Anode for lithium secondary battery, and lithium secondary battery comprising same

Abstract

The present disclosure provides an anode for a lithium secondary battery, and a lithium secondary battery comprising same. The anode for a lithium secondary battery, according to the present disclosure, comprises: an anode current collector; a first layer, which includes a first metal and is coated on the anode current collector; a second layer, which is disposed on the first layer and includes carbon nanotubes; and a third layer, which is disposed on the second layer and includes carbon nanotubes, wherein at least a portion of the carbon nanotubes of the second layer is coated with a second metal, and the first metal can have a higher work function than the anode current collector.

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

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

[0004] Recently, lithium-ion rechargeable batteries are reaching their limits in terms of performance. Electric vehicles equipped with lithium-ion rechargeable batteries can only travel a distance of less than approximately 400 km per charge, and smartphones equipped with lithium-ion rechargeable batteries struggle to be used for even about 24 hours per charge. These limitations can be overcome by increasing the energy density of lithium-ion rechargeable batteries. To increase the energy density of lithium-ion rechargeable batteries, methods such as replacing the low-energy-density graphite anode with a lithium metal anode, or minimizing or eliminating the anode, may be adopted. However, these methods can cause problems in terms of lifespan characteristics, performance, and thermal stability because lithium deposited on the anode current collector continuously depletes the electrolyte, and the lithium is not electrodeposited uniformly or is deposited locally to form dendrites.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] According to some embodiments of the present disclosure for solving the above technical problem, a negative electrode for a lithium secondary battery comprises a negative electrode current collector, a first layer coated on the negative electrode current collector and including a first metal, a second layer disposed on the first layer and including carbon nanotubes, and a third layer disposed on the second layer and including carbon nanotubes, wherein at least a portion of the carbon nanotubes of the second layer are coated with a second metal, and the first metal may have a higher work function than the negative electrode current collector.

[0009] According to some embodiments of the present disclosure for solving the above technical problem, a lithium secondary battery may include a negative electrode, a positive current collector, a positive composite layer disposed on the positive current collector, and an intermediate layer disposed between the negative electrode and the positive electrode. The negative electrode may include a negative current collector, a first layer coated on the negative current collector and comprising a first metal, a second layer disposed on the first layer and comprising carbon nanotubes, and a third layer disposed on the second layer and comprising carbon nanotubes, wherein at least a portion of the carbon nanotubes of the second layer is coated with a second metal, and the first metal may have a higher work function than the negative current collector.

[0010] According to some embodiments of the present disclosure, a first metal may be coated on the surface of a negative current collector to suppress the emission of electrons within the negative current collector. The first metal may be deposited on the surface of a negative current collector to lower the Fermi level of the negative current collector. By this configuration, the transfer of electrons from the negative current collector to the electrolyte can be prevented, thereby suppressing electrochemical reactions that cause electrolyte decomposition. In addition, the reaction rate with lithium can be slowed down so that lithium is uniformly electrodeposited, and the growth of dendrites formed by localized electrodeposition of lithium can be prevented.

[0011] At least a portion of the surface of the first layer may be coated with chromium (Cr). With this configuration, the bonding strength with the chromium (Cr)-coated carbon nanotubes of the second layer is strengthened, and lithium is uniformly electrodeposited from the bottom of the negative electrode during the charging and discharging process of the lithium secondary battery, and the growth of dendrites formed by localized electrodeposition of lithium can be prevented.

[0012] The carbon nanotubes included in the second layer may be coated with a second metal. The second metal may include chromium (Cr). With this configuration, the second metal improves the interfacial stability between the carbon nanotubes and lithium ions, and lithium is uniformly electrodeposited from the bottom within the negative electrode during the charging and discharging process of the lithium secondary battery, and the growth of dendrites formed by the localized electrodeposition of lithium can be prevented.

[0013] According to some embodiments of the present disclosure, the ion conductivity characteristics, resistance growth rate characteristics, initial efficiency characteristics, and lifespan characteristics of a lithium secondary battery can be improved.

[0014] 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.

[0015] 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.

[0016] FIG. 1 is a schematic diagram showing a unit stacked structure of a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0017] FIG. 2 is a drawing showing a unit stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0018] FIG. 3 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0019] FIG. 4 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0020] FIG. 5 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0021] FIG. 6 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0022] 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.

[0023] 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.

[0024] 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."

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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”.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0034] In this specification, "alloy" means a mixture of two or more metals.

[0035] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0036] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0037] 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.

[0038] 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.

[0039] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0040] In this specification, "discharge" and "discharge" refer to the process of removing electrochemical energy from a battery.

[0041] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0042] In this specification, "cathode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0043] In the present disclosure, "lithium host" means a substrate or framework that accommodates lithium in an electrochemically pre-formed space.

[0044] In the present disclosure, "lithium host structure" means a structure composed of one or more lithium hosts.

[0045] Exemplary embodiments will be described in more detail below.

[0046] In one embodiment of the present disclosure, the lithium secondary battery may be a lithium metal battery. A lithium metal battery may refer to a secondary battery in which lithium metal is used as the negative electrode active material.

[0047] During charging and discharging, dendrites can form on the surface of lithium metal due to side reactions with the electrolyte, and as these dendrites grow, they can cause a short circuit between the anode and the cathode. In addition, there are problems such as volume changes and performance degradation due to the electrodeposition and detachment of lithium metal during charging and discharging. Consequently, the lifespan characteristics, performance, and thermal stability of lithium metal batteries containing lithium metal may be degraded.

[0048] To solve this, a lithium host can be placed within the cathode to enable stable electrodeposition of lithium metal. The lithium host can provide a space where lithium can be stably stored and uniformly distributed within the cathode. The lithium host can be designed with a porous structure or a lithium-affinity material to provide a space for lithium storage.

[0049] 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.

[0050] FIG. 1 is a schematic diagram showing a unit stacked structure of a negative electrode for a lithium secondary battery according to one embodiment of the present disclosure. FIG. 2 is a drawing showing a unit stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0051] An electrode assembly housed inside the case of a lithium secondary battery may include a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes to insulate the positive and negative electrodes. The electrode assembly may be a wound-type electrode assembly formed by stacking and winding a positive electrode, a separator, a negative electrode, and a separator in that order. Alternatively, the electrode assembly may be a stacked-type electrode assembly formed by repeatedly stacking a positive electrode, a separator, a negative electrode, and a separator in that order, and the structure of the electrode assembly is not specifically limited.

[0052] A unit cathode included in the electrode assembly may include a cathode current collector and a lithium host layer disposed on both sides of the cathode current collector. The lithium host layer may include at least one of the first layer, the second layer, and the third layer described later. A unit anode included in the electrode assembly may include an anode current collector and an anode composite layer disposed on both sides of the anode current collector. However, it is not limited thereto, and the anode composite layer may be disposed on only one side of the anode current collector or on only a part of one side. Additionally, the lithium host layer may be disposed on only one side of the cathode current collector or on only a part of one side of the cathode current collector.

