Negative electrode for lithium secondary battery, and lithium secondary battery comprising same

Abstract

The present disclosure relates to a negative electrode for a lithium secondary battery and a lithium secondary battery comprising same, and 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 first particles; and a second lithium host layer disposed on the first lithium host layer and comprising second particles, wherein the first particles comprise a first carbon-based material and an active material forming an alloy with lithium, the surface of the first particles being coated with amorphous carbon, and the second particles comprise a second carbon-based material and an active material forming an alloy with lithium.

Description

Negative electrode for a lithium secondary battery and a lithium secondary battery including the same

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

[0002]

[0003] 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.

[0004] 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.

[0005] Currently available lithium secondary batteries mainly use carbon-based negative electrode active materials such as graphite, but this poses a hurdle to commercialization due to low energy density. As an alternative, research is actively underway on lithium metal batteries that use lithium metal as a negative electrode active material, which has a high electrical capacity of about 3,860 mAh / g.

[0006] However, lithium metal batteries have a fatal problem in that dendrites are formed on the surface of the lithium metal due to side reactions between the lithium metal and the electrolyte during charging and discharging, which can cause a short circuit between the positive and negative electrodes, leading to a decrease in the stability and lifespan characteristics of the lithium metal battery.

[0007] Therefore, there is a need for methods to improve the stability and lifespan characteristics of lithium metal batteries for their commercialization.

[0008] 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.

[0009]

[0010] The problem that the present invention aims to solve is to provide a negative electrode for a lithium secondary battery and a lithium secondary battery including the same to solve the above-mentioned problems.

[0011] 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.

[0012]

[0013] One embodiment of the present disclosure 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 particle, and a second lithium host layer disposed on the first lithium host layer and comprising a second particle, wherein the first particle comprises an active material that forms an alloy with a first carbon-based material and lithium, and the surface is coated with amorphous carbon, and the second particle comprises an active material that forms an alloy with a second carbon-based material and lithium.

[0014] Another embodiment of the present disclosure provides a lithium secondary battery comprising a positive electrode, a negative electrode for a lithium secondary battery as described above, and an electrolyte interposed between the positive electrode and the negative electrode.

[0015]

[0016] According to some embodiments of the present disclosure, lithium electrodeposition on the upper side of the lithium host layer can be minimized by a lithium host layer having a double-layer structure in the cathode, and uniform lithium flux can be induced in the lower direction of the lithium host layer to induce uniform lithium electrodeposition on the lower side of the lithium host layer. Accordingly, the formation and growth of lithium dendrites can be prevented.

[0017] According to some embodiments of the present disclosure, by introducing a three-layer cathode composed of a lithium host layer with a double-layer structure and a porous polymer layer, lithium can be uniformly electrodeposited from the bottom of the lithium host layer and the electrodeposition of lithium on the top of the lithium host layer can be prevented, thereby more effectively preventing the formation and growth of lithium dendrites.

[0018] According to some embodiments of the present disclosure, a lithium secondary battery having a negative electrode composed of a lithium host layer having a double-layer structure can mitigate continuous volume change during charging and discharging.

[0019] 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 negative electrode composed of a lithium host layer having a double-layer structure.

[0020] 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.

[0021]

[0022] 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.

[0023] 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.

[0024] 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.

[0025] FIG. 3 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.

[0026] FIG. 4 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.

[0027] FIG. 5 is a schematic diagram showing the structure of a first particle included in a first lithium host layer according to one embodiment of the present disclosure.

[0028] FIG. 6 is a schematic diagram showing the structure of a second particle included in a second lithium host layer according to one embodiment of the present disclosure.

[0029] FIG. 7 is a schematic diagram showing the structure of a second particle included in a second lithium host layer according to one embodiment of the present disclosure.

[0030] FIG. 8 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0031] FIG. 9 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0032] FIG. 10 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0033] FIG. 11 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0034]

[0035] 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.

[0036] 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.

[0037] 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."

[0038] 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.

[0039] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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”.

[0044] 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.

[0045] 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.

[0046] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0047] In this specification, "alloy" means a mixture of two or more metals.

[0048] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0049] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0050] 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.

[0051] 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.

[0052] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0053] In this specification, "discharge" and "discharge" refer to the process of removing electrochemical energy from a battery.

[0054] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0055] In this specification, "negative electrode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0056] In this specification, "particle" may mean a primary particle (a single particle) or a secondary particle (a particle formed by the aggregation of multiple particles).

[0057] Exemplary embodiments will be described in more detail below.

[0058] 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. Although the present disclosure primarily describes lithium metal 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.

[0059] Lithium metal batteries carry a high risk of fire and interfacial instability between the anode and electrolyte caused by the uneven electrodeposition of lithium metal during the charging and discharging process. Furthermore, lithium metal batteries undergo continuous volume expansion and contraction during charging and discharging; even when a protective film is coated on the anode, these volume changes can cause deformation, such as cracks, in the film, making it difficult to achieve long-life characteristics.

[0060] By introducing a lithium host with high mechanical strength into the negative electrode, which provides a physical space capable of accommodating volume changes that may occur during charging and discharging, the growth of lithium dendrites and the volume expansion phenomenon of the lithium metal battery due to charging and discharging can be suppressed, and the stability and lifespan characteristics of the battery can be improved.

[0061] For example, since lithium host structures do not contain lithium, they lack a lithium source capable of maintaining a long charge-discharge life; to address this, prelithiation of the lithium host can be attempted. However, because it is difficult to fill the lithium host with an appropriate amount of lithium or to selectively fill specific spaces within the lithium host with lithium, the lithium host may not function adequately. For instance, if the entire lithium host of the anode is prelithiated, the lithium host lacks internal empty space and cannot accommodate lithium flowing in from the anode, thus failing to function as a host.

[0062] In addition, lithium ions introduced from the anode may not diffuse to the lower part of the lithium host and may instead be electrodeposited on the upper surface of the lithium host. If electrodeposition occurs on the upper 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 upper part of the lithium host, thereby failing to achieve effects such as reducing volume expansion and improving lifespan characteristics of the lithium metal battery. Below, a lithium host layer with a double-layer structure within the negative electrode designed to prevent such phenomena will be described with reference to FIGS. 1 to 7.

