Electrolyte additive containing a metal nitrate, lithium metal battery using the same, and method for manufacturing the same.

Abstract

One embodiment of the present invention provides an intermediate layer manufactured from an electrolyte additive on which a large amount of metal nitrate is supported by electrospinning of a polymer solution in which metal nitrate is dissolved, and by further incorporating the intermediate layer into a lithium metal battery using a carbonate electrolyte, a lithium metal battery is provided that has significantly superior electrochemical performance and stability compared to existing commercial lithium metal batteries using carbonate electrolytes.

Description

Technical Field

[0001] Cross-reference of related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0063582 filed on May 17, 2023, and Korean Patent Application No. 10-2024-0063612 filed on May 16, 2024, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to an electrolyte additive containing a metal nitrate, a lithium metal battery using the same, and a method for manufacturing the same. More specifically, in order to enhance the stability of a carbonate electrolyte for a high-capacity lithium metal battery, while inducing uniform lithium electro-desorption, and at the same time forming a stable solid electrolyte interphase (SEI), it relates to an electrolyte additive for manufacturing an intermediate layer, a lithium metal battery using the same, and a method for manufacturing the same.

Background Art

[0003] A lithium metal battery is a secondary battery using a lithium metal as a negative electrode material and is a battery system having a high energy density. The lithium metal negative electrode has a higher driving voltage and a theoretical capacity more than 10 times higher (372 mAh / g vs. 3860 mAh / g) than the graphite negative electrode used in existing lithium-ion batteries, so it can store more energy.

[0004] However, the lithium metal negative electrode has a high risk of short circuit and fire, and improvement in stability is required for commercialization. Lithium causes side reactions with the electrolyte, consumes the electrolyte to form a solid electrolyte interphase (SEI), and forms dendritic crystals during deposition on the electrode. The thick SEI generated during the charge-discharge process due to the increase in surface area by dendrites and the lithium detached from the electrode increase the overvoltage and cause electrode degradation.

[0005] To increase the capacity of lithium-ion batteries, metal oxide cathode materials are used, and carbonate electrolytes, which have a wide voltage window and are relatively inexpensive, have been commercially available. However, carbonate electrolytes used in lithium metal batteries have low stability, and for this reason, ether electrolytes, which have a narrow voltage window but high stability, have been used together with cathode materials that have a low driving voltage.

[0006] Recently, various electrolyte additive technologies have been developed to solve these problems, but most of them use high-concentration ether electrolytes, which are expensive and still difficult to use at high voltages. This not only increases the price of batteries but also makes it difficult to drive full cells using various cathode materials.

[0007] Therefore, in order to drive a full cell of a stable lithium metal battery, it is necessary to induce uniform lithium desorption by adding additives to the carbonate electrolyte, while simultaneously forming a stable SEI (Single-Acoustic Inclusion). However, with previously known electrolyte additives, the low solubility in the carbonate solvent and electrolyte leads to premature depletion during battery charging and discharging, making it difficult to form a stable SEI and thus preventing a sufficient improvement in the lifespan characteristics of lithium metal batteries. [Overview of the project] [Problems that the invention aims to solve]

[0008] The technical problem that this invention aims to solve is to provide an electrolyte additive for manufacturing an intermediate layer that can overcome the limited solubility of nitrates in high-capacity lithium metal batteries, enhance the stability of the carbonate electrolyte, induce uniform lithium desorption, and simultaneously form a stable SEI, as well as a lithium metal battery using the same and a method for manufacturing the same.

[0009] The technical problems that this invention aims to solve are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary skill in the art to which this invention pertains from the following description. [Means for solving the problem]

[0010] To achieve the above technical challenges, one embodiment of the present invention provides an electrolyte additive comprising a polymer nanofiber structure and a metal nitrate supported on the polymer nanofiber structure, wherein the metal nitrate includes lithium nitrate or rubidium nitrate.

[0011] In embodiments of the present invention, the polymer nanofiber structure may include polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), or polyacrylonitrile (PAN), and may include fibers obtained by electrospun from these polymers.

[0012] In the embodiments of the present invention, the polymer nanofiber structure may have a fiber diameter of 100 to 500 nm.

[0013] In the embodiments of the present invention, the metal nitrate may be present in an amount of 10 to 70% by weight relative to the total weight of the electrolyte additive.