[0053] In the present disclosure, "unit stacked structure" is defined as a minimum unit stacked structure that simplifies layers repeatedly stacked in an electrode assembly for convenience of explanation. The unit stacked structure of a negative electrode may refer to a negative electrode current collector and a lithium host layer disposed on one side of the negative electrode current collector. The unit stacked structure of a lithium secondary battery may refer to a structure stacked in the order of a negative electrode current collector, a lithium host layer, an intermediate layer, a positive composite layer, and a positive current collector.

[0054] Referring to FIG. 1, in one embodiment, a negative electrode (140) for a lithium secondary battery may include a negative electrode current collector (142), a first layer (144) coated on the negative electrode current collector (142), a second layer (146) disposed on the first layer (144), and a third layer (148) disposed on the second layer (146).

[0055] Cathode: Cathode current collector

[0056] The negative electrode current collector (142) may not contain a negative electrode active material. Any material constituting the negative electrode current collector (142) that does not react with lithium, that is, any material that does not form an alloy or compound with lithium and has conductivity is possible. The metal substrate is, for example, a metal or an alloy. The metal substrate may be, for example, made of 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.

[0057] The negative current collector (142) includes, for example, a first metal substrate. The first metal substrate includes the first metal as a main component or is made of the first metal. The first metal substrate includes the first metal as a main component or is made of the first metal. The content of the first metal included in the first metal substrate is, for example, 90 weight% or more, 95 weight% or more, 99 weight% or more, or 99.9 weight% or more with respect to the total weight of the first metal substrate. The first metal substrate may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium.

[0058] The first metal may be, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited to these; any metal used as a current collector in the relevant technical field may be used. The first metal substrate may be composed of, for example, one of the metals described above, or may be composed of an alloy of two or more metals. The first metal substrate is, for example, in the form of a sheet or foil.

[0059] The negative current collector (142) may further include a coating layer (not shown) containing a second metal on a first metal substrate.

[0060] The negative current collector (142) may include, for example, a first metal substrate and a coating layer disposed on the first metal substrate and containing a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer containing the second metal is harder than the substrate containing the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the first metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The coating layer contains the second metal. The coating layer may, for example, contain the second metal as a main component or be composed of the second metal. The content of the second metal included in the coating layer is, for example, 90% by weight or more, 95% by weight or more, 99% by weight or more, or 99.9% by weight or more with respect to the total weight of the coating layer. The coating layer may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is excessively low, it may be difficult to suppress the deterioration of the negative electrode current collector (142). If the Mohs hardness of the second metal is excessively high, processing may not be easy. The second metal is one or more selected from, for example, titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh).The coating layer may be composed of, for example, one of the metals described above, or an alloy of two or more metals. The difference in Mohs hardness between the first metal included in the first metal substrate and the second metal included in the coating layer may be, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. By having such a difference in Mohs hardness between the first metal and the second metal, the deterioration of the negative current collector (142) can be suppressed more effectively. The coating layer may be a single-layer structure or a multilayer structure of two or more layers. The coating layer may be a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may be a three-layer structure including, for example, a first coating layer, a second coating layer, and a third coating layer. The thickness of the coating layer may be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. The coating layer may be deposited on the first metal substrate by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods; any method capable of forming a coating layer in the relevant technical field is possible.

[0061] For example, the negative current collector (142) may have a reduced thickness compared to a conventional negative current collector. Accordingly, the negative electrode (140) according to the present disclosure is distinguished from a conventional electrode that includes a thick film current collector by including, for example, a thin film current collector.

[0062] 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 (142) 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 (142) 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.

[0063] The negative current collector (142) 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.

[0064] The negative current collector (142) 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 (142) may have a structure comprising a substrate, wherein the substrate may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. An intermediate layer may be additionally disposed on the metal substrate layer.

[0065] 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.

[0066] The metal substrate layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The metal substrate layer may act as an electrochemical fuse and be cut off in the event of an overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal substrate layer. The metal substrate layer may be plated or deposited on a base film. As the thickness of the metal substrate layer decreases, the limit current and / or maximum current of the negative electrode current collector (142) decreases, thereby improving the stability of the lithium metal secondary battery in the event of a short circuit.

[0067] 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° (Celsius), or 100° to 200° (Celsius). 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 (142) with this structure, the weight of the electrode can be reduced and, consequently, the energy density can be improved.

[0068] Cathode: 1st layer

[0069] Referring to FIG. 1, a negative electrode (140) for a lithium secondary battery comprises a first layer (144) coated on a negative electrode current collector (142), and the first layer (144) may comprise a first metal (143). The first metal (143) of the first layer (144) may correspond to a separate component distinct from the first metal of the negative electrode current collector (142) described above.

[0070] In one embodiment, the first metal (143) may have a higher work function than the negative current collector (142). The first metal (143) may be coated on the surface of the negative current collector (142) to suppress the emission of electrons within the negative current collector (142). The first metal (143) may be deposited on the surface of the negative current collector (142) to lower the Fermi level of the negative current collector (142). By this configuration, electrons from the negative current collector (142) are prevented from being transferred to the electrolyte, thereby suppressing electrochemical reactions that cause electrolyte decomposition. Additionally, the reaction rate with lithium is slowed down so that lithium is uniformly electrodeposited, and the growth of dendrites formed by localized electrodeposition of lithium can be prevented.

[0071] In one embodiment, the first metal (143) may have a work function of 5.0 eV to 5.9 eV. Alternatively, the first metal (143) may have a work function of 5.0 eV or more. However, it is not limited thereto, and various metals having a work function higher than that of the negative current collector (142) may be used. For example, the first metal (143) may include iridium (Ir), selenium (Se), nickel (Ni), palladium (Pd), or an alloy thereof.

[0072] In one embodiment, the first metal (143) may be deposited in the form of a thin film on the surface of the negative current collector (142). For example, the thickness of the first layer (144) may be, for example, 50 nm or less. For example, the thickness of the first layer (144) may be 1 nm to 50 nm, 1 nm to 40 nm, 10 nm to 40 nm, 20 nm to 40 nm, or 20 nm to 50 nm. By this configuration, the low electrical conductivity of the first metal (143) can be compensated for. The first layer (144) may be disposed on the negative current collector (142) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming a coating layer in the art is possible.

