Current collector-integrated large-area and thin-film lithium electrode having low surface roughness

Abstract

A negative electrode for a secondary battery, according to an aspect of the present invention, comprises: a substrate layer serving as a negative electrode current collector; and a lithium metal layer provided on the substrate layer and formed through an electrochemical deposition method, wherein the surface roughness of the lithium metal layer may be 5.0-10 um.

Description

Large-area and thin-plate lithium electrodes integrated with a current collector having low surface roughness

[0001] The present invention relates to a large-area and thin-plate lithium electrode integral with a current collector having low surface roughness, and more specifically, to a negative electrode for a secondary battery having low surface roughness, a large-area and thin-plate shape, and formed integrally with an electrode current collector, a secondary battery including the same, and a method for manufacturing the same.

[0002] Recently, with the increasing demand for electric vehicles and portable electronic devices, the development of high-performance secondary batteries and related materials is progressing rapidly. For example, technologies are being developed to improve the capacity characteristics of secondary batteries by using materials such as silicon and lithium metal as anode materials instead of graphite.

[0003] Lithium metal has a high energy density of 3,860 mAh / g and a low electrochemical potential of -3.040 V vs. standard hydrogen electrode (SHE). Therefore, its application as a cathode in secondary batteries can significantly improve battery capacity. However, its practical commercialization has been limited by its short cycle life and the risk of internal short circuits.

[0004] The problem with lithium metal anodes is related to the uneven plating / stripping of lithium during repeated cycling. Specifically, lithium nucleation occurs locally at defect sites in the solid-electrolyte interphase (SEI) formed on the current collector, making uniform deposition difficult. Furthermore, lithium ions concentrate in specific areas, causing the growth of lithium dendrites with sharp tips toward the opposite anode. This accumulation of lithium dendrites can cause short-circuiting between the anode and cathode in the battery, resulting in capacity fading or even explosion.

[0005] In other words, lithium dendrite growth is driven by surface unevenness, and lithium dendrites primarily grow on protrusions of uneven surfaces. Therefore, there is a need to develop a technology to suppress the formation of lithium dendrites by uniformly surface-forming anodes made of lithium metal.

[0006] Furthermore, lithium metal anodes can generally be manufactured by coating lithium metal powder on a metal foil and rolling it. However, due to the nature of the rolling process, lithium metal anodes typically have a thickness of 100 μm or more. In particular, manufacturing lithium metal anodes with a thickness of at least 50 μm presents technical challenges.

[0007] The thinner the lithium metal anode, the smaller the volume of the secondary battery. However, when manufacturing lithium metal anodes using a rolling process, there are limits to how much volume can be reduced in the secondary battery. Therefore, there is a need to develop technologies to reduce the thickness of lithium metal anodes.

[0008] The inventor of the present invention completed the present invention after a long period of research and trial and error to solve these problems.

[0009] The present invention was created to solve the problems of the prior art as described above, and one object of the present invention is to provide a negative electrode for a secondary battery having low surface roughness, a large area and a thin plate shape, and formed integrally with an electrode current collector, a secondary battery including the negative electrode, and a method for manufacturing the same.

[0010] Meanwhile, other unspecified purposes of the present invention will be additionally considered within the scope that can be easily inferred from the detailed description and effects thereof below.

[0011] A negative electrode for a secondary battery according to one aspect of the present invention includes a substrate layer that functions as a negative electrode current collector; and a lithium metal layer formed on the substrate layer by an electrochemical deposition method, wherein the surface roughness of the lithium metal layer may be 5.0 um to 10 um.

[0012] In one embodiment of the present invention, the surface roughness of the lithium metal layer may be 8.0 um to 8.5 um.

[0013] In one embodiment of the present invention, an intermediate layer disposed between the substrate layer and the lithium metal layer may be further included.

[0014] In one embodiment of the present invention, the intermediate layer may include at least one of silver (Ag) fine powder, silver (Ag) nanowires, and nickel (Ni).

[0015] In one embodiment of the present invention, a lithium alloy layer is further included between the intermediate layer and the lithium metal layer, and the lithium alloy layer can be formed by a reaction between lithium of the lithium metal layer and silver of the intermediate layer.

