Anode current collector for all-solid-state batteries comprising a multilayer protective film, and all-solid-state battery comprising the same

Abstract

A negative electrode current collector for an all-solid-state battery and an all-solid-state battery including the same are proposed, which include a multilayer protective film capable of preventing chemical and mechanical degradation of a copper current collector occurring in a sulfide-based solid electrolyte environment, thereby extending the lifespan of the all-solid-state battery and ensuring interfacial stability. The negative electrode current collector for an all-solid-state battery including the multilayer protective film comprises, on a copper substrate, a first nickel-phosphorus alloy layer having a phosphorus content smaller than that of a second nickel-phosphorus alloy layer; on the first nickel-phosphorus alloy layer, a second nickel-phosphorus alloy layer having a phosphorus content larger than that of the first nickel-phosphorus alloy layer; on the second nickel-phosphorus alloy layer, a third nickel-phosphorus alloy layer having a phosphorus content smaller than that of the second nickel-phosphorus alloy layer; and on the third nickel-phosphorus alloy layer, a fourth nickel-phosphorus alloy layer having a phosphorus content larger than that of the third nickel-phosphorus alloy layer.

Description

Technology Field

[0001] The present invention relates to a negative electrode current collector for an all-solid-state battery comprising a multilayer protective film and an all-solid-state battery comprising the same. More specifically, the invention relates to a negative electrode current collector for an all-solid-state battery comprising a multilayer protective film capable of preventing chemical and mechanical degradation of a copper current collector occurring in a sulfide-based solid electrolyte environment, thereby extending the lifespan of the all-solid-state battery and ensuring interface stability, and an all-solid-state battery comprising the same. Background Technology

[0003] Lithium-ion batteries have long been used as the core power source for electric vehicles and energy storage systems (ESS). However, due to the structural characteristics of liquid electrolytes, they pose risks of thermal runaway and fire. To address these issues, all-solid-state batteries (ASSBs) utilizing sulfide-based solid electrolytes are attracting attention as next-generation energy storage systems. Sulfide-based electrolytes are considered the material with the highest potential for commercialization, as they offer high ionic conductivity and excellent mechanical ductility.

[0004] In conventional lithium-ion batteries, copper (Cu) thin films have been widely used as negative electrode current collectors. In liquid electrolyte environments, copper was considered a chemically stable, inert substrate. However, in all-solid-state battery environments, when copper comes into direct contact with sulfide-based electrolytes, it undergoes spontaneous chemical and electrochemical corrosion reactions to form insulating layers such as copper sulfide (Cu2S). This leads to a rapid increase in interfacial resistance and causes problems such as shortened battery life.

[0005] To address this, techniques have been proposed to coat the copper surface with a nickel (Ni) or nickel-phosphorus (Ni-P) alloy layer or to use a stainless steel (STS) thin film. However, these conventional techniques exhibit problems such as low electrical conductivity causing ohmic loss or the coating film easily peeling off under high pressure of approximately 50 MPa. Additionally, they have limitations in effectively blocking crevice corrosion occurring on the sides during electrode cutting.

[0006] Therefore, for the commercialization of all-solid-state batteries, new protection structures and manufacturing technologies capable of fundamentally preventing chemical and mechanical degradation of copper current collectors are required. The problem to be solved

[0008] The present invention has been devised to solve the above-mentioned problems, and the objective of the present invention is to provide a negative electrode current collector for an all-solid-state battery comprising a multilayer protective film capable of preventing chemical and mechanical degradation of the copper current collector occurring in a sulfide-based solid electrolyte environment, thereby extending the lifespan of the all-solid-state battery and ensuring interface stability, and an all-solid-state battery comprising the same. means of solving the problem

[0010] A negative electrode current collector for an all-solid-state battery comprising a multilayer protective film according to one embodiment of the present invention for achieving the above objective comprises, on a copper substrate, a first nickel-phosphorus alloy layer having a phosphorus content smaller than that of a second nickel-phosphorus alloy layer; on the first nickel-phosphorus alloy layer, a second nickel-phosphorus alloy layer having a phosphorus content larger than that of the first nickel-phosphorus alloy layer; on the second nickel-phosphorus alloy layer, a third nickel-phosphorus alloy layer having a phosphorus content smaller than that of the second nickel-phosphorus alloy layer; and on the third nickel-phosphorus alloy layer, a fourth nickel-phosphorus alloy layer having a phosphorus content larger than that of the third nickel-phosphorus alloy layer.

