Negative electrode for lithium secondary battery, method for manufacturing same, and lithium secondary battery including same

Abstract

Provided are: a negative electrode for a lithium secondary battery; a method for manufacturing same; and a lithium secondary battery including same. The negative electrode comprises: a current collector; and a protective layer disposed on one surface of the current collector, wherein the protective layer includes a polymer support and a lithiophilic material, and has a concentration gradient region in which the concentration of the lithiophilic material progressively increases in a direction from one side of the protective layer on which the current collector is disposed toward the other side of the protective layer on which the current collector is not disposed.

Description

Anode for lithium secondary battery, method for manufacturing same, and lithium secondary battery including same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0106389, filed on August 8, 2024, and all contents of the literature of that Korean patent application are incorporated herein by reference.

[0003] The present specification relates to a negative electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

[0004] With the rapid development of the electronics, communications, and computer industries, the application of energy storage technology is expanding to include camcorders, mobile phones, laptops, and even electric vehicles. Consequently, the development of lightweight, long-lasting, and highly reliable, high-performance, compact secondary batteries is underway.

[0005] Among the secondary batteries currently in use, lithium secondary batteries developed in the early 1990s are attracting attention due to their high operating voltage and superior energy density.

[0006] Lithium metal, carbon-based materials, and silicon are used as negative active materials for lithium secondary batteries. Among them, lithium metal has the advantage of achieving the highest energy density, and therefore continuous research is being conducted.

[0007] However, lithium metal reacts with moisture in the air, producing byproducts such as LiOH, Li2O, and Li2CO3. Furthermore, when lithium metal is exposed to electrolyte, resistive materials are formed, which significantly reduce the performance of the manufactured battery and can even lead to internal short circuits.

[0008] Furthermore, when using lithium metal electrodes, dendrites form on the surface of the lithium metal during the battery's charge and discharge process. This is a problem that must be solved to improve battery performance and stability. Therefore, various methods are being studied to improve the stability of lithium metal electrodes.

[0009] The present specification relates to a negative electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

[0010] The present invention comprises: a collector; and

[0011] Including a protective layer provided on one side of the above-mentioned collector,

[0012] The above protective layer comprises a polymer support and a lithium-affinity material,

[0013] A negative electrode for a lithium secondary battery is provided, which includes a concentration gradient region in which the concentration of the lithium affinity material increases from one side where the current collector of the protective layer is provided to the other side where the current collector of the protective layer is not provided.

[0014] In addition, the present invention comprises a step of preparing a whole body;

[0015] A step of providing a protective layer by irradiating a polymer support composition including a polymer support raw material on one side of the above-mentioned collector; and

[0016] A method for manufacturing the above-described negative electrode for a lithium secondary battery is provided, including a step of providing a lithium-affinity material in the above-described protective layer.

[0017] In addition, the present invention provides a lithium secondary battery including the negative electrode for a lithium secondary battery described above.

[0018] The negative electrode for a lithium secondary battery of the present invention can evenly deposit lithium during battery operation.

[0019] In addition, the negative electrode for a lithium secondary battery of the present invention has the effect of improving battery characteristics.

[0020] In addition, the negative electrode for a lithium secondary battery of the present invention has the effect of improving the battery life.

[0021] Figure 1 is an example of a process diagram for manufacturing a negative electrode for a lithium secondary battery of the present invention.

[0022] Figures 2 to 4 show the TOF-SIMS analysis results according to Experimental Example 1.

[0023] Figures 5 to 9 are the results of scanning electron microscope image analysis according to Experimental Example 2.

[0024] Figure 10 shows the results of analysis of pore characteristics of a carbon support according to Experimental Example 3.

[0025] Figure 11 shows the XRD analysis results according to Experimental Example 4.

[0026] Figures 12 to 15 show the results of observing lithium electrodeposition phenomena according to Experimental Example 5.

[0027] Figures 16 to 18 show the results of battery characteristic evaluation according to Experimental Example 6.

[0028] Hereinafter, the specification will be described in detail.

[0029] Unless otherwise defined herein, all technical and scientific terms used herein are used merely to describe exemplary embodiments and are not intended to be limiting of the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that the terms "comprises," "includes," or "has" specify the presence of implemented features, numbers, steps, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0030] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

[0031] The technical terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Furthermore, the singular forms "a," "an," and "the" as used herein also include the plural forms, unless the context clearly dictates otherwise.

[0032] In the present invention, in time-of-flight secondary ion mass spectrometry (TOF-SIMS), ions (secondary ions) are emitted from the sample surface by irradiating the sample with an ion beam (primary ions), and the mass is analyzed using the difference in the flight time (proportional to the square root of the mass) until the secondary ions reach the detector. Thereby, a mass spectrum of the secondary ions is obtained. In other words, component analysis of the sample surface is possible. In addition, by alternately repeating irradiation of the sample with an ion beam for etching and irradiation thereafter with an ion beam for measurement (primary ion beam), changes in the mass spectrum in the thickness direction can be analyzed. In other words, component analysis in the thickness direction of the sample is possible. A specific method will be described later in an experimental example.

[0033] The present invention comprises: a collector; and

[0034] Including a protective layer provided on one side of the above-mentioned collector,

[0035] The above protective layer comprises a polymer support and a lithium-affinity material,

[0036] A negative electrode for a lithium secondary battery is provided, which includes a concentration gradient region in which the concentration of the lithium affinity material increases from one side of the protective layer having a current collector to the other side of the protective layer not having a current collector.

[0037] In the case of a conventional lithium secondary battery negative electrode including a protective layer having a lithium-affinity material, when the lithium secondary battery negative electrode is applied to a secondary battery and charge / discharge cycles are repeated, lithium ions move to the protective layer containing the lithium-affinity material with a high affinity for lithium and are reduced to lithium metal, resulting in lithium electrodeposition. At this time, the protective layer can act as a mixed ionic-electronic conductor (MIEC), and the electrodeposited lithium moves through grain boundaries by the Coble Creep Mechanism. During this process, it is difficult to control the speed or amount of moving lithium, which causes problems such as the formation of lithium dendrites, cracks occurring at the electrolyte interface, and deterioration of battery performance.