[0014] To achieve the above technical challenges, another embodiment of the present invention provides a lithium metal battery comprising: a lithium metal anode; a nanofiber-shaped intermediate layer disposed on the anode and manufactured from an electrolyte and an electrolyte additive; a separation membrane disposed on the intermediate layer; and a positive electrode disposed on the separation membrane.

[0015] In an embodiment of the present invention, a solid electrolyte interphase (SEI) can be formed on the intermediate layer, in which the ionic conductivity is improved by nitrate anions produced by the decomposition of metal nitrates.

[0016] Furthermore, the intermediate layer can have a thickness of 10 to 40 μm.

[0017] To achieve the above technical challenges, yet another embodiment of the present invention provides a method for manufacturing a lithium metal battery, comprising the steps of: preparing an electrolyte additive which is a mixture of a polymer and a metal nitrate; manufacturing an intermediate layer from the electrolyte and the electrolyte additive; and arranging a lithium metal negative electrode below the intermediate layer and sequentially arranging a separation membrane and a positive electrode above the intermediate layer.

[0018] In the embodiments of the present invention, in the step of preparing the electrolyte additive, the mixed weight ratio of the metal nitrate and the polymer may be 1:2 to 3:1.

[0019] In the embodiment of the present invention, the step of producing the intermediate layer may be carried out by electrospinning.

[0020] In the embodiments of the present invention, the electrospinning method may be carried out under the application of a voltage of 8kV to 25kV. [Effects of the Invention]

[0021] According to embodiments of the present invention, by providing an electrolyte and an electrolyte additive, which is a polymer solution in which a predetermined metal nitrate is dissolved, to an electrospinning process, an intermediate layer on which a large amount of metal nitrate is supported can be produced. This makes it possible to provide a lithium metal battery with significantly superior electrochemical performance and stability compared to existing commercially available lithium metal batteries using carbonate electrolytes.

[0022] The lithium metal battery according to the present invention includes an intermediate layer manufactured from an additive on which nitrate is supported. The anions can form a solid electrolyte interphase (SEI) consisting of a large amount of inorganic compound, and simultaneously, the cations can induce uniform lithium deposition through nucleation seeding or charge shielding effect.

[0023] It should be understood that the effects of the present invention are not limited to those described above, but include all effects that can be inferred from the detailed description of the present invention or the configuration of the invention as described in the claims. [Brief explanation of the drawing]

[0024] [Figure 1] The schematic structure of a lithium metal battery containing a PAN intermediate layer on which a metal nitrate is supported, according to one embodiment of the present invention, is shown. [Figure 2] A schematic diagram shows a method for producing a PAN intermediate layer supported with a metal nitrate according to one embodiment of the present invention, and an example of an electrospinning apparatus applied thereto. [Figure 3] This diagram shows the expected effects when the manufactured intermediate layer is applied to a lithium metal battery. [Figure 4] The image shows the scanning electron microscope (SEM) analysis according to Example 1. [Figure 5] The image shows the scanning electron microscope (SEM) analysis according to Example 2. [Figure 6] The image shows an SEM analysis of the intermediate layer (CsPAN) formed by a PAN nanofiber layer supported with CsNO3 according to Example 3. [Figure 7] This graph shows the Coulomb efficiency over cycles of a half-cell to evaluate lithium reversibility in comparative examples and examples. [Figure 8] These images were obtained by scanning electron microscopy and focused ion beam (FIB) cross-sectional analysis to evaluate the electrodeposition shape of lithium electrodes in comparative examples and examples. [Figure 9] The results show the capacity and Coulomb efficiency per cycle for the overall battery performance evaluation using comparative examples and examples. [Modes for carrying out the invention]

[0025] The present invention will be described below with reference to the accompanying drawings. However, the present invention can be realized in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly illustrate the present invention in the drawings, unnecessary parts have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0026] Throughout the specification, when a part is described as being "connected (linked, in contact with, or joined)" to another part, this includes not only cases where they are "directly connected" but also cases where they are "indirectly connected" with other components in between. Furthermore, when a part is described as "containing" a certain component, this means, unless otherwise stated, that it may further contain other components rather than excluding them.

[0027] The terms used herein are used solely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “includes” or “having” specify the presence of features, figures, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood not to preemptively exclude the possibility of the presence or addition of one or more other features, figures, steps, actions, components, parts, or combinations thereof.

