Positive electrode for lithium secondary battery and method for manufacturing same

Abstract

The present disclosure relates to a positive electrode for a lithium secondary battery and a method for manufacturing same. The positive electrode for a lithium secondary battery according to the present disclosure comprises a positive electrode current collector, a first positive electrode mixture layer disposed on the positive electrode current collector, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer, wherein the capacity ratio of a sacrificial positive electrode active material in the first positive electrode mixture layer may be different from that of the sacrificial positive electrode active material in the second positive electrode mixture layer.

Description

Cathode for lithium secondary battery and method for manufacturing same

[0001] The present disclosure relates to a positive electrode for a lithium secondary battery and a method for manufacturing the same.

[0002] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for high-energy density, high-capacity secondary batteries. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries.

[0003] A lithium secondary battery is a battery that includes a positive electrode and a negative electrode that contain active materials capable of intercalating and deintercalating lithium ions, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and negative electrode.

[0004] Lithium secondary batteries currently on the market primarily use carbon-based anode materials, such as graphite. Carbon-based anode materials exhibit no volume change during charge and discharge, contributing to the stability of lithium secondary batteries. Graphite's theoretical electrical capacity is relatively small, at approximately 372 mAh / g.

[0005] In contrast, numerous studies have recently been conducted on lithium metal batteries that do not coat the anode current collector with a cathode active material to increase energy density. Lithium metal batteries lacking a cathode active material layer offer a significantly higher energy density per unit weight compared to conventional lithium-ion batteries, which feature a thick carbon-based cathode active material coated on the anode current collector.

[0006] However, such lithium metal batteries lack a source of extra lithium, leading to continuous lithium depletion during charge and discharge and irreversible reactions that can degrade their lifespan. Therefore, to dramatically improve the lifespan of a lithium metal battery without a negative active material layer, a means of supplying additional lithium within the cell is necessary.

[0007] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0008] One embodiment provides a positive electrode for a lithium secondary battery and a method for manufacturing the same to solve the above technical problem.

[0009] Another embodiment provides a lithium secondary battery including a positive electrode for a lithium secondary battery for solving the above technical problem.

[0010] According to one embodiment of the present invention for solving the above technical problem, a positive electrode for a lithium secondary battery includes a positive electrode current collector, a first positive electrode mixture layer disposed on the positive electrode current collector, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer, wherein a capacity ratio occupied by a sacrificial positive electrode active material in the first positive electrode mixture layer may be different from a capacity ratio occupied by a sacrificial positive electrode active material in the second positive electrode mixture layer.

[0011] A lithium secondary battery according to one embodiment of the present invention for solving the above technical problem may include a positive electrode for a lithium secondary battery according to one embodiment, a negative electrode including a negative electrode current collector, and an electrolyte disposed between the positive electrode and the negative electrode.

[0012] A method for manufacturing a positive electrode for a lithium secondary battery according to one embodiment of the present invention for solving the above technical problem includes a step of disposing a first positive electrode mixture layer on a positive electrode current collector and a step of disposing a second positive electrode mixture layer on the first positive electrode mixture layer, wherein a capacity ratio occupied by a sacrificial positive electrode active material of the first positive electrode mixture layer may be different from a capacity ratio occupied by a sacrificial positive electrode active material of the second positive electrode mixture layer.

[0013] According to some embodiments of the present disclosure, a positive electrode for a lithium secondary battery includes a sacrificial positive electrode that forms a lithium metal layer on a negative electrode substrate in a fusion step, thereby compensating for lithium consumption due to SEI (Solid Electrolyte Interphase) formation or other side reactions during charge and discharge, thereby dramatically improving the life characteristics of the secondary battery.

[0014] In some embodiments of a lithium secondary battery cathode according to the present disclosure, unlike the first cathode composite layer in contact with the substrate, the second cathode composite layer can improve output characteristics by minimizing the conductive agent / binder ratio to increase ion transfer resistance. Furthermore, an optimized ratio of cathode compositions for each layer can be provided in the cathode having such a structure.

[0015] According to some embodiments of the present disclosure, a lithium metal battery can be provided easily and economically by omitting a number of processes, such as a wide-width process or a thin-film process, compared to a lithium metal battery in which lithium metal is introduced in advance onto a negative electrode current collector before charging.

[0016] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects that are not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0017] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0018] Figure 1 schematically illustrates the structure of a positive electrode for a lithium secondary battery according to one embodiment.

[0019] Figure 2 shows a cross-sectional SEM image of a positive electrode for a lithium secondary battery according to one embodiment.

[0020] Figure 3 shows the appearance of a lithium secondary battery before charging according to one embodiment.

[0021] Figure 4 shows the appearance of a lithium secondary battery after charging according to one embodiment.

[0022] Figure 5 is a flowchart showing an example of a method for manufacturing a positive electrode for a lithium secondary battery according to the present disclosure.

[0023] Figure 6 is a schematic diagram illustrating a lithium secondary battery according to one embodiment.

[0024] Figure 7 is a schematic diagram illustrating a lithium secondary battery according to one embodiment.

[0025] Figure 8 is a schematic diagram illustrating a lithium secondary battery according to one embodiment.

[0026] Figure 9 is a schematic diagram illustrating a lithium secondary battery according to one embodiment.

[0027] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0028] Unless otherwise specified herein, when a part such as a layer, film, region, plate, etc. is said to be “on” another part, this includes not only cases where it is “directly on” the other part, but also cases where there is another part in between.

[0029] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0030] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0031] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0032] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein. The singular expression "singular" includes plural expression unless the context clearly indicates otherwise.

[0033] In this specification, the terms "include" or "have" are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials or combinations thereof.

[0034] The term "combination of these" in this specification means a mixture or combination of one or more of the described components, and may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0035] As used herein, the term "and / or" is meant to include any and all combinations of one or more of the items described herein. As used herein, the term "or" means "and / or."

[0036] When a part such as a layer, film, region, or plate is said to be “on” another part in this specification, this includes not only cases where it is directly on top of the other part, but also cases where there is another part in between.

[0037] Although terms such as first, second, etc. may be used in this specification to describe various components, the components should not be limited by the terms. The terms are used solely to distinguish one component from another.

[0038] As used herein, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0039] As used herein, “alloy” means a mixture of two or more metals.

