WO2005057693A1

WO2005057693A1 - Negative electrode collector for nonaqueous electrolyte secondary battery

Info

Publication number: WO2005057693A1
Application number: PCT/JP2004/010016
Authority: WO
Inventors: Tomohiro Sakata; Kazuko Taniguchi; Makoto Dobashi
Original assignee: Mitsui Mining & Smelting Co., Ltd.
Priority date: 2003-12-12
Filing date: 2004-07-14
Publication date: 2005-06-23
Also published as: TW200520291A

Abstract

[PROBLEMS] To obtain a collector having, despite being thin, a high tensile strength at low cost. [MEANS FOR SOLVING PROBLEMS] There is provided a negative electrode collector for nonaqueous electrolyte secondary battery characterized in that at least one major surface of an electrolytic foil of a metal material exhibiting low capability of lithium compound formation is furnished with a hard nickel plating layer. This hard nickel plating layer is formed by electroplating in a plating bath containing a nickel salt and an ammonium salt. The metal material is constituted of, for example, any of copper, iron, cobalt, nickel, zinc and silver or an alloy of at least two members thereof.

Description

Specification

Negative electrode current collector for non-aqueous electrolyte secondary batteries

Technical field

The present invention relates to a negative electrode current collector for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

Background art

[0002] Recently, research has been conducted on using a high-capacity active material such as a silicon-based material or a tin-based material as a negative electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. There. When these active materials are used, the stress applied to the current collector due to the volume expansion of the active material accompanying the charging and discharging of the battery is larger than when using a conventional carbon-based active material. Therefore, there is a problem that the current collector is wrinkled or the current collector is deformed. When the current collector is wrinkled or deformed, the adhesion between the current collector and the active material is reduced, and the battery life is shortened. As a countermeasure, a higher strength current collector that can withstand the stress applied by volume expansion is required. Thickening the current collector is one of the ways to increase the strength. However, even if the current collector is made thicker, a significant improvement in strength (tensile strength) cannot be expected, and this has the disadvantage of lowering the energy density of the battery instead of the strength.

[0003] Representative examples of a metal foil used as a current collector include those manufactured by a rolling method and those manufactured by an electrolytic method. Among the metal foils manufactured by these methods, a 1 μm thick nickel foil is applied to each surface of a 20 μm thick electrolytic iron foil to increase the strength of the metal foil manufactured by the electrolytic method. The current collector thus obtained is used as a negative electrode of a lithium ion secondary battery (see Patent Document 1), or an alkaline storage battery obtained by applying a nickel or nickel alloy to the surface of a current collector made of a thin steel plate (Patent Reference 2) has been proposed. However, these current collectors have the disadvantage that the current collector strength is inferior to that of rolled copper alloy foil, judging from the composition of the nickel plating bath or the coating method.

[0004] With respect to metal foils manufactured by the rolling method, it has been proposed to use rolled copper alloy foils as current collectors (see Patent Document 3). However, rolled foils can be made thinner Therefore, it is inexpensive from the viewpoint of obtaining a thin and high-strength current collector.

[0005] Apart from Patent Documents 1 to 3, there has been proposed a lithium ion secondary battery in which a current collector made of copper is plated with nickel (see Patent Document 4). However, the technique described in this document does not aim to increase the strength of the current collector, and does not disclose the conditions for nickel knolling, so it is unclear whether the effect of improving the strength was recognized.

[0006] Furthermore, the current collector is subjected to a high-temperature and long-time heat treatment after the active material is supported on the current collector. For example, Patent Document 5 describes that it is preferable to bake the current collector supporting the active material at 400 ° C., and in this example, the baking time is set to 10 hours or the like. Therefore, the strength of the current collector after heat treatment is also required.

Patent Document 1: JP-A-6-310147

Patent Document 2: JP-A-11-233117

Patent Document 3: JP-A-2003-7305

Patent Document 4: JP-A-5-159781

Patent Document 5: JP-A-2002-260637

Disclosure of the invention

Problems to be solved by the invention

[0008] Therefore, an object of the present invention is to provide a negative electrode current collector for a non-aqueous electrolyte secondary battery, which can solve the above-mentioned various disadvantages of the related art.