[0028] The embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0029] "LiPAN" refers to an intermediate layer formed from PAN nanofiber layers supported with lithium nitrate (LiNO3).

[0030] "RbPAN" refers to an intermediate layer formed from PAN nanofiber layers supported with rubidium nitrate (RbNO3).

[0031] An electrolyte additive according to one embodiment of the present invention comprises a polymer nanofiber structure and a metal nitrate supported on the polymer nanofiber structure, the metal nitrate of which may include lithium nitrate or rubidium nitrate. Since the polymer intermediate layer produced from the electrolyte additive is located between the lithium anode and the separation membrane in a lithium metal battery, the metal nitrate supported on the polymer nanofiber structure readily reacts with the lithium anode and acts as an additive.

[0032] The polymer nanofiber structure may include polymers selected from the group including polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), or polyacrylonitrile (PAN), and these polymers can be electrospun to form polymer nanofiber structures having a fibrous shape.

[0033] In such polymer nanofiber structures, each fiber can have a fiber diameter of, for example, 100-500 nm or 150-450 nm, and these nanofibers can have a shape in which they are intertwined with one another.

[0034] The aforementioned metal nitrate may be included in the intermediate layer or electrolyte additive in an amount of 10 to 70% by weight relative to the total weight.

[0035] Figure 1 shows a schematic structure of a lithium metal battery containing a PAN intermediate layer on which a metal nitrate is supported, according to one embodiment of the present invention.

[0036] A lithium metal battery according to another embodiment of the present invention will be described with reference to Figure 1.

[0037] A lithium metal battery according to one embodiment of the present invention may include a lithium metal negative electrode, an intermediate layer in the form of a nanofiber structure manufactured from an electrolyte and an electrolyte additive, a separation membrane disposed on the intermediate layer, and a positive electrode disposed on the separation membrane.

[0038] Figure 2 schematically shows a method for producing a PAN intermediate layer supported with a metal nitrate according to one embodiment of the present invention, and an example of an electrospinning apparatus applied thereto.

[0039] Referring to Figure 2, a method for manufacturing a lithium metal battery according to yet another embodiment of the present invention will be described below.

[0040] A method for manufacturing a lithium metal battery according to one embodiment of the present invention may include the steps of: preparing an electrolyte additive which is a mixture of a polymer and a metal nitrate; manufacturing an intermediate layer from the electrolyte and the electrolyte additive; and arranging a lithium metal negative electrode below the intermediate layer and sequentially arranging a separation membrane and a positive electrode above the intermediate layer.

[0041] First, there is a step of preparing an electrolyte additive, which is a mixture of a polymer and a metal nitrate. The mixture is prepared by dissolving and dispersing the metal nitrate and the polymer, for example, a polymer selected from the group including polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), or polyacrylonitrile (PAN), together in a solvent. At this time, DMF (Dimethyl Formamide) can be used as the solvent.

[0042] The step of preparing the electrolyte additive may be carried out under an inert gas atmosphere. This is to prevent water from being incorporated into the mixture during the process of dissolving and dispersing the metal nitrate and polymer in the solvent.

[0043] In the step of preparing the electrolyte additive, the mixing ratio of the metal nitrate and the polymer may be 1:2 to 3:1.

[0044] Next, there is a step of manufacturing an intermediate layer. This step of manufacturing the intermediate layer may be carried out by electrospinning. By such electrospinning, the polymer nanofiber structure can be obtained from the polymer.

[0045] Electrospinning is a method for producing nanofibers by dissolving or melting a polymer and extruding it through a spinneret. It allows for the creation of thin nanofibers with a large surface area per unit weight and high porosity. The intermediate layer in the embodiment of the present invention can be obtained as a polymer nanofiber structure by transforming a PAN polymer dissolved in a solvent into a nanofiber shape using electrospinning. The surface area of ​​the metal nitrate can be increased depending on the degree of dispersion.

[0046] The applied voltage range when performing the electrospinning method described above may be 8kV to 25kV. If the voltage range is lower than 8kV, electrospinning may not occur, and if it is higher than 25kV, the fibers may not be spun into a nanofiber shape. However, the voltage range is not limited to this and may vary depending on the concentration of the mixture, the additives, or the spinning distance.

[0047] Furthermore, a step of drying the intermediate layer may be included. After electrospinning is complete, it can be dried in a vacuum oven to confirm that the nanofiber-shaped intermediate layer is finally synthesized.