[0016] In one embodiment of the present invention, the intermediate layer includes nickel (Ni), and further includes an additional intermediate layer provided on the intermediate layer and including tin (Sn), and the lithium alloy layer can be formed by a reaction between lithium of the lithium metal layer and a material of the additional intermediate layer.

[0017] In one embodiment of the present invention, the sum of the thicknesses of the substrate layer and the lithium metal layer may be 1 um to 50 um.

[0018] In one embodiment of the present invention, the electrochemical deposition method may be an electro-deposition method.

[0019] In one embodiment of the present invention, the lithium metal layer may include a first region and a second region having different thicknesses.

[0020] In one embodiment of the present invention, the thickness of the first region may be greater than the thickness of the second region, and the first region may be a region formed by applying a higher load than the second region.

[0021] A secondary battery according to one aspect of the present invention may include a positive electrode; a negative electrode for the secondary battery described above; and an electrolyte between the positive electrode and the negative electrode.

[0022] A method for manufacturing a negative electrode for a secondary battery according to one aspect of the present invention includes a substrate layer preparation step of preparing a substrate layer; an intermediate layer formation step of forming an intermediate layer on the substrate layer; and a lithium metal layer formation step of forming a lithium metal layer on the intermediate layer, wherein the lithium metal layer is formed using an electro-deposition method, and the surface roughness of the lithium metal layer may be 5.0 um to 10 um.

[0023] In one embodiment of the present invention, while the lithium metal layer is being formed, the intermediate layer material and the lithium metal may react to form a lithium alloy layer.

[0024] In one embodiment of the present invention, in the lithium metal layer forming step, a first region and a second region having different thicknesses are formed, the thickness of the first region being greater than the thickness of the second region, and the first region may be a region formed by applying a higher load than the second region.

[0025] The negative electrode for a secondary battery according to the present invention, the secondary battery including the same, and the manufacturing method thereof can provide a negative electrode for a secondary battery having low surface roughness, a large area, and a thin plate shape, and formed integrally with an electrode current collector.

[0026] FIGS. 1 to 4 are drawings for explaining a negative electrode for a secondary battery according to one embodiment of the present invention.

[0027] FIG. 5 is a drawing for explaining a method for manufacturing a negative electrode for a secondary battery according to one embodiment of the present invention.

[0028] Figure 6 is a photograph of a negative electrode for a secondary battery manufactured in an embodiment of the present invention.

[0029] Fig. 7 is an SEM image of the surface of the negative electrode for the secondary battery shown in Fig. 6.

[0030] Figure 8 is an image of the surface of the negative electrode for the secondary battery illustrated in Figure 6, taken using a magnifying microscope.

[0031] FIG. 9 is a drawing for explaining the surface profile of the negative electrode for a secondary battery illustrated in FIG. 6.

[0032] Fig. 10 is a drawing for explaining the surface roughness of the lithium metal layer shown in Fig. 6.

[0033] It is to be understood that the attached drawings are provided for reference only to help understand the technical concept of the present invention, and the scope of the present invention is not limited thereby.

[0034] The terms used in the present invention are selected from the most widely used general terms as much as possible, but in certain cases, there are terms arbitrarily selected by the applicant. In such cases, the meaning should be understood by considering the meaning described or used in the specific content for carrying out the invention, rather than the simple name of the term.

[0035] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0036] The purpose, specific advantages, and novel features of the present invention will become more apparent from the detailed description and preferred embodiments below. Furthermore, in describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to unnecessarily obscure the gist of the present invention.

[0037] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0038]

[0039] Below, a negative electrode for a secondary battery and a manufacturing method thereof according to one embodiment of the present invention are described in detail with reference to the attached drawings.

[0040] FIGS. 1 to 4 are drawings for explaining a negative electrode for a secondary battery according to one embodiment of the present invention.