[0063] 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.

[0064] FIGS. 1 to 4 are schematic diagrams showing a stacked structure of a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0065] 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 sequentially stacked. Referring to FIG. 2, a negative electrode (200) for a lithium secondary battery according to one embodiment of the present disclosure may have a structure in which a negative electrode current collector (210), a first lithium host layer (220), a second lithium host layer (230), and a porous polymer layer (240) are sequentially stacked. Referring to FIG. 3, a negative electrode (300) for a lithium secondary battery according to one embodiment of the present disclosure may have a structure in which a negative electrode current collector (310), a metal coating layer (320), a first lithium host layer (330), and a second lithium host layer (340) are sequentially stacked. Referring to FIG. 4, a negative electrode (400) for a lithium secondary battery according to one embodiment of the present disclosure may have a structure in which a negative electrode current collector (410), a metal coating layer (420), a first lithium host layer (430), a second lithium host layer (440), and a porous polymer layer (450) are sequentially stacked.

[0066]

[0067] Cathode: Cathode current collector

[0068] The negative electrode current collector (110, 210, 310, 410) may not include a negative electrode active material. A negative electrode current collector that does not include a negative electrode active material layer may have lithium metal plated onto it by charging. The plated metal layer may include plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The metal layer may include non-fibrous lithium, non-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, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0069] The material constituting the negative electrode current collector (110, 210, 310, 410) can be any material that does not react with lithium, that is, a material that does not form an alloy or compound with lithium and has conductivity. The metal substrate is, for example, a metal or an alloy. The metal substrate may be 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.

[0070] The negative current collector (110, 210, 310, 410) includes, for example, a second metal substrate. The second metal substrate includes the second metal as a main component or is composed of the second metal. The content of the second metal included in the second 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 second metal substrate. The second 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.

[0071] The second 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 second metal substrate may be, for example, composed of one of the metals described above or composed of an alloy of two or more metals. The second metal substrate is, for example, in the form of a sheet or foil.

[0072] The negative current collector (110, 210, 310, 410) may further include a coating layer (not shown) containing a third metal on a second metal substrate.

[0073] The third metal has a higher Mohs hardness than the second metal. That is, since the coating layer containing the third metal is harder than the substrate containing the second metal, deterioration of the second metal substrate can be prevented. The Mohs hardness of the material constituting the second metal substrate is, for example, 5.5 or less. The Mohs hardness of the second 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 second metal may be, for example, 2.0 to 6.0. The coating layer contains the third metal. The coating layer may, for example, contain the third metal as a main component or be composed of the third metal. The content of the third metal contained 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 higher. For example, the Mohs hardness of the third metal is 6.0 or higher, 6.5 or higher, 7.0 or higher, 7.5 or higher, 8.0 or higher, 8.5 or higher, or 9.0 or higher. The Mohs hardness of the third metal may be, for example, 6.0 to 12. If the Mohs hardness of the third metal is excessively low, it may be difficult to suppress the deterioration of the negative current collector (110, 210, 310, 410). If the Mohs hardness of the third metal is excessively high, processing may not be easy. The third metal is, for example, one or more selected from titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh). The coating layer may be composed of, for example, one of the metals described above, or an alloy of two or more metals.The difference in Mohs hardness between the second metal included in the second metal substrate and the third 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 second metal and the third 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, for example, a two-layer structure including a first coating layer and a second coating layer. The coating layer may be, for example, a three-layer structure including a first coating layer, a second coating layer, and a third coating layer. The thickness of the coating layer may be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. 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.

[0074] For example, the negative current collector (110, 210, 310, 410) 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.

[0075] 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, 310, 410) 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, 310, 410) 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.

[0076] The cathode current collector (110, 210, 310, 410) 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.

[0077] The negative current collector (110, 210, 310, 410) 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, 310, 410) includes a substrate, and the substrate may have a structure including, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. An intermediate layer may be additionally disposed on the metal substrate layer.

[0078] For example, the base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. 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.

[0079] 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 upon 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, 310, 410) decreases, thereby improving the stability of the lithium metal secondary battery during a short circuit.

[0080] 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.

[0081]

[0082] Cathode: Lithium host layer

[0083] Referring to FIG. 1, in a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure, a first lithium host layer (120) is disposed on a negative electrode current collector (110) and may include a first particle (not shown). A second lithium host layer (130) is disposed on the first lithium host layer (120) and may include a second particle (not shown). The first particle and the second particle will be described later with reference to FIGS. 5 to 7.

[0084] According to one embodiment of the present disclosure, the ratio of the thickness (T1) of the first lithium host layer (120) to the thickness (T2) of the second lithium host layer (130) may be 1:0.2 to 1:5. Alternatively, the ratio of the thickness (T1) of the first lithium host layer (120) to the thickness (T2) of the second lithium host layer (130) may be 1:0.2 to 1:4, 1:0.2 to 1:3, 1:0.3 to 1:3, 1:0.3 to 1:1, 1:0.4 to 1:1, 1:0.5 to 1:1, 1:0.6 to 1:1, 1:0.7 to 1:1, 1:0.8 to 1:1, or 1:0.9 to 1:1.

[0085] In this case, it may be easy for lithium ions to pass through the second lithium host layer (130) and reach the first lithium host layer (120), and accordingly, uniform lithium electrodeposition may be induced on the first lithium host layer (120), thereby improving the performance and lifespan characteristics of the lithium metal battery. However, the thickness ratio of the first lithium host layer (120) and the second lithium host layer (130) 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. For example, the thickness of the first lithium host layer (120) may be 10 μm to 40 μm, and the thickness of the second lithium host layer (130) may be 2 μm to 40 μm.

[0086] Referring to FIG. 2, a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure may further include a negative electrode current collector (210), a first lithium host layer (220) disposed on the negative electrode current collector (210), a second lithium host layer (230) disposed on the first lithium host layer (220), and a porous polymer layer (240) disposed on the second lithium host layer (230). The porous polymer layer (240) may include a polymer having excellent ion conductivity but weak or almost no electron conductivity. Accordingly, the electron conductivity of the second lithium host layer (230) may be limited due to the porous polymer layer (240). That is, the rate at which lithium ions are electrodeposited on the upper surface of the second lithium host layer (230) is reduced to the minimum while passing smoothly through the second lithium host layer (230), thereby inducing lithium ions to be electrodeposited on the first lithium host layer (220).

