Negative electrode and lithium battery containing the same

Abstract

A lithium battery is presented comprising a negative electrode current collector; a protective layer disposed on one surface of the negative electrode current collector; and a negative electrode intermediate layer disposed between the negative electrode current collector and the protective layer, wherein the protective layer comprises a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer, and the negative electrode intermediate layer comprises a mixture of first particles containing a lithium-affinity metal and second particles containing carbon elements.

Description

[Technical Field]

[0001] This invention relates to a negative electrode and a lithium battery containing the same. [Background technology]

[0002] Currently available lithium batteries primarily use carbon-based negative electrode active materials such as graphite. Because carbon-based negative electrode active materials do not change in volume during charging and discharging, lithium batteries have high stability. However, the theoretical electrical capacity of graphite is small, at approximately 372 mAh / g.

[0003] A negative electrode without a negative electrode active material layer may be used. In a negative electrode with a free negative electrode active material layer, the layer forms on the lithium layer on the current collector surface during charging and discharging. In this case, if the lithium layer is not uniformly formed on the current collector surface, lithium dendrites may form, and as these dendrites grow, they may induce a short circuit between the positive and negative electrodes. As a result, the lifespan characteristics of lithium batteries containing a negative electrode with a free negative electrode active material layer will be reduced.

[0004] A method is needed to improve the lifespan characteristics of lithium batteries that include a negative electrode in which the negative electrode active material layer is free. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The problem that this invention aims to solve is to provide a negative electrode with a novel structure.

[0006] Furthermore, the problem that this invention aims to solve is to provide a lithium battery that includes a negative electrode with a novel structure. [Means for solving the problem]

[0007] Based on one concrete example, Negative electrode current collector and A protective layer disposed on one surface of the negative electrode current collector, It includes a negative electrode interlayer (anode interlayer) disposed between the negative electrode current collector and the protective layer, The protective layer comprises a first polymer and a second polymer, the first polymer comprising a high-strength polymer, and the second polymer comprising an ion-conducting polymer. The negative electrode is provided, in which the negative electrode intermediate layer comprises a mixture of first particles made of carbon and second particles made of a lithium-affinity metal.

[0008] Another concrete example shows that A lithium battery is provided, comprising a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. [Effects of the Invention]

[0009] On one side, by employing a negative electrode having a double-layer structure consisting of a protective layer and a negative electrode intermediate layer, it is possible to provide a lithium battery with improved cycle characteristics. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the negative electrode in an exemplary example. [Figure 2] This is a cross-sectional view of the negative electrode in another exemplary example. [Figure 3] This is a schematic diagram of a lithium battery based on an exemplary example. [Figure 4] This is a schematic diagram of a lithium battery based on an exemplary example. [Figure 5] This is a schematic diagram of a lithium battery based on an exemplary example. [Figure 6] This is a scanning electron microscope image of the negative electrode cross-section manufactured in Example 1. [Figure 7] This graph shows the charge-discharge experiment results for Example 1 and Comparative Example 1. [Figure 8] This graph shows the charge-discharge experiment results for Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0011] In lithium batteries that use a negative electrode containing a protective layer and a negative electrode current collector, and in which the negative electrode active material layer is free, a lithium-containing metal layer is deposited and dissolved between the negative electrode current collector and the protective layer during the charge-discharge process. As the lithium battery is repeatedly charged and discharged, the lithium-containing metal layer contains impurities remaining in the electrode, decomposition products of the electrolyte, etc. Therefore, the surface of the lithium-containing metal layer becomes rough and hard due to the presence of such impurities. On such a rough lithium-containing metal layer, lithium dendrites are formed, inducing perforation of the protective layer, and the reduced adhesion between the lithium-containing metal layer and the protective layer allows the electrolyte to flow between the protective layer and the lithium-containing metal layer, potentially causing the protective film to detach. Furthermore, as the lithium battery is repeatedly charged and discharged, the electrolyte is continuously consumed by side reactions, which can cause a sudden decrease in the cycle characteristics of the lithium battery.

[0012] A negative electrode for a lithium battery with a single side surface employs a negative electrode having a double-layer structure consisting of a protective layer and an intermediate negative electrode layer. This suppresses deformation and perforation of the protective layer, maintains adhesion between the protective layer and the lithium-containing metal deposited during the charge-discharge process, and prevents the protective film from detaching. As a result, lithium dendrite formation is suppressed, and electrolyte consumption is reduced, improving the cycle characteristics of lithium batteries employing such a negative electrode.

[0013] The present inventive concept described below can be subjected to various transformations and has many embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this should not be understood as limiting the present inventive concept to specific embodiments, but rather as encompassing all transformations, equivalents, or substitutes within the technical scope of the present inventive concept.

[0014] The terms used below are used solely to describe specific embodiments and are not intended to limit the scope of this invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereafter, terms such as “includes” or “has” are intended to indicate the presence of features, numbers, stages, operations, components, parts, ingredients, materials, or combinations thereof described in the specification, and should not be understood as preemptively excluding the existence or possibility of adding one or more other features, numbers, stages, operations, components, parts, ingredients, materials, or combinations thereof. The “ / ” used below is to be interpreted as “and” and also as “or,” depending on the context.

[0015] Thicknesses were enlarged or reduced in the drawings to clearly represent many layers and regions. Similar parts throughout the specification are denoted by the same reference numerals. Throughout the specification, when a part such as a layer, film, region, or plate is described as being "on top of" or "above" another part, this includes not only cases where it is directly above another part, but also cases where there are other parts in between. Throughout the specification, terms such as "first," "second," etc., may be used to describe various components, but components should not be limited by these terms. The terms are used solely to distinguish one component from another. To avoid redundant explanations, components having substantially the same functional configuration are referred to by the same reference numerals in this specification and drawings.

[0016] In this invention, the "size" of a particle refers to, for example, its "particle diameter." If the particle is spherical, the particle diameter indicates the average diameter; if the particle is non-spherical, it indicates the average major axis length. The particle diameter can be measured using a particle size analyzer (PSA). The particle diameter 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, for example, the size of the particle corresponding to the 50% cumulative volume, calculated from the particle size with the smallest particle size in a particle size distribution measured by laser diffraction.

[0017] In this invention, "metal" includes both metals and metalloids such as silicon and germanium, in their elemental or ionic state.

[0018] In this invention, "alloy" means a mixture of two or more metals.

[0019] In this invention, "positive electrode active material" means a positive electrode material that can be lithium-ionized and delithiated.

[0020] In this invention, "negative electrode active material" means a negative electrode material that can be lithium-treated and delithiated.

[0021] In this invention, "lithification" and "lithification" refer to the process of adding lithium to the positive electrode active material or the negative electrode active material.

