Lithium secondary battery anode comprising protective layer, manufacturing method therefor, and lithium secondary battery comprising same

Abstract

In the present invention, a protective layer including a lithium metal compound is coated on an anode current collector so that the formation of lithium dendrites can be suppressed without deviating from the constituent elements and structure of a conventional battery, and thus the lifespan and cycle characteristics of a battery can be greatly improved.

Description

A negative electrode for a lithium secondary battery including a protective layer, a method for manufacturing the same, and a lithium secondary battery including the same

[0001] The present invention relates to a negative electrode for a lithium secondary battery including a protective layer, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002]

[0003] Since their initial commercialization, lithium-ion batteries have undergone decades of research and development, successfully powering not only electronic devices but also electric vehicles. However, lithium-ion batteries using existing graphite anodes suffer from a major drawback in terms of energy density. Therefore, research and development of new anode materials is essential to meet the ever-increasing energy demand.

[0004] Lithium metal has a very high theoretical capacity of 3860 mAh / g and a very low redox potential of -3.04 V (vs SHE), making it the ultimate anode material for lithium-ion batteries. However, despite extensive research on lithium metal anodes, it is not yet a commercially viable technology. Typical problems when using lithium metal as an anode include: 1. lithium dendrite formation; 2. electrolyte depletion due to the continuous reaction of lithium metal; and 3. low coulombic efficiency due to the destruction of the non-uniform SEI (Solid Electrolyte Interface). The problems described above are not just one problem that occurs when a battery is operated, but rather a combination of all three. Therefore, developing a solution that addresses all of these issues, rather than just one, can lead to the commercialization of lithium metal batteries.

[0005]

[0006] The present invention has been devised to solve the above-mentioned problem, and the method for solving this problem is as follows.

[0007] 1) Adjust electrolyte components

[0008] SEI is one of the substances produced by the reaction between an organic electrolyte and lithium metal. In the 1950s, several non-aqueous solvents were discovered that could form a protective film on the surface of lithium metal, ensuring the stability of lithium metal anodes. Since then, extensive research has been conducted on this topic, significantly contributing to the commercialization of primary batteries using lithium metal as an anode. However, the confirmed stable protective film failed to be applied to secondary batteries due to volume changes that occur during repeated charge and discharge of lithium. Consequently, methods for forming SEI by controlling the composition of the electrolyte reached their limits.

[0009] 2) Additives

[0010] The application of various additives to form a SEI has been studied. Two types of additives have been studied: one that adsorbs onto the lithium metal without decomposition, forming a protective film; and the other that decomposes on the lithium metal surface to form an effective SEI. However, no results have been found that are suitable for practical use in lithium metal batteries.

[0011] 3) Formation of artificial SEI

[0012] Because the SEI is a film that naturally forms when an organic electrolyte and lithium metal come into contact, it is difficult to expect a stable and uniform SEI to form. Therefore, extensive research has been conducted on the formation of various artificial SEIs using solid electrolytes such as LiF, Li3N, Li2O, Al2O3, Li3PO4, LiPON, and other carbon-based materials. An ideal SEI requires high ionic conductivity, excellent electronic insulation, appropriate thickness, high mechanical strength, and chemical stability.

[0013] Lithium transition metal oxides possess properties that make them suitable for use as solid electrolytes in lithium-ion batteries. Depositing these materials using vacuum equipment allows for a desired coating thickness, and subsequent heat treatment allows for the formation of the desired phase. Therefore, suppressing lithium dendrite formation through artificial SEI formation could be a solution for the commercialization of lithium metal batteries.

[0014] Accordingly, one embodiment of the present invention coats a protective layer including a lithium metal compound on a negative electrode current collector to suppress lithium dendrite formation.

[0015] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0016]

[0017] As a technical means for achieving the above-mentioned technical task, one aspect of the present invention provides an anode for a lithium secondary battery, comprising: an anode current collector; a protective layer positioned on at least one surface of the anode current collector and including a lithium metal compound; and a lithium metal layer positioned on at least one surface of the protective layer; wherein the lithium metal compound includes lithium (Li), oxygen (O), and at least one transition metal.

[0018] The thickness of the above negative electrode collector may be 1 nm to 100 nm.

[0019] The above transition metal may include at least one selected from the group consisting of boron (B), tungsten (W), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).