[0040] In this specification, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0041] In this specification, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0042] In this specification, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material.

[0043] In this specification, “delithiation” and “delithiate” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0044] In this specification, “charging” and “charging” mean the process of providing electrochemical energy to a battery.

[0045] In this specification, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0046] In this specification, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during the discharge process.

[0047] In this specification, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0048] The term alkyl as used in chemical formulas herein refers to a fully saturated branched or unbranched (or straight-chain or linear) hydrocarbon.

[0049] As used herein, non-limiting examples of alkyl include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, iso-amyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, and the like.

[0050] In the present specification, one or more hydrogen atoms of alkyl are selected from the group consisting of a halogen atom, a C1-C20 alkyl group substituted with a halogen atom (e.g., CCF3, CHCF2, CH2F, CCl3, etc.), a C1-C20 alkoxy, a C2-C20 alkoxyalkyl, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or a salt thereof, a sulfonyl group, a sulfamoyl group, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, or a C1-C20 alkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C1-C20 heteroalkyl group, a C6-C20 aryl group, a C6-C20 arylalkyl group, a C6-C20 heteroaryl group, a C7-C20 It may be substituted with a heteroarylalkyl group, a C6-C20 heteroaryloxy group, a C6-C20 heteroaryloxyalkyl group, or a C6-C20 heteroarylalkyl group.

[0051] In this specification, the term halogen atom includes fluorine, bromine, chlorine, iodine, and the like.

[0052] As used herein, the term C1-C20 alkyl group substituted with a halogen atom refers to a C1-C20 alkyl group substituted with one or more halo groups, and non-limiting examples thereof include polyhaloalkyl containing monohaloalkyl, dihaloalkyl or perhaloalkyl.

[0053] In this specification, monohaloalkyl refers to an alkyl group having one iodine, bromine, chlorine or fluorine, and dihaloalkyl and polyhaloalkyl refer to an alkyl group having two or more identical or different halo atoms.

[0054] In this specification, the term aryl group used in chemical formulas is used alone or in combination to mean an aromatic hydrocarbon containing one or more rings.

[0055] As used herein, the term aryl also includes groups in which an aromatic ring is fused to one or more cycloalkyl rings.

[0056] As used herein, non-limiting examples of aryl include phenyl, naphthyl, tetrahydronaphthyl, etc.

[0057] In this specification, one or more hydrogen atoms in the aryl group may be substituted with a substituent similar to that in the case of the alkyl group described above.

[0058] In this specification, one or more hydrogen atoms in the carbon ring can be substituted with a substituent similar to that in the case of the alkyl group described above.

[0059] Hereinafter, exemplary embodiments will be described in more detail.

[0060] anode

[0061] Figure 1 schematically illustrates the structure of a positive electrode (100) for a lithium secondary battery according to one embodiment.

[0062] Referring to FIG. 1, a positive electrode (100) for a lithium secondary battery according to one embodiment of the present invention may include a positive electrode current collector (110), a first positive electrode mixture layer (120) disposed on the positive electrode current collector (110), and a second positive electrode mixture layer (130) disposed on the first positive electrode mixture layer (120).

[0063] In one embodiment, the cathode current collector (110) may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof.

[0064] In one embodiment, the positive electrode current collector (110) may include a base film and a metal substrate layer disposed on one or both sides of the base film, similar to the negative electrode current collector described below.

[0065] The thickness of the first positive electrode mixture layer (120) and the thickness of the second positive electrode mixture layer (130) may vary depending on the design of those skilled in the art. However, as illustrated in FIG. 1, the thickness of the first positive electrode mixture layer (120) may be thicker than the thickness of the second positive electrode mixture layer (130). For example, the thickness of the first positive electrode mixture layer (120) and the thickness of the second positive electrode mixture layer (130) may have a ratio of 1:9 to 3:7.

[0066] The first positive electrode active material layer (120) may include a first positive electrode active material, a conductive material, and a binder. Here, the first positive electrode active material may include a sacrificial positive electrode active material. In addition, the second positive electrode active material layer (130) may include a second positive electrode active material, a conductive material, and a binder. Here, the second positive electrode active material may include a sacrificial positive electrode active material. In one embodiment, the sacrificial positive electrode active material included in the second positive electrode active material may be the same material as the sacrificial positive electrode active material included in the first positive electrode active material.

[0067] Specifically, the sacrificial cathode active material of the first cathode composite layer (120) or the second cathode composite layer (130) may include Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P, or a combination thereof.

[0068] According to some embodiments of the present disclosure, a positive electrode (100) for a lithium secondary battery includes a sacrificial positive electrode (or a sacrificial positive electrode active material) that forms a lithium metal layer on a negative electrode substrate in a ignition stage, thereby compensating for lithium consumption due to SEI formation or other side reactions during charge and discharge, thereby drastically improving the life characteristics of the secondary battery.

[0069] However, the sacrificial cathode active material may function as an insulator within the cathode (100) for a lithium secondary battery due to a lack of electronic conductivity caused by the loss of lithium ions after charging. Therefore, the composite density of the cathode (100) for a lithium secondary battery may decrease by the proportion of the sacrificial cathode active material.

[0070] Therefore, in one embodiment, the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode mixture layer (120) may be designed to be different from the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode mixture layer (130). Here, the capacity ratio may be proportional to the capacity that a lithium secondary battery may have when the lithium secondary battery is manufactured using the corresponding positive electrode for a lithium secondary battery. That is, the ratio occupied by the sacrificial positive electrode active material in the first positive electrode active material and the ratio occupied by the sacrificial positive electrode active material in the second positive electrode active material may be different from each other.

[0071] Specifically, the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode mixture layer (120) may be greater than the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode mixture layer (130). Here, the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode mixture layer (120) may be 5% to 60%, 10% to 50%, or 20% to 50% relative to the total capacity of the first positive electrode mixture layer (120). On the other hand, the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode mixture layer (130) may be 1% to 50%, 5% to 40%, or 10% to 30% relative to the total capacity of the second positive electrode mixture layer (130). That is, by lowering the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode mixture layer (130), which occupies a higher proportion of the entire positive electrode (100), the output characteristics can be improved while also improving the life characteristics of the secondary battery.

