KR102429876B1 - Negative electrode for lithium metal battery and lithium metal battery comprising the same - Google Patents

Abstract

a lithium metal electrode comprising lithium metal or a lithium metal alloy; and a protective film disposed on at least a portion of the lithium metal electrode, wherein the protective film has a Young's modulus of 10 ⁶ Pa or more, and has a size of greater than 1 µm and less than or equal to 100 µm. Particles), inorganic particles and organic-inorganic particles (organic-inorganic particles) are disclosed a negative electrode for a lithium metal battery comprising at least one particle selected from, and a lithium metal battery including the same.

Description

Negative electrode for lithium metal battery and lithium metal battery comprising the same

A negative electrode for a lithium metal battery and a lithium metal battery including the same are provided.

A lithium secondary battery is a high-performance secondary battery having the highest energy density among currently commercialized secondary batteries, and may be used in various fields such as, for example, an electric vehicle.

A lithium metal thin film may be used as the negative electrode of the lithium secondary battery. When such a lithium metal thin film is used as an anode, it has high reactivity with a liquid electrolyte during charging and discharging due to the high reactivity of lithium. Alternatively, since dendrites are formed on the lithium anode thin film, the lifespan and stability of a lithium secondary battery employing a lithium metal thin film may be reduced, and improvement is required.

One aspect is to provide an anode for a lithium metal battery having a protective film having excellent mechanical properties.

Another aspect is to provide a lithium metal battery with improved cell performance including the above-described negative electrode.

according to one side

a lithium metal electrode comprising lithium metal or a lithium metal alloy; and

and a protective film disposed on at least a portion of the lithium metal electrode,

The Young's modulus of the protective film is 10 ⁶ Pa or more,

A negative electrode for a lithium metal battery comprising at least one particle selected from organic particles, inorganic particles and organic-inorganic particles having a size exceeding 1 μm and less than 100 μm is provided

Anode according to another aspect; the negative electrode described above; and a lithium metal battery including an electrolyte interposed therebetween.

The negative electrode for a lithium metal battery according to an embodiment has a protective film having improved mechanical properties. By using such a negative electrode, it is possible to manufacture a lithium metal battery that effectively suppresses volume change during charging and has improved cycle life and discharge capacity.

1A to 1D schematically show the structure of an anode for a lithium metal battery according to an embodiment.
1e and 1f are diagrams for explaining the principle of operation of the protective film inhibiting and guiding the growth of lithium dendrites in the negative electrode for a lithium metal battery according to an embodiment.
1G to 1K are diagrams schematically showing the structure of a lithium metal battery according to an embodiment.
11 is for explaining the protective role of the lithium metal electrode when the particle diameter of the microspheres contained in the protective film exceeds about 1 μm and is less than or equal to 100 μm in the negative electrode for a lithium metal battery according to an embodiment.
Figure 1m is for explaining the protective role of the lithium metal electrode when the average particle diameter of the microspheres contained in the protective film in the negative electrode for a lithium metal battery is 1 ㎛ or less.
2a to 2d are scanning electron microscope (SEM) pictures of the cathode prepared according to Example 1.
3A to 3C are SEM photographs of the lithium negative electrode prepared according to Example 4.
3D is an SEM photograph of the lithium negative electrode prepared according to Example 22.
4A schematically shows a structure in which a lithium negative electrode is formed on a copper thin film, which is an anode current collector, in a lithium metal battery manufactured according to Example 9. Referring to FIG.
4b and 4c are SEM photographs showing the surface of the anode in the lithium metal battery prepared according to Example 9;
FIG. 4d is an SEM photograph showing a cross-sectional state in which a lithium electrodeposition layer is formed on an anode in a lithium metal battery manufactured according to Example 9;
5A schematically shows a structure in which a lithium negative electrode is formed on a copper thin film, which is an anode current collector, in a lithium metal battery prepared according to Comparative Example 1.
5b and 5c show the surface of the lithium metal negative electrode in the lithium metal battery prepared according to Comparative Example 1.
FIG. 5d is an SEM photograph showing a cross-sectional state of a lithium anode in which a lithium electrodeposition layer is formed on an upper portion of a lithium metal anode in a lithium metal battery prepared according to Comparative Example 1. FIG.
6 shows impedance measurement results of lithium metal batteries prepared according to Example 17 and Comparative Example 1. FIG.
7 shows changes in capacity retention rate for lithium metal batteries prepared according to Example 9 and Comparative Example 1. FIG.
8A and 8B show changes in discharge capacity and capacity retention rate for lithium metal batteries prepared according to Example 17 and Comparative Example 1. FIG.
FIG. 8c is a graph showing changes in Coulomb efficiency of lithium metal batteries prepared according to Example 17 and Comparative Example 1. FIG.
9A to 9C illustrate a state in which particles are disposed on a surface of a lithium metal in a protective film according to an exemplary embodiment.

Hereinafter, an exemplary negative electrode for a lithium metal battery and a lithium metal battery including the same will be described in detail with reference to the accompanying drawings.

a lithium metal electrode comprising lithium metal or a lithium metal alloy; and a protective film disposed on at least a portion of the lithium electrode,

The Young's modulus of the protective film is 10 ⁶ Pa or more,

There is provided a negative electrode for a lithium metal battery comprising at least one particle selected from organic particles, inorganic particles, and organic/inorganic particles having a size of greater than 1 μm and less than or equal to 100 μm.

Since lithium metal or lithium metal alloy has a large electric capacity per unit weight, it is possible to realize a high-capacity battery by using the lithium metal or lithium metal alloy. However, in the case of lithium metal or lithium metal alloy, dendrites may grow during the lithium ion desorption/attachment process to cause a short circuit between the positive electrode and the negative electrode. In addition, the electrode including lithium metal or lithium metal alloy has high reactivity with the electrolyte and may cause a side reaction with the electrolyte, thereby reducing the cycle life of the battery. In order to compensate for this, a protective film capable of supplementing the surface of the lithium metal electrode containing lithium metal or lithium metal alloy is required.

Accordingly, the present inventors provide a novel protective film that can compensate for the above-described problems, and the protective film includes a lithium salt or a liquid electrolyte.

When the protective film includes a liquid electrolyte, an ion conductive path can be formed through the liquid electrolyte, thereby improving the conductivity of the negative electrode. And it is possible to manufacture a lithium metal battery having stable cycle characteristics.

The liquid electrolyte includes at least one selected from an organic solvent, an ionic liquid, and a lithium salt.

The liquid electrolyte may occupy 30 to 60% by volume, for example, 35 to 55% by volume, for example, 40 to 50% by volume, based on the total volume of the protective film in the protective film. The liquid electrolyte occupies, for example, 40 to 50% by volume in the protective film.

When the protective film includes a liquid electrolyte, a liquid electrolyte may be added in the protective film manufacturing step or the liquid electrolyte contained in the battery may move to the protective film and be contained in the protective film after operation of the battery.

In the protective film according to an embodiment, the size of one or more particles selected from organic particles, inorganic particles, and organic/inorganic particles is, for example, 1.1 to 50 μm, for example, 1.1 to 25 μm, for example, 1.5 to 20 μm. , for example 1.5 to 10 μm.

The particles include, for example, poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm and poly(styrene-co-divinylbenzene) having an average particle diameter of about 8 μm in a 1:1 weight ratio. Poly(styrene-co-divinylbenzene) copolymer microspheres containing copolymer microspheres or having an average particle diameter of about 3 μm in a 1:1 weight ratio and poly(styrene-co-divinylbenzene) having an average particle diameter of about 1.3 μm ) copolymer microspheres or poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm and poly(styrene-co-divinylbenzene) having an average particle diameter of about 1.1 μm in a 1:1 weight ratio ) copolymer microspheres.

According to one embodiment, the particles are microspheres having a monomodal particle size distribution. When the monomodal particle size distribution is analyzed using a particle diameter analyzer (Dynamic Light Scattering: DLS, Nicomp 380), the standard deviation is less than 40%, for example, 20% or less, for example, 10% or less. , for example, 1% or more to less than 40% or 2 to 25%, for example, within the range of 3 to 10%.

A Young's modulus of the passivation layer is 10 ⁶ Pa or more, for example, 10 ⁷ Pa or more or 10 ⁸ Pa or more. The Young's modulus of the protective film is, for example, 10 ⁶ to As 10 ¹¹ Pa, 10 ⁷ to 10 ¹⁰ Pa, or 10 ⁷ to 10 ⁹ Pa, the Young's modulus of the protective film is very excellent and mechanical properties are very good.

The Young's modulus has the same meaning as the so-called "tensile modulus". The tensile modulus is measured using a dynamic mechanical analysis system (DMA800, TA Instruments), and the protective film specimen is prepared through ASTM standard D412 (Type V specimens). And the tensile modulus of elasticity of the protective film was measured by measuring the change in strain with respect to stress at a rate of 5 mm per minute at 25 ^o C and a relative humidity of about 30%. The tensile modulus of elasticity is evaluated from the slope of the stress-strain curve thus obtained. The protective film may contain particles having a chemically or physically crosslinked structure.

At least one particle in the protective layer may have a cross-linked structure. Particles having a chemically or physically crosslinked structure are defined as including organic particles made of a crosslinked polymer obtained from a polymer having a crosslinkable functional group, inorganic particles having a structure crosslinked by a crosslinkable functional group present on the surface, and the like. . The crosslinkable functional group is a functional group that participates in the crosslinking reaction, and may include, for example, an acryl group, a methacryl group, a vinyl group, and the like.

Crosslinking may be performed by applying heat or irradiating light such as UV. Here, heat or light may be applied in a range that does not negatively affect the lithium metal electrode.

Particles having a chemically crosslinked structure are crosslinked using a chemical method (ie, chemical reagents) to enable binding of a crosslinkable functional group present in a material constituting the particle. And particles having a physically crosslinked structure are crosslinked by a physical method. Physical methods include, for example, applying heat to enable bonding of the cross-linkable functional group, that is, to reach the glass transition temperature of the polymer constituting the particle although the cross-link is not formed by a chemical reagent. Cross-linking may take place within the particle itself or may proceed between adjacent particles in the protective film.

The lithium metal or lithium metal alloy used as the lithium metal electrode has a thickness of 100 µm or less, for example, 80 µm or less, or 50 µm or less, or 30 µm or less, or 20 µm or less. According to another embodiment, the thickness of the lithium metal electrode is 0.1 to 60㎛. Specifically, the thickness of the lithium metal or lithium metal alloy is 1 to 25 μm, for example, 5 to 20 μm, specifically 10 to 20 μm.

The particles may have a spherical shape, a rod shape, an elliptical shape, a radial shape, or the like, or a combination thereof.

When the particles are spherical, for example, they may be microspheres having an average particle diameter of more than 1 μm and a size of 100 μm or less. The average particle diameter of the microspheres may be, for example, 1.5 to 75 μm, 1.5 to 50 μm, or 1.5 to 20 μm, or, for example, 1.5 to 10 μm.

If the size of the particles exceeds 100㎛, the thickness of the protective film is thickened to increase the overall thickness of the cell may deteriorate the energy density characteristics of the lithium metal battery. In addition, since the porosity of the protective layer is increased, the liquid electrolyte may easily contact the lithium metal electrode.

When the particle size is 1 μm or less, a lithium metal battery employing a protective film containing particles of this size has lithium electrodeposition density characteristics of a lithium metal battery employing a protective film when the particle size exceeds 1 μm and is less than or equal to 100 μm. lower than in the case of

In the present specification, "size" refers to an average particle diameter when the particles are spherical. When the particles are rod-shaped or elliptical, the size represents the major axis length.

As used herein, “average particle size” or “average particle diameter” refers to 50% of particles in a distribution curve accumulating particles with the smallest particle size and largest particle size in order. It means the particle size (D50) corresponding to . Here, the total number of accumulated particles is 100%. The average particle size is measurable according to methods known to those skilled in the art. For example, the average particle size can be measured using a particle size analyzer, TEM or SEM image. As another method for measuring the average particle size, there is a method using a measuring device using dynamic light scattering. According to this method, the number of particles having a predetermined size range is counted, and the average particle diameter can be calculated therefrom.

In the present specification, porosity is a measure of voids (ie, voids or pores) in a material, and is defined as a volume percentage of voids in a material based on the total volume of the material.

11 is for explaining the protective role of the lithium metal electrode when the particle diameter of the microspheres contained in the protective film exceeds about 1 μm and is less than or equal to 100 μm in the negative electrode for a lithium metal battery according to an embodiment, and FIG. 1 m is a general This is to explain the protective role of the lithium metal electrode when the average particle diameter of the microspheres contained in the protective film in the anode for lithium metal batteries is 1 μm or less.

Referring to FIG. 11 , a protective film 12 including microspheres 13a is laminated on the lithium metal electrode 11 . The surface coating fraction of microspheres and the particle spacing of microspheres contained in the protective film formed on the lithium metal electrode are factors that directly affect the protective film function of the lithium metal electrode. As used herein, the term “surface coating fraction” refers to a surface area (portion) of a lithium metal electrode including a protective film for the total surface area of the lithium metal electrode. The surface coating fraction is, for example, about 80%, about 85%, about 90%, or about 100% of the total surface area of the lithium metal electrode.