[0073] In one embodiment, at least a portion of the surface of the first layer (144) may be coated with chromium (Cr). For example, the first layer (144) may include a coating layer (145) that contains chromium (Cr) and is coated on the first metal (143). The coating layer (145) may be deposited in the form of a thin film on at least a portion of the surface of the first metal (143). Specifically, the thickness of the coating layer (145) may be, for example, 50 nm or less. For example, the thickness of the first layer (144), including the coating layer, may be, for example, 1 nm to 100 nm, 1 nm to 80 nm, 1 nm to 70 nm, 5 nm to 90 nm, 10 nm to 100 nm, 20 nm to 100 nm, 30 nm to 90 nm, 40 nm to 80 nm, 50 nm to 100 nm, 60 nm to 100 nm, or 70 nm to 90 nm.

[0074] In one embodiment, the coating layer (145) may be placed on the first metal (143) by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods, and any method capable of forming the coating layer (145) in the relevant technical field is possible. With this configuration, the bonding strength with the chromium (Cr)-coated carbon nanotube of the second layer (146) to be described later is strengthened, lithium is uniformly electrodeposited from the bottom of the negative electrode during the charging and discharging process of the lithium secondary battery, and the growth of dendrites formed by the localized electrodeposition of lithium can be prevented. In one embodiment, the material of the coating layer (145) and the second metal (147) to be described later may be the same.

[0075] The coating layer (145) may include a metal having a lithium affinity similar to chromium (Cr). For example, the coating layer (145) may include a transition metal, a rare earth metal, or a combination thereof. For example, the transition metal may include chromium (Cr), titanium (Ti), zirconium (Zr), molybdenum (Mo), tungsten (W), niobium (Nb), hafnium (Hf), vanadium (V), tantalum (Ta), rhenium (Re), osmium (Os), ruthenium (Ru), cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn), scandium (Sc), or a combination thereof. Rare earth metals may include yttrium (Y), scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), or combinations thereof.

[0076] The coating layer (145) may include a lithium-affinity material. The lithium-affinity material may include, for example, a lithium-affinity metal, a lithium-affinity metal oxide, a lithium-affinity metal phosphate, a lithium-affinity metal nitride, a lithium-affinity metal nitride, a lithium-affinity metal carbide, a lithium-affinity metal-organic framework, a lithium-affinity metal chalcogenide, or a combination thereof.

[0077] Lithium-affinity metals may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or alloys thereof.

[0078] Lithium-affinity metal oxides may include, for example, gold oxide, platinum oxide, palladium oxide, silicon oxide, silver oxide, aluminum oxide, bismuth oxide, tin oxide, manganese oxide, zinc oxide, or combinations thereof. Lithium-affinity metal oxides may include, for example, ZnO, SiO2, MnO2, Co3O4, SnO2, or combinations thereof.

[0079] Lithium-affinity metal nitrides may include, for example, titanium nitride, cobalt nitride, or a combination thereof. Lithium-affinity metal nitrides may include, for example, TiN, Co4N, or a combination thereof.

[0080] Lithium-affinity metal carbides may include, for example, lithium carbide, titanium carbide, or a combination thereof. Lithium-affinity metal carbides may include, for example, Li6C, TiC, or a combination thereof.

[0081] Cathode: 2nd layer and 3rd layer

[0082] In one embodiment, the negative electrode (140) for a lithium secondary battery may include a second layer (146) disposed on a first layer (144) and containing carbon nanotubes (CNT), and a third layer (148) disposed on the second layer (146) and containing carbon nanotubes. The second layer (146) and the third layer (148) may correspond to a lithium host layer.

[0083] The carbon nanotubes included in the second layer (146) may be coated with a second metal (147). The second metal (147) of the second layer (146) may be different from the second metal of the negative current collector (142) described above. The second metal (147) may include chromium (Cr). With this configuration, the second metal (147) improves the interfacial stability between the carbon nanotubes and lithium ions, and during the charging and discharging process of the lithium secondary battery, lithium is uniformly electrodeposited from the bottom within the negative electrode, and the growth of dendrites formed by the localized electrodeposition of lithium can be prevented.

[0084] The second metal (147) may include a metal having a lithium affinity similar to that of chromium (Cr). For example, the second metal (147) may include a transition metal, a rare earth metal, or a combination thereof. For example, the transition metal may include chromium (Cr), titanium (Ti), zirconium (Zr), molybdenum (Mo), tungsten (W), niobium (Nb), hafnium (Hf), vanadium (V), tantalum (Ta), rhenium (Re), osmium (Os), ruthenium (Ru), cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn), scandium (Sc), or a combination thereof. Rare earth metals may include yttrium (Y), scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), or combinations thereof.

[0085] The second metal (147) may include a lithium-affinity material. The lithium-affinity material may include, for example, a lithium-affinity metal, a lithium-affinity metal oxide, a lithium-affinity metal phosphate, a lithium-affinity metal nitride, a lithium-affinity metal nitride, a lithium-affinity metal carbide, a lithium-affinity metal-organic framework, a lithium-affinity metal chalcogenide, or a combination thereof.

[0086] Lithium-affinity metals may include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or alloys thereof.

[0087] Lithium-affinity metal oxides may include, for example, gold oxide, platinum oxide, palladium oxide, silicon oxide, silver oxide, aluminum oxide, bismuth oxide, tin oxide, manganese oxide, zinc oxide, or combinations thereof. Lithium-affinity metal oxides may include, for example, ZnO, SiO2, MnO2, Co3O4, SnO2, or combinations thereof.

[0088] Lithium-affinity metal nitrides may include, for example, titanium nitride, cobalt nitride, or a combination thereof. Lithium-affinity metal nitrides may include, for example, TiN, Co4N, or a combination thereof.

[0089] Lithium-affinity metal carbides may include, for example, lithium carbide, titanium carbide, or a combination thereof. Lithium-affinity metal carbides may include, for example, Li6C, TiC, or a combination thereof.

[0090] In one embodiment, within the initial cathode, the thickness of the second layer (146) may be 10% or less of the total thickness of the first layer (144), the second layer (146), and the third layer (148). For example, the total thickness of the first layer (144), the second layer (146), and the third layer (148) may be 70 μm or less, and the thickness of the second layer may be 7 μm or less. In one embodiment, the thickness of the third layer (148) may be 10% or less of the total thickness of the first layer (144), the second layer (146), and the third layer (148). For example, the total thickness of the first layer (144), the second layer (146), and the third layer (148) may be 70 μm or less, and the thickness of the third layer may be 7 μm or less. In one embodiment, the thickness of the third layer (148) may be equal to or smaller than the thickness of the second layer (146). Accordingly, lithium ions may easily pass through the third layer (148) and reach the surface of the second layer (146) and / or the first layer (144).

[0091] In one embodiment, the sum of the thicknesses of the second layer (146) and the third layer (148) may be 200 nm to 500 nm. For example, the sum of the thicknesses of the carbon nanotubes of the second layer (146) and the third layer (148) may be 200 nm to 300 nm. For example, the thickness of each of the second layer (146) and the third layer (148) may be 100 nm to 150 nm. However, this is not limited thereto, and the sum of the thicknesses of the second layer (146) and the third layer (148) may be 100 nm to 300 nm, or 300 nm to 500 nm. For example, the thicknesses of the first layer (144), the second layer (146), and the third layer (148) may correspond to 50 nm, 125 nm, and 125 nm, respectively, or have a thickness ratio corresponding thereto.