[0020] The above lithium metal compound can be expressed by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li x B y W z O k

[0023] (At this time, 1≤x≤5; 0.1≤y≤2; 0.1≤z≤3; and 5≤k≤15.)

[0024] The above lithium metal compound can be expressed by the following chemical formula 2.

[0025] [Chemical Formula 2]

[0026] Li x B y W z O k

[0027] (At this time, 2≤x≤4; 0.5≤y≤1.5; 1≤z≤2; and 7≤k≤12.)

[0028] The thickness of the above protective layer may be 200 nm to 5 μm.

[0029] As a technical means for achieving the aforementioned technical task, another aspect of the present invention provides a method for producing an anode for a lithium secondary battery, comprising: a step of producing a lithium metal compound by mixing a lithium precursor and one or more transition metal precursors; and a step of coating a protective layer including the lithium metal compound on an anode current collector.

[0030] The above lithium precursor may include at least one selected from the group consisting of Li2O, Li2CO3, LIOH, Li2NO3, and combinations thereof.

[0031] The above transition metal precursor may include at least one selected from the group consisting of B2O3, Li2WO4, TiO2, Fe2O3, ZnO, Co3O4, NiO, CuO, MnO2, and combinations thereof.

[0032] The lithium precursor is Li2O, the transition metal precursor is B2O3 and Li2WO4, and the molar ratio of Li2O, B2O3 and Li2WO4 may be 1 to 5: 1: 0.5 to 2.

[0033] The above coating step can be performed by one or more methods selected from the group consisting of PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), ALD (Atomic Laser Deposition), and combinations thereof.

[0034] The above coating step can be performed by RF sputtering.

[0035] As a technical means for achieving the above-mentioned technical task, another aspect of the present invention provides a lithium secondary battery including the above-mentioned negative electrode; positive electrode; and a separator positioned between the negative electrode and the positive electrode.

[0036]

[0037] According to one embodiment of the present invention, the negative electrode for a lithium secondary battery has an advantage in that it has better performance than a conventional lithium secondary battery by suppressing the formation of lithium dendrites formed by SEI that are formed unevenly as the cycle continues by coating a lithium metal compound on the negative electrode current collector in contact with lithium metal.

[0038] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0039]

[0040] Figure 1 is a schematic diagram of a lithium secondary battery according to one embodiment of the present invention.

[0041] Figure 2 is a flowchart of a method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present invention.

[0042] Figure 3 is X-ray diffraction analysis data of a lithium metal compound powder and a protective layer according to one embodiment of the present invention.

[0043] Figure 4 is a surface and cross-sectional scanning electron microscope (SEM) analysis image of a lithium metal compound formed according to one embodiment of the present invention.

[0044] Figure 5 is electrochemical impedance spectroscopy (EIS) analysis data of a lithium metal compound according to one embodiment of the present invention.

[0045] FIG. 6 is charge / discharge cycle analysis data of a sample to which a lithium metal compound is applied (Example, Li / LBWO-Cu) and a sample to which a lithium metal compound is not applied (Comparative Example, Li / Cu) according to one embodiment of the present invention.

[0046]

[0047] Hereinafter, the present invention will be described in more detail. However, the present invention may be implemented in various different forms, and the present invention is not limited to the embodiments described herein, but is defined solely by the claims set forth below.

[0048] Additionally, the terminology used herein is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. Throughout the specification of the present invention, the term "including" or "comprising" a component does not exclude other components, but rather implies the inclusion of other components, unless specifically stated otherwise.

[0049]

[0050] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0051]

[0052] Example

[0053] <Cathode Manufacturing Method - Lithium Metal Compound (LBWO) Composition and Protective Layer Formation Method>

[0054] Li2O, B2O3, and Li2WO4 were used as raw materials, and the molar ratio of Li2O:B2O3:Li2WO4 was 3.6:1:1.2. After mixing in a ball mill for 24 hours, lithium metal compound powder was synthesized by heat treatment at 700℃ for 3 hours. This was made into pellets through cold pressing to make a sputtering target, and then a protective layer was deposited on a copper negative electrode collector using the RF sputtering method. After that, the lithium metal layer was fabricated as a coin cell in the form of current collector-separator-Li metal in a glove box, and then the electrodeposition method was used to irradiate the copper with 0.1 mA / cm 2 A thickness of 20 μm was deposited on the Cu current collector in the range of . The deposited negative current collector (Li-Cu) was obtained by disassembling the coin cell.