[0072] For example, the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode composite layer (120) may be 30% of the total capacity of the first positive electrode composite layer (120), and the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode composite layer (130) may be 10% of the total capacity of the second positive electrode composite layer (130).

[0073] According to one embodiment, the weight ratio of the first positive electrode active material in the first positive electrode mixture layer (120) may be equal to or less than the weight ratio of the second positive electrode active material in the second positive electrode mixture layer (130). That is, the weight ratio of the conductive material and the binder in the first positive electrode mixture layer (120) may be equal to or greater than the weight ratio of the conductive material and the binder in the second positive electrode mixture layer (130).

[0074] The binder occupying a high weight ratio in the first positive electrode mixture layer (120) can strengthen the bonding between the positive electrode current collector (110) and the first positive electrode mixture layer (120), thereby increasing the mechanical strength of the positive electrode (100) and reducing the movement resistance by securing a current movement path. However, if the binder amount increases, the capacity of the mixture layer decreases, and as the mixture density decreases, electron movement between active materials becomes difficult, which may increase the internal resistance. Therefore, it is preferable that the binder weight ratio be low in the second mixture layer (130) which is close to the negative electrode and occupies a high weight ratio.

[0075] Here, the first positive electrode active material may be included in an amount ranging from 95 wt% to 98 wt% of the total weight of the first positive electrode composite layer. In addition, the second positive electrode active material may be included in an amount ranging from 98 wt% to 99 wt% of the total weight of the second positive electrode composite layer.

[0076] For example, the first positive electrode active material may be 96 wt% of the total weight of the first positive electrode composite layer, and the second positive electrode active material may be 98 wt% of the total weight of the second positive electrode composite layer.

[0077] For example, the first positive electrode active material may be 98 wt% of the total weight of the first positive electrode composite layer, and the second positive electrode active material may be 98 wt% of the total weight of the second positive electrode composite layer.

[0078] A cross-sectional SEM image of a positive electrode for a lithium secondary battery according to one embodiment is shown in FIG. 2. Referring to FIG. 2, a positive electrode (200) for a lithium secondary battery according to one embodiment of the present invention may include a positive electrode current collector (210), a first positive electrode mixture layer (220) disposed on the positive electrode current collector (210), and a second positive electrode mixture layer (230) disposed on the first positive electrode mixture layer (220). The description of each component here is the same as in FIG. 1.

[0079] In some embodiments of a lithium secondary battery cathode according to the present disclosure, unlike the first cathode composite layer in contact with the substrate, the second cathode composite layer can improve output characteristics by minimizing the conductive agent / binder ratio to increase ion transfer resistance. Furthermore, an optimized ratio of cathode compositions for each layer can be provided in the cathode having such a structure.

[0080]

[0081] Method for manufacturing anode

[0082] Figure 5 is a flowchart showing an example of a method for manufacturing a positive electrode for a lithium secondary battery according to the present disclosure.

[0083] A method for manufacturing a positive electrode for a lithium secondary battery according to one embodiment of the present invention (500) can be initiated by disposing a first positive electrode mixture layer on a positive electrode current collector (S510).

[0084] Thereafter, a second positive electrode mixture layer can be placed on the first positive electrode mixture layer (S520). At this time, the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer can have a ratio of 1:9 to 9:1, 1:9 to 2:8, or 1:9 to 3:7.

[0085] Here, the capacity ratio occupied by the sacrificial positive electrode active material of the first positive electrode composite layer may be different from the capacity ratio occupied by the sacrificial positive electrode active material of the second positive electrode composite layer. Specifically, the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode composite layer may be greater than the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode composite layer.

[0086] Additionally, the weight ratio of the first positive electrode active material in the first positive electrode composite layer may be smaller than the weight ratio of the second positive electrode active material in the second positive electrode composite layer.

[0087] A method (500) for manufacturing a positive electrode for a lithium secondary battery according to one embodiment may further include a step of vacuum drying the first positive electrode mixture layer and the second positive electrode mixture layer. A method (500) for manufacturing a positive electrode for a lithium secondary battery according to one embodiment may further include a step of rolling the first positive electrode mixture layer and the second positive electrode mixture layer.

[0088] According to some embodiments of the present disclosure, a lithium metal battery can be provided easily and economically by omitting a number of processes, such as a wide-width process or a thin-film process, compared to a lithium metal battery in which lithium metal is introduced in advance onto a negative electrode current collector before charging.

[0089]

[0090] lithium secondary battery

[0091] Fig. 3 illustrates a state (300) before charging of a lithium secondary battery according to one embodiment. In addition, Fig. 4 illustrates a state (302) after charging of a lithium secondary battery according to one embodiment.

[0092] Referring to FIGS. 3 and 4, a lithium secondary battery according to one embodiment of the present invention may include a positive electrode for a lithium secondary battery according to one embodiment of the present invention described above, a negative electrode including a negative electrode current collector (350), and an electrolyte (340) disposed between the positive electrode and the negative electrode.

[0093] That is, a lithium secondary battery according to one embodiment may include a cathode current collector (310), a first cathode mixture layer (320) disposed on the cathode current collector (310), a second cathode mixture layer (330) disposed on the first cathode mixture layer (320), a cathode current collector (350), and an electrolyte (340) disposed between the cathode and the cathode.

[0094] Here, the negative electrode current collector (350) may include a foil structure layer containing copper (Cu) or a sheet structure layer containing copper, as will be described later.

[0095] Referring to FIG. 3, a lithium secondary battery according to one embodiment may be free of a negative electrode active material layer before charging. That is, the negative electrode current collector (350) may be exposed to the electrolyte (340).

[0096] Referring to FIG. 4, in a lithium secondary battery according to one embodiment, a lithium metal layer (452) may be formed on an anode current collector (350) after charging. Specifically, the lithium metal layer (452) may be disposed between the anode current collector (350) and the electrolyte (340). For example, the lithium metal layer (452) may be a lithium electrodeposition layer. For example, the lithium metal layer (452) may include a lithium alloy and a lithium metal. For example, the lithium alloy included in the lithium metal layer may weaken the reactivity of the lithium metal, thereby effectively preventing a side reaction between the lithium metal layer and the polymer electrolyte. In addition, the lithium metal layer has excellent electrical conductivity, so that the internal resistance of a lithium secondary battery including the lithium metal layer may be reduced. Accordingly, a lithium secondary battery including a lithium metal layer may have improved not only life characteristics but also charge and discharge efficiency.

