later, and in particular, it should be noted that the scale of the negative electrode active material 16 is significantly different from other scales.

  The active material layer 17 is formed including the negative electrode active material 16. A slurry is formed by dissolving, dispersing, and mixing the negative electrode active material 16 and a binder material 18 (hereinafter also simply referred to as “binder”) that holds the negative electrode active material 16 on the roughened particles 15. The Then, this slurry is coated on the roughened particles 15, and the active material layer 17 is formed by evaporating the solvent by drying at a high temperature for a long time using, for example, an infrared heating furnace. Is done.

  As the negative electrode active material 16, for example, particles of carbon (C) -based materials such as graphite and hard carbon, Sn-containing materials, Si-containing materials, metal composite oxides, lithium nitride metal compounds, and the like can be used. By forming the active material layer 17 using such a material, the capacity of the lithium ion secondary battery can be further increased. The diameter of the particles used as the negative electrode active material 16 is, for example, several μm to several tens of μm.

  As the binder material 18, various materials can be used as long as they are used as a binder material for a lithium ion secondary battery. Specifically, for example, imide resins such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyimide (PI), and the like can be used. The particle diameter of the binder material 18 is several tens nm to several hundreds nm, and the apparent aggregate diameter when used in the negative electrode current collector is several hundred nm to several tens μm.

  As the solvent, for example, a substance that is liquid at normal temperature (20 ° C.) and normal pressure and has a boiling point of 50 to 400 ° C. can be used. Specifically, for example, water, N-methylpyrrolidone, or the like can be used depending on the type of the binder substance.

  It is advisable to add as much negative electrode active material 16 as possible to the slurry and to reduce the proportion of the binder material 18 in the slurry. Thereby, the capacity | capacitance of a lithium ion secondary battery can be enlarged more. In addition to the above-described negative electrode active material 16, binder material 18, and solvent, for example, a conductive aid, a thickener, a binding aid, a viscosity modifier, and the like may be added to the slurry.

In the present invention, the roughened particles 15 have an average particle diameter of 0.5 μm or more and less than 1.0 μm, and 100 or more roughened particles 15 having a particle diameter of 0.2 μm or more and less than 1.5 μm per 100 μm ^2. Adhesion with the negative electrode active material 16 can be improved by having less than 1,000. As described above, the roughened particles 15 are composed of the copper roughened plated layer 13 and the treated layer 14 (nickel-cobalt alloy plated thin film 14a, galvanized thin film 14b, and chromate treated layer 14c). However, the layer between the copper roughening plating layer 13 and the chromate treatment layer 14c may not be provided, and other metals may be appropriately employed. Since the treatment layer 14 covers the particles formed by the copper roughening plating layer 13, the average particle diameter of the roughening particles and the number of particles satisfying each dimension are those of the particles forming the copper roughening plating layer. It becomes almost the same numerical value.

The amount of nickel-cobalt alloy related to the nickel-cobalt alloy plating thin film is 5 μg / cm ² or more and less than 80 μg / cm ² so that the welding strength between the current collector copper foil 10 and the Ni tab lead can be improved. It is a thing.

  Hereinafter, the reason why the adhesiveness between the active material layer 17 of the present invention and the copper foil 10 for current collector and the bondability with the Ni tab lead are improved will be described.

  As described above, regarding the dimensions, the average particle diameter of the roughened particles 15 is 0.5 μm or more and less than 1.0 μm, the diameter of the particles of the negative electrode active material 16 is several μm to several tens of μm, and the aggregate of particles of the binder material 18 The diameter is from several hundred nm to several tens of μm. A part of the binder material 18 enters a concave space formed between three or more adjacent roughened particles 15 and covers the roughened particles 15.

Although it is desirable that the binder material 18 penetrates to the bottom of the concave space, the binder material 18 does not have to be penetrated in all the concave spaces, and may be, for example, about half the height of the roughened particles 15. The negative electrode active material 16 has a particle size larger than that of the roughened particles 15 and cannot directly enter the concave space formed between the roughened particles 15, but the roughened particles 15 may be introduced via the binder material 18. The copper foil 10 for current collector can be bound. In order to make it easier for the binder material 18 to enter the concave space formed by the roughened particles 15, the average particle size is 0.5 μm or more and less than 1.0 μm according to the diameter of the aggregate of the binder material 18, and can 1.5μm less roughening particles over 0.2μm is within the range of 100 or more than 1000 per ² 100 [mu] m, to adjust the size of the roughening particles 15.

