Negative electrode for lithium secondary battery

Abstract

The present disclosure relates to a negative electrode for a lithium secondary battery and a lithium secondary battery comprising same. One embodiment provides a negative electrode for a lithium secondary battery, the negative electrode comprising: a negative electrode current collector; a first lithium host layer disposed on the negative electrode current collector and comprising a first carbon-based lithium host structure having a lithiophilic material coated on at least a portion of the surface thereof; and a second lithium host layer disposed on the first lithium host layer and comprising a second carbon-based lithium host structure, wherein the second lithium host layer has lower electronic conductivity than the first lithium host layer. In addition, an embodiment provides a negative electrode for a lithium secondary battery, the negative electrode comprising a negative electrode current collector, a first lithium host layer disposed on the negative electrode current collector and comprising a first carbon-based lithium host structure doped with a dopant, and a second lithium host layer disposed on the first lithium host layer and comprising a second carbon-based lithium host structure having at least one of a polymer or an oxide ceramic coated on the surface thereof, wherein the dopant includes heteroatoms, and the heteroatoms include any one of nitrogen (N), oxygen (O), phosphorus (P), boron (B), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), germanium (Ge), gallium (Ga), or a combination thereof.

Description

Negative electrode for lithium secondary batteries

[0001] The present disclosure relates to a negative electrode for a lithium secondary battery.

[0002] Recently, accompanied by the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, computers, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is rapidly increasing. Accordingly, research and development to improve the performance of lithium-ion batteries is actively underway.

[0003] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of lithium ion intercalation and deintercalation, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and the negative electrode.

[0004] Currently commercially available lithium secondary batteries mainly use carbon-based negative electrode active materials such as graphite. Carbon-based negative electrode active materials do not change in volume during charging and discharging, so the stability of lithium secondary batteries is high. However, the theoretical electric capacity of graphite is small, at about 372 mAh / g.

[0005] Lithium metal can be used as a negative electrode active material. The theoretical electric capacity of lithium metal is very large, approximately 3,860 mAh / g. During charging and discharging, dendrites can form on the surface of lithium metal due to side reactions with the electrolyte, and as these dendrites grow, they can cause a short circuit between the positive and negative electrodes. Consequently, the lifespan characteristics and thermal stability of lithium metal batteries containing lithium metal are degraded.

[0006] A method is required to improve the lifespan characteristics and thermal stability of lithium metal secondary batteries containing lithium metal.

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

[0008] The problem that the present invention aims to solve is to provide a negative electrode for a lithium secondary battery to solve the above-mentioned problems.

[0009] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0010] One embodiment provides a negative electrode for a lithium secondary battery comprising a negative electrode current collector, a first lithium host layer disposed on the negative electrode current collector and comprising a first carbon-based lithium host structure, and a second lithium host layer disposed on the first lithium host layer and comprising a second carbon-based lithium host structure, wherein the electronic conductivity of the second lithium host layer is lower than that of the first lithium host layer.

[0011] One embodiment provides a negative electrode for a lithium secondary battery comprising a negative electrode current collector, a first lithium host layer disposed on the negative electrode current collector and comprising a first carbon-based lithium host structure doped with a dopant, and a second lithium host layer disposed on the first lithium host layer and comprising a second carbon-based lithium host structure whose surface is coated with at least one of a polymer or an oxide ceramic, wherein the dopant comprises a heteroatom, and said heteroatom comprises any one of nitrogen (N), oxygen (O), phosphorus (P), boron (B), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), germanium (Ge), gallium (Ga), or a combination thereof.

[0012] According to some embodiments of the present disclosure, lithium can be prevented from being electrodeposited on the upper surface of the lithium host layer by the lithium host layer having a double-layer structure in the cathode.

[0013] According to some embodiments of the present disclosure, lithium can be uniformly electrodeposited on the lower portion of the lithium host layer by means of a lithium host layer having a double-layer structure within the cathode.

[0014] According to some embodiments of the present disclosure, a lithium affinity layer is disposed below the lithium host layer so that lithium can be uniformly electrodeposited from the bottom of the negative electrode.

[0015] According to some embodiments of the present disclosure, a three-layer structure composed of a lithium host layer and a lithium affinity layer is introduced so that lithium is uniformly electrodeposited from the bottom of the lithium host layer and lithium is not electrodeposited on the upper surface, thereby preventing the formation and growth of lithium dendrites.

[0016] According to some embodiments of the present disclosure, a lithium secondary battery incorporating a three-layer structure composed of a lithium host layer and a lithium affinity layer having a double-layer structure can mitigate continuous volume change during charging and discharging.

[0017] According to some embodiments of the present disclosure, the lifespan characteristics, stability, and performance of a lithium secondary battery can be improved by introducing a three-layer cathode composed of a lithium host layer and a lithium affinity layer having a double-layer structure.

[0018] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0019] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0020] FIG. 1 is a schematic diagram showing a stacked structure of a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0021] FIG. 2 is a schematic diagram showing a stacked structure of a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0022] Figure 3 is a schematic diagram showing an example of the structure of a second lithium host layer.

[0023] Figure 4 is a schematic diagram showing an example of the structure of a second lithium host layer.

[0024] Figure 5 is a schematic diagram showing an example of the structure of the first lithium host layer.

[0025] FIG. 6 is a schematic diagram showing a stacked structure of a lithium secondary battery including a negative electrode for a lithium secondary battery shown in FIG. 1.

[0026] FIG. 7 is a schematic diagram showing the stacked structure of a lithium secondary battery including the negative electrode for a lithium secondary battery shown in FIG. 2.

[0027] FIG. 8 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0028] FIG. 9 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0029] FIG. 10 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0030] FIG. 11 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0031] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0032] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0033] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0034] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0035] Methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0036] In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof.

[0037] In this specification, the term “combination of these” means a mixture or combination with one or more of the described components, and may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0038] In this specification, the term “and / or” means any combination of one or more items described in relation and all combinations thereof. In this specification, the term “or” means “and / or”.

[0039] In this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is directly above the other part, but also cases where there is another part in between.

[0040] In this specification, terms such as "first," "second," etc., may be used to describe various components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another.

[0041] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0042] In this specification, "alloy" means a mixture of two or more metals.

[0043] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0044] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0045] In this specification, "lithiation" and "to lithiate" refer to the process of adding lithium to a positive electrode active material or a negative electrode active material.

[0046] In this specification, "delithiation" and "to delithiate" refer to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0047] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0048] In this specification, "discharge" and "discharge" refer to the process of removing electrochemical energy from a battery.

[0049] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0050] In this specification, "cathode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0051] In this specification, "lithium host structure" may mean a structure that provides a space in which lithium can be electrodeposited or inserted.

[0052]

[0053] Exemplary embodiments will be described in more detail below.

[0054] In the present disclosure, the lithium secondary battery may be a lithium metal battery in which the positive electrode capacity is greater than the negative electrode capacity, and lithium metal is plated and stripped from the negative electrode during charging and discharging. Alternatively, the lithium secondary battery may be a negative electrode-free secondary battery in which an active material is absent from the negative electrode. Although the present disclosure primarily describes lithium metal secondary batteries or negative electrode-free secondary batteries, it is not limited thereto and may be, for example, a lithium primary battery, and may also be applied to lithium-sulfur batteries, lithium-air batteries, etc.

[0055] Lithium metal batteries have the risk of interfacial instability between the anode and electrolyte and fire caused by uneven electrodeposition of lithium metal or dendrite growth during the charging and discharging process. To solve this, a lithium host with a large surface area capable of storing lithium and high mechanical strength can be introduced into the anode to suppress lithium dendrite growth and volume expansion, thereby improving the stability and lifespan characteristics of the battery.

[0056] Lithium metal batteries undergo continuous volume expansion and contraction during charging and discharging. Even when a protective film is coated on the negative electrode, these volume changes can cause deformation, such as cracks, in the film, making it difficult to improve long-life characteristics. On the other hand, a lithium host provides a physical space capable of accommodating volume changes during charging and discharging. By providing a large surface area, the lithium host can reduce the effective current density received by lithium ions, thereby suppressing dendrite growth.

[0057] However, the lithium host must be properly designed and manufactured. For example, since the lithium host structure does not contain lithium, it lacks a lithium source capable of maintaining a long charge-discharge life; to address this, prelithiation of the lithium host can be attempted. However, it is difficult to selectively fill the appropriate space with lithium in an appropriate amount, so the lithium host may not function adequately. For instance, if the entire lithium host is prelithiated, the lithium host may fail to function as a host because there is no empty space inside, making it unable to accommodate lithium from the anode.

[0058] Alternatively, if the lithium host is not properly designed, lithium ions from the anode may not diffuse to the bottom of the lithium host and may instead be electrodeposited on the top surface of the lithium host. When electrodeposition occurs on the top surface of the lithium host, the diffusion of lithium ions downward is hindered, and subsequent charge-discharge cycles may result in electrodeposition occurring only on the top of the lithium host, thereby failing to achieve effects such as reduced volume expansion and improved lifespan characteristics. Below, a lithium host designed to improve this phenomenon will be described with reference to FIGS. 1 to 5.

[0059] In this disclosure, the sizes and relative sizes of the layers and regions depicted in the drawings may be exaggerated for clarity of description. That is, the sizes depicted in the drawings are for convenience of understanding only and are not limited thereto. Additionally, throughout the specification, the same reference numerals may refer to the same components.

[0060] FIGS. 1 and 2 are schematic diagrams showing a stacked structure of a negative electrode for a lithium secondary battery according to some embodiments of the present disclosure.

[0061] Referring to FIG. 1, a negative electrode (100) for a lithium secondary battery according to one embodiment of the present disclosure may have a structure in which a negative electrode current collector (110), a first lithium host layer (120), and a second lithium host layer (130) are stacked in that order.

[0062]

[0063] Cathode: Cathode current collector

[0064] The negative electrode current collector (110, 210) may not contain a negative electrode active material. Any material constituting the negative electrode current collector (110, 210) that does not react with lithium, that is, a material that does not form an alloy or compound with lithium and has conductivity is possible. The metal substrate is, for example, a metal or an alloy. The metal substrate may be composed of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The electrode current collector may have a shape selected from, for example, a sheet, foil, film, plate, porous body, mesoporous body, through-hole containing body, polygonal ring body, mesh body, foam, and nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0065] The negative current collector comprises, for example, a first metal substrate. The first metal substrate comprises the first metal as a main component or is composed of the first metal. The first metal substrate comprises the first metal as a main component or is composed of the first metal. The content of the first metal included in the first metal substrate is, for example, 90 weight% or more, 95 weight% or more, 99 weight% or more, or 99.9 weight% or more with respect 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, that is, does not form an alloy and / or compound with lithium.