Means for solving the problem

[0009] The present invention provides a hard nickel plating layer in which at least one surface of an electrolytic foil made of a metal material having a low ability to form a lithium compound is subjected to electrolytic plating using a plating bath containing a nickel salt and an ammonium salt. The object has been achieved by providing a negative electrode current collector for a non-aqueous electrolyte secondary battery, characterized in that a negative electrode current collector is formed.

[0010] The present invention also provides, as a preferred method for producing the current collector,

At least one side of the electrolytic foil made of a metal material with low lithium compound formation is electroplated using a plating bath containing 100-250 g / l nickel sulfate, 10-50 gZl ammonium chloride and 10-50 g / l boric acid. To form a hard nickel plating layer And a method for producing a negative electrode current collector for a non-aqueous electrolyte secondary battery.

Further, the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery provided with the current collector, and a non-aqueous electrolyte secondary battery provided with the negative electrode.

The invention's effect

According to the present invention, a current collector having a high tensile strength despite its thinness can be obtained at low cost. Further, according to the present invention, it is possible to obtain a current collector in which a sufficient level of high tensile strength is maintained even after heat treatment. Furthermore, by subjecting the surface of the hard nickel plating layer to a roughening treatment and / or an anti-rust treatment, the adhesion between the current collector and the active material can be increased. Further, by adjusting the thickness of the hard nickel plating layer on each surface of the electrolytic foil, it is possible to effectively prevent the occurrence of curling due to plating or internal stress inherent to the electrolytic foil. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on preferred embodiments. The negative electrode current collector for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, simply referred to as a current collector) is one in which a hard nickel plating layer is formed on at least one surface of a foil made of a metal material. An electrolytic foil is used as a foil made of a metal material. The electrolytic foil has an advantage that when the foil is made thinner, the manufacturing cost can be reduced as compared with the rolled foil.

[0014] The above-mentioned electrolytic foil is preferably thin because it can increase the energy density of the battery. From this point of view and from the viewpoint of the production cost when the rolling method is used, the electrolytic foil has a thickness force of —50 / im, particularly 3-18 μΐη, and especially 9-118 / im. . If the thickness is converted by weight per unit (when the density of copper is 8.96 g / cm ³ ), it should be 8.96-448 g / m ² , especially 80-6-161 · 3 g / m ² Power S preferred ,. The thickness of the box is measured by analyzing cross-sectional photographs taken with a micrometer or an electron microscope.

[0015] The electrolytic foil is made of a metal material having a low ability to form a lithium compound. "Low ability to form a lithium compound" means that no intermetallic compound or solid solution is formed with lithium, or even if it is formed, the amount of lithium is a very small force or very unstable. As such a metal material, for example, copper, nickel, iron, cobalt, chromium, zinc, silver or an alloy of two or more of these is used. Among these metals, it is preferable to use copper or an alloy thereof, which is a material having low electric resistance and excellent workability. Good.

[0016] A conventionally known technique may be used without particular limitation on the method for producing an electrolytic foil. The electrolytic foil is generally obtained by using a rotating drum as a cathode, performing electrolysis in an electrolytic bath containing ions of the above-mentioned metal material, depositing the metal material on the drum peripheral surface, and peeling the deposited metal material. When the electrolytic foil is, for example, a copper foil, a sulfuric acid acidic copper sulfate electrolytic bath can be used.

[0017] As another method for producing the electrolytic foil used in the present invention, a thin release agent layer is formed on one surface of a conductive carrier foil, and a metal material having a low ability to form a lithium compound is electrolytically deposited thereon. There is also a method of obtaining an electrolytic foil with a foil. In the electrolytic foil with a carrier foil, since the carrier foil functions as a support for the electrolytic foil, there is no occurrence of blemishes or the like in the manufacturing process even when the electrolytic foil is made extremely thin. According to this manufacturing method, the electrolytic foil can be made extremely thin, so that a high density and a high capacity density can be obtained when the electrode is formed. There is no particular lower limit on the thickness of the electrolytic foil produced by this method, but it is about 1 / m in consideration of production stability. The upper limit of the thickness is not particularly limited.However, if an electrolytic foil having a thickness exceeding 10 / m is to be manufactured, it is not necessary to employ the present manufacturing method. The upper limit is about 10 μm. On the other hand, the conductive carrier foil preferably has a thickness of about 18-50 / m. When it is less than 18 / im, the effect as a support becomes insufficient. On the other hand, exceeding 50 / im does not have any particular effect, but rather leads to an increase in manufacturing cost. The material of the conductive carrier foil is not particularly limited as long as it has conductivity. However, considering the recyclability of the material, the material is preferably the same as that of the electrolytic foil.