  The active material layer 17 in FIG. 2 includes a binder material 18 and a negative electrode active material 16 one by one. However, a binder, a binder, a conductive agent, a thickener, and the like are randomly added as necessary. It may be laminated while being interposed.

Thus, the structure of the roughening particles 15, by roughening particles 15 of particle size of less than than 0.2 [mu] m 1.5 [mu] m are present fewer than 1000 ² per 100 or more 100 [mu] m, adhesion between the anode active material 16 Can be improved.

First, after degreasing and pickling treatment are performed on the rolled copper foil 11, the base copper plating layer 12 is formed by applying the base copper plating in an acidic copper plating bath mainly composed of copper sulfate and sulfuric acid. Then, the copper plating bath has a current density of 35 A / dm ² or more and 45 A / dm ² or less, a plating time of 1 sec or more and 10 sec or less, and a plating bath temperature of 15 ° C. or more and 50 ° C. or less). An electroplating layer 13 is formed. Thereby, the average particle diameter of the roughened particles 15 is 0.5 μm or more and less than 1.0 μm and has 100 or more and less than 1000 roughened particles 15 having a particle diameter of 0.2 μm or more and less than 1.5 μm per 100 μm ^2. A roughened surface is formed.

Here, the number of the roughening particles 15 is adjusted by appropriately adjusting the plating conditions such as current density and time during copper plating so that the particle diameter is 0.2 μm or more and less than 1.5 μm per 100 μm ^2. Some roughened particles 15 can be obtained.

  In the following examples and comparative examples, 02ZrOFC copper foil (oxygen-free copper foil containing Zr 0.02 mass%) having a thickness of 10.5 μm is used as the rolling degree foil 11.

  FIG. 4 shows a photomicrograph of the surface of the current collector copper foil.

  A method for producing Comparative Example I without copper plating in FIG. After the surface is cleaned by electrolytic degreasing and acid cleaning, Ni—Co alloy plating, zinc plating, and chromate treatment are subsequently performed. The formed copper foil 10 for current collectors was produced. The thickness of the chromium-based film is chromate treatment (film thickness 100 nm).

  A method for producing the copper foil for current collector of (b) Comparative Example II and (c) Example I with copper plating in FIG. 4 will be described. First, after the surface was cleaned by electrolytic degreasing and acid cleaning, a base copper plating layer and a copper roughening plating layer were formed by copper plating. Subsequently, Ni-Co alloy plating, zinc plating, and chromate treatment were performed to produce a collector copper foil on which the nickel-cobalt alloy plating thin film 14a, the zinc plating thin film 14b, and the chromate treatment layer 14c were formed. Here, the copper foil for current collectors of (b) Comparative Example II and (c) Example I was prepared by adjusting the current density, time, etc. in the plating treatment during the formation of the copper roughening plating layer. The average particle size was 2.0 μm and 0.6 μm, respectively. The chromium-based film is formed by chromate treatment and has a thickness of 100 nm.

  Evaluation of the copper foil for collectors of this FIG. 4 was performed as follows.

  The average of the longest diameter (major axis) and the shortest diameter (minor axis) of the roughened particles 15 is defined as the particle size of the roughened particles 15. An area of 10 μm × 10 μm is divided into a grid pattern of 1 μm × 1 μm (10 squares × 10 squares), and the average particle diameter of the roughened particles 15 present at the crossing points of the grids is determined as the average grain of the copper foil 10 for current collector The diameter.

The number of roughened particles 15 having a particle size of 0.2 μm or more and less than 1.5 μm present in a 10 μm × 10 μm region was counted, and this was defined as the number of roughened particles per 100 μm ² (hereinafter, the number of particles N).

  The results are shown in Table 1.