[0038] The negative electrode for a lithium secondary battery of the present invention is characterized by including a concentration gradient region in which the concentration of the lithium affinity material increases from one side where the current collector of the protective layer is provided to the other side where the current collector of the protective layer is not provided. By including the concentration gradient region, the movement speed of lithium is improved, and lithium that has moved to the protective layer is prevented from being precipitated to the outside, thereby preventing the formation of lithium dendrites or the occurrence of cracks at the electrolyte interface, and improving battery performance.

[0039] Specifically, by increasing the concentration of the lithium-affinity material on the other side of the protective layer, which is not equipped with a current collector, coble creep can occur rapidly, and the relative lithium movement speed can be controlled to be high. This allows for faster lithium uptake, thereby improving the lithium movement speed.

[0040] Conversely, by lowering the concentration of the lithium-affinity material on one side of the protective layer, the coble creep can be slowed down and the relative lithium migration rate can be controlled to be low. This prevents lithium diffused into the protective layer from being precipitated outward.

[0041] Meanwhile, by controlling the movement speed of lithium differently in the concentration gradient region of the protective layer as described above, a sandwich structure of a first protective layer provided on the other side of the surface equipped with the current collector and a second protective layer provided on the surface equipped with the current collector can be formed through self-assembly, and lithium can be electrodeposited between the first protective layer and the second protective layer, thereby stably preserving lithium. In other words, the movement path of lithium ions can be efficiently improved, and structural stability can be enhanced.

[0042] In the present invention, the protective layer includes a first protective layer provided on the other side of the surface provided with the current collector, and a second protective layer provided on the side of the surface provided with the current collector, and the concentration of the lithium affinity material of the first protective layer may be greater than the concentration of the lithium affinity material of the second protective layer. During the battery cycle, lithium may be electrodeposited between the first protective layer and the second protective layer, thereby forming a lithium layer. Since the lithium electrodeposition rate on the first protective layer side is high, the amount of lithium electrodeposited from the outside to the protective layer is large, and since the lithium electrodeposition rate on the second protective layer is low, lithium is not deposited to the outside. That is, lithium electrodeposited through the first protective layer is not deposited to the outside through the second protective layer, but can be stably preserved between the first protective layer and the second protective layer.

[0043] In the present invention, the value calculated by the following mathematical formula 1 may be 10% or more and 90% or less.

[0044] [Mathematical Formula 1]

[0045] (T HALF -T MAX ) / (T TOTAL -T MAX )*100(%)

[0046] In the above mathematical formula 1,

[0047] T TOTAL is the total sputter time of the depth profile from the time-of-flight secondary ion mass spectrometry (TOF-SIMS) result in the thickness direction from one side of the protective layer equipped with the current collector to the other side of the protective layer not equipped with the current collector,

[0048] T MAX is the sputter time when the ion detection amount of the lithium affinity material of the above depth profile is maximum,

[0049] T HALF is the above T MAX Sputter time is the time when the amount of ions detected in the sample is half.

[0050] In the present invention, the value calculated by the above mathematical expression 1 indicates a boundary point that is a boundary between an area where the detection amount of the lithium affinity material is high and an area where the detection amount of the lithium affinity material is low. The thickness of the protective layer can be converted from the depth profile, and the boundary point can be expressed numerically. Specifically, the lithium affinity material has the highest detection amount at the outer edge of the protective layer, and the detection amount decreases as the thickness increases toward the current collector. At this time, the point (T) where the detection amount of the lithium affinity material is the highest MAX ), the total reference depth of the area with high detection amount of lithium affinity material and the area with low detection amount of lithium affinity material is (T TOTAL -T MAX ) can be expressed as (T), and the depth of the region with high detection amount of lithium affinity material is (T HALF -T MAX ) can be expressed as. The above mathematical expression 1 quantifies the depth of the region where the detection amount of the lithium affinity material is high, based on the entire reference depth of the protective layer.

[0051] In the present invention, the value calculated by the above mathematical formula 1 may be 10% or more and 90% or less. Preferably, it may be 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, or 58% or more. In addition, it may be 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, or 60% or less. In the above numerical range, the lithium ion deposition rate can be controlled, so that lithium ions can be uniformly deposited within the protective layer and lithium can be prevented from being precipitated to the outside. Through this, the charge / discharge capacity and coulombic efficiency can be improved, and a short circuit can be prevented from occurring during battery operation.

[0052] Meanwhile, the value calculated by the above mathematical expression 1 can be achieved by controlling the type of lithium-affinity material, the thickness of the lithium-affinity material, and the average diameter or porosity of the polymer support.

[0053] In the present invention, the lithium-affinity material may be impregnated into the polymer support. Specifically, the lithium-affinity material may be provided in the pores of the polymer support; the surface of the polymer support; or a combination thereof. When the lithium-affinity material is provided in the pores of the polymer support, it has the effect of preventing the growth of lithium dendrites even during repeated charge and discharge. In the impregnated form, the lithium-affinity material may be dispersed and present in part or all of the polymer support, or the lithium-affinity material may be partially aggregated and present in an island shape.

[0054] In the present invention, the surface area-based impregnation rate of the lithium affinity material may be 5% or more. Preferably, it may be 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, or 95% or more. In addition, it may be 100% or less, 99% or less, 98% or less, 97% or less, 96% or less, 95% or less, 90% or less, 85% or less, or 80% or less. The surface area-based impregnation rate refers to the area ratio of the polymer support provided with the lithium affinity material based on the entire surface area of ​​the polymer support. At this time, the total surface area of ​​the polymer support may mean the total surface area of ​​the outer surface of the polymer support and the total surface area of ​​the pores inside the polymer support, or the total surface area of ​​the pores. Within the above numerical range, the above-described effect of the lithium-affinity material can be sufficiently exerted, and the durability of the protective layer can be maintained.

[0055] In the present invention, the content of the lithium affinity material may be 10 wt% or more and 200 wt% or less based on the total weight of the protective layer. Preferably, it may be 20 wt% or more, 30 wt% or more, 40 wt% or more, 50 wt% or more, 70 wt% or more, 90 wt% or more, or 100 wt% or more. In addition, it may be 180 wt% or less, 160 wt% or less, 150 wt% or less, 140 wt% or less, or 120 wt% or less. Within the above numerical range, the above-described effect of the lithium affinity material can be sufficiently exerted, and the durability of the protective layer can be maintained.

