JP4948656B2 - Perforated roughening copper foil for secondary battery current collector, method for producing the same, and negative electrode for lithium ion secondary battery - Google Patents

Description

The present invention relates to a perforated roughened copper foil suitable for a current collector for a secondary battery.
The present invention also relates to a negative electrode for a lithium ion secondary battery in which the perforated roughened copper foil is used as a current collector, and a silicon-based active material is laminated on the current collector.

  Secondary batteries are incorporated into IT (information and communications technology field) -related devices such as communication terminal devices and mobile phones, and recently, their demand has expanded dramatically, including in hybrid and electric vehicles. I am doing. Such secondary batteries are required to have high performance, high charge / discharge capacity and high potential in addition to miniaturization and thinning. In response to such demands, lithium ion secondary batteries are currently attracting particular attention because of their convenience that takes advantage of economic efficiency and environmental characteristics.

  In this lithium ion secondary battery, the characteristics of the negative electrode particularly determine the charge / discharge characteristics as a secondary battery and the superiority or inferiority of maintaining a high potential. The negative electrode of an early lithium ion secondary battery uses a copper foil as a current collector, carbon (graphite) mixed with a binder (binder) as an active material, and the active material is made of a copper foil as a current collector. It was prepared by coating on both sides and drying under pressure.

  In order to further improve the characteristics of the lithium ion secondary battery, it is necessary to improve the current collecting capacity of the negative electrode. As a method for improving the current collecting capacity of the negative electrode, it is conceivable to stack the carbon active material thickly on the current collector. However, when the active material is thickly stacked on the current collector, the size of the negative electrode increases, The size of the battery becomes large and the practicality becomes poor, and it becomes difficult to laminate carbon with a uniform thickness on both sides of the current collector (copper foil). Therefore, at present, the current collecting capacity is improved by reducing the particle size and increasing the surface area of carbon.

  Recently, however, there has been a demand for a higher capacity for secondary batteries, and a technique has been advanced in which the active material is changed from a carbon-based material to, for example, a silicon-based material, and the amount of lithium occluded is remarkably improved. In order to change the active material from carbon-based to silicon-based, it is necessary to develop a current collector that maximizes the characteristics of the active material. In particular, the adoption of a silicon-based active material requires a current collector that can follow the characteristics of the active material. Since the silicon-based active material has a fine particle size, it is necessary that the surface of the current collector to be laminated has an appropriate roughness, and the so-called surface roughness that can be filled with many active materials is sufficient. Desired. In addition, the adoption of a silicon-based active material requires an appropriate hardness and plasticity (elongation) for a metal foil serving as a current collector.

One of the conditions for satisfying the high capacity and long charge / discharge life of a lithium ion secondary battery is an active material that is expected to improve capacity on the negative electrode and a metal foil suitable as a current collector for laminating the active material Selection.
In response to the demand for higher capacity of secondary batteries, the active material is being changed from a carbon-based active material to a silicon-based active material as described above.
On the other hand, silicon active materials have a special hardness and a large expansion / contraction between particles during charging / discharging. Therefore, selection of a current collector that can maximize the characteristics of this silicon-based active material is the biggest issue. It has become to. As a current collector that satisfies such a problem, a metal foil that has a uniform shape on both the front and back surfaces of the current collector and that can hold the active material thin is required, thereby increasing the capacity and charge of the lithium ion secondary battery. Long discharge life can be achieved at the same time.

  In general, the essential requirements for a negative electrode current collector material of a lithium ion secondary battery using metal foil are excellent in conductivity, ease of surface processing on both sides, adhesion to the active material, and ultrasonic bonding of the current collecting terminal. It has characteristics. Although copper foil has conductivity and ultrasonic bonding properties of current collecting terminals among these essential requirements, there is still room for improvement in terms of surface shape and adhesion to the active material.

As a metal foil for a secondary battery negative electrode, Patent Document 1 discloses a current collector in which through holes are provided in a copper foil in order to increase the surface area of the copper foil and increase the adhesion of the active material.
Moreover, the proposal of the electrical power collector which provided the through-hole in metal foil is also disclosed by patent document 2, 3.
However, the current collector disclosed in Patent Document 1 is a material in which the shape of the through-holes is finely defined to increase the surface area of the current collector and increase the adhesion with the active material made of carbon. . Patent Document 2 is a technology for applying nickel plating to the surface of a copper foil having a through hole as a current collector for an alkaline secondary battery in order to prevent corrosion by an alkaline electrolyte, and mainly uses a hydrogen storage alloy as an active material. This slurry is used. Patent Document 3 relates to a technology that regulates the position of a through hole provided in a current collector, and uses an active material mainly composed of carbon.
Thus, the perforated current collector disclosed in these patent documents is a technique developed for laminating carbon or a hydrogen storage alloy as an active material. Therefore, the perforated current collector disclosed in the above-mentioned patent document provides a thin secondary battery that functions as a current collector that fully exhibits the characteristics of a silicon-based active material, that is, high performance and can be miniaturized. The ability as a current collector to sufficiently extract the function of a silicon-based active material that can be obtained has not been pursued.

JP 2000-294250 A Japanese Patent Laid-Open No. 10-112326 JP-A-11-86869

In particular, the present invention can sufficiently exhibit the characteristics of a silicon-based active material, that is, can sufficiently extract the functions of a silicon-based active material that can provide a thin secondary battery with high performance and downsizing. An object is to provide a perforated roughened copper foil (current collector).
It is another object of the present invention to provide an electrode for a secondary battery in which a silicon-based active material is uniformly laminated on the current collector.