As the release agent applied to the surface of the conductive carrier foil, an organic compound is preferably used, and particularly, a nitrogen-containing compound or a sulfur-containing compound is preferably used. Examples of the nitrogen-containing compound include benzotriazole (BTA), carboxybenzotriazole (CBTA), trinoletriazolone (TTA), N ,, N, monobis (benzotriazolylmethyl) urea (BTD —U) and triazole-based compounds such as 3-amino-1H-1,2,4-triazole (ATA) are preferably used. Sulfur-containing compounds include mercaptobenzothiazole (MBT), thiocyanuric acid (TCA) and 2_benzimidazole thiol (BIT). As for the method of providing the release agent layer, the conductive carrier is dissolved in a solution in which the release agent is dissolved. The foil may be dipped, or the solution may be applied on a conductive carrier foil. In this case, the concentration of the release agent is preferably 3-4 g / present when CBTA is used as the release agent. On the other hand, it is also effective to perform a chromate treatment instead of the organic compound release agent layer.

When an electrolytic foil with a conductive carrier foil is used, the hard nickel layer is preferably formed in a state where the electrolytic foil is supported on a conductive carrier foil. The method for forming the hard nickel layer will be described later. When a hard nickel layer is provided on both sides of the electrolytic foil, a hard nickel layer is formed on the surface of the electrolytic foil while the electrolytic foil is supported on the conductive carrier foil, and then the electrolytic foil is transferred to the conductive carrier foil. And then a hard nickel layer can be formed on the other side of the electrolytic foil.

[0020] A hard nickel plating layer is formed on at least one surface of the electrolytic foil. By the way, since nickel plating tends to have high strength, nickel plating or nickel alloy plating is generally called hard nickel plating as a general term (for example, see Patent Document 2). However, it should be noted that the strength (tensile strength) of nickel plating differs depending on the plating conditions, as shown in the examples described later. The hard nickel plating layer in the present invention is formed by electroplating using a plating bath containing a nickel salt and an ammonium salt. As a result of the study by the present inventors, the hard nickel plating layer formed by electroplating using this plating bath is formed by electroplating using another plating bath (for example, a Watt bath or a sulfamic acid bath). It was found that the material was harder than the formed echnoke plating layer, and as a result, it was possible to obtain a current collector having a high tensile strength. The Watts bath is a bath containing nickel sulfate, nickel chloride and boric acid, and the sulfamic acid bath is a bath containing nickel sulfamate, nickel chloride and boric acid.

[0021] Examples of the nickel salt in the plating bath used for forming the hard nickel plating layer include nickel sulfate hexahydrate. Examples of the ammonium salt include Shii-dani ammonium and the like. In addition to these components, the plating bath may contain boric acid or the like. Preferably, the concentration of nickel sulfate in the plating bath is 100-250 g / l, especially 130 190 gZl. The concentration of ammonium chloride is 10-50 g / l, especially 20 30 gZl It's preferable that there is. Preferably, the concentration of boric acid is between 10 and 50 g / l, especially between 20 and 40 g / l.

[0022] As plating conditions using the plating bath, the bath temperature is preferably 20 to 60 ° C, particularly preferably 30 to 40 ° C, and the current density is preferably 1 to 50 A / dm ² , particularly 5 to 5 ° C. Sile, it preferred to be a 15dm ^2. The pH is preferably 26, especially 35.

Conventionally, hard nickel plating using the above-mentioned plating bath is an alternative to hard chrome plating used for abrasion parts or overfilling of balta, such as a part with excessive ij, or used in combination with hard chrome plating. It was the main application (see, for example, “Surface Treatment Handbook” written by Sakae Tajima, published on November 15, 1955, Sangyo Tosho Co., Ltd., page 143). However, hard nickel plating has not been conventionally formed on the surface of a thin material such as a metal foil, and the strength (tensile strength) against elongation of the metal foil is increased by forming the force on the surface of the metal foil. It was not known to increase. The characteristics of such hard nickel plating were first discovered by the present inventors.