[0097] Here, the lithium constituting the lithium metal layer (452) may be derived from the sacrificial anode included in the first cathode composite layer (320) or the second cathode composite layer (330). For example, the lithium metal layer (452) may be generated by lithium ions included in the electrolyte (340) being deposited on the negative electrode current collector (350) by originating from the sacrificial anode (or sacrificial anode active material) as the lithium secondary battery is charged and discharged.

[0098] In particular, in conventional lithium ion batteries, only the irreversible reaction at the initial stage of charge and discharge is compensated for, so a small proportion of the sacrificial cathode active material is sufficient. However, in a lithium metal secondary battery according to one embodiment, since lithium derived from the sacrificial cathode is continuously utilized during charge and discharge, a large amount of the sacrificial cathode active material may be required compared to a lithium ion battery of the same capacity.

[0099] In one embodiment, the lithium metal layer (452) may include, for example, lithium foil, lithium powder, plated lithium, a carbon-based material, or a combination thereof. For example, the lithium metal layer (452) may include lithium foil. In this case, the lithium metal layer (452) may be a negative electrode active material layer. For example, the lithium metal layer (452) may be introduced by coating a slurry including lithium powder and a binder onto the negative electrode current collector. For example, the binder may be a fluorine-based binder such as polyvinylidene fluoride (PVDF).

[0100] In one embodiment, the lithium metal layer (452) may include only deposited lithium metal or lithium alloy. In this case, the lithium metal layer (452) may be a lithium electrodeposited layer.

[0101] In one embodiment, the lithium metal layer (452) may not include a carbon-based negative electrode active material. Accordingly, the lithium metal layer (452) may be formed of a metal-based negative electrode active material.

[0102] For example, the thickness of the lithium metal layer (452) may be, for example, 0.1 ㎛ to 100 ㎛, 0.1 ㎛ to 80 ㎛, 1 ㎛ to 80 ㎛, or 10 ㎛ to 80 ㎛, but is not necessarily limited to this range and may be adjusted according to the shape, capacity, etc. of the required lithium secondary battery. If the thickness of the lithium metal layer (452) increases excessively, the structural stability of the lithium secondary battery may deteriorate and side reactions may increase. If the thickness of the lithium metal layer (452) is excessively small, the energy density of the lithium metal battery may decrease.

[0103] According to one embodiment, the thickness of the lithium foil included in the lithium metal layer (452) may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, or 10 μm to 30 μm, or 10 μm to 80 μm. When the lithium foil has a thickness in this range, the life characteristics of the lithium battery can be further improved.

[0104] According to one embodiment, the particle size of the lithium powder included in the lithium metal layer (452) may be, for example, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. When the lithium powder has a thickness within this range, the life characteristics of the lithium secondary battery can be further improved.

[0105] FIGS. 6 to 9 are schematic diagrams illustrating a lithium secondary battery according to one embodiment, wherein FIG. 6 is a cylindrical battery, FIG. 7 is a square battery, and FIGS. 8 and 9 are pouch-type battery forms. Referring to FIGS. 6 to 9, a lithium secondary battery (1) includes a battery structure (7, electrode assembly) having a separator (4, separator) interposed between a positive electrode (3) and a negative electrode (2), and a case (5) in which the battery structure (7) is built. The positive electrode (3), the negative electrode (2), and the separator (4) may be impregnated with an electrolyte (not shown). The lithium secondary battery (1) may include an assembly (6, sealing member) that seals the case (5), as shown in FIG. 6. In addition, in FIG. 7, the lithium secondary battery (1) may include a positive electrode lead tab (3') and a positive electrode terminal (3"), a negative electrode lead tab (2'), and a negative electrode terminal (2"). As shown in FIGS. 8 and 9, a lithium secondary battery (1) may include electrode tabs (70), i.e., a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical paths for inducing current formed in a battery structure (7) to the outside.

[0106] Referring to FIG. 6, a lithium secondary battery (1) according to one embodiment includes the above-described positive electrode (3), the above-described negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a case (5). A polymer electrolyte or a liquid electrolyte is injected into the case (5) and sealed with a cap assembly (6), thereby completing the lithium secondary battery (1). The case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0107] Referring to FIG. 7, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound, folded, or laminated to form a battery structure (7). The formed battery structure (7) is accommodated in a case (5). A composition for forming a positive electrode electrolyte is injected into the case (5), cross-linked, and sealed to complete the lithium secondary battery (1). The case (5) is square, but is not necessarily limited to this shape, and may be, for example, cylindrical, thin-film, etc. A positive electrode lead tab (3') and a positive electrode terminal (3") are electrically connected to the positive electrode (3). A negative electrode lead tab (2') and a negative electrode terminal (2") are electrically connected to the negative electrode (2).

[0108] Referring to FIG. 8, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a case (5). An electrode tab (70) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. The above-described polymer electrolyte or liquid electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is not necessarily limited to a square shape, and may be, for example, a cylindrical shape, a thin-film shape, etc.

[0109] Referring to FIG. 9, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). The aforementioned polymer electrolyte including the separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. For example, a battery structure (7) is stacked in a bi-cell structure and then accommodated in a case (5). A positive electrode tab (71) and a negative electrode tab (72), which serve as electrical paths for guiding the current formed in the battery structure (7) to the outside, may be included. A polymer electrolyte or a liquid electrolyte is injected into the case (5) and sealed, thereby completing the lithium secondary battery (1). The case (5) is not necessarily limited to a square shape, and may be, for example, a cylindrical shape, a thin film shape, etc.

[0110] However, the present invention is not limited thereto, and the case (5) may be configured in various shapes such as circular, pouch-shaped, etc. For example, the pouch-shaped lithium secondary battery corresponds to each of the lithium secondary batteries (1) of FIGS. 6 to 13 in which a pouch is used as the case (5). The pouch-shaped lithium secondary battery includes one or more battery structures (7). A separator (4) is arranged between the positive electrode (3) and the negative electrode (2) to form the battery structure (7). The battery structures (7) are laminated in a bi-cell structure, then impregnated with a polymer electrolyte or a liquid electrolyte, and accommodated and sealed in a pouch to complete the pouch-shaped lithium secondary battery.

