Anode and lithium secondary battery comprising same

Abstract

An anode and a lithium secondary battery comprising same are presented, the anode comprising: an anode current collector; and a protective layer disposed on the anode current collector and including a cross-linked polymer including a repeating unit derived from two or more types of multi-functional cross-linking agents, wherein the cross-linked polymer has a cross-linking density (g / n) of 300 or less.

Description

Anode and lithium secondary battery containing the same

[0001] The present invention relates to a negative electrode including a protective layer and a lithium secondary battery including the same.

[0002] In a lithium battery employing a cathode containing lithium metal or a non-cathode containing no cathode active material, a protective layer is applied to prevent dendrite formation and ensure uniform ion flux when dendrites are formed.

[0003] Protective layers can be polymeric, inorganic, or organic / inorganic composite. Most protective layers require a thickness of at least 10 μm to ensure sufficient ionic conductivity. However, thicker protective layers often lead to lower current densities in lithium batteries employing them.

[0004] To solve these problems, a hybrid binder of polyimide and polyvinyl alcohol was applied to the protective layer, but it was not easy to form a stable SEI during the initial deposition.

[0005] Therefore, in a lithium battery employing a cathode including lithium metal or a cathode without a cathode active material, a protective layer capable of suppressing volume change of the electrode and a binder forming the protective layer are required, which provide high initial efficiency and life characteristics, and improved electrode stability.

[0006] One aspect is to provide a cathode having improved initial capacity, life characteristics and electrode stability, and including a protective layer with improved ionic conductivity while suppressing volume change of the electrode.

[0007] Another aspect is to provide a lithium secondary battery employing the above negative electrode.

[0008] According to one implementation example,

[0009] negative current collector; and

[0010] A protective layer is disposed on the negative electrode current collector and includes a crosslinked polymer including repeating units derived from one or more polyfunctional crosslinking agents,

[0011] A cathode is provided in which the crosslinking density (g / n) of the crosslinked polymer is 300 or less.

[0012] According to another implementation example,

[0013] A lithium secondary battery is provided, comprising: a positive electrode; the negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode.

[0014] According to one aspect, when the crosslinking density (g / n) of the crosslinked polymer included in the protective layer satisfies 300 or less, not only the mechanical properties of the protective layer are improved, but also the ionic conductivity can be improved. Accordingly, the negative electrode and lithium secondary battery including the protective layer can have improved high-temperature life characteristics.

[0015] Figure 1 is a cross-sectional view of a cathode according to an exemplary embodiment.

[0016] Figure 2 is a cross-sectional view of a cathode according to another exemplary embodiment.

[0017] Figure 3 is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.

[0018] Figure 4 is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.

[0019] Figure 5 is a schematic diagram of a lithium secondary battery according to an exemplary embodiment.

[0020] Figure 6 is a graph showing the results of measuring the capacity retention rate of lithium batteries according to examples and comparative examples.

[0021] The present inventive concept described below is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, but rather to encompass all modifications, equivalents, or alternatives within the technical scope of the present inventive concept.

[0022] The terminology used below 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. Hereinafter, the terms "comprises" or "has" and the like 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. The " / " used below may be interpreted as "and" or "or" depending on the context.

[0023] In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is said to be "on" or "above" another part throughout the specification, this includes not only cases where it is directly above the other part, but also cases where there is another part in between. Terms such as first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In this specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

[0024] 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.

[0025] 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."

[0026] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0027] 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.

[0028] In the present disclosure, the "particle diameter" of a particle refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter of a particle can be measured using a particle size analyzer (PSA). The "particle diameter" of a particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the size of a particle corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, laser diffraction. The average particle diameter and average major axis length of a particle can be measured using a scanning electron microscope. When the particle size is measured using a scanning electron microscope, it is determined as the average value of 30 or more randomly selected particles having a size of 1 μm or more, excluding fine particles.

[0029] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states, and “alloy” means a mixture of two or more metals.

[0030] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0031] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0032] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0033] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0034] Hereinafter, a negative electrode including a protective layer according to exemplary embodiments and a lithium secondary battery including the same will be described in more detail.

[0035] As used herein, "cross-link" means a bond that connects one polymer chain to another polymer chain. As used herein, a cross-link is a covalent bond. As used herein, a "linker" or "cross-linker" means a functional group that connects one polymer chain to another polymer chain. As used herein, a "cross-linked polymer" means a polymer in which one polymer chain and another polymer chain are connected by one or more linkers. Furthermore, a cross-linked polymer is a product of a cross-linking reaction of one or more polymers.

[0036] [cathode]

[0037] According to one embodiment, a negative electrode (20) includes a negative electrode current collector (21); and a protective layer (24) disposed on the negative electrode current collector (21), wherein the protective layer (24) includes a crosslinked polymer including repeating units derived from at least one polyfunctional crosslinking agent, and a crosslinking density (g / n) of the crosslinked polymer may be 300 or less. For example, the negative electrode (20) of the present invention includes a crosslinked polymer including repeating units derived from at least one polyfunctional crosslinking agent, and the crosslinking density (g / n) of the crosslinked polymer satisfies 300 or less, so that mechanical properties are excellent and ionic conductivity can be improved at the same time.

[0038] For example, the crosslinking density (g / n) of the crosslinked polymer may mean a value obtained by dividing the molecular weight of the crosslinked polymer by the number of functional groups. For example, the molecular weight of the crosslinked polymer is the molecular weight of the repeating unit included in the crosslinked polymer, and the number of functional groups is the number of crosslinkable points included in the repeating unit of the crosslinked polymer, for example, the number of functional groups such as acrylate groups.

