KR20170026098A - Lithium metal battery including lithium metal anode, method of protecting the lithium metal anode, and protective layer prepared according to the method - Google Patents

Abstract

Suggested is a lithium metal battery which includes: a lithium metal anode; a protective layer which is arranged on an upper side of the lithium metal anode and includes i) a polymer and ii) one or more selected from nitrogen-containing additives and metal salt including I group or II group elements; a cathode; and a liquefied electrolyte which is interposed between the cathode and the protective layer. One or more selected from nitrogen-containing additives and metal salt including I group or II group elements are insoluble in an organic solvent of the liquefied electrolyte. Accordingly, the present invention can suppress the formation of lithium dendrite on the surface of the lithium metal anode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium metal battery including a lithium metal anode, a method for protecting the lithium metal anode, and a protective film prepared according to the method. }

A lithium metal battery including a lithium metal negative electrode, a method of protecting the lithium metal negative electrode, and a protective film produced by the method.

Lithium secondary batteries are high performance secondary batteries having the highest energy density among currently commercialized secondary batteries and can be used in various fields such as electric vehicles.

As the cathode of the lithium secondary battery, a lithium metal thin film may be used. When such a lithium metal thin film is used as a negative electrode, reactivity with a liquid electrolyte during charging and discharging is high due to high reactivity of lithium. Or a dendrite is formed on the lithium negative electrode thin film, so that the lifetime and stability of the lithium secondary battery employing the lithium metal thin film may be deteriorated, and improvement is required.

One aspect is to provide a lithium metal battery in which the formation of lithium dendrite is suppressed on the surface of the lithium metal cathode.

Another aspect provides a method for protecting a lithium metal anode of a lithium metal battery.

Another aspect provides a protective film produced according to the above-described method.

On one side

Lithium metal cathode;

A protective film disposed on the lithium metal cathode and comprising at least one selected from the group consisting of i) a polymer, ii) a metal salt containing a Group 1 or Group 2 element, and a nitrogen-containing additive;

anode; And

And a liquid electrolyte interposed between the protective film and the anode,

Wherein at least one selected from a metal salt containing a Group 1 element or a Group 2 element and a nitrogen-containing additive is insoluble in an organic solvent of a liquid electrolyte.

According to another aspect, there is provided a method for forming a protective film, comprising: i) mixing a polymer and at least one selected from the group consisting of a metal salt containing a Group 1 or 2 element and a nitrogen containing additive;

Supplying the composition for forming a protective film to a lithium metal anode; And

And drying the resultant to form a protective film. The above-described method for protecting the lithium metal anode is provided.

According to another aspect, there is provided a protective film produced according to the above-described method.

The lithium metal battery according to an embodiment effectively suppresses the growth of lithium dendrites on the surface of the lithium metal cathode, increases the lithium electrodeposition density, decreases the interface resistance between the lithium metal cathode and the protective film, and increases the lithium ion mobility do. As a result, it is possible to produce a lithium metal battery having an improved rate-limiting performance and a long lifetime.

FIG. 1 schematically illustrates the structure of a lithium metal battery according to one embodiment.
2 schematically shows a structure of a lithium metal battery according to another embodiment.
3A and 3B are electron micrographs of a lithium metal anode surface after 0.1 C charging in a lithium metal battery manufactured according to Example 2 and Comparative Example 1, respectively.
FIGS. 4A and 4B are electron micrographs of lithium metal cathodes obtained after 0.1 C charging in the lithium metal batteries prepared according to Example 2 and Comparative Example 1, respectively.
FIG. 5 shows the results of impedance analysis for the lithium metal battery prepared in Example 2 and the lithium metal battery prepared in Comparative Example 1. FIG.
6 is a graph showing a change in discharge capacity according to the number of cycles in the lithium metal battery produced according to Example 1, Comparative Example 1, and Comparative Example 4.
7 shows the change in the Coulomb efficiency with the number of cycles in the lithium metal battery produced according to Example 1, Comparative Examples 1 and 4.
Fig. 8 shows the stress-strain curve of the protective film prepared according to Example 1. Fig.
FIG. 9 shows the rate-limiting performance of a lithium metal battery produced according to Example 2 and Comparative Example 1. FIG.
10 is a graph showing changes in cell voltage with respect to a symmetric cell using the protective film of Example 2 and the lithium metal thin film of Comparative Example 1. FIG.

Hereinafter, an exemplary lithium metal battery, a method of manufacturing the same, a method for protecting a lithium metal anode of the lithium metal battery, and a protective film manufactured according to the method will be described in detail with reference to the accompanying drawings.

Lithium metal cathode; A protective film disposed on the lithium metal cathode, the protective film comprising: i) a polymer; ii) a metal salt comprising a Group 1 or Group 2 element; and a nitrogen-containing additive; anode; And a liquid electrolyte interposed between the protective film and the positive electrode, wherein at least one selected from the group consisting of a metal salt containing a Group 1 element or a Group 2 element and a nitrogen-containing additive is insoluble in an organic solvent of a liquid electrolyte .

The metal salt containing the group I or II element is a metal salt containing at least one selected from Cs, Rb, K, Ba, Sr, Ca, Na and Mg. Examples of such salts are (methylsulfonyl-trifluoromethyl) Cs-bis imide {CsTFSI: Cs (bis (trifluoromethylsulfonyl ) imide)}, CsNO 3, CsPF 6, Cs -bis (sulfonyl fluorophenyl) imide {CsFSI: Cs (bis (fluorosulfonyl) imide)} , CsAsF 6, CsClO 4, CsBF 4, RbTFSI, RbNO 3, RbPF 6, RbFSI, RbAsF 6, RbClO 4, RbBF 4, KTFSI, KNO 3, KPF 6, KFSI, KAsF 6, _{KClO 4, KBF 4, NaTFSI,} NaNO 3, NaPF 6, NaFSI, NaAsF 6, NaClO 4, NaBF 4, Ba (TFSI) 2, Ba (NO 3) 2, Ba (PF 6) 2, Ba (FSI) 2 _{, Ba (AsF 6) 2,} Ba (ClO 4) 2, Ba (BF 4) 2, Sr (TFSI) 2, Sr (NO 3) 2, Sr (PF 6) 2, Sr (FSI) 2, Sr ( _{AsF 6) 2, Sr (ClO} 4) 2, Sr (BF 4) 2, Ca (TFSI) 2, Ca (NO 3) 2, Ca (PF 6) 2, Ca (FSI) 2, Ca (AsF 6) _{2, Ca (ClO 4) 2} , Ca (BF 4) 2, Mg (TFSI) 2, Mg (NO 3) 2, Mg (PF 6) 2, Mg (FSI) 2, Mg (AsF 6) 2, Mg (ClO ₄ ) ₂ and Mg (BF ₄ ) ₂ . Wherein TFSI represents bis (trifluoromethanesulfonyl) imide, and FSI represents bisfluorosulfonylimide.

TFSI FSI

Means that the solubility of the nitrogen-containing additive in the organic solvent of the liquid electrolyte at 25 [deg.] C is lower than that of the liquid Is less than 100 parts per million (ppm) per liter of organic solvent in the electrolyte.

The lithium metal negative electrode has a large electric capacity per unit weight, so that it is possible to realize a high capacity battery. In the case of a lithium metal anode, a dendrite structure is formed and grown during the deposition / dissolution of lithium ions, which may cause a short circuit between the anode and the cathode. In addition, the lithium metal negative electrode has high reactivity to the electrolyte and may cause a side reaction with the electrolyte, thereby decreasing the cycle life of the battery. In addition, as the charge and discharge of the lithium metal battery is repeated, the battery volume and thickness are changed. As a result, lithium desorption occurs from the cathode. In order to compensate for this, a protective film is required to complement the surface of the lithium metal cathode.

In a lithium metal battery having a lithium metal anode, a method of adding an additive such as cesium salt to a liquid electrolyte or using a polymer electrolyte as a cathode protecting film has been proposed in order to suppress the growth of lithium dendrites.

However, when an additive such as a cesium salt is added to a liquid electrolyte, the cesium salt does not dissolve in the liquid electrolyte, making it difficult to apply it to an actual battery system. The cesium salt inhibits the migration of lithium ions or participates in an electrochemical reaction at the anode to degrade cell performance.

When the lithium metal cathode protection film is used, the interfacial resistance between the protection film and the lithium cathode is increased due to the polymer electrolyte, so that the cell performance of the lithium metal battery may be deteriorated.

Accordingly, the present inventors have conducted extensive studies to solve the above-mentioned problems, and after a lot of researches, the present inventors have found that a protective film comprising at least one selected from a metal salt containing a Group 1 or Group 2 element and a nitrogen- A lithium metal battery is provided.

At least one selected from the group consisting of a metal salt containing a group I or II element and a nitrogen-containing additive is insoluble in an organic solvent of a liquid electrolyte. For example, the solubility of the nitrogen-containing additive in the organic solvent of the liquid electrolyte at 25 DEG C is less than 100 parts per million per liter (ppm / L) of the organic solvent of the liquid electrolyte, for example less than 75 ppm / L, / L.

In view of solubility characteristics, when a protective film is used which is stably present only on the surface of a lithium metal anode and is limited in at least one of mobility and a nitrogen-containing additive selected from the group consisting of metal salts containing Group 1 or Group 2 elements, And does not interfere with the movement.