[0011] The first nickel-phosphorus alloy layer and the third nickel-phosphorus alloy layer may have a phosphorus content of 1 to 4 wt%.

[0012] The first nickel-phosphorus alloy layer and the third nickel-phosphorus alloy layer may be crystalline alloys.

[0013] The second nickel-phosphorus alloy layer and the fourth nickel-phosphorus alloy layer may have a phosphorus content of 10 to 15 wt%.

[0014] The second nickel-phosphorus alloy layer and the fourth nickel-phosphorus alloy layer may be amorphous alloys.

[0015] The ratio of the thicknesses of the first nickel-phosphorus alloy layer, the second nickel-phosphorus alloy layer, the third nickel-phosphorus alloy layer, and the fourth nickel-phosphorus alloy layer may be 1.5 : 2 : 1.5 : 5.

[0016] The thicknesses of the first nickel-phosphorus alloy layer, the second nickel-phosphorus alloy layer, the third nickel-phosphorus alloy layer, and the fourth nickel-phosphorus alloy layer may be 150 nm, 200 nm, 150 nm, and 500 nm, respectively.

[0017] The total thickness can be 1.0 μm.

[0018] The laminate can be sealed by forming a plating layer on the side.

[0019] According to another aspect of the present invention, an all-solid-state battery is provided comprising a negative current collector for an all-solid-state battery, wherein the first nickel-phosphorus alloy layer having a phosphorus content smaller than that of a second nickel-phosphorus alloy layer is stacked on a copper substrate; a second nickel-phosphorus alloy layer having a phosphorus content larger than that of the first nickel-phosphorus alloy layer is stacked on the first nickel-phosphorus alloy layer; a third nickel-phosphorus alloy layer having a phosphorus content smaller than that of the second nickel-phosphorus alloy layer is stacked on the second nickel-phosphorus alloy layer; and a fourth nickel-phosphorus alloy layer having a phosphorus content larger than that of the third nickel-phosphorus alloy layer is stacked on the third nickel-phosphorus alloy layer. Effects of the invention

[0021] According to the present invention, by implementing a multilayer structure in which crystalline and amorphous alloy layers are alternately stacked on the surface of a copper negative current collector and an in-situ encapsulation technology, excellent electrical conductivity and interfacial stability are provided in a normal operating environment, and mechanical and chemical deterioration can be suppressed in a high temperature and high pressure environment through the shock absorption and diffusion blocking effects of each layer.

[0022] In addition, the multilayer nano-stacked current collector according to the present invention can secure long-term operating stability of more than 2,000 cycles while maintaining a total thickness of 1.0 μm or less, and can control the increase rate of interfacial resistance to within 4.2% of the initial value, thereby having the effect of significantly improving the lifespan and reliability of the all-solid-state battery.

[0023] In addition, the present invention can replace expensive alloys or rare metal coatings by utilizing only general-purpose copper foil and plating processes, thereby drastically reducing manufacturing costs, and can fundamentally prevent gap corrosion through an encapsulation structure that perfectly seals even the side cut surfaces, thus having the effect of accelerating the commercialization of all-solid-state batteries.

[0024] Therefore, the present invention has the effect of simultaneously ensuring safety and economic efficiency in various application fields, such as next-generation electric vehicles, energy storage devices, and highly integrated power modules. Brief explanation of the drawing

[0026] FIG. 1 is a cross-sectional view of a negative electrode current collector for an all-solid-state battery according to an embodiment of the present invention. Figure 2 is a graph showing the change in phosphorus content according to current density in nickel-phosphorus plating on a copper substrate, and Figure 3 is EDXS measured data of the low-phosphorus alloy layer and the high-phosphorus alloy layer. FIG. 4 is a drawing provided to explain a method for manufacturing a negative electrode current collector for an all-solid-state battery according to another embodiment of the present invention. FIG. 5 is a drawing provided to explain a method for manufacturing a negative electrode current collector for an all-solid-state battery according to another embodiment of the present invention. Specific details for implementing the invention

[0027] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. However, embodiments of the present invention may be modified in various different forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Although there may be components in the attached drawings that are depicted to have a specific pattern or have a predetermined thickness, this is for convenience of explanation or distinction, and therefore, even if a specific pattern and a predetermined thickness are depicted, the present invention is not limited only to the features of the depicted components.

