JP2010103061A - Negative electrode copper alloy foil of secondary battery and manufacturing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode copper alloy foil of a secondary battery which is excellent on an adhesive property to an active material, and a manufacturing method for a negative electrode copper alloy foil of a secondary battery. <P>SOLUTION: The negative electrode copper alloy foil 1 of a secondary battery functioned as a negative electrode for a secondary battery by preparing an active material layer 40 has a copper alloy foil 10 expanding and contracting in response to expansion and contraction in the plane direction of the active material layer 40, and a plating core 20 formed on the surface of the copper alloy foil 10 as a core of copper plating. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a negative electrode copper alloy foil for secondary batteries and a method for producing a negative electrode copper alloy foil for secondary batteries. In particular, the present invention relates to a negative electrode copper alloy foil for lithium ion secondary batteries and a method for producing a negative electrode copper alloy foil for lithium ion secondary batteries.

  A conventional negative electrode for a lithium ion secondary battery includes a current collector and a layer made of a carbon or graphite material and including a binder made of an active material and a thermoplastic resin provided on the current collector. The active material is Sn There is known a negative electrode for a lithium ion secondary battery, which is made of an alloy powder containing bismuth and the binder is made of a resin having an elastic modulus of 3.0 GPa or more (see, for example, Patent Document 1).

Since the negative electrode for lithium ion secondary batteries described in Patent Document 1 uses an alloy powder containing Sn as an active material, a lithium ion secondary battery that can exhibit good charge / discharge cycle characteristics can be provided. When the active material is formed mainly of Sn, the theoretical discharge capacity (maximum capacity) of the active material made of a carbon material such as a carbon material or a graphite material is 372 mAh / g or more (for example, Li _4.4 Sn). About 1000 mAh / g) can be expected.

JP 2007-149604 A

  However, the negative electrode for a lithium ion secondary battery according to Patent Document 1 uses Sn whose volume expands about 3.5 times when lithium ions are occluded, and this is a case where an alloy powder containing Sn is added to a binder. However, it is difficult to completely avoid peeling and dropping of the active material from the current collector due to repeated charge / discharge cycles. In particular, when the capacity of the lithium ion secondary battery is increased by reducing the ratio of the binder (carbon material), an increase in volume change due to Sn is inevitable, and the active material and the current collector are not charged during charging and discharging. In some cases, the battery characteristics may be deteriorated due to the occurrence of peeling.

  Therefore, the objective of this invention is providing the manufacturing method of the negative electrode copper alloy foil for secondary batteries excellent in the adhesiveness with respect to an active material, and the negative electrode copper alloy foil for secondary batteries.

  In order to achieve the above object, the present invention is a negative electrode copper alloy foil for a secondary battery that functions as a negative electrode for a secondary battery by providing an active material layer, and according to expansion and contraction in the planar direction of the active material layer Provided is a negative electrode copper alloy foil for a secondary battery, which includes a copper alloy foil that expands and contracts and a plating nucleus that is formed on the surface of the copper alloy foil and serves as a nucleus of copper plating.

  Moreover, the negative electrode copper alloy foil for a secondary battery may include 0.01 wt% or more and 0.06 wt% or less of Zr, and the plating nucleus may be formed of Cu and Zr.

The negative electrode copper alloy foil for a secondary battery may have a product of the maximum tensile strength of the copper alloy foil and the thickness of the copper alloy foil of 3600 N / mm ² · μm or more.

  Moreover, the said negative electrode copper alloy foil for secondary batteries may further be provided with the copper layer which is formed on a plating nucleus by copper plating using a plating nucleus as a nucleus, and has the surface roughness of 1 micrometer or more and less than 5 micrometers.

  Moreover, as for the said negative electrode copper alloy foil for secondary batteries, a plating nucleus may be formed in layered form on the surface of copper alloy foil.

  Moreover, in order to achieve the above object, the present invention provides a method for producing a negative electrode copper alloy foil for a secondary battery that functions as a negative electrode for a secondary battery by providing an active material layer, and is provided in the planar direction of the active material layer. A negative electrode copper for a secondary battery, comprising: a copper alloy foil preparation step for preparing a copper alloy foil that expands and contracts according to expansion and contraction; and a plating nucleus formation step for forming a plating nucleus as a core of copper plating on the surface of the copper alloy foil A method for producing an alloy foil is provided.