The perforated roughened copper foil for a lithium ion secondary battery current collector of the present invention is an untreated copper foil or a non-treated copper foil in which a through hole having an opening area of 0.01 mm ² or less is drilled. A primary roughening treatment layer made of copper or a copper alloy is provided on the surface of the treated copper alloy foil by pulse cathode electrolytic treatment, and a secondary treatment made of copper or a copper alloy by smooth plating treatment on the primary roughening treatment layer. A layer is provided.

The perforated roughened copper foil for a lithium ion secondary battery current collector of the present invention is an untreated copper foil or a non-treated copper foil in which a through hole having an opening area of 0.01 mm ² or less is drilled. A surface of the treated copper alloy foil is provided with a primary roughened layer made of the same metal as the untreated copper or the untreated copper alloy foil by pulse cathode electrolytic treatment, and smooth plating is performed on the primary roughened layer. A secondary treatment layer made of copper or the same metal as the copper alloy foil is provided by the treatment.

The through-hole drilled in the copper foil is circular (including an ellipse) or geometric shape (polygon, indeterminate shape, etc.), and the area of the opening of one hole is 0.01 mm ² or less. It is preferable.
Furthermore, in the copper foil or copper alloy foil in which the through holes are formed, the total area of the opening portions of the through holes is preferably 55% or less with respect to the surface area of the foil before the through holes are formed.

  The perforated roughened copper foil for a secondary battery current collector of the present invention has a rust preventive layer provided with a rust preventive agent on the surface of the secondary treated layer, and a protective layer provided with a coupling agent on the surface of the rust preventive layer. Is provided.

The method for producing a perforated roughened copper foil for a current collector of a lithium ion secondary battery according to the present invention comprises an untreated copper in which a through hole having an opening area of 0.01 mm ² or less is drilled. A primary roughening layer made of copper or a copper alloy is provided on the surface of the foil or untreated copper alloy foil by pulse cathode electrolytic treatment, and a secondary treatment layer made of copper or a copper alloy is provided on the primary roughening layer. It is a manufacturing method provided by a smooth plating process.

The method for producing a copper foil for a negative electrode current collector of a lithium ion secondary battery of the present invention is made of oxygen-free copper , has an elongation at room temperature of 3.5% or more, and the surface substrate on both surfaces is JIS-B- A first roughening layer made of metallic copper is provided on both surfaces of an untreated rolled copper foil having an Rz of 0.8 to 2.5 μm as defined by 0601 by pulse cathodic electrolytic roughening, and then the first roughened A smooth copper plating treatment is performed on the surface of the chemical treatment layer to provide a second copper plating layer whose roughness on both surfaces is 3.0 μm or less in Rz, and then the third rust prevention layer with a rust inhibitor on the surface of the second copper plating layer the provided, then a manufacturing method in said third anticorrosive layer surface providing a fourth protective layer with a coupling agent.
In addition, the method for producing a perforated roughened copper foil for a lithium ion secondary battery current collector according to the present invention has not yet been provided with a through hole in which the area of the opening of one hole is 0.01 mm ² or less. On the surface of the treated copper foil or untreated copper alloy foil, a primary roughening treatment layer made of copper or the same metal as the copper alloy foil is provided by pulse cathode electrolytic treatment, and copper or the above-mentioned It is a manufacturing method which provides the secondary treatment layer which consists of the same metal as copper alloy foil by a smooth plating process.

  The lithium ion secondary battery negative electrode using the perforated roughened copper foil for the secondary battery current collector of the present invention is an electrode formed by laminating a silicon-based active material on the surface of the perforated roughened copper foil. It is.

The perforated roughened copper foil of the present invention is a copper foil or copper alloy foil in which a through hole is formed (hereinafter simply referred to as an untreated copper foil or a copper foil when it is not necessary to distinguish between copper foil and copper alloy foil) The copper or the same metal as the copper alloy foil is deposited on the surface of the copper foil by pulse cathodic electrolysis treatment and subjected to fine roughening treatment, and then the roughened particles (metal bump) ) Is applied so that it does not fall off, and a rust prevention layer and a protective layer made of a coupling agent are provided thereon as necessary. Therefore, a large amount of silicon-based active material can be efficiently laminated (coated), and an excellent effect as a high-quality negative electrode current collector for a lithium ion secondary battery is exhibited.
In addition, by using the perforated roughened copper foil of the present invention as a current collector and laminating a silicon-based active material on the current collector, the characteristics of the silicon-based active material sufficiently function, high performance and small size, A thin lithium ion secondary battery can be provided.

It is process explanatory drawing which shows an example of the surface roughening process of a perforated copper foil. It is explanatory drawing illustrating the cross-sectional shape of the copper foil by this invention embodiment, (A) is a cross section of the primary roughening process layer a, (B) is a cross section of the secondary roughening process layer b.

Hereinafter, the present invention will be described in detail.
The perforated roughened copper foil of the present invention has a very low roughened and uniform surface on both sides of the copper foil in order to strengthen the adhesion with the silicon-based active material and hold more active material without dropping off. A primary roughening treatment with various copper particles or copper alloy particles is performed by pulse cathode electrolysis.
Next, in order to keep the primary roughened layer that has been subjected to the primary roughening treatment healthy, a smooth plating (cathodic electrolytic plating) is performed on the primary roughened layer with a plating solution having the same components as the particles used in the primary roughening. ) To provide a smooth secondary treatment layer (capsule plating layer).