[0066] The first metal may be, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited to these; any metal used as a current collector in the relevant technical field may be used. The first metal substrate may be composed of, for example, one of the metals described above, 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.

[0067] The negative current collector (110, 210) may further include a coating layer (not shown) containing a second metal on a first metal substrate.

[0068] The negative current collector (110, 210) may include, for example, a first metal substrate and a coating layer disposed on the first metal substrate and comprising a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer comprising the second metal is harder than the substrate comprising 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 comprises the second metal. The coating layer may, for example, comprise the second metal as a main component or be composed of the second metal. The content of the second metal included in the coating layer is, for example, 90% by weight or more, 95% by weight or more, 99% by weight or more, or 99.9% by weight or more with respect 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, that is, 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 more, 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 the deterioration of the negative electrode current collector (110, 210). If the Mohs hardness of the second metal is excessively high, processing may not be 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 metals described above, or 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. By having such a difference in Mohs hardness between the first metal and the second metal, the deterioration of the negative current collector (110, 210) can be suppressed more effectively. The coating layer may be a single-layer structure or a multilayer structure of two or more layers. The coating layer may be a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may be 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 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. The coating layer may be deposited on the first metal substrate by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods; any method capable of forming a coating layer in the relevant technical field is possible.

[0069] For example, the negative current collector (110, 210) may have a reduced thickness compared to a conventional negative current collector. Accordingly, the negative according to the present disclosure is distinguished from a conventional electrode comprising a thick film current collector by including, for example, a thin film current collector.

[0070] As a result, the energy density of the lithium metal secondary battery employing such electrodes is increased. The thickness of the negative electrode current collector (110, 210) may be, for example, less than 15 μm, 14.5 μm or less, or 14 μm or less. The thickness of the negative electrode current collector (110, 210) may be, for example, 0.1 μm to 15 μm, 1 μm to 14.5 μm, 2 μm to 14 μm, 3 μm to 14 μm, 5 μm to 14 μm, or 10 μm to 14 μm.

[0071] The negative current collector (110, 210) may have a shape selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a through-hole containing body, a polygonal ring body, a mesh body, a foam, and a nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0072] The negative current collector (110, 210) may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. The negative current collector (110, 210) may have a structure comprising a substrate, wherein the substrate may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. An intermediate layer may be additionally disposed on the metal substrate layer.

[0073] For example, the base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, 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 may melt upon the occurrence of a short circuit, thereby suppressing a sudden increase in current. The base film may be, for example, an insulator.

[0074] The metal substrate layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The metal substrate layer may act as an electrochemical fuse and be cut off in the event of an overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal substrate layer. The metal substrate layer may be plated or deposited on a base film. As the thickness of the metal substrate layer decreases, the limit current and / or maximum current of the negative electrode current collector (110, 210) decreases, thereby improving the stability of the lithium metal secondary battery in the event of a short circuit.

[0075] A lead tab may be added to the metal substrate layer for external connection. The lead tab may be welded to the metal substrate layer or the metal substrate layer / base film laminate by means of ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal substrate layer may melt, thereby electrically connecting the metal substrate layer to the lead tab. To make the weld between the metal substrate layer and the lead tab more robust, a metal chip may be added between the metal substrate layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal substrate layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to the metal chip / metal substrate layer laminate or the metal chip / metal substrate layer / base film laminate by placing the metal chip on the metal substrate layer and then welding it to the lead tab. During welding, the base film, metal layer, and / or metal chip may melt, allowing the metal layer or the metal layer / metal chip laminate to be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal substrate layer. The thickness of the base film may be, for example, 1 µm to 50 µm, 1.5 µm to 50 µm, 1.5 µm to 40 µm, or 1 µm to 30 µm. By having the base film within this thickness range, the weight of the cathode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100° to 300° (Celsius), 100° to 250°, or 100° to 200°. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. To improve the adhesion between the base film and the metal substrate layer, a surface treatment such as corona treatment may be performed on the base film.The thickness of the metal substrate layer may be, for example, 0.01 μm to 3 μm, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. By having the metal substrate layer within this range of thickness, the stability of the cathode can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 μm to 10 μm, 2 μm to 7 μm, or 4 μm to 6 μm. By having the metal piece within this range of thickness, the connection between the metal layer and the lead tab can be performed more easily. By having the cathode current collector (110, 210) with this structure, the weight of the electrode can be reduced and, consequently, the energy density can be improved.

[0076]

[0077] Cathode: Lithium host layer and lithium affinity layer

[0078] The first lithium host layer (120) is disposed on the negative electrode current collector (110) and may include a first carbon-based lithium host structure and pores.

[0079] In one embodiment, at least a portion of the surface of the first carbon-based lithium host structure may be coated with a lithium-affinity material.

[0080] In one embodiment, the first lithium host layer (120) may include a first carbon-based lithium host structure doped with a dopant. The dopant includes a heteroatom, and the heteroatom may include nitrogen (N), oxygen (O), phosphorus (P), boron (B), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), germanium (Ge), gallium (Ga), or a combination thereof. For example, the heteroatom may include nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), or a combination thereof, which have relatively high electronegativity. In this case, as described below, the lithium affinity of the first carbon-based lithium host structure or the first lithium host layer (120) may be greatly improved.

[0081] In one embodiment, the first carbon-based lithium host structure and the second carbon-based lithium host structure may be composed of a carbon-based negative electrode active material into which lithium ions can be intercalated. The first lithium host layer (120) and the second lithium host layer (130) each include the first carbon-based lithium host structure and the second carbon-based lithium host structure, and each may further include a conductive material and / or a binder. The carbon-based negative electrode active material will be described later with reference to FIGS. 3 to 5.

[0082] The second lithium host layer (130) is disposed on the first lithium host layer (120) and may include a second carbon-based lithium host structure and pores. The surface of the second carbon-based lithium host structure may not have a coating material. Alternatively, at least a portion of the surface of the second carbon-based lithium host structure may be coated by at least one of a polymer or an oxide ceramic. The type and characteristics of the coating material will be described later with reference to FIGS. 3 to 5.

[0083] The first lithium host layer (120) or the second lithium host layer (130) may contain 90% to 99% by weight of a negative electrode active material, 0.5% to 5% by weight of a binder, and 0% to 5% by weight of a conductive material.

[0084] The binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. Non-aqueous binders, aqueous binders, dry binders, or combinations thereof may be used as binders.

[0085] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or combinations thereof.

[0086] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0087] When a water-based binder is used as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be used in a mixture. Na, K, or Li may be used as the alkali metal.

[0088] The dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0089] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0090] Referring to FIG. 2, a negative electrode (200) for a lithium secondary battery according to one embodiment may further include a lithium affinity layer (220) disposed between a negative electrode current collector (210) and a first lithium host layer (230). The lithium affinity layer (220) comprises a lithium affinity material, and the lithium affinity material may include a lithium affinity metal, a lithium affinity metal oxide, a lithium affinity metal phosphate, a lithium affinity metal nitride, a lithium affinity metal nitride, a lithium affinity metal carbide, a lithium affinity metal-organic framework, a lithium affinity metal chalcoganeide, or a combination thereof.

[0091] Lithium-affinity metals may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or alloys thereof. Lithium-affinity metal oxides may include gold oxide, platinum oxide, palladium oxide, silicon oxide, silver oxide, aluminum oxide, bismuth oxide, tin oxide, manganese oxide, zinc oxide, or combinations thereof.

[0092] Referring to FIG. 1, a negative electrode (100) for a lithium secondary battery according to one embodiment includes a lithium host layer having a double-layer structure, and the first lithium host layer (120) may have a higher lithium affinity than the second lithium host layer (130). Referring to FIG. 2, in the case of a negative electrode (200) for a lithium secondary battery according to one embodiment, the lithium affinity may be higher in the order of the lithium affinity layer (220), the first lithium host layer (230), and the second lithium host layer (240).

[0093] Referring to FIG. 1, in the case of a negative electrode (100) for a lithium secondary battery according to one embodiment, lithium electrodeposition may occur at a faster rate in the first lithium host layer (120) compared to the second lithium host layer (130). This may occur because a lithium-affinity material is not coated on the surface of the structure within the second lithium host layer (130) compared to the first lithium host layer (120). Alternatively, it may occur because a polymer and / or oxide ceramic with weak electronic conductivity is coated on the surface of the structure within the second lithium host layer (130) compared to the first lithium host layer (120). Alternatively, it may occur because the above-described doping treatment is not applied to the surface of the structure within the second lithium host layer (130) compared to the first lithium host layer (120).

[0094] Referring to FIG. 2, in the case of a negative electrode (200) for a lithium secondary battery according to one embodiment, lithium electrodeposition can occur at a rapid speed in the order of the lithium affinity layer (220), the first lithium host layer (230), and the second lithium host layer (240). The phenomenon of lithium electrodeposition occurring rapidly in the order of the first lithium host layer (230) and the second lithium host layer (240) is the same as the above description of the phenomenon in which lithium electrodeposition occurs at a rapid speed in the first lithium host layer (120) compared to the second lithium host layer (130).

[0095] Additionally, the lithium affinity layer (220) has higher electronic conductivity than the first lithium host layer (230) or the second lithium host layer (240), so lithium ions can be electrodeposited at a high speed, and has lower tortuosity than the first lithium host layer (230) or the second lithium host layer (240), so lithium can be electrodeposited uniformly.

[0096] Referring to FIGS. 1 and 2, in one embodiment, at least a portion of the surface of a structure within the first lithium host layer (120, 230) is coated with a lithium-affinity material, so that lithium is not locally electrodeposited but can be easily electrodeposited uniformly. The larger the area of ​​the lithium-affinity material coated on the surface of the structure within the first lithium host layer (120, 230), the more uniformly lithium can be electrodeposited.

[0097] The first carbon-based lithium host structure of the first lithium host layer (120) can significantly reduce the effective current density by providing sufficient internal space. However, uniform electrodeposition of lithium may still not be induced. The shape of the lithium initially electrodeposited during charging can be determined by the surface characteristics of the first carbon-based lithium host structure. When the surface is modified by a dopant containing heteroatoms, the number of defects in the first carbon-based lithium host increases, providing many interaction sites with lithium. Accordingly, a uniform flow of lithium ions appears on the surface of the first carbon-based lithium host structure with improved lithium affinity, and consequently, dense and uniform lithium electrodeposition can occur.