The lithium metal electrode 11 is, for example, lithium metal, and as shown in FIG. 11 , the lithium metal electrode 11 has a thickness of, for example, 5 to 50 µm, for example 10 to 30 µm, for example 15 to 25 µm. It has a thin and soft characteristic with a thickness of ㎛, and the surface step is about ±1㎛. When protecting a lithium metal electrode having such a surface step, when the average particle diameter exceeds 1 μm and is 100 μm or less, using the microspheres 13a has a very excellent function of protecting the lithium metal electrode.

In contrast, when the protective film 12 laminated on the lithium metal electrode 11 as shown in FIG. 1m contains microspheres having an average particle diameter of 1 μm or less, for example, microspheres having a particle diameter of 5 nm to 300 nm. In this case, the aggregation of microspheres and the surface coating fraction are reduced. As a result, the porosity in the protective film may be increased, so that it may be advantageous for the liquid electrolyte to contact the lithium metal.

When the particles are of the spherical type, the size indicates the average particle diameter, and when the particles are of the rod type, the size indicates the length of the major axis. If the particles are of the rod-shaped type, the ratio of the horizontal and vertical axes may be, for example, 1:1 to 1:30, for example 1:2 to 1:25, for example 1:5 to 1:20. .

Any of the particles of the protective film may be used as long as it is a polymer used for forming the protective film.

According to another exemplary embodiment, the particles of the protective film may be formed of a polymer having low wettability with respect to the liquid electrolyte.

The particles of the protective film may include at least one selected from i) polystyrene, a copolymer containing a styrene repeating unit, a copolymer containing a repeating unit having a crosslinkable functional group, and ii) a crosslinked polymer. The particles of the protective film may be a polymer (homopolymer or copolymer) containing a styrene-based repeating unit. As such, in the case of a polymer having a styrenic repeating unit, it has hydrophobicity and thus does not adversely affect the lithium metal electrode, and has almost no electrolyte wettability, so that the reactivity between the lithium metal electrode and the electrolyte can be minimized.

At least one of the particles is a polystyrene, poly(styrene-divinylbenzene) copolymer, poly(methylmethacrylate-divinylbenzene) copolymer, poly(ethylmethacrylate-divinylbenzene) copolymer, poly(pentyl) Methacrylate-divinylbenzene) copolymer, poly(butylmethacrylate-divinylbenzene) copolymer, poly(propylmethacrylate-divinylbenzene) copolymer, poly(styrene-ethylene-butyleneethylene-butyl Lene-styrene) copolymer, poly(styrene-methylmethacrylate) copolymer, poly(styrene-acrylonitrile) copolymer, poly(styrene-vinylpyridine) copolymer, poly(acrylonitrile-butadiene-styrene) copolymer, poly(acrylonitrile-ethylene-propylene-styrene) copolymer, poly(methylmethacrylate-acrylonitrile-butadiene-styrene) copolymer, poly(methacrylate-butadiene-styrene) copolymer, poly At least one selected from the group consisting of (styrene-(C1-C9 alkyl) acrylate) copolymer and poly(acrylonitrile-styrene--(C1-C9 alkyl) acrylate) copolymer and at least one polymer A selected from cross-linked polymers can be one

The crosslinked polymer refers to, for example, a poly(styrene-divinylbenzene) copolymer, poly(methyl methacrylate-divinylbenzene), or a crosslinked product of the above-mentioned polymer A. Here, the polymer A has a crosslinkable functional group, and a crosslinked polymer is prepared through crosslinking thereof. say

When the above-mentioned copolymer contains a styrenic repeating unit, the content of the styrenic repeating unit is 65 to 99 parts by weight, 80 to 99 parts by weight, 90 to 99 parts by weight, for example, based on 100 parts by weight of the copolymer. For 96 to 99 parts by weight.

When the copolymer contains divinylbenzene, the content of divinylbenzene is 1 to 35 parts by weight, 1 to 20 parts by weight, 1 to 10 parts by weight, 1 to 4 parts by weight, for example, based on 100 parts by weight of the copolymer. For example, it is used in an amount of 3 to 7 parts by weight, specifically 5 parts by weight.

The aforementioned poly(methyl methacrylate-divinylbenzene) copolymer, poly(ethyl methacrylate-divinylbenzene) copolymer, poly(pentyl methacrylate-divinylbenzene) copolymer, poly(butyl methacrylate) -Divinylbenzene) copolymer, poly(propyl methacrylate-divinylbenzene) copolymer of methyl methacrylate, ethyl methacrylate, pentyl methacrylate, butyl methacrylate, or propyl methacrylate repeating unit The content is 65 to 99 parts by weight, 80 to 99 parts by weight, 90 to 99 parts by weight, for example 96 to 99 parts by weight, based on 100 parts by weight of the copolymer.

Poly(styrene-ethylene-butylene-styrene) copolymer, poly(styrene-methylmethacrylate) copolymer, poly(styrene-acrylonitrile) copolymer, poly(styrene-vinylpyridine) copolymer, poly(styrene-vinylpyridine) copolymer as described above (acrylonitrile-butadiene-styrene) copolymer, poly(acrylonitrile-ethylene-propylene-styrene) copolymer, poly(methylmethacrylate-acrylonitrile-butadiene-styrene) copolymer, poly(methacrylate) -Butadiene-styrene) copolymer, poly(styrene-(C1-C9 alkyl) acrylate) copolymer and poly(acrylonitrile-styrene-(C1-C9 alkyl) acrylate) copolymer content of styrenic repeating units The amount of silver is 65 to 99 parts by weight, 80 to 99 parts by weight, 90 to 99 parts by weight, for example 96 to 99 parts by weight, based on 100 parts by weight of the total weight of the copolymer. And in the case of a ternary or quaternary copolymer in the above-described copolymer, the content of the remaining repeating units excluding the styrenic repeating unit may be mixed in various ratios from the remainder after subtracting the content of the styrenic repeating unit from the copolymer. The above-mentioned copolymer includes all of a block copolymer, a random copolymer, an alternating copolymer, a graft copolymer, and the like. These copolymers have a weight average molecular weight of 10,000 to 200,000 Daltons.

The weight average molecular weight of the block containing the first repeating unit is 10,000 Daltons or more, for example, 10,000 to 500,000 Daltons, specifically 15,000 to 400,000 Daltons. According to another embodiment, the weight average molecular weight of the block containing the first repeating unit is 20,000 to 200,000 Daltons. The content of the block containing the first repeating unit is 20 to 50 parts by weight, for example, 20 to 40 parts by weight, for example, 22 to 30 parts by weight, based on 100 parts by weight of the total weight of the block copolymer. By using such a polymer block, a protective film having excellent mechanical properties such as strength can be obtained.

The weight average molecular weight of the block containing the second repeating unit is 10,000 Daltons or more, for example, 10,000 to 510,000 Daltons, specifically 15,000 to 400,000 Daltons. According to another embodiment, the weight average molecular weight of the block containing the second repeating unit is 20,000 to 200,000 Daltons. When a hard block having such a weight average molecular weight is used, a protective film excellent in ductility, elasticity and strength can be obtained.

The block copolymer is at least one selected from a diblock copolymer (A-B) and a triblock copolymer (A-B-A' or B-A-B').

The particles of the protective film are polyvinylpyridine, polyvinylcyclohexane, polyglycidylacrylate, poly(2,6-dimethyl-1,4-phenylene oxide), polyolefin, poly(tertbutyl vinyl ether), polycyclohexyl. At least one selected from the group consisting of vinyl ether, polyvinyl fluoride, poly(styrene-maleic anhydride) copolymer, polyglycidyl methacrylate, polyacrylonitrile and polymeric ionic liquids (PIL) may include

Particles of the protective film are poly(styrene-divinylbenzene) copolymer, poly(methyl methacrylate-divinylbenzene) copolymer, poly(ethyl methacrylate-divinylbenzene) copolymer, poly(pentyl methacrylate- divinylbenzene) copolymer, poly(butyl methacrylate-divinylbenzene) copolymer, poly(propyl methacrylate-divinylbenzene) copolymer, poly(methylacrylate-divinylbenzene) copolymer, poly( Ethylacrylate-divinylbenzene) copolymer, poly(pentylacrylate-divinylbenzene) copolymer, poly(butylacrylate-divinylbenzene) copolymer, poly(propylacrylate-divinylbenzene) copolymer, and poly(acrylonitrile-butadiene-styrene) copolymer.

When the particles of the protective film include the above-described cross-linked polymer, the particles are connected to each other through cross-linking, so that the protective film has very good mechanical strength. The crosslinked polymer of the protective film has a degree of crosslinking of 10 to 30%, for example, 12 to 28%, for example, 15 to 25%, based on the total volume of the crosslinked polymer.

1A to 1D, the structure of the negative electrode for a lithium metal battery according to an embodiment will be described. 1A to 1D , the particles of the protective film have a microsphere shape as a non-limiting example.

As shown in Figure 1a, the negative electrode has a lithium metal electrode 11 made of lithium metal or a lithium metal alloy is stacked on the current collector 10, and a protective film 12 is disposed on the lithium electrode 11, have. The protective film 12 contains particles 13 . An empty space exists between the particles 13 contained in the protective film, and ions can be transferred through this space. Therefore, by employing such a protective film, the ionic conductivity of the negative electrode can be improved. In addition, a lithium dendrite growth space may be provided through an empty space, for example, a pore structure to guide lithium dendrite growth.

The lithium metal alloy includes lithium metal and a metal/metalloid or an oxide thereof capable of alloying with lithium metal. Metals/metalloids capable of alloying with lithium metal or oxides thereof include Si, Sn, Al, Ge, Pb, Bi, Sb, and Si-Y alloys (where Y is an alkali metal, alkaline earth metal, group 13 to 16 element, transition a metal, a rare earth element or a combination element thereof, but not Si), a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element, or a combination element thereof, not Sn), MnOx (0 < x ≤ 2), and the like.

The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. For example, the oxide of the metal/metalloid alloyable with the lithium metal may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, SnO ₂ , SiO _x (0<x<2), or the like.

As shown in FIG. 1B, the ion conductive polymer 14 is present around the particles 13. Although not shown in the figure, a liquid electrolyte exists in the space between the particles.

The ion conductive polymer 14 is contained in the protective film 12 to improve the strength of the protective film 12 and to serve as a binder. The content of the ion conductive polymer is 10 parts by weight or less, for example, 5 parts by weight or less, for example, 2 parts by weight or less based on 100 parts by weight of the particles. According to another embodiment, the content of the ion conductive polymer is 1 to 10 parts by weight, for example, 1 to 5 parts by weight, specifically 1 to 2 parts by weight based on 100 parts by weight of the particles. When the content of the ion conductive polymer is within the above range, the mechanical strength of the protective film is excellent, and thus lithium dendrite growth can be effectively suppressed.

The ion conductive polymer may serve as a binder to help fix the particles on the lithium metal electrode in the protective film, and any material capable of improving the mechanical strength of the protective film may be used. As the ion conductive polymer, any polymer having ion conductive properties selected from among homopolymers, copolymers and crosslinked polymers commonly used in lithium metal batteries may be applied.

The copolymer may be a block copolymer, a random copolymer, a graft copolymer, an alternating copolymer, or a combination thereof.

The cross-linked polymer refers to any polymer having a bond in which one polymer chain is connected to another polymer chain, for example, a polymer in which a cross-linked polymer having a cross-linkable functional group is formed. The crosslinked polymer may be a crosslinked product obtained from a copolymer containing a repeating unit having a crosslinkable functional group.

The crosslinked polymer is a crosslinked product of a block copolymer having a polyethylene oxide block having an acrylate functional group and a polystyrene block; or C1-C9 alkyl (meth)acrylate ((C1-C9 alkyl) (meth)acrylate), C2-C9 alkenyl (meth)acrylate ((C2-C9 alkenyl) (meth)acrylate), C1-C12 glycol A cross-linked product of one compound selected from diacrylate (C1-C12 glycol) diacrylate), poly(C2-C6 alkylene glycol) diacrylate (poly(C2-C6 alkylene glycol) diacrylate), and polyol polyacrylate, etc. can be heard The C1-C9 alkyl (meth)acrylate is, for example, hexyl acrylate, 2-ethylhexyl acrylate or allyl methacrylate.

Examples of glycol diacrylate include 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate (1,6-hexanediol diacrylate), ethylene glycol diacrylate, and neopentyl glycol diacrylate. And polyalkylene glycol diacrylate is, for example, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate and polypropylene glycol diacrylate. There are acrylates.

The polyol polyacrylate is, for example, trimethylol propane triacrylate, pentaerythritol tetraacrylate, or pentaerythritol triacrylate.

The ion conductive polymer may be, for example, at least one selected from polystyrene and block copolymers including styrene-based repeating units. Ion conductive polymers are, for example, polystyrene, poly(styrene-divinylbenzene) block copolymers, poly(styrene-isoprene) block copolymers, poly(styrene-isoprene-styrene) block copolymers, poly(styrene-butadiene) blocks copolymer, poly(styrene-butadiene-styrene) block copolymer, poly(styrene-ethylene-butylene-styrene) block copolymer, poly(styrene-methylmethacrylate) block copolymer, poly(styrene-acrylonitrile) ) block copolymer, poly(styrene-vinylpyridine) block copolymer, poly(acrylonitrile-butadiene-styrene) copolymer, poly(acrylonitrile-ethylene-propylene-styrene) copolymer, poly(methyl methacrylate) -Acrylonitrile-butadiene-styrene) copolymer, poly(C1-C9 alkyl) methacrylate-butadiene-styrene) copolymer, poly(styrene-(C1-C9 alkyl) acrylate) copolymer and poly(acrylo) It may be at least one selected from the group consisting of nitrile-styrene-acrylate) copolymers.