Untreated copper foil and copper alloy foil can be either electrolytic copper foil or rolled copper foil. As the copper alloy foil, any copper-based alloy can be used, but it is particularly preferable to use a copper-tin alloy, the tin content is 0.15% or less, and the conductivity is 85% IACS or more. That is, it is more preferable to employ a copper-tin alloy having a conductivity of 85% or more of pure copper.
When the untreated copper foil is an electrolytic copper foil or an electrolytic copper alloy foil, the surface roughness Rz defined in JIS-B-0601 is 0.8 to 2. It is preferable to employ a copper foil in the range of 5 μm.
The electrolytic copper foil is preferably in a state in which the electrodeposited crystal grains at the time of foil production are very fine particles, and the electrolytic copper foil has a granular crystal structure with a fine cross section on the mat surface side. The electrolytic copper foil having such a crystal structure has an elongation at room temperature of 3.5% or more, and is sufficiently heated even at a pressing temperature (in the range of about 150 to 180 ° C.) when the silicon-based active material is pressure-bonded and laminated. This is because it has followability to expansion and contraction.

  The reason why the mechanical property of the electrolytic copper foil before drilling is preferably such that the elongation at normal temperature is 3.5% or more is that an active material is applied to the surface of the roughened copper foil that has been drilled. This is because the adhesion with the active material is maintained against the expansion and contraction of the silicon-based active material at the time of charge and discharge after the battery is assembled as an electrode, and appropriate tracking characteristics with respect to the thermal history are ensured.

When the untreated copper foil is a rolled copper foil or a rolled alloy copper foil, it is preferable to employ a copper foil having a surface roughness Rz of 1.5 μm or less on both sides. In the case of a rolled copper foil, it is preferable to employ a copper foil obtained by rolling a copper alloy ingot containing oxygen-free copper or tin. The properties of the rolled copper foil or rolled alloy copper foil before drilling are preferably in the range of 35 to 45 kN / cm ² (50 to 65 MPa for Young's modulus) as defined by IPC-TM-650.

  Hump-like particles are attached by primary roughening on both the front and back surfaces of a copper foil having appropriate through holes formed in the copper foil. Next, smooth plating is applied to the surfaces of the bump-like individual particles. The bump-like fine particles of the secondary roughened layer provided by the smooth plating process maintain the primary roughened layer in a healthy shape and achieve uniformity of particles and prevention of falling off. The rough surface after the smooth plating treatment has a surface roughness Rz specified in JIS-B-0601 of 3.0 μm or less, preferably 2.5 to 3.0 μm.

Then, if necessary, a rust preventive layer is provided on the surface of the rough surface after the secondary smooth plating treatment. The rust preventive layer may be chromate rust preventive or organic rust preventive, but the chromium adhesion amount in the chromate rust preventive treatment is preferably 0.005 to 0.025 mg / dm ² as metal chromium. When an organic rust preventive is selected, there is no particular limitation as long as it is a BTA (benzotriazole) -based derivative, for example, a salt spray test (salt water concentration: 5%) defined in JIS-Z-2371 (NaCl, temperature 35 ° C.) It is sufficient that a film is formed so that the surface does not change to copper oxide for up to 24 hours.

It is desirable to provide a protective layer made of a single molecule of the coupling agent on the surface of the antirust layer. The adhesion amount in the case of a silane coupling agent is desirably 0.001 to 0.015 mg / dm 2 as silicon, and this adhesion amount range is a monomolecular coating amount (protective layer).
The coupling agent can be appropriately selected depending on the target active material. In addition to silane coupling agents, epoxy, amino and vinyl coupling agents can be selected.

Next, one embodiment of the method for producing a perforated roughened copper foil of the present invention will be described with reference to FIG.
First, the copper foil roughening treatment will be described, and the copper alloy foil roughening treatment will be described later.
First, a through hole is formed in an untreated copper foil with a punching machine. The untreated copper foil A in which the through holes are formed is guided to the first treatment tank 1 for forming the surface of the pulsed cathode electrolytic roughened copper particles. The first treatment tank 1 is provided with an iridium oxide anode 11 and filled with a copper-sulfuric acid electrolyte solution 12. In the primary treatment tank 1, the both sides of the copper foil A are made of bump-like fine roughened particles made of copper particles. A primary roughening treatment layer is formed. The copper foil B on which the primary roughening treatment layer is formed in the first treatment tank 1 is guided to the second treatment tank 2 after being washed in the water washing tank 15. In the figure, reference numeral 13 denotes a shielding plate.

The second treatment tank 2 is provided with an iridium oxide anode 21 and filled with a copper-sulfuric acid electrolyte solution 22 as in the first treatment tank, and is subjected to a smooth copper plating process. The copper foil C that has been subjected to the smooth plating process is guided to the third processing tank 3 after being washed in the water washing tank 25.
The third treatment tank 3 is provided with a SUS anode 31, filled with a chromate electrolyte 32, and provided with a chromate rust preventive layer. The copper foil D provided with the chromate rust prevention layer in the third treatment tank 3 is washed in the water washing tank 35 and then guided to the fourth treatment tank 4.

The fourth treatment tank 4 is filled with a silane coupling liquid 42, and a silane coupling agent is applied to the surface of the copper foil D. The copper foil E coated with the silane coupling agent in the fourth treatment tank 4 is wound around the winding roll 6 through the drying step 5.
In the figure, reference numeral 7 denotes a power supply contact roll.