[0092] In one embodiment, the carbon nanotubes of the second layer (146) have a porous structure, and the porosity of the porous structure may be 70% or more. The carbon nanotubes of the third layer (148) have a porous structure, and the porosity of the porous structure may be 70% or more. In one embodiment, the carbon nanotubes of the third layer (148) may have a higher porosity than the carbon nanotubes of the second layer (146). With this configuration, lithium is uniformly electrodeposited from the bottom in the second layer (146) and the third layer (148) during the charging and discharging process of the lithium secondary battery, and the growth of dendrites formed by the localized electrodeposition of lithium can be prevented.

[0093] The second layer (146) and / or the third layer (148) may include a carbon-based material. The second layer (146) and / or the third layer (148) may further include a conductive material and / or a binder. For example, the second layer (146) and / or the third layer (148) may consist only of a carbon-based material. Or, the second layer (146) and / or the third layer (148) may consist of a carbon-based material and a conductive material. Or, the second layer (146) and / or the third layer (148) may consist of a carbon-based material and a binder. Or, the second layer (146) and / or the third layer (148) may consist of a carbon-based material, a conductive material, and a binder.

[0094] The binder included in the second layer (146) and / or the third layer (148) may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer (Poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these and any binder used in the art may be used. The binder may be composed of a single binder or a plurality of different binders.

[0095] The conductive material included in the second layer (146) and / or the third layer (148) is used to impart conductivity to the electrode and may be an electronically conductive material that does not cause chemical changes. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjenblack, carbon fiber, carbon nanofiber, 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.

[0096] In one embodiment, the second layer (146) and / or the third layer (148) may comprise 90% to 99% by weight of a carbon-based material, 0.5% to 5% by weight of a binder, and 0% to 5% by weight of a conductive material. However, this is not limited thereto, and for example, in the second layer (146), the conductive material may be 0.3% to 10% by weight of the total weight of the carbon-based material and the binder. In the third layer (148), the conductive material may be more than 0% by weight and less than or equal to 0.2% by weight of the total weight of the carbon-based material and the binder.

[0097] The second layer (146) and / or the third layer (148) may include one or more lithium hosts. The second layer (146) and / or the third layer (148) may be composed of, for example, a single lithium host. The second layer (146) and / or the third layer (148) may be composed of, for example, a combination of multiple lithium hosts.

[0098] The carbon-based lithium host may include, for example, amorphous carbon, crystalline carbon, porous carbon, non-porous carbon, or a combination thereof. The carbon-based lithium host may include, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, graphene oxide, reduced graphene oxide, carbon fiber, carbon nanotube (CNT), carbon nanobelt, carbon paper, carbon sheet, carbon foam, or a combination thereof. The carbon-based lithium host may include, for example, a carbon fiber cloth, a carbonized MOF, a carbonized porous MOF, a graphene foam, a carbon nanofiber (CNF), a hollow carbon nanocube, a carbon core / shell array, a porous carbon flake, a carbon rod array, 3D nanoporous graphene, a crumple graphene ball, a graphene ball containing metal oxide particles, a carbon granule, a carbon fiber framework, a carbon matrix, or a combination thereof.

[0099] The second layer (146) and / or the third layer (148) comprises a lithium host, and the lithium host may be, for example, an electrochemically inert lithium host.

[0100] The electrochemically inert lithium host is a lithium host that does not react with lithium to form a compound and acts as a conductor for electron transfer and / or a receptacle for receiving electrodeposited lithium. By including the electrochemically inert lithium host in the second layer (146) and / or third layer (148), the degradation of the lithium secondary battery due to volume change and / or physical property change during charging and discharging of the lithium host can be prevented more effectively. The electrochemically inert lithium host may be a carbon-based lithium host, for example, amorphous carbon.

[0101] A carbon-based lithium host capable of lithium insertion and lithium electrodeposition may refer to a lithium host that enables a lithium secondary battery to operate through capacity development via lithium insertion during charging and discharging, and simultaneously enables the lithium secondary battery to operate through capacity development via lithium electrodeposition during charging and discharging. Capacity development may mean that the lithium secondary battery operates by operating as lithium ions are inserted / extracted, or by operating as lithium ions are electrodeposited / deposited in the form of lithium metal to produce electrical energy.

[0102] A carbon-based lithium host capable of lithium electrodeposition may refer to a lithium host capable of both capacity development through lithium insertion and capacity development through lithium electrodeposition during charging and discharging, or a lithium host in which capacity development through lithium electrodeposition accounts for most of the total capacity of the lithium secondary battery.

[0103] The second layer (146) and / or the third layer (148) may include a lithium host structure. A binder may bind a plurality of lithium hosts together to form a lithium host structure. By including a binder in the second layer (146) and / or the third layer (148), the mechanical stability of the lithium host structure may be improved. By including the lithium host structure in the second layer (146) and / or the third layer (148), the electrodeposition of lithium within the second layer (146) and / or the third layer (148) may proceed more easily and uniformly.

[0104] The lithium host structure may include, for example, a one-dimensional structure, a two-dimensional structure, a three-dimensional structure, or a combination thereof.

[0105] The one-dimensional structure may include one-dimensional nanostructures, two-dimensional microstructures, or a combination thereof. The one-dimensional nanostructure may include, for example, nanofibers, nanotubes, nanorods, or a combination thereof. The one-dimensional microstructure may include, for example, microfibers, microtubes, microrods, or a combination thereof. The lithium host one-dimensional structure may include, for example, lithium host one-dimensional nanostructures, lithium host two-dimensional microstructures, or a combination thereof.

[0106] The two-dimensional structure may include, for example, two-dimensional nanostructures, two-dimensional microstructures, or a combination thereof. The two-dimensional nanostructure may include, for example, nanosheets, nanoflakes, or a combination thereof. The two-dimensional microstructure may include, for example, microsheets, microflakes, or a combination thereof. The lithium host two-dimensional structure may include, for example, lithium host two-dimensional nanostructures, lithium host two-dimensional microstructures, or a combination thereof.

[0107] The three-dimensional structure may include, for example, a three-dimensional nanostructure, a three-dimensional microstructure, or a combination thereof. The three-dimensional nanostructure may include, for example, a nanoparticle, a nanocage, a nanomatrix, or a combination thereof. The three-dimensional microstructure may include, for example, a microparticle, a microcage, a micromatrix, or a combination thereof. The lithium host three-dimensional structure may include, for example, a lithium host three-dimensional nanostructure, a lithium host three-dimensional microstructure, or a combination thereof.