[0024] The hard nickel plating layer formed using the plating bath has a thickness of 0.5 018 μ 各 η on each surface of the electrolytic foil, and particularly, 11 1010 / im. It is preferable in terms of the balance between increasing the energy density of the battery and increasing the strength of the current collector. For the same reason, when hard nickel plating layers are provided on both sides of the electrolytic foil, the total thickness of the plating layers is preferably 118 / im, particularly preferably 2-12 μΐη. The thickness of the hard nickel plating layer can be measured by observing a SIM image by FIB cross-section processing or by taking an element mapping image of the cross section of the electrolytic foil with an electron microscope and analyzing it.

By the way, the electrolytic foil has a smooth surface called a glossy surface and a rough surface called a matte surface. The glossy surface is the surface facing the rotating drum or carrier foil used as a cathode during electrolysis, and the matte surface is the surface that was in contact with the electrolyte. When the hard nickel plating layer is formed only on one surface of the electrolytic foil used in the present invention, the plating layer may be formed on either the glossy surface or the matte surface. Considering that the adhesion to the active material is improved, it is preferable to form a hard nickel plating layer on the matte surface, which is a rough surface, and to form the active material layer on the plating layer. Further, by forming a hard nickel plating layer on the mat surface, curling of the electrolytic foil can be prevented. When a hard nickel plating layer is formed on one surface of the electrolytic foil, for example, on a glossy surface, the electrolytic foil may be deformed into a curl shape with the plating layer side inside. This deformation becomes conspicuous when the thickness of the electrolytic foil is 12 / im or less and the thickness of the hard nickel plating layer is 3 μm or more. In order to prevent this curl, it is preferable to form a hard nickel plating layer on each surface of the electrolytic foil (that is, on each of the matte surface and the glossy surface). In this case, curling can be effectively prevented by making the thickness of the plating layer on one side smaller than the thickness of the plating layer on the other side. In particular, by making the thickness of the hard nickel plating layer on the glossy surface side smaller than the thickness of the hard nickel plating layer on the matte surface side, curling can be more effectively prevented. The reason for this is that the effect of suppressing the force caused by the internal stress inherent in the electrolytic foil occurs. This effect is obtained when the thickness of the hard nickel plating layer on the matte side becomes preferably 1.1 to 1.2 times, more preferably 1.3 to 1.7 times the thickness of the hard nickel plating layer on the glossy side. It will be even more pronounced. In this case, the thickness of the hard nickel plating layer on the matte side is preferably 0.5 · 10 / im, particularly preferably 16 μΐη, and the thickness of the hard nickel plating layer on the glossy side is 0.3. — 8 / im, preferably 0.8—8 / im.

It is preferable to provide an intermediate layer between the electrolytic foil and the hard nickel layer. As the intermediate layer, a layer containing cobalt or iron is preferred, and a layer coated with cobalt or iron alone is particularly preferred. When the electrolytic foil and the hard nickel layer are directly laminated without providing an intermediate layer, if the heat treatment is carried out at a temperature of 400 ° C or more for a long time in the subsequent electrode manufacturing process, the hard nickel layer and the electrolytic foil will interdiffuse There is a concern that the Kirkendall effect of moving will occur and the strength that the hard nickel layer should have originally will be reduced. It is known that when the Kirkendall effect occurs, voids occur at the diffusion boundary between the hard nickel layer and the electrolytic foil. The locations where voids exist are locations where tensile stress is concentrated, and the foil is likely to break. This phenomenon is remarkable when a copper foil or a copper alloy foil is used as the electrolytic foil. Therefore, when a copper foil or a copper alloy foil is used as the electrolytic foil, it is particularly preferable to provide an intermediate layer. The thickness of the intermediate layer is generally about 0.1 to 0.5 zm, as long as the intermediate layer can prevent mutual occurrence of the hard nickel layer and the electrolytic foil. The material of the intermediate layer is limited to cobalt or iron as long as it has an effect of preventing mutual diffusion between the hard nickel layer and the electrolytic foil. What? The intermediate layer is preferably formed by electroplating from the viewpoint of simplifying the manufacturing process. When the intermediate layer is provided, it is preferable that the material of the intermediate layer is different from the material of the electrolytic foil.