[0022] In this invention, "desitization" and "desitizing" refer to the process of removing lithium from the positive electrode active material or the negative electrode active material.

[0023] In this invention, "charging" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0024] In this invention, "discharge" and "to discharge" refer to the process of removing electrochemical energy from a battery.

[0025] In this invention, "positive electrode" and "cathode" refer to electrodes in which electrochemical reduction and lithiumization occur during the discharge process.

[0026] In this invention, "negative electrode" and "anode" refer to electrodes in which electrochemical oxidation and delithiation occur during the discharge process.

[0027] The following provides a more detailed explanation of the negative electrode for lithium metal batteries and the lithium battery containing it, using illustrative examples.

[0028] [Negative electrode] An embodiment of a lithium battery anode includes a negative electrode current collector; a protective layer disposed on one surface of the negative electrode current collector; and anode interlayer disposed between the negative electrode current collector and the protective layer, wherein the protective layer comprises a first polymer and a second polymer, the first polymer comprising a high-strength polymer, the second polymer comprising an ion-conducting polymer, and the anode interlayer comprising a mixture of first particles containing carbon and second particles containing a lithium-affinity metal.

[0029] The negative electrode intermediate layer contains a mixture of first particles containing carbon and second particles containing a lithium-affinity metal. The first particles ensure that the second particles containing the lithium-affinity metal are uniformly coated onto the negative electrode current collector. The uniformly coated second particles on the negative electrode current collector induce the uniform formation of a lithium-containing metal layer between the double layer structure, which includes the protective layer and the negative electrode intermediate layer, and the negative electrode current collector. This induces strong adhesion between the double layer structure and the lithium-containing metal layer, preventing deformation or detachment of the protective layer.

[0030] Specifically, the first particles cause the second particles to be uniformly distributed at the interface between the protective layer and the negative electrode current collector, thereby forming a negative electrode intermediate layer in which the second particles are uniformly distributed, and allowing lithium ions to be uniformly distributed between the interface between the negative electrode intermediate layer and the negative electrode current collector. Therefore, local current density imbalances between the negative electrode intermediate layer and the negative electrode current collector are suppressed, and lithium metal can be uniformly deposited (plated) between the negative electrode intermediate layer and the negative electrode current collector. By uniformly depositing lithium metal between the negative electrode intermediate layer and the negative electrode current collector, the deposition and / or growth of lithium dendrites due to local current density imbalances between the negative electrode intermediate layer and the negative electrode current collector can be effectively suppressed. By simultaneously containing the first and second particles in the negative electrode intermediate layer, the uniformity of lithium ion distribution within the negative electrode intermediate layer and / or between the negative electrode intermediate layer and the negative electrode current collector can be increased.

[0031] Furthermore, the negative electrode intermediate layer containing both the first and second particles has greater adhesion to the protective layer than to the negative electrode current collector, allowing the negative electrode current collector and the negative electrode intermediate layer to separate during charging and discharging, and enabling lithium ions to flow more easily into the region between the negative electrode current collector and the negative electrode intermediate layer. This allows a lithium-containing metal layer to form more easily in the region between the negative electrode current collector and the negative electrode intermediate layer. In addition, the negative electrode intermediate layer can improve the adhesion between the lithium-containing metal layer and the protective layer, preventing the protective layer from detaching during charging and discharging of the battery.

[0032] Referring to Figure 1, the negative electrode 20 includes a negative electrode current collector 21; a protective layer 24 disposed on the negative electrode current collector 21; and a negative electrode intermediate layer 22 disposed between the negative electrode current collector 21 and the protective layer 24, wherein the protective layer 24 includes a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer, and the negative electrode intermediate layer 22 includes a mixture of first particles containing carbon and second particles containing a lithium-affinity metal.

[0033] Referring to Figure 2, the negative electrode 20 includes a negative electrode current collector 21; a protective layer 24 disposed on the negative electrode current collector 21; a negative electrode intermediate layer 22 disposed between the negative electrode current collector 21 and the protective layer 24; and a metal layer 23 disposed between the negative electrode intermediate layer 22 and the negative electrode current collector 21. The protective layer 24 includes a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer. The negative electrode intermediate layer 22 includes a mixture of first particles containing carbon and second particles containing a lithium-affinity metal. The metal layer 23 contains a lithium-affinity metal.

[0034] [Negative electrode: anode interlayer] Referring to Figure 1, the negative electrode 20 may include an anode interlayer 22 positioned between the negative electrode current collector 21 and the protective layer 24. Referring to Figure 2, the negative electrode 20 may include an anode interlayer 22 positioned between the protective layer 23 and the metal layer 23. The inclusion of an anode interlayer in the negative electrode 20 can further effectively suppress the formation and / or growth of lithium dendrites in the negative electrode 20.

[0035] The negative electrode intermediate layer 22 may include, for example, a mixture of first particles containing a lithium-affinity metal and second particles containing a carbon element.

[0036] The lithium-affinity metal contained in the first particle is a material that is lithified and delithified. The negative electrode intermediate layer 22 can be formed by introducing the lithium-affinity metal onto the negative electrode current collector 21 via nanoparticle casting. Specifically, nanoparticle casting is performed by applying a slurry (dispersion) obtained by mixing the first particle and the second particle and dispersing it in a solvent onto the negative electrode current collector 21 using a doctor blade. When the negative electrode intermediate layer 22 is introduced onto the negative electrode current collector 21 via nanoparticle casting, lithium ions can permeate the negative electrode intermediate layer 22, and lithium metal can be formed between the negative electrode intermediate layer 22 and the negative electrode current collector 21.

[0037] The first particles contained in the negative electrode intermediate layer 22 are also nanoparticles of the lithium affinity metal. The average particle size of the first particles can be, for example, 10 nm to 4 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. Having an average particle size in such a range of sizes makes reversible plating and / or dissolution of lithium easier during charging and discharging. Also, having a nano-size of the first particles allows lithium ions to permeate the negative electrode intermediate layer 22 containing the first particles, and lithium metal can be deposited between the negative electrode current collector 21 and the negative electrode intermediate layer 21. The average particle size of the first particles is, for example, the median diameter (D50) measured using a laser particle size analyzer.

[0038] 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).

[0039] The second particles can uniformly coat the first particles onto the negative electrode current collector 21. The second particles, which contain carbon, can uniformly coat the first particles onto the negative electrode current collector 21, thereby uniformly coating the first particles onto the negative electrode current collector 21. The uniformly coated first particles can prevent the formation of lithium dendrites by allowing lithium metal to uniformly precipitate on the negative electrode current collector 21.

[0040] The second particles may include, for example, amorphous carbon, crystalline carbon, or any combination thereof.