[0048] Finally, a lithium metal negative electrode can be placed below the intermediate layer, and a separator membrane and a positive electrode can be sequentially placed above the intermediate layer to manufacture a lithium metal battery.

[0049] The polymer nanofiber structure and the polymer intermediate layer containing the metal nitrate are manufactured by electrospinning. Additives with low solubility and difficulty in being applied to electrolytes can be supported in large quantities via the polymer intermediate layer. The supported additives dissolve slowly in the electrolyte and exert their effects over a long period of time, and when used in lithium metal batteries, the stability of lithium metal can be improved.

[0050] Figure 3 shows a schematic diagram of the expected effects when the manufactured intermediate layer is applied to a lithium metal battery.

[0051] Referring to FIG. 3, a solid electrolyte interphase (SEI) with improved ionic conductivity can be formed by nitrate anions due to the decomposition of metal nitrates in the intermediate layer. On the other hand, metal cations due to the decomposition of metal nitrates in the intermediate layer are reduced to a metallic form on the lithium surface and act as nucleation seeds, and can induce uniform lithium electrodeposition.

[0052] When the intermediate layer is applied to the lithium metal anode in this way, a stable SEI can be formed by the decomposition of metal nitrates, and metal ions show a uniform lithium electrodeposition shape according to their types.

[0053] On the other hand, the lithium metal battery includes a lithium metal anode, and can follow the configuration of a general lithium metal secondary battery except for including the intermediate layer containing the polymer nanofiber structure and metal nitrates.

[0054] In such a lithium metal battery, an electrolyte solution containing a non-aqueous organic solvent and a lithium salt can be supported in the intermediate layer.

[0055] The lithium salt contained in the electrolyte solution is used as a medium for transmitting ions in the secondary battery. The lithium salt contains, for example, Li as a cation + and includes F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 -, (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - , C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2) 2CH - CF3(CF2)7SO3 - and SCN - It can also contain anions selected from the group consisting of the following.

[0056] Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10 It may contain one or more substances selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBF2 (C2O4), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2, and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2).

[0057] The concentration of the lithium salt can be appropriately changed within a range that is normally usable, and may be included in the electrolyte at a concentration of 0.4 M to 6 M, or 0.5 M to 5 M.

[0058] On the other hand, the type of non-aqueous organic solvent included in the electrolyte is not particularly limited, and any organic solvent known to be applicable to lithium-ion battery electrolytes can be used. Examples of such organic solvents include one or more selected from the group consisting of carbonate-based solvents, ether-based solvents, nitrile-based solvents, phosphate-based solvents, and sulfone-based solvents.

[0059] More specifically, as the carbonate-based solvent, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, methyl propyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate, or methyl (2,2,2-trifluoroethyl) carbonate can be used, and as the phosphate-based solvent, trimethyl phosphate, triethyl phosphate, or 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphosphorane 2-oxide can be used.

[0060] Furthermore, as the ether-based solvent, dibutyl ether, tetraglyceride, diglyme, dimethoxyethane, or tetrahydrofuran derivatives such as 2-methyltetrahydrofuran can be used, and as the nitrile-based solvent, succinonitrile, adiponitrile, sebaconitrile, acetonitrile, or propionitrile can be used. Furthermore, as the sulfone-based solvent, dimethyl sulfone, ethyl methyl sulfone, or sulforane can be used.

[0061] On the other hand, in the lithium metal battery, the positive electrode may include a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector.

[0062] Such a positive electrode can be manufactured by mixing an active material, a binder, and optionally a conductive material, a filler, etc. in a solvent to produce a positive electrode slurry composition, and applying this to a positive electrode current collector.

[0063] The positive electrode current collector can generally have a thickness of 3 to 500 μm. Further, the positive electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. The current collector can also form fine irregularities on its surface to enhance the adhesion of the positive electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc. are possible.

[0064] And the positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, specifically, it can contain a lithium metal oxide containing one or more metals such as iron, cobalt, manganese, nickel or aluminum and lithium.

[0065] Specifically, the lithium metal oxide is a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1O4 (where 0 < Z1 < 2, etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2, etc.), lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1, etc.), or lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (where M is one or more selected from Al, Mg, and Ti, X is one or more selected from F, S, and N, -0.5 ≤ a ≤ +0.5, 0 ≤ x ≤ 0.5, 0 ≤ b ≤ 0.1, etc.), and any one or two or more of these compounds may be included.