[0055] <Method for manufacturing lithium secondary batteries>

[0056] Coin cells were assembled in an inert atmosphere using an argon-filled glovebox at a humidity of less than 0.1 ppm. The electrolyte used was 1 M LiPF6, and the cathode was LCO and the anode was Li-metal. The battery performance was 0.5 mA / cm 2 It was charged and discharged for 100 cycles at room temperature and evaluated in coin cells using the WBCS 2000 system.

[0057]

[0058] Experimental Example 1: X-ray diffraction (XRD) analysis of lithium metal compound powder and protective layer

[0059] Figure 3 is X-ray diffraction analysis data of a lithium metal compound powder and a protective layer according to an embodiment of the present invention. Through X-ray diffraction analysis, it can be confirmed that the synthesized LBWO (lithium metal compound) has crystallinity, indicating that the synthesis was successful, and it can be confirmed that the protective layer after deposition exhibits an amorphous structure. This is a result of the protective layer deposited by the sputtering process being deposited in an amorphous form, and since an amorphous protective layer has improved ionic conductivity compared to a protective layer having a crystalline form, it can be said that an amorphous form shows better results.

[0060]

[0061] Experimental Example 2: Surface and cross-sectional scanning electron microscope (SEM) analysis of lithium metal compound formation.

[0062] Figure 4 is a surface and cross-sectional scanning electron microscope (SEM) analysis image of a lithium metal compound formed according to one embodiment of the present invention. The formed protective layer (LBWO thin film) was deposited using a RF sputtering method, and the RF sputtering method was performed in an argon (Ar) environment at a base pressure of 510-6 torr and an operating pressure of 510-3, and was performed at a power of 60 W for 6 hours. Silicon was used as the substrate, and it can be confirmed that the deposition was performed well without delamination from the substrate.

[0063]

[0064] Experimental Example 3: Electrochemical Impedance Spectroscopy (EIS) Analysis of Lithium Metal Compounds

[0065] Figure 5 shows electrochemical impedance spectroscopy (EIS) analysis data of a lithium metal compound according to one embodiment of the present invention. For electrochemical impedance spectroscopy analysis of the deposited protective layer (LBWO thin film), stainless steel was used as the negative electrode current collector, and measurements were made using a sandwich structure of SUS / LBWO / SUS.

[0066] ※ EIS measurement method

[0067] - Fabrication of a cell for measuring ionic conductivity using an Electrode (SUS) / Solid electrolyte / Electrode (SUS) structure. Impedance was measured using EIS (Electrochemical Impedance Spectroscopy), and ionic conductivity was calculated based on thickness and area.

[0068] - Manufactured an impedance measurement cell of SUS / LBWO / SUS structure.

[0069] - Ionic conductivity measurement formula:

[0070] - σ: conductivity, d: thickness, R: resistance, A: area

[0071] The fabricated LBWO (lithium metal compound) is 5.2 * 10 -6 It was confirmed to be excellent with an ionic conductivity of S / cm.

[0072]

[0073] Experimental Example 4: Charge / Discharge Cycle Analysis of Samples with and without Lithium Transition Metal Oxide

[0074] Figure 6 shows charge / discharge cycle analysis data of a sample to which a lithium metal compound is applied (Example, Li / LBWO-Cu) according to one embodiment of the present invention and a sample to which a lithium metal compound is not applied (Comparative Example, Li / Cu). The sample to which a lithium metal compound is not applied (Comparative Example, Li / Cu) was manufactured in the same manner as the Example except that it did not include a protective layer.

[0075] For the Li / Cu sample, the Coulombic efficiency drops after 10 cycles, and no further cycling is possible. This is a common finding in lithium metal batteries and is the result of electrode short-circuiting due to lithium dendrite formation. In contrast, the Li / LBWO-Cu sample continues to cycle without any decrease in Coulombic efficiency.

[0076] That is, it can be seen that the electrode short-circuit phenomenon due to lithium dendrite formation does not occur, and it can be confirmed that the LBWO thin film can help the performance and lifespan of a lithium metal battery by suppressing lithium dendrite formation.

[0077]

[0078] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0079] The scope of the present invention is indicated by the claims set forth below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0080]

[0081] The first aspect of this article is,

[0082] A negative electrode (10) for a lithium secondary battery is provided, comprising: a negative electrode current collector (11); a protective layer (12) positioned on at least one surface of the negative electrode current collector (11) and containing a lithium metal compound; and a lithium metal layer (13) positioned on at least one surface of the protective layer (12) facing the negative electrode current collector (11); wherein the lithium metal compound contains lithium (Li), oxygen (O), and at least one transition metal.