[0041] Referring to FIGS. 1 to 4, the negative electrode for a secondary battery according to an embodiment of the present invention may have a low surface roughness. For example, the negative electrode for a secondary battery may have a surface roughness in the range of 8.0 to 8.5 μm. Preferably, the negative electrode for a secondary battery may have a surface roughness of 8.3 μm. That is, the negative electrode for a secondary battery according to an embodiment of the present invention may have a flat surface. By having a flat surface, the growth of lithium dendrites may be suppressed. Therefore, the negative electrode for a secondary battery according to an embodiment of the present invention can prevent capacity loss of a secondary battery due to lithium dendrites and reduce the risk of explosion of a secondary battery due to separator damage caused by lithium dendrites.

[0042] Typically, a secondary battery may include a positive electrode, a negative electrode, and a separator. The positive electrode, negative electrode, and separator are provided in sheet form, and the secondary battery may be manufactured by sequentially stacking the positive electrode, the separator, the negative electrode, and the separator and then winding the stack. The positive electrode, negative electrode, and separator may be impregnated with an electrolyte.

[0043] The positive electrode may include a positive electrode current collector and a positive electrode active material.

[0044] A separator separates the positive and negative electrodes and can provide a passage for ions, such as lithium ions. That is, the separator can have low resistance to the ion movement of the electrolyte and excellent electrolyte impregnation ability. For example, the separator can include glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and can be in the form of a non-woven or woven fabric. In addition, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used in lithium ion batteries, and coated separators containing ceramic components or polymer materials can also be used to secure heat resistance or mechanical strength, and can optionally be used in a single-layer or multi-layer structure. Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, and all-solid-state batteries depending on the type of separator and electrolyte used.

[0045] Among these, the all-solid-state battery is LSPS (Li 10 SnP2S 12 ), LGPS(Li 10 GeP2S 12 ) and LPSCl (Li6PS5Cl). When including a solid electrolyte, the negative electrode of the secondary battery may form a composite with the solid electrolyte. Here, the composite may mean a form in which the negative electrode is surrounded by the solid electrolyte.

[0046] As described above, when a solid electrolyte forms a composite with a negative electrode, the separator may be omitted in the secondary battery.

[0047] Furthermore, lithium secondary batteries can be classified into cylindrical, square, coin-shaped, and pouch-shaped types based on their shape. Lithium secondary batteries can also be divided into bulk and thin-film types based on their size. The structure and manufacturing method of the lithium secondary batteries described above are widely known in the field, so a detailed description will be omitted.

[0048] The negative electrode may include a substrate layer (100) that functions as a negative electrode current collector, and a lithium metal layer (200) that includes a negative electrode active material.

[0049] The substrate layer (100) may be formed of one of carbon fiber, carbon foam, metal foam, metal wire, and metal foil. The metal constituting the metal foam, metal wire, and metal foil may include at least one of silver (Ag), gold (Au), copper (Cu), calcium (Ca), zinc (Zn), aluminum (Al), tin (Sn), and nickel (Ni). For example, the substrate layer (100) may be formed of copper foil (Cu foil).

[0050] The substrate layer (100) may have a thickness of 1 um to 20 um, but is not limited thereto. The thickness of the substrate layer (100) may be varied as needed.

[0051] The lithium metal layer (200) can be formed on the substrate layer (100). That is, the lithium metal layer (200) can be formed on the exposed surface of the substrate layer (100).

[0052] The lithium metal layer (200) can serve as an anode active material that stores and releases lithium during charging and discharging of a secondary battery. The thicker the lithium metal layer (200), the more it can prevent lithium source depletion within the secondary battery, and the surface area where lithium is exposed to the electrolyte increases, thereby improving the power density and energy density of the secondary battery. However, if the lithium metal layer (200) is formed excessively thick, for example, if it is formed to a thickness of 100 μm or more, the surface roughness increases, causing an uneven distribution of the electric field and increasing the possibility of lithium dendrites being generated.

[0053] In addition, when the thickness of the lithium metal layer (200) is less than 5 um, it may be difficult for the lithium metal layer (200) to replenish the depleted lithium, which may reduce the lifespan of the secondary battery. In addition, the surface area of ​​lithium exposed to the electrolyte may be reduced, which may lower the power density and energy density of the secondary battery. Therefore, the thickness of the lithium metal layer (200) may preferably be 5 um to 50 um.

