US-12620599-B2 - Layered body, negative electrode current collector for lithium ion secondary battery, and negative electrode for lithium ion secondary battery

Abstract

A laminated body contains a first metal layer containing copper; and a second metal layer containing nickel and laminated directly on the first metal layer. A first surface of the second metal layer is a surface in contact with the first metal layer. A second surface of the second metal layer is a reverse face of the first surface. A thickness direction of the second metal layer is a direction approximately perpendicular to the first surface and oriented from the first surface toward the second surface. A unit of a content of nickel in the second metal layer is % by mass. The content of nickel in the second metal layer 2 decreases along the thickness direction D.

Inventors

• Yuhei HORIKAWA
• Makoto Endo
• Takuya KAKIUCHI
• Miyuki Yanagida
• Yuki Naito
• Takahiro Tashiro

Assignees

• TDK CORPORATION

Dates

Publication Date

20260505

Application Date

20211216

Priority Date

20210120

Claims (9)

1. 1 . A laminated body comprising: a first metal layer containing copper; and a second metal layer containing nickel and laminated directly on the first metal layer, wherein a first surface of the second metal layer is a surface in contact with the first metal layer, a second surface of the second metal layer is a reverse face of the first surface, a thickness direction of the second metal layer is a direction approximately perpendicular to the first surface and oriented from the first surface toward the second surface, a unit of a content of nickel in the second metal layer is % by mass, and the content of nickel in the second metal layer decreases along the thickness direction.
2. 2 . The laminated body according to claim 1 , wherein the second metal layer further contains at least one element selected from the group consisting of phosphorus and tungsten.
3. 3 . The laminated body according to claim 1 , wherein the second metal layer consists of a plurality of nickel-containing layers laminated in the thickness direction, and a content of nickel in each of the plurality of nickel-containing layers is different from each other.
4. 4 . The laminated body according to claim 1 , wherein a thickness of the first metal layer is represented by T 1 , a thickness of the second metal layer is represented by T 2 , and T 2 /T 1 is 0.6 or more and 1.0 or less.
5. 5 . The laminated body according to claim 1 , wherein the content of nickel in the second metal layer is the highest in the vicinity of the first surface, decreases stepwise along the thickness direction, and is the lowest in the vicinity of the second surface.
6. 6 . The laminated body according to claim 1 , wherein the content of nickel in the second metal layer is the highest in the vicinity of the first surface, decreases continuously along the thickness direction, and is the lowest in the vicinity of the second surface.
7. 7 . A negative electrode current collector for a lithium ion secondary battery, the negative electrode current collector comprising the laminated body according to claim 1 .
8. 8 . A negative electrode for a lithium ion secondary battery, the negative electrode comprising: the negative electrode current collector according to claim 7 ; and a negative electrode active material layer containing a negative electrode active material, wherein the negative electrode active material layer is laminated directly on the second surface of the second metal layer.
9. 9 . The negative electrode according to claim 8 , wherein the negative electrode active material contains silicon.

Description

TECHNICAL FIELD The present disclosure relates to a laminated body, a negative electrode current collector for a lithium ion secondary battery, and a negative electrode for a lithium ion secondary battery. BACKGROUND ART A negative electrode current collector for a lithium ion secondary battery is subjected to repeated loads (compressive stress and tensile stress), due to fluctuating of the volume of the negative electrode active material layer laminated on the negative electrode current collector associated with charging and discharging. Deformation of the negative electrode current collector attributed to these loads causes deformation of the battery main body or short-circuiting between electrodes. Therefore, the negative electrode current collector is required to have durability against the loads. For example, the following Patent Literature 1 discloses, as a negative electrode current collector having tensile strength, a negative electrode current collector in which an electrode foil containing copper and a hard nickel plating layer are laminated. The following Patent Literature 2 discloses, as a current collector having sufficient strength for suppressing cracking and tearing, a current collector in which a first metal layer consisting of copper and a second metal layer consisting of nickel or a nickel alloy are laminated. CITATION LIST Patent Literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2005-197205 Patent Literature 2: Japanese Unexamined Patent Publication No. 2019-186134 SUMMARY OF INVENTION Technical Problem As in the case of the above-mentioned conventional negative electrode current collectors, when a laminated body has a first metal layer that contains copper and a second metal layer that contains nickel and is laminated directly on the first metal layer, as the laminated body is repeatedly subjected to stress, the second metal layer is likely to be peeled from the first metal layer. The inventors found that peeling of the second metal layer from the first metal layer is attributed to the difference in hardness (elastic modulus) between the first metal layer and the second metal layer. For example, the Young's modulus of the second metal layer containing nickel tends to be higher than the Young's modulus of the first metal layer containing copper. That is, the second metal layer containing nickel is hard compared with the first metal layer containing copper and is less likely to be deformed due to stress. Furthermore, the elastic modulus of the second metal layer tends to increase with an increase in contents of additive elements other than nickel in the second metal layer, and the second metal layer tends to become hard. An object of one aspect of the present invention is to provide a laminated body having a first metal layer containing copper and a second metal layer containing nickel, in which peeling of the second metal layer from the first metal layer is suppressed, a negative electrode current collector and a negative electrode for a lithium ion secondary battery, both of which contain the laminated body. Solution to Problem A laminated body according to one aspect of the present invention contains a first metal layer containing copper and a second metal layer containing nickel and laminated directly on the first metal layer, a first surface of the second metal layer is a surface in contact with the first metal layer, a second surface of the second metal layer is a reverse face of the first surface, a thickness direction of the second metal layer is a direction approximately perpendicular to the first surface and oriented from the first surface toward the second surface, a unit of a content of nickel in the second metal layer is % by mass, and the content of nickel in the second metal layer decreases along the thickness direction. The second metal layer may further contain at least one element selected from the group consisting of phosphorus and tungsten. The second metal layer may consist of a plurality of nickel-containing layers laminated in the thickness direction, and a content of nickel in each of the plurality of nickel-containing layers may be different from each other. A thickness of the first metal layer is represented by T1, a thickness of the second metal layer is represented by T2, and T2/T1 may be 0.6 or more and 1.0 or less. The content of nickel in the second metal layer may be the highest in the vicinity of the first surface, may decrease stepwise along the thickness direction, and may be the lowest in the vicinity of the second surface. The content of nickel in the second metal layer may be the highest in the vicinity of the first surface, may decrease continuously along the thickness direction, and may be the lowest in the vicinity of the second surface. A negative electrode current collector for a lithium ion secondary battery according to one aspect of the present invention contains the above-described laminated body. A negative electrode