[0098] The electronic properties of carbon doped with heteroatoms can be changed by varying the type and number of heteroatoms.

[0099] In one embodiment, the doping of the first carbon-based lithium host structure may be single heteroatom doping or codoping. The codoped first carbon-based lithium host structure may have improved lithium affinity. For example, nitrogen (N) and phosphorus (P), nitrogen (N) and oxygen (O), nitrogen (N) and sulfur (S), and nitrogen (N) and boron (B) may be used as codoping atoms. Codoping may be achieved through a simple polymerization and carbonization process of the carbon fiber.

[0100] By doping the first carbon-based lithium host structure with the above-described dopant, the mechanical durability, electrochemical stability, and reversibility of lithium electrodeposition of the first carbon-based lithium host structure can be improved. Accordingly, the charge / discharge life characteristics of a lithium secondary battery including the above-described first lithium host layer (120) can be improved.

[0101] In addition, the lithium affinity of the doped first carbon-based lithium host structure can be improved by doping the first carbon-based lithium host structure with the dopant described above. Accordingly, the lithium affinity of the first lithium host layer (120) can be improved, and by placing the first lithium host layer (120) at the bottom of the negative electrode (100), lithium can be easily inserted and electrodeposited from the bottom of the negative electrode (100).

[0102] The first carbon-based lithium host structure may be composed of a first carbon-based negative electrode active material. The first lithium host layer may include the first carbon-based lithium host structure and may further include a first conductive material and / or a first binder. The above-described dopant may be doped into the first carbon-based lithium host structure or the first carbon-based negative electrode active material. For example, the surface of the first carbon-based lithium host structure may be doped by the dopant.

[0103] By doping the surface of the first carbon-based lithium host structure with a dopant, lithium can be uniformly electrodeposited on the surface of the structure. Additionally, by placing the first carbon-based lithium host structure at the bottom of the negative electrode (100), lithium is uniformly electrodeposited from the bottom of the negative electrode (100), and the phenomenon of lithium electrodeposition on the upper layer or upper surface of the negative electrode (100) can be mitigated.

[0104] The doping content of the dopant is defined as the weight ratio of the dopant to the weight of the first carbon-based lithium host structure. In some embodiments, the dopant comprises heteroatoms that are nitrogen (N), oxygen (O), sulfur (S), or a combination thereof, and the doping content of the dopant may be 1% to 8%, 1% to 7%, 1% to 6%, 1% to 5%, 1% to 4%, 1% to 3%, 1% to 2%, 2% to 8%, 2% to 7%, 2% to 6%, 2% to 5%, 2% to 4%, 2% to 3%, or 5% to 8%. By doping the first carbon-based lithium host structure with a doping content within the ranges described above, lithium can be electrodeposited more uniformly.

[0105] Referring to FIGS. 1 and 2, within the initial cathode, the thickness of the second lithium host layer may be equal to or smaller than the thickness of the first lithium host layer. In one embodiment, the ratio of the thickness of the first lithium host layer (T1) to the thickness of the second lithium host layer (T2) may be 10:1 to 1:1. Alternatively, the ratio of the thickness of the first lithium host layer (T1) to the thickness of the second lithium host layer (T2) may be 10:1 to 10:9, 10:1 to 10:8, 10:1 to 10:7, 10:1 to 10:6, 10:1 to 10:5, 10:1 to 10:4, or 10:1 to 10:3.

[0106] However, this is not limited thereto, and the thickness (T2) of the second lithium host layer may be equal to or smaller than the thickness (T1) of the first lithium host layer. Accordingly, lithium ions may easily pass through the second lithium host layer (130, 240) and reach the first lithium host layer (120, 230) and / or the lithium affinity layer (220), and the high resistance problem caused by the second lithium host layer (130, 240) including a polymer or oxide ceramic may be resolved. In addition, when the ratio of the thickness (T1) of the first lithium host layer to the thickness (T2) of the second lithium host layer is 10:1 to 1:1, the above-described effect may be enhanced.

[0107] In one embodiment, the first lithium host layer (120, 230) comprises a first carbon-based negative electrode active material, a first conductive material, and a first binder, and the second lithium host layer (130, 240) may comprise a second carbon-based negative electrode active material, a second conductive material, and a second binder. The types of the conductive material and binder are as described above.

[0108] The weight ratio of the first conductive material to the total weight of the first carbon-based negative electrode active material and the first binder may be greater than the weight ratio of the second conductive material to the total weight of the second carbon-based negative electrode active material and the second binder. Accordingly, in a double-layer structure, the electronic conductivity of the second lithium host layer (130, 240) is weaker than that of the first lithium host layer (120, 230), so that lithium is electrodeposited first inside the second lithium host layer (130, 240), thereby preventing the phenomenon in which lithium ions are hindered from diffusing downward, i.e., toward the negative electrode current collector (110, 210). Additionally, the phenomenon in which lithium ions are hindered from diffusing downward can be prevented by lithium being electrodeposited first on the upper surface of the second lithium host layer (130, 240).

[0109] In one embodiment, the weight of the first conductive material is 0.3% to 10% of the total weight of the first carbon-based negative electrode active material and the first binder, and the weight of the second conductive material may be 0.2% or less of the total weight of the second carbon-based negative electrode active material and the second binder. In this case, the above-described top electrodeposition phenomenon of lithium can be prevented more effectively.

[0110] Additionally, the composite density of the first lithium host layer (120, 230) may be greater than the composite density of the second lithium host layer (130, 240). The composite density of the first lithium host layer (120, 230) can be calculated as the mass of the first carbon-based negative electrode active material relative to the volume of the first lithium host layer (120, 230). The composite density of the second lithium host layer (130, 240) can be calculated as the mass of the second carbon-based negative electrode active material relative to the volume of the second lithium host layer (130, 240). Accordingly, the passage of lithium ions from the second lithium host layer (130, 240) to the first lithium host layer (120, 230) can occur more easily, and lithium can be electrodeposited more uniformly from the bottom of the first lithium host layer (120, 230).

[0111] In one embodiment, the composite density of the first lithium host layer (120, 230) is 1.8 g / cc to 3 g / cc, and the composite density of the second lithium host layer (130, 240) may be 1.5 g / cc or less. In this case, the uniform bottom electrodeposition effect of lithium described above can be further maximized.

[0112] FIGS. 3 and 4 are schematic diagrams showing some examples of the structure of a second lithium host layer, and FIG. 5 is a schematic diagram showing one example of the structure of a first lithium host layer. FIGS. 3 and 4 are schematic diagrams showing the appearance of region A of FIGS. 1 and 2 before charging. FIG. 5 is a schematic diagram showing the appearance of region B of FIGS. 1 and 2 before charging.

[0113] Referring to FIGS. 3 to 5, the first lithium host layer (120, 230) may include a first carbon-based lithium host structure (LS1), and the second lithium host layer (130, 240) may include a second carbon-based lithium host structure (LS2).

[0114] A carbon-based lithium host structure (LS1, LS2) according to one embodiment may include a porous structure, a non-porous structure, or a combination thereof. The carbon-based lithium host structure (LS1, LS2) may include a particle structure, a sheet structure, a paper structure, a non-woven fabric structure, a woven fabric structure, a foam structure, a mesh structure, or a combination thereof.

[0115] The porous structure may have a pore ratio of 5 vol% to 99 vol%, 10 vol% to 99 vol%, 20 vol% to 99 vol%, or 30 vol% to 99 vol% in the total volume defined by the outer surface of the structure.

[0116] A non-porous structure is a structure that does not substantially contain pores within the structure. A non-porous structure may, for example, contain non-porous particles. A non-porous structure may have a pore ratio of 1 vol% or less, 0.5 vol% or less, or 0.1 vol% or less in the total volume defined by the outer surface of the structure.

[0117] The porous structure may include one or more pores within the structure. The pores may include open pores, closed pores, or a combination thereof.

[0118] The porous structure may include, for example, a microporous structure having pores smaller than 2 nm, a mesoporous structure having pores larger than 2 nm, a macroporous structure having pores larger than 50 nm, or a combination thereof. The pores included in the macroporous structure may include, for example, pores larger than 50 nm, pores larger than 50 nm, pores larger than 500 nm, pores larger than 1 μm, pores larger than 1 μm, pores larger than 10 μm, pores larger than 10 μm, or a combination thereof.

[0119] The carbon-based lithium host structures (LS1, LS2) are lithium host structures having electronic conductivity. The electronic conductivity of the carbon-based lithium host structures (LS1, LS2) is, for example, 1.0 × 10⁻⁶ at 25°C. 3 S / m or more, 1.0X10 4 S / m or more, or 1.0X10 5 It may be more than S / m.

[0120] A carbon-based lithium host structure (LS1, LS2) according to one embodiment may include amorphous carbon, crystalline carbon, porous carbon, non-porous carbon, or a combination thereof. The carbon-based lithium host structure (LS1, LS2) may include graphite, hard carbon, soft carbon, carbon black, acetylene black, furnace black, ketjen black, graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, carbon foam, or a combination thereof.

[0121] The carbon-based lithium host structure (LS1, LS2) may include, for example, a carbon fiber cloth, a carbonized MOF, a carbonized porous MOF, a graphene foam, a carbon nanofiber (CNF), a hollow carbon nanocube, a carbon core / shell array, a porous carbon flake, a carbon rod array, a 3D nanoporous graphene, a crumple graphene ball, a graphene ball containing metal oxide particles, a carbon granule, a carbon fiber framework, a carbon matrix, or a combination thereof.

[0122] A carbon-based lithium host structure (LS1, LS2) according to one embodiment may be an inert lithium host structure that does not react with lithium to form a compound and acts as a conductor for electron transfer and / or a receptacle for receiving electrodeposited lithium. By including an electrochemically inert lithium host structure in the lithium host layer, degradation of the lithium secondary battery due to volume change and / or physical property change during charging and discharging of the lithium host layer can be prevented more effectively. The carbon-based lithium host structure (LS1, LS2) may include, for example, amorphous carbon.

[0123] In one embodiment, the first carbon-based lithium host structure (LS1) and the second carbon-based lithium host structure (LS2) may include graphite. Alternatively, the first carbon-based lithium host structure (LS1) may include hard carbon, and the second carbon-based lithium host structure (LS2) may include graphite.

[0124] Referring to FIGS. 3 to 5, the lithium host layer may further include pores, and the pores may include a first pore (not shown) disposed within a carbon-based lithium host structure (LS1, LS2), a second pore (P) between a plurality of carbon-based lithium host structures (LS1, LS2), or a combination thereof.