[0087] According to one embodiment of the present disclosure, the porous polymer layer (240) may comprise at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polycarbonate (PC), polyimide (PI), polyurethane (PU), polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), and polyetherimide (PEI).

[0088] The porous polymer layer (240) can be formed by electrospinning and may have a three-dimensional network structure. A porous polymer can be dissolved in a solvent to create a polymer solution, and electrospinning can be performed.

[0089] Electrospinning can be performed using a high-voltage electrospinning machine capable of electrospinning porous polymers, using SUS (steel use stainless) as the collector, and can be carried out in a voltage range of 10 kV to 100 kV or 10 kV to 30 kV and a TCD (tip to collector distance) range of 5 cm to 20 cm or 5 cm to 10 cm. In addition, the spinning speed can be carried out under conditions of 0.5 ml / hr to 10 ml / hr.

[0090] A solvent for dissolving a polymer may include, but is not limited to, at least one of chlorinated organic solvents such as chloroform, methylene chloride, carbon tetrachloride, carbon dichloride, trichloroethane, vinyl chloride, dichloroethylene, trichloroethylene, and tetrachloride, aliphatic organic solvents including dimethylacetamide (DMAC), dichloromethane, 1,2-dichloromethane, benzene, toluene, carbon tetrachloride, xylene, tetrahydrofuran, hexane, heptaine, and octane, aromatic organic solvents, ethers, ketones, and esters, and mixtures thereof.

[0091] When preparing a polymer solution, the polymer may be used in an amount of 5% to 25% by weight, 10% to 20% by weight, or 13% to 18% by weight based on the total weight of the polymer solution. If the weight of the polymer is less than the above range, a porous polymer membrane may not be formed, and if it exceeds the above range, a porosity and thickness suitable for a porous polymer layer may not be formed.

[0092] When preparing a polymer solution, the solvent may be used in an amount of 75% to 95% by weight, 80% to 90% by weight, or 82% to 87% by weight based on the total weight of the polymer solution. If the weight of the solvent is less than the above range, a porosity and thickness suitable for a porous polymer membrane may not be formed, and if it exceeds the above range, a porous polymer membrane may not be formed.

[0093] Electrospinning can be performed by connecting a polymer solution to an electrospinning nozzle using a supply device and forming a high electric field (~100 kV) between the nozzle and a collector (e.g., anode) using a high-voltage generator. Fibers are extruded from the high-voltage nozzle and collected on a collector (e.g., anode) located at a predetermined distance, thereby forming a porous polymer layer. The magnitude of the electric field is related to the distance between the nozzle and the collector, and a combination of these relationships is used to facilitate electrospinning. At this time, the electrospinning device used is not particularly limited and can be a commonly used one; methods such as the electro-blown method or centrifugal electrospinning may also be employed.

[0094] According to one embodiment of the present disclosure, the porous polymer layer (240) may have a thickness of 1 μm to 5 μm, 2 μm to 5 μm, 3 μm to 5 μm, or 4 μm to 5 μm. In this case, a uniform flux of lithium ions may be provided from the second lithium host layer (230) toward the first lithium host layer (220), thereby preventing electrodeposition on the upper surface of the second lithium host layer (230) and allowing lithium ions to be uniformly electrodeposited from the bottom of the first lithium host layer (220).

[0095] Referring to FIG. 3, a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure may further include a negative electrode current collector (310), a first lithium host layer (330), and a second lithium host layer (340), in addition to a metal coating layer (320) disposed between the negative electrode current collector (310) and the first lithium host layer (330). Since the metal coating layer (320) contains a lithium-affinity material, lithium can be uniformly electrodeposited on the first lithium host layer (330) facing the metal coating layer (320) without being locally electrodeposited.

[0096] The thickness of the metal coating layer (320) can be formed to be 20 nm to 50 nm. In this case, the above-described effect can be enhanced.

[0097] According to one embodiment of the present disclosure, the metal coating layer (320) may comprise at least one selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), titanium (Ti), nickel (Ni), cobalt (Co), manganese (Mn), magnesium (Mg), palladium (Pd), silicon (Si), aluminum (Al), bismuth (Bi), tin (Sn), copper (Cu) and zinc (Zn).

[0098] The metal coating layer (320) may be formed by, for example, a physical vapor deposition (PVD) or chemical vapor deposition (CVD) method, but is not limited thereto.

[0099] Referring to FIG. 4, a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure may include a structure in which a negative electrode current collector (410), a metal coating layer (420), a first lithium host layer (430), a second lithium host layer (440), and a porous polymer layer (450) are sequentially stacked. The role and characteristics of each layer included in the stacked structure may be the same as those described above.

[0100] With reference to FIGS. 5 to 7, the structure of a first particle included in a first lithium host layer and the structure of a second particle included in a second lithium host layer according to one embodiment of the present disclosure will be described in detail. FIG. 5 is a schematic diagram showing the structure of a first particle included in region A of FIGS. 1 to 4, and FIGS. 6 and / or FIGS. 7 is a schematic diagram showing the structure of a second particle included in region B of FIGS. 1 to 4.

[0101] Referring to FIG. 5, the first particle (500) comprises a first carbon-based material (510) and an active material (520) that forms an alloy with lithium, and its surface may be coated with amorphous carbon (530). Referring to FIG. 6, the second particle (600) may comprise a second carbon-based material (610) and an active material (620) that forms an alloy with lithium. The first particle (500) and the second particle (600) may correspond to secondary particles.

[0102] According to one embodiment of the present disclosure, the first carbon-based material (510) and the second carbon-based material (610) may comprise a porous structure, a non-porous structure, or a combination thereof. The first carbon-based material (510) and the second carbon-based material (610) may comprise 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.

[0103] 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.

[0104] 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.

[0105] The porous structure may include one or more pores within the structure. The pores may include open pores, closed pores, or a combination thereof. However, the first carbon-based material (121) may not include closed pores. This may be to prevent the lithium-affinity material from being formed inside the first carbon-based material (121) when the lithium-affinity material is coated using a chemical vapor deposition (CVD) method or the like.