Examples of the poly(C1-C9 alkyl) methacrylate-butadiene-styrene) copolymer include polymethacrylate-butadiene-styrene) copolymer, and poly(styrene--(C1-C9 alkyl) acrylate) Examples of the copolymer include poly(styrene-acrylate) copolymers.

The poly(styrene-divinylbenzene) copolymer is represented by the following formula (1).

[Formula 1]

In Formula 1, a and b are mole fractions, respectively, 0.01 to 0.99, and the sum of a and b is 1. In Formula 1, a is, for example, 0.95 to 0.99, for example, 0.96 to 0.99, specifically 0.98 to 0.99, and b is, for example, 0.01 to 0.05, for example, 0.01 to 0.04, and specifically 0.01 to 0.02. .

The poly(styrene-divinylbenzene) copolymer is represented by the following Chemical Formula 1a.

[Formula 1a]

The poly(styrene-divinylbenzene) copolymer is represented by the following Chemical Formula 1b.

[Formula 1b]

The poly(acrylonitrile-butadiene-styrene) copolymer may be represented by Formula 2 below.

[Formula 2]

In Formula 2, x, y, and z are mole fractions, and are 0.01 to 0.99 regardless of each other, and the sum of x, y, and z is 1.

In Formula 2, x is 0.1 to 0.35, y is 0.05 to 0.55, and z is 0.2 to 0.7. For example, x is 0.15-0.35, y is 0.05-0.3, and z is 0.4-0.6.

The degree of polymerization of the poly(styrene-divinylbenzene) copolymer represented by the formula (1) and the poly(acrylonitrile-butadiene-styrene) copolymer represented by the formula (2) is 2 to 5,000, for example, a number of 5 to 1,000 .

The poly(styrene-divinylbenzene) copolymer represented by Formula 1 and the poly(acrylonitrile-butadiene-styrene) copolymer represented by Formula 2 may be, for example, block copolymers.

In the protective film according to an embodiment, the particles 13 may form a single film structure as shown in FIGS. 1A and 1B .

The protective film according to another embodiment has a two-layer film structure in which particles 13 are stacked in two layers on the lithium electrode 11 as shown in FIG. 1C . The ion conductive polymer 14 is present around the particles 13 as in FIG. 1B .

As shown in FIG. 1D , the protective film according to another exemplary embodiment may have a multilayer structure in which particles 13a, 13b, and 13c having different sizes are mixed in the protective film 12 . As such, when the protective film 12 has a multilayer structure in which particles of different sizes (13a), (13b) and (13c) are mixed, the porosity is lowered or the packing density is improved to increase the dendrite growth space. or, through this, it is possible to minimize the lithium metal contact of the electrolyte. And it becomes possible to suppress dendrite growth by improving the thickness of a protective film.

The particles of the protective film may contain, for example, a poly(styrene-divinylbenzene) copolymer.

When the particles are made of a cross-linked polymer, the particles may have a structure in which they are chemically connected to each other. Having such a chemically connected structure can form a high-strength microsphere network structure.

The porosity of the protective layer is 25 to 50%, for example, 28 to 48%, for example, 30 to 45%. And the pore size and porosity of the protective film are determined according to the size of the particles.

There is substantially no aggregation of particles in the protective film according to an embodiment, so that it can be formed to a constant thickness. The thickness of the protective film is 1 to 10 μm, for example 2 to 9 μm, for example 3 to 8 μm. The thickness deviation of the protective film is 0.1 to 4 µm, for example, 0.1 to 3 µm, for example, 0.1 to 2 µm.

The protective film contains a lithium salt or a liquid electrolyte. The liquid electrolyte contains a lithium salt and an organic solvent. The lithium salt contained in the protective film is, for example, LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiN(SO ₂ C ₂ ) F ₅ ) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiSbF ₆ , LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , and LiB(C ₂ O ₄ ) ) may be at least one selected from ₂ .

The content of the lithium salt in the protective film is 10 to 70 parts by weight, for example, 15 to 60 parts by weight, for example, 20 to 50 parts by weight, based on 100 parts by weight of the particles. When the content of the lithium salt is within the above range, the ionic conductivity of the protective film is very good.

The organic solvent includes a carbonate-based compound, a glyme-based compound, and a dioxolane-based compound. The carbonate-based compound includes ethylene carbonate, propylene carbonate, dimethyl carbonate, fluoroethylene carbonate, diethyl carbonate, or ethylmethyl carbonate.

The glyme-based compound is poly(ethylene glycol) dimethyl ether (PEGDME, polyglyme), tetra(ethylene glycol) dimethyl ether (TEGDME, tetraglyme), tri(ethylene glycol) dimethyl ether (tri(ethylene glycol) dimethyl ether, triglyme), poly(ethylene glycol) dilaurate (PEGDL), poly(ethylene glycol) monoacrylate ; PEGMA) and poly(ethylene glycol) diacrylate (poly(ethylene glycol) diacrylate; PEGDA).

Examples of the dioxolane-based compound include 1,3-dioxolane, 4,5-diethyl-1,3-dioxolane, 4,5-dimethyl-1,3-dioxolane, 4-methyl-1 and at least one selected from the group consisting of ,3-dioxolane and 4-ethyl-1,3-dioxolane. The organic solvent is 2,2-dimethoxy-2-phenylacetophenone, dimethyl ether (DME), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, gamma butyrolactone, 1, 1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether), etc.

Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethylene glycol Dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinonitrile, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, and 1,1 ,2,2-tetrafluoroethyl at least one selected from 2,2,3,3-tetrafluoropropyl ether.

1e and 1f are diagrams for explaining the effect of the lithium negative electrode according to an embodiment.

As shown in FIG. 1E , the lithium negative electrode according to an embodiment has a structure in which SEI is formed on the lithium metal electrode 11 and a protective film 12 containing particles 13 is disposed thereon. The lithium metal electrode 11 and the SEI have soft properties due to their thickness and the like, and are pressed by the particles 13 . As a result, a groove is formed on the lithium electrode 11 and the SEI 15 .

Particles 13 in FIG. 1E use, for example, cross-linked polystyrene (PS) microspheres. Lithium dendrite growth can be suppressed by the force applied to the particles 13 , and lithium dendrites can be guided to form in the space between the particles 13 . When the negative electrode using such a protective film is charged, lithium electrodeposition proceeds, as shown in FIG. 1f , a lithium electrodeposition layer 16 is formed on the lithium electrode 11, and SEI 13 and particles 13 are formed thereon. The protective film 12 has a stacked structure.

When the above-mentioned protective film is employed, the lithium electrodeposition density is greatly improved. In addition, the protective film has a function of adsorbing by-products obtained from the positive electrode by controlling the dendrite growth while providing a dendrite growth space using a network structure and a pore structure. is improved

In a lithium metal battery employing an anode for a lithium metal battery according to an embodiment, the electrodeposition density of lithium electrodeposited on the surface of a lithium electrode subjected to charging is 0.2 to 0.3 g/cm ³ (g/cc), 0.209 to 0.29 g/cm ³ , for example 0.201 to 0.280 g/cm ³ .

When the lithium anode according to the embodiment is employed in the lithium metal battery according to the embodiment, the lithium electrodeposition density is a lithium metal battery without a protective film (ie, a lithium metal battery employing a bare lithium metal as an anode) is larger than the lithium deposition density of Compared to a lithium metal battery employing a lithium metal without a protective film, when a lithium negative electrode according to an embodiment is employed, the lithium electrodeposition density increase rate is 50% or more, for example 55% or more, for example 58% or more, for example 50 to 75%, for example 50 to 60%. The reason why the electrodeposition density is greatly improved in this way is because the lithium negative electrode employs a high-strength protective film. Here, the Young's modulus of the protective film is 10 ⁶ Pa or more at 25° C., for example, 6 to 8 GPa.

When the Young's modulus of the protective film is within the above range, the function of suppressing the volume change of the negative electrode is excellent, and the portion that is attacked by the dendrite formed on the surface of the lithium metal electrode is cracked and a short is less likely to be formed.

The protective film according to an embodiment has a tensile strength at 25 °C of 2.0

MPa or more, such as 5.0 MPa or more, such as 10 MPa or more. In addition, the interfacial resistance between the lithium metal electrode and the protective layer derived from the Nyquist plot obtained from the impedance measurement is reduced by more than 10% at 25° C. compared to the bare lithium metal. As described above, when the protective film according to the embodiment is used, the interfacial resistance is reduced compared to the case of the lithium metal electrode alone, and thus the interfacial properties are excellent. In addition, the negative electrode has an oxidation current or a reduction current of 0.05 mA/cm ² or less in a voltage range of 0.0V to 6.0V compared to lithium metal.

In addition, when the protective film according to an embodiment is used, there is substantially no swelling problem of the battery after repeated charging and discharging.

In the protective film according to an exemplary embodiment, the region in which the liquid electrolyte directly contacts the lithium metal electrode is 30 to 80% based on the region in which the protective film and the lithium metal are in direct contact.

9A to 9C show that microspheres are disposed on the surface of the lithium metal in the negative electrode for a lithium metal battery according to an embodiment.

With reference to this, a structure in which microspheres 13 having a diameter of 3 μm are disposed on the lithium metal electrode 11 is shown. According to FIGS. 9A to 9C , the microspheres 13 are disposed on the lithium metal electrode 11 .

The length of the lithium metal electrode 11 in FIGS. 9A to 9C is about 5.4 μm. and

9A, 9B and 9C, a is, for example, about 1.2 μm, 0.9 μm, and 0.5 μm, respectively. At this time, the region in which the liquid electrolyte of the protective film is in direct contact with the lithium metal electrode is about 33.3%, 50%, and 72.2 based on the region in which the protective film and the lithium metal are in direct contact, respectively, in the case of FIGS. 9A, 9B and 9C. %to be.

A method of manufacturing a negative electrode for a lithium metal battery according to an embodiment will be described as follows.

First, a composition for forming a protective film is prepared by mixing particles having a size exceeding 1 μm and less than 100 μm and a solvent.

By coating and drying the composition for forming a protective film on the upper part of the lithium metal electrode to form a protective film, a negative electrode for a lithium metal battery can be manufactured.

As the solvent, tetrahydrofuran, N-methylpyrrolidone, or the like may be used. The content of the solvent is 100 to 5000 parts by weight based on 100 parts by weight of the particles.

An ion conductive polymer may be further added to the composition for forming a protective film.

One or more selected from an ionic liquid, a polymer ionic liquid, and a lithium salt may be further added to the composition for forming a protective film.

Any of the above coating methods may be used as long as they are commonly available methods when forming a protective film. For example, methods such as spin coating, roll coating, curtain coating, extrusion, casting, screen printing, inkjet printing, and doctor blade coating may be used.

Drying is carried out at 20 to 25 °C. As the drying proceeds at a low temperature as described above, deformation of the lithium metal electrode does not occur. In addition, a protective film having a monodisperse monolayer structure can be formed by directly coating the composition for forming a protective film on a lithium metal electrode, so that film processability is greatly improved. In addition, the protective film has very good mechanical strength and improved ionic conductivity.

A rolling process may be performed after the drying process. The rolling process may be performed under the same process conditions as in a conventional battery manufacturing method. A rolling process is performed using the pressure of 1-1.5 kgf/cm, etc., for example.

The protective layer has an oxidation current or a reduction current of 0.05 mA/cm ² or less in a voltage range of 0.0V to 6.0V compared to lithium metal. The protective layer may be electrochemically stable in a voltage range of 0V to 6.0V, for example, a voltage range of 0V to 5.0V, specifically, 0V to 4.0V with respect to lithium. The protective film according to an embodiment can be applied to an electrochemical device operated at a high voltage by having a wide voltage window that is electrochemically stable.

The particles of the passivation layer may be organic particles. Organic particles include, for example, polystyrene or poly(styrene-divinyl benzene) copolymers.

The particles of the protective layer may be inorganic particles. The inorganic particles include, for example, SiO ₂ , TiO ₂ , ZnO, Al ₂ O ₃ , or BaTiO ₃ .

The particles of the protective layer may be organic/inorganic particles. The organic-inorganic particles are, for example, at least one selected from cage-structured silsesquioxane and metal-organic framework (MOF).

The cage structure silsesquioxane may be, for example, polyhedral oligomeric silsesquioxane (POSS). There are 8 or less silicon present in this POSS, eg 6 to 8, eg 6 or 8 silicon. The silsesquioxane having a cage structure may be a compound represented by Formula 3 below.

[Formula 3]

Si _k O _1.5k (R ₁ ) _a (R ₂ ) _b (R _{3 ) c}

in Formula 3 R ₁ , R ₂ , and R ₃ are independently of each other hydrogen, substituted or non

A substituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or Unsubstituted C6-C30 aryl group, substituted or unsubstituted C6-C30 aryloxy group, substituted or unsubstituted C2-C30 heteroaryl group, substituted or unsubstituted C4-C30 carbocyclic ring group, or a silicon-containing functional group.