[0066] Among them, the positive electrode active material includes lithium; and a lithium metal oxide containing two or more metals selected from the group consisting of nickel, manganese, cobalt, and aluminum, and the lithium metal oxide may contain 50 mol% or more, or 60 to 99 mol%, or 70 to 95 mol% of nickel based on the total metal content excluding lithium. Such a lithium metal oxide may be represented, for example, by the following Chemical Formula 1: [Chemical Formula 1] Li x Ni a Co b M 1 cM 2 d O2 In the above chemical formula 1, the above M 1 M may be one or more selected from Mn and Al, or a combination thereof. 2 a may be one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S, and may be 0.90≦x≦1.1, or 0.95≦x≦1.08, or 1.0≦x≦1.08, and may be 0.50≦a<1.0, or 0.60≦a≦0.99, or 0.70≦a≦0.95. Also, 0 <b≦0.3であり、0<c≦0.3であり、0≦d≦0.1であってもよい。

[0067] By using a lithium metal oxide containing such a high nickel content as the positive electrode active material and combining it with the negative electrode of one embodiment, the output, capacity characteristics, and lifespan characteristics of the lithium metal battery can be further improved.

[0068] The positive electrode active material described above may be present in an amount of 60-99% by weight, 70-99% by weight, or 80-98% by weight, based on the total weight of the positive electrode active material layer.

[0069] On the other hand, the conductive material contained in the positive electrode active material layer is a component that further improves the conductivity of the positive electrode active material, and such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive nanomaterials such as carbon nanofibers or carbon nanotubes; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used. In particular, by including conductive nanomaterials such as carbon nanotubes or carbon nanofibers in the conductive material, the resistance of the lithium metal battery can be further reduced and the output characteristics can be further improved.

[0070] Typically, the conductive material may be present in an amount of 1 to 20% by weight, 1 to 15% by weight, or 1 to 10% by weight, based on the total weight of the positive electrode active material layer.

[0071] The binder selectively included in the positive electrode active material layer is a component that supports the bonding of the positive electrode active material to conductive materials and to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, nitrile rubber, styrene-butadiene rubber, or fluororubber, and a mixture or copolymer of two or more selected from these may be used.

[0072] Typically, the binder may be present in an amount of 1 to 20% by weight, 1 to 15% by weight, or 1 to 10% by weight, based on the total weight of the positive electrode active material layer.

[0073] On the other hand, the lithium metal battery described above may further include a porous separator membrane interposed between the positive and negative electrodes. More specifically, the separator membrane may be located between the intermediate layer and the positive electrode.

[0074] Such porous separation membranes can be used in the form of sheets, multilayer membranes, fine porous films, woven fabrics, and nonwoven fabrics, but are not necessarily limited to these forms. However, it is preferable to use porous polyethylene or porous glass fiber nonwoven fabric (glass filter) as the separation membrane, and it is even more preferable to use a porous glass filter (glass fiber nonwoven fabric) as the separation membrane. The separation membrane may be a thin insulating film with high ion permeability and mechanical strength, and the pore size of the separation membrane may generally be in the range of 0.01 to 10 μm, and the thickness may generally be in the range of 5 to 300 μm, but is not limited to these.

[0075] The following describes embodiments, comparative examples, and experimental examples of the invention in detail.

[0076] Comparative Example 1 shows a lithium metal battery without an intermediate layer, using a carbonate electrolyte (1M LiPF6in EC / DEC / FEC) and a lithium metal anode; Example 1 shows a lithium metal battery including a PAN intermediate layer without metal nitrates; Example 2 shows a lithium metal battery including a LiPAN nanofiber intermediate layer to which lithium nitrate is added as a metal nitrate; and Example 3 shows a lithium metal battery including an RbPAN nanofiber intermediate layer to which rubidium nitrate is added as a metal nitrate.

[0077] Comparative Example 1: Carbonate electrolyte without metal nitrate additives (1M LiPF6in EC / DEC / FEC, 45:45:10) A commercially available 1M LiPF6in EC / DEC / FEC electrolyte was used, which is a lithium-ion battery electrolyte with a standard structure (1M LiPF6in EC / DEC) to which 10 volume% of FEC has been added.