[0083]

[0084] Hereinafter, with reference to FIG. 1, a negative electrode for a lithium secondary battery according to the first aspect of the present invention will be described in detail.

[0085] In one embodiment of the present invention, the negative electrode (1) may include a negative electrode current collector (11), a protective layer (12), and a lithium metal layer (13).

[0086] In one embodiment of the present invention, the negative electrode current collector (11) is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and may be selected from the group consisting of copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, alloys thereof, and combinations thereof. 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 surface-treated with a conductive material, or a conductive polymer, etc. may be used. Generally, a copper foil is applied as the negative electrode current collector (11).

[0087] In addition, the form can be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. with / without fine unevenness formed on the surface.

[0088] In one embodiment of the present invention, the thickness of the negative electrode current collector (11) may be 1 to 100 um, preferably 5 to 30 um, and more specifically 1 to 20 um. If the thickness of the negative electrode current collector (11) is less than 1 um, the current collection effect is reduced, and on the other hand, if the thickness exceeds 20 um, there is a problem of reduced processability when assembling the cell by folding.

[0089] In one embodiment of the present invention, a protective layer (12) positioned on at least one surface of the negative electrode current collector (11) may be included.

[0090] Currently, lithium metal has a very high theoretical capacity of 3,860 mAh / g, compared to 372 mAh / g for graphite, and thus, is being extensively studied as an anode material for next-generation lithium secondary batteries. While it offers the advantage of high theoretical capacity, secondary batteries using lithium metal as an anode suffer from the formation of lithium dendrites due to the formation of an uneven SEI over charge and discharge cycles. The formation of lithium dendrites in lithium secondary batteries is the biggest problem, reducing battery life and performance.

[0091] The purpose of the present invention is to suppress lithium dendrite formation and improve battery life performance by coating a protective layer (12) on a negative electrode current collector (11).

[0092] A method for suppressing lithium dendrites using a lithium metal compound and its effect can improve the cycle characteristics of a battery using lithium metal as an anode without departing from the components and structure of existing batteries by modifying the surface of an anode current collector in contact with a lithium metal layer among the components of a conventional lithium metal battery. Specifically, lithium dendrites, known as the biggest drawback of lithium batteries, are known to be formed by an uneven SEI formed during initial charge and discharge, and are known to have a significant impact on the cycle characteristics of the battery.

[0093] In the present invention, by coating a lithium metal compound on the surface of the negative electrode current collector (11) in contact with the lithium metal layer (13), a uniform SEI is formed before the initial cycle begins, so that lithium dendrites can be effectively suppressed even during repeated cycles, which can significantly improve the lifespan and characteristics of a battery using lithium metal as the negative electrode.

[0094] In one embodiment of the present invention, the protective layer (12) includes a lithium metal compound, and the lithium metal compound may include lithium (Li), oxygen (O), and one or more transition metals.

[0095] The above transition metal may include at least one selected from the group consisting of boron (B), tungsten (W), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), rhenium (Re), osmium (Os), and iridium (Ir).

[0096] The above transition metal may be boron (B), and the above lithium metal compound may be Li3BO3, Li2B4O7.

[0097] The above transition metal may be tungsten (W), and the above lithium metal compound may be Li2WO4, Li7La3Zr2O 12 (LLZO) and W-doped Li7La3Zr2-xW x O 12 It could be.

[0098] The above transition metal may be scandium (Sc), and the above lithium metal compound may be LiScO2, Sc-doped LLZO: Li7La3Zr2-xSc x O 12 It could be.

[0099] The above transition metal may be titanium (Ti), and the above lithium metal compound may be Li4Ti5O 12 , LiTi2(PO4)3(NASICON structure).

[0100] The above transition metal may be vanadium (V), and the above lithium metal compound may be Li3VO4, LiV3O8.

[0101] The above transition metal may be chromium (Cr), and the above lithium metal compound may be LiCrO2, Li3Cr2(PO4)3 (NASICON structure).

[0102] The above transition metal may be copper (Cu), and the above lithium metal compound may be LiCuO2, Li2CuO2.

[0103] The above transition metal may be zinc (Zn), and the above lithium metal compound may be Li2ZnO2, LiZnPO4.