[0039] According to one embodiment, the crosslinking density (g / n) of the crosslinked polymer may be 100 to 300 or 150 to 280.

[0040] [Protective layer]

[0041] According to one embodiment, the ionic conductivity of the protective layer (24) may be 0.01 mS / cm or more at 25°C. For example, the protective layer (24) may have excellent ionic conductivity while satisfying excellent mechanical properties. For example, the ionic conductivity of the protective layer (24) may be 0.03 mS / cm or more or 0.05 mS / cm or more at 25°C.

[0042] For example, the crosslinked polymer included in the protective layer (24) may include repeating units (A) derived from an ester monomer; or repeating units (B) derived from an alkylene oxide monomer. For example, the crosslinked polymer may include repeating units (A) derived from an ester monomer; and repeating units (B) derived from an alkylene oxide monomer.

[0043] For example, when the crosslinked polymer included in the protective layer (24) includes a repeating unit (A) derived from an ester-based monomer, the physical properties of the protective layer (24) can be improved. In addition, when the crosslinked polymer included in the protective layer (24) includes a repeating unit (B) derived from an alkylene oxide-based monomer, the ionic conductivity of the protective layer (24) can be improved.

[0044] According to one embodiment, the ratio of the mole number of the repeating unit (A) derived from the ester monomer to the mole number of the repeating unit (B) derived from the alkylene oxide monomer in the crosslinked polymer may be 1 to 20. For example, when the ratio of the mole number of the repeating unit (A) derived from the ester monomer to the mole number of the repeating unit (B) derived from the alkylene oxide monomer satisfies the above range, the ionic conductivity of the polymer electrolyte (300) increases, and the initial overpotential value decreases, so that the formation of lithium dendrites can be suppressed. Accordingly, the life characteristics and efficiency characteristics of the lithium secondary battery including the protective layer (24) can be improved.

[0045] For example, the ratio of the mole number of repeating units (A) derived from the ester monomer to the mole number of repeating units (B) derived from the alkylene oxide monomer in the crosslinked polymer may be 1 to 10, 1 to 5, 2 to 20, 2 to 10, or 2 to 5.

[0046] According to one embodiment, the alkylene oxide monomer may include a unit represented by the following chemical formula 1. For example, the alkylene oxide monomer may be an ethylene oxide monomer.

[0047] <Chemical Formula 1>

[0048]

[0049] In the above chemical formula 1,

[0050] L1 is an alkylene group having 2 to 5 carbon atoms, and * is a bonding site with a neighboring atom.

[0051] For example, in the above chemical formula 1, L1 may be a methylene group, an ethylene group, an isopropylene group, a propylene group, a butylene group, a pentylene group, or a hexylene group.

[0052] For example, in the above chemical formula 1, L1 may be a methylene group, an ethylene group, or an isopropylene group.

[0053] According to one embodiment, the alkylene oxide monomer may include glyceryl propoxy triacrylate, glyceryl ethoxy triacrylate, tri-propoxylated glycerol triacrylate, tetra-propoxylated glycerol triacrylate, polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, or any combination thereof.

[0054] According to one embodiment, the alkylene oxide monomer may include glyceryl propoxy triacrylate, polyethylene glycol diacrylate, or a combination thereof.

[0055] According to one embodiment, the ester monomer may include a unit represented by the following chemical formula 2.

[0056] <Chemical Formula 2>

[0057]

[0058] In the above chemical formula 2,

[0059] * is a bonding site with a neighboring atom.

[0060] According to one embodiment, the ester monomer may include pentaerythritol triacrylate, pentaerythritol tetracrylate, dipentaerythritol hexacrylate, butyl acrylate, methyl metacrylate, trimethylolpropane triacrylate, or any combination thereof.

[0061] According to one embodiment, the ester monomer may include dipentaerythritol hexacrylate.

[0062] According to one embodiment, the alkylene oxide monomer may have at least one crosslinking point, and the ester monomer may have at least three crosslinking points. For example, the crosslinking point may be an unsaturated group at which a polymerization reaction is performed. For example, the crosslinking point may include an acrylate group. For example, the number of crosslinking points of the alkylene oxide monomer may be less than the number of crosslinking points of the ester monomer.

[0063] For example, the alkylene oxide monomer may have two or more crosslinking points, and the ester monomer may have four or more crosslinking points. The alkylene oxide monomer may have two crosslinking points, and the ester monomer may have six crosslinking points.

[0064] According to one embodiment, the difference in the number of crosslinking points between the ester monomer and the alkylene oxide monomer may be 2 to 6. For example, the difference in the number of crosslinking points between the ester monomer and the alkylene oxide monomer may be 3 to 5.

[0065] According to one embodiment, the protective layer (24) may further include a lithium salt, an inorganic oxide, or a linear polymer.

[0066] According to one embodiment, the lithium salt is 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)(1≤x≤20, 1≤y≤20), LiCl, LiI, lithium difluoro(oxalato)borate (LiDFOB) or a mixture thereof.

[0067] According to one embodiment, it may include lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0068] According to one embodiment, the mixing weight ratio of lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4) may be 1:2 to 1:0.3.

[0069] According to one embodiment, the inorganic oxide may include MgO, AlMgO, Al2O3, Nb2O5, TiO2, SiO2, ZrO2, SnO2, ZnO, Co3O4, HfO2, VO, NiO, Bi2O3, Ta2O5, GeO2, Ga2O3, In2O3, or any combination thereof.