[0108] The lithium host structure may include, for example, a porous structure, a non-porous structure, or a combination thereof.

[0109] A porous structure may include one or more pores within the structure. The pores may include open pores, closed pores, or a combination thereof. The porous structure may include, for example, a microporous structure containing pores with a size of 2 nm or less, a mesoporous structure containing pores with a size of 2 nm to 50 nm, a macroporous structure containing pores with a size greater than 50 nm, or a combination thereof. The pores included in the macroporous structure may include, for example, pores with a size greater than 50 nm to 500 nm, pores with a size greater than 500 nm to 1 μm, pores with a size greater than 1 μm to 10 μm, pores with a size greater than 10 μm to 50 μm, or a combination thereof. The lithium host structure may include, for example, 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, but is not limited to these, and any structure used as a lithium host structure in the relevant technical field is possible. 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.

[0110] A non-porous structure is a structure that does not substantially contain pores within the structure. A non-porous structure may include, for example, 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.

[0111] Positive: Positive current collector

[0112] Referring to FIG. 2, an anode composite layer (120) may be disposed on an anode current collector (110) to form an anode (130). In one embodiment, an anode composite layer (120) may be disposed on an intermediate layer (160), and an anode current collector (110) may be disposed on the anode composite layer (120). The intermediate layer (160) may correspond to an electrolyte or a separator.

[0113] The anode (130) includes an anode current collector (110). For example, the anode (130) can be prepared by forming an anode composite layer (120) on the anode current collector (110).

[0114] For example, the positive current collector (110) may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0115] According to one embodiment, the positive current collector (110) may include aluminum (Al). According to one embodiment, the positive current collector (110) may include a base film and a metal layer disposed on one or both sides of the base film, in the same manner as the negative current collector (142) described above.

[0116] Anode: Anode composite layer

[0117] The positive composite layer (120) may include a positive active material. The positive composite layer (120) may further include a conductive material and / or a binder.

[0118] The anode composite layer may include a spinel-based anode active material, an olivine-based anode active material, a layered anode active material, or a combination thereof. As an example, the anode composite layer may include any one of LiMO2 (M = Co, Ni, Mn, Al), LFP, LiM2O4 (M = Ti, V, Mn), or a combination thereof.

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

[0120] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), 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 bO2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

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

[0122] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content 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.

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

[0124] <Chemical Formula 1>

[0125] Li a Ni x Co y M z O2-b A b

[0126] 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.

[0127] 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.

[0128] 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:

[0129] <Chemical Formula 1-1>

[0130] LiNi x Co y Mn z O2

[0131] 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.

[0132] <Chemical Formula 1-2>

[0133] LiNi x Co y Al z O2

[0134] 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.

[0135] 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 Mn 0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0136] 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.

[0137] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0138] 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.).

[0139] For example, the anode (130) may further include an additive that can serve as a sacrificial anode.

[0140] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive composite layer (120), and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive composite layer (120).

[0141] 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.

[0142] 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.

[0143] The positive electrode composite layer (120) may further include a sacrificial positive electrode active material. Specifically, the sacrificial positive electrode active material of the positive electrode composite layer (120) may include Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P, or a combination thereof. A positive electrode (130) for a lithium secondary battery according to some embodiments of the present disclosure includes a sacrificial positive electrode (or sacrificial positive electrode active material) that forms a lithium metal layer on a negative electrode substrate during the formation step, thereby compensating for lithium consumption caused by SEI generation or other side reactions during charging and discharging, and thus can significantly improve the lifespan characteristics of the secondary battery.

[0144] The intermediate layer may include a separator and / or an electrolyte layer.

[0145] Intermediate layer: Separator

[0146] The intermediate layer (160) may include at least one of a separator and an electrolyte layer.

[0147] According to one embodiment, the intermediate layer (160) may be a separator. The separator may be placed between the anode (130) and the cathode (140). The separator may be placed between the anode composite layer (120) and the third layer (148). As the separator according to one embodiment, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc. may be used.

[0148] 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.

[0149] 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.

[0150] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0151] 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.

[0152] 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.

[0153] Intermediate layer: Electrolyte layer

[0154] According to one embodiment, the intermediate layer (160) may be an electrolyte layer. The lithium secondary battery further includes an electrolyte (not shown), and the electrolyte may be injected into the case to impregnate the laminated structure. Alternatively, the electrolyte layer may be disposed between the positive electrode composite layer (120) and the separator. Alternatively, the electrolyte layer may be disposed between the third layer (148) and the separator.

[0155] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0156] The electrolyte is, for example, an organic electrolyte. The organic electrolyte is prepared, for example, by dissolving a lithium salt in an organic solvent. Any organic solvent used as an organic solvent in the relevant technical field may be used.

[0157] 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.

[0158] 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.

[0159] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0160] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0161] 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.

[0162] 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, butyronitrile, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, gamma-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, BN (Butyronitrile), or mixtures thereof.

[0163] Any lithium salt used as a lithium salt in the relevant technical field is also acceptable. Examples of lithium salts include LiDFOB, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1 The lithium salts are SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI, or mixtures thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0164] Solid electrolytes are, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0165] 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 P3-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).

[0166] 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, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x ("LIPON", 0 <x<4, 0<y<3), Li3.25 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-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다.

[0167] 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.

[0168] A polymeric solid electrolyte is an electrolyte that, for example, contains a mixture of a lithium salt and a polymer, or contains a polymer having ion-conducting functional groups. A polymeric solid electrolyte is, for example, a polymeric electrolyte that does not contain a liquid electrolyte. The polymers included in the polymeric solid electrolyte are, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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, polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ketone), SPEEK, sulfonated poly(arylene ether ketone sulfone), SPAEKKS, sulfonated poly(aryl ether ketone, SPAEK), poly[bis(benzimidazobenzisoquinolinones)], SPBIBI), polystyrene sulfonate (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi+ It may be ) or a combination thereof, but is not limited thereto, and any that are used as polymer electrolytes in the relevant technical field are permitted. Any lithium salt that can be used as a lithium salt in the relevant technical field is permitted. Examples of lithium salts include LiDFOB, LiTFSI, 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.

[0169] The electrolyte may correspond to, for example, a gel electrolyte.

[0170] The gel electrolyte is, for example, a gel polymer electrolyte. According to one embodiment of the present disclosure, the gel polymer electrolyte may comprise a first gel polymer electrolyte disposed between a cathode and a separator and / or a second gel polymer electrolyte disposed between an anode and a separator. The gel polymer electrolyte may comprise, for example, an organic solvent, a liquid electrolyte containing a lithium salt, and a cross-linked polymer.