In addition, the metal of the metal salt containing the Group 1 or Group 2 element has a larger atomic size than that of lithium, and if it is contained in the protective layer, the metal stain hindrance effect causes a lithium dendrite Can be inhibited from growing. The metal cation (for example, Cs or rubidium ion) of the metal salt has a small effective reduction potential as compared with the reduction potential of lithium ion, so that the metal salt is reduced or applied during the lithium deposition process Without process, metal cations form a positive charge electrostatic shield around the initial growth tip of the protuberance on the surface of the lithium metal cathode. When such a positive electrostatic shield is formed, the growth of lithium dendrites on the surface of the lithium metal cathode can be effectively inhibited. As described above, the content of the metal salt is important for the metal salt to have a small effective reduction potential as compared with the reduction potential of lithium. The content of the metal salt is controlled in the range of 0.1 to 100 parts by weight based on 100 parts by weight of the polymer in the protective film.

In addition, the protective film is excellent in mechanical strength and flexibility, so that the effect of suppressing the formation of lithium dendrite is excellent, and an ion conductive film having high ion conductivity is formed between the lithium metal anode and the protective film. The ion conductive film reduces the interfacial resistance between the lithium metal cathode and the protective film by increasing the ionic conductivity and the lithium ion mobility of the protective film. The ion conductive film contains, for example, lithium nitride (Li ₃ N).

In addition, the protective layer improves the electrophoresis morphology of the lithium metal cathode by chemically improving the lithium desorption / desorption process to increase the electrodeposition density on the surface of the lithium metal cathode, Thereby improving ion mobility. As described above, at least one selected from the metal salt and the nitrogen-containing additive is present in a protective film on the surface of the lithium metal anode, and at least one selected from the metal salt and the nitrogen-containing additive is dispersed in the liquid electrolyte or approaches the anode, Thereby preventing the reaction from occurring. As a result, it is possible to produce a lithium metal battery with improved rateing performance and life.

The nitrogen containing additive contained in the protective film can be, but not limited to, inorganic nitrate, organic nitrate, inorganic nitrite, organic nitrite, organic nitro compound, organic An organic compound, a nitro compound, an NO compound, and lithium nitride (Li ₃ N).

The inorganic nitrate is 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, a C1 to C20 dialkyl imide Is at least one selected from the group consisting of zirconium nitrate, zirconium nitrate, zirconium nitrate, zirconium nitrate, zirconium nitrate, zirconium nitrate, zirconium nitrate, And the organic nitrite is at least one selected from the group consisting of ethylnitrite, propylnitrite, butylnitrite, pentylnitrite, and octylnitrite.

Examples of the organic nitro compound include at least one selected from the group consisting of nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene and nitropyridine. And the N-O compound is at least one selected from the group consisting of, for example, pyridine N-oxide, C1 to C20 alkylpyridine N-oxide, and tetramethylpiperidine 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 I or II element is cesium bistrifluoromethylsulfonylimide (CsTFSI), and CsNO _3, CsPF _6, CsFSI, CsAsF _6, CsClO _4, and ₄ CsBF least one selected from, for example, be CsTFSI.

The content of at least one selected from a metal salt containing a group 1 or group 2 element and a nitrogen-containing additive in the protective film 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 the group consisting of metal salts containing Group 1 or Group 2 elements and nitrogen containing additives is within the above range, the effect of inhibiting the growth of lithium dendrites and the effect of reducing the interface resistance between the lithium metal anode surface and the protective film, Can be produced.

According to one embodiment, the protective film may comprise only a metal salt containing a group I or II element. In this case, the content of the metal salt containing a Group 1 or Group 2 element 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,

According to another embodiment, the protective film 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 30 parts by weight, specifically 1 to 30 parts by weight, based on 100 parts by weight of the polymer.

The protective film may contain, for example, both a metal salt containing a Group 1 or 2 element and a nitrogen-containing additive. In this case, the content of the metal salt containing a group 1 or group 2 element is 0.01 to 99.99 parts by weight, for example, 0.1 to 30 parts by weight, for example, 1 to 30 parts by weight, based on 100 parts by weight of the polymer, The content of the additive is 0.01 to 99.99 parts by weight, for example, 0.1 to 30 parts by weight, specifically 1 to 30 parts by weight, based on 100 parts by weight of the polymer.

The weight ratio of the metal salt containing the Group 1 or Group 2 element to the nitrogen containing additive in the protective film according to one embodiment is 1: 9 to 9: 1, for example, 1: 2 to 2: 1, specifically 1: 1 . When the mixing ratio by weight of the metal salt containing a Group 1 or Group 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 lithium ion mobility property in the electrolyte are excellent, .

The protective film includes a polymer. The polymer may be a homopolymer, at least one polymer selected from block copolymers and graft copolymers, or a mixture thereof. The polymer may have properties such that it is not soluble in the organic solvent of the liquid electrolyte, for example. Unlike a conventional polyethylene-based protective film, the use of a polymer having such properties is excellent in chemical resistance to a liquid electrolyte containing a carbonate-based organic solvent. And the occurrence of a short circuit inside the battery due to cracks or the like in the protective film is very excellent.

The polymer may be at least one selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, polymethyl acrylate, polyethyl methacrylate, polyethyl acrylate, polypropyl methacrylate, polypropyl acrylate, polybutyl acrylate, polybutyl methacrylate , Polyphenyl methacrylate, polypentyl methacrylate, polypentyl acrylate, polycyclohexyl methacrylate, polycyclohexyl acrylate, polyhexyl methacrylate, polyhexyl acrylate, polyglycidyl acrylate, polyglycidyl methacrylate And polyacrylonitrile can be mentioned.

The polymer contained in the protective film is a block copolymer including a first polymer block and a second polymer block. The first polymer block may be selected from the group consisting of polystyrene, hydrogenated polystyrene, polymethacrylate, poly (methyl methacrylate), polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide, polyethylene, polybutylene, polypropylene, poly 4-methylpentene-1), poly (butylene terephthalate), poly (isobutyl methacrylate), poly (ethylene terephthalate), polydimethylsiloxane, polyacrylonitrile, polymaleic acid, polymaleic anhydride, At least one selected from the group consisting of polymethacrylic acid, poly (buthyl vinyl ether), poly (cyclohexyl methacrylate), poly (cyclohexyl vinyl ether), polyvinylidene fluoride, polydivinylbenzene, Is a polymer containing two or more kinds of repeating units to be constituted.

The second polymer block may be selected from the group consisting of polyethylene oxide, polypropylene oxide, polymethylmethacrylate, polyethylmethacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polymethylacrylate, (C1-C20 alkyl carbonate), polynitrile, polyphosphoric acid, polyoxyethylene (meth) acrylate, polyoxyethylene (meth) acrylate, May be at least one selected from the group consisting of polyphosphazines, polyolefins, polydienes, polyisoprene, polybutadiene, polychloroprene, polyurethane, polyethylene, polybutylene, polyisobutylene and polypropylene. Polymer blocks are related to the mechanical properties of block copolymers. The second polymer block is a region related to the ionic conductivity, strength, and / or ductility of the block copolymer.

The block copolymers may include i) a structural domain; And ii) a block copolymer comprising at least one selected from ion conductive domains, rubber-free domains and hard domains. Such a block copolymer is excellent in strength and flexibility and has a very excellent function of physically suppressing the growth of lithium dendrites on the surface of a lithium metal cathode. As used herein, the term " structural domain " is an area related to the mechanical properties of a block copolymer. As used herein, the term " ion conductive domain " refers to a region related to ionic conductivity of a block copolymer. &Quot; Hard domain " means that the block copolymer has hydrophobicity and crystallinity as a region contributing to exhibit high mechanical strength, So that the protective film retains the characteristics of the separator. The "rubber-free domain" provides excellent strength, ductility and elasticity of the block copolymer at the same time, and is excellent in stability to a liquid electrolyte containing a carbonate-based organic solvent.

Wherein the structural domain in the block copolymer comprises a first polymer block of a block copolymer and at least one selected from an ion conductive domain, a rubber-phase domain and a hard domain is an ion-conductive block of the block copolymer, ii) Block, and iii) a hard block. The first polymer block includes a plurality of structural repeating units, and the second polymer block includes at least one selected from a plurality of ion conductive repeating units, a plurality of rubber-like repeating units, and a plurality of olefin-based repeating units. Wherein the ion conductive block is selected from the group consisting of polyethylene oxide, polypropylene oxide, polymethylmethacrylate, polyethylmethacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polymethylacrylate, (C1-C20 alkylcarbonate), polynitrile, and poly (vinylpyrrolidone), which are known in the art, such as poly (methyl methacrylate), poly (methyl methacrylate), poly Polyphosphazines, and polyphosphazines.

In one embodiment, the rubber-like block in the block copolymer is at least one selected from the group consisting of polyisoprene, polybutadiene, polychloroprene, polyisobutylene, and polyurethane, and the hard block is selected from the group consisting of polyethylene, polybutylene, polyisobutyl And at least one selected from the group consisting of rhenylene and polypropylene.

The weight average molecular weight of the first polymer block of the block copolymer according to one embodiment is 10,000 Daltons or more, for example 10,000 to 500,000 Daltons, specifically 15,000 to 400,000 Daltons. And the weight average molecular weight of the second polymer block is 10,000 Daltons or more, for example, 10,000 to 500,000 Daltons, specifically 15,000 to 400,000 Daltons. When a block copolymer containing the first polymer block and the second polymer block having such a weight average molecular weight is used, a protective film excellent in ductility, elasticity and strength can be obtained.