[0106] The porous structure may include, for example, a microporous structure having pores smaller than 2 nm, a mesoporous structure having pores between 2 nm and 50 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 between 50 nm and 500 nm, pores between 500 nm and 1 μm, pores between 1 μm and 10 μm, pores between 10 μm and 50 μm, or a combination thereof.

[0107] According to one embodiment of the present disclosure, each of the first carbon-based material (510) and the second carbon-based material (610) may comprise at least one selected from the group consisting of 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, fullerene, carbon sheet, and carbon foam. For example, the first carbon-based material (510) may comprise any one of the materials described above, and the second carbon-based material (610) may comprise hard carbon. The second carbon-based material (610) has excellent ion conductivity, but its electron conductivity is equal to or lower than that of the first carbon-based material (510), so it can provide a uniform flux of lithium ions from the second lithium host layer (130) to the first lithium host layer (120). Accordingly, lithium electrodeposition in the second lithium host layer (130) can be minimized, and uniform lithium electrodeposition in the first lithium host layer (120) can be induced.

[0108] According to one embodiment of the present disclosure, an active material (520, 620) that forms an alloy with lithium may include at least one selected from the group consisting of silicon (Si), aluminum (Al), tin (Sn), magnesium (Mg), bismuth (Bi), silver (Ag), antimony (Sb), lead (Pb), and cadmium (Cd).

[0109] Referring to FIGS. 5 and 6, an active material (520, 620) that forms an alloy with lithium can be deposited inside a first carbon-based material (510) and a second carbon-based material (610) to form a first particle (500) and a second particle (600) in the form of a secondary particle, respectively. The secondary particle shape can have a shape that is close to a sphere overall, containing pores inside, and the active material (520, 620) that forms an alloy with lithium is deposited and fills parts of the pores and between the pores of the first carbon-based material (510) and the second carbon-based material (610). Lithium ions can be stored in the pores of the first particle (500) and the second particle (600) that have the secondary particle shape. Since the active material (520, 620) that forms an alloy with lithium is a lithium-affinity material, the first particle (500) and the second particle (600) can accept a relatively larger amount of lithium ions.

[0110] The deposition of the active material (520, 620) that forms an alloy with lithium can be formed, for example, by chemical vapor deposition (CVD). Chemical vapor deposition can be performed at temperatures of 400°C to 900°C, 500°C to 900°C, 600°C to 900°C, and 700°C to 900°C, but is not limited thereto.

[0111] The active material (520, 620) that forms an alloy with lithium may be, for example, silicon (Si). In this case, chemical vapor deposition can be performed using a silane gas, and the silane gas may include at least one selected from the group consisting of silane (SiH4), dichlorosilane (SiH2Cl2), silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), methylsilane (CH3SiH3), disilane (Si2H6), or a combination thereof.

[0112] The weight of the active material (520) forming an alloy with the lithium included in the first particle (500) may be 3% to 20% by weight, 3% to 17% by weight, 3% to 15% by weight, 3% to 10% by weight, 5% to 10% by weight, 7% to 10% by weight, 9% to 10% by weight, 3% to 8% by weight, 3% to 5% by weight, or 3% to 4% by weight relative to the weight of the first carbon-based material (510). The weight of the active material (620) forming an alloy with the lithium included in the second particle (600) may be 3% to 20% by weight, 3% to 17% by weight, 3% to 15% by weight, 3% to 10% by weight, 5% to 10% by weight, 7% to 10% by weight, 9% to 10% by weight, 3% to 8% by weight, 3% to 5% by weight, or 3% to 4% by weight relative to the weight of the second carbon-based material (610). In this case, the first particle (500) and the second particle (600) may accept a relatively larger amount of lithium ions.

[0113] Referring to FIG. 5, the surface of the first particle (500) can be coated with amorphous carbon (530). The amorphous carbon (530) can provide a high-capacity lithium ion storage capacity, which can induce more lithium electrodeposition into the first lithium host layer containing the first particle (500) whose surface is coated with amorphous carbon (530).

[0114] According to one embodiment of the present disclosure, the amorphous carbon (530) may include at least one selected from the group consisting of hard carbon, soft carbon, carbon black, acetylene black, furnace black, ketjen black, graphene oxide, and pitch carbon.

[0115] The weight of the amorphous carbon (530) may be 2% to 20% by weight relative to the total weight of the first carbon-based material (510) included in the first particle (500) and the active material (520) that forms an alloy with lithium. Alternatively, the weight of the amorphous carbon (530) may be 3% to 20% by weight, 4% to 20% by weight, 4% to 15% by weight, 6% to 15% by weight, 8% to 15% by weight, 10% to 15% by weight, 12% to 15% by weight, or 14% to 15% by weight relative to the total weight of the first carbon-based material (510) included in the first particle (500) and the active material (520) that forms an alloy with lithium. Alternatively, the weight of the amorphous carbon (530) may be 2% to 22% by weight, 2% to 20% by weight, 2% to 15% by weight, 2% to 14% by weight, 2% to 12% by weight, 2% to 10% by weight, 2% to 8% by weight, 2% to 6% by weight, or 2% to 4% by weight relative to the total weight of the first carbon-based material (510) included in the first particle (500) and the active material (520) that forms an alloy with lithium.

[0116] In this case, more lithium electrodeposition into the first lithium host layer can be induced.

[0117] The average particle size (D50) based on the volume of the first particle (500) may be 1 μm to 15 μm, 1 μm to 13 μm, 1 μm to 10 μm, 1 μm to 8 μm, 3 μm to 8 μm, 5 μm to 8 μm, 7 μm to 8 μm, 1 μm to 6 μm, 1 μm to 4 μm, or 1 μm to 2 μm.

[0118] Referring to FIG. 6, the surface of the second particle (600) may not include a separate coating layer. Accordingly, lithium electrodeposition in the second lithium host layer compared to the first lithium host layer having a surface coated with amorphous carbon can be minimized, and thus lithium electrodeposition can be uniformly performed at the bottom of the lithium host layer.