[0028] FIG. 1 is a cross-sectional view of a negative electrode current collector for an all-solid-state battery according to an embodiment of the present invention. A negative electrode current collector (100) for an all-solid-state battery including a multilayer protective film according to the present invention has a copper substrate (110) on which a first nickel-phosphorus alloy layer (120) has a phosphorus content smaller than that of a second nickel-phosphorus alloy layer (130); on the first nickel-phosphorus alloy layer (120), a second nickel-phosphorus alloy layer (130) has a phosphorus content larger than that of the first nickel-phosphorus alloy layer (120); on the second nickel-phosphorus alloy layer (130), a third nickel-phosphorus alloy layer (140) has a phosphorus content smaller than that of the second nickel-phosphorus alloy layer (130); and on the third nickel-phosphorus alloy layer (140), a fourth nickel-phosphorus alloy layer (150) has a phosphorus content larger than that of the third nickel-phosphorus alloy layer (140).

[0029] The negative electrode current collector (100) for an all-solid-state battery according to the present invention is a negative electrode current collector based on copper among negative electrode current collectors used in an all-solid-state battery, and includes a nickel-phosphorus alloy layer to prevent corrosion when the copper substrate (110) comes into contact with a sulfide-based electrolyte.

[0030] The nickel-phosphorus multilayer alloy layer is a multilayer alloy layer, wherein a first nickel-phosphorus alloy layer (120), a second nickel-phosphorus alloy layer (130), a third nickel-phosphorus alloy layer (140), and a fourth nickel-phosphorus alloy layer (150) are sequentially stacked based on a copper substrate (110). The alloy layers constituting the nickel-phosphorus multilayer alloy layer each have different phosphorus contents. In this specification, an alloy layer with a relatively low phosphorus content is referred to as a low-phosphorus alloy layer, and an alloy layer with a relatively high phosphorus content is referred to as a high-phosphorus alloy layer.

[0031] The nickel-phosphorus multilayer alloy layer includes a first nickel-phosphorus alloy layer (120) and a third nickel-phosphorus alloy layer (140) as low-phosphorus alloy layers, and includes a second nickel-phosphorus alloy layer (130) and a fourth nickel-phosphorus alloy layer (150) as high-phosphorus alloy layers.

[0032] The first nickel-phosphorus alloy layer (120) formed on the copper substrate (110) is a low-phosphorus alloy layer with a crystalline structure having a phosphorus content of 1 to 4 wt%, and forms a strong epitaxial bond with the copper substrate (110) to absorb interfacial shear stress and prevent delamination.

[0033] The second nickel-phosphorus alloy layer (130) formed on the first nickel-phosphorus alloy layer (120) is a high-phosphorus alloy layer with an amorphous structure having a phosphorus content of 10 to 15 wt%, and is a key buffer material that dissipates the impact energy of electrolyte particles by utilizing a low Young's modulus (55 GPa).

[0034] The third nickel-phosphorus alloy layer (140) formed on the second nickel-phosphorus alloy layer (130) is a low-phosphorus alloy layer with a crystalline structure having a phosphorus content of 1 to 4 wt%, and as a mechanical support layer of the nickel-phosphorus alloy layer, it blocks the movement of dislocations at the amorphous-crystalline-amorphous interface to maximize bending stiffness through the 'nano-multilayer Hall-Petch' effect.

[0035] The fourth nickel-phosphorus alloy layer (150) formed on the third nickel-phosphorus alloy layer (140) is a high-phosphorus alloy layer with a phosphorus content of 10 to 15 wt% and a non-crystalline amorphous structure that completely blocks the diffusion of sulfur and lithium ions within a depth of 85 nm and induces conformal contact with electrolyte particles.

[0036] The ratio of the thicknesses of the first nickel-phosphorus alloy layer (120), the second nickel-phosphorus alloy layer (130), the third nickel-phosphorus alloy layer (140), and the fourth nickel-phosphorus alloy layer (150) may be 1.5 : 2 : 1.5 : 5. When the total thickness of the nickel-phosphorus alloy layer is 1.0 μm, the thickness of the first nickel-phosphorus alloy layer (120) may be about 150 nm, the thickness of the second nickel-phosphorus alloy layer (130) may be about 200 nm, the thickness of the third nickel-phosphorus alloy layer (140) may be about 150 nm, and the thickness of the fourth nickel-phosphorus alloy layer (150) may be about 500 nm.