  Next, the negative electrode active material 16 was applied to the copper foil for current collector 10 shown in Table 2 and dried using the copper foil 10 for current collector shown in Table 1, and the copper foil 10 for current collector and The adhesion of the active material layer 17 was evaluated.

Si-based active materials used in Comparative Example 1-A to Comparative Example 4-A and Example 1-A to Example 4-A:
An amorphous Si powder and graphite particles were uniformly dispersed in an NMP (N-methyl-pyrrolidone) solution containing 10 mass% of polyamic acid, which is a polyimide precursor, to prepare a Si-based active material slurry. The mass ratio of the NMP solution, amorphous Si powder, and graphite powder was 10: 85: 5. This slurry was applied to one side of each current collector copper foil 10 to a thickness of 200 μm, dried in air at 100 ° C. for 30 minutes, and further heated at 400 ° C. for 10 hours in an Ar atmosphere. A negative electrode current collector 20 having a system active material was produced.

Sn-based active materials used in Comparative Example 1-B to Comparative Example 4-B and Example 1-B to Example 4-B:
In the negative electrode current collector 20 having the Si-based active material, the negative electrode current collector 20 having the Sn-based active material was produced by using SnO powder instead of the amorphous Si powder described above as the negative electrode active material 16.

  That is, SnO powder and graphite particles were uniformly dispersed in an NMP solution containing 10 mass% of polyamic acid, which is a polyimide precursor, to prepare a SnO-based active material slurry. The mass ratio of the NMP solution, SnO powder and graphite powder was 10: 85: 5. This slurry was applied to one side of each current collector copper foil 10 to a thickness of 200 μm, dried in air at 100 ° C. for 30 minutes, and further heated at 400 ° C. for 10 hours in an Ar atmosphere. A negative electrode current collector 20 having a system active material layer was produced.

  FIG. 5 is a schematic view of a peel test for evaluating the adhesion between the current collector copper foil 10 and the active material layer 17.

  The negative electrode current collector 20 cut out to a width of 15 mm is wound around a SUS rod 21 having a diameter of 3 to 15 mm with the coated surface outside, a load 22 of 50 gf is applied to one end of the negative electrode current collector 20, and the other is indicated by an arrow. As shown in Fig. 5, the negative electrode current collector 20 is pulled down at a constant speed, and the state of the active material layer 17 at that time is evaluated. Here, as described above, the active material layer 17 includes the negative electrode active material 16 and the binder material 18.

At this time, the following phenomenon occurs in the active material layer 17 as the winding diameter of the SUS rod 21 decreases.
(1) Fine cracks occur in the active material layer.
(2) Cracks in the active material layer become large and the number thereof increases.
(3) The active material layer peels off.

  The better the adhesion of the current collector copper foil 10 / active material layer 17, the less likely these phenomena occur. That is, the adhesion between the current collector copper foil 10 and the active material layer 17 was quantitatively evaluated.

Test results:
Table 2 shows the results of the peel test of the copper foil coated with the Si-based and Sn-based active materials.

  As a result of intensive studies, a sample in which cracks are observed in the active material layer 17 when it is wound around a SUS rod having a length of 6 mm or more is obtained from the current collector copper foil 10 to the active material layer 17 even in the manufacture of an actual lithium ion battery. A correlation was found that part of the film peeled off. Therefore, in this test, the minimum diameter of the SUS rod in which no crack was observed in the active material layer 17 with the naked eye was set to be 6 mm or more.

From Table 2, in Comparative Examples 1-A and 1-B, since the roughening treatment was not performed, the SUS bar was cracked at less than 8 mm, and the evaluation of adhesion was “impossible”. In Comparative Examples 2-A and 2-B, the number of roughened particles 15 (number N of particles) per 100 μm ^{2 having} a particle size of 0.2 μm or more and less than 1.5 μm is 294. The average particle size was as large as 2.0 μm, and the minimum diameter of the SUS rod without cracks was 7 mm, and the evaluation result of adhesion was “impossible”. Furthermore, Comparative Examples 3-A and 3-В and Comparative Examples 4-A and 4-B have a particle number N of 884 and 669, but since the average particle diameter is less than 0.5 μm, cracks occurred. The minimum diameters of the SUS rods that were not present were 7 mm and 6 mm, respectively, and the evaluation of adhesion was “impossible”.