[0070] According to one embodiment, the linear polymer is vinyl acetate, vinyl alcohol, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, It may include a polymerization reaction product of one or more monomers selected from among 3-isocyanatopropyl (meth)acrylate, 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylenedi(meth)acrylate, diethyleneglycol(meth)acrylate, triethyleneglycoldi(meth)acrylate, trimethylenepropanetri(meth)acrylate, trimethylenepropanetriacrylate, 1,3-butanediol(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof.

[0071] According to one embodiment, the protective layer (24) may further include a conductive material.

[0072] The conductive material may include, but is not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used.

[0073] According to one embodiment, the thickness of the protective layer (24) may be 5 μm or less. The thickness of the protective layer (24) may be, for example, 0.1 μm to 5 μm, 0.1 μm to 3 μm, 0.1 μm to 2 μm, 0.1 μm to 1.5 μm, 0.1 μm to 1.2 μm, 0.1 μm to 1.2 μm, or 0.2 to 1 μm. When the protective layer (24) has a thickness in this range, the decomposition of the electrolyte can be effectively suppressed and the imbalance of local current density can be effectively prevented, thereby effectively preventing the generation and / or growth of lithium dendrites. Accordingly, the cycle characteristics of the lithium battery including the protective layer (24) can be further improved. If the thickness of the protective layer (24) is excessively increased, the energy density of the lithium metal battery may be reduced. If the thickness of the protective layer (24) is excessively decreased, the improvement in the cycle characteristics of the lithium metal battery may be minimal.

[0074] According to one embodiment, the modulus of the protective layer (24) may be 30 MPa or more. For example, the modulus of the protective layer (24) may be 50 MPa or more, 70 MPa or more, 100 MPa or more, 500 MPa or more, 100 MPa to 2000 MPa, 100 MPa to 1500 MPa, or 100 MPa to 1000 MPa.

[0075] According to one embodiment, the recovery rate of the protective layer (24) may be 50% or more. For example, the recovery rate of the protective layer (24) may be 55% or more. For example, the recovery rate of the protective layer (24) may be 60% or more. For example, the recovery rate of the protective layer (24) may be 63% or more. For example, the recovery rate of the protective layer (24) may be measured using a micro-indenter. For example, the recovery rate of the protective layer (24) means the degree to which the protective layer (24) returns after being pressed with a certain force.

[0076] According to one implementation example, the hardness of the protective layer (24) is 10 N / mm 2 It may be ideal. For example, the hardness of the protective layer (24) is 12 N / mm 2 It may be ideal. For example, the hardness of the protective layer (24) is 15 N / mm 2 It may be ideal. For example, the hardness of the protective layer (24) is 20 N / mm 2 It may be ideal. For example, the hardness of the protective layer (24) is 40 N / mm 2 It may be ideal. For example, the hardness of the protective layer (24) is 50 N / mm 2 It could be strange.

[0077] [Cathode: Negative current collector]

[0078] Referring to FIGS. 1 and 2, the negative electrode (20) includes a negative electrode collector (21).

[0079] The negative electrode current collector (21) includes, 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.

[0080] The negative electrode current collector (21) 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 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 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 first metal includes, 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 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 is, for example, in the form of a sheet or foil. The thickness of the negative electrode current collector (21) may be, for example, 5 μm to 50 μm, 10 μm to 50 μm, 10 μm to 40 μm, or 10 μm to 30 μm, but is not necessarily limited to this range and may be selected depending on the characteristics of the required lithium battery.

[0081] The negative electrode current collector (21) may include, for example, a first metal substrate; and a coating layer (not shown) 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. If the thickness of the coating layer is too thin, it may be difficult to suppress the uneven growth of the lithium-containing metal layer. As the thickness of the coating layer increases, the cycle characteristics of the lithium battery improve. However, if the thickness of the coating layer is too thick, the energy density of the lithium battery decreases and the formation of the coating layer may not be easy. 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.

[0082] The negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The metal layer may include, 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. Since the positive electrode current collector has such a structure, the weight of the electrode can be reduced, and consequently, the energy density of the all-solid-state secondary battery can be improved.

[0083] [Cathode: Anode interlayer]

[0084] Referring to FIG. 1, the negative electrode (20) may include an anode interlayer (22) disposed between the negative electrode current collector (21) and the protective layer (24). Since the negative electrode (20) includes the anode interlayer (22), the generation and / or growth of lithium dendrites in the negative electrode (20) can be more effectively suppressed.

[0085] The negative electrode intermediate layer (22) may include, for example, a lithium-affinity metal. The negative electrode intermediate layer (22) may include, for example, a lithium-affinity metal and a carbon material.

[0086] The above lithium-compatible metal is a material that can be lithiated and delithiated. The negative electrode intermediate layer (22) can be formed by introducing the lithium-compatible metal onto the negative electrode current collector (21) through nanoparticle casting. When the negative electrode intermediate layer (22) is introduced onto the negative electrode current collector (21) through nanoparticle casting, lithium ions can penetrate the negative electrode intermediate layer (22), so that lithium metal can be formed between the negative electrode intermediate layer (22) and the negative electrode current collector (21).

[0087] The lithium-affinity metal included in the negative electrode intermediate layer (22) may be nanoparticles of the lithium-affinity metal. The average particle diameter of the lithium-affinity metal may be, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. Since the lithium-affinity metal has an average particle diameter in this range, reversible plating and / or dissolution of lithium may be facilitated during charge and discharge. In addition, since the lithium-affinity metal has a nano-sized size, lithium ions may penetrate the negative electrode intermediate layer (22) including the lithium-affinity metal, so that lithium metal may be precipitated between the negative electrode current collector (21) and the negative electrode intermediate layer (21). The average particle diameter of the above lithium-affinity metal is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0088] The lithium-affinity metal may include, for example, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The lithium-affinity metal may include, for example, silver (Ag).