The content of the first polymer block in the block copolymer is 20 to 50 parts by weight, for example, 22 to 30 parts by weight, specifically 25 to 30 parts by weight, based on 100 parts by weight of the total weight of the block copolymer. When such a first polymer block is used, a protective film excellent in mechanical properties such as strength can be obtained.

The block copolymer according to one embodiment is at least one selected from a double block copolymer (AB) and a triblock copolymer (ABA 'or BA-B'), and the blocks A and A ' The first polymer block, and the blocks B and B 'are the second polymer block.

When the polymer contained in the protective film is a block copolymer, for example, i) a first block of polystyrene and ii) a block copolymer comprising at least one second block selected from polyisoprene and polybutadiene, i) a first block of polystyrene and ii) ) A block copolymer comprising at least one second block selected from polyisoprene, polybutadiene and iii) a polystyrene third block; a block copolymer comprising i) at least one first block selected from polystyrene and polymethyl methacrylate, and ii) at least one second block selected from polyethylene and polybutylene, i) one selected from polystyrene and polymethyl methacrylate At least one second block selected from the group consisting of polyethylene and polybutylene, and iii) at least one third block selected from polystyrene and polymethyl methacrylate; i) a block copolymer comprising a first block of polystyrene and ii) a second block comprising polyethylene oxide and one reaction product selected from polyethylene glycol diacrylate and polyethylene glycol dimethacrylate; (i) a first block of polystyrene and ii) a second block comprising polyethylene oxide and one reaction product selected from polyethylene glycol diacrylate and polyethylene glycol dimethacrylate, and (iii) a block copolymer containing a third block of polystyrene coalescence; i) a block copolymer comprising a first block of polystyrene and ii) a second block comprising polyethylene oxide and one reaction product selected from trimethylolpropane triacrylate and trimethylolpropane trimethacrylate; (i) a first block comprising polystyrene and (ii) a second block comprising polyethylene oxide and one reaction product selected from trimethylolpropane triacrylate and trimethylolpropane trimethacrylate, and (iii) a second block comprising a polystyrene third block Block copolymers; (i) a first block of polystyrene and (ii) a second block comprising a reaction product of a polyhedral oligomeric silsesquioxane (POSS) with an acrylic group selected from polyethylene glycol diacrylate and polyethylene glycol dimethacrylate and polyethylene oxide I) a first block of polystyrene and ii) a second block comprising a reaction product of POSS having an acrylic group and one selected from polyethylene glycol diacrylate and polyethylene glycol dimethacrylate and polyethylene oxide, and iii) ) A block copolymer containing a third polystyrene block; (i) a first block of polystyrene and (ii) a second block comprising a reaction product of POSS having an acrylic group and one selected from trimethylolpropane triacrylate and trimethylolpropane trimethacrylate and polyethylene oxide) coalescence; Or i) a first block of polystyrene and ii) a second block comprising polyethylene oxide and the reaction product of POSS having an acrylic group and one selected from trimethylolpropane triacrylate and trimethylolpropane trimethacrylate and iii) polystyrene And a block copolymer containing a third block.

The total content of the first block and the third block in the above-mentioned block copolymer including the first block, the second block and the third block is 20 to 35 parts by weight based on 100 parts by weight of the total weight of the block copolymer, The content of the second block is from 65 to 80 parts by weight, for example, from 70 to 78 parts by weight, specifically from 72 to 70 parts by weight, based on 100 parts by weight of the block copolymer, 75 parts by weight. In the above-mentioned block copolymer, the mixing weight ratio of the first polymer block and the second polymer block is 1: 1 to 1: 9, for example, 1: 1 to 1: 7, specifically 1: 1 to 1: 4. When the mixing ratio is in the above range, the mechanical properties of the protective film are excellent and the growth of lithium dendrite is effectively suppressed without lowering the ductility and tensile elastic modulus of the protective film.

According to another embodiment, the block copolymer comprises at least one first block selected from the group consisting of polystyrene, polymethyl methacrylate and polyacrylonitrile and at least one second block selected from polyisoprene, polyethylene and polybutylene.

According to another embodiment, the block copolymer comprises at least one first block selected from polystyrene, polymethyl methacrylate, polyacrylonitrile and at least one second block among polyethylene oxide and polysiloxane.

Block copolymers include, for example, polystyrene-b-polyisoprene-polystyrene block copolymers and the like.

The weight average molecular weight of the block copolymer contained in the protective film according to one embodiment may be in the range of 10,000 to 500,000 daltons.

In a lithium metal battery according to an embodiment, the liquid electrolyte contains a lithium salt and an organic solvent. Examples of the organic solvent include a carbonate compound, a glycol compound, and a dioxolane compound. The carbonate-based compound includes ethylene carbonate, propylene carbonate, dimethyl carbonate, fluoroethylene carbonate, diethyl carbonate, or ethyl methyl carbonate. The glycine compound is selected from the group consisting of poly (ethylene glycol) dimethyl ether, tetra (ethylene glycol) dimethyl ether, tri (ethylene glycol) dimethyl ether, poly (ethylene glycol) dilaurate, poly (ethylene glycol) Glycol) diacrylate.

Examples of dioxolane-based compounds include 3-dioxolane, 4,5-diethyl-dioxolane, 4,5-dimethyl-dioxolane, 4-methyl- -1,3-dioxolane. ≪ / RTI > The organic solvent may be, for example, 2,2-dimethoxy-2-phenylacetophenone, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, tetrahydrofuran, gamma butyrolactone, , 1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether).

The organic solvent of the liquid electrolyte includes, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, fluoroethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylene glycol dimethyl ether, Diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinonitrile, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, and 1, And 1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. The polymer contained in the protective film according to one embodiment is insoluble in the above-mentioned organic solvent.

The lithium salt may be, 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, LiAlO 2, LiAlCl 4, LiCl, LiI, LiSbF 6, LiPF 3 (CF 2 CF 3) 3, LiPF 3 (CF 3) 3, and And LiB (C ₂ O ₄ ) ₂ . The content of the lithium salt in the liquid electrolyte may be, for example, 0.01 to 2.0M.

The protective film may further include at least one selected from an inorganic particle, an ionic liquid, a polymeric ionic liquid, and an oligomer.

The protective film may further include a lithium salt. The content of the lithium salt is 10 to 70 parts by weight, for example, 15 to 60 parts by weight, specifically 20 to 50 parts by weight, based on 100 parts by weight of the polymer of the protective film. The ionic conductivity of the protective film is excellent when the content of the lithium salt is in the above range.

The elongation of the protective film according to one embodiment is at least 500%, for example at least 600%, particularly 1000 to 1500% at 25 ° C. The protective film satisfying such an elongation rate is excellent in ductility and can suppress the growth of dendrite on the surface of the lithium metal, and can effectively suppress the volume change of the lithium metal cathode.

As the inorganic particles, at least one selected from SiO ₂ , cage-structured silsesquioxane, TiO ₂ , ZnO, Al ₂ O ₃ , BaTiO ₃ and metal-organic framework (MOF) have. When such an inorganic particle is further included, a protective film having improved mechanical properties can be produced. The average particle size of the inorganic particles may be 1 탆 or less, for example, 1 to 500 nm, specifically 1 to 100 nm or less. For example, the particle size of the inorganic particles may be 1 nm to 100 nm, for example, 10 nm to 100 nm, specifically 30 nm to 70 nm. When the particle size of the inorganic particles is in the above range, a protective film excellent in film forming property and excellent in mechanical properties can be produced without lowering the ion conductivity.

The silsesquioxane of the cage structure may be, for example, Polyhedral Oligomeric Silsesquioxane (POSS). There are no more than eight silicones present in such POSS, for example six or eight. The silsesquioxane having a cage structure may be a compound represented by the following formula (1).

[Chemical Formula 1]

^{_{Si k O 1 .5k (R 1}} ) a (R 2) b (R 3) c

In the above formula R ¹ , R ² , and R ³ are each independently hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C2-C30 A substituted or unsubstituted C6-C30 aryloxy 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 C4-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbon ring group, or a silicon-containing functional group.

In the above formula (1), 0 <a <20, 0 <b <20, 0 <c <20, k = a + b + c where a, b and c are in the range of 6? K?

Silsesquioxane having a cage structure may be a compound represented by the following formula (2) or a compound represented by the following formula (3).

 (2)

Wherein R _{1 to} R ₈ are independently selected from the group consisting of hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C2-C30 Substituted or unsubstituted C2-C30 alkynyl group, substituted or unsubstituted C6-C30 aryl group, substituted or unsubstituted C6-C30 aryloxy group, substituted or unsubstituted A C2-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbon ring group, or a silicon-containing functional group.

 (3)

In Formula 3, R ₁ -R ₆ are independently hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C1-C30 alkoxy group, a substituted or unsubstituted C2-C30 to each other Substituted or unsubstituted C2-C30 alkynyl group, substituted or unsubstituted C6-C30 aryl group, substituted or unsubstituted C6-C30 aryloxy group, substituted or unsubstituted A C2-C30 heteroaryl group, a substituted or unsubstituted C4-C30 carbon ring group, or a silicon-containing functional group.

According to one embodiment, R ₁ -R _{8 in} Formula 2 and R ₁ -R ₆ in Formula 3 are isobutyl groups. For example, the silsesquioxane of the cage structure may be, for example, octaisobutyl-t8-silsesquioxane.

When inorganic particles are contained in the protective film, the content of the inorganic particles is 1 to 40 parts by weight, for example 3 to 30 parts by weight, specifically 5 to 20 parts by weight, based on 100 parts by weight of the polymer. When the content of the inorganic particles is within the above range, a protective film excellent in mechanical properties and ionic conductivity can be produced.