[0056] In the present invention, the porosity of the polymer support may be 1% or more and 30% or less. Preferably, it may be 2% or more, 4% or more, 6% or more, 8% or more, 10% or more, 12% or more, 13% or more, 13.2% or more, or 13.5% or more. In addition, it may be 30% or less, 25% or less, 20% or less, 18% or less, 16% or less, 15% or less, or 14% or less. Within the above numerical range, the lithium-affinity material can easily penetrate into the polymer support, and the lithium-affinity material can be uniformly distributed throughout the polymer support.

[0057] In the present invention, the polymer support may include pores having an average diameter of 50 nm or more and 500 nm or less. Preferably, the average diameter may be 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 100 nm or more, 120 nm or more, 130 nm or more, or 140 nm or more. In addition, it may be 400 nm or less, 300 nm or less, or 200 nm or less. Within the above numerical range, the lithium-affinity material can easily penetrate into the polymer support, and the lithium-affinity material can be uniformly distributed throughout the polymer support.

[0058] In the present invention, the porosity and average diameter of the polymer support can be measured using mercury intrusion porosimetry. Specifically, a polymer support sample is introduced into mercury intrusion porosimetry, and the pressure is gradually increased to infiltrate the pores of the sample. The volume of mercury is recorded, and a relationship such as the Washburn equation is used to create a pore diameter distribution curve based on the pressure and volume of the mercury infiltrated. This can be interpreted by software to calculate the average pore diameter and porosity. The MicroActive AutoPoreV 9600 equipment can be used for the mercury porosimetry.

[0059] In the present invention, the polymer support may have a structure comprising a plurality of fibers. More specifically, the porous polymer support is a three-dimensional network structure in which a plurality of fibers are interconnected, and a plurality of irregular spaces existing between the discrete fibers form pores. The specific form of the porous polymer support is not particularly limited, but may include, for example, a nonwoven fabric, a web form, or a laminated form thereof.

[0060] In the present invention, the average diameter of the fibers included in the porous polymer support may be 50 nm or more and 100 μm or less. Preferably, it may be 50 nm or more, 70 nm or more, or 100 nm or more. In addition, it may be 70 μm or less, 50 μm or less, or 30 μm or less.

[0061] In the present invention, the fibers included in the porous polymer support may be non-ionic conductive polymer fibers. In this case, this is preferable in terms of chemical stability.

[0062] In the present invention, the porous polymer support is polyethylene terephthalate, polyimide, polyamide, polysulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polypropylene, polyetherimide, polyethylene oxide, polyacrylic acid, polydimethylsiloxane, (agarose), polyvinylpyrrolidone, alginate, agarose polyvinylidene hexafluoropropylene, polyurethane, polypyrrole, poly 3,4-ethylenedioxythiophene It may include at least one selected from the group consisting of polyaniline, polyaniline, and derivatives thereof, but is not limited thereto.

[0063] In the present invention, the thickness of the lithium-affinity material may be 10 nm or more and 5,000 nm or less. Preferably, it may be 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more. In addition, it may be 2,000 nm or less, 1,000 nm or less, 700 nm or less, 500 nm or less, 400 nm or less, 350 nm or less, or 320 nm or less. In the above numerical range, lithium can be uniformly diffused in a direction with low stress through the Coble Creep Mechanism, and lithium dendrite growth can be suppressed. In addition, the phenomenon of the pores of the polymer support being blocked by the lithium-affinity material can be prevented. This can improve charge / discharge capacity and coulomb efficiency, and prevent short circuits from occurring during battery operation.

[0064] In the present invention, the lithium-affinity material may include gold (Au), silver (Ag), magnesium (Mg), platinum (Pt), aluminum (Al), gallium (Ga), zinc (Zn), bismuth (Bi), tin (Sn), indium (In), antimony (Sb), lead (Pb), silicon (Si), germanium (Ge) or an alloy thereof; an oxide of copper (Cu), zinc (Zn), cobalt (Co), manganese (Mn); or a combination thereof.

[0065] In the present invention, the lithium-affinity material may be gold (Au), silver (Ag), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), or an alloy thereof. Preferably, it may be magnesium (Mg); or an alloy of magnesium and gold (Au), silver (Ag), platinum (Pt), zinc (Zn), or silicon (Si). Magnesium can easily form an alloy with lithium at the magnesium interface, enabling stable electrodeposition of lithium, and has a low overpotential at the initial stage of the reaction, thereby minimizing the formation of dendrites.

[0066] In the present invention, the thickness of the protective layer may be 1 µm or more and 100 µm or less. Preferably, it may be 2 µm or more, 3 µm or more, 4 µm or more, 5 µm or more, or 6 µm or more. In addition, it may be 90 µm or less, 70 µm or less, 50 µm or less, 30 µm or less, 20 µm or less, or 10 µm or less. Within the above numerical range, stable electrodeposition of lithium is possible, and the overall mechanical stability of the negative electrode for a lithium secondary battery can be improved.

[0067] In the present invention, the current collector may include, without limitation, any current collector that can be used in the relevant technical field. The negative electrode current collector may include a material that does not react with lithium, i.e., does not form any alloy or compound with lithium. For example, the current collector may be selected from the group consisting of copper, stainless steel, titanium, iron, cobalt, palladium, nickel, alloys thereof, and combinations thereof, but is not limited thereto. Here, the stainless steel may be surface-treated with carbon, nickel, titanium, or silver, and the alloy may be an aluminum-cadmium alloy. In addition, calcined carbon, a non-conductive polymer or a conductive polymer surface-treated with a conductive material, etc. may also be used.

[0068] In the present invention, the shape of the collector is not particularly limited, but may be, for example, in the form of a plate or foil. Preferably, it may be in the form of a foil.

[0069] In the present invention, the thickness of the current collector may be 1 μm or more and 100 μm or less. Preferably, it may be 2 μm or more, 4 μm or more, 6 μm or more, or 8 μm or more. Alternatively, it may be 90 μm or less, 80 μm or less, 60 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. Within the above numerical range, excellent conductivity and heat resistance can be maintained.

[0070] In the present invention, the current collector and the protective layer may be in direct contact with each other. Direct contact may mean a state of physical or electrical contact. Alternatively, this may mean that no other member is provided between the current collector and the protective layer.