[0104] The above transition metal may be yttrium (Y), and the lithium metal compound may be LiYSiO4, Y-doped LLZO: Li7La3Zr2-xY x O 12 It could be.

[0105] The above transition metal may be zirconium (Zr), and the above lithium metal compound may be Li7La3Zr2O 12 (LLZO), Zr-doped LATP: Li 1.3 Al 0.3 Ti 1.7 Zr 0.3 (PO4)3 may be.

[0106] The above transition metal may be niobium (Nb), and the lithium metal compound may be LiNbO3, Nb-doped LLZO: Li7La3Zr2-xNb x O 12 It could be.

[0107] The above transition metal may be molybdenum (Mo), and the above lithium metal compound may be Li2MoO4, LiMoO2.

[0108] The above transition metal may be ruthenium (Ru), and the above lithium metal compound may be Li2RuO3, LiRuO2.

[0109] The above transition metal may be rhodium (Rh), and the above lithium metal compound may be LiRhO2, Li2RhO3.

[0110] The above transition metal may be palladium (Pd), and the above lithium metal compound may be Li2PdO3, LiPdO2.

[0111] The above transition metal may be silver (Ag), and the above lithium metal compound may be LiAgO2, Li2AgO3.

[0112] The above transition metal may be cadmium (Cd), and the above lithium metal compound may be Li2CdO2, LiCdO2.

[0113] The above transition metal may be hafnium (Hf), and the above lithium metal compound may be Li2HfO3, LiHfO2.

[0114] The above transition metal may be tantalum (Ta), and the above lithium metal compound may be Li3TaO4, LiTaO3.

[0115] The above transition metal may be rhenium (Re), and the above lithium metal compound may be LiReO3, Li2ReO4.

[0116] The above transition metal may be osmium (Os), and the above lithium metal compound may be Li2OsO4, LiOsO2.

[0117] The above transition metal may be iridium (Ir), and the above lithium metal compound may be Li2IrO3, LiIrO2.

[0118] The above transition metals can be of two types, and the two types can be boron (B) and tungsten (W).

[0119] The above lithium metal compound can be expressed by the following chemical formula 1.

[0120] [Chemical Formula 1]

[0121] Li x B y W z O k

[0122] (At this time, 1≤x≤5; 0.1≤y≤2; 0.1≤z≤3; and 5≤k≤15 may be applicable, and preferably 1.5≤x≤4.5; 0.3≤y≤1.8; 0.5≤z≤2.5; and 6≤k≤13 may be applicable.

[0123] More specifically, the lithium metal compound can be expressed by the following chemical formula 2.

[0124] [Chemical Formula 2]

[0125] Li x B y W z O k

[0126] (At this time, 2≤x≤4; 0.5≤y≤1.5; 1≤z≤2.2; and 7≤k≤12.)

[0127] The above lithium metal compound has a problem in that an undesirable phase formation occurs when the composition is outside the above range.

[0128] In one embodiment of the present invention, the thickness of the protective layer (12) may be 200 nm to 5 um, preferably 500 nm to 2 um, and more specifically 1 to 1.5 um. If the thickness of the protective layer (12) is less than 200 nm, it cannot function as a protective layer, and material transfer and electron exchange occur in the SEI layer, forming lithium dendrites. On the other hand, if the thickness exceeds 5 um, there is a problem in that the battery characteristics deteriorate due to the effect of increasing the internal resistance of the cell itself.

[0129] In one embodiment of the present invention, a lithium metal layer (13) may be included located on at least one surface of the protective layer (12) facing the negative electrode current collector (11).

[0130] The above lithium metal layer (13) may be located on one side where the protective layer (12) and the negative electrode current collector (11) are not in contact.

[0131] The above lithium metal layer (13) may be lithium metal or a lithium alloy. At this time, the lithium alloy includes an element capable of alloying with lithium, and specifically, may be an alloy of lithium and at least one selected from the group consisting of Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, and Al.

[0132] The lithium metal layer (13) may be in the form of a sheet or foil, and in some cases, may be in the form of lithium metal or lithium alloy deposited or coated on a current collector by a dry process, or may be in the form of metal and alloy deposited or coated on particles by a wet process, etc. In this case, the method of forming the lithium metal layer (13) is not particularly limited, and known metal thin film forming methods such as lamination and sputtering may be used.