  Moreover, the manufacturing method of the said negative electrode copper alloy foil for secondary batteries prepares the copper alloy foil which contains 0.01 wt% or more and 0.06 wt% or less of Zr in the copper alloy foil preparation process, The surface of the copper alloy foil may be electrolytically etched to form a plating nucleus made of Cu and Zr.

  Moreover, the manufacturing method of the said negative electrode copper alloy foil for secondary batteries may further comprise the copper layer formation process which forms a copper layer on a plating nucleus by copper-plating by using a plating nucleus as a nucleus.

  According to the negative electrode copper alloy foil for the secondary battery and the method for producing the negative electrode copper alloy foil for the secondary battery according to the present invention, the negative electrode copper alloy foil for the secondary battery excellent in adhesion to the active material, and the secondary battery The manufacturing method of the negative electrode copper alloy can be provided.

[Embodiment]
FIG.1 and FIG.2 shows the outline | summary of the cross section of the negative electrode copper alloy foil for secondary batteries which concerns on embodiment of this invention.

(Configuration of negative electrode copper alloy foil 1 for secondary battery)
A secondary battery negative electrode copper alloy foil 1 according to the present embodiment is a copper alloy foil used for a negative electrode of a lithium ion secondary battery. Referring to FIG. 1, the secondary battery negative electrode copper alloy foil 1 according to the present embodiment includes a copper alloy foil 10 and a plating nucleus 20 formed on the surface of the copper alloy foil 10. The plating nucleus 20 functions as a nucleus of the formed copper layer when a later-described copper layer is formed on the plating nucleus 20 by copper plating. Moreover, the copper alloy foil 10 is formed to have a strength capable of expanding and contracting according to the expansion and contraction in the planar direction of the active material layer provided on the negative electrode copper alloy foil 1 for a secondary battery.

(Copper alloy foil 10)
The purpose of the copper alloy foil 10 according to the present embodiment is to suppress the progress of softening of the copper alloy foil 10 by ensuring the heat resistance and heat history applied to the copper alloy foil 10 during the manufacture of the lithium ion secondary battery. It is formed including 0.01 wt% or more of Zr. Moreover, the copper alloy foil 10 contains 0.06 wt% or less of Zr for the purpose of providing practically sufficient heat resistance to the negative electrode copper alloy foil 1 for secondary batteries and realizing cost reduction. It is formed.

  As described above, the copper alloy foil 10 according to the present embodiment is formed to contain 0.01 wt% or more and less than 0.06 wt% of Zr based on the following knowledge obtained as a result of earnest research by the inventors. .

  That is, the lithium ion secondary battery is formed by including a current collector made of copper foil and an active material provided on the current collector. When the volume of the active material on the current collector expands during charging of the lithium ion secondary battery, the copper foil that is the current collector also expands following the volume expansion of the active material. Here, in a normal copper foil (electrolytic copper foil or tough pitch copper foil) that does not contain Zr, plastic deformation occurs by extending beyond the range of elastic deformation of the copper foil, so the discharge of the lithium ion secondary battery Sometimes, even if the volume of the active material is reduced, the copper foil does not shrink and remains in an elongated state. Thereby, peeling of the active material from the copper foil occurs. When the charge and discharge of the lithium ion secondary battery is repeated, the active material repeatedly expands and contracts, while the copper foil does not contract. Therefore, the active material peels from the copper foil more significantly.

  Here, if the current collector is formed of a high-strength copper foil (that is, a high-strength copper alloy foil), the proof stress of the current collector is greater than the stress generated by the volume expansion of the active material. It was found that the elongation of the current collector stays within the elastic deformation because it wins. That is, a current collector is formed by forming a current collector from a material that expands and contracts according to the volume change of the active material due to charge and discharge of the lithium ion secondary battery (a material that expands and contracts according to the expansion and contraction in the plane direction of the layered active material). The knowledge that peeling of the active material from the electric conductor can be suppressed was obtained. In addition, when the current collector is formed from a high-strength copper foil, it has been found that during charging, lithium ions cannot enter the vicinity of the current collector, and the volume expansion in the vicinity of the current collector can be suppressed small.