[0037] According to the present invention, by controlling the phosphorus content and thickness of each alloy layer of the multilayer nickel-phosphorus alloy layer formed on the copper substrate (110), H of the external acidic environment + , Cl - Corrosion agents, which are corrosion-inducing substances, cannot penetrate in a straight line but move in a zigzag pattern along the interface between the high-phosphorus alloy layer and the low-phosphorus alloy layer, thereby lengthening the penetration path and enabling a tortuosity effect.

[0038] Additionally, when a corrosive agent penetrates the outermost solid alloy layer, the fourth nickel-phosphorus alloy layer (150), due to external impact or defects, the lower third nickel-phosphorus alloy layer (140) is oxidized first (sacrificial corrosion), causing the corrosion area to spread only in the horizontal direction and not proceed in the vertical direction (substrate direction), thereby making it difficult for the corrosive agent to reach the lower copper substrate (110), a galvanic fuse effect can be obtained.

[0039] The negative electrode current collector (100) for an all-solid-state battery according to the present invention forms a nickel-phosphorus alloy layer by performing an electrolytic nickel-phosphorus plating process on a copper substrate (110). A low-phosphorus alloy layer and a high-phosphorus alloy layer can be formed by changing the current density. With this process, the use of a separate plating bath is unnecessary, and the formation of an oxide layer due to movement of the plating bath can be prevented. Furthermore, since the thickness of the plating layer can be easily controlled by controlling the current density, it is possible to manufacture a negative electrode current collector for an all-solid-state battery that includes a coating layer of excellent performance through a simple process.

[0040] In addition, when manufacturing a negative electrode current collector (100) for a solid-state battery, a first nickel-phosphorus alloy layer (120), a second nickel-phosphorus alloy layer (130), and a third nickel-phosphorus alloy layer (140) are formed by electroplating on a copper substrate (110), and then a fourth nickel-phosphorus alloy layer (150) is formed by electroless plating, so that the copper substrate (110) can be sealed and thus corrosion in the gap can be suppressed at the source.

[0041] According to another aspect of the present invention, an all-solid-state battery is provided comprising a negative current collector for an all-solid-state battery, wherein the first nickel-phosphorus alloy layer having a phosphorus content smaller than that of a second nickel-phosphorus alloy layer is stacked on a copper substrate; a second nickel-phosphorus alloy layer having a phosphorus content larger than that of the first nickel-phosphorus alloy layer is stacked on the first nickel-phosphorus alloy layer; a third nickel-phosphorus alloy layer having a phosphorus content smaller than that of the second nickel-phosphorus alloy layer is stacked on the second nickel-phosphorus alloy layer; and a fourth nickel-phosphorus alloy layer having a phosphorus content larger than that of the third nickel-phosphorus alloy layer is stacked on the third nickel-phosphorus alloy layer.

[0043] The present invention will be explained in more detail below through examples.

[0044] <Example>

[0045] [Experiment on Phosphorus (P) Content Control via Current Density Control in a Single Plating Solution]

[0046] To confirm that a nickel-phosphorus multilayer alloy layer comprising alternating low-phosphorus alloy layers and high-phosphorus alloy layers according to the present invention can be continuously formed within a single plating bath without moving the copper substrate, the change in phosphorus (P) content of the plating layer according to the change in current density under single nickel-phosphorus electrolytic solution conditions was evaluated.

[0047] An electrolytic solution was prepared by including nickel salts such as nickel sulfate and nickel chloride, boric acid, and phosphoric acid (H3PO3), a source of phosphorus (P), in the composition shown in Table 1.

[0048] Parameter Amount Nickel Sulfamate Solution [mL] 300 Phosphorous acid [g / L] 27 Boric acid [g / L] 25 pH 2 Temperature[℃] 50

[0049] Current density (A / cm²) in the above single plating solution 2 Electroplating was performed on a copper substrate while varying the value, and the surface composition of the formed plating layer was analyzed using EDXS (Energy Dispersive X-ray Spectroscopy).

[0050] Figure 2 is a graph showing the change in phosphorus content according to current density in nickel-phosphorus plating on a copper substrate, and Figure 3 is EDXS measured data of the low-phosphorus alloy layer and the high-phosphorus alloy layer.