[0054] Additionally, the sum of the thicknesses of the substrate layer (100) and the lithium metal layer (200) may be 1 um to 50 um or less. Preferably, the sum of the thicknesses of the substrate layer (100) and the lithium metal layer (200) may be 20 um to 50 um or less.

[0055] In one embodiment of the present invention, the lithium metal layer (200) may have a very low surface roughness. For example, the surface roughness of the lithium metal layer (200) may be 5.0 um to 10 um. Preferably, the surface roughness of the lithium metal layer (200) may be 8.0 um to 8.5 um.

[0056] When the surface roughness of the lithium metal layer (200) exceeds 10 μm, lithium dendrites are generated during charging and discharging of the secondary battery. Lithium dendrites can destroy the separator and adversely affect the stability of the secondary battery.

[0057] In addition, when the surface roughness of the lithium metal layer (200) is less than 5.0 μm, the storage and release efficiency of lithium on the surface of the lithium metal layer (200) decreases. If the storage and release efficiency of lithium decreases, the charge and discharge efficiency of the secondary battery may decrease.

[0058] The lithium metal layer (200) can be formed through an electrochemical method. For example, the lithium metal layer (200) can be formed through an electrodeposition method. When the lithium metal layer (200) is formed through an electrochemical method such as electrodeposition, a lithium metal layer (200) having a uniform thickness can be formed on a large-area substrate layer (100).

[0059] In one embodiment of the present invention, as illustrated in FIGS. 2 and 3, the negative electrode for a secondary battery may further include an intermediate layer (300) disposed between the substrate layer (100) and the lithium metal layer (200). Here, the intermediate layer (300) may increase the contact force or adhesion between the substrate layer (100) and the lithium metal layer (200), or reduce the interfacial resistance between the substrate layer (100) and the lithium metal layer (200). The thickness of the intermediate layer (300) may not be particularly limited, but may be smaller than the thickness of the substrate layer (100).

[0060] The material applied to the intermediate layer (300) may not be particularly limited as long as it has high conductivity without causing chemical changes in the secondary battery. For example, the substrate layer (100) may include at least one of a metal material or a carbon material.

[0061] The metal material may include at least one of silver (Ag), nickel (Ni), tin (Sn), copper (Cu), silicon (Si), aluminum (Al), germanium (Ge), lead (Pb), bismuth (Bi), antimony (Sb), silicon alloy (Si-Y), and stainless steel (SUS). Here, Y constituting the silicon alloy (Si-Y) may be at least one or more of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, and a rare earth element other than silicon (Si). For example, Y, which constitutes silicon alloy (Si-Y), is composed of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), It may be at least one of aluminum (Al), gallium (Ga), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), and tellurium (Te).

[0062] The above-mentioned metallic materials have the advantages of excellent electron conductivity, low overpotential required for lithium nucleation, and small resistance, which allows for uniform and rapid electrochemical formation of lithium metal layers. In particular, when silver (Ag), silicon (Si), nickel (Ni), tin (Sn), aluminum (Al), germanium (Ge), lead (Pb), bismuth (Bi), antimony (Sb), or silicon alloy (Si-Y) are used, lithium can form a certain amount of alloy with lithium without lithium being precipitated on the surface, thereby greatly increasing the lithium capacity.

[0063] In one embodiment of the present invention, as illustrated in FIGS. 2 and 3, the intermediate layer (300) may include one of silver (Ag) and nickel (Ni). In particular, when the intermediate layer (300) includes silver, the silver (Ag) may have a form such as silver (Ag) fine powder or silver (Ag) nanowires (AgNW). This is to improve alloy formation performance in which the intermediate layer (300) and the lithium metal layer (200) react with each other to form an alloy.

[0064] As described above, when a portion of the metal material constituting the intermediate layer (300) and lithium form an alloy, as illustrated in FIG. 3, a lithium alloy layer (400) may be provided between the intermediate layer (300) and the lithium metal layer (200). Here, since the lithium alloy layer (400) is formed on the surface of the intermediate layer (300), it can be formed very thinly. For example, the lithium alloy layer (400) is formed on the surface of the intermediate layer (300), and the lithium alloy layer (400) may have a thickness of several nm to several tens of nm. For example, the lithium alloy layer (400) may have a thickness of 20 nm or less. That is, the lithium alloy layer (400) may be provided in the form of an atomic layer.