[0028] The current collector of the present invention having the above-described structure is a thin type having a thickness of 3 to 50 µm, particularly 14 to 24 µm. Preferred from the viewpoint of obtaining

. The current collector of the present invention has a high tensile strength despite its thinness and the use of an electrolytic foil as a base material. For example, when the electrolytic foil is made of copper, tensile strength 600N / mm ² or more, a high value of particular 700NZmm ² or more. There is no particular upper limit on the tensile strength, but if it is 800-1000 N / mm ² , especially around 900 NZmm ² , wrinkles may occur on the current collector due to expansion and contraction of the active material, It is possible to effectively prevent the body from being cut off. If the electrolytic foil is made of copper, its elongation is 110. /. And particularly preferably 2 to 8%.

[0029] The tensile strength and elongation are measured using an Autograph AG-I manufactured by Shimadzu Corporation under the conditions of a gauge length of 50 mm and a tensile speed of 50 mm / min.

After the formation of the hard nickel plating layer, the surface of the plating layer may be roughened. This improves the adhesion between the hard nickel plating layer and the active material layer formed thereon. In the roughing treatment, after performing a plating treatment for forming a granular metal on the surface of the hard nickel plating layer, the granular metal is compacted so as not to impair the uneven shape due to the granular metal. A plating process of covering with a dense plating layer is included. The first plating is called so-called plating, and the second plating is called so-called plating. Such roughening treatment is known as a method for roughening the surface of a copper foil for a printed circuit, and is disclosed, for example, in Japanese Patent Publication No. 53-39376. Burning is plating in which a granular metal is precipitated by a current near the critical current density. Covering is a method in which a dense non-granular plating layer is formed by a current at or below the critical current density. It is plating that is deposited so as to cover the powdered metal.

[0031] In the case of performing a plating treatment with copper, for example, as a roughing treatment, the first-stage burn plating includes a plating bath containing 20 to 80 g / l of copper sulfate pentahydrate and 50 to 150 g / l of sulfuric acid. Can be used at a current density of 10-20 A / dm ² . The latter cover is copper sulfate The plating can be performed at a current density of 5 to 3 OA / dm ² using a plating bath containing 200 to 300 g / l of pentahydrate and 50 to 150 g / l of sulfuric acid.

[0032] The roughness treatment layer formed on the surface of the hard nickel plating layer has a ten-point average surface roughness R zjis (JIS B0601) of preferably 2 to 12 zm, more preferably 418 to 8 μm. The coarse roughness is also the same. The ten-point average surface roughness Rzjis is the height from the highest peak to the fifth peak, measured in the direction of the longitudinal magnification from the average line of the part extracted by the reference length from the longitudinal section curve of the roughened layer. It is the difference between the average of the absolute values of the altitude and the average of the absolute values of the depths of the valleys from the lowest to the fifth. Rzjis can be measured, for example, using a surface roughness' contour measuring instrument SEF-30D manufactured by Kosaka Laboratory Co., Ltd.

[0033] Instead of the roughening treatment, the surface of the hard nickele-coated layer may be subjected to an anti-dust treatment. Alternatively, in addition to the roughening treatment, the surface of the roughening treatment layer may be subjected to an anti-rust treatment. This adhesion prevention also improves the adhesion between the hard nickel plating layer and the active material layer formed thereon. Examples of the prevention treatment include (i) metal plating treatment, (ii) chromate treatment, and (iii) silane coupling treatment. In the metal plating process, zinc, nickel, cobalt or their alloys are coated on the surface of a hard nickel plating layer (when the roughing process is not performed) or a roughened layer (when the roughening process is performed). To prevent corrosion of the hard nickel plating layer and the roughened layer. It is preferable to perform zinc or zinc alloy plating from the viewpoint that the effect of preventing corrosion of the hard nickel plating layer and the roughening treatment layer is particularly high. Specifically, alloy plating such as zinc-copper, zinc-nickel, zinc-cobalt, zinc-nickel-copper, zinc-nickel-cobalt, zinc-copper-tin and the like can be mentioned. For example, in the case of zinc plating, contain zinc at 16 g / l, potassium pyrophosphate at 50-200 g / l, adjust the pH to 10-12, and use a plating bath with 0.3-1AZdm It can be performed under the condition of the current density of ² .