[0125] During the charging process of the battery, lithium ions originating from the positive electrode composite layer described later may be electrodeposited on the surface of the carbon-based lithium host structure (LS1, LS2) or on the second pore (P) between the carbon-based lithium host structure (LS1, LS2) to form a lithium metal or a lithium alloy.

[0126] A first carbon-based lithium host structure (LS1) according to one embodiment may include amorphous carbon, and a second carbon-based lithium host structure (LS2) may include crystalline carbon. For example, the first carbon-based lithium host structure (LS1) may include any one of hard carbon, soft carbon, carbon black, acetylene black, furnace black, ketjen black, carbon foam, or a combination thereof. For example, the second carbon-based lithium host structure (LS2) may include any one of graphite, graphene, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, or a combination thereof.

[0127] In one embodiment, the first carbon-based lithium host structure (LS1) may include hard carbon or soft carbon, and the second carbon-based lithium host structure (LS2) may include graphite.

[0128] According to one embodiment, a second lithium host layer (130) may include a second carbon-based lithium host structure (LS2) disposed on a first lithium host layer (120), wherein at least a portion of the surface is coated by at least one of a polymer or an oxide ceramic. Since polymers and oxide ceramics have low electronic conductivity, the second lithium host layer (130) may have lower electronic conductivity than the first lithium host layer (120). During charging, lithium electrodeposition by electronic conduction in the second lithium host layer (130) is limited, and lithium electrodeposition on the upper surface of the second lithium host layer (130) may be limited. Accordingly, lithium ions can easily diffuse to the lower part of the negative electrode.

[0129] Referring to FIG. 3, the second lithium host layer may be composed of a second carbon-based lithium host structure (LS2), a second pore (P) between them, and / or a first pore (not shown) inside the second carbon-based lithium host structure (LS2). The surface of the second carbon-based lithium host structure (LS2) may not have any surface coating treatment.

[0130] The second carbon-based lithium host structure (LS2) may include a second carbon-based negative electrode active material and pores. The second carbon-based lithium host structure (LS2) may include a single second carbon-based negative electrode active material or a plurality of second carbon-based negative electrode active materials. The second carbon-based lithium host structure (LS2) may refer to a structure that provides a space (e.g., closed pores, etc.) in which lithium can be electrodeposited or inserted by a single or a plurality of second carbon-based negative electrode active materials. The second carbon-based lithium host structure (LS2) may include amorphous carbon, crystalline carbon, porous carbon, non-porous carbon, or a combination thereof. For example, it may include graphite, hard carbon, soft carbon, carbon black, acetylene black, furnace black, ketjen black, graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, carbon foam, or a combination thereof.

[0131] The second carbon-based lithium host structure (LS2) may include crystalline carbon. For example, it may include any one of graphite, graphene, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, or a combination thereof.

[0132] Referring to FIG. 4, at least a portion of the surface of the second carbon-based lithium host structure (LS2) may be coated by a coating layer (NC) that limits the electronic conductivity of the second lithium host layer. The coating layer (NC) may be a polymer and / or oxide ceramic with weak or almost no electronic conductivity. In this case, the second pore (P) may be an area surrounded by the coating layer (NC) or the second carbon-based lithium host structure (LS2). The second pore (P) may be filled with lithium metal or a lithium alloy formed during the battery charging and discharging process.

[0133] The polymer that can be used as the coating layer (NC) may be an ionic or non-ionic conductive polymer, and may be a polymer with little or no electronic conductivity. In one embodiment, the polymer that can be used as the coating layer (NC) may include any one of PEO (Polyethylene Oxide), PVDF (Polyvinylidene Fluoride), PVA (Polyvinyl Alcohol), PAN (Polyacrylonitrile), PPV (Poly(p-phenylene vinylene)), PAA (Polyacrylic Acid), PDA (Polydopamine), or a combination thereof.

[0134] In one embodiment, the oxide ceramic that can be used as the coating layer (NC) may include aluminum oxide (Al2O3), titanium dioxide (TiO2), zinc oxide (ZnO), cerium oxide (CeO2), magnesium oxide (MgO), barium oxide (BaO), vanadium oxide (V2O5), calcium oxide (CaO), zirconium oxide (ZrO2), or a combination thereof.

[0135] In one embodiment, when the second lithium host structure (LS2) is coated with an oxide ceramic, the mechanical strength of the second lithium host layer can be improved compared to when it is coated with a polymer. This may be attributed to the fact that the oxide ceramic coating is more dense than the polymer coating. The denser the coating, the more the lithium top electrodeposition limiting effect can be maximized.

[0136] Oxide ceramic coating can be achieved by atomic layer deposition (ALD) or chemical vapor deposition (CVD) techniques. When coating by the atomic layer deposition technique, a coating of uniform thickness is possible even on a second lithium host structure (LS2) with a complex structure or a complex surface, and the coating thickness can be controlled at the nanometer level.

[0137] When coating by chemical vapor deposition, it is possible to apply a coating of uniform thickness even to the complex shape of the surface of the second lithium host structure (LS2).

[0138] In one embodiment, the average thickness (T4) of the oxide ceramic coating layer (NC) coated on the surface of the second carbon-based lithium host structure (LS2) may be 1 nm to 10 nm, 2 nm to 10 nm, 3 nm to 10 nm, 4 nm to 10 nm, 5 nm to 10 nm, 6 nm to 10 nm, 7 nm to 10 nm, 8 nm to 10 nm, 9 nm to 10 nm, 1 nm to 9 nm, 1 nm to 8 nm, 1 nm to 7 nm, 1 nm to 6 nm, 1 nm to 5 nm, 1 nm to 4 nm, 1 nm to 3 nm, and 1 nm to 2 nm.

[0139] Alternatively, the average thickness (T4) of the oxide ceramic coating layer may be 2 nm to 7 nm, 3 nm to 7 nm, 4 nm to 7 nm, 5 nm to 7 nm, or 6 nm to 7 nm.

[0140] Alternatively, the average thickness (T4) of the oxide ceramic coating layer may be 3 nm to 5 nm. By coating with such an average thickness, the effect of preventing lithium electrodeposition on the upper layer or upper surface of the cathode can be further maximized.

[0141] Through the coating layer (NC) described above, lithium ions can smoothly pass between the plurality of second carbon-based lithium host structures (LS2) or through the second pores (P), while minimizing the rate of electrodeposition on the surface of the second carbon-based lithium host structure (LS2) or the upper surface of the second lithium host layer, thereby inducing the lithium ions to be delivered and electrodeposited to the first lithium host layer.

[0142] Referring to FIG. 5, the first lithium host layer may be composed of a first carbon-based lithium host structure (LS1), a second pore (P) between them, and / or a first pore (not shown) inside the first carbon-based lithium host structure (LS1). Additionally, at least a portion of the surface of the first carbon-based lithium host structure (LS1) within the first lithium host layer may be coated with a lithium-affinity material (LP).

[0143] In one embodiment, the lithium affinity material (LP) may comprise amorphous silicon (a-Si), GeSn, WO3, or any combination thereof. The lithium affinity material (LP) may be thinly coated on the surface of a carbon-based anode material, for example, by chemical vapor deposition (CVD).

[0144] For example, silicon is a material that easily alloys with lithium metal, and stress may be applied to the battery due to alloying with lithium that is electrodeposited during charging and discharging. In addition, when silicon is used as a negative electrode, it may undergo significant volume expansion and contraction depending on charging and discharging. Therefore, amorphous silicon can be used as a lithium-affinity material (LP).

[0145] Amorphous silicon can prevent cracks from occurring in the first lithium host layer compared to monocrystalline silicon or polycrystalline silicon. Specifically, when silicon used as a lithium-affinity material (LP) is analyzed by X-ray diffraction (XRD), the Full Width at Half Maximum (FWHM) at the XRD (111) peak can be greater than about 0.8 degrees. A larger FWHM indicates that the atomic arrangement is irregular.

[0146] In one embodiment, a lithium-affinity material (LP) may be coated on at least a portion of the surface of the first carbon-based lithium host structure (LS1). Specifically, the average thickness (T5) of the lithium-affinity material (LP) coated on at least a portion of the surface of the first carbon-based lithium host structure (LS1) may be 10 nm to 3 μm. Alternatively, the average thickness (T5) may be 10 nm to 1 μm, 50 nm to 100 nm, 100 nm to 500 nm, 500 nm to 1 μm, or 1 μm to 3 μm.

[0147] In this case, the second pore (P) may be a region surrounded by a lithium-affinity material (LP) or a first carbon-based lithium host structure (LS1). The second pore (P) may be filled with lithium metal or a lithium alloy formed during the battery charging and discharging process. The second pore (P) may be, for example, an open pore.

[0148] In one embodiment, the first pore of the first carbon-based lithium host structure (LS1) may not include an open pore. Accordingly, a coating of a lithium-affinity material (LP) by chemical vapor deposition may not be formed inside the first carbon-based lithium host structure (LS1).

[0149] In one embodiment, the first carbon-based lithium host structure (LS1) may be doped with a dopant instead of, or together with, a surface coating. The dopant comprises a heteroatom, which may comprise nitrogen (N), oxygen (O), phosphorus (P), boron (B), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), germanium (Ge), gallium (Ga), or a combination thereof. For example, the heteroatom may comprise nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), or a combination thereof, which have relatively high electronegativity. The first carbon-based lithium host doped with the dopant may have an increased number of defects and may provide many interaction sites with lithium, and the lithium affinity of the first carbon-based lithium host structure (LS1) or the first lithium host layer according to the present disclosure may be greatly enhanced.

[0150] FIG. 6 is a schematic diagram showing a stacked structure of a lithium secondary battery including a negative electrode for a lithium secondary battery shown in FIG. 1. FIG. 7 is a schematic diagram showing a stacked structure of a lithium secondary battery including a negative electrode for a lithium secondary battery shown in FIG. 2.

[0151] A lithium secondary battery (600, 700) according to one embodiment of the present disclosure may include a positive electrode (640, 740), a negative electrode (100, 200), and a separator (610, 710). At this time, the negative electrode (100, 200) may be substantially the same as the negative electrode for a lithium secondary battery described above with reference to FIGS. 1 to 5. As shown in FIGS. 6 and 7, the lithium secondary battery (600, 700) may have a structure stacked in the order of a negative electrode (100, 200), a separator (610, 710), and a positive electrode (640, 740).