[0171] The organic solvent can be selected from among the organic solvents used in liquid electrolytes. For example, organic solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylene carbonate, ethylmethyl carbonate, fluoroethylene carbonate, methylpropyl carbonate, ethylpropyl carbonate, methylisopropyl carbonate, dipropyl carbonate, dibutyl carbonate, N-methyl-2-pyrrolidinone, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydroxyfranc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolan derivatives, sulfolane, methylsulfolane, It may include at least one selected from the group consisting of 1,3-dimethyl-2-imidazolidinone, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, and combinations thereof.

[0172] The lithium salt may be selected from among lithium salts used in solid polymer electrolytes. The lithium salt may be, for example, a borate-based lithium salt. The borate-based lithium salt may include at least one selected from the group consisting of lithium tetrafluoroborate (LiBF4), lithium difluoro(oxalate)borate (LiDFOB), lithium bis(oxalate)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium bis(2-methyl-2-fluoro-malonato)borate, and combinations thereof.

[0173] 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.

[0174] For example, the cross-linked polymer may have a molecular weight of 5000 g / mol or less. The cross-linked polymer may include, for example, an acrylic monomer having three or more reactive functional groups.

[0175] The crosslinked polymer is a polymerization product of crosslinkable monomers, and the crosslinkable 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), ditrimethylol propanetetraacrylate (DTMPTTA), diglycidyl ester, acrylamide,It may include at least one selected from the group consisting of divinylbenzene and combinations thereof.

[0176] 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 lithium salts, and if it is greater than 2000, 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.

[0177] 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 gel polymer electrolyte.

[0178] In one embodiment, a gel polymer electrolyte can be formed by impregnating a polymer solid electrolyte into an electrolyte within a lithium secondary battery. The gel electrolyte may further include inorganic particles.

[0179] lithium secondary battery

[0180] FIGS. 3 to 6 are perspective views illustrating a lithium secondary battery according to an embodiment of the present disclosure. FIG. 3 is cylindrical, FIG. 4 is prismatic, and FIGS. 5 and 6 are pouch-type batteries. Referring to FIGS. 3 to 6, 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. 3. Additionally, in FIG. 4, 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. 5 and 6, 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.

[0181] Referring to FIG. 3, 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.

[0182] Referring to FIG. 4, 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).

[0183] Referring to FIG. 5, 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.

[0184] Referring to FIG. 6, 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.

[0185] 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. 5 and 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.

[0186] 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).

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] The present invention will be explained in more detail below through the following examples and comparative examples. The following examples are intended only to illustrate the present invention and do not limit the scope of the present invention.

[0192] Example 1

[0193] (Cathode manufacturing)

[0194] A copper (Cu) foil with a thickness of 10 μm was prepared as a cathode current collector. As a first layer, a thin film of iridium (Ir) was coated with a thickness of 30 nm as a first metal on the cathode current collector, and a thin film of chromium (Cr) was coated with a thickness of 20 nm on the first metal to produce a first layer with a thickness of 50 nm.

[0195] A first slurry was prepared by mixing 95 wt% of CNT (carbon-based material), 2 wt% of carbon black (conductive material), and 3 wt% of PVDF (binder) with water solvent.

[0196] The cathode laminate, coated with the first slurry on the prepared cathode current collector, was vacuum dried at 40°C for 10 hours. The dried laminate was 5 ton·f / cm² 2 A second layer with a thickness of 125 nm was prepared by flattening the laminate by cold roll pressing at a pressure of 5 m / s. Subsequently, chromium (Cr) was coated onto carbon nanotubes on the second layer by spraying or electroplating.

[0197] A second slurry was prepared by mixing 95 wt% of CNT (carbon-based material), 2 wt% of carbon black (conductive material), and 3 wt% of PVDF (binder) with water solvent. This was applied onto the second layer in the same manner as the first slurry application method to produce a third layer with a porosity of 70% or more and a thickness of 125 nm.

[0198] (Anode manufacturing)

[0199] An aluminum (Al) foil with a thickness of 10 μm was prepared as an anode current collector. The anode composite layer was prepared by coating the aluminum foil with an anode composite mixed with 98.7 wt% LiCoO2 (anode active material), 0.4 wt% carbon black (conductive material), and 0.9 wt% PVDF (binder). The anode laminate coated with the anode composite on the aluminum foil was vacuum dried at 40°C for 10 hours. The dried laminate was 5 ton·f / cm² 2 The anode composite layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / s and a speed of 5 m / s.

[0200] (Gel Electrolyte Manufacturing)

[0201] The gel polymer electrolyte composition was prepared by the following method. First, as the liquid electrolyte, a mixed solvent of FEC (Fluoroethylene carbonate), DEC (Diethyl carbonate), and BN (Butyronitrile) in a volume ratio of 42:28:10 was used, and DPHA (Dipentaerythritol hexaacrylate) was mixed and used as a crosslinking agent at 4 wt% relative to the total weight of the electrolyte. LiDFOB (Lithium difluoro(oxalato)borate) and LiBF4 (Lithium tetrafluoroborate) were used as electrolyte salts at a concentration of 0.6 M each.

[0202] (Lithium secondary battery manufacturing)

[0203] An electrode assembly was prepared by sequentially stacking a cathode, a separator, and a positive electrode, and the gel electrolyte composition described above was injected into the electrode assembly. Then, a lithium secondary battery was prepared by thermally crosslinking in an oven at 70 degrees (Celsius) for 1 hour and 30 minutes.

[0204] Example 2

[0205] A lithium secondary battery was prepared in the same manner as in Example 1, except that a thin film coating was applied on the negative current collector using selenium (Se) as the first metal as indicated in Table 1.

[0206] Example 3

[0207] A lithium secondary battery was prepared in the same manner as in Example 1, except that nickel (Ni) was used as the first metal and a thin film coating was applied on the negative current collector as indicated in Table 1.

[0208] Example 4

[0209] A lithium secondary battery was prepared in the same manner as in Example 1, except that palladium (Pd) was used as the first metal and a thin film coating was applied on the negative current collector as indicated in Table 1.

[0210] Comparative Example 1

[0211] A lithium secondary battery was prepared in the same manner as in Example 1, except that the first, second, and third layers are absent as indicated in Table 1, and a copper (Cu) foil with a thickness of 10 μm is used alone as the negative electrode.

[0212] Comparative Example 2

[0213] A lithium secondary battery was prepared in the same manner as in Example 1, except that the second and third layers were absent as indicated in Table 1 and a copper (Cu) foil with a thickness of 10 μm coated with iridium was used alone as the negative electrode.

[0214] Comparative Example 3

[0215] As indicated in Table 1, a lithium secondary battery was prepared in the same manner as in Example 1, except that the first layer is absent, the carbon nanotubes of the second layer are not coated with chromium, and the porosity of the second and third layers is 30% or less.