[0133] The above lithium metal layer (13) can have a width adjusted according to the electrode shape to facilitate electrode manufacturing.

[0134] In one embodiment of the present invention, the thickness of the lithium metal layer (13) may be 200 nm to 20 μm, preferably 5 to 20 μm, and more specifically 5 to 10 μm. If the thickness of the lithium metal layer (13) is less than 200 nm, the energy density capacity of the negative electrode decreases, whereas if the thickness exceeds 20 μm, there are problems such as an increase in volume and an increase in stress and deformation of the internal battery.

[0135]

[0136] The second aspect of this article is,

[0137] A method for manufacturing an anode for a lithium secondary battery is provided, comprising: a step (S1) of manufacturing a lithium metal compound by mixing a lithium precursor and one or more transition metal precursors; and a step (S2) of coating a protective layer including the lithium metal compound on an anode current collector.

[0138] Detailed explanations of parts that overlap with the first aspect of the present application have been omitted, but the explanations of the first aspect of the present application may be applied equally even if the explanations are omitted in the second aspect.

[0139]

[0140] Hereinafter, with reference to FIG. 2, a method for manufacturing a negative electrode for a lithium secondary battery according to the second aspect of the present invention will be described in detail.

[0141] In one embodiment of the present invention, S1 is a step of preparing a lithium metal compound by mixing a lithium precursor and one or more transition metal precursors.

[0142] The above lithium precursor may include at least one selected from the group consisting of Li2O, Li2CO3, LIOH, Li2NO3, and combinations thereof.

[0143] The above transition metal precursor may include at least one selected from the group consisting of B2O3, Li2WO4, TiO2, Fe2O3, ZnO, Co3O4, NiO, CuO, MnO2, and combinations thereof.

[0144] The lithium precursor is Li2O, the transition metal precursor is B2O3 and Li2WO4, and the molar ratio of Li2O, B2O3 and Li2WO4 may be 1 to 5: 1: 0.5 to 2. If the ratio is out of the above range, there is a problem that an unwanted phase may be formed, which may cause a deterioration in battery performance.

[0145] The above S1 can synthesize lithium metal compound powder by putting Li2O, B2O3, and Li2WO4 into a ball mill, mixing for 20 to 28 hours, and then heat treating at 500 to 1000°C for 1 to 5 hours.

[0146] In one embodiment of the present invention, S2 is a step of coating a protective layer including the lithium metal compound on the negative electrode current collector.

[0147] The above S2 can manufacture a protective layer by manufacturing the lithium metal compound manufactured in S1 into pellets using a cold press.

[0148] The above coating method can be performed by at least one selected from the group consisting of PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), ALD (Atomic Laser Deposition) and combinations thereof, and can be performed by, for example, RF sputtering.

[0149]

[0150] The third aspect of this foundation is,

[0151] A lithium secondary battery (1) is provided, comprising: a cathode (10) including the above-described contents; a cathode (30); and a separator (20) positioned between the cathode (10) and the cathode (30).

[0152] Detailed explanations of overlapping parts with aspects 1 and 2 of this application have been omitted, but the explanations for aspects 1 and 2 of this application may be applied equally even if the explanations are omitted in aspects 3.

[0153] In one embodiment of the present invention, a conventional separator (20) may be interposed between the anode (30) and cathode (10). The separator (20) is a physical separator having the function of physically separating the electrodes, and can be used without any special restrictions as long as it is used as a conventional separator.

[0154] In addition, the separator (20) separates or insulates the positive electrode (30) and the negative electrode (10) from each other, thereby enabling the transport of lithium ions between the positive electrode (30) and the negative electrode (10). The separator (20) may be made of a porous, non-conductive or insulating material. The separator (20) may be an independent member such as a film, or may be a coating layer added to the positive electrode (30) and / or the negative electrode (10).

[0155] Examples of polyolefin porous membranes that can be used as the above separation membrane (20) include membranes formed from polyolefin polymers such as polyethylene, polypropylene, polybutylene, polypentene, etc., either singly or as a mixture thereof, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.

[0156] Examples of nonwoven fabrics that can be used as the above separation membrane (20) include nonwoven fabrics formed from polymers such as polyphenyleneoxide, polyimide, polyamide, polycarbonate, polyethyleneterephthalate, polyethylenenaphthalate, polybutyleneterephthalate, polyphenylenesulfide, polyacetal, polyethersulfone, polyetheretherketone, and polyester, either singly or in combination, and such nonwoven fabrics include spunbond or meltblown forms composed of long fibers in the form of fibers that form a porous web.