[0152] In a lithium secondary battery (600, 700) according to one embodiment, the capacity per area (mAh / cm²) of the positive electrode (640, 740) 2 Capacity per area (mAh / cm²) due to lithium insertion in the first lithium host layer (120, 230) and the second lithium host layer (130, 240) for ) 2 The ratio of ) may be less than 1. In this case, the capacity per area (mAh / cm²) of the positive electrode (640, 740) 2 ) is the capacity per area (mAh / cm²) of the positive composite layer (620, 720). 2 It may mean ). The capacity per area may vary depending on the type and loading amount of the carbon-based negative and positive active materials.

[0153] According to this design, lithium can be electrodeposited and desorbed within the negative electrode (100, 200) during charging and discharging. In one embodiment, the capacity per area (mAh / cm²) of the positive electrode (640, 740) 2 Capacity per area (mAh / cm²) due to lithium insertion in the first lithium host layer (120, 230) and the second lithium host layer (130, 240) for ) 2 The ratio of ) may be about 0.05 to 0.4, 0.1 to 0.4, 0.2 to 0.4, 0.3 to 0.4, or 0.28 to 0.35.

[0154] Additionally, the total thickness of the first lithium host layer (120) and the second lithium host layer (130) may be thinner than the thickness of the positive composite layer (620). Even when a lithium affinity layer (220) is added, the total thickness of the first lithium host layer (230) and the second lithium host layer (240) may be thinner than the thickness of the positive composite layer (720).

[0155] In the present disclosure, a lithium secondary battery (600, 700) can be driven through a process in which lithium metal is electrodeposited and detached.

[0156] Referring to FIG. 6, during the charging process, lithium ions originating from the positive composite layer (620) may be inserted in an ionic state into the first carbon-based lithium host structure of the first lithium host layer (120) and into the second carbon-based lithium host structure of the second lithium host layer (130). Additionally, during the charging process, lithium ions originating from the positive composite layer (620) may be electrodeposited on the surface of the first carbon-based lithium host structure or lithium-affinity material of the first lithium host layer (120), and on the surface of the second carbon-based lithium host structure or coating layer of the second lithium host layer (130) to form lithium metal. Furthermore, during the charging process, lithium ions originating from the positive composite layer (620) may have a stronger tendency to be electrodeposited first within the first lithium host layer (120) than within the second lithium host layer (130).

[0157] During the discharge process, lithium ions inserted into the carbon-based lithium host structure are detached and move to the positive composite layer (620), and lithium metal electrodeposited on the surface of the carbon-based lithium host structure, lithium-affinity material, or coating layer is detached and can move to the positive composite layer (620) in the form of lithium ions.

[0158] Referring to FIG. 7, during the charging process, lithium ions originating from the positive composite layer (720) may be inserted in an ionic state into the first carbon-based lithium host structure of the first lithium host layer (230) and into the second carbon-based lithium host structure of the second lithium host layer (240). Additionally, during the charging process, lithium ions originating from the positive composite layer (720) may be electrodeposited on the surface of the first carbon-based lithium host structure or lithium-affinity material of the first lithium host layer (230), and on the surface of the second carbon-based lithium host structure or coating layer of the second lithium host layer (240) to form lithium metal. Furthermore, during the charging process, lithium ions originating from the positive composite layer (720) may have a stronger tendency to be electrodeposited first within the first lithium host layer (230) than within the second lithium host layer (240). This tendency may be stronger by including more lithium affinity layer (220) than the lithium secondary battery (600) described with reference to FIG. 6.

[0159] During the discharge process, lithium ions inserted inside the carbon-based lithium host structure are detached and move to the positive composite layer (720), and lithium metal electrodeposited on the surface of the carbon-based lithium host structure, lithium-affinity material, or coating layer is detached and can move to the positive composite layer (720) in the form of lithium ions.

[0160] As described above, during the charging process of the battery, lithium ions may be electrodeposited on the surface of the carbon-based lithium host structure or on the second pore (e.g., P in FIGS. 3 to 5) between the carbon-based lithium host structures to form a lithium metal or a lithium alloy. Additionally, the lithium metal or lithium alloy may be electrodeposited uniformly from the bottom of the negative electrode (100, 200), and may have a relatively weak tendency to be electrodeposited first within the second lithium host layer (130, 240) or to be electrodeposited on the upper surface of the second lithium host layer (130, 240) compared to the first lithium host layer (120, 230).

[0161] A lithium secondary battery (600, 700) according to one embodiment may further include a lithium metal or lithium alloy disposed in at least a portion of the interior of a lithium host layer (120, 130, 230, 240) after charging. The lithium metal or lithium alloy may be disposed on the surface of a carbon-based lithium host structure constituting the interior of the lithium host layer (120, 130, 230, 240).

[0162] A lithium secondary battery according to one embodiment may further include lithium ions inserted into at least a portion of the lithium host layer (120, 130, 230, 240) after charging. Specifically, the lithium ions may be inserted in an ionic state within a carbon-based lithium host structure. The lithium ions may include ions derived from the positive electrode composite layer (620, 720) or ions derived from the electrolyte during charging.

[0163] As described above, a metal layer composed of lithium metal or lithium alloy disposed in at least a portion of the interior of the lithium host layer (120, 130, 230, 240) may include plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The metal layer may include non-fibrous lithium, non-needle lithium, plate lithium, or any combination thereof. The lithium alloy contains lithium and a first metal, and the first metal may include indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), cesium (Cs), sodium (Na), potassium (K), calcium (Ca), yttrium (Y), bismuth (Bi), tantalum (Ta), hafnium (Hf), barium (Ba), vanadium (V), strontium (Sr), lanthanum (La), or a combination thereof.

[0164]

[0165] anode

[0166] The positive electrode (640, 740) includes a positive electrode current collector (630, 730) and a positive electrode composite layer (620, 720), and the positive electrode composite layer (620, 720) may be disposed on the positive electrode current collector (630, 730).

[0167]

[0168] Positive: Positive current collector

[0169] The positive current collector (630, 730) may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0170] According to one embodiment, the positive current collector (630, 730) may include aluminum (Al).

[0171] For example, the positive current collector (630, 730) may include a base film and a metal substrate layer disposed on one or both sides of the base film, in the same way as the negative current collector (110, 210) described above.

[0172]

[0173] Anode: Anode composite layer

[0174] The positive composite layer (620, 720) may include a positive active material and may further include a conductive material and / or a binder. For example, the positive active material may include LiMO2 (M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof), LFP, LMFP, LiM2O4 (M is Ti, V, Mn or a combination thereof) or a combination thereof.

[0175] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used. The composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0176] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O 4-c Dc (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni 1-b-c Mn b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

[0177] In the chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is Mn, Al, or a combination thereof.

[0178] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in a lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel cathode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0179] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 1:

[0180]

[0181] <Chemical Formula 1>

[0182] Li a Ni x Co y M z O 2-b A b

[0183]

[0184] In Chemical Formula 1, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0≤y≤0.3, 0 <z≤0.3, x+y+z=1, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다.

[0185] In Chemical Formula 1, for example, 0.7≤x<1, 0 <y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.2, 0<z≤0.2, 0.83≤x<0.97, 0<y≤0.15, 0<z≤0.15, 또는 0.85≤x<0.95, 0<y≤0.1, 0<z≤0.1일 수 있다.

[0186] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulas 1-1 and 1-2:

[0187]

[0188] <Chemical Formula 1-1>

[0189] LiNi x Co y Mn z O2

[0190]

[0191] In Chemical Formula 1-1, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다.

[0192]

[0193] <Chemical Formula 1-2>

[0194] LiNi x Co y Al z O2

[0195]

[0196] In Chemical Formula 1-2, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.8≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.82≤x≤0.95, 0<y≤0.15, 0<z≤0.15이다. 예를 들어, 0.85≤x≤0.95, 0<y≤0.1, 0<z≤0.1이다.

[0197] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04O2 , LiNi 0.8 Co 0.15 Mn 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02O2 , LiNi 0.8 Co 0.15 Al 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0198] For example, the positive electrode active material may be one having a coating layer on the surface of a lithium transition metal oxide, or a mixture of a lithium transition metal oxide and a lithium transition metal oxide having a coating layer may be used.

[0199] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0200] For example, the compound forming the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. For the coating layer formation process, any coating method may be used as long as the coating can be applied to the lithium transition metal oxide using the coating elements in a manner that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.).

[0201] For example, the anode may additionally include an additive that can serve as a sacrificial anode.

[0202] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive composite layer (620, 720), and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive composite layer (620, 720).

[0203] The binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0204] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0205]

[0206] separator

[0207] A separator (610, 710) may be placed between an anode (640, 740) and a cathode (100, 200). A separator (610, 710) may be placed between an anode composite layer (620, 720) and a second lithium host layer (130, 240). As the separator (610, 710) according to one embodiment, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc. may be used.

[0208] The separator (610, 710) may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0209] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0210] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0211] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0212] Organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0213]

[0214] electrolytes

[0215] The lithium secondary battery (600, 700) further includes an electrolyte (not shown), and the electrolyte may be injected into a case to impregnate the stacked structure. Alternatively, the electrolyte may be placed between the positive electrode composite layer (620, 720) and the separator (710, 610). Alternatively, the electrolyte may be placed between the second lithium host layer (130, 240) and the separator (710, 610).

[0216] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0217] The electrolyte is, for example, an organic electrolyte. The organic electrolyte is prepared, for example, by dissolving a lithium salt in an organic solvent. Any organic solvent used as an organic solvent in the relevant technical field may be used.

[0218] An organic electrolyte is prepared, for example, by dissolving a lithium salt in an organic solvent. For example, the organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0219] Carbonate-based solvents such as fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) may be used.

[0220] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0221] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0222] Cyclohexanone and the like can be used as ketone-based solvents. Ethyl alcohol and isopropyl alcohol and the like can be used as alcohol-based solvents, and nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group) and amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes and the like can be used as aprotic solvents.

[0223] Organic solvents are, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, - 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.

[0224] Any lithium salt used as a lithium salt in the relevant technical field is also acceptable. Examples of lithium salts include LiDFOB, LiTFSI, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1 The lithium salts are 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.

[0225] Solid electrolytes are, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0226] 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 Tiy 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 It is one or more selected from (M = Te, Nb, or Zr, where x is an integer from 1 to 10). Solid electrolytes are produced by sintering methods, etc. For example, oxide-based solid electrolytes include Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a MaO 12 It is 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).