[0041] The amorphous carbon may include, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, carbon nanotubes, or any combination thereof. The amorphous carbon is carbon that is non-crystalline or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0042] The negative electrode intermediate layer 22 includes, for example, a mixture of first particles containing a lithium-affinity metal and second particles containing a carbon element. The first particles are uniformly coated onto the negative electrode current collector 21 via the second particles, and the first particles can uniformly deposit lithium metal between the negative electrode intermediate layer 22 and the negative electrode current collector 21. This suppresses the formation of lithium dendrites and can improve the lifespan characteristics of the lithium battery including the negative electrode 20. Furthermore, the negative electrode intermediate layer 22 can firmly adhere the deposited lithium metal to the protective layer 24 (described later), preventing deformation and perforation of the protective layer 24 due to uneven deposition of lithium metal.

[0043] The mixing ratio of the first particle and second particle mixture contained in the negative electrode intermediate layer 22 is, 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 by weight.

[0044] The negative electrode intermediate layer 22 may further contain a binder. Examples of binders included in the negative electrode intermediate layer 22 include, but are not limited to, polyacrylic acid, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. Any binder that is usable in the art may be used. The binder may consist of one or more different binders. If the negative electrode intermediate layer 22 does not contain a binder, it can be easily separated from the protective layer 24 or the negative electrode current collector 21. The binder content in the negative electrode intermediate layer 22 is, for example, 55% by weight or less, 0.1 to 50% by weight, 0.1 to 20% by weight, or 0.1 to 10% by weight relative to the total weight of the negative electrode intermediate layer 22.

[0045] The thickness of the negative electrode intermediate layer can be, for example, 0.1 μm to 5 μm, 0.1 μm to 3 μm, or 0.5 μm to 5 μm, 0.5 μm to 3 μm, or 0.5 μm to 2 μm. If the thickness of the negative electrode intermediate layer is excessively thin, lithium dendrites formed between the negative electrode intermediate layer and the negative electrode current collector will cause the negative electrode intermediate layer to disintegrate, making it difficult to improve the cycle characteristics of the lithium battery. If the thickness of the negative electrode intermediate layer is excessively increased, the energy density of the lithium battery using negative electrode 20 will decrease, making it difficult to improve the cycle characteristics. If the thickness of the negative electrode intermediate layer decreases, for example, the charging capacity of the negative electrode intermediate layer will also decrease. The charging capacity of the negative electrode intermediate layer can be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the total charging capacity. If the charging capacity of the negative electrode intermediate layer is excessively small, lithium dendrites formed between the negative electrode intermediate layer and the negative electrode current collector will cause the negative electrode intermediate layer to disintegrate, making it difficult to improve the cycle characteristics of the lithium battery. If the charging capacity of the negative electrode intermediate layer is excessively large, the energy density of the lithium battery using negative electrode 20 will decrease, making it difficult to improve the cycle characteristics.

[0046] The charging capacity of the positive electrode active material layer is obtained by multiplying the charging capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the layer. When various positive electrode active materials are used, the charging capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charging capacity of the positive electrode active material layer.

[0047] The charging capacity of the negative electrode intermediate layer is calculated in a similar manner. That is, the charging capacity of the negative electrode intermediate layer is obtained by multiplying the charging 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 various negative electrode active materials are used, the charging capacity density × mass value is calculated for each negative electrode active material, and the sum of these values ​​is the charging capacity of the negative electrode intermediate layer. Here, the charging capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid-state half-cell with lithium metal as the relative electrode. The charging capacity of the positive electrode active material layer and the negative electrode intermediate layer is directly measured by measuring the charging capacity using an all-solid-state half-cell. Dividing the measured charging capacity by the mass of the active material yields the charging capacity density. In other embodiments, the charging capacity of the positive electrode active material layer and the negative electrode intermediate layer are also the initial charging capacity measured during the first charging cycle.

[0048] [Negative electrode: protective layer] Referring to Figures 1 and 2, the negative electrode 20 includes a negative electrode current collector 21; a protective layer 24 placed on the negative electrode current collector 21; and a negative electrode intermediate layer 22 placed between the negative electrode current collector 21 and the protective layer 24.

[0049] The protective layer 24 comprises a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer. If the protective layer 24 does not contain the first and second polymers, the protective layer 24 can be easily separated from the negative electrode intermediate layer 22 and / or the negative electrode current collector 21.

[0050] The first polymer includes a high-strength polymer having a larger elastic modulus than the second polymer. The high-strength polymer has a large elastic modulus, and even if lithium dendrites are formed due to the uneven deposition of lithium metal during the process of forming the metal layer 23 between the negative electrode current collector 21 and the negative electrode intermediate layer 22, the protective layer 24 containing the high-strength polymer is pressed onto the metal layer 23 without deformation, thereby suppressing the formation of lithium dendrites.

[0051] The first polymer is, for example, a fluorine-based polymer. The fluorine-based polymer is, for example, polytetrafluoroethylene, polyvinylidene fluoride, or polyvinylidene fluoride / hexafluoropropylene copolymer. The fluorine-based polymer may include, for example, polyvinylidene fluoride.

[0052] The second polymer includes an ion-conducting polymer. By including the ion-conducting polymer in the protective layer 24, the protective layer 24 can selectively allow lithium ions contained in the electrolyte to permeate, effectively suppressing side reactions with organic solvents.

[0053] The ion-conducting polymer may include, for example, polyethylene oxide (PEO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, and polyacetylene or any combination thereof. The ion-conducting polymer may include, for example, polyethylene oxide (PEO).

[0054] The content of the first polymer is greater than or equal to the content of the second polymer. The content ratio of the first polymer to the second polymer is, for example, 50:50 to 99:1. When the content of the first polymer is greater than or equal to the content of the second polymer, the protective layer 24 has sufficient elastic strength and ionic conductivity, which can further effectively suppress the formation of lithium dendrites.

[0055] The content ratio of the first polymer to the second polymer is, for example, 60:40 to 99:1, 70:30 to 99:1, 80:20 to 99:1, or 85:15 to 95:5.

[0056] The weight-average molecular weights of the first and second polymers are 300,000 Daltons to 1,000,000 Daltons, or 400,000 Daltons to 600,000 Daltons, respectively. The weight-average molecular weights of the first and second polymers can be measured, for example, using gel permeation chromatography (GPC) on a polystyrene standard sample.

[0057] In other examples, the protective layer 24 is lithium salt-free and non-porous. The protective layer 24 does not contain lithium salts, which can prevent a decrease in the lifespan of the lithium battery due to side reactions between lithium salts contained in the protective layer 24 and the electrolyte. Furthermore, the protective layer 24 has a non-porous structure, which, compared to a protective layer 24 with a porous structure, makes it easier to prevent deformation and perforation of the protective layer 24 caused by lithium dentite generated during the process of lithium deposition between the negative electrode intermediate layer 22 and the negative electrode current collector 21.