[0119] Referring to FIG. 7, the surface of the second particle (600) may be coated with a non-conductive polymer (630). The non-conductive polymer (630) may be an ionic or non-ionic conductive polymer, but may have relatively low electronic conductivity. By coating the surface of the second particle (600) with a non-conductive polymer (630), it is possible to prevent lithium ions from being electrodeposited first on the second lithium host layer containing the second particle (600) rather than on the first lithium host layer.

[0120] According to one embodiment of the present disclosure, the non-conductive polymer (630) may comprise at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyolefin, polyamide, polyester, aramid, acrylic, polycaprolactone, polycarbonate, polyurethane, polystyrene, polyethylene terephthalate, polybenzimidazole, poly(2-hydroxyethyl methacrylate), poly(ether imide), and styrene-butadiene-styrene triblock copolymer (SBS).

[0121] The average particle size (D50) based on the volume of the second particle (600) may be 5 µm to 20 µm, 8 µm to 20 µm, 8 µm to 17 µm, 8 µm to 15 µm, 10 µm to 15 µm, 12 µm to 15 µm, 14 µm to 15 µm, 8 µm to 13 µm, 8 µm to 11 µm, or 8 µm to 9 µm.

[0122] The particle size (D50) ratio of the first particle (500) and the second particle (600) may be 1:2 to 1:3. In this case, uniform electrodeposition of lithium is induced on the lower part of the first lithium host layer, thereby suppressing the growth of dendrites and improving the performance and lifespan of the battery.

[0123] In one embodiment of the present disclosure, the first lithium host layer may further include a first conductive material and a first binder in addition to the first particle (500), and the second lithium host layer may further include a second conductive material and a second binder in addition to the second particle (600).

[0124] 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. The binder may be, for example, a non-conductive binder or a conductive binder. A conductive binder may be, for example, an ion-conductive binder, an electron-conductive binder, or a combination thereof.

[0125] The binder may be, for example, polystyrene sulfonate (PSS), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), polyethylene glycol (PEG), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, and polyacetylene, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyimide (PI), polyamideimide (PAI), carboxymethylcellulose (CMC), polyvinyl chloride (PVC), polyacrylonitrile (PAN), modified polyphenylene oxide (PPO), polyethylene (PE), polypropylene (PP), etc., but is not limited thereto.

[0126] Ion-conducting binders may include polar functional groups. Ion-conducting binders containing polar functional groups may be, for example, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(etheretherketone), sulfonated poly(aryleneetherketoneketone), sulfonated poly(aryletherketone), poly[bis(benzimadazorbenzisoquinolinone), polystyrene sulfonate (PSS), lithium 9,10-diphenylatlasene-2-sulfonate, etc.

[0127] The electronically conductive binder may be, for example, polyacetylene, polythiophene, polypyrrole, poly(p-phenylene), poly(phenylenevinylene), poly(phenylenesulfide), polyaniline, etc.

[0128] 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.

[0129] The weight ratio of the first conductive material to the total weight of the first carbon-based 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 material and the second binder. Accordingly, in a lithium host double layer structure, the electronic conductivity of the second lithium host layer is lower than that of the first lithium host layer, which not only prevents lithium from being electrodeposited first inside the second lithium host layer but also induces the diffusion of lithium ions toward the negative electrode current collector.

[0130] The weight of the first conductive material is 0.3% to 10% of the total weight of the first carbon-based 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 material and the second binder.

[0131] In addition, the total density of the first carbon-based material, the first conductive material, and the first binder may be greater than the total density of the second carbon-based material, the second conductive material, and the second binder. That is, the density of the first composite may be greater than the density of the second composite. Accordingly, lithium ions can move more easily from the second lithium host layer to the first lithium host layer, and lithium can be uniformly electrodeposited from the bottom of the first lithium host layer.

[0132] In one embodiment, the total density of the first carbon-based material, the first conductive material, and the first binder is 1.8 g / cc to 3 g / cc, and the total density of the second carbon-based material, the second conductive material, and the second binder may be 1.5 g / cc or less.

[0133]

[0134] anode

[0135] A positive active material layer is disposed on a positive current collector to form a positive electrode. A positive active material layer is disposed on an electrolyte, and a positive current collector may be disposed on the positive active material layer.

[0136]

[0137] Positive: Positive current collector

[0138] The positive electrode includes a positive electrode current collector. For example, a positive electrode can be prepared by forming a layer of positive electrode active material on the positive electrode current collector.

[0139] For example, the positive current collector 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.

[0140] According to one embodiment of the present disclosure, the anode current collector may include aluminum (Al).

[0141] For example, the positive current collector 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 described above.

[0142]

[0143] Anode: Anode active material layer

[0144] The positive active material layer may include a positive active material, a conductive material, and a binder.

[0145] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. For example, the positive electrode 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. The positive electrode active material may include a layered structure active material, a spinel structure active material, an olivine-based active material, or a combination thereof.

[0146] 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.

[0147] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni 1-b-c Mn b X c O 2-α D α(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

[0148]

[0149] 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.

[0150] 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.

[0151] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 1:

[0152] [Chemical Formula 1]

[0153] Li a Ni x Co y M z O 2-b A b

[0154]

[0155] 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.

[0156] 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.

[0157] 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:

[0158] <Chemical Formula 1-1>

[0159] LiNi x Co y Mn z O2

[0160]

[0161] 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.

[0162]

[0163] <Chemical Formula 1-2>

[0164] LiNi x Co y Al z O2

[0165]

[0166] 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.

[0167] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04O2 , LiNi 0.8 Co 0.15 Mn 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02O2 , LiNi 0.8 Co 0.15 Al 0.05O2 , LiNi 0.8 Co 0.1 Mn0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0168] 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.

[0169] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0170] 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.).

[0171] For example, the anode may additionally include an additive that can serve as a sacrificial anode.

[0172] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, 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 active material layer.

[0173] 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.

[0174] 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.

[0175]

[0176] separator

[0177] A lithium secondary battery according to one embodiment of the present disclosure may further comprise a separator (not shown). The separator may be disposed between a positive active material layer and a second lithium host layer (130, 230, 340, 440).

[0178] As a separator, polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof may be used, and of course, mixed multilayer films such as polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0179] The separator 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.