The metal-organic skeleton structure is a porous crystalline compound in which a metal ion of group 2 to 15 or a metal ion cluster of group 2 to 15 is formed by a chemical bond with an organic ligand. The organic ligand means an organic group capable of chemical bonding such as coordination bond, ionic bond or covalent bond. For example, the organic ligand is an organic group having two or more sites capable of binding to the metal ion described above, A structure can be formed.

The Group 2 to Group 15 metal ions may be at least one selected from the group consisting of Co, Ni, Mo, W, Ru, Os, Cd, beryllium, (Ba), Sr, Fe, Mn, Cr, V, Al, Ti, Zr, Zr, (Pt), copper (Cu), zinc (Zn), magnesium (Mg), hafnium (Hf), Nb, tantalum (Ta), Re, rhodium (Rh), iridium (Ir), palladium , Ag, Sc, Y, In, Thl, Si, Ge, Sn, Pb, As, Sb) and bismuth (Bi), and the organic ligand is at least one selected from aromatic dicarboxylic acid, aromatic tricarboxylic acid, imidazole compound, tetrazole compound, 1,2,3- A sulfonic acid, an aromatic phosphoric acid, an aromatic sulfinic acid, an aromatic phosphinic acid, a bipyridine, an amino group, an imino group, an acyl group, A, pyridine group, a pyrazine group a group derived from at least one selected from a compound having at least one functional group selected ^from-imide group, a dithiocarbamic acid group (-CS ₂ H), dithio-carboxylate (-CS _2).

Examples of the aromatic dicarboxylic acid or aromatic tricarboxylic acid mentioned above include benzene dicarboxylic acid, benzenetricarboxylic acid, biphenyldicarboxylic acid and terphenyldicarboxylic acid.

The above-mentioned organic ligands may specifically be a group derived from a compound represented by the following general formula (4).

[Chemical Formula 4]

The metal-organic skeleton structure can be, 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 = 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 }.

The ionic liquid refers to a salt in a liquid state at room temperature or a room-temperature molten salt having a melting point below room temperature and consisting solely of ions. The ionic liquid may be selected from the group consisting of i) an ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, Triazolium series and mixtures thereof and ii) at least one cation selected from the group consisting of 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 ^- .

The inorganic particles may have various shapes. The inorganic particles may be, for example, spherical, elliptical, cubic, cubical, tetrahedral, pyramidal, octahedral, cylindrical, A pillar-like shape, a conical shape, a columnar shape, a tubular shape, a helical shape, a funnel shape, a dendrite shape, And may have various common regular shapes or irregular shapes.

The ionic liquid may include, for example, N-methyl-N-propylpyrrolidiumbis (trifluoromethylsulfonyl) imide (N-methyl-N-propylpyrrolidinium bis Butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, (Trifluoromethylsulfonyl) imide. &Lt; / RTI &gt; The content of the ionic liquid is 5 to 40 parts by weight, for example 7 to 30 parts by weight, specifically 10 to 20 parts by weight, based on 100 parts by weight of the polymer contained in the protective film. When the content of the ionic liquid is within the above range, a protective film excellent in ionic conductivity and mechanical properties can be obtained.

(IL / Li) of the ionic liquid (IL) / lithium ion (Li) is 0.1 to 2.0, for example, 0.2 to 1.8, . The protective film having such a molar ratio is excellent in lithium ion mobility and ionic conductivity as well as excellent in mechanical properties and can effectively suppress the growth of lithium dendrite on the surface of the lithium metal cathode.

The polymeric ionic liquid may be obtained by polymerizing an ionic liquid monomer, or may be a polymeric compound. Such a polymeric ionic liquid has a high solubility in an organic solvent and has an advantage that ionic conductivity can be further improved when added to an electrolyte.

In the case of obtaining a polymeric ionic liquid by polymerizing the above-mentioned ionic liquid monomer, the polymeric reaction product is washed and dried, and then anion substitution reaction is carried out to obtain an appropriate anion capable of imparting solubility to the organic solvent do.

The polymeric ionic liquid according to one embodiment may be selected from the group consisting of i) ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, At least one cation selected from the group consisting of 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 -, 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 - &Lt; RTI ID = 0.0 &gt; and / or &lt; / RTI &gt;

According to another embodiment, the ionic liquid monomer may have a polymerizable functional group such as a vinyl group, an allyl group, an acrylate group, a methacrylate group and the like, and may be an ammonium group, a pyrrolidinium group, a pyridinium group, a pyrimidinium group, At least one cation selected from imidazolium-based, piperidinium-based, 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 formula (5) or (6).

[Chemical Formula 5]

[Chemical Formula 6]

Examples of the above polymeric ionic liquid include a compound represented by the following formula (7) or a compound represented by the following formula (8).

(7)

In Formula 7, R ₁ and R ₃ independently represent hydrogen, a substituted or unsubstituted C1-C30 alkyl group, a substituted or unsubstituted C2-C30 alkenyl group, a substituted or unsubstituted C2-C30 A substituted or unsubstituted C6-C30 aryl group, a substituted or unsubstituted C2-C30 heteroaryl group, and a substituted or unsubstituted C4-C30 carbon ring group. In Formula 10, R ₂ represents a chemical bond or represents a C1-C3 alkylene group, a C6-C30 arylene group, a C2-C30 heteroarylene group, or a C4-C30 carbon ring group,

X ^- represents an anion of the ionic liquid,

and n is 500 to 2800.

[Chemical Formula 8]

In the formula 8 ^Y-X is in formula (7) ^- is defined in the same manner as,

and n is 500 to 2800.

Y ^- in formula (8) is, for example, bis (trifluoromethylsulfonyl) imide (TFSI), bis (fluorosulfonyl) imide, BF ₄ or CF ₃ SO ₃ .

Polymeric ionic liquids include, for example, poly (1-vinyl-3-alkylimidazolium) wherein alkyl is a C1-C20 alkyl group, poly - CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , and a cation selected from poly (1-methacryloyloxy-3-alkylimidazolium) ^{_{-, (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 ^- .

The compound represented by the formula (8) includes polydiallyldimethylammonium bis (trifluoromethylsulfonyl) imide.

According to another embodiment, the polymeric ionic liquid may comprise 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 glyme. Examples of the glyme include 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, for example, 250 to 500. And the thermally stable ionic liquid is as defined in the above ionic liquid.

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, and the oligomer content is 5 to 50 parts by weight, for example 3 to 30 parts by weight, specifically 5 to 25 parts by weight, based on 100 parts by weight of the polymer. When the oligomer is added in this manner, the film forming property, the mechanical property, and the ionic conductivity of the protective film are superior.

The ionic conductivity of the protective film may be 1 X 10 ^-4 S / cm or more, for example, 5 × 10 ^-4 S / cm or more, specifically 1 × 10 ^-3 S / cm or more at about 25 ° C. The tensile modulus of the protective film is at least 10 MPa, for example, 10 to 80 MPa, specifically 10 to 50 MPa at about 25 캜. And the elongation of the protective film is at least 500%, for example at least 600%, specifically at least 1200% or 1300% at about 25 ° C. The protective film can secure both mechanical properties such as ductility and elasticity required for battery performance and ionic conductivity at 25 占 폚. When the elongation percentage of the protective film is in the above range, the function of suppressing the volume change of the lithium metal cathode is excellent. If the elongation percentage of the protective film is smaller than the above range, the portion attacked due to the dendrites formed on the surface of the lithium metal cathode is likely to be broken to form a short. The protective film according to one embodiment has tensile elastic modulus and ductility as described above, thereby suppressing a change in the cathode volume and effectively suppressing dendrite growth.

The protective film according to one embodiment has a tensile strength at 25 DEG C of 2.0

MPa or more. And the interface resistance between the lithium metal and the protective film derived from the Nyquist plot obtained from the impedance measurement is reduced by 10% or more at 25 캜 as compared with the bare lithium metal. When the protective film according to one embodiment is used, the interfacial resistance is reduced as compared with the case where lithium metal alone is used, so that the interfacial property is excellent. The protective film has an oxidation current or a reduction current of 0.05 mA / cm ² or less in a voltage range of 0.0 Volts (V) to 6.0 V relative to lithium metal.

In a lithium metal battery according to an embodiment, the lithium electrodeposition density at the surface of the lithium metal cathode is 0.2 to 0.4 grams per cubic centimeter (g / cc), for example, 0.26 to 0.32 g / cc.

FIGS. 1 and 2 show the structure of a lithium metal battery according to an embodiment.

Referring to FIG. 1, a protective film 11 according to an embodiment is formed on a lithium metal cathode 10, and a liquid electrolyte 12 is disposed between the protective film 11 and the positive electrode 13. (14) selected from a metal salt containing a group 1 or group 2 element contained in the protective film (11) and a nitrogen-containing additive, and this material has insoluble characteristics in the organic solvent of the liquid electrolyte (12). One or more (14) selected from a metal salt containing a Group 1 or 2 element and a nitrogen containing additive may be present in the region adjacent to the lithium metal cathode 10 in the protective film 11 as shown in FIG. According to another embodiment, at least one (14) selected from a metal salt containing a group I or II element and a nitrogen-containing additive is distributed throughout the protective film and the content thereof is increased to a region close to the lithium metal cathode 10 . 1, at least one (14) selected from a metal salt containing a group 1 or group 2 element and a nitrogen-containing additive is present at a position adjacent to the lithium metal cathode 10, It is not.