[0058] The thickness of the protective layer 24 can be, for example, 100 nm to 20 μm, 500 nm to 20 μm, 1 μm to 20 μm, 1 μm to 15 μm, or 1 μm to 10 μm. By having a protective layer 24 with a thickness in such a range, the decomposition of the electrolyte can be effectively suppressed, local current density imbalances can be suppressed, and the formation and / or growth of lithium dendrites can be effectively prevented. Therefore, the cycle characteristics of a 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 decrease. If the thickness of the protective layer 24 is excessively decreased, the improvement in the cycle characteristics of the lithium metal battery will be minimal.

[0059] The thickness of the negative electrode intermediate layer 22 is thinner than or the same as the thickness of the protective layer 24. The thickness ratio of the negative electrode intermediate layer 22 to the protective layer 24 is, for example, 1:1 to 1:20, 1:1 to 1:15, 1:1 to 1:10, 1:1 to 1:5, 1:2 to 1:20, 1:2 to 1:10, or 1:2 to 1:5. By having a negative electrode intermediate layer 22 that is thinner than or the same as the protective layer 24, the overall structural strength of the negative electrode 20 can be improved, and the durability of the negative electrode 20 can be improved.

[0060] [Negative electrode: negative electrode current collector] Referring to Figures 1 and 2, the negative electrode 20 includes the negative electrode current collector 21. 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), tin (Sn), lithium (Li), or alloys or combinations thereof.

[0061] The negative electrode current collector 21 includes, for example, a first metal substrate. The first metal substrate contains a first metal as its main component or consists of a first metal. The content of the first metal in the first metal substrate is, for example, 90% or more by weight, 95% or more by weight, 99% or more by weight, or 99.9% or more by weight relative to 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 alloys and / or compounds 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), tin (Sn), lithium (Li), or alloys thereof. The first metal substrate may be composed of, for example, one of the above-mentioned metals, an alloy of two or more metals, or a combination of two or more metals. The first metal substrate is, for example, a sheet or foil. The thickness of the negative electrode current collector 21 is, 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 such ranges and can be selected depending on the required lithium battery characteristics.

[0062] 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 containing a second metal. The second metal has a higher Mohs hardness than the first metal. That is, the coating layer containing the second metal is harder than the substrate containing the first metal, thus preventing deterioration of the first metal substrate. 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 is also, for example, 2.0 to 6.0. The coating layer contains the second metal. The coating layer, for example, contains the second metal as a main component or consists of the second metal. The content of the secondary metal in the coating layer is, for example, 90% or more by weight, 95% or more by weight, 99% or more by weight, or 99.9% or more by weight relative to 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 alloys and / or compounds with lithium. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or higher. For example, the Mohs hardness of the secondary metal is 6.0 or higher, 6.5 or lower, 7.0 or higher, 7.5 or higher, 8.0 or higher, 8.5 or higher, or 9.0 or higher. The Mohs hardness of the secondary metal is also, for example, 6.0 to 12. If the Mohs hardness of the secondary metal is excessively low, it is difficult to suppress the deterioration of the negative electrode current collector. If the Mohs hardness of the secondary metal is excessively high, processing is not easy. The second metal is one or more selected from, for example, 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-mentioned metals or an alloy of two or more metals. The difference in Mohs hardness between the first metal contained in the first metal substrate and the second metal contained in the coating layer is, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. Having such a difference in Mohs hardness between the first and second metals can further effectively suppress the deterioration of the negative electrode current collector.The coating layer may be a single layer or a multi-layer structure of two or more layers. For example, the coating layer may be a two-layer structure including a first coating layer and a second coating layer. Alternatively, it may be a three-layer structure including 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 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. If the coating layer is excessively thin, it is difficult to suppress the uneven growth of the lithium-containing metal layer. While increasing the thickness of the coating layer improves the cycle characteristics of the lithium battery, excessively thick coating layers reduce the energy density of the lithium battery, making coating layer formation difficult. The coating layer may be formed on the first metal substrate by methods such as vacuum deposition, sputtering, or plating, but is not limited to such methods; any method capable of forming a coating layer in the relevant art can be used.

[0063] 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 also 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. By including a thermoplastic polymer in the base film, the base film can liquefy when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may also be, for example, an insulator. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The metal layer can act as an electrochemical fuse to cut off in the event of overcurrent, thereby performing a short-circuit prevention function. The thickness of the metal layer can be adjusted to adjust the limit current and the maximum current. The metal layer can be plated or deposited onto the base film. Reducing the thickness of the metal layer can decrease the limiting current and / or maximum current of the negative electrode current collectors 521b and 522b, thereby improving the stability of the lithium battery during short circuits. Lead tabs can be added to the metal layer for external connection. The lead tabs can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer may melt while the metal layer is electrically connected to the lead tab. To further strengthen the weld between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab. The metal chip is also a thin piece of the same material as the metal layer. The metal chip can also be, for example, metal foil or metal mesh. The metal chip can also be, for example, aluminum foil, copper foil, or SUS foil. After placing a metal piece on a metal layer, the lead tab can be welded to a metal piece / metal layer laminate or a metal piece / metal layer / base film laminate by welding the lead tab to the metal layer.During welding, the base film, metal layer, and / or metal chip may melt, and the metal layer or metal layer / metal chip laminate may be electrically bonded to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal layer. The thickness of the base film may be, for example, 1-50 μm, 1.5-50 μm, 1.5-40 μm, or 1-30 μm. Having the base film in such a thickness range can further effectively reduce the weight of the electrode assembly. The melting point of the base film may be, for example, 100-300°C, 100-250°C or lower, or 100-200°C. Having the base film in such a melting point range allows the base film to melt during the welding process of the lead tab and be easily bonded to the lead tab. Surface treatments such as corona treatment may be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01-3 μm, 0.1-3 μm, 0.1-2 μm, or 0.1 μm. Having the metal layer in such a thickness range can ensure the stability of the electrode assembly while maintaining conductivity. The thickness of the metal piece can also be, for example, 2-10 μm, 2-7 μm, or 4-6 μm. Having the metal piece in such a thickness range can further facilitate the connection between the metal layer and the lead tab. Having such a structure in the negative electrode current collectors 521b and 522b can reduce the weight of the electrode and, as a result, improve the energy density.