[0180] 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.

[0181] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0182] 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.

[0183] 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.

[0184]

[0185] electrolytes

[0186] A lithium secondary battery (100, 200, 300, 400) according to one embodiment of the present disclosure includes an electrolyte interposed between a positive electrode and a negative electrode, and the electrolyte may be injected into a case to impregnate the stacked structure. Specifically, the electrolyte may be disposed between a positive active material layer and a separator. Alternatively, the electrolyte may be disposed between a second lithium host layer (130, 230, 340, 440) and a separator.

[0187] The electrolyte may be, for example, a liquid electrolyte, a gel electrolyte, a solid electrolyte, or a combination thereof.

[0188] The electrolyte is, for example, an organic electrolyte. The 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.

[0189] 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.

[0190] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0191] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0192] 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.

[0193] 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, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

[0194] Any lithium salt used as a lithium salt in the relevant technical field is also acceptable. Examples of lithium salts include LiPF6, LiTFSI, LiDFOB, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1The 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.

[0195] 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.

[0196] Crosslinked polymers can be selected from among the polymers used in solid polymer electrolytes. Crosslinked polymers can act as crosslinking agents. That is, by forming a polymer network with a three-dimensional structure, crosslinked polymers can improve mechanical strength and chemical stability while maintaining the ionic conductivity of the gel electrolyte.

[0197] The cross-linked polymer may have a molecular weight of 5,000 g / mol or less. The cross-linked polymer may include, for example, an acrylic monomer having three or more reactive functional groups, a fluorinated acrylic monomer, or a combination thereof.

[0198] Crosslinked polymers can contain two or more reactive double bonds within a single molecule. The cross-linked polymer is a polymerization product of cross-linkable monomers, and the cross-linkable monomers are dipentaerythritol hexaacrylate (DPHA), trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), diethylene glycol diacrylate (DEGDA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol diacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dianol diacrylate (DDA), and dianol dimethacrylate (DDMA), Ethoxylated trimethylolpropane triacrylate (ETPTA), acrylate-functionalized ethylene oxide, butanediol dimethacrylate, ethoxylated neopentyl glycol diacrylate (NPEOGDA), propoxylated neopentyl glycol diacrylate (NPPOGDA), pentaerythritol triacrylate (PETA), ethoxylated propoxylated trimethylolpropane triacrylate (TMPEOTA) / (TMPPOTA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), pentaerythritol tetraacrylate (PETTA), Dipentaerythritol pentaacrylate (DPEPA),It may include at least one selected from the group consisting of ditrimethylol propane tetraacrylate (DTMPTTA), diglycidyl ester, acrylamide, divinylbenzene, and combinations thereof.

[0199] The weight-average molecular weight of the crosslinkable monomer may be 200 to 2,000, 200 to 1,000, for example, 200 to 500. If the weight-average molecular weight is less than 200, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be excessively high, which may restrict the free movement of the lithium salt, and if it is greater than 2,000, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be excessively low, which may reduce the electrolyte blocking ability.

[0200] The cross-linked polymer may be included in an amount of 3 to 50 weight%, 3 to 40 weight%, 3 to 30 weight%, 5 to 30 weight%, or 10 to 30 weight% relative to the total weight of the first gel polymer electrolyte and the second gel polymer electrolyte.

[0201] A polymer solid electrolyte can form a gel polymer electrolyte by impregnating the electrolyte in a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0202] Solid electrolytes are, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0203] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3)O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 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).

[0204] 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.

[0205] 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.

[0206] A polymeric solid electrolyte is, for example, an electrolyte containing a mixture of a lithium salt and a polymer, or 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 ether ketone), SPEEK, sulfonated poly(arylene ether ketone ketone sulfone), SPAEKKS), sulfonated poly(aryl ether ketone, SPAEK), poly[bis(benzimidazobenzisoquinolinones)], SPBIBI), polystyrene sulfonate (PSS), lithium 9,10-diphenylatlasene-2-sulfonate (lithium It may be 9,10-diphenylanthracene-2-sulfonate, DPASLi+) or a combination thereof, but is not limited to these, and any polymer electrolyte used in the relevant technical field is acceptable.Any lithium salt that can be used as a lithium salt in the relevant technical field is acceptable. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C. x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are each 1 to 20), LiCl, LiI, or mixtures thereof, etc.

[0207]

[0208] lithium secondary battery

[0209] A lithium secondary battery according to one embodiment of the present disclosure may include a positive electrode, a negative electrode for a lithium secondary battery according to one embodiment described above, and an electrolyte interposed between the positive electrode and the negative electrode.

[0210] In a lithium secondary battery according to one embodiment of the present disclosure, the capacity per area of ​​the positive electrode (mAh / cm²) 2 Capacity per area (mAh / cm²) due to lithium insertion in the first lithium host layer and the second lithium host layer for ) 2 The ratio of ) can be less than 1. In this case, the capacity per anode area (mAh / cm²) 2 ) is the capacity per area of ​​the positive active material layer (mAh / cm²). 2 It may mean ). The capacity per area may vary depending on the type and loading amount of the first carbon-based material, the second carbon-based material, and the positive active material.

[0211] Accordingly, lithium can be electrodeposited and desorbed within the negative electrode during the charging and discharging of the lithium secondary battery. For example, the capacity per unit area of ​​the positive electrode (mAh / cm²) 2 Capacity per area (mAh / cm²) due to lithium insertion in the first lithium host layer and the second lithium host layer for ) 2 The ratio of ) can be about 0.05 to 0.4 or 0.28 to 0.35.

[0212] In addition, the total thickness of the first lithium host layer and the second lithium host layer may be thinner than the thickness of the positive active material layer.

[0213] A lithium secondary battery according to one embodiment of the present disclosure can be operated through a process in which a lithium metal capable of acting as a negative electrode active material is electrodeposited and deposited.

[0214] During the charging process, lithium ions originating from the positive active material layer can be inserted in an ionic state into the first particle of the first lithium host layer and the second particle of the second lithium host layer. Additionally, during the charging process, lithium ions originating from the positive active material layer may be electrodeposited into the first particle of the first lithium host layer or the second particle of the second lithium host layer to form lithium metal or a lithium alloy. Furthermore, during the charging process, lithium ions originating from the positive active material layer have a strong tendency to be electrodeposited first within the first lithium host layer rather than the second lithium host layer, so the lithium metal or lithium alloy can be uniformly electrodeposited starting from the bottom of the negative electrode.