[0227] Sulfide-based solid electrolytes may comprise, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or combinations thereof. Sulfide-based solid electrolyte particles may comprise Li2S, P2S5, SiS2, GeS2, B2S3, or combinations thereof. Sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles have high lithium ion conductivity compared to other inorganic compounds. For example, sulfide-based solid electrolytes comprise Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte comprises Li2S-P2S5, the mixed molar ratio of Li2S to P2S5 may be, for example, in the range of about 50:50 to about 90:10. Additionally, 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 An inorganic solid electrolyte prepared by adding S4 ("ThioLISICON"), Li2O-Al2O3-TiO2-P2O5 ("LATP"), etc., to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiX (X = halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, 및 Li2S-SiS2-Lip 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.

[0228] In addition, a calcination process may be performed after the above treatment. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0229] A polymeric solid electrolyte is an electrolyte that, for example, contains a mixture of a lithium salt and a polymer, or contains a polymer having ion-conducting functional groups. A polymeric solid electrolyte is, for example, a polymeric electrolyte that does not contain a liquid electrolyte.The polymers included in the polymeric solid electrolyte are, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ketone), SPEEK, sulfonated poly(arylene ether ketone sulfone), SPAEKKS, sulfonated poly(aryl ether ketone, SPAEK), poly[bis(benzimidazobenzisoquinolinones)], SPBIBI), polystyrene sulfonate (PSS), lithium 9,10-diphenylatlasene-2-sulfonate 9,10-diphenylanthracene-2-sulfonate, DPASLi. +It may be ) or a combination thereof, but is not limited thereto, and any that are used as polymer electrolytes in the relevant technical field are permitted. Any lithium salt that can be used as a lithium salt in the relevant technical field is permitted. 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)(x and y are each 1 to 20), LiCl, LiI, or mixtures thereof, etc.

[0230] A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is an electrolyte that includes, for example, a liquid electrolyte and a polymer, or includes an organic solvent and a polymer having ion-conducting functional groups. The liquid electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt in a liquid state at room temperature or a room temperature molten salt that has a melting point below room temperature and consists solely of ions. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4- , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include one or more compounds selected from those containing one or more anions selected from among. A gel polymer electrolyte may be formed by impregnating the polymer solid electrolyte into the electrolyte in a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0231] According to one embodiment, one or more stacked structures of the lithium secondary battery (600, 700) as described above may be stacked or wound and accommodated in a case, and the case may be classified into cylindrical, prismatic, thin film, coin, pin type, etc.

[0232]

[0233] lithium secondary battery

[0234] FIGS. 8 to 11 are perspective views illustrating a lithium secondary battery according to an embodiment of the present disclosure. FIG. 8 is cylindrical, FIG. 9 is prismatic, and FIGS. 10 and 11 are pouch-type batteries. Referring to FIGS. 8 to 11, the lithium secondary battery (1) includes a battery structure (7, electrode assembly) having a separator (4, separator) interposed between a positive electrode (3) and a negative electrode (2), and a case (5) in which the battery structure (7) is housed. The positive electrode (3), the negative electrode (2), and the separator (4) may be impregnated with an electrolyte (not shown). As shown in FIG. 8, the lithium secondary battery (1) may include an assembly (6, sealing member) that seals the case (5). Additionally, in FIG. 9, the lithium secondary battery (1) may include a positive lead tab (3') and a positive terminal (3"), a negative lead tab (2') and a negative terminal (2"). As shown in FIGS. 10 and 11, the lithium secondary battery (1) may include electrode tabs (70), namely a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical passages for inducing current formed in the battery structure (7) to the outside.

[0235] Referring to FIG. 8, a lithium secondary battery (1) according to one embodiment includes the anode (3), the cathode (2), and the separator (4) described above. The anode (3), the cathode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5) and sealed with a cap assembly (6) to complete the lithium secondary battery (1). The case (5) is cylindrical but is not necessarily limited to this shape and may be, for example, prismatic, thin film, etc.

[0236] Referring to FIG. 9, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound, folded, or stacked to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5), cross-linked, and sealed to complete the lithium secondary battery (1). The case (5) is prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc. A positive lead tab (3') and a positive terminal (3") are electrically connected to the positive electrode (3). A negative lead tab (2') and a negative terminal (2") are electrically connected to the negative electrode (2).

[0237] Referring to FIG. 10, a lithium secondary 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 housed in a case (5). It may include an electrode tab (70) that serves as an electrical path for inducing the current formed in the battery structure (7) to the outside. An electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0238] Referring to FIG. 11, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2) and a separator (4) as described above. An electrolyte as described above, including a separator (4), is disposed between the positive electrode (3) and the negative electrode (2) to form a battery structure. For example, the battery structure (7) is stacked in a bicell structure and then housed in a case (5). It may include a positive electrode tab (71) and a negative electrode tab (72) that serve as electrical pathways for inducing current formed in the battery structure (7) to the outside. The electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0239] However, the present invention is not limited to this, and the case (5) may be configured in various shapes such as circular or pouch type. For example, the pouch-type lithium secondary battery corresponds to the lithium secondary battery (1) of FIGS. 9 and 10 in which a pouch is used as the case (5). The pouch-type lithium secondary battery includes one or more battery structures (7). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2) to form the battery structure (7). The battery structure (7) is stacked in a bicell structure, then impregnated with an electrolyte, and then housed and sealed in a pouch to complete the pouch-type lithium secondary battery.

[0240] Specifically, the battery structure (7) including the aforementioned positive electrode (3), negative electrode (2), and separator (4) is simply stacked and contained in a pouch, or wound into a jelly roll shape or folded and contained in a pouch. Subsequently, an electrolyte is injected into the pouch and sealed to complete the lithium secondary battery (1).

[0241] The case (5) may be made of metal such as aluminum, aluminum alloy, nickel-plated steel, or a laminate film or plastic that constitutes the pouch.

[0242] Lithium secondary battery (1) has excellent lifespan characteristics and high rate characteristics, so it is used in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it is used in fields where a large amount of power storage is required. For example, it is used in electric bicycles, power tools, etc.

[0243] A plurality of lithium secondary batteries (1) are stacked to form a battery module, and a plurality of 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. A battery module includes, for example, a plurality of batteries and a frame that holds them.

[0244] A battery pack includes, for example, a plurality of battery modules and a bus bar connecting them. The battery modules and / or battery pack may further include a cooling device. A plurality of 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.

[0245]

[0246] The present invention will be explained in more detail below through the following examples and comparative examples. The following examples are intended only to illustrate the present invention and do not limit the scope of the present invention.

[0247]

[0248] Example 1

[0249] (Cathode manufacturing)

[0250] A copper (Cu) foil with a thickness of 10 μm was prepared as a negative electrode current collector. For the first lithium host layer, hard carbon was used as the negative active material, carbon black as the conductive material, and PVDF as the binder. The surface of the first carbon-based lithium host structure made of hard carbon was coated with amorphous Si using a CVD method. Specifically, the vapor deposition coating was performed by setting the temperature of the CVD substrate to 450°C and flowing SiH4 gas at 100 sccm at 0.5 Torr. The deposition time was adjusted so that the coating thickness of the amorphous Si was 0.5 μm. A mixture of hard carbon, carbon black, and PVDF in a weight ratio of approximately 95:2:3 was applied onto the copper foil, and the first lithium host layer was prepared by vacuum drying at 40°C for 10 hours.

[0251] For the second lithium host layer, hard carbon was used as the negative active material, carbon black as the conductive material, and PVDF as the binder. To wet-coat the surface of the second carbon-based lithium host structure made of hard carbon with PEO, the hard carbon was added to a solution in which PEO was dispersed in NMP (N-Methyl-2-pyrrolidone) and stirred. At this time, the coating thickness of the PEO was set to 1 μm. A slurry mixed with hard carbon, carbon black, and PVDF in a weight ratio of approximately 95:2:3 was applied onto the first lithium host layer, and the second lithium host layer was prepared by vacuum drying at 40 degrees Celsius for 10 hours. At this time, the thickness ratio of the first lithium host layer to the second lithium host layer was applied such that it was 10:1.

[0252] (Anode manufacturing)

[0253] An aluminum (Al) foil with a thickness of 10 μm was prepared as the positive current collector. The positive composite layer was prepared by coating the aluminum foil with a positive composite material mixed with lithium cobalt oxide (LiCoO2) as the positive active material, carbon black as the conductive material, and PVDF as the binder. The positive laminate coated with the above positive composite material on the aluminum foil was vacuum dried at 40°C for 10 hours. The dried laminate was 5 ton·f / cm² 2 The anode composite layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / s and a speed of 5 m / s.

[0254] (Lithium secondary battery manufacturing)

[0255] Referring to Fig. 6, a laminate was prepared by placing a separator between the prepared anode and cathode. A separator with a total thickness of 15 μm was used, in which alumina (Al2O3) was coated on both sides of a polyethylene monolayer. A pouch-type lithium secondary battery was manufactured by placing the laminate into a pouch, injecting an electrolyte, and vacuum sealing it. As the electrolyte, 1.0 M LiPF6 dissolved in a solvent with EC : DEC = 1 : 1 (V : V) was used.

[0256] In addition, parts of the positive and negative current collectors were extended outside the sealed pouch and used as positive and negative terminals.

[0257]

[0258] Example 2

[0259] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the amorphous Si coating thickness of the first lithium host layer was changed to 1 μm and the thickness ratio of the first lithium host layer and the second lithium host layer was changed to 10:2.

[0260]

[0261] Example 3

[0262] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the amorphous Si coating thickness of the first lithium host layer was changed to 0.8 μm, the coating material of the second lithium host layer was changed to PVDF (coating thickness: 1 μm), and the thickness ratio of the first lithium host layer and the second lithium host layer was changed to 10:3.

[0263]

[0264] Example 4

[0265] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the amorphous Si coating thickness of the first lithium host layer was changed to 2 μm, the surface coating of the second lithium host structure of the second lithium host layer was not performed, and the thickness ratio of the first lithium host layer and the second lithium host layer was changed to 10:3.

[0266]

[0267] Example 5

[0268] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the first lithium host layer was changed to GeSn (coating thickness: 2 μm), the coating material of the second lithium host layer was changed to PVDF, and the thickness ratio of the first lithium host layer and the second lithium host layer was changed to 10:3.

[0269]

[0270] Example 6

[0271] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the second lithium host layer was changed to V2O5 (coating thickness: 0.2 μm).

[0272]

[0273] Example 7

[0274] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the second lithium host layer was changed to CeO2 (coating thickness: 0.8 μm) and the thickness ratio of the first lithium host layer to the second lithium host layer was changed to 10:2.