[0064] In one embodiment of the present invention, the positive electrode current collector 511b 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 also 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. The inclusion of a thermoplastic polymer in the base film allows the base film to liquefy when a short circuit occurs, thereby suppressing a rapid increase in current. The base film may also be, for example, an insulator. 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), or alloys thereof. The positive electrode current collector 511b may additionally include metal pieces and / or lead tabs. For more specific details regarding the base film, metal layer, metal piece, and lead tab of the positive electrode current collector 511b, refer to the negative electrode current collectors 521b and 522b described above. The positive electrode current collector 511b having such a structure can reduce the weight of the electrodes and, as a result, improve energy density.

[0065] [Negative electrode: metal layer] Referring to Figure 2, the negative electrode 20 may further include a metal layer 23 positioned between the negative electrode current collector 21 and the negative electrode 22. The metal layer 23 may include, for example, a lithium-affinity metal.

[0066] The metal layer 23 may contain one or more elements selected from the group consisting of, for example, 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).

[0067] The metal layer 23 may, for example, contain the lithium-affinity metal particles. The metal layer 23 can be formed by introducing the lithium-affinity metal particles onto the negative electrode current collector 21 through sputtering or nanoparticle casting.

[0068] The lithium-affinity metal particles contained in the metal layer 23 are also nanoparticles of the lithium-affinity metal. The average particle size of the lithium-affinity metal particles can be, for example, 10 nm to 4 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. Having an average particle size in such a range of lithium-affinity metal particles makes the reversible deposition (plating) and / or dissolution of lithium during charging and discharging even easier. The average particle size of the lithium-affinity metal particles is, for example, the median diameter (D50) measured using a laser particle size analyzer.

[0069] The metal layer 23 is also binder-free. The absence of a binder in the metal layer 23 can improve current density. This can increase the overall capacity of the lithium battery, including the negative electrode 20 containing the metal layer 23.

[0070] [Lithium battery] A lithium battery according to one embodiment includes a positive electrode; the negative electrode described above; and an electrolyte disposed between the positive and negative electrodes. By including the negative electrode described above, the lithium battery can simultaneously provide improved capacity and excellent lifespan characteristics.

[0071] Lithium batteries include, for example, primary lithium batteries, secondary lithium batteries, lithium-sulfur batteries, and lithium-air batteries, but are not limited to these; any lithium battery used in the relevant technical field can be used.

[0072] Lithium batteries are manufactured, for example, by the exemplary methods described below, but are not necessarily limited to such methods and may be adjusted according to the required conditions.

[0073] Negative electrode Prepare the negative electrode described above.

[0074] Positive electrode First, a positive electrode active material, a conductive agent, a binder, and a solvent are mixed to prepare a positive electrode active material composition. 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. In other embodiments, 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.

[0075] As the positive electrode active material, any lithium-containing metal oxide that is commonly used in the art can be used without limitation. For example, one or more of composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof and lithium are used. 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 formula, 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 F α (in the above formula, 0.90 ≦ a ≦ 1, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, 0 < α < 2); Lia Ni 1-b-c Co b B c O 2-α F2(In the above equation, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2);Li a Ni 1-b-c Mn b B c D α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 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 b O2 (In the above formula, 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (In the above formula, 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (In the above formula, 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); Li a Mn2G bO4 (In the above formula, 0.90 ≤ a ≤ 1 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Compounds represented by any one of the chemical formulas Fe2(PO4)3(0≦f≦2) or LiFePO4 may be used.

[0076] In the chemical formulas representing the compounds described above, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, 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 compounds with a coating layer attached to the surface of the compounds described above, and it is also possible to use mixtures of the compounds described above and compounds with a coating layer attached. The coating layer applied to the surface of the above-mentioned compound includes, for example, a coating element compound of an oxide, hydroxide, oxyhydroxy, oxycarbonate, or hydroxycarbonate of the coating element. The compound forming such a 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 mixtures 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 is, for example, spray coating or immersion method. Since the specific coating method is well understood by those skilled in the art, a detailed explanation is omitted.

[0077] The positive electrode active material is, for example, Li a Ni x Co y M z O 2-b A b (where 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1, 0 < y ≤ 0.3, 0 < z ≤ 0.3, and x + y + z = 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), LiNi x Co y Mn z O2 (where 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2 and x + y + z = 1), LiNi x Co y Al z O2 (where 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2 and x + y + z = 1), LiNi x Co y Mn z Al w O2 (where 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, 0 < w ≤ 0.2, and x + y + z + w = 1), Li a Co x M y O 2-b A b (where 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, and x + y + z = 1, where M' is cobalt (Co), 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 M1 x M2 y PO 4-b X b (In 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, where M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof, M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof), Li a M3 z PO4 (0.90 ≤ a ≤ 1.1, 0.9 ≤ z ≤ 1.1, where M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof).

[0078] Examples of conductive materials used include carbon black, graphite nanoparticles, natural graphite, artificial graphite, acetylene black, Ketjenblack, carbon fibers, carbon nanotubes, metal powders or fibers such as copper, nickel, aluminum, and silver, or metal tubes, and conductive polymers such as polyphenylene derivatives. However, these materials are not limited to these, and any material usable as a conductive material in the relevant art can be used. In other embodiments, the positive electrode does not include, for example, a separate conductive material.

[0079] As binders, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the aforementioned polymers, and styrene-butadiene rubber polymers are used, and as solvents, N-methylpyrrolidone (NMP), acetone, and water are used, but are not necessarily limited to these; any solvent used in the relevant art can be used.

[0080] It is also possible to further add a plasticizer or pore-forming agent to the positive electrode active material composition to form pores inside the electrode plate.

[0081] The content of the positive electrode active material, conductive agent, binder, and solvent used in the positive electrode is at levels typically used in lithium batteries. Depending on the application and configuration of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

[0082] The binder content of the positive electrode is 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 of the positive electrode is 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.

[0083] (Separator) Next, a separator is provided to be inserted between the positive electrode and the negative electrode.

[0084] Any separator commonly used in lithium batteries can be used. The separator should, for example, have low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. The separator may be selected from, for example, glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in nonwoven or woven form. For lithium-ion batteries, for example, rollable separators such as polyethylene or polypropylene are used, while for lithium-ion polymer batteries, separators with excellent organic electrolyte impregnation capacity are used.

[0085] The separator is manufactured by the following exemplary methods, but is not limited to such methods and may be adjusted according to the required conditions.

[0086] First, a separator composition is prepared by mixing a polymer resin, a filler, and a solvent. The separator composition is then directly coated onto the electrode and dried to form a separator. In another embodiment, the separator composition is cast onto a support and dried, and then the separator film peeled off the support is laminated onto the top of the electrode to form a separator.

[0087] The polymers used in the manufacture of separators are not particularly limited; any polymer used as a binder for electrode plates can be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof can be used.

[0088] (electrolyte) Next, electrolytes are added.