In Formula 3, 0<a<20, 0<b<20, 0<c<20, and k=a+b+c, a, b, and c are selected so that the range of k is 6≤k≤20 .

The silsesquioxane having the cage structure may be a compound represented by the following Chemical Formula 4 or a compound represented by the following Chemical Formula 5.

[Formula 4]

In Formula 4, R _{1 -} R ₈ are each independently hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, or a substituted or unsubstituted C2-C30 of an alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, a substituted or unsubstituted It may be a C2-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbocyclic group, or a silicon-containing functional group.

[Formula 5]

In Formula 5, R ₁ -R ₆ are each independently hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, or a substituted or unsubstituted C2-C30 of an alkenyl group, a substituted or unsubstituted C2-C30 alkynyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C6-C30 aryloxy group, a substituted or unsubstituted It may be a C2-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbocyclic group, or a silicon-containing functional group.

According to one embodiment, in the silsesquioxane of the cage structure, R _{1 -} R ₈ of Formula 4 and R _{1 -} R ₆ of Formula 5 are isobutyl groups. The caged silsesquioxane may be, for example, octaisobutyl-t8-silsesquioxane.

The metal-organic framework structure is a porous crystalline compound in which a metal ion of Groups 2 to 15 or a metal ion cluster of Groups 2 to 15 is chemically bonded to an organic ligand.

The organic ligand refers to an organic group capable of chemical bonding such as a coordination bond, an ionic bond, or a covalent bond. structures can be formed.

The Group 2 to Group 15 metal ions are cobalt (Co), nickel (Ni), molybdenum (Mo), tungsten (W), ruthenium (Ru), osdium (Os), cadmium (Cd), beryllium (Be), Calcium (Ca), Barium (Ba), Strondium (Sr), Iron (Fe), Manganese (Mn), Chromium (Cr), Vanadium (V), Aluminum (Al), Titanium (Ti), Zirconium (Zr) ), copper (Cu), zinc (Zn), magnesium (Mg), hafnium (Hf), Nb, tantalum (Ta), Re, rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt) , silver (Ag), scandium (Sc), yttrium (Y), indium (In), thallium (Tl), silicon (Si), Ge, tin (Sn), lead (Pb), arsenic (As), antimony ( Sb), at least one selected from bismuth (Bi), and the organic ligand is aromatic dicarboxylic acid, aromatic tricarboxylic acid, imidazole-based compound, tetrazole-based compound, 1,2,3-triazole, 1,2, 4-triazole, pyrazole, aromatic sulfonic acid, aromatic phosphoric acid, aromatic sulfinic acid, aromatic phosphinic acid, bipyridine, amino group, imino group, amide group, methane It is a group derived from at least one selected from compounds having at least one functional group selected from a dithioic acid (-CS ₂ H) group, a methanedithioic acid anion (-CS ₂ ^- ) group, a pyridine group, and a pyrazine group.

Examples of the above-mentioned aromatic dicarboxylic acid or aromatic tricarboxylic acid include benzenedicarboxylic acid, benzenetricarboxylic acid, biphenyldicarboxylic acid, and triphenyldicarboxylic acid.

The above-described organic ligand may be a group derived from a compound represented by the following formula (6) specifically.

[Formula 6]

The metal-organic framework structure is, for example, Ti ₈ O ₈ (OH) ₄ [O ₂ CC ₆ H ₄ -CO ₂ ] _{6 ,} Cu (bpy)(H ₂ O) ₂ (BF ₄ ) ₂ (bpy){bpy = 4, 4'-bipyridine}, Zn ₄ O(O ₂ CC ₆ H ₄ -CO ₂ ) ₃ (Zn-terephthalic acid-MOF, Zn-MOF) or Al(OH){O ₂ CC ₆ H ₄ -CO ₂ } can be mentioned.

The protective film is i) BaTiO₃, Cage-structured silsesquioxane, Metal-Orgainc Framework (MOF), Li_{One +x+ y}Al_xTi_{2 - x}Si_yP_{3 - y}O₁₂ (0<x<2, 0≤y<3), Pb(Zr_pTi_1-p)O₃(0≤p≤1) (PZT), Pb_{One - x}La_xZr_{One - y}Ti_yO₃(PLZT)(O≤x<1, O≤y<1),Pb(Mg₃Nb_2/3)O₃-PbTiO₃(PMN-PT), HfO₂, SrTiO₃, SnO₂, CeO₂, Na₂O, MgO, NiO, CaO, BaO, ZnO, ZrO₂, Y₂O₃, Al₂O₃, TiO₂, SiO₂, SiC, lithium phosphate (Li₃PO₄), Li_xTi_y(PO₄)₃(lithium titanium phosphate, 0<x<2,0<y<3), Li_xAl_yTi_z(PO₄)₃(lithium aluminum titanium phosphate, 0<x<2, 0<y<1, 0<z<3), Li_{One +x+y}(Al_pGa_{One -p})_x(Ti_qGe_{One -q})_2-xSi_yP_3-yO₁₂(O≤x≤1, O≤y≤1), Li_xLa_yTiO₃(lithium titanium phosphate, 0<x<2, 0<y<3), LixGeyPzSw(lithium germanium thiophosphate, 0<x<4, 0<y<1, 0<z<1, 0<w<5), \ Li_xN_y(lithium nitride, 0<x<4, 0<y<2), Li_xSi_yS_z(SiS₂Glass based, 0<x<3,0<y<2, 0<z<4), Li_xP_yS_z(P₂S₅Glass based, 0≤x<3, 0<y<3, 0<z<7), Li₂O, LiF, LiOH, Li₂CO₃, LiAlO₂, Li₂O-Al₂O₃-SiO₂-P₂O₅-TiO₂-GeO₂, Li_{3 + x}La₃M₂O₁₂(M = Te, Nb, or Zr) (0≤x≤5) comprising one or more particles selected from the group; or ii) may be a crosslinked product of the particles. The crosslinked product of the particles has a structure in which the particles have crosslinkable functional groups and are crosslinked by these crosslinkable functional groups.

Any crosslinkable functional group may be used as long as it is a crosslinkable functional group, and examples thereof include an acrylate group, a methacrylate group, and an epoxy group.

When a crosslinkable functional group is present on the particle surface, the particles are covalently linked to each other, so that the mechanical strength of the protective film made of these particles can be further improved.

An ionic liquid has a melting point below room temperature and refers to a salt in a liquid state at room temperature or a molten salt at room temperature composed of only ions. The ionic liquid is i) ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, tria At least one cation selected from zolium-based and mixtures thereof, and ii) BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- , AlCl ₄ ^- , HSO ₄ ^- , ClO ₄ ^- , CH ₃ SO ₃ ^- , CF ₃ CO ₂ ^- , Cl ^- , Br ^- , I ^- , BF ₄ ^- , SO ₄ ^- , CF ₃ SO ₃ ^- , (FSO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ )(CF ₃ SO ₂ )N ⁻ , and (CF ₃ SO ₂ ) ₂ N ⁻ are selected from compounds including at least one anion.

The ionic liquid is for example N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidium bis(trifluoromethylsulfonyl)imide, at least one selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

The content of the ionic liquid is 5 to 40 parts by weight, for example, 7.5 to 30 parts by weight, for example, 10 to 20 parts by weight, based on 100 parts by weight of the particles of the protective film. When the content of the ionic liquid is within the above range, a protective film having excellent ionic conductivity and mechanical properties can be obtained.

When the protective film contains an ionic liquid and a lithium salt, the molar ratio (IL/Li) of the ionic liquid (IL)/lithium ion (Li) is 0.1 to 2.0, for example 0.2 to 1.8, specifically 0.4 to 1.5 days can The protective film having such a molar ratio has excellent lithium ion mobility and ion conductivity as well as excellent mechanical properties, thereby effectively inhibiting lithium dendrite growth on the surface of the anode.

As the polymer ionic liquid, one obtained by polymerizing the ionic liquid monomer may be used, or a compound obtained in the form of a polymer may be used. Such a polymer ionic liquid has high solubility in organic solvents and has the advantage that ionic conductivity can be further improved when added to a protective film.

In the case of obtaining a polymer ionic liquid by polymerizing the above-described ionic liquid monomer, the resultant polymerization reaction is washed and dried, and then prepared to have an appropriate anion capable of imparting solubility to an organic solvent through an anion substitution reaction. do.

The polymer ionic liquid according to one embodiment is i) ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phospho At least one cation selected from nium-based, sulfonium-based, triazolium-based and mixtures thereof, and ii) BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- , AlCl ₄ ^- , HSO ₄ ^- , ClO ₄ ^- , CH ₃ SO ₃ ^- , CF ₃ CO ₂ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , Cl ^- , Br ^- , I ^- , SO ₄ ^2- , CF ₃ SO ₃ ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ )(CF ₃ SO ₂ )N ^- , NO ₃ ^- , Al ₂ Cl ₇ ^- , (CF ₃ SO ₂ ) ₃ C ^- , (CF ₃ ) ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , SF ₅ CF ₂ SO ₃ ^- , SF ₅ CHFCF ₂ SO ₃ ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (O(CF ₃ ) ₂ C ₂ (CF ₃ ) ₂ O) ₂ PO ^- may contain a repeating unit comprising at least one anion selected from.

According to another embodiment, the polymer ionic liquid may be prepared by polymerizing the ionic liquid monomer. The ionic liquid monomer has ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, It may have at least one cation selected from pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolium-based, and mixtures thereof and the above-described anion.

Examples of the ionic liquid monomer include 1-vinyl-3-ethylimidazolium bromide, a compound represented by the following Chemical Formula 7 or 8.

[Formula 7]

[Formula 8]

Examples of the above-described polymeric ionic liquid include a compound represented by the following formula (9) or a compound represented by the formula (10).

[Formula 9]

In Formula 9, R ₁ and R ₃ are each independently hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, or a substituted or unsubstituted C2-C30 of an alkynyl group, a substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C2-C30 heteroaryl group, or a substituted or unsubstituted C4-C30 carbocyclic group. In Formula 9, R ₂ simply represents a chemical bond or represents a C1-C30 alkylene group, C6-C30 arylene group, C2-C30 heteroarylene group, or C4-C30 divalent carbocyclic group,

X ^- represents the anion of the ionic liquid,

n is from 500 to 2800.

[Formula 10]

In Formula 10, Y ⁻ is defined the same as X ⁻ in Formula 9, and n is 500 to 2800.

In Formula 10, Y ⁻ is, for example, bis(trifluoromethanesulfonyl)imide (TFSI), bis(fluorosulfonyl)imide, BF ₄ , or CF ₃ SO ₃ .

Polymeric ionic liquids are for example poly(1-vinyl-3-alkylimidazolium), poly(1-allyl-3-alkylimidazolium), poly(1-(methacryloyloxy-3-alkyl) imidazolium), and CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , ( CF ₃ SO ₂ ) ₃ C ⁻ , (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , C ₃ F ₇ COO ⁻ and (CF ₃ SO ₂ )(CF ₃ CO)N ⁻ among selected anions.

The compound represented by Formula 10 may include polydiallyldimethylammonium bis(trifluoromethanesulfonyl)imide.

According to another embodiment, the high molecular weight ionic liquid may include a low molecular weight polymer, a thermally stable ionic liquid, and a lithium salt. The low molecular weight polymer may have an ethylene oxide chain. The low molecular weight polymer may be a glyme. Here, glyme includes, for example, polyethylene glycol dimethyl ether (polyglyme), tetraethylene glycol dimethyl ether (tetraglyme), and triethylene glycol dimethyl ether (triglyme).

The weight average molecular weight of the low molecular weight polymer is 75 to 2000 Daltons, for example 100 to 1000 Daltons, for example 250 to 500 Daltons. And the thermally stable ionic liquid is as defined in the above-mentioned ionic liquid. The protective layer may further include an oligomer. The oligomer is at least one selected from the group consisting of polyethylene glycol dimethyl ether and polyethylene glycol diethyl ether. The weight average molecular weight of the oligomer is 200 to 2,000 Daltons, for example 300 to 1800 Daltons, for example 400 to 1500 Daltons, and the content of the oligomer is 5 to 50 parts by weight, for example, based on 100 parts by weight of the particles of the protective film. 10 to 40 parts by weight, for example 10 to 30 parts by weight. When the oligomer is added as described above, the film formability, mechanical properties, and ionic conductivity properties of the protective film are more excellent.

The ionic conductivity of the protective film is 1 X 10 ^-4 S/cm or more at about 25° C., for example,

It may be 5×10 ^-4 S/cm or more, specifically 1×10 ^-3 S/cm or more.

The lithium metal battery according to an embodiment refers to, for example, a lithium air battery, a lithium ion battery, a lithium polymer battery, and the like.

The protective film according to an embodiment is suitable as a protective film for a lithium secondary battery for high voltage.

Here, "high voltage" refers to a case in which the charging voltage is in the range of 4.0V to 5.5V.

According to another aspect, there is provided a lithium metal battery including a positive electrode, a negative electrode for a lithium metal battery according to an embodiment, and an electrolyte interposed therebetween.