[0089] The carbon material can uniformly coat the lithium-affinity metal on the negative electrode current collector (21). The carbon material can uniformly coat the lithium-affinity metal on the negative electrode current collector (21) by uniformly applying the lithium-affinity metal on the negative electrode current collector (21). The uniformly coated first particles can uniformly precipitate lithium metal on the negative electrode current collector (21) to prevent the formation of lithium dendrites.

[0090] The carbon material may include, for example, amorphous carbon, crystalline carbon, or any combination thereof. The carbon material may include, for example, amorphous carbon.

[0091] The amorphous carbon may include, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or any combination thereof. The amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon.

[0092] The negative electrode intermediate layer (22) may include, for example, a lithium-affinity metal and / or a carbon material, and uniformly apply the lithium-affinity metal onto the negative electrode current collector (21) through the carbon material, and the lithium-affinity metal may uniformly deposit lithium metal between the negative electrode intermediate layer (22) and the negative electrode current collector (21). Accordingly, the formation of lithium dendrites may be suppressed, and the life characteristics of a lithium battery including the negative electrode (20) may be improved. In addition, the negative electrode intermediate layer (22) may firmly attach the lithium metal to the protective layer (24) described below, thereby preventing deformation and perforation of the protective layer (24) due to uneven deposition of lithium metal.

[0093] The mixing ratio of the lithium-affinity metal and the carbon material included in the negative electrode intermediate layer (22) may be, for example, 10:1 to 1:10, 10:1 to 1:1, 10:1 to 2:1, 5:1 to 1:1, or 5:1 to 2:1 in weight ratio.

[0094] The negative electrode intermediate layer (22) may further include a binder. The binder included in the negative electrode intermediate layer (22) may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the art may be used. The binder may be composed of a single binder or a plurality of different binders. When the negative electrode intermediate layer (22) does not include a binder, the negative electrode intermediate layer (22) can be easily separated from the protective layer (24) or the negative electrode current collector (21). The content of the binder included in the negative electrode intermediate layer (22) may be, for example, 5 wt% or less, 0.1 to 5 wt%, 0.1 to 3 wt%, or 0.1 to 1 wt% relative to the total weight of the negative electrode (22) intermediate layer.

[0095] The thickness of the negative electrode intermediate layer may be, for example, 0.1 ㎛ to 5 ㎛, 0.1 ㎛ to 3 ㎛, or 0.5 ㎛ to 5 ㎛, 0.5 ㎛ to 3 ㎛, or 0.5 ㎛ to 2 ㎛. If the thickness of the negative electrode intermediate layer is too thin, lithium dendrites formed between the negative electrode intermediate layer and the negative electrode current collector may cause the negative electrode intermediate layer to collapse, making it difficult to improve the cycle characteristics of the lithium battery. If the thickness of the negative electrode intermediate layer increases excessively, the energy density of the lithium battery employing the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics. If the thickness of the negative electrode intermediate layer decreases, for example, the charge capacity of the negative electrode intermediate layer also decreases.

[0096] The charge capacity of the negative electrode intermediate layer may be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the charge capacity. If the charge capacity of the negative electrode intermediate layer is too small, lithium dendrites formed between the negative electrode intermediate layer and the negative electrode current collector may collapse the negative electrode intermediate layer, making it difficult to improve the cycle characteristics of the lithium battery. If the charge capacity of the negative electrode intermediate layer increases excessively, the energy density of the lithium battery using the negative electrode (20) may decrease and it may be difficult to improve the cycle characteristics. The charge capacity of the positive electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer. When multiple types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charge capacity of the positive electrode active material layer. The charge capacity of the negative electrode intermediate layer is also calculated in the same way. That is, the charge capacity of the negative electrode intermediate layer is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode intermediate layer. When multiple types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the negative electrode intermediate layer. Here, the charge capacity density of the positive electrode active material and the negative electrode active material is the capacity estimated using an all-solid-state half-cell using lithium metal as a counter electrode. The charge capacity of the positive electrode active material layer and the negative electrode intermediate layer is directly measured by measuring the charge capacity using an all-solid-state half-cell. The charge capacity density is obtained by dividing the measured charge capacity by the mass of each active material. Alternatively, the charge capacity of the positive electrode active material layer and the negative electrode intermediate layer may be the initial charge capacity measured at the time of the 1st charge cycle.

[0097] [Cathode: Cathode active material layer]

[0098] Referring to FIG. 2, the negative electrode (20) further includes a negative electrode active material layer (23) disposed between the negative electrode current collector (21) and the protective layer (22). The negative electrode active material layer (23) may include, for example, lithium metal or a lithium alloy.

[0099] The negative electrode active material layer (23) may include, for example, lithium foil, lithium powder, plated lithium, a carbon-based material, or a combination thereof. The negative electrode active material layer including lithium foil may be, for example, a lithium metal layer. The negative electrode active material layer including lithium powder may be introduced by coating a slurry including lithium powder and a binder, etc., on a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer may be formed of a metal-based negative electrode active material. The negative electrode active material layer (23) may also be a plated lithium metal layer. After manufacturing a lithium battery by assembling a negative electrode (20), a positive electrode, and an electrolyte that do not include a negative electrode active material layer (22), a lithium metal layer deposited between a negative electrode current collector (21) and a protective layer (22) by charging may be further included as a negative electrode active material layer (23).