[0111] Specifically, the battery structure (7) including the above-described positive electrode (3), negative electrode (2), and separator (4) is simply laminated and accommodated in a pouch, or is wound or folded in a jelly roll shape and then accommodated in a pouch. Subsequently, a polymer electrolyte or liquid electrolyte is injected into the pouch and sealed, thereby completing the lithium secondary battery (1).

[0112] The case (5) may be made of metal such as aluminum, aluminum alloy, nickel-plated steel, or a laminate film or plastic that constitutes a pouch.

[0113] Lithium secondary batteries (1) have excellent lifespan and high-rate characteristics, making them suitable for use in electric vehicles (EVs). For example, they are used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). They are also used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0114] Lithium secondary batteries (1) are stacked in multiple layers to form a battery module, and the multiple battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. The battery module includes, for example, multiple batteries and a frame that holds them.

[0115] A battery pack includes, for example, multiple battery modules and bus bars connecting them. The battery modules and / or battery packs may further include a cooling device. The multiple battery packs are controlled by a battery management system. The battery management system includes the battery packs and a battery control device connected to the battery packs.

[0116]

[0117] positive electrode active material

[0118] Referring to FIGS. 1 to 4, the first positive electrode active material included in the first positive electrode mixture layer (120, 220, 320) or the second positive electrode active material included in the second positive electrode mixture layer (130, 230, 330) in the present invention may be a positive electrode active material to be described later. For example, the first positive electrode active material or the second positive electrode active material may include LiCoO2, LiMnO2, LiAlO2, LiTi2O4, LiV2O4, LiMn2O4, LFP, or a combination thereof. Depending on the choice of a person skilled in the art, the first positive electrode active material and the second positive electrode active material may be the same or different materials.

[0119] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used. The compound oxide may be a lithium transition metal compound oxide, and specific examples include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or combinations thereof.

[0120] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Lia Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

[0121] In the chemical formula, A is Ni, Co, Mn, or a combination thereof, X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, D is O, F, S, P, or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, and L 1 is Mn, Al or a combination thereof.

[0122] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in a lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0123] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 1:

[0124]

[0125] <Chemical Formula 1>

[0126] Li a Ni x Co y M z O 2-b A b

[0127]

[0128] In chemical formula 1, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0≤y≤0.3, 0 <z≤0.3, x+y+z=1, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다.

[0129] For example, in chemical formula 1, 0.7≤x<1, 0 <y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.2, 0<z≤0.2, 0.83≤x<0.97, 0<y≤0.15, 0<z≤0.15, 또는 0.85≤x<0.95, 0<y≤0.1, 0<z≤0.1일 수 있다.

[0130] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulae 2 and 3:

[0131]

[0132] <Chemical Formula 2>

[0133] LiNi x Co y Mn z O2

[0134]

[0135] In chemical formula 2, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다.

[0136]

[0137] <Chemical Formula 3>

[0138] LiNi x Co y Al z O2

[0139]

[0140] In chemical formula 3, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.8≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.82≤x≤0.95, 0<y≤0.15, 0<z≤0.15이다. 예를 들어, 0.85≤x≤0.95, 0<y≤0.1, 0<z≤0.1이다.

[0141] For example, lithium transition metal oxide is LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04O2 , LiNi 0.8 Co 0.15 Mn 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02O2 , LiNi 0.8 Co 0.15 Al 0.05O2 , LiNi 0.8 Co0.1 Mn 0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0142] For example, the cathode active material may be a lithium transition metal oxide having a coating layer on the surface, or a lithium transition metal oxide and a lithium transition metal oxide having a coating layer may be mixed and used.

[0143] For example, the coating layer may include a coating element compound of an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element.

[0144] For example, the compound forming the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as the coating elements are used on the lithium transition metal oxide and do not adversely affect the properties of the positive electrode active material (e.g., spray coating, dipping, etc.).

[0145] For example, the anode may further include an additive that can act as a sacrificial anode.

[0146] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and the conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0147] The binder helps the positive electrode active material particles adhere well to each other and also helps the positive electrode active material adhere well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0148] Conductive materials are used to provide conductivity to electrodes, and any material that does not cause chemical changes and is electronically conductive can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, and silver in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0149]

[0150] negative current collector

[0151] The negative electrode current collector may not include a negative electrode active material layer. In a negative electrode current collector not including a negative electrode active material layer, lithium metal may be plated on the negative electrode current collector by charging. The plated metal layer may include plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The metal layer may include non-fibrous lithium, non-acidic lithium, plate-like lithium, or any combination thereof. The lithium alloy contains lithium and a first metal, wherein the first metal may include indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0152] The material constituting the negative electrode current collector may be any material that does not react with lithium, that is, does not form an alloy or compound with lithium, and has conductivity. The metal substrate is, for example, a metal or an alloy. The metal substrate may be made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The electrode current collector may have a form selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a body containing through-holes, a polygonal ring body, a mesh body, a foam body, and a non-woven body, but is not necessarily limited to these forms, and any form used in the relevant technical field may be used.

[0153] The negative electrode current collector includes, for example, a first metal substrate. The first metal substrate includes, as a main component, the first metal, or is made of the first metal. The first metal substrate includes, as a main component, the first metal, or is made of the first metal. The content of the first metal included in the first metal substrate is, for example, 90 wt% or more, 95 wt% or more, 99 wt% or more, or 99.9 wt% or more, based on the total weight of the first metal substrate. The first metal substrate may be made of, for example, a material that does not react with lithium, i.e., does not form an alloy and / or compound with lithium.

[0154] The first metal may be, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited thereto, and any metal that can be used as a current collector in the relevant technical field may be used. The first metal substrate may be composed of, for example, one of the above-described metals, or may be composed of an alloy of two or more metals. The first metal substrate may be, for example, in the form of a sheet or foil.

[0155] The cathode current collector may further include a coating layer (not shown) containing a second metal on the first metal substrate.