  On the other hand, in Examples 1-A and 1-B, the average particle diameter of the roughened particles 15 is 0.6 mm, the number of particles N is 336, and even if the SUS bar is 3 mm, cracks do not occur. Therefore, it was confirmed that the minimum diameter of the SUS rod was less than 6 mm and the adhesion was good. In addition, in Examples 2-A to 4-A and Examples 2-B to 4-B, the average particle diameter of the roughened particles 15 is within a specified value, 0.8 μm, 0.9 μm, It was 0.5 μm, the number N of particles was within the specified value, and the minimum diameter at which cracking did not occur in the evaluation using a SUS rod was 5 mm or less, and it was confirmed that the adhesion was good.

Ni tab lead bondability:
Table 3 shows the test results of the evaluation of the bondability between the current collector copper foils 10 and the current collector copper foils 10 and the Ni tab leads.

  Comparative Example 1-1 to Comparative Example 1-3 are the treatment layer 14 (nickel-cobalt alloy plating) on the rolled copper foil 11 that has not been subjected to copper plating (the base copper plating layer 12 and the copper roughening plating layer 13). The thin film 14a, the galvanized thin film 14b, and the chromate treatment layer 14c) are formed, and the copper foil 10 for current collectors has a different amount of nickel-cobalt alloy plated thin film 14a.

  In Example 1-1 to Example 1-12, 0.5 μm of the base copper plating layer 12 and 1.0 μm of the copper roughening plating layer 13 were applied on the rolled copper foil 11 having a thickness of 10.5 μm. Thereafter, the treatment layer 14 (nickel-cobalt alloy plating thin film 14a, galvanization thin film 14b, chromate treatment layer 14c) was provided so that the average particle diameter was 0.6 μm and the number N of particles was 336. This is a copper foil 10 for electric bodies. However, by adjusting the amounts of the nickel-cobalt alloy plating thin film 14a, the copper roughening plating layer 13, and the chromate treatment layer 14c, the average particle diameter of the roughening particles 15 becomes a value shown in Table 3 respectively. It is adjusting.

Comparative Example 2-1 to Comparative Example 2-3 have the same layer structure as Example 1-1, but the amount of nickel-cobalt alloy plating thin film is 80 (μg / cm ² ), and the average particle size Is the copper foil 10 for current collectors in which the roughened particles 15 are formed so that the particle number N is 294.

For evaluation of the Ni tab lead bondability, these current collector copper foils 10 were cut into W10 mm × L60 mm, and subjected to heat treatment at 400 ° C. for 10 hours in an N ₂ atmosphere using an infrared image furnace, and Ni ribbons (t0. 1 mm × w 4 mm × 50 mm) and ultrasonic welding, and the strength was measured by a tensile test (load cell: 500 kgf, speed: 50 mm / min).

Ultrasonic welding conditions are
Equipment: DUKANE 4070
Frequency: 40kHz
Amplitude: 20 μm
Applied pressure: 0.2 MPa
Energy: 20J
It is.

  FIG. 3 shows the case where the rolled copper foil 11 was plated with copper (Examples 1-1 to 1-12 (average particle diameter of the roughened particles was 0.6 μm)) and Comparative Examples 2-1 to 2-3 (coarse The average particle size of the particles is 2.0 μm)), and in other cases (Comparative Examples 1-1 to 1-3), the relationship between the amount of nickel-cobalt alloy plating thin film formed and the Ni tab lead weld strength It is the shown graph. In addition, as above-mentioned, these copper foils 10 for collectors have the base copper plating layer 12, the copper roughening plating layer 13, the nickel-cobalt alloy plating thin film 14a, the zinc plating thin film 14b, and the chromate treatment layer 14c in order. Have.

From FIG. 3, the thicker the nickel-cobalt alloy plating thin film, the higher the welding strength, but the amount of nickel-cobalt alloy foil film of Comparative Example 2-1 to Comparative Example 2-3 was set to 80 μg / cm ² . When the copper foil 10 for current collectors was bent at 90 °, the treatment layer 14 was cracked (evaluation of crack resistance was “x”). If the treatment layer 14 is cracked, it is not preferable because copper may be eluted from the crack portion when the battery is assembled. Therefore, the nickel-cobalt alloy plating thin film is preferably less than 80 μg / cm ² .