  Although the strength of the copper foil as the current collector can be increased by increasing the thickness of the copper foil, the ratio of the volume of the current collector to the entire negative electrode for the secondary battery is increased. The proportion of the active material in the entire secondary battery negative electrode is reduced. In this case, since the size of the secondary battery increases as the thickness of the copper foil increases, there is a limit to increasing the capacity of the secondary battery. Therefore, it is preferable that the thickness of the copper foil of the current collector is not increased more than necessary. Moreover, in the manufacturing process of a battery such as a lithium ion secondary battery, heat treatment at 150 ° C. to 300 ° C. may be performed on the copper foil. This heat treatment is a process performed in accordance with the battery manufacturing process such as removal of the solvent for the composite material, drying of the water, and formation of the Sn—Cu alloy as the active material. When a copper foil made of oxygen-free copper (OFC copper foil) or a copper foil made of tough pitch copper (TPC copper foil) is subjected to a heat treatment of about 130 ° C., the softening proceeds and the tensile strength is greatly reduced. That is, the OFC copper foil and the TPC copper foil are after the heat treatment after being manufactured as a secondary battery, even if the strength of the copper foil before the heat treatment is sufficient. Since the strength of the copper foil is lowered, it cannot be said to be preferable in the present embodiment.

  As described above, the present inventor can realize a high capacity of the lithium ion secondary battery, expands and contracts in accordance with the expansion and contraction in the planar direction of the active material layer, and can suppress a decrease in strength even when heat treatment is performed. The copper alloy foil 10 containing 0.01 wt% or more and 0.06 wt% or less of Zr has been found.

(Plating nucleus 20)
The plating nucleus 20 is a fine particle formed from Cu and Zr. The fine particles are formed with a diameter of several hundred nm or less. In FIG. 1, the plurality of plating nuclei 20 are formed on the copper alloy foil 10 at intervals, but the plurality of plating nuclei 20 are formed so as to cover the surface of the copper alloy foil 10, that is, without gaps. Accordingly, the layered plating nucleus 20 can be substantially formed.

(Outline of negative electrode copper alloy foil 1a for secondary battery)

  Referring to FIG. 2, the secondary battery negative electrode copper alloy foil 1a is formed by providing a copper layer 30 on the secondary battery negative electrode copper alloy foil 1 shown in FIG. The copper layer 30 is a roughened copper plating layer formed by copper plating (roughening copper plating) using the plating nucleus 20 as a nucleus. The roughened copper plating layer is formed, for example, by plating copper having a bump shape on each of the plurality of plating nuclei 20, and the surface is roughened. Here, when the plating nuclei 20 are scattered on the copper alloy foil 10, the plating nuclei 20 are formed so as to be distributed substantially uniformly on the copper alloy foil 10. Alternatively, the plating nucleus 20 is formed in layers on the copper alloy foil 10. Therefore, the copper layer 30 formed by copper plating using the plating nucleus 20 as a nucleus is formed on the plating nucleus 20 without including a plating defect that is a portion where plating is not performed. Therefore, the copper layer 30 is formed to have a substantially uniform roughened shape over the entire surface.

(Outline of negative electrode 2 for secondary battery)
FIG. 3: shows the outline | summary of the cross section of the negative electrode for secondary batteries which concerns on embodiment of this invention.

  The secondary battery negative electrode 2 is formed by providing an active material layer 40 on the secondary battery negative electrode copper alloy foil 1a shown in FIG. For example, the active material layer 40 is formed on the copper layer 30 by NiSn alloy plating. In the present embodiment, active material layer 40 is formed on copper layer 30 which is a roughened copper plating layer having a rough surface. Since the surface of the copper layer 30 is a roughened surface, the “anchor effect” in which the irregularities on the surface of the copper layer 40 bite into the active material layer 40 is exhibited.

  Here, the copper layer 30 exhibits an anchor effect on the active material layer 40 to ensure adhesion between the copper layer 30 and the active material layer 40. Rz ”or“ Rz ”) is formed with a roughened surface of 1 μm or more. Further, the copper layer 30 is a roughened surface having a surface roughness Rz of less than 5 μm for the purpose of suppressing the drop-off of the copper layer 30 and suppressing a decrease in adhesion between the copper layer 30 and the active material layer 40. Formed.