Referring to FIG. 2, a protective film 21 is formed on the lithium metal cathode 20. Layer structure in which a liquid electrolyte 22a and a solid electrolyte 22b are sequentially stacked on the protective film 21. The liquid electrolyte 22a may be disposed adjacent to the protective film 21 as shown in FIG. 2, but the order of stacking the liquid electrolyte and the solid electrolyte may be changed. An anode 23 is disposed above the solid electrolyte 22b. The electrolyte 22 is composed of a liquid electrolyte 22a and a solid electrolyte 22b.

A gel electrolyte may be used instead of the solid electrolyte 22b in Fig.

The lithium metal battery according to an embodiment may further include a separator. As the separator, polyethylene, polypropylene, polyvinylidene fluoride or a multilayer film of two or more thereof may be used. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene three layer separator, a polypropylene / polyethylene / A three-layer separator, or the like can be used. The separator may further include an electrolyte containing a lithium salt and an organic solvent.

The positive electrodes 13 and 23 in FIGS. 1 and 2 may be porous positive electrodes. The porous anode includes pores which contain pores or which do not exclude the formation of an anode intentionally so that the liquid electrolyte can be permeated into the inside of the anode by capillary phenomenon or the like.

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

According to another embodiment, the anode may further comprise a liquid electrolyte, a gel electrolyte, or a solid electrolyte. The liquid electrolyte, the gel electrolyte, and the solid electrolyte can be used as an electrolyte of a lithium metal battery in the related art, and can be any material that does not deteriorate the cathode active material by reacting with the cathode active material during charging and discharging.

The protective film according to one embodiment is suitable as a high-voltage lithium metal battery protective film.

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

Hereinafter, a method of manufacturing a lithium metal battery according to an embodiment will be described.

A composition for forming a protective film is obtained by mixing at least one selected from a metal salt containing a high molecular substance, a Group 1 or Group 2 element and a nitrogen containing additive and an organic solvent. Next, a composition for forming a protective film is applied on the upper portion of the lithium metal cathode and dried to form a protective film on the lithium metal surface. Here, drying can be carried out, for example, at 25 to 60 占 폚.

The organic solvent may be any solvent conventionally used in the art. Examples of the solvent include tetrahydrofuran, N-methylpyrrolidone, acetonitrile, benzonitrile, 2-methyltetrahydrofuran, gamma -butyrolactone, dioxolane, 4-methyldioxolane, N, Dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, Dimethyl ether, and the like. The content of the organic solvent is, for example, 100 to 4,000 parts by weight, for example, 500 to 2,000 parts by weight based on 100 parts by weight of the polymer.

The composition for forming a protective film may further include at least one selected from inorganic particles, an ionic liquid, a polymeric ionic liquid, and an oligomer.

The above-mentioned coating method of the composition for forming a protective film can be used as long as it is a method which can be generally used for forming a protective film. For example, methods such as spin coating, roll coating, curtain coating, extrusion, casting, screen printing, inkjet printing, doctor blading and the like can be used.

The protective film prepared according to the above process may be electrochemically stable with respect to lithium at a voltage range of 0 to 6.0V, for example, 2.0 to 5.0V, specifically 4.0V to 5.0V. The protective film according to one embodiment can be applied to an electrochemical device operated at a high voltage by having an electrochemically stable wide voltage window.

The protective film may have a current density of 0.05 mA / cm ² or less, for example, 0.001 to 0.02 mA / cm ² , particularly 0.001 to 0.01 mA / cm ² , due to side reactions other than the attachment / . For example, the protective film may have a current density of 0.05 mA / cm ² or less, for example, 0.001 to 0.02 mA / cm ² mA / cm ² , for example, 0.001 to 0.04 mA / cm &lt; ² &gt;, specifically 0.001 to 0.02 mA / cm &lt; ² &gt;.

The lithium metal battery according to one embodiment may be a mixed electrolyte type including at least one selected from a solid electrolyte, a gel electrolyte, and a polymer ionic liquid in addition to the liquid electrolyte. The lithium metal battery may further include a separator. As described above, the conductivity and the mechanical properties of the protective film can be further improved by further including at least one selected from a solid electrolyte and a gel electrolyte.

The gel electrolyte is an electrolyte having a gel form, and any of those known in the art can be used. The gel electrolyte may contain, for example, a polymer and a polymeric ionic liquid. The polymer may be, for example, a solid graft (block) copolymer electrolyte.

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

Examples of the organic solid electrolyte include a polymer including a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and an ionic dissociation group Can be used.

The inorganic solid _{electrolyte, 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, Eu, Gd, Tb, Dy, Ho, Er, Ga) _x (Ge _1-y Ti _y ) _{2 -x} (PO ₄ ) ₃ (X? 0.8, 0? Y? 1.0, M is Nd, Tm or Yb), Li _{1 + x + y} Q _x Ti _{2 - x} Si _y P _{3 - y} O ₁₂ (0 &lt; x? 0.4, 0 &lt; 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).

The lithium metal cathode is a lithium metal thin film electrode or a lithium metal alloy electrode.

Lithium metal alloys include lithium, lithium-alloyable metals / metalloids, alloys thereof,

Oxide. &Lt; / RTI &gt; For example, the metal / semi-metal, alloy or oxide thereof capable of being alloyed with lithium may be at least one selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, Sb, Si- (Wherein Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 to Group 16 elements, transition metals, rare earth elements, or combinations thereof) , And Sn is not), and the like. The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Se, Te, Po, or a combination thereof.

The positive electrode active material for producing the positive electrode 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. And any cathode active material available in the art may be used.

For example, Li _a A _{1 - b} B _b D ₂ , where 0.90? A? 1.8, and 0? B? 0.5; Li _a E _{1 - b} B _b O _{2 - c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? _C ? 0.05; LiE _{2 - b} B _b O _{4 - c} D _{c where} 0? B? 0.5, 0 _{? C?} 0.05; Li _a Ni _{1 -b- c} Co _b B _c D _? Wherein, in the formula, 0.90 _{? A?} 1.8, 0 _? B _? 0.5, 0 _? C _? 0.05, 0? Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F _? Wherein, in the formula, 0.90? A? 1.8, 0 _? B _? 0.5, 0 _? C _? 0.05, 0 <? Li _a Ni _{1 -b- c} Mn _b B _c D _? Wherein, in the formula, 0.90 _{? A?} 1.8, 0 _? B _? 0.5, 0 _? C _? 0.05, 0? Li _a Ni _{1 -b- c} Mn _b B _c O _{2 - ?} F _? Wherein, in the formula, 0.90? A? 1.8, 0 _? B _? 0.5, 0 _? C _? 0.05, 0? Li _a Ni _b E _c G _d O ₂ wherein 0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, and 0.001? D? 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, 0? D? 0.5, and 0.001? E? 0.1. Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8, and 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, and 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} ); _{(0≤f≤2) Li (3-f} ) Fe 2 (PO 4) 3; A compound represented by any one of the formulas of LiFePO ₄ can 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 combinations 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.

The cathode active material may be, for example, a compound represented by the following formula (9), a compound represented by the following formula (10) or a compound represented by the following formula (11).

[Chemical Formula 9]

Li _a Ni _b Co _c Mn _d O ₂

In the above formula (9), 0.90? A? 1.8, 0? B? 0.9, 0? C? 0.5, and 0? D?

[Chemical formula 10]

Li ₂ MnO ₃

(11)

LiMO ₂

In the above formula (11), M is Mn, Fe, Co, or Ni.

The anode 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 further be added to the cathode active material composition.

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

The collector may be a film obtained by plasma spraying or arc spraying of nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloy or stainless steel or carbonaceous material, activated carbon fiber, nickel, aluminum, zinc, copper, A conductive film obtained by dispersing tin, lead, an alloy thereof, or a conductive material in a resin or rubber such as a styrene-ethylene-butylene-styrene copolymer (SEBS) is used. The collector may be made of aluminum, nickel or stainless steel, for example. Aluminum is suitable as a current collector since it is easy to manufacture as a thin film and is inexpensive. The shape of the current collector is not limited and may be a flat plate shape, a mesh shape, a net shape, a punch shape, an embossed shape, or a combination thereof, for example, a mesh shape flat plate. For example, the current collector may have a non-planarized surface formed by etching.

The binder is added to the binder in an amount of 1 to 50 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material. Non-limiting examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Ethylene, propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluorine rubber, various copolymers and the like. The content thereof is 2 to 5 parts by weight based on 100 parts by weight of the total weight of the cathode active material. When the content of the binder is in 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 electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The conductive agent is used in an amount of 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 cathode active material. When the content of the conductive agent is in the above range, the conductivity of the anode finally obtained is excellent.

As a non-limiting example of the solvent, N-methylpyrrolidone or the like is used.

The solvent is used in an amount of 100 to 2000 parts by weight based on 100 parts by weight of the cathode active material. When the content of the solvent is within the above range, the work for forming the active material layer is easy.

The lithium metal battery according to one embodiment can be used not only for a battery cell used as a power source of a small device because of its excellent capacity and life characteristics, but also as a middle- or large-sized battery pack including a plurality of battery cells used as a power source for a medium- The battery module may also be used as a unit battery. The lithium metal battery according to one embodiment has high voltage, capacity and energy density and is widely used in the fields of cell phones, notebook computers, batteries for power generation facilities such as wind power and solar power, electric vehicles, uninterruptible power supply devices, .

Examples of the medium and large devices include an electric vehicle (EV) including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) E-bike, an electric motorcycle electric power tool electric power storage device including an electric scooter (E-scooter), but the present invention is not limited thereto.