[0157] The thickness of the separator (20) is not particularly limited, but is preferably in the range of 1 to 100 μm, and more preferably in the range of 5 to 50 μm. If the thickness of the separator (20) is less than 1 μm, the mechanical properties cannot be maintained, and if it exceeds 100 μm, the separator (20) acts as a resistance layer, resulting in a decrease in the performance of the battery.

[0158] The pore size and porosity of the above separation membrane (20) are not particularly limited, but the pore size is preferably 0.1 to 50 μm and the porosity is preferably 10 to 95%. If the pore size of the separation membrane (20) is less than 0.1 μm or the porosity is less than 10%, the separation membrane (20) acts as a resistance layer, and if the pore size exceeds 50 μm or the porosity exceeds 95%, the mechanical properties cannot be maintained.

[0159]

[0160] [Explanation of symbols]

[0161] 1: Lithium secondary battery

[0162] 10: Cathode

[0163] 11: Negative current collector

[0164] 12: Protective layer

[0165] 13: Lithium metal layer

[0166] 20: Membrane

[0167] 30: Bipolar

[0168]

[0169] According to an embodiment of the present invention, a negative electrode for a lithium secondary battery has an advantage in that it has better performance than a conventional lithium secondary battery by suppressing the formation of lithium dendrites formed by SEI that are formed unevenly as the cycle continues by coating a lithium metal compound on the negative electrode current collector in contact with lithium metal, and thus has industrial applicability in the field of negative electrodes for lithium secondary batteries.

Claims

1. Negative current collector; A protective layer positioned on at least one surface of the negative electrode current collector and comprising a lithium metal compound; and A lithium metal layer positioned on at least one surface of the protective layer; The above lithium metal compound is a negative electrode for a lithium secondary battery, comprising lithium (Li), oxygen (O) and one or more transition metals.

2. In paragraph 1, A negative electrode for a lithium secondary battery, wherein the thickness of the negative electrode current collector is 1 nm to 100 nm.

3. In paragraph 1, A negative electrode for a lithium secondary battery, wherein the transition metal comprises at least one selected from the group consisting of boron (B), tungsten (W), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), hafnium (Hf), tantalum (Ta), rhenium (Re), osmium (Os), and iridium (Ir).

4. In paragraph 1, The above lithium metal compound is a negative electrode for a lithium secondary battery, represented by the following chemical formula 1. [Chemical Formula 1] Li x B y W z O k (At this time, 1≤x≤5; 0.1≤y≤2; 0.1≤z≤3; and 5≤k≤15.) 5. In paragraph 1, The above lithium metal compound is a negative electrode for a lithium secondary battery, represented by the following chemical formula 2. [Chemical Formula 2] Li x B y W z O k (At this time, 2≤x≤4; 0.5≤y≤1.5; 1≤z≤2; and 7≤k≤12.) 6. In paragraph 1, A negative electrode for a lithium secondary battery, wherein the thickness of the protective layer is 200 nm to 5 μm.

7. A step of preparing a lithium metal compound by mixing a lithium precursor and one or more transition metal precursors; and A method for manufacturing a negative electrode for a lithium secondary battery, comprising the step of coating a protective layer containing the lithium metal compound on a negative electrode current collector.

8. In paragraph 7, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the lithium precursor comprises at least one selected from the group consisting of Li2O, Li2CO3, LiOH, Li2NO3, and combinations thereof.

9. In paragraph 7, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the transition metal precursor comprises at least one selected from the group consisting of B2O3, Li2WO4, TiO2, Fe2O3, ZnO, Co3O4, NiO, CuO, MnO2, and combinations thereof.

10. In paragraph 7, The above lithium precursor is Li2O, The above transition metal precursors are B2O3 and Li2WO4, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the above Li2O, B2O3 and Li2WO4 have a molar ratio of 1 to 5: 1: 0.5 to 2.

11. In paragraph 7, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the coating step is performed by at least one method selected from the group consisting of PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), ALD (Atomic Laser Deposition), and combinations thereof.

12. In paragraph 7, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the above coating step is performed by RF sputtering.

13. A cathode according to any one of paragraphs 1 to 6; Bipolar; and A lithium secondary battery, comprising a separator positioned between the negative electrode and the positive electrode.

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