[0216] Comparative Example 4

[0217] As indicated in Table 1, a lithium secondary battery was prepared in the same manner as in Example 1, except that the first layer is absent and the carbon nanotubes of the second layer are not coated with chromium.

[0218] Comparative Example 5

[0219] As indicated in Table 1, a lithium secondary battery was prepared in the same manner as in Example 1, except that the first layer is absent.

[0220] Comparative Example 6

[0221] As indicated in Table 1, a lithium secondary battery was prepared in the same manner as in Example 1, except that chromium was not coated on the carbon nanotubes of the second layer.

[0222] Comparative Example 7

[0223] A lithium secondary battery was prepared in the same manner as in Example 1, except that the second and third layers are absent as indicated in Table 1, and a thin film coating of iron (Fe) as the first metal is used as the negative electrode on a copper (Cu) foil with a thickness of 10 μm.

[0224] Comparative Example 8

[0225] A lithium secondary battery was prepared in the same manner as in Example 1, except that the second and third layers are absent as indicated in Table 1, and magnesium (Mg) is thin-film coated as the first metal on a copper (Cu) foil with a thickness of 10 μm and used as the negative electrode.

[0226] Comparative Example 9

[0227] A lithium secondary battery was prepared in the same manner as in Example 1, except that the second and third layers are absent as indicated in Table 1, and a thin film coating of molybdenum (Mo) as the first metal is used as the negative electrode on a copper (Cu) foil with a thickness of 10 μm.

[0228] Comparative Example 10

[0229] A lithium secondary battery was prepared in the same manner as in Example 1, except that hard carbon (carbon-based material) was used instead of CNT (carbon-based material) as indicated in Table 1, the thickness ratio of the second layer and the third layer was set to 5:5, and the total thickness was adjusted to 45 nm.

[0230] Comparative Example 11

[0231] A lithium secondary battery was prepared in the same manner as in Example 1, except that hard carbon (carbon-based material) was used instead of CNT (carbon-based material) as indicated in Table 1, chromium was not coated on the carbon-based material, and the thickness ratio of the second layer and the third layer was set to 5:5 and the total thickness was adjusted to 45 nm.

[0232] Comparative Example 12

[0233] A lithium secondary battery was prepared in the same manner as in Example 1, except that hard carbon (carbon-based material) was used instead of CNT (carbon-based material) as indicated in Table 1, the first layer was absent, chromium was not coated on the carbon-based material, and the thickness ratio of the second and third layers was set to 5:5 and the total thickness was adjusted to 45 nm.

[0234] Comparative Example 13

[0235] A lithium secondary battery was prepared in the same manner as in Example 1, except that hard carbon (carbon-based material) was used instead of CNT (carbon-based material) as indicated in Table 1, aluminum (Al) was used as the first metal and a thin film was coated on the negative current collector, chromium was not coated on the carbon-based material, and the thickness ratio of the second layer and the third layer was set to 5:5 and the total thickness was adjusted to 45 nm.

[0236] Comparative Example 14

[0237] A lithium secondary battery was prepared in the same manner as in Example 1, except that hard carbon (carbon-based material) was used instead of CNT (carbon-based material) as indicated in Table 1, aluminum (Al) was used as the first metal and a thin film coating was applied on the negative current collector, and the thickness ratio of the second layer and the third layer was set to 5:5 and the total thickness was adjusted to 45 nm.

[0238] Layer 1 Layer 2 Layer 3 Layer 1 Metal Layer 2 Metal Porosity Material Porosity Material Example 1 IrCr 70% or more CNT 70% or more CNT Example 2 SeCr 70% or more CNT 70% or more CNT Example 3 NiCr 70% or more CNT 70% or more CNT Example 4 PdCr 70% or more CNT 70% or more CNT Comparative Example 1 ----Comparative Example 2 Ir---Comparative Example 3--30% or less CNT 30% or less CNT Comparative Example 4--70% or more CNT 70% or more CNT Comparative Example 5-Cr 70% or more CNT 70% or more CNT Comparative Example 6 Ir-70% or more CNT 70% or more CNT Comparative Example 7 Fe-----Comparative Example 8 Mg-----Comparative Example 9 Mo-----Comparative Example 10 IrCr-Hard Carbon-Hard Carbon Comparative Example 11 Ir -- Hard Carbon -- Hard Carbon Comparative Example 12 -- Hard Carbon -- Hard Carbon Comparative Example 13 Al -- Hard Carbon -- Hard Carbon Comparative Example 14 AlCr -- Hard Carbon -- Hard Carbon

[0239] Evaluation Example 1: In the ion conductivity measurement example and comparative example, a coin cell of the SUS / separator / gel polymer electrolyte / SUS structure was prepared by arranging each prepared cathode to face each other.

[0240] A voltage bias of 10 mV was applied to the prepared coin cell in a frequency range of 10 mHz to 200 kHz, and the temperature was scanned while measuring the resistance (R). The ionic conductivity was calculated by substituting the measured coin cell resistance (R) into the following formula. The calculation results are listed in Table 2 below.

[0241] [Equation 1]

[0242] Ionic conductivity (σ) = L (thickness of cathode electrolyte) / R (coin cell resistance) × A (area of ​​cathode electrolyte)

[0243] Evaluation Example 2: Evaluation of Resistance Increase Rate

[0244] For the lithium secondary batteries prepared according to the examples and comparative examples, a formation process was carried out by charging at a current rate of 0.1C. Subsequently, during the charging process, the secondary battery cell was charged at a constant current rate of 0.33C until the voltage reached 4.5V (vs. Li), and then cut-off was performed at a current rate of 0.05C while maintaining a constant voltage of 4.5V in constant voltage mode. Subsequently, during discharge, a constant current discharge at a rate of 1.0C was performed until the voltage reached 2.0V (vs. Li). The above-described charge-discharge process was repeated, and the charge-discharge process was repeated a total of 80 times. In all charge-discharge cycles, a 5-minute pause was provided after each charge / discharge cycle. Here, the resistance increase rate in the Nth cycle is defined by the following formula. The calculation results are listed in Table 2 below.

[0245] [Equation 2]

[0246] Resistance Increase Rate (%) = ((Final Resistance Value - Initial Resistance Value) / Initial Resistance Value) × 100

[0247] Evaluation Example 3: Initial Efficiency Evaluation

[0248] After leaving the coin cells prepared according to the examples and comparative examples at a constant temperature of 25°C for 24 hours, the cell formation process was completed by using a lithium secondary battery charger / discharger (Toyo-System Co., LTD, TOSCAT3500) to charge the cells under constant current conditions of 0.1C to 4.3V and constant voltage conditions with a termination current of 0.05C, and then discharging them under constant current conditions of 0.1C to 2.8V. During the above formation process, the initial efficiency was calculated according to the following formula. The calculation results are listed in Table 2 below.