According to another aspect, there is provided a method for forming a protective film, comprising: i) mixing a polymer and at least one selected from the group consisting of a metal salt containing a Group 1 or 2 element and a nitrogen containing additive; Supplying the composition for forming a protective film to a lithium metal anode; And drying the resultant to form a protective film. The method for protecting a lithium metal anode of a lithium metal battery according to an embodiment of the present invention is provided.

According to another aspect, there is provided a protective film produced according to the above-described method.

As used herein, alkyl refers to fully saturated branched or unbranched (or straight chain or linear) hydrocarbons.

Non-limiting examples of "alkyl" include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n- pentyl, isopentyl, neopentyl, isoamyl, -Methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl and the like.

"Alkyl" at least one hydrogen atom of an alkyl group of a halogen atom, halogen-substituted C1-C20 (for _{example: CCF 3, CHCF 2, CH} 2 F, CCl 3 , etc.), an alkoxy of C1-C20 alkoxy, C2-C20 of A carboxyl group or a salt thereof, a sulfonyl group, a sulfamoyl group, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, or a C1-C4 alkyl group, C20 alkyl group, C2-C20 alkenyl group, C2-C20 alkynyl group, C1-C20 heteroalkyl group, C6-C20 aryl group, C6-C20 arylalkyl group, C6-C20 heteroaryl group, C7- An arylalkyl group, a C6-C20 heteroaryloxy group, a C6-C20 heteroaryloxyalkyl group or a C7-C20 heteroarylalkyl group.

The term &quot; halogen atom &quot; includes fluorine, bromine, chlorine, iodine and the like.

&Quot; Alkenyl &quot; refers to branched or unbranched hydrocarbons 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 at least one hydrogen atom of the alkenyl may be substituted with the same substituent as the alkyl group described above .

&Quot; Alkynyl &quot; refers to branched or unbranched hydrocarbons having at least one carbon-carbon triple bond. Non-limiting examples of the "alkynyl" include ethynyl, butynyl, isobutynyl, propynyl, and the like.

At least one hydrogen atom of &quot; alkynyl &quot; may be substituted with the same substituent as in the alkyl group described above.

&Quot; Aryl &quot; also includes a group in which the aromatic ring is fused to one or more carbon rings. Non-limiting examples of &quot; aryl &quot; include phenyl, naphthyl, tetrahydronaphthyl, and the like.

Also, at least one hydrogen atom in the &quot; aryl &quot; group may be substituted with the same substituent as in the case of the above-mentioned alkyl group.

&Quot; Heteroaryl &quot; means monocyclic or bicyclic organic compounds containing one or more heteroatoms selected from N, O, P, or S and the remaining ring atoms carbon. The heteroaryl group may contain, for example, from 1 to 5 hetero atoms, 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, , 5-oxadiazolyl, 1,3,4-oxadiazolyl group, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, Thiadiazolyl, isothiazol-3-yl, isothiazol-4-yl, isothiazol-5-yl, oxazol- Yl, isoxazol-3-yl, 1,2,4-triazol-5-yl, Yl, pyridyl-2-yl, pyridyl-3-yl, pyrazin-2-yl , Pyrazin-4-yl, pyrazin-5-yl, pyrimidin-2-yl, pyrimidin-4-yl or pyrimidin-5-yl.

The term &quot; heteroaryl &quot; includes those where the heteroaromatic ring is fused to one or more aryl, cycloaliphatic, or heterocycle.

The &quot; carbon ring &quot; group 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 are bornyl, decahydronaphthyl, bicyclo [2.1.1] hexyl, bicyclo [2.2.1] heptyl, bicyclo [2.2.1] heptenyl, or bicyclo [2.2.2] octyl. Examples of tricyclic hydrocarbons include adamantyl and the like.

  &Quot; Heterocycle &quot; is a ring containing at least one heteroatom and may contain 5 to 20, such as 5 to 10, carbon atoms. Wherein the heteroatom is one selected from sulfur, nitrogen, oxygen and boron.

For example, the term "substituted C1-C30 alkyl" refers to a C1-C30 alkyl group substituted with a C6-C30 aryl group and the total number of carbon atoms in the substituted alkyl group is C7-C60.

Alkoxy, aryloxy, heteroaryloxy means alkyl, aryl and heteroaryl, respectively, attached to an oxygen atom herein.

Will be explained in more detail through the following examples and comparative examples. However, the embodiments are for illustrative purposes only and are not intended to be limiting.

Example  1: Manufacture of Lithium Metal Battery

A polystyrene-b-polyisoprene-b-polystyrene block copolymer (available from Polymer Source) was added to anhydrous tetrahydrofuran to obtain a mixture containing 5% by weight of a block copolymer. The weight ratio of polystyrene block, polyisoprene block and polystyrene block in the block copolymer was about 11:78:11 by weight, and the weight average molecular weight of the block copolymer was about 100,000 Daltons.

5% by weight of Li ₃ N, 5% by weight of CsTFSI and 200% by weight of Al ₂ O ₃ (average particle diameter: about 10 nm) were added to the block copolymer-containing mixture to obtain a composition for forming a protective film. Here, the content of Li3N was about 5 parts by weight based on 100 parts by weight of the block copolymer, and the content of CsTFSI was about 5 parts by weight based on 100 parts by weight of the block copolymer.

The composition for forming a protective film was coated on the top of a lithium metal thin film (thickness: about 20 mu m) with a doctor blade to a thickness of about 3 mu m. The coated product was dried at about 25 캜 to prepare a lithium metal anode having a protective film (thickness: about 3 탆) formed on the lithium metal cathode.

Separately, a positive electrode composition was obtained by mixing LiCoO ₂ , Super-P (Timcal Ltd.), polyvinylidene fluoride (PVdF) and N-methylpyrrolidone. In the positive electrode composition, the mixing weight ratio of LiCoO ₂ , the conductive agent, and polyvinylidene fluoride (PVDF) was 97: 1.5: 1.5.

The above cathode composition was coated on an aluminum foil (thickness: about 15 탆), dried at 25 캜, and dried, and dried at about 110 캜 under vacuum to prepare a cathode. The discharge capacity per unit area of the anode was about 3.5 mAh / cm ² .

A lithium metal battery (coin cell) was produced through a polyethylene separator (porosity: about 48%) between the positive electrode obtained by the above procedure and a lithium metal negative electrode (thickness: about 20 μm). Here, a liquid electrolyte was added between the positive electrode and the lithium metal negative electrode. As the liquid electrolyte, 1,2-dimethoxyethane (DME) in a 2: 8: volume ratio and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (1,1,2 , 2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE)) was used as the electrolytic solution in which 1.0 M LiN (SO ₂ F) ₂ (hereinafter referred to as LiFSI) was dissolved.

Example  2: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 1 except that LiNO ₃ was used instead of Li ₃ N in the preparation of the protective film forming composition.

Example  3: Manufacture of lithium metal battery

The procedure of Example 1 was repeated except that the content of Li ₃ N and CsTFSI was 0.05 part by weight and 0.05 part by weight based on 100 parts by weight of the block copolymer, respectively, to prepare a lithium metal battery .

Example  4: Manufacture of lithium metal battery

Except that the content of Li ₃ N and CsTFSI was 50 parts by weight and 50 parts by weight, respectively, based on 100 parts by weight of the block copolymer in the preparation of the protective film forming composition, .

Example  5: Manufacture of lithium metal battery

Except that the contents of LiNO ₃ and CsTFSI were 0.05 part by weight and 0.05 part by weight based on 100 parts by weight of the block copolymer, respectively, in the preparation of the composition for forming a protective film, Respectively.

Example  6: Manufacture of lithium metal battery

A lithium metal battery was prepared in the same manner as in Example 1 except that the amounts of LiNO ₃ and CsTFSI were 50 parts by weight and 50 parts by weight, respectively, based on 100 parts by weight of the block copolymer .

Example  7: Manufacture of lithium metal battery

A lithium metal battery was prepared in the same manner as in Example 1, except that the content of CsTFSI was increased in the preparation of the protective film forming composition to change the mixing weight ratio of Li ₃ N and CsTFSI to 1: 2.

Example  8: Manufacture of Lithium Metal Battery

A lithium metal battery was produced in the same manner as in Example 2, except that the mixing weight ratio of LiNO ₃ and CsTFSI was changed to 1: 2 in the preparation of the protective film forming composition.

Example  9-10: Manufacture of Lithium Metal Battery

A lithium metal battery was produced in the same manner as in Example 1 except that ethyl nitrate and nitromethane were used instead of Li ₃ N in the preparation of the protective film forming composition.

Example  11: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 1, except that Li ₃ N was not added in the preparation of the protective film forming composition.

Example  12: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 1, except that CsTFSI was not added and LiNO ₃ was used instead of Li ₃ N in the preparation of the protective film forming composition.

Example  13: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 1, except that polyvinyl alcohol was used in place of the polystyrene-b-polyisoprene-b-polystyrene block copolymer in the preparation of the protective film forming composition.

Example  14: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 2, except that SiO ₂ was used instead of Al ₂ O _{3 in the} preparation of the protective film forming composition.

Example  15: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 1, except that pyridine N-oxide was used instead of Li ₃ N in the preparation of the protective film forming composition.

Example  16: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 2, except that NaTFSI was used instead of CsTFSI in the preparation of the protective film forming composition.

Example  17: Manufacture of lithium metal battery

A lithium metal battery was produced in the same manner as in Example 2 except that Mg (TFSI) ₂ was used instead of CsTFSI in the preparation of the protective film forming composition.