  In addition, even when the same nickel-cobalt alloy plating thin film is applied, the copper plating is performed on the rolled copper foil, so that the copper plating is not performed if the base copper plating layer and the copper roughening plating layer are formed. It can be seen that the strength is higher than the case.

Optimum thickness of nickel-cobalt alloy plating thin film:
The Table 3 and Figure 3, a nickel - cobalt alloy plating film is good than 80 [mu] g / cm ² does not occur cracks, weld strength to the 5 [mu] g / cm ² or more 80 [mu] g / cm less than ² is desired account.

  The material of the rolled copper foil may be a 02ZrOFC material, a TPC material (tough pitch copper material), or another OFC material.

  However, in general, the welding strength is electrolytic foil <TPC foil <high strength (02ZrOFC) foil. In the present invention, it is more preferable to use 02ZrOFC foil.

  Furthermore, in the case where an OFC containing Zr is used, it is set to 0.02 mass% in the embodiment, but sufficient strength can be obtained even at about 0.015 mass%. Further, if it exceeds 0.03 mass%, the degree of strength improvement reaches its peak, so that it is not necessary to include any more Zr. However, it is possible to improve a manufacturing method and a composition and to improve an intensity | strength.

  In this embodiment, the surface of the rolled copper foil is subjected to base copper plating for the purpose of smoothing and / or reducing variation of the roughened particles 15 before the copper roughening plating treatment, but the base copper plating is omitted. May be.

  The chromium-based film may be pure chromium, an alloy, or a chromium compound. Methods include plating, electrolytic chromate treatment, coating chromate treatment, and reactive chromate treatment.

  In the reactive chromate treatment, substitution reaction with zinc is the mainstream, so only in this case galvanization is necessary immediately before.

DESCRIPTION OF SYMBOLS 10 Current collector copper foil 11 Rolled copper foil 12 Base copper plating layer 13 Copper roughening plating layer 14 Treatment layer 14a Nickel-cobalt alloy plating thin film 14b Zinc plating thin film 14c Chromate treatment layer 15 Roughening particle 16 Negative electrode active material 17 Active Material layer 18 Binder material 20 Negative electrode current collector for lithium ion secondary battery

Claims (7)

In the copper foil for current collector that becomes the negative electrode current collector for the lithium ion secondary battery by providing the active material layer,
Rolled copper foil,
Provided in order on the rolled copper foil, and having roughened particles composed of a copper roughened plating layer and a chromium-based film,
The roughened particles have an average particle size of 0.5 μm or more and less than 1.0 μm, and there are 100 or more and less than 1000 roughened particles of 0.2 μm or more and less than 1.5 μm per 100 μm ^2. Yes Copper foil for current collector.   The copper foil for current collectors according to claim 1, wherein the rolled copper foil is made of oxygen-free copper containing 0.015 mass% or more and 0.030 mass% or less of Zr. Between the copper roughening plating layer and the chromium-based film,
The copper foil for current collectors according to claim 1, wherein a nickel-cobalt alloy plating thin film and a zinc plating thin film of 5 μg / cm ² or more and less than 80 μg / cm ² are sequentially provided.   The copper foil for collectors in any one of Claim 1 to 3 with which a base copper plating layer is provided between the said rolled copper foil and the said copper roughening plating layer.   The copper foil for a current collector according to any one of claims 1 to 3, wherein the chromium-based film is a chromate-treated layer.   A negative electrode current collector for a lithium ion secondary battery, comprising an active material layer provided on the current collector copper foil according to claim 1. It is a manufacturing method of the copper foil for current collectors in any one of Claims 1-4,
The current density during plating for forming the copper roughening plating layer is 35 A / dm ² or more and 45 A / dm ² or less, the plating time is 1 sec or more and 50 sec or less, and the plating water temperature is 15 ° C. or more and 50 ° C. or less. A method for producing a copper foil for a current collector.