[0051] As a result of the analysis, a significant correlation was confirmed that the ratio of nickel and phosphorus co-deposition can be dramatically controlled simply by adjusting the current density without changing the chemical composition of the plating solution (Fig. 2). Accordingly, it was confirmed that a low-phosphorus alloy layer and a high-phosphorus alloy layer can be formed in the same plating bath by adjusting the current density, respectively, without using separate plating baths.

[0052] In the section where a relatively high first current density was applied, the reduction rate of nickel ions overwhelmed the reduction rate of phosphoric acid, forming a crystalline low-phosphorus (Low-P) alloy layer with a phosphorus content controlled to 1 to 4 wt%. On the other hand, in the section where a relatively low second current density was applied, the electrodeposition efficiency of phosphorus was relatively maximized, and it was confirmed that an amorphous high-phosphorus (High-P) alloy layer with a phosphorus content of 10 to 15 wt% was produced (Fig. 3).

[0053] From the behavior of phosphorus content change according to such current density and actual EDXS data, it was confirmed that the first to fourth nickel-phosphorus alloy layers can be precisely cross-stacked on a nanometer scale in a single process (in-situ) without a separate plating solution replacement or substrate cleaning process by periodically alternating the duty cycle and applied current density in the reverse pulse current (PRC) process applied to the present invention.

[0055] <Preparation Example>

[0056] [Formation of lateral encapsulation (sealing) structure]

[0057] The negative electrode current collector for all-solid-state batteries is manufactured with a three-dimensional side encapsulation structure to prevent crevice corrosion on the side of the cut copper substrate.

[0058] [Manufacturing Example 1: Masking Block Interlocked Electroforming Process]

[0059] FIG. 4 is a drawing provided to explain a method for manufacturing a negative electrode current collector for an all-solid-state battery according to another embodiment of the present invention.

[0060] The present manufacturing method is an electrolytic / electroless hybrid process. Referring to FIG. 4, a masking block is mounted on the edge of the electroforming mold to restrict the edge, and the third, second, and first alloy layers are electroplated in sequence. Copper corresponding to the substrate of the negative current collector is electroplated to an appropriate thickness, and then the masking block is removed to expose the side. Subsequently, the first, second, and third alloy layers are electroplated in sequence, and then peeled off from the electroforming mold.

[0061] When the final fourth alloy layer is electroless plated, the fourth alloy layer is plated onto all exposed surfaces due to the growth characteristics of the plating, thereby completing the encapsulation of the top, bottom, and sides without seams.

[0063] [Manufacturing Example 2: Ultra-thin copper foil roll-to-roll hybrid encapsulation process]

[0064] FIG. 5 is a drawing provided to explain a method for manufacturing a negative electrode current collector for an all-solid-state battery according to another embodiment of the present invention.

[0065] This manufacturing example is an electrolytic / electroless hybrid process that prevents mechanical bending of ultra-thin substrates of 10 μm or less and maximizes mass production, and proceeds as follows.

[0067] 1) Surface coating and film lamination

[0068] First to third alloy layers are simultaneously plated symmetrically on the upper and lower surfaces of the copper foil during operation within a single roll-to-roll electrolytic plating bath using multi-stage current control. Subsequently, ultraviolet (UV) peel-off protective films are laminated on both sides to secure substrate rigidity.

[0069] 2) Simultaneous slitting and side electroplating

[0070] The substrate is slit while the film is laminated to precisely expose only the side portion in the thickness direction. Reverse pulse (PRC) electroplating is applied to the exposed edge to form the first to third alloy layers dedicated to the side. At this time, the slitting burr is leveled in-situ by the anodic melting action of the reverse pulse.

[0071] 3) Unmasking and Hybrid Electroless Sealing

[0072] After peeling off the protective film, the substrate is immersed in a high-phosphorus (High-P) electroless plating solution. The lower third alloy layer acts as an autocatalytic agent, allowing the fourth amorphous alloy layer to uniformly coat the entire top, bottom, and cut sides 100% without pretreatment, thereby completing the hybrid encapsulation structure.

[0073] The negative electrode current collector for an all-solid-state battery manufactured by the same manufacturing process as Manufacturing Example 1 and Manufacturing Example 2 implements a defense mechanism of a lateral encapsulation structure, which can structurally prevent at the source the critical problems of coated current collectors, such as fracture of the cut edges and galvanic corrosion of the multilayer cross-section.