[0034] In the chromate treatment, a hard nickel plating layer (a case where the roughening treatment is not performed) or a roughening treatment layer (the case where the roughening treatment is performed) is performed using a solution containing chromate or dichromate as a main component. ) To form a protective coating on the surface. The heat protection film formed by this treatment is made of a chromium oxide layer. The chromate treatment is specified in, for example, JIS Z 0103. Specific conditions for the chromate treatment includes the chromic acid 0. 5- 2gZl, pH by using a plated bath adjusted to 11 one 13, it is carried out at a current density of 0. 5- 2A / dm ² Can be. [0035] In the silane coupling treatment, the surface of the hard nickel plating layer (when the roughing treatment is not performed) or the surface of the roughening treatment layer (when the roughing treatment is performed) is treated with a silane coupling agent. Treated with a silicon-containing compound commonly known as For example, the general formula R-SiX (X is

Three

R is a substituent having a functional group such as a butyl group, an epoxy group, or an amino group, which easily reacts with an organic substance. ) Can be used as a silane coupling agent. A silane coupling agent having a concentration of, for example, 3-lOg / 1 may be used. The silane coupling agent having the concentration may be applied to the hard nickel plating layer and dried at a predetermined temperature for a predetermined time.

[0036] There is no particular limitation on the order of the roughing treatment and the protection treatment. For example, only the roughing process may be performed. Alternatively, only one of the (i) one (m) protection processes may be performed, or two or more of the (i) one (m) protection processes may be combined. When two or more of the (i) first (in) protection treatments are combined, for example, a chromate treatment can be performed after the metal plating treatment, or a silane coupling treatment can be performed after the metal plating treatment. After the metal plating, the chromate treatment and the silane coupling treatment can be performed in this order. Further, a chromate treatment may be performed first, followed by a silane coupling treatment.

[0037] The roughening treatment and the prevention treatment can be combined. In particular, it is preferable to first perform a roughening treatment and then perform a rust prevention treatment. The order of the prevention processing can be as described above. It should be noted that the tensile strength of the current collector of the present invention does not substantially change even if the roughing treatment and / or the anti-rust treatment is performed.

[0038] A layer containing a negative electrode active material is formed on the surface of the current collector of the present invention to produce a negative electrode for a non-aqueous electrolyte secondary battery. Examples of the negative electrode active material include a material having a high ability to form a lithium compound. For example, there are Group 13 and Group 14 elements of the periodic table. Specifically, carbon, silicon, tin, germanium, aluminum, or an alloy thereof may be used. Among these, it is particularly preferable to use tin or silicon or an alloy thereof.

[0039] The negative electrode active material is carried by being deposited on the current collector by electrolysis. Alternatively, it is also supported by applying a paste containing particles of the negative electrode active material on a current collector and drying. Sintering may be performed after application of the paste. As is clear from the examples described later, ADVANTAGE OF THE INVENTION According to the collector of this invention, even if this collector is exposed to high temperature by sintering, there exists an advantage that fall of tensile strength can be suppressed. The effect is particularly great when a hard nickel plating layer is provided on both sides of the electrolytic foil.

The negative electrode provided with the current collector of the present invention is used together with a known positive electrode, a separator, and a non-aqueous electrolyte to form a non-aqueous electrolyte secondary battery. The positive electrode is prepared by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent to prepare a positive electrode mixture, applying the mixture to a current collector, drying the mixture, rolling, pressing, and Obtained by cutting and punching. As the positive electrode active material, a conventionally known positive electrode active material such as a lithium nickel composite oxide, a lithium manganese composite oxide, and a lithium control composite oxide is used. As the separator, a synthetic resin nonwoven fabric, a polyethylene or polypropylene porous film, or the like is preferably used. In the case of a lithium secondary battery, the nonaqueous electrolyte is a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. Examples of lithium salts include, for example, LiClO, LiAlCl, LiPF, LiAsF, LiSbF, LiSCN, LiCl, UBr, UI, LiCF SO, Li

4 4 6 6 6 3 3

C F SO is exemplified.

4 9 3

[0041] The present invention is not limited to the above embodiment. For example, in the present invention, as described above, the hard nickel plating layer may be subjected to a roughening treatment, but instead of or in addition to this, various hardening treatments may be performed to the hard nickel plating layer. Good. Examples of the prevention treatment include (i) a plating treatment with zinc or a zinc alloy, (ii) a chromate treatment, and (m) a silane coupling treatment. Example

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to such examples.