Comparative Example  1: Manufacture of Lithium Metal Battery

LiCoO ₂ , Super-P (Timcal Ltd.), polyvinylidene fluoride (PVdF) and N-methyl pyrrolidone were mixed to obtain a positive electrode composition. The mixing ratio by weight of LiCoO ₂ , the conductive agent and PVDF in the positive electrode composition was 97: 1.5: 1.5.

The above cathode composition was coated on an aluminum foil (thickness: about 15 탆), dried at 25 캜, and dried, and dried at about 110 캜 under vacuum to prepare a cathode.

Using a polypropylene separator (thickness: 12 mu m, porosity: 48%) as a separator as a separator between the positive electrode and the lithium metal thin film (thickness: about 20 mu m) Respectively. As the liquid electrolyte, a mixed solvent of 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a volume ratio of 2: 8 1M LiFSI dissolved therein was used.

Comparative Example  2: Manufacture of lithium metal battery

20 mol of polyethylene oxide, 1 mol of lithium bistrifluoromethylsulfonylimide (LiTFSI) and 1 mol of CsTFSI were mixed to prepare a polymer electrolyte (thickness: 200 m).

The polymer electrolyte was laminated on a lithium metal thin film (thickness: about 20 mu m) to prepare a lithium metal negative electrode.

Separately, a positive electrode composition was obtained by mixing LiCoO ₂ , Super-P (Timcal Ltd.), polyvinylidene fluoride (PVdF) and N-methylpyrrolidone. The mixing ratio by weight of LiCoO ₂ , the conductive agent and PVDF in the positive electrode composition was 97: 1.5: 1.5.

The above cathode composition was coated on an aluminum foil (thickness: about 15 탆), dried at 25 캜, and dried, and dried at about 110 캜 under vacuum to prepare a cathode.

A lithium metal battery (coin cell) was produced through a polyethylene / polypropylene separator between the positive electrode and the lithium metal negative electrode obtained in accordance with the above procedure. Here, a liquid electrolyte was added between the positive electrode and the lithium metal negative electrode. As the liquid electrolyte, a mixture of 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a 2: 8 volume ratio An electrolytic solution in which 1 M LiFSI was dissolved in a solvent was used.

When the lithium metal battery prepared in Comparative Example 2 was charged and discharged, the effect of suppressing the formation of lithium dendrite was insignificant, and the interface resistance between the protective film and the lithium metal cathode surface was increased. And the lithium ion mobility was so small that the cell capacity was not realized under the evaluation example conditions.

Comparative Example  3: Manufacture of lithium metal battery

An electrolyte solution obtained by adding Li ₃ N and CsTFSI to a liquid electrolyte and adding a lithium salt in which a 1.3 M LiPF ₆ solution was dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a 2: 6: 2 volume ratio as a liquid electrolyte , A lithium metal battery was produced in the same manner as in Comparative Example 1. &lt; tb &gt;&lt; TABLE &gt; Here, the content of Li ₃ N and CsTFSI was about 5 parts by weight based on 100 parts by weight of the total weight of the liquid electrolyte.

When Li ₃ N and CsTFSI were added to the liquid electrolyte according to Comparative Example 3, Li ₃ N and CsTFSI were not dissolved well in the carbonate-based organic solvent of the liquid electrolyte. As a result, the lithium metal battery prepared in accordance with Comparative Example 3 was not even properly initialized and it was impossible to obtain a life graph.

Comparative Example  4: Manufacture of lithium metal battery

A polystyrene-b-polyisoprene-b-polystyrene block copolymer (available from Polymer Source) was added to anhydrous tetrahydrofuran to obtain a mixture containing 5% by weight of a block copolymer. The weight ratio of polystyrene block, polyisoprene block and polystyrene block in the block copolymer was about 11:78:11 by weight, and the weight average molecular weight of the block copolymer was about 100,000 Daltons.

200 parts by weight of Al ₂ O ₃ (average particle diameter: about 10 nm) was added to the block copolymer-containing mixture to coat the top of the lithium metal thin film (thickness: about 20 μm) with a doctor blade and dried at about 25 ° C., A lithium metal anode having a protective film (thickness: about 3 m) formed on the thin film was prepared.

Separately, a positive electrode composition was obtained by mixing LiCoO ₂ , Super-P (Timcal Ltd.), polyvinylidene fluoride (PVdF) and N-methylpyrrolidone. The mixing ratio by weight of LiCoO ₂ , the conductive agent and PVDF in the positive electrode composition was 97: 1.5: 1.5. The above cathode composition was coated on an aluminum foil (thickness: about 15 탆), dried at 25 캜, and dried, and dried at about 110 캜 under vacuum to prepare a cathode. The discharge capacity per unit area of the anode was about 3.5 mAh / cm ² .

A lithium metal battery was prepared through a polyethylene separator (thickness: 12 μm, porosity: 48%) between the anode and the lithium metal cathode obtained in the above procedure. Here, a liquid electrolyte was added between the positive electrode and the negative electrode. As the liquid electrolyte, a mixed solvent of 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a volume ratio of 2: 8 An electrolyte solution in which 1 M LiFSI was dissolved was used.

Evaluation example  1: Scanning electron microscope

The lithium metal battery prepared in Example 2 and Comparative Example 1 was subjected to constant current charging until the voltage reached a voltage of 4.40 Volts (V) (vs. Li) at a current of 0.1 C rate at 25 DEG C, Were analyzed using a scanning electron microscope (SEM).

The results of the above-described scanning electron microscopic analysis are shown in FIGS. 3A and 3B. FIG. 3A shows a lithium metal anode surface in a lithium metal battery manufactured according to Example 2, and FIG. 3B shows a lithium metal anode surface in a lithium metal battery manufactured according to Comparative Example 1. FIG.

As a result, it can be seen that the lithium metal battery produced according to Example 2 has a reduced lithium dendrite formation on the surface of the lithium metal as compared with the lithium metal battery of Comparative Example 1. [

The lithium metal battery prepared in Example 2 and Comparative Example 1 was subjected to constant current charging at a current of 0.1 C rate (0.38 mA / cm ² ) at 25 ° C. until the voltage reached 4.40 V (vs. Li) Followed by a cut-off at a current of 0.05 C rate while maintaining 4.40 V in the constant voltage mode. After one charge, the cross-sectional state of the surface of the lithium metal cathode was analyzed by SEM.

The results of the analysis are shown in Figs. 4A and 4B. FIG. 4A is a cross-sectional view of a lithium metal cathode in a lithium metal battery manufactured according to Example 2, and FIG. 4B is a cross-section of a lithium metal cathode in a lithium metal battery manufactured according to Comparative Example 1. FIG.

In the lithium metal battery manufactured according to Comparative Example 1, the thickness of the lithium metal cathode after charging was about 58.9 μm, whereas the thickness of the lithium metal cathode after charging in the lithium metal battery manufactured according to Example 2 was about 29.1 ㎛. Thus, the volume change of the lithium metal battery in the lithium-polymer battery of Example 2 was smaller than that of the lithium metal battery of Comparative Example 1 during charging and discharging.

Evaluation example  2: Lithium electrodeposition density

Lithium metal batteries prepared in accordance with Examples 2, 11, 12, 16 and 17 and Comparative Examples 1 and 4 were subjected to a voltage of 4.40 V (vs. Li (Li)) at a current of 0.1 C rate (0.38 mA / cm ² ) ), And then cut off at a current of 0.05 C rate while maintaining 4.40 V in the constant voltage mode. After one charge, the electrodeposited density on the surface of the lithium metal cathode was examined.

The electrodeposited density evaluation results are shown in Table 1 below.

division Lithium electrodeposition density (g / cc) Example 2 0.31-0.32 Example 11 0.27-0.30 Example 12 0.26-0.28 Example 16 0.26-0.27 Example 17 0.27-0.29 Comparative Example 1 0.18-0.19 Comparative Example 4 0.24-0.25

Referring to Table 1, the electrodeposited density of the lithium metal battery produced according to Examples 2, 11, 12, 16, and 17 was increased as compared with the batteries of Comparative Examples 1 and 4. From these results, it was found that the lithium metal batteries produced according to Examples 2, 11, 12, 16, and 17 were superior to lithium manganese dioxide batteries of Comparative Examples 1 and 4 in the lithium dendrite inhibiting function.

Evaluation example  3: Impedance measurement

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

A Nyguist plot of the impedance measurement results when the elapsed time after the manufacture of the lithium metal battery according to Example 2 and Comparative Example 1 was 24 hours is shown in FIG. In Fig. 5, the interface resistance of the electrode is determined by the position and size of the semicircle. The difference between the left x-axis section and the right x-axis section of the semicircle represents the interface resistance at the electrode.

As shown in FIG. 5, it was found that the lithium metal battery manufactured according to Example 2 had a slight decrease in the interfacial resistance as compared with the interfacial resistance of the lithium metal battery manufactured according to Comparative Example 1.

Evaluation example  4: Charging and discharging  Characteristics (discharge capacity)

1) Examples 1, 14 and 15 and Comparative Examples 1 and 4

Lithium metal batteries prepared according to Examples 1, 14 and 15 and lithium metal batteries prepared according to Comparative Examples 1 and 4 were subjected to a voltage of 4.40 V vs. Li), and then cut off at a current of 0.05 C rate while maintaining 4.40 V in constant voltage mode. Then, at the time of discharging, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) (Mars phase, 1 ^st cycle). The charging and discharging process was performed two more times to complete the conversion process.