[0071] In the present invention, the negative electrode for the lithium secondary battery may include a lithium metal layer provided between the current collector and the protective layer. The lithium metal layer may be intentionally formed, or may be lithium deposited or formed while cycling the lithium secondary battery of the present invention.

[0072] In the present invention, the lithium metal layer may include lithium foil, lithium powder, or plated lithium. Here, the active material layer including the lithium powder may be introduced by coating a slurry including lithium powder and a binder, etc., on an anode current collector. The binder is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the art may be used without limitation. Regarding the plated lithium, in the initial state or after complete discharge of the secondary battery including the anode according to the present invention, the anode current collector and the protective layer may be in direct contact. However, when a secondary battery, especially an all-solid-state battery, is charged, lithium ions are released from the positive active material, pass through the solid electrolyte, are reduced to lithium on top of or inside the protective layer, and move toward the negative electrode to be deposited on the negative electrode current collector. As a result, a lithium deposition layer may be formed between the current collector and the negative electrode coating layer. In the present invention, the lithium metal layer also includes the concept of such a lithium deposition layer.

[0073] In the present invention, the lithium metal layer may include lithium or a lithium alloy. Here, the lithium alloy may include at least one selected from the group consisting of lithium and silver (Ag), tin (Sn), indium (In), silicon (Si), gallium (Ga), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), zinc (Zn), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), iron (Fe), cobalt (Co), chromium (Cr), magnesium (Mg), cesium (Ce), lanthanum (La), tungsten (W), and tellurium (Te).

[0074] In the present invention, the thickness of the lithium metal layer may be 0.1 ㎛ or more and 100 ㎛ or less. Preferably, it may be 0.1 ㎛ or more, 1 ㎛ or more, 3 ㎛ or more, 5 ㎛ or more, or 10 ㎛ or more. In addition, it may be 80 ㎛ or less, but is not limited thereto, and may be appropriately adjusted depending on the shape, capacity, etc. of the lithium metal battery to which the negative electrode of the present invention is to be applied. If the thickness of the lithium metal layer is less than the above range, the structural stability of the secondary battery may be lowered, and the possibility of occurrence of side reactions may increase. On the other hand, if the thickness of the lithium metal layer exceeds the above range, the energy density of the secondary battery of the lithium metal layer may be lowered.

[0075] The present invention provides a method for manufacturing the above-described negative electrode for a lithium secondary battery, comprising the steps of: preparing a current collector; forming a protective layer by spraying a polymer support composition including a polymer support raw material onto one surface of the current collector; and providing a lithium affinity material to the protective layer. The manufacturing process is illustrated in Fig. 1. According to Fig. 1, a polymer support composition (a) is sprayed (b) onto a current collector (i) to form a protective layer (c), and a lithium affinity material is provided (d), thereby forming a protective layer (e) impregnated with a lithium affinity material.

[0076] In the present invention, the polymer support composition may include a polymer support raw material and a solvent.

[0077] In the present invention, the polymer support raw material may be the material of the polymer support described above, and the solvent may be an organic solvent such as dimethylformamide (DMF).

[0078] In the present invention, the weight average molecular weight of the polymer support raw material may be 50,000 or more and 500,000 or less. Preferably, it may be 70,000 or more, 80,000 or more, 100,000 or more, 120,000 or more, or 140,000 or more. In addition, it may be 400,000 or less, 300,000 or less, 250,000 or less, 220,000 or less, 200,000 or less, 180,000 or less, or 160,000 or less. Within the above numerical range, chain entanglement necessary for fiber formation occurs, and the viscosity does not become excessively high, thereby improving processability.

[0079] In the present invention, the solid content of the polymer support composition may be 1 wt% or more and 30 wt% or less. Preferably, it may be 2 wt% or more, 4 wt% or more, 6 wt% or more, or 9 wt% or more. In addition, it may be 26 wt% or less, 24 wt% or less, 22 wt% or less, or 20 wt% or less. Within the above numerical range, viscosity can be appropriately maintained, thereby improving processability.

[0080] In the present invention, the step of providing a protective layer by spinning a polymer support composition including a polymer support raw material on one surface of the current collector may use an electrospinning method, a wet spinning method, a melt spinning method, or a solvent spinning method.

[0081] In the present invention, the step of providing a protective layer by spinning a polymer support composition including a polymer support raw material on one surface of the current collector may use an electrospinning method, and may include a step of adjusting the shortest distance between a nozzle and one surface of the current collector to be 1 cm or more and 50 cm or less; a step of applying an applied voltage; and a step of spinning the polymer support composition.

[0082] In the present invention, the shortest distance between the nozzle and one surface of the collector may be 1 cm or more and 50 cm or less. Preferably, it may be 3 cm or more, 5 cm or more, 7 cm or more, 10 cm or more, 13 cm or more, or 15 cm or more. In addition, it may be 40 cm or less, 30 cm or less, or 20 cm or less. Within the above numerical range, there is an effect that enables the formation of a polymer support with a small thickness deviation.

[0083] In the present invention, the applied voltage may be 5 kV or more and 50 kV or less. Preferably, it may be 7 kV or more, 10 kV or more, 12 kV or more, 13 kV or more, or 14 kV or more. In addition, it may be 40 kV or less, 30 kV or less, 20 kV or less, 18 kV or less, or 16 kV or less. Within the above numerical range, there is an effect of enabling the formation of a polymer support with a small deviation in pore characteristics.

[0084] In the present invention, the spinning rate of the step of spinning the polymer support composition may be 1 uL / min or more and 50 uL / min or less. Preferably, it may be 3 uL / min or more, 5 uL / min or more, 7 uL / min or more, 10 uL / min or more, or 13 uL / min or more. In addition, it may be 40 uL / min or less, 30 uL / min or less, or 20 uL / min or less. Within the above numerical range, there is an effect that enables the formation of a polymer support with little variation in thickness or pore characteristics.

[0085] In the present invention, the step of radiating the polymer support composition may be performed at a relative humidity of 5% or more and 30% or less and a temperature of 10°C or more and 40°C or less. The relative humidity may be 10% or more, 12% or more, or 13% or more, and may be 25% or less, 23% or less, 20% or less, or 17% or less.

[0086] In the present invention, the temperature of the step of radiating the polymer support composition may be 15°C or higher, 20°C or higher, or 23% or higher, and may be 35°C or lower, 30°C or lower, or 28°C or lower. Under the above conditions, the polymer support composition has good flowability and thus has an excellent processability effect.