[0074] In the corner stress distribution mechanism, natural rounding is induced at the corners when the outermost alloy layer is formed through isotropic growth of electroless plating, which is a chemical reduction method. This significantly reduces the stress concentration factor (Kt) at right-angle corners, and the thick amorphous fourth layer with a low Young's modulus of 55 GPa acts as a 'ductile bumper,' while the inner first to third crystalline layers act as a rigid 'backbone,' thereby completely preventing corner fracture even under pressure of 50 MPa.

[0075] The galvanic corrosion prevention mechanism prevents corrosion caused by minute potential differences when the cross-section of a laminate of a first nickel-phosphorus alloy layer, a second nickel-phosphorus alloy layer, and a third nickel-phosphorus alloy layer having different phosphorus contents is exposed to the electrolyte. In the method for manufacturing a negative electrode current collector for an all-solid-state battery according to the present invention, the fourth alloy layer grows by completely burying the exposed cross-section through the conformal nature of the electroless method. As a result, all external surfaces of the current collector form an 'Equipotential High-P Amorphous Shell' as a seamlessly merged monolithic body where no potential difference exists, thereby fundamentally eliminating galvanic cell reactions.

[0076] Although embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention. Explanation of the symbols

[0078] 100: Negative current collector for all-solid-state batteries 110: Copper material 120: First nickel-phosphorus alloy layer 130: Second nickel-phosphorus alloy layer 140: Third nickel-phosphorus alloy layer 150: Quaternary nickel-phosphorus alloy layer

Claims

Claim 1 A negative electrode current collector for an all-solid-state battery comprising a multilayer protective film having a stacked structure including: a first nickel-phosphorus alloy layer having a phosphorus content (wt%) smaller than that of a second nickel-phosphorus alloy layer on a copper substrate; a second nickel-phosphorus alloy layer having a phosphorus content (wt%) larger than that of the first nickel-phosphorus alloy layer on the first nickel-phosphorus alloy layer; a third nickel-phosphorus alloy layer having a phosphorus content (wt%) smaller than that of the second nickel-phosphorus alloy layer on the second nickel-phosphorus alloy layer; and a fourth nickel-phosphorus alloy layer having a phosphorus content (wt%) larger than that of the third nickel-phosphorus alloy layer on the third nickel-phosphorus alloy layer. Claim 2 A negative electrode current collector for an all-solid-state battery comprising a multilayer protective film according to claim 1, wherein the first nickel-phosphorus alloy layer and the third nickel-phosphorus alloy layer have a phosphorus content of 1 to 4 wt%. Claim 3 A negative electrode current collector for an all-solid-state battery comprising a multilayer protective film, wherein, in claim 1, the first nickel-phosphorus alloy layer and the third nickel-phosphorus alloy layer are crystalline alloys. Claim 4 A negative current collector for an all-solid-state battery comprising a multilayer protective film according to claim 1, wherein the second nickel-phosphorus alloy layer and the fourth nickel-phosphorus alloy layer have a phosphorus content of 10 to 15 wt%. Claim 5 A negative electrode current collector for an all-solid-state battery comprising a multilayer protective film, wherein, in claim 1, the second nickel-phosphorus alloy layer and the fourth nickel-phosphorus alloy layer are amorphous alloys. Claim 6 A negative current collector for an all-solid-state battery comprising a multilayer protective film, characterized in that, in claim 1, the ratio of the thicknesses of the first nickel-phosphorus alloy layer, the second nickel-phosphorus alloy layer, the third nickel-phosphorus alloy layer, and the fourth nickel-phosphorus alloy layer is 1.5 : 2 : 1.5 :

5. Claim 7 A negative current collector for an all-solid-state battery comprising a multilayer protective film according to claim 1, wherein the thicknesses of the first nickel-phosphorus alloy layer, the second nickel-phosphorus alloy layer, the third nickel-phosphorus alloy layer, and the fourth nickel-phosphorus alloy layer are 150 nm, 200 nm, 150 nm, and 500 nm, respectively. Claim 8 A negative current collector for an all-solid-state battery comprising a multilayer protective film characterized by a total thickness of 1.0 μm, as in claim 1. Claim 9 A negative current collector for an all-solid-state battery comprising a multilayer protective film, wherein the laminate is sealed by having a plating layer formed on its side in claim 1. Claim 10 All-solid-state battery comprising a negative current collector for an all-solid-state battery comprising a multilayer protective film according to claim 1.

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