  In addition, the presence or absence of the plating nucleus 20 which is microparticles | fine-particles which consist of Cu and Zr can be confirmed as follows. First, the negative electrode copper alloy foil 1a for secondary batteries after roughening copper plating, the negative electrode 2 for secondary electrodes obtained after forming the active material layer 40, or the negative electrode 2 for secondary batteries which concerns on this Embodiment is provided. The cross section of the secondary battery negative electrode 2 taken out from the lithium secondary battery is formed by a focused ion beam (FIB), ion milling, or a microtome. Next, the interface between the copper alloy foil 10 and the copper layer 30 is observed with an SEM. And the presence or absence of the plating nucleus 20 can be confirmed from the SEM image obtained by SEM observation.

Whether or not the copper alloy foil 10 is plastically deformed during charging / discharging of the lithium ion secondary battery using the secondary battery negative electrode 2 depends on the maximum tensile strength of the copper alloy foil 10 and the thickness of the copper alloy foil 10. Can be defined by product. For example, when using the active material layer 40 mainly composed of Sn or Si, the maximum tensile strength of the copper alloy foil 10 and the thickness of the copper alloy foil 10 are set for the purpose of suppressing plastic deformation of the copper alloy foil 10. The product is preferably 3600 N / mm ² · μm or more.

(Negative copper alloy foil for secondary battery and method for producing secondary battery negative electrode)
FIG. 4 shows a flow of manufacturing steps of the secondary battery negative electrode copper alloy foil and the secondary battery negative electrode according to the embodiment of the present invention.

  First, a copper alloy foil 10, which is a high-strength copper alloy foil containing Zr, is prepared (copper alloy foil preparation step: step 100, hereinafter, “step” is referred to as “S”). Next, the copper alloy foil 10 is subjected to cathode electrolytic degreasing in an alkaline solution (degreasing step: S110). Thereby, the surface of the copper alloy foil 10 is cleaned. Subsequently, the copper alloy foil 10 having a cleaned surface is subjected to anodic electrolytic pickling. That is, electrolytic etching is performed on the surface of the copper alloy foil 10 by supplying power to the copper alloy foil 10 using the copper alloy foil 10 as an anode. Thereby, the fine particles composed of Cu and Zr constituting the copper alloy foil 10 are formed to be exposed on the surface of the copper alloy foil 10, and the negative electrode copper alloy foil 1 for the secondary battery according to the present embodiment is manufactured. (Plating nucleus forming step: S120). The fine particles become the plating nucleus 20. In addition, since the copper alloy foil 10 is anodic electrolytic pickling, the clean surface of the copper alloy is exposed to the outside by etching the surface of the copper alloy foil 10.

  Subsequently, a copper layer 30 is formed on the surface of the copper alloy foil 10 on which the plating nucleus 20 is formed by electrolytic copper plating (roughening copper plating) (copper layer forming step: S130). Thereby, the negative electrode copper alloy foil 1a for secondary batteries which concerns on this Embodiment is manufactured. In this case, the copper layer 30 is formed by plating copper on the core using the plating core 20 as a core. For example, the copper layer 30 having a rough surface is formed by performing plating over the plating nucleus 20 and forming the copper layer 30 having a bump shape with the plating nucleus 20 as a nucleus. Moreover, copper plating can also be implemented in several steps.

  In addition, when a part of microparticles | fine-particles which consist of Cu and Zr are inevitably dropped from the surface of the copper alloy foil 10 while performing the electrolytic etching on the surface of the copper alloy foil 10, or ultrasonic waves are applied to the copper alloy foil. Even when a part of the fine particles are intentionally removed by being applied to the surface of the copper alloy 10, as long as the fine particles, that is, the plating nucleus 20 exists on the surface of the copper alloy foil 10, the plating defect is substantially eliminated. A non-existing copper layer 30 can be formed.

  Next, the active material layer 40 is formed on the copper layer 30 (active material layer forming step: S140). For example, the active material layer 40 made of a NiSn alloy is formed by performing NiSn alloy plating on the copper layer 30. Thereby, the negative electrode 2 for secondary batteries which concerns on this Embodiment is manufactured.