[0089] Electrolytes can be liquid electrolytes, solid electrolytes, gel electrolytes, or combinations thereof.

[0090] The electrolyte is, for example, an organic electrolyte solution. The organic electrolyte solution is produced, for example, by dissolving a lithium salt in an organic solvent.

[0091] Any organic solvent can be used as long as it is used as an organic solvent in the relevant technical field. Examples of organic solvents 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.

[0092] Any lithium salt can be used as long as it is used as a lithium salt in the relevant technical field. Examples of lithium salts include 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 mixtures thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0093] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0094] The solid electrolyte is, for example, an oxide-based solid electrolyte. The oxide-based solid electrolyte is Li 1+x+y Al x Ti2-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 these. Solid electrolytes are fabricated by methods such as sintering. For example, oxide-based solid electrolytes include Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 It is a garnet-type solid electrolyte selected from among (M-doped LLZO, where M = Ga, W, Nb, Ta, or Al, and x is an integer from 1 to 10).

[0095] Sulfide-based solid electrolytes can include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or combinations thereof. Sulfide-based solid electrolyte particles can include Li2S, P2S5, SiS2, GeS2, B2S3, or combinations thereof. Sulfide-based solid electrolyte particles can also be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, sulfide-based solid electrolytes include Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte contains Li2S-P2S5, the mixed molar ratio of Li2S:P2S5 is, for example, also in the range of about 50:50 to about 90:10. Also, Li3PO4, halogens, halogen compounds, 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 ("ThioLISICON"), Li2O - Al2O3 - TiO2 - P2O 5( "LATP") etc. can be used as sulfide solid electrolytes when added to inorganic solid electrolytes of Li2S - P2S5, SiS2, GeS2, B2S3, or combinations thereof. Non-limiting examples of sulfide solid electrolyte materials are 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 or Ga); Li2S - GeS2; Li2S - SiS2 - Li3PO4; and Li2S - SiS2 - Li p MO qIt contains (0 < p < 10, 0 < q < 10, M = P, Si, Ge, B, Al, Ga or In). In connection with this, the sulfide-based solid electrolyte material can be manufactured by treating the raw material starting substances of the sulfide-based solid electrolyte substance (for example, Li2S, P2S5, etc.) by a melt quenching method, a mechanical milling method, etc. Further, a calcination process can be carried out after the said treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or in a mixed state thereof.

[0096] Polymeric solid electrolytes are, for example, electrolytes containing a mixture of lithium salt and polymer, or electrolytes containing polymers having ion-conducting functional groups. Polymeric solid electrolytes are, for example, polymeric electrolytes that do not contain a liquid electrolyte.Polymers contained in polymer solid electrolytes include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-β-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-β-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), and polymethyl methacrylate (PVF). Fluoride), 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) (SPEEK), sulfonated poly(arylene ether ketone ketone) (SPAEKKS), sulfonated poly(aryl ether ketone) Ketone (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate, PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi). +) or a combination thereof, but not limited to these, any material used as a polymer electrolyte in the art is acceptable. Any lithium salt used as a lithium salt in the art is acceptable. Examples of lithium salts include 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) (where x and y are 1 to 20, respectively), LiCl, LiI, or mixtures thereof, etc.

[0097] Gel electrolytes are, for example, gel polymer electrolytes. Gel polymer electrolytes are, for example, electrolytes containing a liquid electrolyte and a polymer, or an organic solvent and a polymer having ionic conductive functional groups. Liquid electrolytes are, for example, ionic liquids, mixtures of lithium salts and organic solvents, mixtures of ionic liquids and organic solvents, or mixtures of lithium salts, ionic liquids and organic solvents. Polymers can be selected from polymers used in solid polymer electrolytes. Organic solvents can be selected from organic solvents used in liquid electrolytes. Lithium salts can be selected from lithium salts used in solid polymer electrolytes. Ionic liquids have a melting point below room temperature and refer to salts that are liquid at room temperature or molten at room temperature, composed only of ions. Ionic liquids include, 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 contain one or more compounds selected from among those containing one or more anions selected from the following. A polymer solid electrolyte can form a gel polymer electrolyte when impregnated into the electrolyte in a lithium battery. The gel electrolyte may further contain inorganic particles.

[0098] (Lithium battery) Referring to Figure 3, a lithium battery 1 according to one embodiment includes a positive electrode 3, the aforementioned negative electrode 2, and a separator 4. The positive electrode 3, negative electrode 2, and separator 4 are wound or folded to form a battery structure 7. The formed battery structure 7 is housed in a battery case 5. An organic electrolyte is injected into the battery case 5 and sealed in a cap assembly 6 to complete the lithium battery 1. The battery case 5 is cylindrical, but is not necessarily limited to such a form; for example, it can be rectangular, thin-film, etc.

[0099] Referring to Figure 4, a lithium battery 1 according to one embodiment includes a positive electrode 3, the aforementioned negative electrode 2, and a separator 4. The separator 4 is positioned between the positive electrode 3 and the negative electrode 2, and the positive electrode 3, negative electrode 2, and separator 4 are wound or folded to form a battery structure 7. The formed battery structure 7 is housed in a battery case 5. It may include electrode tabs 8 that serve as electrical pathways for guiding the current formed in the battery structure 7 to the outside. The lithium battery 1 is completed when an organic electrolyte is injected into the battery case 5 and sealed. The battery case 5 is rectangular, but is not necessarily limited to such a form; for example, it may be cylindrical, thin-film, etc.

[0100] Referring to Figure 5, a lithium battery 1 according to one embodiment includes a positive electrode 3, the aforementioned negative electrode 2, and a separator 4. The separator 4 is placed between the positive electrode 3 and the negative electrode 2 to form the battery structure. After the battery structures 7 are stacked in a bicell structure, they are housed in a battery case 5. It may include electrode tabs 8 that serve as electrical pathways for guiding the current formed in the battery structure 7 to the outside. The lithium battery 1 is completed when the organic electrolyte is injected into the battery case 5 and sealed. The battery case 5 is rectangular, but is not necessarily limited to such a form; for example, it may be cylindrical, thin-film, etc.

[0101] A pouch-type lithium battery corresponds to the lithium batteries shown in Figures 3 to 5, where a pouch is used as the battery case. A pouch-type lithium battery includes one or more battery structures. A separator is placed between the positive and negative electrodes to form the battery structure. After the battery structures are stacked in a bicell structure, they are impregnated with an organic electrolyte, housed in a pouch, and sealed to complete the pouch-type lithium battery. For example, although not shown, the positive electrode, negative electrode, and separator described above may be simply stacked and housed in a pouch in the form of an electrode assembly, or wound into a jelly roll form of an electrode assembly, or folded and then housed in a pouch. Then, the organic electrolyte is injected into the pouch and sealed to complete the lithium battery.