[0100] The thickness of the negative electrode active material layer (23) 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 depending on the shape, capacity, etc. of the required lithium metal battery. If the thickness of the negative electrode active material layer (23) increases excessively, the structural stability of the lithium metal battery may deteriorate and side reactions may increase. If the thickness of the negative electrode active material layer (22) is excessively small, the energy density of the lithium metal battery may decrease. The thickness of the lithium foil may be, for example, 1 ㎛ to 50 ㎛, 1 ㎛ to 30 ㎛, or 10 ㎛ to 30 ㎛, or 10 ㎛ to 80 ㎛. When the lithium foil has a thickness in this range, the life characteristics of the lithium battery including the protective layer can be further improved. The particle size of the lithium powder may be, for example, 0.1 ㎛ to 3 ㎛, 0.1 ㎛ to 2 ㎛, or 0.1 ㎛ to 2 ㎛. When the lithium powder has a thickness in this range, the life characteristics of the lithium battery including the protective layer may be further improved. The thickness of the lithium precipitation layer may be, for example, 1 ㎛ to 80 ㎛, or 10 ㎛ to 80 ㎛.

[0101] [Lithium battery]

[0102] A lithium battery according to one embodiment includes a positive electrode; the above-described negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode. By including the above-described negative electrode, the lithium battery can simultaneously provide improved capacity and excellent lifespan characteristics.

[0103] Lithium batteries may be, but are not limited to, lithium primary batteries, lithium secondary batteries, lithium-sulfur batteries, lithium-air batteries, etc., and any lithium battery used in the relevant technical field may be used.

[0104] Lithium batteries are manufactured by, for example, the following exemplary methods, but are not necessarily limited to these methods and are adjusted according to required conditions.

[0105] (cathode)

[0106] Prepare the cathode described above.

[0107] (anode)

[0108] First, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent. The prepared positive electrode active material composition is directly coated and dried on an aluminum current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on the aluminum current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon.

[0109] The cathode active material is a lithium-containing metal oxide, and any one commonly used in the art can be used without limitation. For example, one or more types of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used, and specific examples thereof include Li a A 1-b B b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Cob B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG bO2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) A compound represented by any one of the chemical formulas Fe2(PO4)3(0 ≤ f ≤ 2); LiFePO4 can be used.

[0110] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B 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; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0111] The cathode active material is, for example, Li a Ni x Co y M z O 2-b A b(1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0 <y≤0.3, 0<z≤0.3, 및 x+y+z=1이고, M은 망간(Mn), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), LiNi x Co y Mn z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Al z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Mn z Al w O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1), Li a Co x M y O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), Li a Ni x Mn y M' z O 2-b A b(1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고, M'는 코발트(Co), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), Li a M1 x M2 y PO 4-b X b (In the above chemical formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며, M1이 크롬(Cr), 망간(Mn), 철(Fe), 코발트(Co), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 또는 이들의 조합이며, M2가 마그네슘(Mg), 칼슘(Ca), 스트론튬(Sr), 바륨(Ba), 티탄(Ti), 아연(Zn), 보론(B), 니오븀(Nb), 갈륨(Ga), 인듐(In), 몰리브덴(Mo), 텅스텐(W), 알루미늄(Al), 실리콘(Si), 크롬(Cr), 바나듐(V), 스칸듐(Sc), 이트륨(Y) 또는 이들의 조합이며, X가 O, F, S, P 또는 이들의 조합), Li a M3 z PO4 (0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof).

[0112] Conductive materials include, but are not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used. Alternatively, the anode may not include a separate conductive material, for example.

[0113] As the binder, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above polymers, styrene butadiene rubber polymer, etc. are used, and as the solvent, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not necessarily limited to these, and any solvent used in the relevant technical field may be used.

[0114] It is also possible to form pores inside the electrode plate by further adding a plasticizer or a pore forming agent to the positive electrode active material composition.

[0115] The contents of the cathode active material, conductive agent, binder, and solvent used in the cathode are at levels typically used in lithium batteries. Depending on the intended use and configuration of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

[0116] The binder content included in the positive electrode may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer. The positive electrode active material content included in the positive electrode may be 80 wt% to 99 wt%, 90 wt% to 99 wt% or 95 wt% to 99 wt% of the total weight of the positive electrode active material layer.

[0117] (Separator)

[0118] Next, a separator to be inserted between the positive and negative electrodes is prepared.

[0119] Any separator commonly used in lithium batteries can be used. For example, a separator with low resistance to ion migration and excellent electrolyte absorption capacity is used. The separator may be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a nonwoven or woven fabric. For lithium-ion batteries, a rollable separator, such as polyethylene or polypropylene, is used, while for lithium-ion polymer batteries, a separator with excellent organic electrolyte absorption capacity is used.

[0120] The separator is manufactured by the following exemplary methods, but is not limited to these methods and may be adjusted according to required conditions.

[0121] First, a separator composition is prepared by mixing a polymer resin, a filler, and a solvent. The separator composition is directly coated and dried on the electrode to form a separator. Alternatively, the separator composition is cast on a support and dried, and then a separator film peeled from the support is laminated on the electrode to form a separator.

[0122] The polymer used in separator manufacturing is not particularly limited; any polymer used as a binder for electrode plates can be used. Examples include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof.

[0123] (electrolyte)

[0124] Next, the electrolyte is prepared.

[0125] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, or a combination thereof.

[0126] The electrolyte is, for example, an organic electrolyte. An organic electrolyte is prepared by dissolving a lithium salt in an organic solvent, for example.

[0127] Any organic solvent used in the relevant technical field may be used. Examples of the organic solvent include 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.

[0128] Lithium salts are all possible if they are used as lithium salts in the relevant technical field. Lithium salts include, 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)(1≤x≤20, 1≤y≤20), LiCl, LiI or a mixture thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0129] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof.

[0130] 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 x Zr 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 M a O 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).