The said roughening process process is a process about copper foil. When the untreated copper foil is a copper alloy foil, the primary roughening treatment and the secondary roughening treatment may be performed by the above treatment, but depending on the copper alloy foil, it is preferable to perform the roughening treatment with the same alloy as the copper alloy. In some cases.
When a roughening treatment of the same alloy composition as that of the untreated copper alloy foil A is performed, the first treatment tank 1 is filled with a copper-based sulfuric acid electrolyte solution 12 in which the same type of metal as the copper alloy foil is appropriately dissolved. Then, a primary roughening treatment layer made of bump-like fine roughening particles made of copper alloy particles is formed on both surfaces of the copper alloy foil A in the first treatment tank 1.
Similar to the first treatment tank, the second treatment tank 2 is filled with an electrolytic solution 22 mainly composed of copper in which the same metal as the copper alloy foil is dissolved, and is subjected to a smooth copper alloy plating process.
Other treatments are the same as the copper foil roughening treatment.

When electrolytic copper foil is used as the untreated perforated copper foil A, the double-sided gloss has a smoother surface shape than the electrolytic copper foil having a crystal structure composed of columnar crystal grains in order to further improve the active material characteristics and battery characteristics. Electrolytic copper foil is preferred, and the surface roughness of the front and back after electrolytic foil production is preferably in the range of 0.8 or more and less than 2.5 μm in terms of surface roughness Rz defined in JIS-B-0601.
When the untreated copper foil is a rolled copper foil or a rolled alloy copper foil, it is preferable to use an oxygen-free copper material (OFC material).
Furthermore, it is preferable that the normal temperature elongation of the untreated copper foil is 3.5% or more, regardless of whether it is electrolysis, rolling, or alloy copper foil.

Since the surface-treated copper foil of the present invention emphasizes heat resistance and plastic followability particularly during active material coating lamination drying process and charging / discharging after being incorporated in a secondary battery, appropriate mechanical characteristics Is required. For example, the value of Vickers Hardness Hv (Vickers Hardness) is preferably in the range of about 80 to 110, and the elongation at normal temperature is preferably about 3.5% or more. With such a perforated copper foil, active material peeling or breakage of the copper foil as a current collector caused by significant plastic deformation due to thermal history does not occur unless the aperture ratio exceeds 55% at the maximum.
Moreover, it is preferable that the area of the opening part of one hole is 0.01 mm < ² > or less. When the area of the opening portion of one hole is 0.01 mm ² or less, the opening portion is blocked by the roughening treatment, but a gap through which Li ions can pass remains. Thereby, even if a difference occurs in the active material adhesion amount on both sides of the current collector, the occlusion amount of the entire active material can be utilized to the maximum without being restricted by the Li occlusion amount on the side with the smaller adhesion amount. If the area of the opening part of one hole is larger than 0.01 mm ² , the active material is connected on both the front and back sides, which is effective for current collection characteristics. On the other hand, if there is a weak part in the opening part, Cracks may occur around the opening of the copper foil due to expansion and contraction during charging and discharging.
In addition, an aperture ratio means the ratio of the total area of an opening part with respect to the area of the untreated copper foil before a through-hole drilling.

When the untreated copper foil is, for example, a perforated copper foil that is not an alloy foil, the primary roughening treatment provided on both sides is a pulse using a copper sulfate bath to which an arsenic compound or metal molybdenum is added in the first treatment tank 1. It is applied by cathodic electroplating.
In the primary roughening treatment, copper bumpy rough particles are formed on both surfaces of the perforated copper foil. Specifically, copper sulfate as copper is 20 to 30 g / l, sulfuric acid concentration is H ₂ SO ₄ as 90 to 110 g / l, sodium molybdate as Mo is 0.15 to 0.35 g / l, and chlorine is chloride ion. With the electrolyte mixed in 0.005-0.010 g / l in terms of conversion, the bath temperature was set to 18.5-28.5 ° C., the pulse cathode electroplating current density was set to 22-31.5 A / dm ² , A sound layer of roughened copper bumps is formed on the copper foil surface at an appropriate flow rate and inter-electrode distance.

The first roughening treatment will be further described in detail with reference to the drawings.
In the first roughening treatment tank 1, two pairs of iridium oxide anodes 11 that are separated with a shielding plate 13 interposed therebetween are arranged on both sides of the rolled copper foil A.
The copper-sulfuric acid electrolyte 12 flows in the first roughening treatment tank 1 at a predetermined flow rate. For example, the first roughening treatment tank 1 is filled with a copper-sulfuric acid electrolyte solution 12 and stirred at a predetermined flow rate, or the copper-sulfuric acid electrolyte solution 12 is fed from the bottom of the first roughening treatment tank 1. In a circulating laminar state where the liquid is supplied and overflows, the fluid flows at a predetermined flow velocity (hereinafter referred to as “first circulating laminar flow velocity”).

  In the first roughening treatment tank 1, the surface of the copper foil of the base material is subjected to a surface treatment by pulse cathodic electrolysis with extremely low roughness and evenness. That is, on both surfaces of the untreated, oxygen-free and rolled copper foil illustrated in FIG. 2A (however, the illustration of FIG. 2A shows only one surface), for example, surface roughness A uniform bump-shaped copper particle layer (primary roughening layer) a of about 1.5 to 1.6 μm in Rz is formed.

Pulse Cathodic Electroplating Treatment Method On-time (time for applying current) and off-time in performing pulse cathodic electroplating treatment in which a pulsed current is applied between the power supply contact roll 7 and the iridium oxide anode 11. In order to determine the time (period in which no current is applied), it is necessary to consider copper concentration, sulfuric acid concentration, average current density, flow rate of electrolyte, bath temperature, and treatment time. For these settings, it is empirically confirmed that the conditions for sound “burnt plating” can be replaced with pulsed cathode electrolytic plating treatment by DC electrolytic plating treatment, and that equivalent or better sound treatment can be achieved. .