(Effect of embodiment)
Since the negative electrode copper alloy foil 1 for a secondary battery according to the present embodiment forms a current collector from a high strength copper alloy foil 10 containing a predetermined concentration of Zr, the negative electrode copper alloy foil 1 for a secondary battery is Even when charging and discharging are repeated in the used lithium ion secondary battery, the copper alloy foil 10 can be expanded and contracted in accordance with the expansion and contraction of the active material layer 40. Thereby, even if the negative electrode copper alloy foil 1 for secondary batteries is repeatedly charged and discharged, peeling of the active material layer 40 from the copper alloy foil 10 can be reduced.

  Moreover, the negative electrode copper alloy foil 1 for secondary batteries which concerns on this Embodiment provides the plating nucleus 20 on the surface of the copper alloy foil 10 which is a collector, and carries out copper plating on the plating nucleus 20, and thereby a plating defect Since the copper layer 30 having a substantially uniform surface is formed, the adhesion strength between the copper alloy foil 10 and the active material layer 40 can be improved by the anchor effect. Thereby, in this Embodiment, compared with the negative electrode for secondary batteries using a carbon type active material, energy density is high, and the active material as an active material for negative electrodes from the copper alloy foil 10 which is a collector Even if the layer 40 is repeatedly charged and discharged, the layer 40 is not peeled off or dropped off, so that the secondary battery negative electrode 2 for a lithium ion secondary battery having excellent cycle characteristics can be provided.

(Manufacture of negative electrode for secondary battery)
The negative electrode for secondary batteries which concerns on an Example (Examples 1-3) was manufactured. Specifically, an 18 μm thick Zr-containing high-strength copper foil (manufactured by Hitachi Cable Ltd., HCL02Z foil) was prepared as a copper alloy foil 10. The Zr composition of HCL02Z was 0.02 wt%. Subsequently, cathodic electrolytic degreasing of the surface of the copper alloy foil 10 was performed. Next, after the surface of the copper alloy foil 10 was subjected to anodic electrolytic pickling, roughened copper plating 1 and roughened copper plating 2 were performed. Further, an active material layer was formed by NiSn alloy plating. This produced the secondary battery negative electrode which concerns on an Example. Here, each condition of cathodic electrolytic degreasing, anodic electrolytic pickling, copper roughening plating 1, copper roughening plating 2, and NiSn alloy plating is as shown in Table 1.

The difference between the negative electrodes for secondary batteries according to Examples 1 to 3 is the conditions for anodic electrolytic pickling. That is, in the negative electrode for a secondary battery according to Example 1, the conditions of anodic electrolytic pickling were set to a current density of 20 A / dm ² and the anodic electrolytic pickling time was set to 5 seconds. The negative electrode for a secondary battery according to Example 2 was set to the same conditions as in Example 1 except that the time for anodic electrolytic pickling was set to 30 seconds. Thereby, in the negative electrode for secondary batteries which concerns on Example 2, 6 times as many microparticles | fine-particles which consist of Cu and Zr on the surface of the copper alloy foil 10 were formed compared with the case of Example 1. FIG. However, in Example 2, some of the fine particles dropped off naturally.

  The negative electrode for a secondary battery according to Example 3 is similar to Example 2, in which fine particles composed of Cu and Zr are formed on the surface of the copper alloy foil 10, and then ultrasonic waves are applied to the copper alloy foil 10 on which the fine particles are formed. The conditions were the same as in Example 2 except that the surface was irradiated. In Example 3, some of the fine particles were removed from the surface of the copper alloy foil 10 by irradiation with ultrasonic waves. When the surface of the copper alloy foil 10 after ultrasonic irradiation was observed, the surface was light brown. Therefore, in Example 3, it was confirmed that fine particles composed of Cu and Zr remained on the surface of the copper alloy foil 10 even after the ultrasonic wave irradiation.

  In addition, as a comparative example, instead of anodic electrolytic pickling, a negative electrode for a secondary battery according to a comparative example was manufactured in place of the condition of immersing in sulfuric acid for 30 seconds without performing electrolysis. In the comparative example, the surface of the copper alloy foil 10 exhibited a copper color even after immersion, and it was confirmed that a fine particle layer composed of Cu and Zr was not formed. Moreover, in Examples 1-3 and a comparative example, the volume expansion coefficient is normal secondary by forming the thickness of NiSn alloy plating thinner than the thickness of the active material layer used for a normal secondary battery. The active material layer was relatively small with respect to the active material layer used in the battery.