Example 1

An 18 zm thick VLP foil (trade name) manufactured by Mitsui Kinzoku Mining was used as a current collector. This foil is an electrolytic copper foil obtained using a rotating drum as a cathode. Electroplating was performed on the matte surface of the electrolytic copper foil using a plating bath having the following composition to form a hard nickel plating layer having a thickness of 3 / im. The bath temperature was 50 ° C. and the current density was 5 A / dm ² . pH was 4. Thus, a negative electrode current collector was obtained. [Composition of Plating Bath]

* Nickel sulfate hexahydrate 162g / l

'Ammonia chloride 25g / l

'Boric acid 30g / l

[Comparative Example 1]

A negative electrode current collector was obtained in the same manner as in Example 1 except that a sulfamic acid bath having the following composition was used instead of the plating bath used in Example 1. Bath temperature 50 ° C, current density was lOAZd m ^2.

[Composition of Sulfamic Acid Bath]

• 60 weight ^_0/0 nickel sulfamate solution LOOOg / 1

• Nickel chloride hexahydrate 5gZl

'Boric acid 40gZl

[Comparative Example 2]

A negative electrode current collector was obtained in the same manner as in Example 1 except that a nickel-phosphorus alloy plating bath having the following composition was used instead of the plating bath used in Example 1. Bath temperature is 50 ° C, current density is

5 was A / dm ^2.

[Composition of nickel-phosphorus alloy plating bath]

* Nickel sulfate hexahydrate 56g / l

• Nickel chloride hexahydrate 45g / l

NiCO2Νί (Νί) ηΟΗ Ο48g / l

3 2 2

'' Phosphorous acid 41g / l

'' Phosphoric acid 49g / l

[Comparative Example 3]

The electrolytic copper foil used in Example 1 was used as it was. No nickel plating was performed. (Example 2)

VLP foil (trade name) manufactured by Mitsui Kinzoku Mining having a thickness of 12 zm was used as a current collector. This foil is an electrolytic copper foil obtained using a rotating drum as a cathode. Electroplating was performed on the matte surface of the electrolytic copper foil using the same plating bath as in Example 1, and a 3 zm thick hard nickel A plating layer was formed. The plating conditions were a bath temperature of 35 ° C., a current density of 10 A / dm ² , and a pH of 4. Next, a hard nickel plating layer having a thickness of 2 / im was formed on the glossy surface under the same conditions. Thus, a negative electrode current collector was obtained.

[Example 3]

The same electrolytic copper foil as in Example 2 was used as a current collector. A 0.3 xm cobalt intermediate layer was formed on both sides of the electrolytic copper foil by electrolytic plating. Next, the same hard nickel layer as in Example 2 was formed. The bath composition and plating conditions for cobalt plating are as follows.

[Composition of cobalt plating bath]

• Cobalt sulfate hexahydrate 180g / l

• Boric acid 30gZl

• Flocculant 0.lg / 1

(Aggregating agent is acrylamide polymer)

[Cobalt plating conditions]

• Bath temperature 35 ° C

• pH 4

'' Current density 10A / dm ²

, Stirring

Example 4

The same electrolytic copper foil as in Example 2 was used as a current collector. Iron intermediate layers of 0.5 μΐη were formed on both sides of the electrolytic copper foil by electrolytic plating. Next, the same hard nickel layer as in Example 2 was formed. The bath composition and plating conditions for iron plating are as follows.

[Composition of iron plating bath]

• Iron sulfate heptahydrate 180gZl

• Boric acid 30gZl

• Flocculant 0.lg / 1

(Aggregating agent is acrylamide polymer) [Iron plating conditions]

• Bath temperature 30 ° C

• pH 4

• Current density 5AZdm ²

• With stirring

[Reference Example 1]

A negative electrode current collector was obtained in the same manner as in Example 1 except that a cobalt plating layer was formed using a plating bath having the following composition instead of the plating bath used in Example 1. The plating conditions were a bath temperature of 40 ° C., a current density of 10 AZdm ² , and a pH of 4.

[Composition of Cobalt Plating Bath]

• Cobalt sulfate hexahydrate 281gZl

'' Cobalt chloride hexahydrate 47gZl

'Boric acid 40g / l

[Reference Example 2]

Rolled copper alloy foil (composition Ni3. Owt%, SiO. 65 wt%, MgO. 15 wt%, balance Cu. Thickness 1

8 / im) was used as the negative electrode current collector.