What is important in the pulse cathode electrolytic plating method is the maximum value (peak) of the current applied to the roll 7 and the anode 11.
The normal peak current value is approximately (the sum of the ratios of the on time and off time) × the average current value flows during the on time.
The total ratio of the on time and the off time is, for example, 5 when the on time is 10 ms and the off time is 40 ms, and the total ratio is 7 when the on time is 10 ms and the off time is 60 ms.

  In this case, if the flow rate of the copper-sulfuric acid electrolyte 12 is slow and the supply of copper ions is insufficient, or if the flow rate of the copper-sulfuric acid electrolyte solution 12 is fast and the supply of copper ions is excessive, a healthy “burnt plating” I can't. Therefore, a copper concentration bath rich in manageability of the copper-sulfuric acid electrolyte 12 is set, and the average current density, flow velocity, bath temperature, and treatment time are controlled to perform the treatment.

  The average current density is generally set to the current value when performing “DC electrolytic plating” that enables sound “burn plating” at the set bath temperature. The treatment time (energization time) is preferably a value obtained when “DC electrolytic plating treatment” is performed. For example, the processing time is 2.5 to 5.0 seconds.

  The flow rate of the copper-sulfuric acid electrolyte 12 only needs to be able to supply copper ions that can follow a healthy galvanization limit current density, so that it is sufficient to be about half the conveying speed of the copper foil A. For example, when the conveyance speed is 6 to 12 m / min, the flow rate is 3 to 6 m / min.

  In the case of the pulse cathode electroplating process, it is important to supply copper ions at the peak current, and theoretically, a flow rate of the copper-sulfuric acid electrolyte solution 12 faster than the copper foil transport speed is required. However, since copper ions are supplied even during the off time, it is not necessary to increase the flow rate of the copper-sulfuric acid electrolyte solution 12 as the sum of the on-time ratios increases. The flow rate can be processed at a flow rate that is about half the transfer speed of the copper foil, similar to the DC electrolytic plating process.

  In the determination of the on-time / off-time, the laboratory found that it is essential that the ratio of the on-time to the off-time, that is, the on-time / off-time is in the range of 1: 4 to 1: 6. It was.

The peak current density (current density during on-time) is determined by the on-time time, off-time time, and pulse cathode electrolytic average plating current density, and is not particularly limited. For example, when the on-time is 10 ms, The peak current density is preferably set so as to be 157.5 A / dm ² or less, and more preferably in the range of 154 to 157.5 A / dm ² .
In addition, it is also possible to appropriately perform electrolytic plating with smooth copper under the condition that the current density is set to 15 to 20 A / dm ² as necessary so that the copper bump roughened particles do not fall out in the same bath.

  Subsequently, the copper foil B subjected to the primary roughening treatment is moved to the second treatment tank 2 so that the fine copper roughening particles adhering in the primary roughening treatment are not dropped off from the surface of the perforated copper foil, A secondary roughening treatment is performed for the purpose of adjusting the surface shape of the fine copper roughened particles and uniformly preparing the surface. By this step, the uniformity of the roughening treatment thickness can be avoided, the problems with charging and discharging due to the removal of copper particles, the inadvertent adhesion to the separator, and the abnormal electrodeposition with the lithium compound used in the positive electrode can be avoided.

A method for forming the second roughened layer will be described in detail with reference to the drawings.
The copper-sulfuric acid electrolytic solution 22 is flowing in the second copper plating treatment tank 2 at a predetermined flow rate. For example, the copper-sulfuric acid treatment tank 2 is filled with a copper-sulfuric acid electrolytic solution 22 and stirred at a predetermined flow rate, or the copper-sulfuric acid electrolytic solution 22 is supplied from the bottom of the cupric-plating electrolytic treatment tank 2. It is flowing at a predetermined flow rate (hereinafter referred to as “second circulating laminar flow velocity”) in a circulating laminar flow state that is liquefied and overflows.
In order to keep the copper particle layer a adhering to the surface of the bump-shaped copper particles applied by the first roughening treatment in a healthy state, the copper particles are smoothed by a low current applied to the power supply contact roll 7 and the iridium oxide anode 21. A copper plating process is performed, and as illustrated in FIG. 2B, the copper-sulfuric acid electrolytic solution 22 is provided on both sides of the copper foil B on which the primary roughening treatment layer a is formed. The smooth copper plating layer (secondary roughening process layer) b which adheres the illustrated encapsulated copper layer which consists of smooth copper plating as a secondary roughening process b by cathodic electrolytic plating is formed.
By this smooth copper plating treatment, the bump-like fine particle layer (primary roughening treatment layer) a obtained by the primary roughening treatment maintains a healthy shape and maintains the uniformity of the particles.

Smooth electrolytic plating conditions The cathode electrolytic plating current density applied continuously between the roll 7 and the anode 21 was set to 15 to 20 A / dm ² , for example.
Specifically, the electrolytic solution in the second treatment tank 2 is set to 35 to 55 g / L using copper sulfate as copper, 90 to 110 g / L using sulfuric acid concentration as H ₂ SO ₄ , and a bath temperature of 35 to 55 ° C. The cathode electrolytic plating current density is set to 15 to 20 A / dm ² . A smooth copper plating is formed on the surface of the first roughening treatment layer (fine copper roughening particles) with an appropriate flow rate of the electrolytic solution 22 and an appropriate distance between the electrodes of the iridium oxide anode 21.
For example, the conveyance speed of copper foil is the same as the conveyance speed in the first step, for example, 6 to 12 m / min, and the second circulating laminar flow speed is 3 to 6 m / min.
Since the electrolysis time is smooth plating, it is defined by (current density × treatment time * plating amount), and is, for example, about 3.75 to 7.5 seconds.