[0275]

[0276] Example 8

[0277] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the second lithium host layer was changed to ZrO2 (coating thickness: 0.2 μm) and the thickness ratio of the first lithium host layer to the second lithium host layer was changed to 10:2.

[0278]

[0279] Comparative Example 1

[0280] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the first lithium host layer was changed to PEO (coating thickness: 1 μm) and the surface coating of the second lithium host structure of the second lithium host layer was not performed.

[0281]

[0282] Comparative Example 2

[0283] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the coating material of the first lithium host layer was changed to ZrO2 (coating thickness: 0.5 μm), the coating material of the second lithium host layer was changed to PEO (coating thickness: 1 μm), and the thickness ratio of the first lithium host layer and the second lithium host layer was changed to 10:2.

[0284]

[0285] Comparative Example 3

[0286] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the surface coating of the first lithium host structure of the first lithium host layer and the surface coating of the second lithium host structure of the second lithium host layer were not performed.

[0287] The above examples and comparative examples are summarized and shown in Table 1 below.

[0288]

[0289] First lithium host layer coating material (thickness) Second lithium host layer coating material (thickness) Thickness between the first and second lithium host layers Example 1 Amorphous Si (0.5 μm) PEO (1 μm) 10 : 1 Example 2 Amorphous Si (1 μm) PEO (1 μm) 10 : 2 Example 3 Amorphous Si (0.8 μm) PVDF (1 μm) 10 : 3 Example 4 Amorphous Si (2 μm) -10 : 3 Example 5 GeSn (2 μm) PVDF (1 μm) 10 : 3 Example 6 Amorphous Si (0.5 μm) V2O5 (0.2 μm) 10 : 1 Example 7 Amorphous Si (0.5 μm) CeO2 (0.8 μm) 10 : 2 Example 8 Amorphous Si (0.5 μm)ZrO2(0.2 μm)10 : 2 Comparative Example 1 PEO(1 μm)-10 : 1 Comparative Example 2 ZrO2(0.5 μm) PEO(1 μm)10 : 2 Comparative Example 3--10 : 1

[0290]

[0291] Evaluation Example 1-1: Life Characteristics Test

[0292] 100 kgf / cm² for each lithium secondary battery prepared according to the examples and comparative examples 2While applying pressure, constant current charging was performed at a rate of 0.2C at a temperature of 45°C for 1 hour until the voltage reached 4.3V, and constant voltage charging was performed while maintaining 4.3V until the current reached 0.05C. Subsequently, a formation step was performed by carrying out one cycle of discharging at a constant current of 0.2C until the voltage reached 3.0V during discharge. For the lithium secondary battery after the formation step was completed, constant current charging was performed at a rate of 0.7C at 25°C until the voltage reached 4.35V (vs. Li), and constant voltage charging was performed while maintaining 4.35V until the current reached 0.025C. Subsequently, a cycle of discharging at a constant current of 1.0C until the voltage reached 2.75V (vs. Li) during discharge was repeated.

[0293] The room temperature capacity retention rate at the Nth cycle is expressed by Equation 1 below. The number of charge / discharge cycles when the room temperature capacity retention rate reaches 80% is shown in Table 2 below.

[0294]

[0295] <Equation 1>

[0296] Room temperature capacity retention rate [%] = [Discharge capacity at Nth cycle / Discharge capacity at 1st cycle] × 100

[0297]

[0298] Evaluation Example 1-2: Discharge Rate Characteristic Test

[0299] The lithium secondary batteries prepared in the examples and comparative examples were subjected to one charge-discharge cycle at 0.2C to verify the 0.2C capacity. Subsequently, 2C charge-discharge was performed. The discharge rate characteristic can be expressed as the ratio of the capacity at 2C discharge to the capacity at 0.2C discharge, i.e., the capacity retention rate (%). The discharge rate characteristic (%) was evaluated in this manner and is shown in Table 2 below.

[0300] Lifespan Characteristics (Cycles) Discharge Rate Characteristics (%) (2C / 0.2C) Example 1 23387 Example 2 23586 Example 3 24185 Example 4 20786 Example 5 18787 Example 6 21286 Example 7 19585 Example 8 19985 Comparative Example 19177 Comparative Example 2 10183 Comparative Example 3 9581

[0301] As shown in Table 2 above, it was confirmed that the lithium secondary batteries of Examples 1 to 8 exhibited superior lifespan characteristics and discharge rate characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 3. This is believed to be due to the introduction of the double-layer structured negative electrode of the present disclosure, which allows lithium to be uniformly electrodeposited from the bottom of the negative electrode, thereby exhibiting improved lifespan characteristics and performance.

[0302] Through the lithium secondary battery of Comparative Example 1, it was confirmed that it is difficult to induce the bottom electrodeposition of lithium when the polymer is coated on the surface of the first lithium host structure of the first lithium host layer rather than the second lithium host structure of the second lithium host layer.

[0303] Through the lithium secondary battery of Comparative Example 2, it was confirmed that it is difficult to induce the bottom electrodeposition of lithium when an oxide ceramic (e.g., ZrO2) is coated on the surface of the first lithium host structure of the first lithium host layer rather than the second lithium host structure of the second lithium host layer.

[0304] Through the lithium secondary battery of Comparative Example 3, it was confirmed that when a negative electrode consisting only of a lithium host layer without a coating material is included, the capacity retention rate and discharge rate characteristics are significantly lower.

[0305]

[0306] Example 9

[0307] (Cathode manufacturing)

[0308] A copper (Cu) foil with a thickness of 10 μm was prepared as the negative electrode current collector. For the first lithium host layer, hard carbon was used as the negative active material, carbon black as the conductive material, and PVDF as the binder. To manufacture hard carbon doped with heteroatoms, sucrose was used as the raw material for the hard carbon. A sucrose solution, in which sucrose was dissolved at 0.5 M in deionized water, was heated and dried in an autoclave at 250°C. Subsequently, it was mixed with a dopant to achieve a heteroatom doping content of 2% and heat-treated in an autoclave at 1300°C. Nitrogen (N) atoms were used as the heteroatoms. LiNO3 was used as the nitrogen dopant. A first lithium host layer was prepared by mixing nitrogen-doped hard carbon, carbon black, and PVDF in a weight ratio of approximately 95:2:3, coating the mixture onto a copper foil, and vacuum drying it at 40 degrees Celsius for 10 hours. At this time, the first lithium host layer was prepared such that the density of the composite containing heteroatom-doped hard carbon, carbon black, and PVDF was 2.0 g / cc.

[0309] For the second lithium host layer, hard carbon was used as the negative active material, carbon black as the conductive material, and PVDF as the binder. To prepare hard carbon coated with Al2O3, sucrose was used as the raw material for the hard carbon. A sucrose solution, in which sucrose was dissolved at 0.5 M in deionized water, was heated and dried in an autoclave at 250°C. Subsequently, Al2O3 was coated onto the prepared hard carbon using the ALD method to produce hard carbon coated with Al2O3. At this time, the coating thickness of Al2O3 was set to 5 nm. The Al2O3-coated hard carbon, carbon black, and PVDF were mixed in a ratio of approximately 97:0.2:2.8, applied onto the first lithium host layer, and vacuum dried at 40°C for 10 hours to produce the second lithium host layer. At this time, a second lithium host layer was prepared such that the density of the composite containing hard carbon, carbon black, and PVDF coated with Al2O3 was 1.34 g / cc.

[0310] (Anode manufacturing)

[0311] An aluminum (Al) foil with a thickness of 10 μm was prepared as a positive current collector. The positive composite layer was prepared by coating the aluminum foil with a positive composite mixed with lithium cobalt oxide (LiCoO2) as the positive active material, carbon black as the conductive material, and PVDF as the binder. The positive laminate coated with the positive composite on the aluminum foil was vacuum dried at 40 degrees Celsius for 10 hours. The dried laminate was cold-roll-pressed at a pressure of 5 ton·f / cm2 and a speed of 5 m / s to flatten the positive composite layer of the laminate.

[0312] (Lithium secondary battery manufacturing)

[0313] Referring to Fig. 4, a laminate was prepared by placing a separator (a single film of polyethylene) between the prepared anode and cathode. The laminate was placed in a pouch, an electrolyte was injected, and then vacuum-sealed to manufacture a pouch-type lithium secondary battery.

[0314] In addition, parts of the positive and negative current collectors were extended outside the sealed pouch and used as positive and negative terminals.

[0315]

[0316] Example 10

[0317] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 3%, and the density of the composite containing hard carbon, carbon black, and PVDF coated with Al2O3 in the second lithium host layer was changed to 1.40 g / cc.

[0318]

[0319] Example 11

[0320] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 3%, the content ratio of hard carbon, carbon black, and PVDF doped with nitrogen atoms in the first lithium host layer was changed to 94:4:2, the content ratio of hard carbon, carbon black, and PVDF coated with Al2O3 in the second lithium host layer was changed to approximately 98:0.1:1.9, the Al2O3 coating thickness of the second lithium host layer was changed to 3 nm, and the density of the composite containing hard carbon, carbon black, and PVDF coated with Al2O3 in the second lithium host layer was changed to 1.45 g / cc.

[0321]

[0322] Example 12

[0323] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 4%, the content ratio of hard carbon, carbon black, and PVDF doped with nitrogen atoms in the first lithium host layer was changed to 94:4:2, the content ratio of hard carbon, carbon black, and PVDF coated with Al2O3 in the second lithium host layer was changed to approximately 98:0.1:1.9, the Al2O3 coating thickness of the second lithium host layer was changed to 3 nm, and the density of the composite containing hard carbon, carbon black, and PVDF coated with Al2O3 in the second lithium host layer was changed to 1.42 g / cc.

[0324]

[0325] Example 13

[0326] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 4%, the content ratio of hard carbon, carbon black, and PVDF doped with nitrogen atoms in the first lithium host layer was changed to 94:4:2, the content ratio of hard carbon, carbon black, and PVDF in the second lithium host layer was changed to approximately 98:0.1:1.9, the density of the composite containing hard carbon, carbon black, and PVDF in the second lithium host layer was changed to 1.41 g / cc, and the coating material of the second lithium host layer was changed to PEO (coating thickness: 1 μm).

[0327]

[0328] Example 14

[0329] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 4%, the content ratio of hard carbon, carbon black, and PVDF doped with nitrogen atoms in the first lithium host layer was changed to 94:4:2, and a lithium affinity layer was disposed between the negative current collector and the first lithium host layer.