[0131] 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 0.75 S4("Thio-LISICON"), Li2O-Al2O3-TiO2-P2O 5( An inorganic solid electrolyte prepared by adding "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-Z m S n(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. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0132] (lithium battery)

[0133] Referring to FIG. 3, a lithium battery (1) according to an 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 or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6), thereby completing the lithium battery (1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0134] Referring to FIG. 4, a lithium battery (1) according to one embodiment includes a positive electrode (3), the aforementioned 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 battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed to complete the lithium battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc.

[0135] Referring to FIG. 5, a lithium battery (1) according to an embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2) to form a battery structure. A battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding a current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed to complete the lithium battery (1). The battery case (5) is not necessarily limited to a square shape, and may be, for example, a cylindrical shape, a thin film shape, etc.

[0136] A pouch-type lithium battery corresponds to the lithium batteries of FIGS. 3 to 5, each of which uses a pouch as a battery case. The pouch-type lithium battery includes one or more battery structures. A separator is disposed between a positive electrode and a negative electrode to form a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with an organic electrolyte, and accommodated and sealed in a pouch to complete the pouch-type lithium battery. For example, although not shown in the drawings, the above-described positive electrode, negative electrode, and separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jelly-roll-shaped electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed to complete the lithium battery.

[0137] Lithium batteries are used in electric vehicles (EVs) due to their excellent cycle life and high-rate characteristics. 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.

[0138] Lithium batteries 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. The battery pack includes, for example, multiple battery modules and a bus bar that connects them. The battery module and / or the battery pack may further include a cooling device. The multiple battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0139] [Cathode manufacturing method]

[0140] A method for manufacturing a negative electrode according to another embodiment includes the steps of providing a negative electrode current collector; and the step of providing the protective layer on the negative electrode current collector.

[0141] The above protective layer can be formed by applying a third composition including the first polymer and the second polymer described above onto the negative electrode current collector and then heat-treating at a temperature of 100°C or higher for 1 to 10 hours.

[0142] First, a negative electrode current collector is provided. The negative electrode current collector refers to the negative electrode portion described above. For example, copper foil is provided as the negative electrode current collector.

[0143] Next, a protective layer is provided on the negative electrode current collector. The protective layer includes the steps of: preparing a third composition by mixing a first composition including at least one first polymer selected from among polyamic acid and polyimide substituted with a first functional group and a non-aqueous solvent and a second composition including a water-soluble second polymer having a second functional group and water; applying the third composition on the negative electrode current collector and heat-treating at a temperature of 100° C. or higher to form a protective layer.

[0144] The first polymer, second polymer, and third polymer are the same as those described in the binder section above. The non-aqueous solvent included in the first composition may be a polar solvent such as N-methylpyrrolidone (NMP) or alcohol. The first composition may additionally include water. The second composition may additionally include an aqueous solution containing water or a polar organic solvent such as alcohol that is miscible with water in addition to water. Therefore, the first composition and the second composition can be easily mixed.

[0145] The time for applying the third composition on the negative electrode current collector and heat-treating at a temperature of 100°C or higher is not particularly limited, but for example, the time for applying the third composition on the negative electrode current collector and heat-treating at a temperature of 100°C or higher may be 1 to 10 hours. For example, the time for applying the third composition on the negative electrode current collector and heat-treating at a temperature of 100°C or higher may be 1 to 5 hours. For example, the time for applying the third composition on the negative electrode current collector and heat-treating at a temperature of 100°C or higher may be 1 to 3 hours. If the heat-treatment time is too short, cross-linking may not be sufficiently formed, and if the heat-treatment time is too long, the difference in the degree of cross-linking may be minimal compared to the heat-treatment time. However, if the heat-treatment temperature is too low, the polyamic acid may not be cured into polyimide.

[0146] The method for manufacturing an anode may further include a step of introducing an anode intermediate layer between the anode protective layer and the anode current collector. The anode intermediate layer may include a lithium-compatible metal. The anode intermediate layer may include a lithium-compatible metal and a carbon material. The lithium-compatible metal and the carbon material are the same as those described in the anode intermediate layer section described above. For example, the anode intermediate layer may be provided on the anode current collector by applying nanoparticles including the lithium-compatible metal through a nanoparticle casting method. The anode intermediate layer may be provided, for example, by mixing a lithium-compatible metal and a solvent to prepare a first slurry, and then coating and drying the first slurry on the anode current collector. The solvent may be an organic solvent. The solvent may be, for example, N,N-dimethylacetamide, N-methylpyrrolidone (NMP), etc., but is not necessarily limited thereto, and any solvent used in the art may be used. The first slurry may further include a carbon material.

[0147] The negative electrode manufacturing method may further include a step of introducing a negative electrode active material layer between the protective layer and the negative electrode current collector. The negative electrode active material layer may include, for example, lithium metal and / or a lithium alloy.

[0148] The method for introducing the negative electrode active material layer between the protective layer and the negative electrode current collector is not particularly limited. For example, the negative electrode active material layer may be disposed on the negative electrode current collector before providing the protective layer on the negative electrode current collector. The method for disposing the negative electrode active material layer on the negative electrode current collector is not particularly limited. For example, a lithium metal layer may be disposed on the negative electrode current collector by sputtering or the like. Alternatively, a lithium foil may be disposed on the negative electrode current collector and prepared by rolling. Alternatively, a laminate in which a lithium metal layer is laminated on a copper foil may be commercially available and used. Alternatively, a laminate may be prepared by coating and drying a composition including lithium powder and a binder on a metal substrate. For the lithium powder and binder, refer to the negative electrode section described above. Alternatively, after the negative electrode including the negative electrode current collector and the protective layer is prepared, the negative electrode active material layer may be introduced between the negative electrode collector and the protective layer by charging. The negative electrode active material layer may be, for example, a plated lithium layer.