  In this case, the roughness of the final roughened shape after smooth plating is the surface roughness Rz specified in JIS-B-0601, and both sides of the copper foil are 3.0 μm or less, preferably 2.3-3. The range is preferably 0 μm, more preferably 2.4 to 2.5 μm.

  When the surface-treated copper foil E is used as a current collector for a secondary battery by smooth copper plating, problems with charging / discharging due to copper particle detachment, inadvertent adhesion to the separator in the secondary battery, Abnormal electrodeposition with the lithium compound used for the positive electrode of the secondary battery can be avoided.

Next, if necessary, a chromate rust preventive agent is provided on the surface of the secondary roughened layer finished to 3.0 μm or less by dipping treatment or, if necessary, cathodic electrolysis treatment (third treatment tank 3) to enhance rust prevention power. The film thickness in the case of chromate treatment is preferably in the range of 0.005 to 0.025 mg / dm ² as the amount of metallic chromium. If it is this adhesion amount range, the surface will not change to the color of copper oxide until 24 hours under the conditions of the salt spray test (salt water concentration: 5% -NaCL, temperature 35 ° C.) specified in JIS-Z-2371.

  For the formation of the rust preventive layer, organic rust preventives represented by BTA (benzo triazole) are also commercially available and can be properly used. Incidentally, if it is an organic rust preventive agent, for example, it is chromate even if it is dipped in a bath constructed at 35-40 ° C. at 5.0 Wt% (weight percent) of product number C-143 of Chiyoda Chemical Co., Ltd. Rust prevention effect comparable to processing is obtained. These antirust treatment effects are the same regardless of whether the rolled copper foil is a base, an electrolytic copper foil base, or an alloy metal foil base, but the chromate treatment is excellent in cost performance.

Furthermore, a silane coupling agent is appropriately coated (protective layer) as necessary on the surface subjected to the chromate treatment. By providing the silane coupling agent layer, the adhesion with the binder mixed in the silicon-based active material for the lithium ion secondary battery can be enhanced. The silane coupling agent is appropriately selected depending on the target active material, but it is preferable to select an epoxy-based, amino-based, or vinyl-based coupling agent that is particularly excellent in compatibility with a silicon-based active material. The agent having a double bond or an azo group is particularly preferred because it is rich in crosslinking reaction and excellent in adhesion effect.
In the present invention, the kind of the product is not limited, but the adhesion amount of the silane coupling agent is in the range of 0.001 to 0.015 mg / dm ² as silicon in order to improve the adhesion at least chemically. preferable.

A “perforated electrolytic copper foil” was prepared by punching and punching an untreated electrolytic copper foil having a thickness of 0.018 mm and having a diameter of 50 μm and an aperture ratio of 55%, which was manufactured with a mirror surface on the liquid surface side under electrolytic foil production conditions. In addition, the shape roughness of the matte surface side (electrodeposition liquid surface side) of the electrolytic copper foil before drilling is 0.8 μm at the surface roughness Rz defined in JIS-B-0601, and the glossy surface side (drum surface side). Using a copper foil (double-sided glossy electrolytic copper foil manufactured by Furukawa Electric Co., Ltd.) having a surface roughness Rz of 1.2 μm and a normal temperature elongation of 6.2%, both surfaces of the foil were roughed under the following conditions. Was applied. In this process, the roughening process is divided into the matte side (electrodeposition liquid side) from the tank inlet to the bottom side, and the glossy side (drum peeling surface side) from the bottom to the tank outlet side. Was subjected to a roughening treatment. The reason for dividing the pulse treatment into two times is to avoid cutting and elongation problems in the tank because it is a perforated copper foil and heat generation at peak current is larger than that of a non-perforated copper foil. In addition, the ON-OFF time can be individually set so that the surface roughness by the finish roughening process on both sides is matched.
Next, a smooth copper plating treatment was performed by a secondary roughening treatment by DC cathodic electroplating on both sides simultaneously from the tank inlet to the bottom side.
In the examples and comparative examples, the cathode electrolysis conditions are described separately as “pulse cathode electrolysis” and “DC cathode electrolysis”.

[Primary coarse particle formation bath composition and treatment conditions]
Copper sulfate: 23.5 g / l as metallic copper
Sulfuric acid ... 100g / l
Sodium molybdate: 0.25 g / l as molybdenum
Hydrochloric acid: 0.002 g / l as chloride ion
Ferric sulfate ... 0.20 g / l as metallic iron
Chromium sulfate: 0.20 g / l as trivalent chromium
Bath temperature: 25.5 ℃
Pulse cathodic electrolysis on time: 10 ms
Pulse cathode electrolysis off time ... 60ms
Pulse cathode electrolysis average plating current density: 22.5 A / dm2

[Secondary smooth plating conditions]
Copper sulfate: 45g / l as metallic copper
Sulfuric acid ... 110g / l
Bath temperature: 50.5 ℃
DC cathode electroplating current density: 18.5A / dm2

As a rust prevention treatment, a rust prevention layer was formed by immersing and drying in a chromate bath containing 3 g / L as CrO ₃ . Thereafter, an epoxy-based silane coupling agent (Silas Ace S-510, manufactured by Chisso Corporation) bathed in 0.5 wt% was applied as a thin film thereon.