The electrolyte may be a mixed electrolyte type including at least one selected from a liquid electrolyte, a solid electrolyte, a gel electrolyte, a polymer ionic liquid, and a solid electrolyte. The lithium metal battery may further include a separator.

At least one selected from a liquid electrolyte, a polymer ionic liquid, a gel electrolyte, and a solid electrolyte may be interposed between the positive electrode and the electrolyte. The gel electrolyte is an electrolyte having a gel form, and any one known in the art may be used. The gel electrolyte may contain, for example, a polymer and a polymer ionic liquid. The polymer herein may be, for example, a solid graft (block) copolymer electrolyte.

The solid electrolyte may be an organic solid electrolyte or an inorganic solid electrolyte.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly-agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and ionic dissociation groups. Polymers and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ - Li ₂ S-SiS ₂ , Cu ₃ N, LiPON, Li ₂ S·GeS ₂ ·Ga ₂ S ₃ , Li ₂ O·11Al ₂ O ₃ , (Na,Li) _{1+ x} Ti _{2 - x} Al _x (PO ₄ ) ₃ (0.1≤x≤0.9), Li _{1 + x} Hf _{2 - x} Al _x (PO ₄ ) ₃ (0.1≤x≤0.9), Na ₃ Zr ₂ Si ₂ PO ₁₂ , Li ₃ Zr ₂ Si ₂ PO ₁₂ , Na ₅ ZrP ₃ O ₁₂ , Na ₅ TiP ₃ O ₁₂ , Na ₃ Fe ₂ P ₃ O ₁₂ , Na ₄ NbP ₃ O ₁₂ , Na-Silicates, Li _{0 . 3} La _{0 . 5} TiO ₃ , Na ₅ MSi ₄ O ₁₂ (M is a rare earth element such as Nd, Gd, Dy) Li ₅ ZrP ₃ O ₁₂ , Li ₅ TiP ₃ O ₁₂ , Li ₃ Fe ₂ P ₃ O ₁₂ , Li ₄ NbP ₃ O ₁₂ , Li _{1 + x} (M, Al,Ga) _x (Ge _1-y Ti _y ) _{2 -x} (PO ₄ ) ₃ (x≤0.8, 0≤y≤1.0, M is Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), Li _{1 +x+ y} Q _x Ti _{2 - x} Si _y P _{3 - y} O ₁₂ (0<x≤0.4, 0<y≤0.6, Q is Al or Ga), Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ La ₃ M ₂ O ₁₂ (M is Nb, Ta), Li _{7 + x} A _x La _{3 - x} Zr ₂ O ₁₂ (0<x<3, A is Zn) and the like may be used.

The protective layer according to an embodiment may include at least one selected from an ionic liquid, a metal salt containing a Group 1 or 2 element, and a nitrogen-containing additive, boron nitride, or a mixture thereof.

The metal salt containing the Group 1 element or Group 2 element is at least one metal salt containing at least one selected from Cs, Rb, K, Ba, Sr, Ca, Na, and Mg, and the nitrogen-containing additive is an inorganic nitrate. (inorganic nitrate), organic nitrate (organic nitrate), inorganic nitrite (inorganic nitrite), organic nitrite (organic nitrite), organic nitro compound, organic nitroso compound, NO compound and lithium nitride (Li ₃ N) consisting of at least one selected from the group.

At least one selected from the group 1 or 2 element-containing metal salt and nitrogen-containing additive is insoluble in the organic solvent of the liquid electrolyte. Due to such solubility characteristics, the lithium ion between the electrodes is limited to the surface of the lithium metal anode and stably present, and the mobility of at least one selected from the group 1 or 2 element-containing metal salt and nitrogen-containing additive is limited. does not impede the movement of

In addition, since the metal of the metal salt containing the Group 1 or Group 2 element has a larger atomic size than lithium, when it is contained in a protective film, lithium dendrite on the surface of the lithium metal negative electrode due to the steric hindrance effect of the metal can inhibit growth. In addition, the metal cation (eg, Cs or rubidium ion) of the metal salt has an effective reduction potential that is small compared to the reduction potential of lithium ions, so that the metal salt is reduced or applied during the lithium deposition process. Without the process, the metal cations form an electrostatic shield of positive charge around the initial growth tip of the protuberance on the surface of the lithium metal anode. When the electrostatic shield of such positive charge is formed, it is possible to effectively suppress the growth of lithium dendrites on the surface of the lithium metal anode. As described above, in order for the metal salt to have a small effective reduction potential compared to the reduction potential of lithium, the content of the metal salt is important. The content of the metal salt is controlled in the range of 0.1 to 100 parts by weight, for example, 1 to 75 parts by weight, for example, 10 to 50 parts by weight, based on 100 parts by weight of the particles of the protective film.

In addition, the protective film is very excellent in mechanical strength and flexibility to suppress the formation of lithium dendrites, and forms an ion conductive film having high ion conductivity between the lithium metal negative electrode and the protective film. The ion conductive film reduces the interfacial resistance between the lithium metal negative electrode and the protective film by increasing the ion conductivity and lithium ion mobility of the protective film. The ion conductive film contains, for example, lithium nitride (Li ₃ N).

In addition, the protective film improves the electrodeposition morphology of the lithium metal negative electrode by chemically improving the electrodeposition/desorption process of lithium to improve the electrodeposition morphology of the lithium metal negative electrode as compared to the case where the conventional protective film is formed. improve mobility. And as described above, at least one selected from the metal salt and the nitrogen-containing additive is present in the protective film on the surface of the lithium metal negative electrode to be limited, so that at least one selected from the metal salt and the nitrogen-containing additive is dispersed in the liquid electrolyte or approached toward the positive electrode to interact with the positive electrode It can block the reaction from taking place. As a result, it is possible to manufacture a lithium metal battery with improved rate performance and lifespan.

Nitrogen-containing additives contained in the protective film include, but are not limited to, inorganic nitrate, organic nitrate, inorganic nitrite, organic nitrite, organic nitrite, organic nitro compound, organic and at least one selected from the group consisting of an organic nitrso compound, an NO compound, and lithium nitride (Li ₃ N).

The inorganic nitrate is, for example, at least one selected from the group consisting of lithium nitrate, potassium nitrate, cesium nitrate, barium nitrate and ammonium nitrate, and the organic nitrate is, for example, dialkyl imidazolium nitrate. at least one selected from the group consisting of lactate, guanidine nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, and octyl nitrite. And the organic nitrite is, for example, at least one selected from the group consisting of ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, and octyl nitrite.

The organic nitro compound may include, for example, at least one selected from the group consisting of nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene and nitropyridine. And the N-O compound is, for example, at least one selected from the group consisting of pyridine N-oxide, alkylpyridine N-oxide, and tetramethyl piperidine N-oxyl (TEMPO).

In the protective film according to another embodiment, the nitrogen-containing additive is at least one selected from LiNO ₃ and Li ₃ N, and the metal salt containing the Group 1 or Group 2 element is cesium bistrifluoromethylsulfonylimide (CsTFSI), CsNO ₃ , CsPF ₆ , CsFSI, CsAsF ₆ , CsClO ₄ , or CsBF ₄ , for example, CsTFSI.

In the protective layer, the content of at least one selected from a metal salt containing a Group 1 or 2 element and a nitrogen-containing additive is 0.1 to 100 parts by weight, for example, 0.1 to 30 parts by weight, based on 100 parts by weight of the polymer. When the content of at least one selected from a metal salt containing a Group 1 or 2 element and a nitrogen-containing additive is within the above range, the effect of inhibiting the growth of lithium dendrites, the interfacial resistance between the surface of the lithium metal negative electrode and the protective film is reduced, and the ion mobility of lithium It is possible to manufacture an improved lithium metal battery.

According to one embodiment, the protective layer may include only a metal salt containing a Group 1 or Group 2 element. At this time, the content of the metal salt containing a Group 1 or 2 element is 0.1 to 100 parts by weight, for example 0.1 to 50 parts by weight, for example 0.1 to 30 parts by weight, based on 100 parts by weight of the particles,

According to another exemplary embodiment, the protective layer may contain only a nitrogen-containing additive. At this time, the content of the nitrogen-containing additive is 0.1 to 100 parts by weight, for example, 0.1 to 50 parts by weight, for example, 0.1 to 30 parts by weight, based on 100 parts by weight of the particles.

The protective film may contain, for example, both a metal salt containing a Group 1 or Group 2 element and a nitrogen-containing additive. At this time, the content of the metal salt containing the Group 1 or Group 2 element is 0.01 to 99.99 parts by weight, for example, 0.05 to 50 parts by weight, for example, 0.1 to 30 parts by weight, based on 100 parts by weight of the particles, and the nitrogen-containing additive The content of is 0.01 to 99.99 parts by weight, for example, 0.05 to 50 parts by weight, for example, 0.1 to 30 parts by weight, based on 100 parts by weight of the particles.

In the protective film according to an embodiment, a mixing weight ratio of the metal salt containing a Group 1 or 2 element and the nitrogen-containing additive is 1:9 to 9:1, for example 1:2 to 2:1, specifically 1:1. . When the mixing weight ratio of the metal salt containing a Group 1 or 2 element and the nitrogen-containing additive is within the above range, the electrodeposition density on the surface of the lithium metal anode and the mobility of lithium ions in the electrolyte are excellent, so the rate-limiting performance and lifespan characteristics of the lithium metal battery This is improved.

The lithium metal electrode may be a lithium metal or a lithium metal alloy, and a liquid electrolyte containing at least one selected from an organic solvent, an ionic liquid, and a lithium salt may be further included between the negative electrode and the positive electrode.

In the lithium metal battery, if the negative electrode according to an embodiment is employed, a lithium metal battery having improved capacity retention rate can be manufactured. Such lithium metal batteries have high voltage, capacity, and energy density, and thus are widely used in the fields of mobile phones, notebook computers, storage batteries of power generation facilities such as wind power or solar power, electric vehicles, uninterruptible power supply devices, and household storage batteries.

1G to 1J schematically show the structure of a lithium metal battery according to an embodiment.

As shown in FIG. 1G , the lithium metal battery has a structure in which the electrolyte 24 is interposed between the positive electrode 21 and the negative electrode 22 . A protective film 23 is included between the electrolyte 24 and the negative electrode 22 . The electrolyte 24 may further include one or more selected from a liquid electrolyte, a polymer ionic liquid, a solid electrolyte, and a gel electrolyte. The lithium metal battery may further include a separator.

As the above-described protective film 23 is disposed on at least a portion of the negative electrode 22 , the surface of the negative electrode may be mechanically stabilized and electrochemically stabilized. Therefore, it is possible to suppress the formation of dendrites on the surface of the negative electrode during charging and discharging of the lithium metal battery, and the interfacial stability between the negative electrode and the electrolyte is improved. Therefore, the cycle characteristics of the lithium metal battery can be improved.

The electrolyte 24 may have a two-layer structure in which a liquid electrolyte 24a and a solid electrolyte 24b are sequentially stacked as shown in FIG. 1H . Here, the liquid electrolyte may be disposed adjacent to the protective film 23 . This lithium metal battery has a stacking order of negative electrode / protective film / electrolyte (liquid electrolyte / solid electrolyte) / positive electrode.

Referring to FIG. 1I , a lithium metal battery according to an exemplary embodiment may use a separator 24c. As the separator, a single-layer film made of polyethylene, polypropylene, polyvinylidene fluoride or a combination thereof or a multi-layer film of two or more layers thereof may be used, a polyethylene/polypropylene two-layer separator, and a polyethylene/polypropylene/polyethylene three-layer separator , a polypropylene/polyethylene/polypropylene three-layer separator and the like can be used. An electrolyte containing a lithium salt and an organic solvent may be further added to the separator.

As shown in FIG. 1J , a liquid electrolyte 24a may be disposed in a lithium metal battery according to an exemplary embodiment. Here, the liquid electrolyte may be the same as or different from the composition of the liquid electrolyte that may be contained in the protective film 23 .

1K is a schematic diagram of a structure of a lithium metal battery according to another embodiment.

The lithium metal battery 30 includes a positive electrode 31, a negative electrode 32 according to an embodiment, and a battery case 34 for accommodating them.

1G to 1K , the positive electrode may be a porous positive electrode. The porous positive electrode includes a positive electrode that contains pores or does not intentionally exclude the formation of the positive electrode, so that the liquid electrolyte can penetrate into the positive electrode by capillary action or the like.

For example, the porous positive electrode includes a positive electrode obtained by coating and drying a positive electrode active material composition including a positive electrode active material, a conductive agent, a binder, and a solvent. The positive electrode thus obtained may contain pores existing between particles of the positive electrode active material. The porous positive electrode may be impregnated with a liquid electrolyte.

According to another embodiment, the positive electrode may include a liquid electrolyte, a gel electrolyte, or a solid electrolyte. The liquid electrolyte, the gel electrolyte, and the solid electrolyte may be used as electrolytes for lithium metal batteries in the art, as long as they do not deteriorate the positive electrode active material by reacting with the positive electrode active material during charging and discharging.

Each of the components constituting the lithium metal battery including the negative electrode according to the embodiment and the method of manufacturing the lithium metal battery having these components will be described in more detail as follows.