[0102] Lithium batteries have excellent lifespan and high efficiency characteristics, making them suitable for use in electric vehicles (EVs), for example. They are also used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). Furthermore, they are used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0103] Lithium batteries are stacked in multiples to form a battery module, and multiple battery modules form a battery pack. Such battery packs can be used in all devices that require high capacity and high output. For example, they can be used in notebook computers, smartphones, electric vehicles, etc. A battery module includes, for example, multiple batteries and a frame that secures them. A battery pack includes, for example, multiple battery modules and bus bars that connect them. Battery modules and / or battery packs may further include a cooling device. Multiple battery packs are regulated by a battery management system. The battery management system includes battery packs and battery control devices connected to the battery packs.

[0104] [Negative electrode manufacturing method] A method for manufacturing a negative electrode according to another embodiment includes the steps of: providing a negative electrode current collector; providing a negative electrode intermediate layer on the negative electrode current collector; and providing a protective layer on the negative electrode intermediate layer, wherein the negative electrode intermediate layer comprises a mixture of first particles containing a lithium affinity metal and second particles containing carbon elements, and the protective layer comprises a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer. A lithium battery comprising a negative electrode manufactured by such a method provides improved cycle characteristics.

[0105] 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.

[0106] Next, a negative electrode intermediate layer is provided on the negative electrode current collector. The negative electrode intermediate layer can be provided on the negative electrode current collector, for example, by a nanoparticle casting method. The negative electrode intermediate layer can also be provided, for example, by preparing a first slurry by mixing first and second particles with a solvent, and then coating and drying the first slurry on the negative electrode current collector. The first and second particles refer to the negative electrode portion described above. The solvent can be water or an organic solvent. The solvent can be, for example, N,N-dimethylacetamide or N-methylpyrrolidone (NMP), but is not necessarily limited to these; any solvent used in the art can be used.

[0107] Next, a protective layer is provided on the negative electrode intermediate layer. The protective layer can be provided, for example, by mixing the first polymer and the second polymer with a solvent to prepare a second slurry, and then coating and drying the second slurry on the negative electrode intermediate layer. The coating method is not particularly limited and can be performed using a doctor blade or the like. The first polymer and the second polymer refer to the negative electrode portion described above. The solvent can also be an organic solvent. The solvent can be, for example, N,N-dimethylacetamide or N-methylpyrrolidone (NMP), but is not necessarily limited to these; any solvent used in the art can be used.

[0108] The negative electrode manufacturing method may further include the step of introducing a metal layer between the negative electrode intermediate layer and the negative electrode current collector. The metal layer may include, for example, a lithium-affinity metal. The metal layer may include, for example, lithium-affinity metal particles.

[0109] The method for introducing a metal layer between the negative electrode intermediate layer and the negative electrode current collector is the same as the method for introducing the negative electrode intermediate layer. For example, the metal layer may be placed on the negative electrode current collector before providing the negative electrode intermediate layer on the negative electrode current collector. The method for placing the metal layer on the negative electrode current collector is the same as the method for providing the negative electrode intermediate layer on the negative electrode current collector. For example, a metal layer containing lithium-affinity metal particles may be placed on a metal substrate by a nanoparticle casting method. In other embodiments, a laminate may be prepared by coating and drying a binder-free lithium-affinity metal particle composition on a metal substrate.

[0110] The present invention will be explained in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and do not limit the scope of the present invention to them alone.

[0111] (Manufacturing of negative electrodes and lithium metal batteries) Example 1: Cu substrate / negative electrode intermediate layer (Ag+C, 1:3) / protective layer (PVDF+PEO, 9:1) (Negative electrode manufacturing) Ag nanoparticles and carbon black were mixed in a 1:3 weight ratio, and this mixture was added to distilled water so that the weight of the polyacrylic acid binder was 50 wt% relative to the total weight of the solid powder. The mixture was then dispersed overnight at 60°C through stirring using a thinky mixer to prepare the first slurry.

[0112] A first slurry was coated onto a 10 μm thick copper (Cu) current collector using a nanoparticle casting method, and then the solvent was removed at 65°C for 6 hours to introduce a negative electrode intermediate layer.

[0113] Polyvinylidene fluoride (PVDF) (Sigma-Aldrich, average Mw 534,000 by GPC) powder and polyethylene oxide (PEO) powder were added to N-methylpyrrolidone (NMP, 99%, Sigma-Aldrich) in a 9:1 weight ratio. The mixture was then stirred overnight at 60°C using a stirring bar to prepare the second slurry.

[0114] After coating the negative electrode intermediate layer with the second slurry using a doctor blade, the solvent was removed at 60°C for 6 hours to introduce a protective layer.

[0115] We manufactured a negative electrode having a negative electrode current collector / negative electrode intermediate layer / protective layer structure.

[0116] Figure 10 shows a scanning electron microscope image of the cross-section of the manufactured negative electrode.

[0117] As shown in Figure 10, it was confirmed that a double-layer protective layer is provided, with a negative electrode intermediate layer placed on the copper current collector and a protective layer placed on top of the negative electrode intermediate layer.

[0118] The thickness of the negative electrode intermediate layer was 3 μm, and the thickness of the protective layer was 6 μm.

[0119] (Manufacturing of coin cells) A 20 μm thick lithium foil was used as the relative electrode, a polypropylene separator (Celgard 3510) was placed between the relative electrode and the negative electrode, and an electrolyte was injected to fabricate a coin cell.

[0120] As electrolytes, a solution containing 0.6M LiBF4 and 0.6M LiDFOB dissolved in FEC (fluoroethylene carbonate) + DEC (diethyl carbonate) (1:2 volume ratio) was used.

[0121] Example 2: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:3) / protective layer (PVDF + PEO, 8:2) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of PVDF:PEO in the protective layer was changed to 8:2.

[0122] Example 3: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:3) / protective layer (PVDF + PEO, 7:3) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of PVDF:PEO in the protective layer was changed to 7:3.

[0123] Example 4: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:3) / protective layer (PVDF + PEO, 6:4) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of PVDF:PEO in the protective layer was changed to 6:4.

[0124] Example 5: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:3) / protective layer (PVDF + PEO, 5:5) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of PVDF:PEO in the protective layer was changed to 5:5.

[0125] Example 6: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:2) / protective layer (PVDF + PEO, 9:1) The anode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of Ag nanoparticles to carbon black in the anode intermediate layer was changed to 1:2.

[0126] Example 7: Cu substrate / negative electrode intermediate layer (AgNP + C, 1:1) / protective layer (PVDF + PEO, 9:1) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of Ag nanoparticles to carbon black in the negative electrode intermediate layer was changed to 1:1.