[0330]

[0331] Comparative Example 4

[0332] A lithium secondary battery was manufactured in the same manner as in Example 9, except that the doping content of heteroatoms in the first lithium host layer was changed to 9%, the surface coating of the second lithium host structure of the second lithium host layer was not performed, and the density of the composite containing hard carbon, carbon black, and PVDF in the second lithium host layer was changed to 1.77 g / cc.

[0333]

[0334] Comparative Example 5

[0335] A lithium secondary battery was manufactured in the same manner as in Example 9, except that doping was not performed on the first carbon-based lithium host structure of the first lithium host layer.

[0336]

[0337] Comparative Example 6

[0338] A lithium secondary battery was manufactured in the same manner as in Example 9, except that doping was not performed on the first carbon-based lithium host structure of the first lithium host layer, and the coating material of the second lithium host layer was changed to PEO (coating thickness: 1 μm).

[0339]

[0340] Examples 9 to 14 and Comparative Examples 4 to 6 above are summarized and shown in Table 3 below.

[0341]

[0342] Lithium Affinity Layer 1st Lithium Host Layer 2nd Lithium Host Layer Content Non-Doping Content (%) Composition Density (g / cc) Content Non-Coating Layer Thickness Composition Density (g / cc) Example 9-95:2:32 2.097:0.2:2.85 nm (Al2O3) 1.34 Example 10-95:2:33 1.997:0.2:2.85 nm (Al2O3) 1.40 Example 11-94:4:23 2.098:0.1:1.93 nm (Al2O3) 1.45 Example 12-94:4:24 1.998:0.1:1.93 nm (Al2O3) 1.42 Example 13-94:4:24 1.998:0.1:1.91 μm(PEO) 1.41 Example 14 Ag 94:4:2 4 1.997:0.2:2.85 nm (Al2O3) 1.40 Comparative Example 4 - 95:2:3 9 2.197:0.2:2.8 - 1.77 Comparative Example 5 - 95:2:3 - 2.097:0.2:2.85 nm 1.34 Comparative Example 6 - 95:2:3 - 2.097:0.2:2.81 μm(PEO) 1.41

[0343] Evaluation Example 2-1: Life Characteristics Test

[0344] For each lithium secondary battery prepared according to the examples and comparative examples, the room temperature capacity retention rate was measured in the same manner as in Evaluation Example 1-1 above. The number of charge-discharge cycles at which the room temperature capacity retention rate at the Nth cycle reaches 80% is shown in Table 4 below.

[0345]

[0346] Evaluation Example 2-2: Discharge Rate Characteristic Test

[0347] The discharge rate characteristics (%) of the lithium secondary batteries prepared in the examples and comparative examples were evaluated using the same method as in Evaluation Example 2-1 and are shown in Table 4 below.

[0348] Lifespan Characteristics (Cycles) Discharge Rate Characteristics (%) (2C / 0.2C) Example 9 24587 Example 10 23586 Example 11 24185 Example 12 25786 Example 13 22386 Example 14 23989 Comparative Example 4 15381 Comparative Example 5 14182 Comparative Example 6 12580

[0349] As shown in Table 4 above, it was confirmed that the lithium secondary batteries of Examples 9 to 14 exhibited superior lifespan characteristics and discharge rate characteristics compared to the lithium secondary batteries of Comparative Examples 4 to 6. This is thought to be because lithium was uniformly electrodeposited from the bottom of the negative electrode by doping the first lithium host structure and coating the surface of the second lithium host structure with Al2O3 or PEO, resulting in improved lifespan characteristics and performance.

[0350]

[0351] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. Cathode current collector; A first lithium host layer comprising a first carbon-based lithium host structure disposed on the above-mentioned negative current collector, wherein at least a portion of the surface is coated with a lithium-affinity material; and A second lithium host layer disposed on the first lithium host layer and comprising a second carbon-based lithium host structure Includes, A negative electrode for a lithium secondary battery, wherein the electronic conductivity of the second lithium host layer is lower than that of the first lithium host layer.

2. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein at least a portion of the surface of the second carbon-based lithium host structure is coated with at least one of a polymer or an oxide ceramic.

3. In Paragraph 2, The above oxide ceramic comprises any one of aluminum oxide (Al2O3), titanium dioxide (TiO2), zinc oxide (ZnO), cerium oxide (CeO2), magnesium oxide (MgO), barium oxide (BaO), vanadium oxide (V2O5), calcium oxide (CaO), zirconium oxide (ZrO2), or a combination thereof, for a negative electrode for a lithium secondary battery.

4. In Paragraph 2, The above polymer comprises any one of PEO (Polyethylene Oxide), PVDF (Polyvinylidene Fluoride), PVA (Polyvinyl Alcohol), PAN (Polyacrylonitrile), PPV (Poly(p-phenylene vinylene)), PAA (Polyacrylic Acid), PDA (Polydopamine), or a combination thereof, for a negative electrode for a lithium secondary battery.

5. In Paragraph 1, The above lithium-affinity material comprises any one of amorphous silicon (a-Si), GeSn, WO3, or a combination thereof, a negative electrode for a lithium secondary battery.

6. In Paragraph 1, The first carbon-based lithium host structure and the second carbon-based lithium host structure comprise any one of amorphous carbon, crystalline carbon, porous carbon, non-porous carbon, or a combination thereof, for a negative electrode for a lithium secondary battery.

7. In Paragraph 1, A lithium affinity layer disposed between the above-mentioned negative current collector and the above-mentioned first lithium host layer Includes more, The above lithium affinity layer is a lithium affinity metal, a lithium affinity metal oxide, a lithium affinity metal phosphate, a lithium affinity metal nitride, a lithium affinity metal nitride, Li It comprises any one of a lithium-affinity metal carbide, a lithium-affinity metal-organic framework, a lithium-affinity metal chalcoganeide, or a combination thereof, The above lithium-affinity metal includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or alloys thereof, and The above lithium-affinity metal oxide comprises any one of gold oxide, platinum oxide, palladium oxide, silicon oxide, silver oxide, aluminum oxide, bismuth oxide, tin oxide, manganese oxide, zinc oxide, or a combination thereof, for a negative electrode for a lithium secondary battery.

8. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the thickness of the lithium-affinity material coated on at least a portion of the surface of the first carbon-based lithium host structure is 10 nm to 3 μm.

9. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the thickness of the second lithium host layer is equal to or smaller than the thickness of the first lithium host layer.

10. In Paragraph 1, The first lithium host layer comprises a first carbon-based negative electrode active material, a first conductive material, and a first binder, and The second lithium host layer comprises a second carbon-based negative electrode active material, a second conductive material, and a second binder, and A negative electrode for a lithium secondary battery, wherein the weight ratio of the first conductive material to the total weight of the first carbon-based negative electrode active material and the first binder is greater than the weight ratio of the second conductive material to the total weight of the second carbon-based negative electrode active material and the second binder.

11. In Paragraph 1, The first lithium host layer comprises a first carbon-based negative electrode active material, a first conductive material, and a first binder, and The second lithium host layer comprises a second carbon-based negative electrode active material, a second conductive material, and a second binder, and A negative electrode for a lithium secondary battery, wherein the composite density of the first lithium host layer is greater than the composite density of the second lithium host layer.

12. Cathode current collector; A first lithium host layer comprising a first carbon-based lithium host structure disposed on the above-mentioned negative current collector and doped with a dopant; and A second lithium host layer comprising a second carbon-based lithium host structure disposed on the first lithium host layer, wherein at least a portion of the surface is coated by at least one of a polymer or an oxide ceramic. Includes, The above dopant comprises a heteroatom, wherein the heteroatom comprises any one of nitrogen (N), oxygen (O), phosphorus (P), boron (B), sulfur (S), fluorine (F), chlorine (Cl), bromine (Br), germanium (Ge), gallium (Ga), or a combination thereof, for a negative electrode for a lithium secondary battery.

13. In Paragraph 12, The oxide ceramic comprises any one of aluminum oxide (Al2O3), titanium dioxide (TiO2), zinc oxide (ZnO), cerium oxide (CeO2), magnesium oxide (MgO), barium oxide (BaO), vanadium oxide (V2O5), calcium oxide (CaO), zirconia (ZrO2), or a combination thereof, for a negative electrode for a lithium secondary battery.

14. In Paragraph 12, The above polymer comprises any one of PEO (Polyethylene Oxide), PVDF (Polyvinylidene Fluoride), PVA (Polyvinyl Alcohol), or a combination thereof, for a negative electrode for a lithium secondary battery.

15. In Paragraph 12, The first carbon-based lithium host structure and the second carbon-based lithium host structure comprise any one of hard carbon, soft carbon, carbon black, acetylene black, furnace black, Kettjen black, graphene oxide, reduced graphene oxide, carbon foam, graphite, graphene, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, or a combination thereof, for a negative electrode for a lithium secondary battery.

16. In Paragraph 12, It further includes a lithium affinity layer disposed between the above-mentioned negative current collector and the above-mentioned first lithium host layer, and The above lithium affinity layer is a lithium affinity metal, a lithium affinity metal oxide, a lithium affinity metal phosphate, a lithium affinity metal nitride, a lithium affinity metal nitride, Li It comprises any one of a lithium-affinity metal carbide, a lithium-affinity metal-organic framework, a lithium-affinity metal chalcoganeide, or a combination thereof, The above lithium-affinity metal comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or an alloy thereof, A negative electrode for a lithium secondary battery, wherein the lithium-affinity metal oxide comprises any one of gold oxide, platinum oxide, palladium oxide, silicon oxide, silver oxide, aluminum oxide, bismuth oxide, tin oxide, manganese oxide, zinc oxide, or a combination thereof.

17. In Paragraph 12, A negative electrode for a lithium secondary battery, wherein the average thickness of the oxide ceramic coated on the surface of the second carbon-based lithium host structure is 1 nm to 10 nm.

18. In Paragraph 12, A negative electrode for a lithium secondary battery, wherein the doping content of the above dopant is 1% to 8% based on the total weight of the above first carbon-based lithium host structure.

19. In Paragraph 12, The first lithium host layer comprises a first carbon-based negative electrode active material, a first conductive material, and a first binder, and The second lithium host layer comprises a second carbon-based negative electrode active material, a second conductive material, and a second binder, and A negative electrode for a lithium secondary battery, wherein the weight ratio of the first conductive material to the total weight of the first carbon-based negative electrode active material and the first binder is greater than the weight ratio of the second conductive material to the total weight of the second carbon-based negative electrode active material and the second binder.

20. In Paragraph 12, A negative electrode for a lithium secondary battery, wherein the composite density of the first lithium host layer is greater than the composite density of the second lithium host layer.

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