As a positive electrode active material for manufacturing a positive electrode, it may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide, but is not necessarily limited thereto. and any positive active material available in the art may be used.

For example, Li _a A _{1 -b B b D 2} (in the above formula, 0.90≤a≤1.8, and 0≤b≤0.5); Li _a E _1-b B _b O _2-c D _c (in the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE _{2 -b B b O 4 -c} D _c (wherein 0≤b≤0.5, 0≤c≤0.05); Li _a Ni _{1 -b- c} Co _b B _c D _α (in the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li _a Ni _{1 -b- c} Co _b B _c O _{2 -α F α ( in} the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _{1 -b- c} Mn _b B _c D _α (in the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li _a Ni _{1 -b- c} Mn _b B _c O _{2 -α F α ( in} the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (in the above formula, 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≤f≤2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≤f≤2); A compound represented by any one of the chemical formulas of LiFePO ₄ may be used.

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

As the positive active material, for example, a compound represented by the following Chemical Formula 11, a compound represented by the following Chemical Formula 12, or a compound represented by the Chemical Formula 13 may be used.

[Formula 11]

Li _a Ni _b Co _c Mn _d O ₂

In Formula 11, 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and 0≤d≤0.5.

[Formula 12]

Li ₂ MnO ₃

[Formula 13]

LiMO ₂

In Formula 13, M is Mn, Fe, Co, or Ni.

A positive electrode is prepared according to the following method.

A cathode active material composition in which a cathode active material, a binder, and a solvent are mixed is prepared.

A conductive agent may be further added to the cathode active material composition.

The positive electrode active material composition is directly coated and dried on a metal current collector to manufacture a positive electrode plate. Alternatively, the positive electrode active material composition may be cast on a separate support, and then a film peeled from the support may be laminated on a metal current collector to manufacture a positive electrode plate.

The binder is a component that assists in bonding of the active material and the conductive agent and the like to the current collector. Non-limiting examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoro roethylene, polyethylene, polypropylene, ethylene-propylene-diene ter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, and the like. The content is 1 to 50 parts by weight, for example, 2 to 5 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material. When the content of the binder is within the above range, the binding force of the active material layer to the current collector is good.

The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The amount of the conductive agent is 1 to 10 parts by weight, for example, 2 to 5 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material. When the content of the conductive agent is within the above range, the conductivity characteristics of the finally obtained electrode are excellent.

As a non-limiting example of the solvent, N-methylpyrrolidone and the like are used.

The amount of the solvent is 100 to 2000 parts by weight based on 100 parts by weight of the positive electrode active material. When the content of the solvent is within the above range, the operation for forming the active material layer is easy.

The content of the positive active material, the conductive agent, the binder, and the solvent is a level commonly used in a lithium battery. At least one of the conductive agent, the binder, and the solvent may be omitted depending on the use and configuration of the lithium metal battery.

The negative electrode may be a lithium metal thin film or a lithium metal alloy thin film as described above.

The lithium metal alloy may include lithium and a metal/metalloid capable of alloying with lithium. For example, the metal/metalloid capable of alloying with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb, or a Si-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 to 16 element, a transition metal) , a rare earth element or a combination element thereof, not Si), a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 to 16 element, a transition metal, a rare earth element, or a combination element thereof, Sn is not), etc. The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

As the electrolyte, a separator and/or a lithium salt-containing non-aqueous electrolyte commonly used in lithium metal batteries may be used.

As the separator, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 20 μm. As such a separator, For example, olefin polymers, such as polypropylene; A sheet or nonwoven fabric made of glass fiber or polyethylene is used. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also serve as a separator.

Specific examples of the separator include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, a polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, polypropylene/polyethylene and mixed multilayer films such as a polypropylene three-layer separator and the like.

The lithium salt-containing non-aqueous electrolyte includes a non-aqueous electrolyte and a lithium salt.

As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, or an inorganic solid electrolyte is used.

The non-aqueous electrolyte includes an organic solvent. Any such organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , Fluoroethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, 4-methyldioxolane, N,N-dimethylform amide, N,N-dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof. And examples of the lithium salt include, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, Li(FSO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _{2x + 1} SO 2 )(C _y F _{2y + 1} SO ₂ ) (provided that x and y are natural numbers), LiCl, LiI, or mixtures thereof. And for the purpose of improving charge/discharge characteristics, flame retardancy, etc. in the non-aqueous electrolyte, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoamide (hexamethyl phosphoramide), nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride etc. may be added. In some cases, in order to impart incombustibility, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included.

The lithium metal battery according to one embodiment has excellent capacity and lifespan characteristics, so it can be used in a battery cell used as a power source for a small device, as well as a medium or large battery pack including a plurality of battery cells used as a power source for a medium or large device. It can also be used as a unit cell in a battery module.

Examples of the medium-large device include electric vehicles (Electric Vehicles, EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (Plug-in Hybrid Electric Vehicles, PHEVs), etc. E-bike) and an electric two-wheeled vehicle power tool power storage device including an electric scooter (E-scooter), but is not limited thereto.

Alkyl as used herein refers to fully saturated branched or unbranched (or straight or linear) hydrocarbons.

Non-limiting examples of “alkyl” include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, and the like.

At least one hydrogen atom in “alkyl” is a halogen atom, a C1-C20 alkyl group substituted with a halogen atom (eg, CF ₃ , CHF ₂ , CH ₂ F, CCl ₃ , etc.), C1-C20 alkoxy, C2-C20 alkoxy Alkyl, hydroxyl group, nitro group, cyano group, amino group, amidino group, hydrazine group, hydrazone group, carboxyl group or its salt, sulfonyl group, sulfamoyl group, sulfonic acid group or its salt, phosphoric acid or its salt, or C1- C20 alkyl group, C2-C20 alkenyl group, C2-C20 alkynyl group, C1-C20 heteroalkyl group, C6-C20 aryl group, C7-C20 arylalkyl group, C6-C20 heteroaryl group, C7-C20 hetero It may be substituted with an arylalkyl group, a C6-C20 heteroaryloxy group, a C6-C20 heteroaryloxyalkyl group, or a C6-C20 heteroarylalkyl group.

The term “halogen atom” includes fluorine, bromine, chlorine, iodine and the like.

“Alkenyl” refers to a branched or unbranched hydrocarbon having at least one carbon-carbon double bond. Non-limiting examples of the alkenyl group include vinyl, allyl, butenyl, isopropenyl, isobutenyl, and the like, and one or more hydrogen atoms of the alkenyl group may be substituted with the same substituents as in the case of the above-described alkyl group. .

“Alkynyl” refers to a branched or unbranched hydrocarbon having at least one carbon-carbon triple bond. Non-limiting examples of the “alkynyl” include ethynyl, butynyl, isobutynyl, propynyl, and the like.

One or more hydrogen atoms in “alkynyl” may be substituted with the same substituents as in the case of the above-described alkyl group.

“Aryl” also includes groups in which an aromatic ring is optionally fused to one or more carbon rings. Non-limiting examples of "aryl" include phenyl, naphthyl, tetrahydronaphthyl, and the like.

In addition, one or more hydrogen atoms in the “aryl” group may be substituted with the same substituents as in the case of the above-described alkyl group.

"Heteroaryl" refers to a monocyclic or bicyclic aromatic organic group containing one or more heteroatoms selected from N, O, P or S, and the remaining ring atoms are carbon. The heteroaryl group may include, for example, 1-5 heteroatoms, and may include 5-10 ring members. The S or N may be oxidized to have various oxidation states.

Examples of heteroaryl include thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2 ,5-oxadiazolyl, 1,3,4-oxadiazolyl group, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1, 3,4-thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol-2-yl, oxazol-4-yl, oxazol-5 -yl, isoxazol-3-yl, isoxazol-4-yl, isoxazol-5-yl, 1,2,4-triazol-3-yl, 1,2,4-triazol-5 -yl, 1,2,3-triazol-4-yl, 1,2,3-triazol-5-yl, tetrazolyl, pyrid-2-yl, pyrid-3-yl, pyrazin-2- yl, pyrazin-4-yl, pyrazin-5-yl, pyrimidin-2-yl, pyrimidin-4-yl, or pyrimidin-5-yl.

The term “heteroaryl” includes where a heteroaromatic ring is optionally fused to one or more aryl, cyclyaliphatic or heterocycles.

A "carbocyclic" group as used in the formula refers to a saturated or partially unsaturated non-aromatic monocyclic, bicyclic or tricyclic hydrocarbon group.

Examples of monocyclic hydrocarbons include cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl and the like. Examples of bicyclic hydrocarbons include bornyl, decahydronaphthyl, bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.1]heptenyl, or bicyclo[2.2.2]octyl. And examples of tricyclic hydrocarbons include adamantly and the like.

A “heterocycle” is a cyclic group comprising at least one heteroatom and may contain 5 to 20 carbon atoms, for example 5 to 10 carbon atoms. Here, the heteroatom is one selected from sulfur, nitrogen, oxygen and boron.

Alkoxy, aryloxy and heteroaryloxy refer herein respectively to alkyl, aryl and heteroaryl bound to an oxygen atom.

It will be described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes and are not limited thereto.

Example 1: Preparation of negative electrode

Poly(styrene-b-divinylbenzene) copolymer microspheres (average particle diameter: about 3 μm) (EPRUI) were added to anhydrous tetrahydrofuran to obtain a mixture containing 5 wt% of a block copolymer.

The mixing weight ratio of the polystyrene block and the polydivinylbenzene block in the block copolymer was about 80:20 (4:1), and the weight average molecular weight of the poly(styrene-b-divinylbenzene) copolymer was about 100,000 Daltons.

Lithium bis(fluorosulfonyl) imide (LiFSI) {LiN(SO ₂ F) ₂ } was added to the copolymer-containing mixture to obtain a composition for forming a protective film. Here, the content of LiFSI was about 30 parts by weight based on 100 parts by weight of the poly(styrene-b-divinylbenzene) copolymer.

The composition for forming a protective film was coated on a lithium metal thin film (thickness: about 20 μm) with a doctor blade to a thickness of about 3 μm.

The coated resultant was dried at about 25° C. and then dried under vacuum at about 40° C. for about 24 hours to prepare a negative electrode having a protective film on the lithium metal thin film.

Example 2-3: Preparation of negative electrode

An anode was manufactured in the same manner as in Example 1, except that the thickness of the protective film was changed to about 1 μm and 8 μm.

Example 4: Preparation of negative electrode

The same method as in Example 1 was followed, except that a poly(acrylonitrile-b-butadiene-b-styrene) block copolymer was further added during the preparation of the composition for forming a protective film.

The content of the poly(acrylonitrile-b-butadiene-b-styrene) copolymer was 2 parts by weight based on 100 parts by weight of the poly(styrene-b-divinylbenzene) copolymer. And the weight average molecular weight of the poly(acrylonitrile-b-butadiene-b-styrene) copolymer was about 100,000 Daltons, and the mixing weight ratio of the polyacrylonitrile block, polybutadiene block and polystyrene block was 25:25:50.

Example 5: Preparation of negative electrode

The content of the poly(acrylonitrile-b-butadiene-b-styrene) copolymer is An anode was manufactured in the same manner as in Example 4, except that it was changed to 1 part by weight based on 100 parts by weight of the poly(styrene-b-divinylbenzene) copolymer.

Example 6-7: Preparation of negative electrode

An anode was manufactured in the same manner as in Example 1, except that the average particle diameter of the poly(styrene-b-divinylbenzene) copolymer microspheres was changed to about 1.3 μm and 8 μm, respectively.

Example 8: Preparation of negative electrode

Example, except that poly(styrene-b-divinylbenzene) copolymer microspheres having a mixing weight ratio of 98:2 (49:1) were used instead of poly(styrene-b-divinylbenzene) copolymer microspheres A negative electrode was prepared by carrying out according to the same method as in 1.

Example 9: Manufacture of lithium metal battery

The composition for forming a protective film prepared according to Example 1 was coated on a lithium metal thin film (thickness: about 20 µm) with a doctor blade to a thickness of about 3 µm. The coated resultant was dried at about 25° C. and further dried at about 40° C. under vacuum to prepare a negative electrode having a protective film on the lithium metal thin film.

Separately, LiCoO ₂ , a conductive agent (Super-P; Timcal Ltd.), polyvinylidene fluoride (PVdF), and N-methylpyrrolidone were mixed to obtain a composition for forming a cathode active material layer. In the composition for forming a positive electrode active material layer, the mixing weight ratio of LiCoO ₂ , the conductive agent and PVDF was 97:1.5:1.5, and the content of N-methylpyrrolidone was LiCoO ₂ At 97 g, about 137 g was used.

The composition for forming the positive electrode active material layer was coated on an aluminum foil (thickness: about 15 μm) and dried at 25° C., and then the dried product was dried at about 110° C. in a vacuum to prepare a positive electrode.

A lithium metal battery (pouch cell) was prepared by interposing a polyethylene separator (porosity: about 48%) between the positive electrode and the negative electrode (thickness: about 20 μm) obtained according to the above procedure.

A liquid electrolyte was added between the positive electrode and the lithium metal negative electrode. Liquid electrolytes include 1.2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (1,1,2) in a 2:8 volume ratio An electrolyte solution in which 1.0M LiN(SO ₂ F) ₂ (hereinafter, LiFSI) was dissolved in a mixed solvent of ,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether: TTE) was used.