[Performance evaluation]

For the negative electrode current collectors obtained in Examples 1 and 4, Comparative Example 1 and 3, and Reference Examples 1 and 2, the tensile strength and elongation before and after heat treatment were measured by Shimadzu Corporation. The measurement was carried out using an autograph AG-I manufactured by Toshiba Corporation. The measurement conditions were a distance between gauge marks of 50 mm and a tensile speed of 50 mm / min. The conditions of the heat treatment were 400 ° C. in vacuum for 5 hours. However, in Examples 3 and 4, the heat treatment was performed for 10 hours. The results are shown in Table 1.

[0057] [Table 1]

As is clear from the results in Table 1, the current collector of Example 1 shows higher tensile strength before and after the heat treatment than the current collectors of Comparative Examples 1 to 3. As is clear from the comparison between Example 1 and Reference Example 1, the current collector of Example 1 had the same tensile strength as the current collectors of Reference Examples 1 and 2 before and after the heat treatment. It turns out that it shows. The current collector of Reference Example 1 is inferior to the current collector of the present invention in that the current collector has high strength but has a high manufacturing cost due to the presence of the cobalt plating layer. The current collector of Reference Example 2 also has high strength, but the thin rolled foil is inferior to the current collector of the present invention in that the production cost is high. As is clear from the comparison between Example 1 and Example 2, the current collector of Example 2 in which the hard nickel plating layers were provided on both surfaces of the electrolytic foil was provided with the hard nickel layer only on one surface of the electrolytic foil. It can be seen that despite having a smaller total thickness than the current collector of Example 1, the current collector exhibits higher tensile strength than the current collector. Furthermore, as is clear from the comparison between Examples 3 and 4 and Examples 1 and 2, the heat treatment time in Examples 3 and 4 is twice as long as that in Examples 1 and 2. It can be seen that the tensile strength after the heat treatment maintained a value equal to or higher than that of Examples 1 and 2. Therefore, the current collector according to the present invention has a high tensile strength even if it is made thin, and can be manufactured at low cost, and can be applied as a new negative electrode current collector for a nonaqueous electrolyte secondary battery.

Claims

The scope of the claims

[I] At least one surface of an electrolytic foil made of a metal material having a low ability to form a lithium compound is subjected to electrolytic plating using a plating bath containing a nickel salt and an ammonium salt to form a hard nickel plating layer. Negative electrode current collector for a non-aqueous electrolyte secondary battery

[2] The current collector according to claim 1, wherein the metal material is made of copper, iron, cobalt, nickel, zinc, or silver, or an alloy of two or more thereof.

3. The current collector according to claim 1, wherein the metal material is made of copper or an alloy thereof.

4. The method according to claim 1, wherein an intermediate layer capable of preventing mutual diffusion between the electrolytic foil and the hard nickel layer is provided between the electrolytic foil and the hard nickel plating layer. Current collector.

5. The current collector according to claim 4, wherein the intermediate layer is a layer containing cobalt or iron.

[6] The current collector according to any one of [1] to [5], wherein the thickness of the electrolytic foil is 110 / im, and the total thickness of the plating layer is 118 / im. .

7. The current collector according to claim 1, wherein the metal material is copper, and the tensile strength of the current collector is not less than 00 N / mm ² .

[8] The current collector according to any one of [1] to [7], wherein the surface of the plating layer is subjected to a roughening treatment.

[9] The current collector according to any one of [1] to [8], wherein a surface of the plating layer is subjected to a heat-proof treatment.

[10] The plated layer is formed on each of the matte surface and the glossy surface of the electrolytic foil, and the thickness of the plating layer on one side is smaller than the thickness of the plating layer on the other side. Item 10. The current collector according to any one of Items 1 to 9.

[II] The current collector according to claim 10, wherein the thickness of the plating layer on the glossy side is smaller than the thickness of the plating layer on the matte side.

[12] A method for producing a negative electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1,

At least one surface of an electrolytic foil made of a metal material having a low ability to form a lithium compound has 100-250 g / l of nickel sulfate, 10-50 g / l of ammonium chloride and 10-50 g / l of A method for producing a negative electrode current collector for a non-aqueous electrolyte secondary battery, comprising performing electrolytic plating using a plating bath containing sulfuric acid, and forming a hard nickel plating layer.

[13] A negative electrode for a non-aqueous electrolyte secondary battery, comprising the negative electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1.

14. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 13, wherein a silicon-based material or a tin-based material is used as the negative electrode active material.

[15] A non-aqueous electrolyte secondary battery comprising the negative electrode for a non-aqueous electrolyte secondary battery according to claim 13.