[0087] In the present invention, the step of forming a protective layer by spraying a polymer support composition including a polymer support raw material onto one surface of the current collector may include a step of connecting the polymer supports to each other. At this time, the fibers may be connected using a web forming method known in the art, such as a needle punching method, a chemical bonding method, a thermal bonding method, a melt blown method, a spunlace method, a stitch bonding method, a spun bonding method, or an electrospinning method.

[0088] In the present invention, the step of providing a lithium-affinity material in the protective layer can be performed by plating, immersion, spin coating, dip coating, spray coating, doctor blade, solution casting, drop coating, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition).

[0089] In the present invention, the step of providing a lithium-affinity material in the protective layer may include a step of depositing the lithium-affinity material on the protective layer. Specifically, a physical vapor deposition (PVD), chemical vapor deposition (CVD), or thermal evaporation method may be used. In this case, the lithium-affinity material can be deposited in a thin thickness, and the lithium-affinity material can be easily impregnated even into a polymer support having a small pore size.

[0090] In the present invention, the step of impregnating the protective layer with a lithium-affinity material can be performed by pre-determining the thickness of the lithium-affinity material using a thin film deposition monitor. In this case, deposition or coating can be performed until the target thickness is reached. The thin film deposition monitor can be a thin film deposition monitoring device (manufactured by INFICON, product name: SQM-160).

[0091] In the present invention, the deposition rate of the step of impregnating the lithium affinity material into the protective layer may be 0.1 Å / s or more and 10 Å / s or less. Preferably, it may be 0.2 Å / s or more, 0.3 Å / s or more, 0.4 Å / s or more, 0.5 Å / s or more, 0.6 Å / s or more, 0.7 Å / s or more, 0.8 Å / s or more, 0.9 Å / s or more, or 1 Å / s or more. In addition, it may be 9 Å / s or less, 8 Å / s or less, 7 Å / s or less, 6 Å / s or less, 5 Å / s or less, 4 Å / s or less, 3 Å / s or less, or 2 Å / s or less. In the above numerical range, the density of the deposited lithium affinity material and the adhesion to the protective layer may be improved.

[0092] The present invention provides a lithium secondary battery including the above-described negative electrode for a lithium secondary battery.

[0093] The lithium secondary battery of the present invention comprises a positive electrode; and a solid electrolyte provided between the negative electrode and the positive electrode for the lithium secondary battery. The lithium secondary battery of the above type may be referred to as an all-solid-state lithium secondary battery.

[0094] In the present invention, the protective layer of the cathode can be formed on the surface facing the anode.

[0095] In the present invention, the solid electrolyte may be positioned on the protective layer of the negative electrode. The solid electrolyte serves as both an electrolyte and a separator in an all-solid-state lithium secondary battery, and may include a solid electrolyte and a binder.

[0096] In the present invention, the solid electrolyte may further include one or more of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte.

[0097] In the present invention, the polymer-based solid electrolyte may be a solid polymer electrolyte formed by adding a polymer resin to a lithium salt that is independently solvated, or a polymer gel electrolyte in which an organic electrolyte solution containing an organic solvent and a lithium salt is incorporated into a polymer resin.

[0098] In the present invention, the solid polymer electrolyte is not particularly limited as long as it is a polymer material that is typically used as a solid electrolyte material for an all-solid-state lithium secondary battery as an ion-conductive material. The solid polymer electrolyte may include, for example, a polyether-based polymer, a polycarbonate-based polymer, an acrylate-based polymer, a polysiloxane-based polymer, a phosphazene-based polymer, a polyethylene derivative, an alkylene oxide derivative such as polyethylene oxide, a phosphoric acid ester polymer, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociation group, etc. As an example, the solid polymer electrolyte may include a branched copolymer, a comb-like polymer, a cross-linked polymer resin, etc., in which an amorphous polymer such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene is copolymerized as a comonomer in a polyethylene oxide (PEO) main chain as a polymer resin.

[0099] In the present invention, the polymer gel electrolyte includes an organic electrolyte containing a lithium salt and a polymer resin, and the organic electrolyte contains 60 to 400 parts by weight based on the weight of the polymer resin. The polymer applied to the gel electrolyte is not limited to a specific component, but may include, for example, PVC-based, PMMA-based, polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), etc.

[0100] In the present invention, in the solid electrolyte, the lithium salt mentioned above is an ionizable lithium salt, Li + X - It can be expressed as . There is no particular limitation on the anion of these lithium salts, but F- , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - ,　 CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N -　 Examples include:

[0101] In the present invention, the sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass ceramic. Non-limiting examples of such sulfide-based solid electrolytes include Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, etc., and may include one or more of these.

[0102] In the present invention, the oxide-based solid electrolyte contains oxygen (O) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. Non-limiting examples thereof include LLTO-based compounds, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (where, 0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(where, 0≤x≤1, 0≤y≤1), LiTi x Zr 2-x (PO4)3 (wherein, 0≤x≤1, 0≤y≤1), may include at least one selected from among LISICON compounds, LIPON compounds, perovskite compounds, NASICON compounds, and LLZO compounds.

[0103] In the present invention, as described above, a lithium secondary battery negative electrode having a protective layer impregnated with a lithium-affinity material on a current collector is manufactured, and then a solid electrolyte is applied to at least one surface of the lithium secondary battery negative electrode to form a solid electrolyte. After the solid electrolyte is formed as described above, a positive electrode can be placed on the solid electrolyte.

[0104] In the present invention, the positive electrode may include a current collector and a positive electrode active material positioned on at least one surface of the current collector.

[0105] In the present invention, the positive electrode can be manufactured in the form of a positive electrode by applying a composition including a positive electrode active material, a conductive material, and a binder to a current collector.

[0106] In the present invention, the positive electrode active material may be, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y = 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides expressed as O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and y = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc. can be used, but are not limited to these.