[0215] During the discharge process, lithium ions inserted into the first lithium host layer and the second lithium host layer are detached and move to the positive active material layer, and lithium metal electrodeposited on the first particle of the first lithium host layer or the second particle of the second lithium host layer is detached and can move to the positive active material layer in the form of lithium ions.

[0216] 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). The lithium secondary battery (1) may include an assembly (6, sealing member) that seals the case (5) as in FIG. 8. 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.

[0217] 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.

[0218] 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).

[0219] 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.

[0220] 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.

[0221] 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. 3 to 6 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.

[0222] 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).

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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.

[0227]

[0228] The present invention will be explained in more detail below through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and the scope of the present invention is not limited thereto.

[0229]

[0230] Example 1

[0231] (Cathode manufacturing)

[0232] 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. Hard carbon, carbon black, and PVDF were mixed in a weight ratio of 95:2:3 and coated onto the copper foil, and the mixture was vacuum dried at 40°C for 10 hours to prepare the first lithium host layer.

[0233] Subsequently, SiH4(g) was deposited on the hard carbon included in the first lithium host layer at a rate of 50 sccm for 50 minutes using a chemical vapor deposition (CVD) method to produce a first particle in the form of a secondary particle. The silicon content deposited on the first particle thus produced was 7 wt% relative to the weight of the hard carbon. Subsequently, the hard carbon was coated on the surface of the first particle as amorphous carbon. The particle size (D50) of the first particle was 5 μm, and the amount of hard carbon coated on the surface was 10 wt% relative to the weight of the first particle (hard carbon and silicon).

[0234] 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. Hard carbon, carbon black, and PVDF were mixed in a weight ratio of 95:2:3 and applied onto the first lithium host layer, and vacuum dried at 40 degrees (Celsius) for 10 hours to prepare the second lithium host layer.

[0235] Subsequently, a second particle in the form of a secondary particle was prepared by depositing SiH4(g) onto the hard carbon included in the second lithium host layer at a rate of 50 sccm for 50 minutes using a chemical vapor deposition (CVD) method. The silicon content deposited on the second particle prepared in this way was 7 wt% relative to the weight of the hard carbon. Subsequently, a PEO polymer was coated on the surface of the second particle. The particle size (D50) of the second particle was 12 μm, and the thickness of the polymer coated on the surface was 1 μm.

[0236] Meanwhile, the thickness ratio of the first lithium host layer and the second lithium host layer was set to 1:1.

[0237] Next, a PVDF solution mixed with 80 wt% PVDF and 20 wt% dimethylformamide (DMF) as a spinning solution was electrospun onto a second lithium host layer to produce a porous polymer layer. The thickness of the porous polymer layer was 2 μm.

[0238] (Anode manufacturing)

[0239] An aluminum (Al) foil with a thickness of 10 μm was prepared as the positive current collector. The positive active material layer was prepared by coating the aluminum foil with a positive composite material consisting of lithium cobalt oxide (LiCoO2) as the positive active material, carbon black as the conductive material, and PVDF as a binder in a weight ratio of 97.5:0.5:2. The thickness of the positive composite material was 45 μm, and its density was 4.2 g / cc. The positive laminate coated with the positive composite material on the aluminum foil was vacuum dried at 40°C for 10 hours. The dried laminate was [distributed as follows] at 5 ton·f / cm² 2 The positive active material layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / s and a speed of 5 m / s.

[0240] (Lithium secondary battery manufacturing)

[0241] A laminate was prepared by placing a separator between the positive and negative electrodes. The laminate was placed in a pouch, and a gel electrolyte was crosslinked and then vacuum-sealed to manufacture a pouch-type lithium secondary battery.

[0242] The gel electrolyte was prepared by the following method. First, 0.6 M LiPF6, 0.3 M LiTFSI, and 0.3 M LiDFOB were added as electrolyte salts to an organic solvent mixed with ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) in a mass ratio of 3:3:4, followed by the addition of 4 mass% of DPHA. Subsequently, the mixed solution was injected into a pouch cell, vacuum sealed, and then heat-treated at 70°C for 3 hours to cure it.

[0243]

[0244] Examples 2 to 10

[0245] As described in Table 1 below, a lithium secondary battery was manufactured in the same manner as in Example 1. For reference, in Example 5, tin (Sn) was used instead of silicon (Si).

[0246]

[0247] Comparative Example 1

[0248] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the manufacturing of the second lithium host layer was omitted.

[0249]

[0250] Comparative Example 2

[0251] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the manufacturing of the first lithium host layer was omitted.

[0252]

[0253] Comparative Example 3

[0254] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a hard carbon coating was omitted on the surface of the first particle in the form of a secondary particle included in the first lithium host layer.

[0255]

[0256] The above examples and comparative examples are summarized and shown in Table 1 below.

[0257]

[0258] [Table 1]

[0259]

[0260]

[0261] Evaluation Example 1: Life Characteristics Test

[0262] Each lithium secondary battery prepared according to the examples and comparative examples at 0.1 mA / cm² at 25°C 2 Constant current charging was performed for 5 hours at a current of . Subsequently, at 0.1 mA / cm² until the voltage reached 1.0 V (vs. Li) during discharge. 2 It was discharged with a constant current. These charge / discharge cycles were repeated under the same conditions. In all charge / discharge cycles, a 10-minute pause was taken after each charge / discharge cycle.

[0263] State of Health (SOH) based on capacity is defined by the following Equation 1. Here, the initial capacity refers to the rated capacity of the initial battery, and the capacity at the Nth cycle refers to the maximum capacity that the battery can provide at the Nth cycle.

[0264]

[0265] [Equation 1]

[0266] SOH [%] = [Capacity at Nth cycle / Initial capacity] × 100

[0267]

[0268] The number of cycles required for the SOH to decrease to approximately 80% is shown in Table 1 below.