[0156] The negative electrode current collector may include, for example, a first metal substrate and a coating layer disposed on the first metal substrate and including a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer including the second metal is harder than the substrate including the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the first metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The coating layer includes the second metal. The coating layer includes, for example, the second metal as a main component or is made of the second metal. The content of the second metal included in the coating layer is, for example, 90 wt% or more, 95 wt% or more, 99 wt% or more, or 99.9 wt% or more based on the total weight of the coating layer. The coating layer may be composed of, for example, a material that does not react with lithium, i.e., does not form an alloy and / or compound with lithium. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or less, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is excessively low, it may be difficult to suppress deterioration of the negative electrode current collector. If the Mohs hardness of the second metal is excessively high, processing may not be easy. The second metal is, for example, one or more selected from titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh).The coating layer may be composed of, for example, one of the above-described metals, or may be composed of an alloy of two or more metals. The difference in Mohs hardness between the first metal included in the first metal substrate and the second metal included in the coating layer may be, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. Since the first metal and the second metal have such a difference in Mohs hardness, deterioration of the negative electrode current collector can be more effectively suppressed. The coating layer may have a single-layer structure or a multi-layer structure of two or more layers. The coating layer may have a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may have a three-layer structure including, for example, a first coating layer, a second coating layer, and a third coating layer. The thickness of the coating layer may be, for example, 10 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. The coating layer may be formed on the first metal substrate by, for example, a vacuum deposition method, a sputtering method, a plating method, etc., but is not necessarily limited to these methods, and any method capable of forming a coating layer in the relevant technical field may be used.

[0157] For example, the negative electrode current collector may have a reduced thickness compared to conventional negative electrode current collectors. Therefore, the negative electrode according to the present disclosure is distinguished from conventional electrodes including thick film current collectors, for example, by including a thin film current collector.

[0158] As a result, the energy density of a lithium metal battery employing such an electrode is increased. The thickness of the negative electrode current collector may be, for example, less than 15 um, 14.5 um or less, or 14 um or less. The thickness of the negative electrode current collector may be, for example, 0.1 um to less than 15 um, 1 um to 14.5 um, 2 um to 14 um, 3 um to 14 um, 5 um to 14 um, or 10 um to 14 um.

[0159] The negative electrode current collector may have a form selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a body containing through holes, a polygonal ring body, a mesh body, a foam body, and a non-woven body, but is not necessarily limited to these forms, and any form used in the relevant technical field may be used.

[0160] The negative electrode current collector may include, for example, a base film and a metal substrate layer disposed on one or both surfaces of the base film. The negative electrode current collector may include a substrate, and the substrate may have a structure including, for example, a base film and a metal substrate layer disposed on one or both surfaces of the base film. An intermediate layer may additionally be disposed on the metal substrate layer.

[0161] For example, the base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Since the base film includes a thermoplastic polymer, the base film may melt when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may be, for example, an insulator.

[0162] The metal substrate layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The metal substrate layer may act as an electrochemical fuse, which may be cut off in the event of an overcurrent to prevent a short circuit. The limit current and maximum current may be controlled by adjusting the thickness of the metal substrate layer. The metal substrate layer may be plated or deposited on the base film. As the thickness of the metal substrate layer decreases, the limit current and / or maximum current of the negative electrode current collector may be reduced, thereby improving the stability of the lithium metal battery in the event of a short circuit.

[0163] A lead tab may be added to the metal substrate layer for external connection. The lead tab may be welded to the metal substrate layer or the metal substrate layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal substrate layer may be melted, so that the metal substrate layer may be electrically connected to the lead tab. To strengthen the welding between the metal substrate layer and the lead tab, a metal chip may be added between the metal substrate layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal substrate layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to the metal chip / metal substrate layer laminate or the metal chip / metal substrate layer / base film laminate by placing the metal chip on the metal substrate layer and then welding it with the lead tab. During welding, the base film, metal layer, and / or metal piece may melt, thereby electrically connecting the metal layer or the metal layer / metal piece laminate to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal substrate layer. The thickness of the base film may be, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. When the base film has a thickness in this range, the weight of the negative electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300 ℃, 100 to 250 ℃ or less, or 100 to 200 ℃. When the base film has a melting point in this range, the base film may melt during the welding of the lead tab, thereby easily bonding to the lead tab. A surface treatment, such as corona treatment, may be performed on the base film to improve the adhesion between the base film and the metal substrate layer. The thickness of the metal substrate layer is, for example, 0.The thickness of the metal substrate layer may be 0.1 to 3 ㎛, 0.1 to 3 ㎛, 0.1 to 2 ㎛, or 0.1 to 1 ㎛. By having a thickness in this range, the stability of the negative electrode can be secured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 ㎛, 2 to 7 ㎛, or 4 to 6 ㎛. By having a thickness in this range, the connection between the metal layer and the lead tab can be performed more easily. By having the negative electrode current collector with this structure, the weight of the electrode can be reduced, and as a result, the energy density can be improved.

[0164] In one embodiment, the negative electrode current collector may be free of a negative electrode active material layer prior to performing a charge / discharge cycle. For example, the negative electrode current collector may be free of a lithium metal layer prior to performing a charge / discharge cycle.

[0165] According to one embodiment, a lithium metal layer including a plate-shaped lithium metal thin film can be disposed on a negative electrode current collector before charge and discharge is performed.

[0166] According to one embodiment, the negative electrode may further include an interlayer disposed between the negative electrode current collector and the lithium metal layer.

[0167] In one embodiment, the interlayer may be directly disposed on, for example, one or both surfaces of the negative current collector. Accordingly, no other layer may be disposed between the negative current collector and the interlayer. By directly disposing the interlayer on one or both surfaces of the negative current collector, the bonding strength between the negative current collector and the lithium metal layer may be further enhanced.

[0168]

[0169] electrolyte

[0170] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0171] The electrolyte is, for example, an organic electrolyte. An organic electrolyte is prepared by dissolving a lithium salt in an organic solvent. Any organic solvent used in the relevant technical field can be used. Organic solvents include, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

[0172] Any lithium salt used in the relevant technical field is also possible. Lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI, or mixtures thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0173] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0174] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La xZr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a MaO 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0175] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x ("LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75An inorganic solid electrolyte prepared by adding S4 ("ThioLISICON"), Li2O-Al2O3-TiO2-P2O5 ("LATP"), etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiX (X=halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다.