  Here, the surface of the negative electrode copper alloy foil for secondary batteries after roughening copper plating 1 and roughening copper plating 2 was observed with SEM.

  Fig.5 (a) is a SEM photograph of the negative electrode copper alloy foil for secondary batteries which concerns on an Example, (b) is a SEM photograph of the negative electrode copper alloy foil for secondary batteries which concerns on a comparative example.

  Specifically, FIG. 5 (a) shows the surface before the NiSn alloy plating after the roughened copper plating 1 and the roughened copper plating 2 in the manufacturing process of the negative electrode for secondary battery according to Example 1. It is the result of having observed (namely, the surface of the negative electrode copper alloy foil for secondary batteries) by SEM. FIG. 5 (b) shows the surface before applying NiSn alloy plating after the roughened copper plating 1 and the roughened copper plating 2 in the manufacturing process of the negative electrode for secondary battery according to the comparative example (that is, It is the result of having observed SEM of the surface of the negative electrode copper alloy foil for secondary batteries.

  Referring to FIG. 5 (a), the surface of the secondary battery negative electrode copper alloy foil is roughened substantially uniformly. That is, in the negative electrode copper alloy foil for secondary battery according to Example 1, it was observed that the protrusions of about a dozen μm were formed substantially uniformly on the surface of the copper alloy foil. On the other hand, referring to FIG. 5 (b), it was observed that many plating defects not plated with copper exist in the region surrounded by a circle in FIG. 5 (b). In addition, although the surface was also observed by SEM about the negative electrode copper alloy foil for secondary batteries which concerns on Example 2 and 3, like Example 1, it was confirmed that the plating defect has not generate | occur | produced.

  FIG. 6 is a cross-sectional BSE photograph of a negative electrode copper alloy foil for a secondary battery according to an example.

  Specifically, FIG. 6 is a backscattered electron (BSE) image of the negative electrode copper alloy foil for a secondary battery according to Example 1. The observation method is as follows. That is, about the negative electrode copper alloy foil for secondary batteries which concerns on Example 1, the cross section was formed using the Hitachi Ltd. Ar ion milling apparatus E3500. Then, the cross section formed with the YAG backscattered electron detector with which Hitachi SEM SU-70 was mounted was observed.

  As can be seen with reference to FIG. 6, fine particles 22 were observed in the region surrounded by a circle. The fine particles were fine particles having a diameter of 300 nm or less. In addition, when the surface of the copper alloy foil 10 after anodic electrolytic pickling was measured by Energy Dispersive X-ray Spectroscopy (EDX), Cu and Zr were detected. It is thought that it is formed.

(Charge / discharge test)
Each of the negative electrodes for secondary batteries according to Examples 1 to 3 and the comparative example was punched into a 2 cm ² circle, and each was a test cell having metallic lithium as a counter electrode (test cells 1 to 3 according to the example and comparative example) The test cell) was manufactured and the charge / discharge characteristics were evaluated. The measuring cell is an HS cell manufactured by Hosen Co., Ltd., the measuring device is HJ1001SM8A manufactured by Hokuto Denko Co., Ltd., the separator is # 2400 manufactured by Celgard Co., Ltd., and the electrolyte is LIPASTER-EDMC / manufactured by Toyama Pharmaceutical Co., Ltd. PF1 (a mixed solution of ethylene carbonate and diethyl carbonate (1: 1 vol.) In which 1 mol / L LiPF ₆ was dissolved) was used. This is because a lithium ion secondary battery is an aprotic solvent and requires the use of an electrolytic solution having a high dielectric constant and low viscosity. Therefore, the electrolytic solution is a high dielectric constant and high viscosity solvent (for example, a cyclic ester such as ethylene carbonate) and a low dielectric constant and low viscosity solvent (for example, a chain shape such as diethyl carbonate). It is preferable to use a mixed solution with an ester. Charging / discharging was performed at a constant current density of 0.25 mA / cm ^{2 in} the range of 0.01 to 1 V vs Li / Li ⁺ . The evaluation results are shown in Table 2.