[0269]

[0270] Evaluation Example 2: Discharge Rate Characteristic Test

[0271] The lithium secondary batteries prepared in the examples and comparative examples were subjected to one charge and discharge cycle at 2C and 0.2C, and the discharge rate characteristics (%) were evaluated and shown in Table 2 below. The discharge rate characteristics 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 (%).

[0272]

[0273] [Table 2]

[0274]

[0275]

[0276] As shown in Table 2, it was confirmed that the lithium secondary battery according to the example exhibited superior lifespan characteristics and discharge rate characteristics compared to the lithium secondary battery according to the comparative example.

[0277]

[0278] 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.

[0279]

[0280] The negative electrode for a lithium secondary battery and the lithium secondary battery including the same according to the present disclosure can achieve excellent lifespan characteristics and stability by employing a double-layer structure comprising a first lithium host layer including a first particle coated with amorphous carbon and a second lithium host layer including a second particle, thereby inducing uniform electrodeposition of lithium during charging and discharging and suppressing dendrite formation. Such lithium secondary batteries can be industrially applied to various electronic devices and energy storage systems requiring high capacity and high output, such as mobile phones, laptops, and electric vehicles, and can also be utilized in large-scale energy storage devices composed of battery modules and battery packs.

Claims

1. Cathode current collector; A first lithium host layer disposed on the above-mentioned negative current collector and comprising a first particle; and A second lithium host layer disposed on the first lithium host layer and comprising a second particle Includes, The first particle comprises a first carbon-based material and an active material that forms an alloy with lithium, and its surface is coated with amorphous carbon, and The above second particle comprises a second carbon-based material and an active material that forms an alloy with lithium, a negative electrode for a lithium secondary battery.

2. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein each of the first carbon-based material and the second carbon-based material comprises at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, acetylene black, furnace black, Kettjen black, graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, fullerene, carbon sheet, and carbon foam.

3. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the active material forming an alloy with the lithium comprises at least one selected from the group consisting of silicon (Si), aluminum (Al), tin (Sn), magnesium (Mg), bismuth (Bi), silver (Ag), antimony (Sb), lead (Pb), and cadmium (Cd).

4. In Paragraph 1, The amorphous carbon comprises at least one selected from the group consisting of hard carbon, soft carbon, carbon black, acetylene black, furnace black, Kettjen black, graphene oxide, and pitch carbon, for a negative electrode for a lithium secondary battery.

5. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the surface of the second particle is coated with a non-conductive polymer.

6. In Paragraph 5, The above non-conductive polymer comprises at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyolefin, polyamide, polyester, aramid, acrylic, polycaprolactone, polycarbonate, polyurethane, polystyrene, polyethylene terephthalate, polybenzimidazole, poly(2-hydroxyethyl methacrylate), poly(ether imide), and styrene-butadiene-styrene triblock copolymer (SBS), a negative electrode for a lithium secondary battery.

7. In Paragraph 1, The average particle size (D50) based on the volume of the first particle is 1 μm to 15 μm, and A negative electrode for a lithium secondary battery, wherein the average particle size (D50) based on the volume of the second particle is 5 μm to 20 μm.

8. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the ratio of the thickness of the first lithium host layer to the thickness of the second lithium host layer is 1:0.2 to 1:

5.

9. In Paragraph 1, The weight of the active material forming an alloy with the lithium included in the first particle is 3% to 20% by weight relative to the weight of the first carbon-based material. A negative electrode for a lithium secondary battery, wherein the weight of the active material forming an alloy with the lithium included in the second particle is 3% to 20% by weight relative to the weight of the second carbon-based material.

10. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the weight of the amorphous carbon is 2% to 20% by weight relative to the total weight of the first carbon-based material included in the first particle and the active material forming an alloy with the lithium.

11. In Paragraph 1, A negative electrode for a lithium secondary battery, further comprising a porous polymer layer disposed on the second lithium host layer.

12. In Paragraph 11, The above porous polymer layer comprises at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polycarbonate (PC), polyimide (PI), polyurethane (PU), polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), and polyetherimide (PEI), for a negative electrode for a lithium secondary battery.

13. In Paragraph 11, The above porous polymer layer has a thickness of 1 μm to 5 μm, a negative electrode for a lithium secondary battery.

14. In Paragraph 1, A negative electrode for a lithium secondary battery, further comprising a metal coating layer between the negative current collector and the first lithium host layer.

15. In Paragraph 14, The negative electrode for a lithium secondary battery, wherein the metal coating layer comprises at least one selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), titanium (Ti), nickel (Ni), cobalt (Co), manganese (Mn), magnesium (Mg), palladium (Pd), silicon (Si), aluminum (Al), bismuth (Bi), tin (Sn), copper (Cu), and zinc (Zn).

16. Anode; cathode; and It includes an electrolyte interposed between the anode and the cathode, The above cathode is, Cathode current collector; A first lithium host layer disposed on the above-mentioned negative current collector and comprising a first particle; and A second lithium host layer disposed on the first lithium host layer and comprising a second particle Includes, The first particle comprises a first carbon-based material and an active material that forms an alloy with lithium, and its surface is coated with amorphous carbon, and A lithium secondary battery comprising a second particle, a second carbon-based material, and an active material that forms an alloy with lithium.

17. In Paragraph 16, A lithium secondary battery, wherein each of the first carbon-based material and the second carbon-based material comprises at least one selected from the group consisting of 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, fullerene, carbon sheet, and carbon foam.

18. In Paragraph 16, A lithium secondary battery comprising at least one selected from the group consisting of hard carbon, soft carbon, carbon black, acetylene black, furnace black, Kettjen black, graphene oxide, and pitch carbon.

19. In Paragraph 16, A lithium secondary battery in which the surface of the second particle is coated with a non-conductive polymer.

20. In Paragraph 19, A lithium secondary battery comprising at least one selected from the group consisting of the above-mentioned non-conductive polymer: polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyolefin, polyamide, polyester, aramid, acrylic, polycaprolactone, polycarbonate, polyurethane, polystyrene, polyethylene terephthalate, polybenzimidazole, poly(2-hydroxyethyl methacrylate), poly(ether imide), and styrene-butadiene-styrene triblock copolymer (SBS).

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