[0127] Example 8: Cu substrate / negative electrode intermediate layer (AgNP + C, 2:1) / protective layer (PVDF + PEO, 9:1) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the weight ratio of Ag nanoparticles to carbon black in the negative electrode intermediate layer was changed to 2:1.

[0128] Comparative example 1: Cu base material / protective layer (PVDF+PEO, 9:1) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that a negative electrode intermediate layer was not applied.

[0129] Comparative example 2: Cu base material / first negative electrode intermediate layer (AgNP) / second negative electrode intermediate layer (C) / protective layer (PVDF+PEO, 9:1) The anode and coin cell were manufactured in the same manner as in Example 1, except that instead of introducing a 3:1 mixture of Ag nanoparticles and carbon black onto the anode current collector, a first anode intermediate layer containing Ag nanoparticles and a second anode intermediate layer containing carbon black were applied.

[0130] Comparative example 3: Cu base material / negative electrode intermediate layer (AgNP) / protective layer (PVDF+PEO, 9:1) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the negative electrode intermediate layer contained only Ag nanoparticles and no carbon black.

[0131] Comparative Example 4: Cu substrate / negative electrode intermediate layer (AgNP+C, 1:3) / protective layer (PVDF alone) The negative electrode and coin cell were manufactured in the same manner as in Example 1, except that the protective layer consisted solely of PVDF.

[0132] Evaluation Example 1: Charge / Discharge Test The lithium batteries produced in Examples 1 to 9 and Comparative Examples 1 to 4 were tested at 25°C for a rate of 0.5 mA / cm². 2 With a current density of 1.0 mAh / cm², 2 The capacity was charged with a constant current. Then, during discharge, a discharge rate of 0.1 mA / cm was applied until the voltage reached 1.0 V (vs. Li). 2 It discharged with a constant current.

[0133] This cycle was repeated under the same conditions for 10 cycles.

[0134] A 10-minute stop period was observed after each charge / discharge cycle in all charge / discharge cycles. The results of Example 1 and Comparative Example 1 from the room-temperature charge / discharge experiments are shown in Figures 7 and 8 below. The results of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 1 below. Charge / discharge efficiency is defined by the following formula 1.

[0135] After the 10th cycle, the charge / discharge efficiency and overpotential values ​​are shown in Table 1 below.

[0136] <Formula 1> Charge / discharge efficiency [%] = [Discharge capacity in the Nth cycle / Charge capacity in the Nth cycle] × 100

[0137] [Table 1]

[0138] As shown in Figures 7, 8 and Table 1, the lithium batteries of Examples 1 to 8 showed improved charge and discharge efficiency and reduced overpotential values ​​compared to the lithium batteries of Comparative Examples 1 to 3.

[0139] The improved lifespan characteristics and overpotential reduction effect of the lithium batteries in Examples 1 to 9 were determined to be due to the suppression of side reactions caused by solvent decomposition on the negative electrode surface and the suppression of local current density imbalances, resulting from the presence of a double-layer structure comprising a negative electrode intermediate layer containing AgNP and carbon black, and a protective layer containing PVDF and PEO.

[0140] In the lithium batteries of Comparative Examples 1 to 4, it was determined that the protective layer and the negative electrode intermediate layer failed to effectively suppress side reactions with the solvent and / or local imbalances in current density.

[0141] Although an exemplary embodiment has been described in detail above based on the attached drawings, this original idea is not limited to such an example. It is self-evident to any person with ordinary skill in the art to which this original idea belongs that various modifications or alterations can be derived within the scope of the technical idea described in the claims, and it goes without saying that these also fall within the technical scope of this original idea. [Explanation of symbols]

[0142] 1 Lithium battery 2, 20 negative electrode 3, 10 positive electrode 4 Separators 5 Battery case 6 Cap Assembly 7 Battery structure 8 Electrode Tabs 11 Positive electrode current collector 12 Cathode active material layer 21 Negative electrode current collector 22 Negative electrode intermediate layer 23 Metal layer 24 Protective layer 30 Solid electrolyte layer

Claims

1. Negative electrode current collector and A protective layer disposed on one surface of the negative electrode current collector, It includes a negative electrode interlayer (anode interlayer) disposed between the negative electrode current collector and the protective layer, The protective layer comprises a first polymer containing a high-strength polymer and a second polymer containing an ion-conducting polymer. The negative electrode wherein the negative electrode intermediate layer comprises a mixture of first particles containing a lithium-affinity metal and second particles containing a carbon element.

2. The negative electrode according to claim 1, wherein the lithium affinity metal includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), magnesium (Mg), zinc (Zn), or any combination thereof.

3. The negative electrode according to claim 1, wherein the second particle comprises amorphous carbon, crystalline carbon, or any combination thereof.

4. The negative electrode according to claim 1, wherein the content ratio of the first particle to the second particle is 5:1 to 1:

5.

5. The negative electrode according to claim 1, wherein the negative electrode intermediate layer further comprises a binder.

6. The negative electrode according to claim 1, wherein the thickness of the negative electrode intermediate layer is 0.1 to 5 μm.

7. The negative electrode according to claim 1, wherein the high-strength polymer has a larger elastic modulus than the second polymer.

8. The anode according to claim 1, wherein the high-strength polymer includes a fluorine-based polymer.

9. The negative electrode according to claim 8, wherein the fluorine-based polymer includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl fluoride (PVF), or any combination thereof.

10. The negative electrode according to claim 1, wherein the ion-conducting polymer comprises polyethylene oxide (PEO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyethylene dioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, and polyacetylene or any combination thereof.

11. The negative electrode according to claim 1, wherein the content of the first polymer is greater than or equal to the content of the second polymer.

12. The negative electrode according to claim 1, wherein the protective layer is lithium salt-free and non-porous.

13. The negative electrode according to claim 1, wherein the thickness of the protective layer is 100 nm to 20 μm.

14. The negative electrode according to claim 1, wherein the thickness ratio of the negative electrode intermediate layer to the protective layer is 1:1 to 1:

20.

15. The negative electrode according to claim 1, wherein the negative electrode current collector comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), tin (Sn), lithium (Li), or alloys or assemblies thereof.

16. The negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film. The 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. The negative electrode according to claim 1, 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), tin (Sn), lithium (Li), or an alloy or combination thereof.

17. The negative electrode according to claim 1, further comprising the negative electrode intermediate layer and a metal layer disposed between the negative electrode intermediate layers.

18. The negative electrode according to claim 17, wherein the metal layer is binder-free.

19. Positive electrode and, The negative electrode according to claim 1, A lithium battery comprising an electrolyte disposed between the positive electrode and the negative electrode.

20. The lithium battery according to claim 19, wherein the electrolyte is a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

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