[0065] When the intermediate layer (300) includes silver (Ag), the lithium alloy layer (400) may be composed of an alloy of lithium (Li) and silver (Ag). When the intermediate layer (300) includes nickel (Ni), the lithium alloy layer (400) may be composed of an alloy of lithium (Li) and nickel (Ni).

[0066] In addition, as illustrated in FIG. 4, an additional intermediate layer (310) may be provided on the intermediate layer (300). Here, when the additional intermediate layer (320) is provided, the intermediate layer (300) may include nickel (Ni), and the additional intermediate layer (310) may include tin (Sn). A lithium alloy layer (400) may be provided between the additional intermediate layer (310) and the lithium metal layer (200). Since the additional intermediate layer (310) includes tin (Sn), the lithium alloy layer (400) may be composed of an alloy of lithium (Li) and tin (Sn).

[0067] Additionally, the carbon material may include at least one of a carbon-based conductive material, graphite, graphene, and carbon nanotubes (CNTs).

[0068] The electronic conductivity of carbon materials is lower than that of metal materials. Therefore, when the substrate layer (100) is composed of a carbon material, the overpotential required for nucleation is higher and the resistance is higher than that of a metal material, so the electrochemical deposition of lithium may proceed relatively slowly. However, carbon materials have a high specific surface area, and carbon combined with lithium (such as LiC6) has superior stability compared to lithium metal, which can have a positive effect on the capacity and life characteristics of a secondary battery.

[0069]

[0070] Below, a method for manufacturing the negative electrode for the secondary battery described above is described with reference to FIG. 5 together with FIGS. 1 to 4.

[0071] FIG. 5 is a drawing for explaining a method for manufacturing a negative electrode for a secondary battery according to one embodiment of the present invention.

[0072] Referring to FIG. 5, a method for manufacturing a negative electrode for a secondary battery according to one embodiment of the present invention may include a substrate layer preparation step (S100), an intermediate layer formation step (S200), and a lithium metal layer formation step (S300).

[0073] In the substrate layer preparation step (S100), a substrate layer (100) for manufacturing a negative electrode for a secondary battery can be prepared.

[0074] The substrate layer (100) can serve as a negative electrode current collector. In addition, the substrate layer (100) can be formed of one of carbon fiber, carbon foam, metal foam, metal wire, and metal foil. The metal constituting the metal foam, metal wire, and metal foil can include at least one of silver (Ag), gold (Au), copper (Cu), calcium (Ca), zinc (Zn), aluminum (Al), tin (Sn), and nickel (Ni). For example, the substrate layer (100) can be formed of copper foil (Cu foil).

[0075] The substrate layer (100) may have a thickness of 1 um to 20 um, but is not limited thereto. The thickness of the substrate layer (100) may be varied as needed.

[0076] After preparing the substrate layer (100), an intermediate layer forming step (S200) can be performed.

[0077] In the intermediate layer formation step (S200), an intermediate layer (300) may be formed on the substrate layer (100). The material applied to the intermediate layer (300) may not be particularly limited as long as it has high conductivity and does not induce chemical changes in the secondary battery. For example, the substrate layer (100) may include at least one of a metal material and a carbon material.

[0078] The intermediate layer (300) can be formed using various methods. For example, it can be formed using printing methods such as dip coating using metal ink or paste, screen printing, inkjet printing, and roll printing. Alternatively, the intermediate layer can be formed using a plating method using an electrolytic method or an electroless method. Furthermore, the intermediate layer (300) can be formed using a deposition method such as thermal deposition, physical vapor deposition, and chemical vapor deposition. Alternatively, the intermediate layer (300) can be formed using a coating method such as spin coating.

[0079] After forming the intermediate layer (300), a lithium metal layer forming step (S300) can be performed.

[0080] In the lithium metal layer formation step (S300), a lithium metal layer (200) can be formed on the intermediate layer (300).