  Referring to Table 2, in test cells 1 to 3 according to the example, the capacity retention rate after 20 cycles was 80% or more. On the other hand, in the test cell according to the comparative example, the capacity retention rate after 20 cycles was 55%. In the charge / discharge test, when the capacity retention rate was 70% or more, the determination was “good”, and when the capacity retention rate was less than 70%, the determination was “failed”. In all of the test cells 1 to 3 according to the example, the determination was “◯”, and it was revealed that the charge / discharge characteristics were improved in the test cells 1 to 3 according to the example.

(About the product of maximum tensile strength and thickness of copper alloy foil)
Zr-containing high-strength copper foil (HCL02Z foil manufactured by Hitachi Cable Ltd.) having a thickness of 8 μm, 12 μm, and 18 μm, and tough pitch copper (TPC) foil were prepared. The TPC foil was heated at 180 ° C. for 12 hours to simulate the heat applied to the TPC foil in the manufacturing process of the lithium ion secondary battery. The maximum tensile strength of the TPC foil after the heat treatment was 150 N / mm ² . In the HCL02Z foil, the physical properties are not changed by the heat treatment at this temperature and time.

  Subsequently, the HCL02Z foil having a thickness of 8 μm, 12 μm, and 18 μm was processed under the same conditions as those of Example 1 shown in Table 1 to produce secondary battery negative electrodes (Examples 4 to 6). Moreover, the negative electrode for secondary batteries was manufactured by performing the process of the same conditions as the conditions of Example 1 shown in Table 1 on the tough pitch copper (TPC) foil having thicknesses of 8 μm, 12 μm, and 18 μm, respectively (Comparative Examples 2 to 2). 4). Then, the charge / discharge test was implemented similarly to the said "charge / discharge test" about the negative electrode for secondary batteries which concerns on each of Examples 4-6 and Comparative Examples 2-4. Table 3 shows the results of the charge / discharge test for the negative electrodes for secondary batteries according to Examples 4 to 6 and Comparative Examples 2 to 4.

Referring to Table 3, each of the negative electrodes for secondary batteries according to Examples 4 to 6 uses a material containing Zr for the copper alloy foil, and the thickness of the copper alloy foil and the maximum tensile strength of the copper alloy foil. The product value is 3600 N / mm ² μm or more. And the determination of the charging / discharging test was "(circle)" about all the negative electrodes for secondary batteries which concern on Examples 4-6. On the other hand, about the negative electrode for secondary batteries which concerns on each of Comparative Examples 2-4, determination of the charging / discharging test was "x". Therefore, by using a material containing Zr for the copper alloy foil and using a material in which the product of the thickness of the copper alloy foil and the maximum tensile strength of the copper alloy foil is 3600 N / mm ² · μm or more, It was shown that a negative electrode for a secondary battery having a sufficient capacity retention rate can be provided.

(About anodic electrolytic pickling and roughened copper plating 2)
Using an 18 μm-thick Zr-containing high-strength copper foil (HCL02Z foil manufactured by Hitachi Cable Ltd.), in the same manner as in Example 1, cathodic electrolytic degreasing, anodic electrolytic pickling, roughened copper plating 1, and roughened copper plating 2 Then, a negative electrode for a secondary battery in which an active material layer was formed by NiSn alloy plating was produced (Examples 7 to 12). In the production of the negative electrode for secondary battery according to Examples 7 to 12, the time for anodic electrolytic pickling and the conditions of roughened copper plating 2 were changed with respect to Example 1. Moreover, the negative electrode for secondary batteries which concerns on Comparative Examples 5-7 was manufactured as a comparative example. Table 4 shows the anodic electrolytic pickling and roughening copper plating 2 conditions of the negative electrodes for secondary batteries according to Examples 7 to 12 and Comparative Examples 5 to 7, and the determination results of the charge / discharge test. In addition, about the charging / discharging test, the method demonstrated in said "(charging / discharging test)" was employ | adopted and implemented.

  Referring to Table 4, when the surface roughness Rz of the copper layer formed by the roughened copper plating 2 is less than 1 μm, the discharge capacity retention rate is as low as 65% (Comparative Example 5), and the surface roughness Rz is 1 μm or more and 5 μm. In the case of less than 80%, the discharge capacity retention rate was 80% or more (Examples 7 to 12). Further, when the surface roughness Rz of the copper layer formed by the roughened copper plating 2 was 5 μm or more, the copper layer formed by plating on the copper alloy foil 10 dropped off. Therefore, it was shown that the surface roughness Rz of the copper layer is preferably 1 μm or more and less than 5 μm.