[0149] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0150] (Manufacturing of cathodes and lithium batteries)

[0151] Example 1: Cu substrate / protective layer (DPHA / PEG-DA, 3 / 1, crosslinking degree (g / n)=141)

[0152] (Cathode manufacturing)

[0153] A 10 μm thick copper foil as a negative current collector was prepared. A precursor solution containing dipentaerythritol hexaacrylate (DPHA) as an ester monomer and polyethylene glycol diacrylate as an alkylene oxide monomer in a 3:1 molar ratio in DMF solvent was applied to the surface of the negative current collector, and then coated using a doctor blade. Thereafter, the solution was dried and thermally crosslinked in a vacuum oven at 70°C for more than 9 hours, thereby preparing an anode in which a protective layer including a crosslinker was laminated on the negative current collector. In this case, the crosslinking degree (g / n) of the crosslinker included in the protective layer was 141.

[0154] (Polar electrode manufacturing)

[0155] The above anode was prepared according to the following method.

[0156] Li 1.04 Ni 0.88 Co 0.1 Al 0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to obtain a weight ratio of active material:carbon conductive material:binder = 90:5:5 to prepare a positive electrode active material slurry. The prepared slurry was coated on a 15 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120°C, and then rolled using a roll press to form a sheet to manufacture a positive electrode.

[0157] (Manufacturing of coin cells)

[0158] An electrode assembly was prepared by sequentially stacking the above-mentioned negative electrode, a polyolefin separator having a thickness of 30 μm, and the above-mentioned positive electrode, and an electrolyte containing 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) in a 2:1 volume ratio mixed solvent of diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) was injected into the electrode assembly to manufacture a coin cell.

[0159] Example 2: Cu substrate / protective layer (PEG-DA (Mw=550), crosslinking degree (g / n)=275)

[0160] Coin cells were manufactured in the same manner as in Example 1, except that polyethylene glycol diacrylate having a weight average molecular weight of 550 was used as the protective film.

[0161] Comparative Example 1: Cu substrate / protective layer (PEG-DA (Mw=2,000), crosslinking degree (g / n)=1000)

[0162] Coin cells were manufactured in the same manner as in Example 1, except that polyethylene glycol diacrylate having a weight average molecular weight of 2,000 was used as the protective film.

[0163] Comparative Example 2: Cu substrate / protective layer (PEG-MA (Mw=500), crosslinking degree (g / n)=500)

[0164] Coin cells were manufactured in the same manner as in Example 1, except that polyethylene glycol monoacrylate having a weight average molecular weight of 500 was used as the protective film.

[0165] Comparative Example 3: Cu substrate / without protective layer

[0166] Coin cells were manufactured in the same manner as in Example 1, except that the cathode did not include a protective layer.

[0167] Evaluation Example 1: Evaluation of the physical properties of the protective layer

[0168] Using the protective layers manufactured in Examples 1 to 2 and Comparative Examples 1 to 2, a 5×5 cm sized film was formed on a glass substrate. 2 After manufacturing a polymer film with a thickness of 50 ㎛, the mechanical properties of the polymer were evaluated as follows.

[0169] The recovery, modulus, and hardness of the protective layers manufactured in Examples 1 and 2 and Comparative Examples 1 and 2 were measured using a microindenter (DUH-211, Shimadzu). The force applied to the polymer film sample was 10 mN.

[0170] The measurement results are shown in Table 1 below. The recovery rate is the ratio of the distance the tip moves toward the sample surface from the point where the tip has moved the most into the sample to the point where the force applied to the tip becomes zero, to the distance the tip has moved into the sample. The modulus is the indentation modulus and the hardness is the indentation hardness, and they are calculated from the force applied to the tip from the sample according to the distance the microindenter tip has moved.

[0171] Evaluation Example 2: Swelling Evaluation of the Protective Layer

[0172] The protective layers manufactured in Examples 1 to 2 and Comparative Examples 1 to 2 were immersed in an electrolyte (EC: DEC: FEC=5:70:25), stored at 60 degrees for 72 hours, and the weight after swelling occurred was measured. The swelling ratio was calculated by (film weight before swelling - film weight after swelling) / weight before swelling * 100.

[0173] Crosslinked polymer Crosslinking degree (g / n) Recovery rate [%] Modulus [GPa] Hardness [N / mm2] Swelling ratio [%] Example 1 DPHA / PEG-DA (3 / 1) 14 16 38 49.99 2.92 88 Example 2 PEG-DA (Mw = 550) 27 59 4.97 9.8 13 359 Comparative example 1 PEG-DA (Mw = 2,000) 1,000 90 213.55 54 Comparative example 2 PEG-MA (Mw = 500) 500 754 4.0 Dissolved

[0174] As shown in Table 1 above, the protective layers of Examples 1 and 2 had increased modulus, i.e., elastic coefficient and hardness, compared to the protective layers of Comparative Examples 1 and 2, thereby suppressing expansion of the negative electrode.

[0175] For example, the protective layer according to Example 1 can function as a protective layer as it satisfies a recovery rate of 60% or more, and has significantly improved modulus, hardness, and swelling ratio compared to the protective layer according to Comparative Examples 1 and 2, so that the life characteristics of a lithium secondary battery including the protective layer according to Example 1 can be improved.