[0176] Additionally, a calcination process may be performed after the above treatment. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0177] A polymer solid electrolyte is an electrolyte that includes, for example, a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. A polymer solid electrolyte is, for example, a polymer electrolyte that does not include a liquid electrolyte. Polymers included in the polymer solid electrolyte include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly, (ether ether ketone) (sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi+) or a combination thereof, but is not limited thereto, and any polymer electrolyte used in the art may be used. The lithium salt may be any lithium salt that can be used in the art. The lithium salt may be, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C, x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are each 1 to 20), LiCl, LiI or a mixture thereof.

[0178] A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is, for example, an electrolyte that includes a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte can be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer can be selected from among the polymers used in solid polymer electrolytes. The organic solvent can be selected from among the organic solvents used in liquid electrolytes. The lithium salt can be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature and is liquid at room temperature or a room temperature molten salt that is composed only of ions. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium and mixtures thereof, and b) BF4. - , PF6 - , AsF6 -, SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include at least one selected from compounds containing at least one anion selected from. A gel polymer electrolyte may be formed by impregnating a polymer solid electrolyte into an electrolyte solution in a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0179]

[0180] separator

[0181] A lithium secondary battery according to one embodiment may further include a separator (not shown).

[0182] As the separator, a multilayer film of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0183] The separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof, positioned on one or both sides of the porous substrate.

[0184] The porous substrate may be a polymer membrane formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0185] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0186] The inorganic material may include inorganic particles selected from, but not limited to, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0187] Organic and inorganic substances may be mixed and present in one coating layer, or a coating layer containing an organic substance and a coating layer containing an inorganic substance may be present in a laminated form.

[0188] The following examples and comparative examples are provided for further details. However, the examples are provided for illustrative purposes only and are not intended to be limiting.

[0189]

[0190] Example 1-1

[0191] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material volume ratio of 30% was applied onto the aluminum foil and then briefly dried. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material volume ratio of 10% was applied and then dried to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 2:8.

[0192]

[0193] Example 1-2

[0194] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material content of 10% by volume was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material content of 30% by volume was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 2:8.

[0195]

[0196] Example 1-3

[0197] Aluminum foil was prepared as a current collector. A first cathode mixture layer slurry having a sacrificial cathode active material volume ratio of 50% was applied onto the aluminum foil and then briefly dried. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture layer slurry was 4%. Thereafter, a second cathode mixture layer slurry having a sacrificial cathode active material volume ratio of 10% was applied and then dried to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture layer slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 2:8.

[0198]

[0199] Comparative Example 1

[0200] Aluminum foil was prepared as a current collector. A first cathode mixture layer slurry with a capacity ratio of 0% of the sacrificial cathode active material was applied onto the aluminum foil and then dried to produce a cathode. At this time, the weight ratio of the conductive material and binder in the first cathode mixture layer slurry was 4%.

[0201]

[0202] Classification 1 Anode composite layer 2 Anode composite layer Anode: Sacrificial anode Capacity ratio (%) Active material: Conductive material Binder weight ratio (wt%) Anode: Sacrificial anode Capacity ratio (%) Active material: Conductive material Binder weight ratio (wt%) Example 1-170:3096:490:1098:2 Example 1-290:1096:470:3098:2 Example 1-350:5096:490:1098:2 Comparative example 1100:096:4--

[0203] In Examples 1-1 to 1-3 of Table 1, the thickness ratio of the first positive electrode mixture layer and the second positive electrode mixture layer corresponds to 2:8. "Positive electrode: sacrificial positive electrode capacity ratio (%)" corresponds to the positive electrode active material discharge capacity: sacrificial positive electrode charge capacity.

[0204]

[0205] Example 2-1

[0206] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material content of 30% by volume was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material content of 10% by volume was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 3:7.

[0207]

[0208] Example 2-2

[0209] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material volume ratio of 30% was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material volume ratio of 10% was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 5:5.

[0210]

[0211] Example 2-3

[0212] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material volume ratio of 30% was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material volume ratio of 10% was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 7:3.

[0213]

[0214] Thickness ratio of the first anode composite layer (%) Thickness ratio of the second anode composite layer (%) Example 2-13070 Example 2-25050 Example 2-37030

[0215] In Table 2, the capacity ratio of the sacrificial cathode active material in the first cathode composite layer corresponds to 30%, and the weight ratio of the conductive material and binder corresponds to 4%. In the second cathode composite layer, the capacity ratio of the sacrificial cathode active material corresponds to 10%, and the weight ratio of the conductive material and binder corresponds to 2%.

[0216]

[0217] Example 3-1

[0218] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material volume ratio of 30% was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 2%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material volume ratio of 10% was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 3:7.

[0219]

[0220] Example 3-2

[0221] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material volume ratio of 30% was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 6%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material volume ratio of 10% was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 3:7.

[0222]

[0223]

[0224] Example 3-3

[0225] Aluminum foil was prepared as a current collector. A first cathode mixture slurry having a sacrificial cathode active material content of 30% by volume was applied onto the aluminum foil, followed by brief drying. At this time, the weight ratio of the conductive material and the binder in the first cathode mixture slurry was 4%. Thereafter, a second cathode mixture slurry having a sacrificial cathode active material content of 10% by volume was applied, followed by drying to manufacture a cathode. At this time, the weight ratio of the conductive material and the binder in the second cathode mixture slurry was 2%. In the completed cathode, the thickness ratio of the first cathode mixture layer and the second cathode mixture layer was 3:7.

[0226]

[0227] Classification 1 Anode composite layer 2 Anode composite layer Anode: Sacrificial anode Capacity ratio (%) Active material: Conductive material Binder weight ratio (wt%) Anode: Sacrificial anode Capacity ratio (%) Active material: Conductive material Binder weight ratio (wt%) Example 3-170:3098:290:1098:2 Example 3-270:3094:690:1098:2 Example 3-370:3096:490:1098:2

[0228] In Table 3, the thickness ratio of the first positive electrode composite layer and the second positive electrode composite layer corresponds to 3:7.

[0229]

[0230] Evaluation Example 1: Measurement of DC-IR resistance (mΩ) of a lithium secondary battery

[0231] The lithium secondary batteries manufactured according to Examples 1-1 to 3-3 and Comparative Example 1 were charged at a current of 0.1C rate to undergo a formation process, and then fully charged at a current of 0.2C rate (SOC 100%). For the discharge process, first, the batteries were discharged at a current of 3C rate for 10 seconds, then at a current of 0.2C rate for 10 seconds, and then at a current of 3C rate for 10 seconds. Finally, the batteries were completely discharged at a 0.2C rate, and then the DC-IR was calculated from the voltage drop (IR Drop) that occurred when a current of 3C rate was applied. The results are shown in the table below.