[0081] The lithium metal layer (200) can be formed on the surface of the intermediate layer (300) using an electrochemical method. For example, the lithium metal layer (200) can be formed using an electro-deposition method.

[0082] In the electrodeposition method, scrap composed of lithium metal, lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium scrap, or black powder separated and crushed from a used secondary battery can be used as a counter electrode. Then, lithium ions are extracted and controlled from the counter electrode and moved onto an intermediate layer (300), and then the lithium ions are reduced on the intermediate layer (300) to form a lithium metal layer (200).

[0083] As described above, the lithium metal layer (200) formed using the electrodeposition method may have very low surface roughness. For example, the surface roughness of the lithium metal layer (200) may be 5.0 um to 10 um. Preferably, the surface roughness of the lithium metal layer (200) may be 8.0 um to 8.5 um.

[0084] Meanwhile, the negative electrode for a secondary battery in which a lithium metal layer (200) is formed may be provided in a composite form with a lithium metal electrode, a silicon electrode, a graphite-silicon composite electrode, etc.

[0085] In one embodiment of the present invention, while forming the lithium metal layer (200), a metal material of the intermediate layer (300) and a portion of the lithium of the lithium metal layer (200) may form an alloy on the surface of the intermediate layer (300). Accordingly, as illustrated in FIGS. 3 and 4 , a lithium alloy layer (400) may be formed between the intermediate layer (300) and the lithium metal layer (200).

[0086] In one embodiment of the present invention, as illustrated in FIG. 4, an additional intermediate layer (310) may be formed on the intermediate layer (300) prior to the formation of the lithium metal layer (200).

[0087] In one embodiment of the present invention, when a high load is locally applied to a portion of the substrate layer (100) while forming the lithium metal layer (200), the thickness of the lithium metal layer (200) may be formed differently depending on the region. Here, locally applying a high load may mean that a stronger current flows in the region or a stronger electric field is applied compared to other regions.

[0088] For example, the lithium metal layer (200) may include a first region and a second region having different thicknesses. Here, the thickness of one of the first region and the second region, for example, the first region, may be greater than the thickness of the other of the first region and the second region, for example, the second region. In addition, when forming the lithium metal layer (200), the first region may be a region formed by applying a high load current compared to the second region.

[0089] Meanwhile, in one embodiment of the present invention, the formation of an intermediate layer (300) after preparing a base layer (100) and then forming a lithium metal layer (200) on the intermediate layer (300) has been described as an example, but is not limited thereto. For example, the intermediate layer (300) may be omitted, and the lithium metal layer (200) may be formed directly on the base layer (100).

[0090] As described above, when a portion of the metal material constituting the intermediate layer (300) and lithium form an alloy, a lithium alloy layer (400) may be provided between the intermediate layer (300) and the lithium metal layer (200), as illustrated in FIGS. 3 and 4. Here, since the lithium alloy layer (400) is formed on the surface of the intermediate layer (300), it can be formed very thinly. For example, the lithium alloy layer (400) may be formed on the surface of the intermediate layer (300) and may be provided in the form of an atomic layer.

[0091]

[0092] [Example]

[0093] Example 1.

[0094] Lithium metal was deposited on copper foil to form a negative electrode for a secondary battery including a copper foil and a lithium metal layer, as shown in Fig. 6.

[0095]

[0096] Example 2.

[0097] An intermediate layer was formed using silver nanowires on copper foil, and lithium metal was deposited on the intermediate layer to form a negative electrode for a secondary battery including copper foil, an intermediate layer including silver nanowires, and a lithium metal layer.

[0098]

[0099] As shown in Fig. 9, the profile analysis result of the negative electrode for a secondary battery according to Example 1 shows that the negative electrode for a secondary battery according to Example 1 has a thickness of 27.3 um. That is, it can be seen that the negative electrode for a secondary battery manufactured through the method for manufacturing a negative electrode for a secondary battery according to an embodiment of the present invention can be manufactured with a thickness of 50 um or less.