[0176] Evaluation Example 3: Charge / Discharge Characteristics Evaluation

[0177] The lithium batteries (coin cells) manufactured in Examples 1 to 2 and Comparative Examples 1 to 3 were charged at a constant current rate of 0.1 C at 25°C until the voltage reached 0.01 V (vs. Li), and then charged at a constant voltage rate until the current reached 0.01 C while maintaining 0.01 V. After charging, the lithium batteries were allowed to rest for 10 minutes, and then discharged at a constant current rate of 0.1 C until the voltage reached 1.5 V (vs. Li) (1 st cycle).

[0178] Then, the coin cell was charged at a constant current rate of 0.2 C until the voltage reached 0.01 V (vs. Li), and then charged at a constant voltage rate until the current reached 0.01 C while maintaining 0.01 V. After the coin cell was rested for 10 minutes after charging, it was discharged at a constant current rate of 0.2 C until the voltage reached 1.5 V (vs. Li) (2 nd cycle)(1st-2nd cycle is the Mars phase).

[0179] The coin cell that went through the above-mentioned Mars step was charged at a constant current of 0.33C at 45℃ until the voltage reached 0.01V (vs. Li), and then charged at a constant voltage while maintaining 0.01V until the current reached 0.01C. After the coin cell was rested for 10 minutes after completion of charging, the discharge cycle was repeated 100 times at a constant current of 1.0C until the voltage reached 1.5V (vs. Li). The capacity retention rate at each cycle was measured and shown in Fig. 6.

[0180] The capacity retention rate was calculated from the following mathematical formula 1.

[0181] <Mathematical Formula 1>

[0182] Capacity retention rate [%] = [Discharge capacity of each cycle / 3] rd Discharge capacity of cycle] × 100

[0183] Referring to FIG. 6, the lithium secondary batteries of Examples 1 to 2 have improved life characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 3.

Claims

1. Negative current collector; and A protective layer is disposed on the negative electrode current collector and includes a crosslinked polymer including repeating units derived from one or more polyfunctional crosslinking agents, A cathode having a crosslinking density (g / n) of the above crosslinked polymer of 300 or less.

2. In paragraph 1, The ionic conductivity of the above protective layer is 0.01 mS / cm or more at 25°C, the cathode.

3. In paragraph 1, A negative electrode, wherein the crosslinked polymer comprises a repeating unit (A) derived from an ester monomer; or a repeating unit (B) derived from an alkylene oxide monomer.

4. In paragraph 3, The above alkylene oxide monomer comprises a unit represented by the following chemical formula 1, the cathode: <Chemical Formula 1> In the above chemical formula 1, L1 is an alkylene group having 2 to 5 carbon atoms, * is a bonding site with a neighboring atom.

5. In paragraph 4, In the above chemical formula 1, L1 is a polymer electrolyte having an ethylene group, a propylene group, or an isopropylene group.

6. In paragraph 3, A negative electrode, wherein the alkylene oxide monomer comprises glyceryl propoxy triacrylate, glyceryl ethoxy triacrylate, tri-propoxylated glycerol triacrylate, tetra-propoxylated glycerol triacrylate, polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, or any combination thereof.

7. In paragraph 3, The above ester monomer comprises a unit represented by the following chemical formula 2, the negative electrode: <Chemical Formula 2> In the above chemical formula 2, * is a bonding site with a neighboring atom.

8. In paragraph 3, A negative electrode, wherein the ester monomer comprises pentaerythritol triacrylate, pentaerythritol tatracrylate, dipentaerythritol hexacrylate, butyl acrylate, methyl metacrylate, trimethylolpropane triacrylate, or any combination thereof.

9. In paragraph 1, The above crosslinked polymer is a negative electrode comprising a repeating unit (A) derived from an ester monomer; and a repeating unit (B) derived from an alkylene oxide monomer.

10. In paragraph 9, A negative electrode, wherein the ratio of the number of moles of repeating units (A) derived from the ester monomer to the number of moles of repeating units (B) derived from the alkylene oxide monomer among the crosslinked polymers is 1 to 20.

11. In paragraph 9, The above alkylene oxide monomer has at least one crosslinking point, A cathode having three or more cross-linking points of the above ester monomer.

12. In paragraph 9, A negative electrode, wherein the difference in the number of crosslinking points between the ester monomer and the alkylene oxide monomer is 2 to 6.

13. In paragraph 1, The above protective layer further comprises a lithium salt, an inorganic oxide or a linear polymer, wherein the negative electrode.

14. In paragraph 13, The above lithium salts are LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 A cathode comprising SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI or a mixture thereof.

15. In paragraph 13, The above inorganic oxide is a cathode comprising MgO, AlMgO, Al2O3, Nb2O5, TiO2, SiO2, ZrO2, SnO2, ZnO, Co3O4, HfO2, VO, NiO, Bi2O3, Ta2O5, GeO2, Ga2O3, In2O3 or any combination thereof.

16. In paragraph 13, The above linear polymers are vinyl acetate, vinyl alcohol, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl A negative electrode comprising a polymerization reaction product of one or more monomers selected from (meth)acrylate, 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylenedi(meth)acrylate, diethyleneglycol(meth)acrylate, triethyleneglycoldi(meth)acrylate, trimethylenepropanetri(meth)acrylate, trimethylenepropanetriacrylate, 1,3-butanediol(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof.

17. In paragraph 1, The thickness of the above protective layer is 5㎛ or less, the cathode.

18. In paragraph 1, The above negative electrode collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, A cathode, wherein the metal layer comprises 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.

19. Bipolar; The cathode according to paragraph 1; and A lithium battery comprising an electrolyte disposed between the positive electrode and the negative electrode.

20. In paragraph 19, A lithium secondary battery wherein the electrolyte is a liquid electrolyte, a solid electrolyte, a gel electrolyte or a combination thereof.

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