[0107] In the present invention, the conductive agent may typically be 1 wt% or more and 30 wt% or less based on the total weight of the electrode active material. Preferably, it may be 1 wt% or more or 5 wt% or more. In addition, it may be 20 wt% or less or 10 wt% or less. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, it may include one or a mixture of two or more selected from the following conductive materials: graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0108] In the present invention, the binder resin is not particularly limited as long as it is a component that assists in the binding of electrode components such as electrode active materials or solid electrolytes and the binding thereof to a current collector, and examples thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0109] In the present invention, the content of the binder resin may be 1 wt% or more and 30 wt% or less based on the total weight of the electrode active material. Preferably, it may be 1 wt% or more, 2 wt% or more, or 4 wt% or more. Additionally, it may be 20 wt% or less or 10 wt% or less.

[0110] In the present invention, the current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, the current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0111] In the present invention, when a laminate in which a negative electrode, a solid electrolyte, and a positive electrode are arranged in the above order is manufactured, an all-solid-state lithium secondary battery can be manufactured by pressing the laminate. The pressing process can be performed at a temperature range of 25°C to 90°C. In addition, the pressing process can be performed by pressing at a pressure of 550 MPa or less, for example, 500 MPa or less, for example, 1 MPa to 500 MPa or less. The pressing time can vary depending on the temperature and pressure, but can be, for example, less than 30 minutes. The pressing process can be, for example, isostatic pressing, roll pressing, plate pressing, or warm isostatic pressing.

[0112] When the negative electrode provided in the present invention is applied to a secondary battery, particularly an all-solid-state lithium secondary battery, the protective layer included in the negative electrode may exhibit a resistance effect against a pressurized environment generated during the manufacturing process of the all-solid-state lithium secondary battery.

[0113] Meanwhile, the all-solid-state lithium secondary battery manufactured as described above can be housed (cased) in a container.

[0114] Hereinafter, the present invention will be described in more detail through examples.

[0115] <Examples and Comparative Examples>

[0116] <Example 1>

[0117] A stainless steel foil (Steel Use Stainless: SUS) with a thickness of 10㎛ was prepared.

[0118] A 9.1 wt% polymer support composition was prepared by dissolving polyacrylonitrile (manufactured by Sigma Aldrich, molecular weight: 150,000 g / mol) as a polymer support raw material in dimethylformamide (DMF), a solvent, at 25°C for 12 hours.

[0119] The polymer support composition was placed in a plastic syringe pump equipped with an 18-gauge metal needle and positioned 17 cm above the current collector. 0.1 mL of the polymer support composition was electrospun under conditions of 15 kV voltage, 15 μL / min injection rate of the polymer support composition, 15% relative humidity, and 25°C to form a protective layer comprising a 6 μm thick polymer support. The process of forming the protective layer is illustrated in Fig. 1.

[0120] To deposit a lithium-affinity material on the polymer support of the protective layer, raw magnesium (Mg) metal was placed in a deposition device (KVT-3004, manufactured by Korea Vacuum Tech Co., Ltd.), and magnesium was deposited at a deposition rate of 1 Å / s to manufacture a negative electrode for a lithium secondary battery. At this time, the thickness of the magnesium was monitored using a thin film deposition monitor (product name: SQM-160, manufactured by INFICON Co., Ltd.), and the deposition process was stopped when the thickness reached 300 nm, thereby controlling the deposition thickness of the magnesium to 300 nm.

[0121] <Example 2>

[0122] A negative electrode for a lithium secondary battery was manufactured in the same manner as Example 1, except that the thickness of the deposited magnesium was adjusted to 200 nm.

[0123] <Example 3>

[0124] A negative electrode for a lithium secondary battery was manufactured in the same manner as Example 1, except that the thickness of the deposited magnesium was adjusted to 50 nm.

[0125] <Comparative Example 1>

[0126] A negative electrode for a lithium secondary battery was manufactured in the same manner as in Example 1, except that magnesium was not deposited (SUS-PAN).

[0127] Comparative Example 2

[0128] A negative electrode for a lithium secondary battery was manufactured by directly depositing magnesium on the stainless steel foil (Steel Use Stainless: SUS) used in Example 1 without forming a protective layer. At this time, the same method as in Example 1 was used except that the protective layer was not formed (SUS@Mg).

[0129] <Comparative Example 3>

[0130] A stainless steel foil (Steel Use Stainless: SUS) was prepared, identical to that used in Example 1, but without a protective layer or magnesium deposition (SUS).

[0131] <Experimental Example>

[0132] <Experimental Example 1: TOF-SIMS Analysis>

[0133] One side of the negative electrode for lithium secondary batteries manufactured in Examples and Comparative Examples was analyzed. The negative electrode sample for lithium secondary batteries was placed in an analysis chamber, and vacuum was maintained within the chamber.

[0134] A pulsed 30 keV bismuth single ion beam (Bi1) was irradiated onto the protective layer surface of a lithium secondary battery anode to generate ions. The analysis area was a square area of ​​100 μm x 100 μm.

[0135] The emitted ions were accelerated by an electric field and passed through a TOF flight tube, and the arrival time was measured to derive a mass spectrum.

[0136] Afterwards, the sample surface was gradually sputtered using a 2 keV Cs ion beam. A 30 keV bismuth single ion beam in pulse form was irradiated in the depth direction to investigate the component distribution of the sample according to the sputtering time. At this time, the sputtering area was set wider than the analysis area (300 μm * 300 μm).

[0137] The mass spectrum according to the sputtering time was derived and shown in the drawing, and the values ​​calculated using the following mathematical formula 1 were derived and recorded in Table 1 below. Fig. 2 represents the results of Example 1, Fig. 3 represents the results of Example 2, and Fig. 4 represents the results of Example 3, respectively.

[0138] [Mathematical Formula 1]

[0139] (T HALF -T MAX ) / (T TOTAL -T MAX )*100(%)

[0140] In the above mathematical formula 1,

[0141] T TOTAL is the total sputter time of the depth profile from the time-of-flight secondary ion mass spectrometry (TOF-SIMS) result in the thickness direction from one side of the protective layer equipped with the current collector to the other side of the protective layer not equipped with the current collector,

[0142] T MAX is the sputter time when the ion detection amount of the lithium affinity material of the above depth profile is maximum,

[0143] T HALF is the above T MAXSputter time is the time when the amount of ions detected in the sample is half.