The surface roughness Rz on both surfaces of the copper foil after the roughening treatment was measured based on JIS-B-0601 and listed in Table 1.
Further, the treated copper foil is cut into a square of 250 mm, and the roughened surface on the mat surface side is overlaid on a commercially available polyphenylene ether (PPE) resin substrate (equivalent to Megtron-6 prepreg manufactured by Panasonic Electric Works) and heated at 180 ° C. The uniformity of the roughening treatment was evaluated from the measured values of the peel strength using the laminated samples. The presence or absence of abnormal roughening treatment was evaluated by visual observation of the remaining copper on the substrate surface after the entire surface etching with an optical microscope.

  The uniformity evaluation (variation chart evaluation) of the roughening treatment is performed by measuring the peel strength by a measurement method defined in JIS-C-6481, which is used for measuring the peel adhesion to the base material. If there is no “difference” between the value and the minimum value and the line is drawn and peeled straight without chart shake, the evaluation is “◎” as being excellent in roughening uniformity, and chart shake is 0.02 kg / Within 1 cm, the evaluation is “◯”, within 0.05 kg / cm, the evaluation is “Δ”, and when it exceeds 0.05 kg / cm, the evaluation is “×” and the numerical value variation of the adhesion strength is converted into Table 1. Described.

  The remaining copper is ◎ when there is no residual copper per unit area (0.5 mm × 0.5 mm) after etching the surface of the laminated substrate, ◯ when it is hardly seen, and when it is seen somewhat. Δ, the case of being noticeable was evaluated as x and listed in Table 1.

  The copper foil (made by Furukawa Electric Co., Ltd.) having a glossy surface side roughness of 2.5 μm in surface roughness Rz and a room temperature elongation of 5.2% of the untreated electrolytic copper foil before drilling used in Example 1 Using the double-sided glossy electrolytic copper foil), the same roughening and surface treatment as in Example 1 were performed so that the surface roughness of both surfaces after the secondary roughening surface treatment was 3.0 μm or less in Rz. Evaluation measurement similar to 1 was performed. The results are also shown in Table 1.

  Instead of the untreated electrolytic copper foil before drilling used in Example 1, a rolled foil of oxygen-free copper having a thickness of 18 μm, an elongation at room temperature of 4.2%, and a surface roughness of both surfaces of Rz of 0.8 μm Except for using (Furukawa Electric Co., Ltd.), roughening and surface treatment were performed after drilling in the same manner as in Example 1, and the same evaluation measurement as in Example 1 was performed. The results are also shown in Table 1.

  A copper-tin alloy foil (manufactured by Furukawa Electric Co., Ltd.) having a thickness of 18 μm, a normal temperature elongation of 3.5%, and a tin content of 0.15% was used. Was applied. In addition, except that the composition of the electrolytic solution in the roughening treatment step is different, the roughening treatment and the surface treatment are performed so that the obtained treated surface has a roughness Rz of 3.0 μm or less in the same manner as in Example 1. The same evaluation measurement as in Example 1 was performed. The results are also shown in Table 1.

[Primary coarse particle formation bath composition and treatment conditions]
Copper sulfate: 23.5 g / l as metallic copper
Sulfuric acid ... 100g / l
Sodium molybdate: 0.25 g / l as molybdenum
Hydrochloric acid: 0.002 g / l as chloride ion
Stannous sulfate ... 2.35g / l as tin
Ferric sulfate ... 0.20 g / l as metallic iron
Chromium sulfate: 0.20 g / l as trivalent chromium
Bath temperature: 25.5 ℃
Pulse cathodic electrolysis on time: 10 ms
Pulse cathode electrolysis off time ... 60ms
Pulse cathode electrolysis average plating current density: 22.5 A / dm2

[Secondary smooth plating treatment conditions] (Check the conditions here again.)
Copper sulfate: 45g / l as metallic copper
Stannous sulfate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 4.5g / l as tin
Sulfuric acid ... 110g / l
Bath temperature: 50.5 ℃
DC cathode electroplating current density: 18.5A / dm2

Comparative Example 1

  Both sides of the perforated copper foil used in Example 1 were subjected to DC cathodic electrolysis instead of pulse treatment with the same bath composition as in Example 1, and the roughness Rz of both roughened surfaces obtained was 3.0 μm or less. The same processing as in Example 1 was performed except that the processing was performed, and the same evaluation measurement as in Example 1 was performed. The results are also shown in Table 1.

Comparative Example 2

  The same evaluation measurement as in Example 1 was performed except that the same treatment as in Comparative Example 1 was performed on both surfaces of the perforated copper foil used in Example 2. The results are also shown in Table 1.

Comparative Example 3

  The same evaluation measurement as in Example 1 was performed except that the same processing as in Comparative Example 1 was performed on both surfaces of the perforated rolled copper foil used in Example 3. The results are also shown in Table 1.

Comparative Example 4

The same evaluation measurement as in Example 1 was performed, except that both surfaces of the rolled alloy foil used in Example 4 were subjected to the same treatment as in Comparative Example 1. The results are also shown in Table 1.

Comparative Example 5

  Foil is made into a middle profile (MP) shape that is classified as an IPC standard by columnar crystals according to electrolytic foil-making conditions, and the surface roughness Rz on the mat surface side is 3.8 μm, and the surface roughness Rz on the gloss surface side is 1.8 μm. The same treatment and evaluation measurement as in Example 1 were performed on the MP-18 μm non-perforated copper foil by direct current electrolytic treatment. The results are also shown in Table 1.