[0078] Example 1: Polymer nanofiber (PAN) intermediate layer without added metal nitrates A mixture (PAN / DMF) was prepared by mixing 7% by weight of polyacrylonitrile (PAN) with DMF solvent and stirring for 12 hours until completely dissolved. The mixture was transferred to a Luer lock syringe and fitted with an electrospinning needle. The electrospinning conditions were a voltage of 15-20kV, a flow rate of 0.5-1ml / hr, and a spinning distance of approximately 15cm. The electrospinned aluminum foil was dried in a vacuum oven at a temperature of approximately 60°C for more than 12 hours under a vacuum atmosphere.

[0079] Figure 4 shows a scanning electron microscope (SEM) analysis image from Example 1. From Figure 4, it can be confirmed that an intermediate layer in the shape of nanofibers is synthesized by the electrospinning method of the above example.

[0080] Example 2: LiPAN nanofiber interlayer In Example 2, a polymer nanofiber (PAN) intermediate layer supported with lithium nitrate (LiNO3) was used as the intermediate layer in Example 1.

[0081] In Example 2, lithium nitrate was further dissolved in the PAN-DMF mixture prepared as in Example 1 at a weight ratio of 2:3 to 4:5 with PAN to produce a mixture containing the additive (LiNO3-PAN / DMF). To prevent the inclusion of water during the dissolution and dispersion process, the process was carried out in a glove box under an argon atmosphere and stirred for approximately 12 hours. The mixture was transferred to a Luer lock syringe and an electrospinning needle was attached. The electrospinning conditions were a voltage of 15-20kV, a flow rate of 0.3-0.5ml / hr, and a spinning distance of approximately 15cm. The electrospinned aluminum foil was dried in a vacuum oven at a temperature of approximately 60°C for more than 12 hours under a vacuum atmosphere.

[0082] Figure 5 shows a scanning electron microscope (SEM) analysis image from Example 2. From Figure 5, it can be confirmed that a nanofiber-shaped intermediate layer is synthesized by the electrospinning method of Example 2, and that an intermediate layer with uniformly supported LiNO3 is synthesized.

[0083] Example 3: RbPAN nanofiber interlayer In Example 3, a polymer nanofiber (PAN) intermediate layer supported with rubidium nitrate (RbNO3) was used in the intermediate layer of Example 1.

[0084] In Example 3, the particle size of rubidium nitrate was reduced by a ball milling process using a stainless steel ball milling bottle and zirconia balls.

[0085] In Example 3, approximately 5 μm RbPAN particles, obtained by a ball milling process for about 2 hours, were dissolved and dispersed in the DMF solvent along with the PAN-DMF mixture prepared as in Example 1, in a weight ratio of approximately 1:1. To prevent the inclusion of water during the dissolution and dispersion process, the process was carried out in a glove box under an argon atmosphere and stirred for approximately 12 hours. The PAN polymer was completely dissolved and the RbNO3 particles were uniformly dispersed to produce a suspension (RbNO3-PAN / DMF).

[0086] Subsequently, the dispersion of RbNO3 particles was further increased by sonication. The prepared suspension was transferred to a Luer lock syringe and an electrospinning needle was attached. Electrospinning was carried out in two stages on an aluminum foil substrate. To prevent RbNO3 particles from adhering to the aluminum foil, in the first stage, 1 ml of PAN / DMF solution was electrospinned. In the second stage, approximately 6 ml of RbNO3-PAN / DMF suspension was electrospinned. The electrospinning conditions were a voltage of 15-20 kV, a flow rate of 0.5-1.0 ml / hr, and a spinning distance of approximately 15 cm.

[0087] The electrospun aluminum foil was dried in a vacuum oven at a temperature of approximately 60°C for more than 12 hours under vacuum conditions.

[0088] Figure 6 shows an SEM analysis image of the intermediate layer (RbPAN) formed by the PAN nanofiber layer supporting RbNO3 according to Example 3. From Figure 6, it can be confirmed that the nanofiber-shaped intermediate layer is synthesized by the electrospinning method of Example 3, and that the dispersed RbNO3 particles are uniformly synthesized together.

[0089] Experimental example The following describes the evaluation of the electrochemical activity of the lithium metal battery of Comparative Example 1 and the lithium metal batteries using the intermediate layers of Examples 1 to 3.

[0090] Figure 7 is a graph showing the Coulomb efficiency for the cycle of a copper-lithium half-cell to evaluate the lithium reversibility of comparative examples and examples of the present invention.