[0232]

[0233] Evaluation Example 2: Measurement of capacity retention rate (%, @100cy) of lithium secondary batteries

[0234] The lithium secondary batteries manufactured according to Examples 1-1 to 3-3 and Comparative Example 1 were charged at a current of 0.1 C rate and the formation process was performed. Thereafter, the secondary battery cells were charged at a constant current of 0.33 C rate until the voltage reached 4.5 V (vs. Li) in the charging process, and the cut-off was performed at a current of 0.05 C rate while maintaining a constant voltage of 4.5 V in the constant voltage mode. Subsequently, a constant current discharge at 1.0 C rate was performed until the voltage reached 3.0 V (vs. Li) during discharge. The above-described charge and discharge processes were repeated a total of 100 times. In all charge and discharge cycles, a pause time of 5 minutes was provided after one charge / discharge cycle. Here, the capacity retention rate in the Nth cycle is defined by the following equation.

[0235] [ceremony]

[0236] Capacity retention rate (%) = (discharge capacity at Nth cycle / 1) stDischarge capacity in cycle)*100

[0237] The capacity retention rate at the 100th cycle for each is shown in the table below.

[0238]

[0239] Classification DC-IR (mΩ) Capacity Retention (%, @100cy) Example 1-1 13.49 3.8 Example 1-2 14.79 1.0 Example 1-3 14.49 2.2 Comparative Example 18.73 2.4

[0240] Classification DC-IR (mΩ) Capacity Retention (%, @100cy) Example 2-1 13.5 9 3.6 Example 2-2 14.9 9 0.4 Example 2-3 15.7 8.2

[0241] Classification DC-IR (mΩ) Capacity Retention (%, @100cy) Example 3-1 14.5 9 0.9 Example 3-2 17.2 8 6.2 Example 3-3 15.2 8 8.1

[0242]

[0243] Referring to Table 4, Examples 1-1 to 1-3 each had lower resistance and better lifespan characteristics than Comparative Example 1.

[0244] Referring to Table 5, Examples 2-1 to 2-3 each had lower resistance and better lifespan characteristics than Comparative Example 1.

[0245] Referring to Table 6, Examples 3-1 to 3-3 each had lower resistance and better lifespan characteristics than Comparative Example 1.

[0246] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

positive current collector; A first positive electrode composite layer disposed on the positive electrode current collector; and A second positive electrode composite layer is disposed on the first positive electrode composite layer, The capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode composite layer is different from the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode composite layer. Cathode for lithium secondary batteries. In the first paragraph, The capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode composite layer is greater than the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode composite layer. Cathode for lithium secondary batteries. In the first paragraph, A positive electrode for a lithium secondary battery, wherein the capacity occupied by the sacrificial positive electrode active material in the first positive electrode composite layer is 5% to 60% of the total capacity of the first positive electrode composite layer. In the first paragraph, A positive electrode for a lithium secondary battery, wherein the capacity occupied by the sacrificial positive electrode active material in the second positive electrode composite layer is 1% to 50% of the total capacity of the second positive electrode composite layer. In the first paragraph, The first positive electrode composite layer includes a first positive electrode active material including a conductive material, a binder, and the sacrificial positive electrode active material, A positive electrode for a lithium secondary battery, wherein the first positive electrode active material is included in a range of 95 wt% to 98 wt% of the total weight of the first positive electrode composite layer. In the first paragraph, The second positive electrode composite layer includes a second positive electrode active material including a conductive material, a binder, and the sacrificial positive electrode active material, A positive electrode for a lithium secondary battery, wherein the second positive electrode active material is included in a range of 98 wt% to 99 wt% of the total weight of the second positive electrode composite layer. In the first paragraph, A positive electrode for a lithium secondary battery, wherein the weight ratio of the first positive electrode active material in the first positive electrode mixture layer is equal to or smaller than the weight ratio of the second positive electrode active material in the second positive electrode mixture layer. In the first paragraph, A positive electrode for a lithium secondary battery, wherein the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer have a ratio of 1:9 to 9:

1. In the first paragraph, A cathode for a lithium secondary battery, wherein the sacrificial cathode active material comprises Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P or any combination thereof. In paragraph 7, A positive electrode for a lithium secondary battery, wherein the first positive electrode active material or the second positive electrode active material comprises LiMO2 (M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof). Anode for a lithium secondary battery according to Article 1; A cathode comprising a cathode current collector; and A lithium secondary battery comprising an electrolyte disposed between the positive electrode and the negative electrode. In Article 11, A lithium secondary battery, wherein the negative electrode current collector includes a foil structure layer containing copper (Cu). In Article 11, A lithium secondary battery in which the negative electrode is free of a negative electrode active material layer before charging. In Article 11, The above lithium secondary battery is a lithium secondary battery in which a lithium metal layer is formed on the negative electrode current collector after charging and discharging. A step of placing a first positive electrode composite layer on a positive electrode current collector; and A step of placing a second positive electrode mixture layer on the first positive electrode mixture layer. Including, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the capacity ratio occupied by the sacrificial positive electrode active material of the first positive electrode mixture layer is different from the capacity ratio occupied by the sacrificial positive electrode active material of the second positive electrode mixture layer. In Article 15, A method for manufacturing a positive electrode for a lithium secondary battery, further comprising a step of vacuum drying the first positive electrode mixture layer and the second positive electrode mixture layer. In Article 15, A method for manufacturing a positive electrode for a lithium secondary battery, further comprising a step of rolling the first positive electrode mixture layer and the second positive electrode mixture layer. In Article 15, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the capacity ratio occupied by the sacrificial positive electrode active material in the first positive electrode mixture layer is greater than the capacity ratio occupied by the sacrificial positive electrode active material in the second positive electrode mixture layer. In Article 15, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the weight ratio of the first positive electrode active material in the first positive electrode mixture layer is smaller than the weight ratio of the second positive electrode active material in the second positive electrode mixture layer. In Article 15, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer have a ratio of 1:9 to 9:1.

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