Example 10-16: Preparation of lithium metal battery

A lithium metal battery was manufactured in the same manner as in Example 9, except that the negative electrode obtained according to Examples 2 to 8 was used instead of the negative electrode obtained according to Example 1.

Example 17: Preparation of lithium metal battery

LiNi ₀ instead of LiCoO ₂ when preparing a composition for forming a cathode active material _{. 6} Co _{0 . 2} Al _{0 .} A lithium metal battery was prepared in the same manner as in Example 12, except that ₂ O ₂ was used.

Example 18: Preparation of negative electrode

An anode was manufactured in the same manner as in Example 1, except that the average particle diameter of the poly(styrene-b-divinylbenzene) copolymer microspheres was changed to about 50 μm.

Example 19: Preparation of negative electrode

Except for using poly(styrene-co-divinylbenzene) copolymer microspheres having a mixing weight ratio of 95:5 instead of poly(styrene-co-divinylbenzene) copolymer microspheres having a mixing weight ratio of 80:20, A negative electrode was prepared in the same manner as in Example 1.

Example 20-21: Preparation of lithium metal battery

A lithium metal battery was manufactured in the same manner as in Example 9, except that the anodes obtained according to Examples 18 and 19 were respectively used instead of the anodes obtained according to Example 1.

Example 22: Preparation of negative electrode

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm and an average particle diameter of about 8 μm An anode was manufactured in the same manner as in Example 1, except that phosphorus poly(styrene-b-divinylbenzene) copolymer microspheres were used in a 1:1 weight ratio.

Example 23: Preparation of lithium metal battery

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, 3.09 μm, and 2.91 μm, respectively. A negative electrode was prepared in the same manner as in Example 1, except that a mixture of (1:1:1 weight ratio) was used, and a lithium metal battery was prepared in the same manner as in Example 9 using this negative electrode.

Example 24: Preparation of lithium metal battery

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, 2.82 μm, and 3.18 μm, respectively. A negative electrode was prepared in the same manner as in Example 1, except that a mixture of (1:1:1 weight ratio) was used, and a lithium metal battery was prepared in the same manner as in Example 9 using this negative electrode.

Example 25: Preparation of lithium metal battery

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, 2.7 μm, and 3.3 μm, respectively. A negative electrode was prepared in the same manner as in Example 1, except that a mixture of (1:1:1 weight ratio) was used, and a lithium metal battery was prepared in the same manner as in Example 9 using this negative electrode.

Example 26: Preparation of negative electrode

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 8 μm and an average particle diameter of about 3 μm An anode was manufactured in the same manner as in Example 1, except that phosphorus poly(styrene-b-divinylbenzene) copolymer microspheres were used in a weight ratio of 9:1.

Example 27: Preparation of negative electrode

Instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm and an average particle diameter of about 1 μm An anode was manufactured in the same manner as in Example 1, except that phosphorus poly(styrene-b-divinylbenzene) copolymer microspheres were used in a weight ratio of 9:1.

Example 28: Preparation of lithium metal battery

Except for using poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 50 μm instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, A negative electrode was prepared in the same manner as in Example 1, and a lithium metal battery was manufactured in the same manner as in Example 9 using this negative electrode.

Example 29: Preparation of lithium metal battery

Except for using poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 100 μm instead of poly(styrene-b-divinylbenzene) copolymer microspheres having an average particle diameter of about 3 μm, A negative electrode was prepared in the same manner as in Example 1, and a lithium metal battery was manufactured in the same manner as in Example 9 using this negative electrode.

comparative example 1: Manufacture of lithium metal battery

LiCoO ₂ , a conductive agent (Super-P; Timcal Ltd.), polyvinylidene fluoride (PVdF), and N-methylpyrrolidone were mixed to obtain a composition for forming a cathode active material layer. In the composition for forming the positive active material layer, the mixing weight ratio of LiCoO ₂ , the conductive agent and PVDF was 97:1.5:1.5.

The composition for forming the positive electrode active material layer was coated on an aluminum foil (thickness: about 15 μm) and dried at 25° C., and then the dried product was dried at about 110° C. in a vacuum to prepare a positive electrode.

A lithium metal battery was prepared by interposing a polyethylene separator (porosity: about 48%) between the positive electrode obtained according to the above process and the lithium metal negative electrode (thickness: about 20 μm). Here, a liquid electrolyte was added between the positive electrode and the lithium metal negative electrode.

Liquid electrolytes include 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (1,1) in a 2:8 volume ratio An electrolyte solution in which 1.0M LiN(SO ₂ F) ₂ (hereinafter, LiFSI) was dissolved in a mixed solvent of ,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether: TTE) was used.

comparative example 2

Polystyrene was added to anhydrous tetrahydrofuran to obtain a mixture containing 5% by weight of polystyrene. The weight average molecular weight of polystyrene was about 100,000 Daltons.

Lithium bis(fluorosulfonyl) imide (LiFSI) {LiN(SO ₂ F) ₂ } was added to the polystyrene-containing mixture to obtain a composition for forming a protective film. Here, the content of LiFSI was about 30 parts by weight based on 100 parts by weight of the polystyrene.

The composition for forming a protective film was coated on a lithium metal thin film (thickness: about 20 µm) with a doctor blade to a thickness of about 3 µm.

The coated resultant was dried at about 25° C. and then dried under vacuum at about 40° C. for about 24 hours to prepare a negative electrode having a protective film on the lithium metal thin film.

comparative example 3-4

When preparing the composition for forming a protective film, alumina (Al ₂ O ₃ ) was used instead of poly(styrene-b-divinylbenzene) copolymer microspheres, and the average particle diameter of alumina was changed to 1 μm and 0.2 μm, respectively, except that A protective film and a negative electrode were prepared in the same manner as in Example 1.

evaluation example 1: Scanning electron microscope analysis

1) Examples 1 and 4

The state of the surface of the anode prepared according to Examples 1 and 4 was analyzed using a scanning electron microscope (SEM).

SEM photographs of the negative electrode prepared according to Example 1 are shown in FIGS. 2A to 2D, and SEM photographs of the lithium negative electrode prepared according to Example 4 are as shown in FIGS. 3A to 3C. The protective film of the negative electrode shown in FIG. 3A represents a monodisperse single layer, and the protective film of the negative electrode shown in FIGS. 3B and 3C has a double layer structure.

2A to 2D, in the negative electrode of Example 1, it can be seen that the microspheres are arranged in a single-layer structure on the surface of the lithium metal. Since they were arranged in this structure, aggregation between mycospheres did not occur.

As shown in FIGS. 3A to 3C , it can be seen that the protective film formed on the surface of the lithium metal thin film in the lithium negative electrode prepared according to Example 4 has microspheres monodispersed and has a closed packed arrangement. there was.

2) Example 22

The state of the surface of the lithium negative electrode prepared according to Example 22 was analyzed using a scanning electron microscope (SEM). The SEM analysis picture is as shown in FIG. 3D .

Referring to this, in the lithium negative electrode of Example 22, it was found that microspheres of two sizes (particle diameters) were uniformly well dispersed on the upper part of the lithium metal.

evaluation example 2: Lithium deposition density and scanning electron microscope analysis

1) Examples 9, 12, 28, 29 Comparative Examples 1 to 4

For the lithium metal batteries prepared according to Examples 9, 12, 28, 29, and Comparative Examples 1 to 4, the voltage was 4.40V at a current of 0.1C rate (0.38mA/cm ² ) at 25° C. After constant current charging was performed until (vs. Li), a cut-off was performed at a current of 0.05C rate while maintaining 4.40V in a constant voltage mode. After one-time charging, the change in the thickness of the pouch exterior and the thickness deviation of the lithium electrodeposition layer were measured using a lithium micrometer in the lithium metal battery, and are shown in Table 1 below. In addition, by measuring the thickness of the lithium electrodeposition layer formed on the upper portion of the negative electrode, the electrodeposition density evaluation results are shown in Table 2 below.

division Change in pouch exterior thickness
(μm) Thickness deviation of lithium electrodeposited layer
(μm) Example 9 38-40 ±3
Example 12 30-31 ±3
Comparative Example 1 50-60 ±10 Comparative Example 2 50 ±10
Comparative Example 3 42-43 ±3
Comparative Example 4 46-48 ±5

Referring to Table 1, the lithium metal batteries of Examples 9 and 12 showed a small change in the thickness of the pouch exterior compared to the case of Comparative Examples 1 to 4. In addition, in the lithium metal batteries of Examples 9 and 12, the thickness variation of the lithium electrodeposition layer was also reduced as compared with Comparative Examples 1, 2 and 4.

In addition, as a result of the evaluation, a uniform thickness increase was observed for the lithium metal batteries of Examples 9 and 12 for each point compared to Comparative Examples 1 to 4.

The lithium metal batteries prepared according to Examples 28 and 29 showed a small change in pouch exterior thickness compared to the lithium metal batteries of Comparative Examples 1 to 4.

division Lithium deposition density
(g/cc) (g/cm3) Thickness of lithium electrodeposition layer (㎛) Example 9 0.207-0.225 35-38 Example 12 0.260-0.270 28-30 Comparative Example 1 0.134-0.161 45 Comparative Example 2 0.134 50 Comparative Example 3 0.18-0.20 39-41 Comparative Example 4 0.17-0.18 44-46

Referring to Table 2, it can be seen that the lithium metal batteries prepared according to Examples 9 and 12 significantly increased the electrodeposition density by 50% or more as compared with the case of Comparative Example 1. And the lithium metal batteries prepared according to Examples 9 and 12 showed an increase in electrodeposition density compared to Comparative Examples 2 to 4, and the lithium metal batteries prepared according to Examples 9 and 12 were prepared according to Comparative Examples 1-4. The thickness of the lithium electrodeposition layer was reduced compared to the case of .

On the other hand, the lithium metal battery prepared according to Example 9 and Comparative Example 1 was charged with a constant current at 25° C. at a rate of 0.1 C until the voltage reached 4.40 V (vs. Li), and then a lithium electrodeposition layer was formed. The cross-sectional state of the surface of the lithium metal anode was analyzed using a scanning electron microscope (SEM).

4A and 5A schematically show a structure in which a lithium negative electrode is formed on a copper thin film serving as a negative electrode current collector in a lithium metal battery prepared according to Example 9 and Comparative Example 1, respectively.

Referring to FIG. 4A , the negative electrode has a structure in which a lithium metal electrode 41 is formed on the current collector 40 , and a protective film 42 made of polystyrene microspheres 43 is laminated thereon.

The above-described scanning electron microscope analysis results are shown in FIGS. 4B, 4D, and 5B to 5D. 4b and 4c show the surface of the anode in the lithium metal battery prepared according to Example 9, and FIGS. 5b to 5c show the surface of the anode in the lithium metal battery prepared according to Comparative Example 1.

Referring to FIG. 5A, in the lithium metal battery prepared according to Comparative Example 1, the negative electrode has a structure in which a lithium metal electrode 51 is stacked on a current collector 50, and lithium dendrites 52 are randomly formed thereon. have

As shown in FIGS. 5B and 5C, in the lithium metal battery prepared according to Comparative Example 1, it was found that lithium dendrites were randomly grown and formed on the lithium metal.

In the lithium metal battery prepared according to Example 9, as shown in FIGS. 4B and 4C, unlike the case of FIGS. 5A and 5B, lithium dendrites were hardly formed. In addition, as shown in FIG. 4d , in the lithium metal battery of Example 9, it was confirmed that a very dense and compact lithium deposit layer was formed, unlike the case of FIG. 5d .

2) Examples 23 to 25

For lithium metal batteries prepared according to Examples 23 to 25, constant current charging was performed at 25° C. with a current of 0.1C rate (0.38 mA/cm ² ) until the voltage reached 4.40V (vs. Li), followed by constant voltage Mode was cut-off at a current of 0.05C rate while maintaining 4.40V. After one-time charging, the change in the pouch exterior thickness and the thickness deviation of the lithium electrodeposition layer were measured using a lithium micrometer in the lithium metal battery, and are shown in Table 3 below. In addition, by measuring the thickness of the lithium electrodeposition layer formed on the upper portion of the negative electrode, the electrodeposition density evaluation results are shown in Table 3 below.

In Table 3 below, the difference in particle size of poly(styrene-b-divinylbenzene) copolymer microspheres (MS) constituting the protective film of each negative electrode is calculated according to the following formula.