  In Comparative Example 7 in which the anodic electrolytic pickling was replaced with chemical polishing, the dissolution amount of the copper alloy foil 10 was as small as 0.01 μm, and formation of fine particles composed of Cu and Zr on the surface of the copper alloy foil 10 Was not recognized. Therefore, in Comparative Example 7, plating defects occurred on the surface of the roughened copper plating formed on the surface of the copper alloy foil 10. Due to this plating defect, in Comparative Example 7, the charge / discharge characteristics were not good. When the amount of dissolution of the surface of the copper alloy foil 10 by anodic electrolytic pickling is 0.1 μm or more (Examples 7 to 12), the charge / discharge characteristics are such that the surface of the copper alloy foil 10 is dissolved as in Comparative Example 7. It was shown that it is greatly improved compared with the case of few.

  While the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

It is a schematic diagram of the cross section of the negative electrode copper alloy foil for secondary batteries which concerns on embodiment of this invention. It is a schematic diagram of the cross section of the negative electrode copper alloy foil for secondary batteries which concerns on embodiment of this invention. It is a schematic diagram of the cross section of the negative electrode for secondary batteries which concerns on embodiment of this invention. It is a figure which shows the flow of the manufacturing process of the negative electrode copper alloy foil for secondary batteries which concerns on embodiment of this invention, and the negative electrode for secondary batteries. (A) is a figure of the SEM photograph of the negative electrode copper alloy foil for secondary batteries which concerns on an Example, (b) is a figure of the SEM photograph of the negative electrode copper alloy foil for secondary batteries which concerns on a comparative example. It is a figure of the cross-section BSE photograph of the negative electrode copper alloy foil for secondary batteries which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Negative electrode copper alloy foil for secondary batteries 2 Negative electrode for secondary batteries 10 Copper alloy foil 20 Plating nucleus 22 Fine particle 30 Copper layer 40 Active material layer

Claims (8)

A negative electrode copper alloy foil for a secondary battery that functions as a negative electrode for a secondary battery by providing an active material layer,
A copper alloy foil that expands and contracts in accordance with the expansion and contraction of the active material layer in the plane direction;
A negative electrode copper alloy foil for a secondary battery, which is formed on a surface of the copper alloy foil and includes a plating nucleus serving as a nucleus of copper plating. The copper alloy foil includes 0.01 wt% or more and 0.06 wt% or less of Zr,
The negative electrode copper alloy foil for a secondary battery according to claim 1, wherein the plating nucleus is made of Cu and Zr. 3. The negative electrode copper alloy foil for a secondary battery according to claim 2, wherein the copper alloy foil has a product of a maximum tensile strength of the copper alloy foil and a thickness of the copper alloy foil of 3600 N / mm ² · μm or more.   The negative electrode copper alloy foil for secondary batteries according to claim 3, further comprising a copper layer formed on the plating nucleus by copper plating using the plating nucleus as a nucleus and having a surface roughness of 1 μm or more and less than 5 μm.   The negative electrode copper alloy foil for a secondary battery according to claim 4, wherein the plating nucleus is formed in a layered manner on the surface of the copper alloy foil. A method for producing a negative electrode copper alloy foil for a secondary battery that functions as a negative electrode for a secondary battery by providing an active material layer,
A copper alloy foil preparation step of preparing a copper alloy foil that expands and contracts in accordance with the expansion and contraction of the active material layer in the plane direction;
The manufacturing method of the negative electrode copper alloy foil for secondary batteries provided with the plating nucleus formation process which forms the plating nucleus used as the nucleus of copper plating on the surface of the said copper alloy foil. In the copper alloy foil preparation step, the copper alloy foil containing 0.01 wt% or more and 0.06 wt% or less of Zr is prepared,
The said plating nucleus formation process is a manufacturing method of the negative electrode copper alloy foil for secondary batteries of Claim 6 which electrolytically etches the surface of the said copper alloy foil and forms the said plating nucleus which consists of Cu and Zr.   The manufacturing method of the negative electrode copper alloy foil for secondary batteries of Claim 7 further equipped with the copper layer formation process which forms a copper layer on the said plating nucleus by copper plating using the said plating nucleus as a nucleus.