[0249] [Equation 3]

[0250] Initial efficiency (%) = (Discharge capacity in 1st cycle / Charge capacity in 1st cycle) × 100

[0251] Evaluation Example 4: Lifespan Characteristics Test of Lithium Secondary Battery

[0252] For the lithium secondary battery prepared according to the examples and comparative examples, constant current charging was performed at 45°C at a current rate of 0.1C until the voltage reached 4.30V (vs. Li), and then cut-off was performed at a current rate of 0.05C while maintaining 4.30V in constant voltage mode. Subsequently, discharge was performed at a constant current rate of 0.1C until the voltage reached 3.6V (vs. Li) during discharge (formation stage, 1st cycle).

[0253] The formation process was completed by performing this charge-discharge process once.

[0254] A lithium secondary battery that has undergone the formation stage was charged at 45°C with a constant current of 0.33C within a voltage range of 3.6 to 4.3 V relative to lithium metal, and then cut off at a current rate of 0.05C while maintaining 4.30V in constant voltage mode. Subsequently, constant current discharge was performed at 1.0C until a cut-off voltage of 3.6V was reached. The aforementioned charge / discharge process was repeated. In all charge / discharge cycles, a 5-minute pause was observed after each charge / discharge cycle. Here, the capacity retention rate in the Nth cycle is defined by the following formula.

[0255] [Equation 4]

[0256] Capacity Retention Rate (%) = (Discharge Capacity at Nth Cycle / Discharge Capacity at 1st Cycle) × 100

[0257] The number of charge-discharge cycles (N) at which the capacity retention rate decreases to approximately 80% is shown in Table 2 below.

[0258] Ionic Conductivity (mS / cm) Resistance Increase Rate (%) Initial Efficiency (%) Lifespan (Cycles) Example 1 4.10 1179 8.71 20 Example 23.80 1149 9.11 32 Example 34.01 12199 41 44 Example 43.99 1159 9.01 37 Comparative Example 13.30 280 88.150 Comparative Example 21.50 1879 2.376 Comparative Example 33.40 300 91.068 Comparative Example 43.43 3209 1.659 Comparative Example 53.72 2109 5.194 Comparative Example 63.91 1639 6.21 30 Comparative Example 73.35 280 85.030 Comparative Example 83.27 215 82.043 Comparative Example 93.50 180 95.080 Comparative Example 103.87 159 85.2101 Comparative Example 113.70 147 83.088 Comparative Example 123.40 170 81.028 Comparative Example 133.60 142 81.878 Comparative Example 143.65 152 81.488

[0259] As shown in Table 2, it was confirmed that the lithium secondary batteries of Examples 1 to 4 have high ion conductivity, high initial efficiency, a low resistance growth rate, and generally excellent lifespan characteristics. This is believed to be because the lithium secondary battery includes the negative electrode of the present disclosure, which causes lithium to be uniformly deposited from the bottom of the negative electrode during charging and discharging, and prevents top deposition, thereby exhibiting improved lifespan characteristics and performance. Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. Cathode current collector; A first layer comprising a first metal and coated on the negative current collector; A second layer disposed on the first layer and comprising carbon nanotubes (CNT); and A third layer disposed on the second layer and comprising carbon nanotubes Includes, At least a portion of the carbon nanotubes of the second layer is coated with a second metal, and The above first metal is a negative electrode for a lithium secondary battery having a higher work function than the above negative current collector.

2. In Paragraph 1, The above-mentioned first metal is a negative electrode for a lithium secondary battery having a work function of 5.0 eV or more.

3. In Paragraph 1, The above-mentioned first metal comprises iridium (Ir), selenium (Se), nickel (Ni), palladium (Pd), or an alloy thereof, for a negative electrode for a lithium secondary battery.

4. In Paragraph 1, The above second metal comprises a transition metal, a rare earth metal, or a combination thereof, for a negative electrode for a lithium secondary battery.

5. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein at least a portion of the surface of the first layer is coated with a transition metal, a rare earth metal, or a combination thereof.

6. In Paragraph 1, A negative electrode for a lithium secondary battery, wherein the thickness of the first layer is 100 nm or less.

7. In Paragraph 1, The carbon nanotubes of the second layer above have a porous structure, A negative electrode for a lithium secondary battery having a porous structure with a porosity of 70% or more.

8. In Paragraph 1, The carbon nanotubes of the third layer above have a porous structure, A negative electrode for a lithium secondary battery having a porous structure with a porosity of 70% or more.

9. Cathode; An anode comprising an anode current collector and an anode composite layer disposed on the anode current collector; and An intermediate layer disposed between the above cathode and the above anode Includes, The above cathode is, Cathode current collector; A first layer comprising a first metal and coated on the negative current collector; A second layer disposed on the first layer and comprising carbon nanotubes (CNT); and A third layer disposed on the second layer and comprising carbon nanotubes Includes, At least a portion of the carbon nanotubes of the second layer is coated with a second metal, and A lithium secondary battery in which the first metal has a higher work function than the negative current collector.

10. In Paragraph 9, A lithium secondary battery comprising a positive electrode composite layer comprising a spinel-based positive electrode active material, an olivine-based positive electrode active material, a layered positive electrode active material, or a combination thereof.

11. In Paragraph 9, A lithium secondary battery comprising the anode composite layer comprising any one of LiMO2 (M = Co, Ni, Mn, Al), LFP, LiM2O4 (M = Ti, V, Mn), or a combination thereof.

12. In Paragraph 9, The above-mentioned anode composite layer further comprises a sacrificial anode active material, and The above sacrificial cathode active material comprises any one of Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P, or a combination thereof, in a lithium secondary battery.

13. In Paragraph 9, The above intermediate layer corresponds to at least one of a separator or an electrolyte layer, and A lithium secondary battery in which the above electrolyte layer comprises a gel polymer electrolyte.

14. In Paragraph 9, The above-mentioned first metal is a lithium secondary battery having a work function of 5.0 eV or more.

15. In Paragraph 9, A lithium secondary battery in which the first metal comprises iridium (Ir), selenium (Se), nickel (Ni), palladium (Pd), or an alloy thereof.

16. In Paragraph 9, A lithium secondary battery in which the second metal comprises a transition metal, a rare earth metal, or a combination thereof.

17. In Paragraph 9, A lithium secondary battery, wherein at least a portion of the surface of the first layer is coated with a transition metal, a rare earth metal, or a combination thereof.

18. In Paragraph 9, A lithium secondary battery having a first layer thickness of 100 nm or less.

19. In Paragraph 9, The carbon nanotubes of the second layer above have a porous structure, A lithium secondary battery having a porosity of 70% or more of the above-mentioned porous structure.

20. In Paragraph 9, The carbon nanotubes of the third layer above have a porous structure, A lithium secondary battery having a porosity of 70% or more of the above-mentioned porous structure.

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