[0100] In addition, the surface of the negative electrode for secondary batteries according to Examples 1 and 2, i.e., the surface of the lithium metal layer, was observed to have a low area average roughness (Sa), as shown in FIGS. 7 to 10. In particular, as shown in FIG. 10, the surface roughness of the lithium metal layer was observed to be 8.3 μm.

[0101]

[0102] The present invention is not limited to the embodiments described above, and may include new embodiments that combine at least two of the above embodiments or combine at least one of the above embodiments with a known technology.

[0103] Although the present invention has been described in detail through specific examples, this is intended to specifically explain the present invention, and the present invention is not limited thereto, and it will be apparent that modifications and improvements can be made by those skilled in the art within the technical spirit of the present invention.

[0104] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

[0105] [Explanation of symbols]

[0106] 100: Base layer

[0107] 200: Lithium metal layer

[0108] 300: Middle layer

[0109] 400: Lithium alloy layer

Claims

1. A substrate layer that acts as a negative electrode collector; and It comprises a lithium metal layer formed through an electrochemical deposition method and provided on the above substrate layer, A negative electrode for a secondary battery, wherein the surface roughness of the lithium metal layer is 5.0 um to 10 um.

2. In paragraph 1, A negative electrode for a secondary battery having a surface roughness of the lithium metal layer of 8.0 um to 8.5 um.

3. In paragraph 2, A negative electrode for a secondary battery further comprising an intermediate layer disposed between the substrate layer and the lithium metal layer.

4. In paragraph 3, The above intermediate layer is a negative electrode for a secondary battery comprising one of silver (Ag) fine powder, silver (Ag) nanowires, and nickel (Ni).

5. In paragraph 4, Further comprising a lithium alloy layer disposed between the intermediate layer and the lithium metal layer, The lithium alloy layer is a negative electrode for a secondary battery formed by a reaction between lithium of the lithium metal layer and a material of the intermediate layer.

6. In paragraph 5, The above intermediate layer contains nickel (Ni), Provided on the above intermediate layer, further comprising an additional intermediate layer containing tin (Sn), The lithium alloy layer is a negative electrode for a secondary battery formed by a reaction between lithium of the lithium metal layer and a material of the additional intermediate layer.

7. In paragraph 2, A negative electrode for a secondary battery, wherein the sum of the thicknesses of the substrate layer and the lithium metal layer is 1 um to 50 um.

8. In paragraph 2, The above electrochemical deposition method is an electro-deposition method for a secondary battery negative electrode.

9. In paragraph 2, A negative electrode for a secondary battery, wherein the lithium metal layer includes a first region and a second region having different thicknesses.

10. In paragraph 9, The thickness of the first region is greater than the thickness of the second region, A negative electrode for a secondary battery, wherein the first region is a region formed by applying a higher load than the second region.

11. Bipolar; A negative electrode for a secondary battery according to any one of claims 1 to 10; and A secondary battery comprising an electrolyte between the positive electrode and the negative electrode.

12. Substrate preparation step for preparing the substrate layer; An intermediate layer forming step of forming an intermediate layer on the above substrate layer; and A lithium metal layer forming step is included, wherein a lithium metal layer is formed on the intermediate layer. The above lithium metal layer is formed using an electro-deposition method, A method for manufacturing a negative electrode for a secondary battery, wherein the surface roughness of the lithium metal layer is 5.0 um to 10 um.

13. In paragraph 12, A method for manufacturing a negative electrode for a secondary battery, wherein the surface roughness of the lithium metal layer is 8.0 um to 8.5 um.

14. In paragraph 13, A method for manufacturing a negative electrode for a secondary battery, wherein the intermediate layer comprises silver (Ag) fine powder or silver (Ag) nanowires.

15. In paragraph 14, A method for manufacturing a negative electrode for a secondary battery, wherein the intermediate layer material and lithium metal react to form a lithium alloy layer while the lithium metal layer is formed.

16. In paragraph 15, In the lithium metal layer forming step, Forming a first region and a second region having different thicknesses, The thickness of the first region is greater than the thickness of the second region, A method for manufacturing a negative electrode for a secondary battery, wherein the first region is a region formed by applying a higher load than the second region.

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