[0144] <Experimental Example 2: Scanning Electron Microscope Image Analysis>

[0145] The surface of one side of the negative electrode for lithium secondary batteries manufactured in Examples and Comparative Examples was observed using a field emission scanning electron microscope (FE-SEM, manufactured by JEOL, product name: JSM-7600F). The cross-section was polished using a cooling cross-section polisher (manufactured by JEOL, product name: IB-19520CCP) and then observed using a scanning electron microscope (Field Emission SEM, manufactured by JEOL, product name: SM-IT710HR). The scanning electron microscope image of Example 1 is shown in Fig. 5, and the scanning electron microscope image of Comparative Example 1 is shown in Fig. 6. It can be confirmed that magnesium is deposited on the negative electrode for lithium secondary batteries of Example 1.

[0146] In addition, an all-solid-state battery was manufactured according to the method of Experimental Example 5 described below, and an EDS device (Energy-dispersive spectroscopy, manufactured by Oxford Instrument, product name: Ultim Max 100) was attached to a scanning electron microscope (Field Emission SEM) to observe the distribution of elements.

[0147] In the negative electrode for a lithium secondary battery of Example 1, it was confirmed that magnesium was distributed at the interface (interlayer) with the electrolyte, and that a large amount of magnesium was distributed on the other side where the current collector was not provided in the protective layer (Fig. 7).

[0148] In addition, it was confirmed that magnesium was not deposited or was not uniformly deposited on the protective layer (polymer layer) on one side of the negative electrode for the lithium secondary battery of Example 1 equipped with a current collector (Fig. 8: 10kx magnification, Fig. 9: 30kx magnification).

[0149] From the above results, it was confirmed that the protective layer of the negative electrode for the lithium secondary battery of Example 1 has a concentration gradient region in which the concentration of the lithium-affinity material increases from one direction in which the current collector is provided to the other direction in which the current collector is not provided.

[0150] <Experimental Example 3: Analysis of Pore Characteristics of Carbon Support>

[0151] The characteristics of the polymer support for the negative electrode for lithium secondary batteries manufactured in Example 1 were analyzed. 0.05 g of the polymer support of Example 1 was taken and analyzed using a mercury porosimeter (MicroActive AutoPore V 9600). The log differential intrusion volume curve (mL*g) according to the pore size diameter (㎛) -1 ) is shown in Fig. 10. At this time, the average diameter of the polymer support pores was 150 nm, and the porosity was calculated to be 13.6%.

[0152] <Experimental Example 4: XRD Analysis>

[0153] For the negative electrodes for lithium secondary batteries of Example 1 and Comparative Example 1, X-ray diffraction analysis was performed using an X-ray diffraction device (HR-XRD, manufactured by Rigaku SmartLab).

[0154] In the case of Example 1, peaks corresponding to the (002) plane and (101) plane of magnesium were observed, and in Comparative Example 1, the above peaks were not observed ((a) of FIG. 11 refers to Example 1, and (b) of FIG. 11 refers to Comparative Example 1).

[0155] <Experimental Example 5: Observation of Lithium Electrodeposition>

[0156] <Manufacturing of all-solid-state batteries>

[0157] NCM811 (manufactured by LG Chem, LiNi) as the cathode active material 0.8 Co 0.1 Mn 0.1O2), a sulfide-based solid electrolyte (manufactured by POSCO JK Solid Solution, Li6PS5Cl), carbon nanofibers (manufactured by Sigma-Aldrich, Vapor-grown carbon nanofibers) as a conductive agent, and polytetrafluoroethylene (PTFE, manufactured by Sigma-Aldrich) as a binder were mixed in a ratio of 75:22:2:1 to prepare a dry positive electrode for an all-solid-state battery. After applying a pressure of 400 MPa to the manufactured dry positive electrode for an all-solid-state battery, the same solid electrolyte powder as the above sulfide-based solid electrolyte was applied, and a pressure of 50 MPa was applied to form a positive electrode-solid electrolyte layer. Thereafter, the negative electrode manufactured in the above examples or comparative examples was laminated on top of the solid electrolyte layer, and a pressure of 400 MPa was applied to manufacture an all-solid-state battery.

[0158] For the negative electrodes for lithium secondary batteries of Example 1 and Comparative Example 2, all-solid-state batteries were manufactured using the above-described method, and lithium deposition phenomena were observed during charge-discharge cycles with and without a protective layer. Microstructural changes were analyzed by observing scanning electron microscope (SEM) images (Figs. 12 to 15).

[0159] In the case of Comparative Example 2 after one cycle, it was confirmed that lithium was deposited unevenly (Fig. 12), but in Example 1, it was confirmed that lithium was deposited uniformly on the protective layer (specifically, between the first protective layer and the second protective layer) (Fig. 13).

[0160] During the first cycle, an alloying reaction of magnesium occurs in the first protective layer, forming a solid-solution-based Li-Mg alloy. This results in the formation of a mixed ionic-electronic conductor (MIEC) ion / electron dual-conducting framework and a porous structure. This imparts sufficient porosity and promotes the Coble Creep Mechanism of Li, thereby allowing Li to migrate toward the current collector. However, in the second protective layer on the current collector side, the Coble Creep Mechanism of Li is slow, preventing Li from migrating.

[0161] After 30 cycles, the microstructure showed more pronounced differences. In Comparative Example 2, cracks developed at the electrolyte interface due to internal stress, resulting in uneven Li deposition and delamination (Fig. 14). In contrast, in Example 1, even after 30 charges, Li was uniformly deposited, and adhesion between the protective layer and the electrolyte layer (SE) was maintained (Fig. 15). Furthermore, no cracks were observed in the electrolyte interface layer.

[0162] <Experimental Example 6: Battery Characteristics Evaluation>

[0163] Initial battery characteristic evaluation

[0164] An experiment was conducted to measure the initial charge capacity and discharge capacity of the all-solid-state battery manufactured in the same manner as Experimental Example 5. For each all-solid-state battery, 0.05C (0.185 mA cm -2 ) Charge / 0.05C (0.185 mA·cm -2 ) was used as a discharge condition. As a result of the evaluation, it was confirmed that the battery capacity and coulombic efficiency of the example were improved compared to the comparative example.