As is apparent from Table 1, the copper foils of Examples 1 to 4 had the same surface roughness on both the front and back surfaces, and the roughening characteristics on both sides were comparable.
Compared with the examples, the copper foils of Comparative Examples 1 to 5 have better adhesion strength than the examples, but are inferior to the examples in terms of variation in adhesion strength and remaining copper, and the active material laminated on the negative electrode current collector From the viewpoint of binding with a uniform thickness, when it is employed as a current collector for a secondary battery, a problem occurs in charge / discharge characteristics.
In addition, in the general-purpose electrolytic copper foil of Comparative Example 5, since the surface roughness of the front and back of the untreated foil was greatly different, the roughened state on both sides could not be brought close to each other by the roughening treatment. For this reason, it is difficult to adopt a copper foil that has a considerable difference in surface roughness between the front and back surfaces of the untreated copper foil. The

  As described above, the perforated copper foil roughened by the pulse cathodic electrolysis of the present invention can be manufactured with substantially the same characteristics on both sides, so as a copper foil as a current collector for a lithium ion secondary battery. Is preferred.

DESCRIPTION OF SYMBOLS 1 1st roughening process (pulse cathode electrolytic roughening process) tank 2 2nd copper plating process (smooth plating process) tank 3 3rd surface treatment (rust prevention process) tank 4 4th surface treatment (silane coupling process) tank A untreated copper foil B primary treated copper foil C secondary treated copper foil D tertiary treated copper foil E quaternary treated copper foil F surface roughened copper foil

Claims (13)

On the surface of an untreated copper foil or an untreated copper alloy foil in which a through hole having an area of an opening portion of one hole of 0.01 mm ² or less is formed, a primary rough comprising copper or a copper alloy by pulse cathode electrolytic treatment A perforated roughened copper for a lithium ion secondary battery current collector is provided with a secondary treatment layer made of copper or a copper alloy by a smooth plating process on the primary roughened layer. Foil. The surface of the untreated copper foil or untreated copper alloy foil in which a through hole having an opening portion of one hole having a diameter of 0.01 mm ² or less is formed on the surface of the untreated copper or untreated by pulse cathode electrolytic treatment. A primary roughening treatment layer made of the same metal as the copper alloy foil is provided, and a secondary treatment layer made of copper or the same metal as the copper alloy foil is provided on the primary roughening treatment layer by smooth plating treatment. A perforated roughened copper foil for a current collector of a lithium ion secondary battery. The perforated rough for a lithium ion secondary battery current collector according to claim 1 or 2, wherein the total area of the opening portions of the through holes is 55% or less with respect to the area of the untreated foil before the through holes are formed. Processed copper foil. The lithium ion secondary battery collection according to claim 1 or 2, wherein a thickness of the untreated copper foil or untreated copper alloy foil in which the through-holes are formed is 8 to 35 µm, and a conductivity is 85% IACS or more. Electrically perforated and roughened copper foil. The perforated roughened copper foil for a lithium ion secondary battery current collector according to claim 1 or 2 , wherein the copper alloy foil is a foil made of an alloy of copper and tin. The lithium ion secondary battery current collector according to claim 1, wherein the surface roughness of the secondary treatment layer is 3.0 μm or less in terms of surface roughness Rz defined in JIS-B-0601. Perforated roughened copper foil. The lithium ion secondary battery collection according to claim 1 or 2, wherein a rust preventive layer is provided on the surface of the secondary treatment layer, and a protective layer is provided on the surface of the rust preventive layer. Electrically perforated and roughened copper foil. 8. The lithium ion secondary battery current collector according to claim 7, wherein the rust preventive layer is made of chromate, and a chromium adhesion amount of the chromate rust preventive layer is 0.005 to 0.025 mg / dm ² as metal chromium. Perforated roughened copper foil. The said protective layer consists of silane coupling agents, and the adhesion amount of this silane coupling agent is 0.001-0.015 mg / dm < ² > as silicon, For lithium ion secondary battery collectors of Claim 7 Perforated roughened copper foil. Pulse the primary roughened layer made of copper or copper alloy on the surface of the untreated copper foil or untreated copper alloy foil in which the through hole having an opening area of one hole of 0.01 mm ² or less is drilled. A method for producing a perforated roughened copper foil for a lithium ion secondary battery current collector, which is provided by cathodic electrolysis and a secondary treatment layer made of copper or a copper alloy is provided on the primary roughening treatment layer by a smooth plating treatment . A primary made of copper or the same metal as the copper alloy foil on the surface of the untreated copper foil or untreated copper alloy foil in which a through-hole having an opening area of one hole of 0.01 mm ² or less is formed. Lithium ion secondary battery current collector provided with a roughening treatment layer by pulse cathodic electrolysis treatment and a secondary treatment layer made of the same metal as copper or the copper alloy foil on the primary roughening treatment layer by smooth plating treatment A method for producing body-perforated roughened copper foil. The hole for a lithium ion secondary battery current collector according to claim 10 or 11, wherein a rust preventive layer is provided on the surface of the secondary treatment layer with a rust preventive agent, and a protective layer is provided on the surface of the rust preventive layer with a coupling agent. A method for producing a roughened copper foil.   Lithium ion obtained by laminating a silicon-based active material on the surface of the roughened copper foil according to claim 1 or 2, or the surface of the roughened copper foil produced by the production method according to claim 10, 11 or 12. Secondary battery negative electrode.

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