[0091] Referring to Figure 7, the evaluation condition is 1 mA·cm -2 and 1mAh·cm -2 The ratio of the desorption capacity to the electrodeposition capacity of lithium is expressed as the Coulomb efficiency. Comparative Example 1 and Example 1 were found to have relatively low Coulomb efficiency and lifespan, while Examples 2 and 3 showed higher Coulomb efficiency and superior lifespan compared to Comparative Example 1 and Example 1.

[0092] Figure 8 shows images obtained by scanning electron microscopy and focused ion beam (FIB) cross-sectional analysis to evaluate the electrodeposition shape of lithium electrodes according to comparative examples and examples of the present invention.

[0093] Referring to Figure 8, it can be seen that in Comparative Example 1 and Example 1, locally dendrite-shaped lithium was electrodeposited on the surface, which is also visible as a thick, porous lithium layer in the cross-sectional image. In Examples 2 and 3, where lithium nitrate or rubidium nitrate was added, it can be seen that the dendrite morphology was suppressed in the lithium electrodeposition shape, resulting in the formation of a relatively thin lithium layer.

[0094] Figure 9 shows the results of the overall battery performance evaluation using comparative examples and examples of the present invention, illustrating the capacity and Coulomb efficiency per cycle. Here, the working electrode is NCM811(LiNi 0.8 Co 0.1 Mn 0.1 Using an O2 electrode, 20 μm lithium foil was used for the relative electrode and reference electrode, and the evaluation condition was 1 mA·cm. -2 (0.29C) Charge and discharge tests were carried out under cutoff voltage conditions of 3V to 4.3V.

[0095] Referring to Figure 9, it can be seen that Examples 2 and 3 maintain high Coulomb efficiency and stable capacity for 100 cycles, thus demonstrating that they can be utilized even with a full battery.

[0096] The above description of the present invention is illustrative, and a person with ordinary skill in the art to which the invention pertains will understand that it can be readily modified in other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described in a distributed manner may be implemented in a combined manner.

[0097] The scope of this invention is defined by the claims set forth below, and all modifications or altered forms derived from the meaning and scope of the claims, as well as the concept of equivalents thereof, should be construed as being included within the scope of this invention.

Claims

1. Polymer nanofiber structures and A metal nitrate supported on the polymer nanofiber structure, Includes, The aforementioned metal nitrate is an electrolyte additive containing lithium nitrate or rubidium nitrate.

2. The electrolyte additive according to claim 1, wherein the polymer nanofiber structure comprises one or more selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN).

3. The electrolyte additive according to claim 1, wherein the polymer nanofiber structure has a fiber diameter of 100 to 500 nm.

4. The electrolyte additive according to claim 1, wherein the metal nitrate is present in an amount of 10 to 70% by weight relative to the total weight of the electrolyte additive.

5. Lithium metal anode and Displaced on the negative electrode, the intermediate layer is in the shape of nanofibers and is manufactured from an electrolyte and an electrolyte additive according to any one of claims 1 to 4, A separation membrane disposed on the intermediate layer, A positive electrode disposed on the separation membrane, Lithium metal batteries, including those containing lithium metal.

6. The lithium metal battery according to claim 5, wherein a solid electrolyte interface (SEI) is formed on the intermediate layer, the ionic conductivity of which is improved by nitrate anions produced by the decomposition of metal nitrates.

7. The lithium metal battery according to claim 5, wherein the intermediate layer has a thickness of 10 to 40 μm.

8. The steps include: preparing an electrolyte additive which is a mixture of polymer and metal nitrate; A step of manufacturing an intermediate layer from an electrolyte and an electrolyte additive, The steps include placing a lithium metal negative electrode at the bottom of the intermediate layer and sequentially placing a separation membrane and a positive electrode at the top of the intermediate layer, A method for manufacturing lithium metal batteries, including [the specified component].

9. The method for manufacturing a lithium metal battery according to claim 8, wherein, in the step of preparing the electrolyte additive, the mixed weight ratio of the metal nitrate and the polymer is 1:2 to 3:

1.

10. The method for manufacturing a lithium metal battery according to claim 8, wherein the step of manufacturing the intermediate layer is carried out by an electrospinning method.

11. The method for manufacturing a lithium metal battery according to claim 10, wherein the electrospinning method is performed under an applied voltage of 8 kV to 25 kV.

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