[0165] Cycle characteristic evaluation

[0166] 0.05C (0.185 mA·cm) for each solid-state battery -2 ) Charge / 0.05C (0.185 mA·cm-2 ) was performed once under the discharge condition. The charge / discharge condition was 0.1C (0.37 mA·cm -2 ) Charge / 0.1C (0.37 mA·cm -2 ) was changed to discharge and performed twice, and the cycle was repeated under the same conditions as the second cycle to calculate the number of cycles in which a short circuit occurred and the coulombic efficiency (CE: discharge capacity compared to charge capacity) after one cycle, which were recorded in Table 1.

[0167] In addition, the internal resistance (Ohm) according to the number of cycles was measured and shown in Fig. 16, the overpotential according to the number of cycles was measured and shown in Fig. 17, and the change in cell thickness according to the charge / discharge time was measured and shown in Fig. 18. (a) of Figs. 16 to 18 represents the results of Example 1, and (b) represents the results of Comparative Example 2.

[0168] In the case of Comparative Example 2, it was confirmed that the internal resistance easily increased depending on the cycle time / number of cycles (Fig. 16), the interior expanded and a change in thickness (△t in Fig. 18) occurred (Fig. 18), and the overpotential increased rapidly, resulting in a short circuit occurring before 100 cycles (arrow point in Fig. 17).

[0169] In the case of Comparative Example 3, only stainless steel foil was used without a protective layer, so the charging and discharging itself was not normal due to a short-circuit phenomenon.

[0170] On the other hand, in the case of the examples, no short circuit occurred at the beginning of the cycle. In particular, in the case of Example 1, no short circuit occurred even during 100 cycles.

[0171] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Experimental Example 1T MAX (Unit:s)300140190NoneNoneNoneT HALF (Unit:s)1,0117901,072NoneNoneNoneT TOTAL(Unit: s) 1,500 1,800 2,000 None None None Mathematical formula 1 (%) 59.34 8.73 9.2 None None None Experimental example 5 Initial charge capacity (mAh / g) 221.6 224.7 224.7 221 211.7 209.7 Initial discharge capacity (mAh / g) 174.2 176.2 175.7 170.8 163.3 162.1 Short circuit occurrence time None 83 times 72 times 47 times 26 times 3 times Coulomb efficiency (%) 78.6 78.4 78.2 77.3 77.177.3

[0172] From the above results, it was confirmed that the negative electrode for a lithium secondary battery having a protective layer equipped with a lithium-affinity material on a polymer support improved long-term stability by not easily causing a short circuit when applied to a secondary battery (Examples 1 to 3). On the other hand, it was confirmed that it was difficult to function as an negative electrode when applied to an electrode using only a current collector (SUS) (Comparative Example 3), and it was confirmed that the negative electrode for a lithium secondary battery not equipped with a lithium-affinity material had deteriorated battery performance (Comparative Example 1).

[0173] Furthermore, even when using a lithium-compatible material, the absence of a protective layer readily increases resistance and overpotential over the cycle, and the cell thickness rapidly increases when the lithium-compatible material is directly mounted on the current collector. This easily causes short-circuiting even at low cycle counts, making it difficult to apply to secondary batteries (Comparative Example 2).

Claims

1. The entire house; and Including a protective layer provided on one side of the above-mentioned collector, The above protective layer comprises a polymer support and a lithium-affinity material, A negative electrode for a lithium secondary battery comprising a concentration gradient region in which the concentration of the lithium affinity material increases from one side where the current collector of the protective layer is provided to the other side where the current collector of the protective layer is not provided.

2. In claim 1, The protective layer includes a first protective layer provided on the other side of the surface on which the entire collector is provided and a second protective layer provided on the side on which the entire collector is provided. A negative electrode for a lithium secondary battery, wherein the concentration of the lithium affinity material of the first protective layer is greater than the concentration of the lithium affinity material of the second protective layer.

3. In claim 1, A negative electrode for a lithium secondary battery, wherein the value calculated by the following mathematical formula 1 is 10% or more and 90% or less: [Mathematical Formula 1] (T HALF -T MAX ) / (T TOTAL -T MAX )*100(%) In the above mathematical formula 1, T TOTAL is the total sputter time of the depth profile from the time-of-flight secondary ion mass spectrometry (TOF-SIMS) result in the thickness direction from one side of the protective layer equipped with the current collector to the other side of the protective layer not equipped with the current collector, T MAX is the sputter time when the ion detection amount of the lithium affinity material of the above depth profile is maximum, T HALF is the above T MAX Sputter time is the time when the amount of ions detected in the sample is half.

4. In claim 1, A negative electrode for a lithium secondary battery, wherein the lithium-affinity material is impregnated into the polymer support.

5. In claim 1, A negative electrode for a lithium secondary battery, wherein the porosity of the polymer support is 1% or more and 30% or less.

6. In claim 1, A negative electrode for a lithium secondary battery, wherein the polymer support includes pores having an average diameter of 50 nm or more and 500 nm or less.

7. In claim 1, A negative electrode for a lithium secondary battery, wherein the thickness of the lithium-affinity material is 10 nm or more and 5,000 nm or less.

8. In claim 1, A negative electrode for a lithium secondary battery, wherein the lithium-compatible material comprises at least one selected from the group consisting of metals including Au, Ag, Pt, Zn, Si, and Mg; and metal oxides including CuO, ZnO, CoO, and MnO.

9. In claim 1, A negative electrode for a lithium secondary battery, wherein the thickness of the protective layer is 1㎛ or more and 100㎛ or less.

10. In claim 1, A negative electrode for a lithium secondary battery, wherein the content of the lithium-affinity material is 10 wt% or more and 200 wt% or less based on the total weight of the protective layer.

11. In claim 1, A negative electrode for a lithium secondary battery, wherein the above-mentioned collector and the above-mentioned protective layer are in direct contact with each other.

12. In claim 1, A negative electrode for a lithium secondary battery comprising a lithium metal layer provided between the above-described collector and the above-described protective layer.

13. Steps to prepare the entire house; A step of providing a protective layer by irradiating a polymer support composition including a polymer support raw material on one side of the above-mentioned collector; and A method for manufacturing a negative electrode for a lithium secondary battery according to any one of claims 1 to 12, comprising a step of providing a lithium-affinity material in the protective layer.

14. A lithium secondary battery comprising a negative electrode for a lithium secondary battery according to any one of claims 1 to 12.

15. In claim 14, Bipolar; and A lithium secondary battery comprising a solid electrolyte provided between the negative electrode and the positive electrode for the lithium secondary battery.

Images