MS particle size difference (%) = {(Maximum MS particle diameter - MS average particle diameter) / average particle diameter of particles} X 100

MS particle size difference (%) pouch exterior
Thickness change (㎛) lithium electrodeposited layer
Thickness deviation (㎛) Lithium deposition density (g/cc) (g/cm ³ ) Thickness of lithium electrodeposition layer (㎛) Example 23 (± 3%) 30-31 ± 3 0.260-0.270 28-30 Example 24 (± 6%) 31-33 ± 3 0.245-0.260 29-31 Example 25 (± 10%) 32-35 ± 3 0.225-0.255 30-33

3) Examples 26 and 27

For the lithium metal batteries prepared according to Examples 26 and 27 For the lithium metal batteries of Examples 23 to 25 For the lithium metal batteries of Examples 23 to 25 Lithium electrodeposition density, pouch exterior thickness change, lithium electrodeposition layer The thickness and thickness deviation were measured and shown in Table 4 below.

division pouch exterior
Thickness change (㎛) lithium electrodeposited layer
Thickness deviation (㎛) Lithium deposition density (g/cc) (g/cm ³ ) Thickness of lithium electrodeposition layer (㎛) Example 26
31-33 ±4 0.255-0.265 29-31 Example 27
29-31 ±3 0.270-0.280 27-29

evaluation example 3: Impedance measurement

For the lithium metal battery prepared according to Example 17 and the lithium metal battery prepared according to Comparative Example 1, using an impedance analyzer (Solartron 1260A Impedance/Gain-Phase Analyzer) at 25° C. according to the 2-probe method. The resistance was measured. The amplitude was ±10 mV, and the frequency range was 0.1 Hz to 1 MHz.

FIG. 6 shows a Nyguist plot of the impedance measurement result when the elapsed time after the preparation of the lithium metal battery prepared according to Example 17 Comparative Example 1 was 24 hours. In FIG. 6 , the interfacial resistance between the negative electrode and the electrolyte is determined by the position and size of the semicircle.

As shown in FIG. 6 , it was found that the lithium secondary battery prepared according to Example 17 had a small interfacial resistance compared to that of Example 1.

evaluation example 4: charging and discharging Characteristics (discharge capacity)

1) Example 9 and Comparative Example 1

With respect to the lithium metal battery prepared according to Example 9 and Comparative Example 1, constant current was charged at 25° C. at a rate of 0.1 C until the voltage reached 4.40 V (vs. Li), and then maintained at 4.40 V in the constant voltage mode. while cutting off at a current of 0.05C rate. Then, it was discharged at a constant current of 0.1C rate until the voltage reached 2.8V (vs. Li) during discharge (Hwaseong stage, 1 ^st cycle). This charging and discharging process was performed two more times to complete the formation process.

The lithium metal battery that has undergone the formation step is charged at room temperature (25° C.) with a constant current of 0.7 C until it reaches a voltage range of 4.4 V compared to lithium metal, and then with a cut-off voltage of 3.0 V at 0.5 C. ), constant current discharge was performed with a current of 0.5C.

The above-described charging/discharging process was repeated 99 times, and the charging/discharging process was repeated 100 times in total. The capacity retention rate is calculated from the following Equation 1, respectively.

[Equation 1]

Capacity retention rate (%) = (100th cycle discharge capacity/1st cycle discharge capacity) × 100

The capacity retention rate evaluation results are shown in FIG. 7 .

Referring to FIG. 7 , it was found that the lithium metal battery prepared according to Example 9 had significantly improved capacity retention compared to the lithium metal battery prepared according to Comparative Example 1.

2) Example 17 and Comparative Example 1

Discharge capacity change capacity, retention rate, and Coulomb efficiency were measured for lithium metal batteries prepared according to Example 17 and Comparative Example 1.

The measurement results are shown in FIGS. 8A to 8C .

With reference to this, the lithium metal battery of Example 17 exhibited improved discharge capacity, capacity retention rate and Coulomb efficiency compared to the case of Comparative Example 1.

evaluation example 5: tensile modulus

The composition for forming a protective film prepared according to Examples 1-4 and Comparative Examples 3-4 was cast on a substrate, and tetrahydrofuran (THF) from the casting result was added at about 25° C. in an argon glove box for 24 hours. It was evaporated slowly and dried under vacuum at 25° C. for 24 hours to prepare a protective film in the form of a film. At this time, the thickness of the protective film was about 50 μm.

The tensile modulus of the protective film was measured using DMA800 (TA Instruments), and the protective film specimen was prepared through ASTM standard D412 (Type V specimens). The tensile modulus is also called Young's modulus.

The change in strain with respect to the stress was measured for the protective film at a rate of 5 mm per minute at 25 ^° C. and a relative humidity of about 30%. The tensile modulus of elasticity was obtained from the slope of the stress-strain curve.

As a result of the measurement, the protective film prepared according to Examples 1 to 4 was 10 ⁶ Pa or more, indicating that the tensile modulus of elasticity was improved compared to that of Comparative Examples 3-4. When the protective film prepared according to Examples 1-4 having these characteristics is used, the volume change of the lithium metal negative electrode and the growth of lithium dendrites can be effectively suppressed.

evaluation example 6: ionic conductivity

The ionic conductivity of the protective film prepared according to Example 1-2 was measured according to the following method.

The ionic conductivity was evaluated by applying a voltage bias of 10 mV to the protective film in a frequency range of 1 Hz to 1 MHz, scanning the temperature, and measuring the resistance.

As a result of the evaluation, it was found that the protective film prepared according to Example 1 had excellent ionic conductivity. In addition, the protective film prepared according to Example 2 exhibited an ionic conductivity equivalent to that of the protective film prepared according to Example 1.

In the above, one embodiment has been described with reference to the drawings and embodiments, but this is only an example, and those of ordinary skill in the art can understand that various modifications and equivalent other embodiments are possible therefrom. will be. Accordingly, the protection scope of the present invention should be defined by the appended claims.

10: current collector 11: lithium electrode
12: Shield 13: Particles
14: ion conductive polymer
15: SEI 16: lithium electrodeposition layer
21: positive electrode 22: negative electrode
23: protective film 24: electrolyte
30: lithium metal battery 34: case

Claims (29)

a lithium metal electrode comprising lithium metal or a lithium metal alloy; and
and a protective film disposed on at least a portion of the lithium metal electrode,
The Young's modulus of the protective film is 10 ⁶ Pa or more,
It contains one or more particles selected from organic particles, inorganic particles, and organic-inorganic particles having a size greater than 1 μm and less than or equal to 100 μm,
The protective layer includes a lithium salt,
The particles of the protective film include a block copolymer containing a styrene repeating unit,
The block copolymer containing the styrene repeating unit is a poly(styrene-divinylbenzene) copolymer, poly(styrene-ethylene-butylene-styrene) copolymer, poly(styrene-methylmethacrylate) copolymer, poly( Styrene-acrylonitrile) copolymer, poly(styrene-vinylpyridine) copolymer, poly(acrylonitrile-butadiene-styrene) copolymer, poly(acrylonitrile-ethylene-propylene-styrene) copolymer, poly(methyl Methacrylate-acrylonitrile-butadiene-styrene) copolymer, poly(methacrylate-butadiene-styrene) copolymer, poly(styrene-acrylate) copolymer and poly(acrylonitrile-styrene-acrylate) copolymer A negative electrode for a lithium metal battery, which is one or more block copolymers selected from the group consisting of coalescing. According to claim 1,
The protective film is an anode for a lithium metal battery comprising a liquid electrolyte. 3. The method of claim 2,
The liquid electrolyte is an anode for a lithium metal battery occupying 30 to 60% by volume of the protective film. 3. The method of claim 2,
The liquid electrolyte is an anode for a lithium metal battery comprising a lithium salt and an organic solvent. According to claim 1,
A negative electrode for a lithium metal battery having a structure in which particles of the protective film are crosslinked. delete delete According to claim 1,
In the passivation layer, at least one particle is i) silsesquioxane having a cage structure, a metal-organic framework ₍ MOF), Li ₁ + _{x + y} Al _x Ti _{2 -x} Si _y P _{3 -y} O ₁₂ (0<x<2, 0≤y<3), BaTiO ₃ , Pb(Zr _p Ti _1-p )O ₃ (0≤p≤1) (PZT), Pb _{1 - x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT)(O≤x<1, O≤y<1),Pb(Mg ₃ Nb _2/3 )O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , Na ₂ O, MgO, NiO, CaO, BaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiO ₂ , SiC, Li ₃ PO ₄ , Li _x Ti _y (PO ₄ ) ₃ (0<x<2,0<y<3), Li _x Al _y Ti _z (PO ₄ ) ₃ (0<x<2, 0<y<1, 0<z<3), Li _{1 +x +y} (Al _p Ga _{1 -p} ) _x (Ti _q Ge _1-q ) _2-x Si _y P _3-y O ₁₂ (O≤x≤1, O≤y≤1), Li _x La _y TiO ₃ (0<x<2, 0<y<3), LixGeyPzSw(0<x<4, 0<y<1, 0<z<1, 0<w<5), Li _x N _y (0<x< 4, 0<y<2), Li _x Si _y S _z (0<x<3,0<y<2, 0<z<4), Li _x P _y S _z (0≤x<3, 0<y<3,0<z<7), Li ₂ O, LiF, LiOH, Li ₂ CO ₃ , LiAlO ₂ , Li ₂ O-Al ₂ O ₃ -SiO ₂ -P ₂ O ₅ -TiO ₂ -GeO ₂ , Li _{3 + x} La ₃ M ₂ O ₁₂ (M = Te, Nb, or Zr) (0≤x≤5) comprising one or more particles selected from; or
ii) A negative electrode for a lithium metal battery, which is a crosslinked body of the particles. delete According to claim 1,
The protective film is an anode for a lithium metal battery further comprising an ion conductive polymer. 11. The method of claim 10,
A negative electrode for a lithium metal battery wherein the ion conductive polymer is a homopolymer, a copolymer, or a crosslinked polymer. 11. The method of claim 10,
The ion conductive polymer is a lithium metal battery negative electrode that is a block copolymer containing polystyrene or styrene-based repeating units. The method of claim 1,
The negative electrode for a lithium metal battery, wherein the protective film is a single layer or a multilayer film including one or more particles selected from organic particles, inorganic particles, and organic/inorganic particles having different sizes. According to claim 1,
The particle is a negative electrode for a lithium metal battery having an average particle diameter of 1.1 to 50㎛ microspheres. According to claim 1,
The particles include poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 3 μm and poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 8 μm in a 1:1 weight ratio. or a 1:1 weight ratio of poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 3 μm and poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 1.3 μm. or a 1:1 weight ratio of poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 3 μm and poly(styrene-co-divinylbenzene) copolymer microspheres having an average particle diameter of 1.1 μm. A negative electrode for a lithium metal battery comprising. According to claim 1,
The particles of the protective film include a cross-linked polymer,
The crosslinking degree of the crosslinking polymer (degree of crosslinking) is 10 to 30% of the negative electrode for a lithium metal battery. According to claim 1,
The porosity of the protective film is 25 to 50% of the negative electrode for a lithium metal battery. According to claim 1,
A negative electrode for a lithium metal battery having a thickness of 1 to 10 μm of the protective film. According to claim 1,
The protective film is an ionic liquid, a metal salt containing a Group 1 or 2 element, and at least one selected from a nitrogen-containing additive, boron nitride, or a negative electrode for a lithium metal battery further comprising a mixture thereof. 20. The method of claim 19,
The ionic liquid is i) ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, At least one cation selected from triazolium series and mixtures thereof,
ii)BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- , AlCl ₄ ^- , HSO ₄ ^- , ClO ₄ ^- , CH ₃ SO ₃ ^- , CF ₃ CO ₂ ^- , Cl ^- , Br ^- , I ^- , SO ₄ ² - , CF ₃ SO ₃ ^- , (FSO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ )(CF ₃ SO ₂ )N ^- , and (CF ₃ SO ₂ ) ₂ N ^- At least one negative electrode for a lithium metal battery selected from compounds containing one or more anions selected from at least one selected from. 20. The method of claim 19,
The metal salt containing the group 1 element or group 2 element is at least one metal salt containing at least one selected from Cs, Rb, K, Ba, Sr, Ca, Na, and Mg,
The nitrogen-containing additive includes inorganic nitrate, organic nitrate, inorganic nitrite, organic nitrite, organic nitro compound, organic nitroso compound, NO compound, and nitrite. At least one negative electrode for a lithium metal battery selected from the group consisting of lithium (Li ₃ N). According to claim 1,
The lithium salt is LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiSbF ₆ , LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiPF ₃ (CF ₃ ) ₃ and at least one selected from LiB(C ₂ O ₄ ) ₂ , Anode for lithium metal batteries. A lithium metal battery comprising a positive electrode, the negative electrode of any one of claims 1 to 5, 8, 10 to 22, and an electrolyte interposed therebetween. 24. The method of claim 23,
A lithium metal battery having a thickness of 40 μm or less of a lithium electrodeposition layer in the lithium metal battery. 24. The method of claim 23,
A lithium electrodeposition layer is disposed on the anode, and the lithium electrodeposition density of the lithium electrodeposition layer is 0.2 to 0.3 g/cm ³ A lithium metal battery. 24. The method of claim 23,
A lithium metal battery having a lithium electrodeposition density increase rate of 50% or more compared to a lithium metal battery employing lithium metal as an anode without a protective film in the lithium metal battery. 24. The method of claim 23,
A lithium metal battery wherein the electrolyte comprises at least one selected from a liquid electrolyte, a solid electrolyte, a gel electrolyte, and a polymer ionic liquid. 25. The method of claim 24,
A lithium metal battery wherein the lithium metal battery includes a separator. 24. The method of claim 23,
The lithium metal battery further includes a separator, the electrolyte is a liquid electrolyte, and the lithium metal battery has a structure in which a negative electrode, a separator, a liquid electrolyte and a positive electrode are sequentially stacked.

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