The lithium metal cell having undergone the above conversion step was charged at a constant current of 0.7 C at a room temperature (25 캜) to a voltage range of 4.4 V relative to lithium metal, and then reached a cut-off voltage of 3.0 V at 0.5C A constant current discharge was performed at a rate of 0.5. The charging / discharging process was repeated 100 times by performing the charging / discharging process described above. The capacity retention rate is calculated from the following equation (1).

[Formula 1]

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

The charge / discharge characteristics of the lithium metal battery manufactured according to Example 1 and the lithium metal battery prepared according to Comparative Example 1 and Comparative Example 4 were evaluated as follows. The discharge capacity change and the Coulomb's efficiency were 6 and 7, respectively.

6 and 7, it was found that the capacity maintenance ratio of the lithium metal battery manufactured according to Example 1 was improved as compared with the lithium metal battery prepared according to Comparative Example 1 and Comparative Example 4. [

The lithium metal batteries prepared according to Examples 14 and 15 were subjected to the same procedures as the capacity maintenance ratios of the lithium metal batteries prepared according to Example 1 and the lithium metal batteries prepared according to Comparative Examples 1 and 4, The retention rate was evaluated.

As a result of the evaluation, the lithium metal battery prepared in accordance with Examples 14 and 15 exhibited almost the same level as the lithium metal battery prepared according to Example 1. [

Evaluation example  5: Tensile modulus  And Elongation

Tetrahydrofuran (THF) was slowly evaporated in an argon glove box over about 24 hours at about 25 DEG C in the result of casting and casting the composition for forming a protective film made according to Example 1 above at 25 DEG C And dried for 24 hours to prepare a film-like protective film. At this time, the thickness of the protective film was about 50 탆.

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 deformation of the protective film against stress was measured at a rate of 5 mm per minute at 25 ^° C and a relative humidity of about 30%. The measurement results are shown in Fig. The tensile modulus was obtained from the slope of the stress-strain curve and the elongation was obtained from the strain value.

As a result of the evaluation, the protective film produced according to Example 1 had a tensile modulus and an elongation characteristic

Was superior. Therefore, by using the protective film prepared according to Example 1 having such characteristics, the volume change of the lithium metal anode and the growth of lithium dendrite can be effectively suppressed.

Evaluation example  6: Charging and discharging  characteristic( Rate  Performance)

1) Example 2 and Comparative Example 1

The lithium metal batteries prepared in Example 2 and Comparative Example 1 were subjected to constant current charging at a current of 0.1 C rate at 25 DEG C until the voltage reached 4.4 V (vs. Li), and then 4.4 V was maintained in the constant voltage mode And cut off at a current of 0.05 C rate. Then, at the time of discharging, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li). The charging and discharging process was performed two more times to complete the conversion process.

Subsequently, they were charged under the conditions of the following Table 2 under the conditions of the constant current (A1) and the constant voltage (4.4 V, 0.05 C cut-off), and then rested for 10 minutes. Then, discharge was performed under the condition of the constant current (A2) to 3.0 V according to the conditions of Table 2 below. The rate capability of the lithium metal battery was evaluated by charging and discharging at different current conditions.

Condition 1 Condition 2 Condition 3 Condition 4 Condition 5 Condition 6 Current A1 (C) 0.2 0.7 0.7 0.7 0.7 0.7 Current A2 (C) 0.2 0.2 0.5 1.0 1.5 2.0

The rate-limiting performance of the lithium metal battery produced according to Example 2 and Comparative Example 1 is shown in FIG.

 Referring to FIG. 9, it can be seen that the lithium metal battery manufactured in accordance with the second embodiment improves the rate-determining performance by being bridged with the lithium metal battery manufactured according to the first comparative example.

2) Examples 2, 11, 12, Comparative Example 1, Comparative Example 4

The lithium metal batteries prepared according to Examples 2, 11 and 12 and the lithium metal batteries prepared according to Comparative Examples 1 and 4

The lithium metal cell was charged with a constant current until the voltage reached 4.4 V (vs. Li) at a current of 0.1 C rate at 25 ° C, and then cut off at a current of 0.05 C rate while maintaining 4.4 V in the constant voltage mode. -off). Then, at the time of discharging, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li). The charging and discharging process was performed two more times to complete the conversion process. Then, the battery was charged at a constant current (0.7 C) and an electric voltage (4.4 V, 0.05 C cut-off), and then rested for 10 minutes. Then, discharge was performed until the voltage reached 3.0 V under a constant current (0.2 C or 1.5 C) condition. That is, the rate capability of the lithium metal battery was evaluated by changing the discharge rates to 0.2C and 1.5C, respectively. The results are shown in Table 2 below. C-rate is the discharge rate of the cell, which is the value obtained by dividing the total capacity of the cell by the total discharge time. In the following Table 3, the rate-limiting performance is calculated by the following equation (2).

[Formula 2]

Rate performance (%) = [(discharge capacity at 1.5C) / (discharge capacity at 0.2C)] x 00

division Rate performance (%) (1.5C / 0.2C) Example 2 94.25 Example 11 92 Example 12 94.25 Comparative Example 1 91 Comparative Example 4 91

As shown in Table 3, the lithium metal batteries prepared according to Examples 2, 11 and 12 showed improved rate-limiting performance as compared with the lithium metal batteries of Comparative Examples 1 and 4.

Evaluation example  7: Lithium ion transfer  a constant

1) Examples 2, 11, 12, Comparative Examples 1 and 4

The protective films used in Examples 2, 11, and 12 were sandwiched between the lithium metal thin films and electrolytes were added to prepare Li / Li symmetric cells. As the electrolyte, a liquid electrolyte was prepared by using 1,2-dimethoxyethane DME in a 2: 8 volume ratio) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE ) Dissolved in 1.0 M LiFSI was used as the electrolytic solution.

For comparison with the symmetric cell, a lithium metal thin film of Comparative Example 1 and a lithium metal negative electrode of Comparative Example 4 were respectively used and assembled together with an electrolyte to prepare a symmetric cell.

The lithium ion transference number (t _{Li +} ) of the symmetric cell was measured at 25 ° C, and some of the results are shown in Table 4 below.

The lithium ion transfer constant can be calculated by the following equation (2). The values required for calculation of the lithium ion transfer constants were measured by measuring the current decay with respect to the impedance and the input voltage with respect to the lithium symmetric cell (Electrochimica Acta 93 (2013) 254).

[Formula 3]

In equation (3), i _o is the initial current, iss is the steady state current, R ⁰ is the initial resistance, R ^ss is the rectified state resistance, and ΔV is the voltage difference.

division The lithium ion transfer constant (t _{Li +} ) Example 2 0.75-0.80 Example 11 0.67-0.70 Example 12 0.74-0.76 Comparative Example 1 0.56-0.58 Comparative Example 4 0.62-0.65

Referring to Table 4, the protective films of Examples 2, 11, and 12 showed increased lithium ion transfer rate as compared with Comparative Examples 1 and 4, indicating that the lithium ion transfer rate was improved.

Evaluation example  8: Cell voltage

A protective film prepared according to Example 2 was interposed between the lithium metal thin films and an electrolyte was added thereto to prepare a Li / Li symmetric cell. As the electrolyte, a mixture of 1,2-dimethoxyethane (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a 2: 8 volume ratio An electrolytic solution in which 1.0 M LiFSI was dissolved in a solvent was used.

For comparison with the above-mentioned symmetric cell, the lithium metal thin film used in Comparative Example 1 and the electrolyte were assembled to prepare a symmetric cell.

For each of the symmetric cells Since it is a lithium-lithium cell, it was charged and discharged at a constant current of 1 C / 1C. At this time, the voltage range was -1 to 1 V.

FIG. 10 shows the cell voltage change with time of the symmetric cell.

As shown in FIG. 10, it can be seen that the symmetric cell employing the protective film produced according to Example 2 has a smaller decrease in cell voltage change over time than the symmetric cell using the lithium metal thin film of Comparative Example 1 there was.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the exemplary embodiments or constructions. It will be apparent to those skilled in the art that various modifications and variations are possible in light of the above teachings will be. Accordingly, the scope of protection of the present invention should be determined by the appended claims.

10, 20: Lithium metal cathode 11, 21: Protective film
12, 22a: liquid electrolyte 22b: solid electrolyte
22: electrolyte 13, 23: anode

Claims (23)

Lithium metal cathode;
A protective film disposed on the lithium metal cathode and comprising at least one selected from the group consisting of i) a polymer, ii) a metal salt containing a Group 1 or Group 2 element, and a nitrogen-containing additive;
anode; And
And a liquid electrolyte interposed between the protective film and the anode,
Wherein at least one selected from a metal salt containing a Group 1 element or a Group 2 element and a nitrogen-containing additive is insoluble in an organic solvent of a liquid electrolyte. The method according to claim 1,
Wherein the metal salt containing the Group 1 element or the Group 2 element is a metal salt containing at least one selected from Cs, Rb, K, Ba, Sr, Ca, Na and Mg. The method according to claim 1,
The metal salt containing the Group 1 element or the Group 2 element is preferably selected from the group consisting of Cs bis (trifluoromethylsulfonyl) imide (CsTFSI: Cs), CsNO ₃ , CsPF ₆ , Cs bis sulfonyl) imide {CsFSI: Cs (bis (fluorosulfonyl ) imide)}, CsAsF 6, CsClO 4, CsBF 4, RbTFSI, RbNO 3, RbPF 6, RbFSI, RbAsF 6, RbClO 4, RbBF 4, KTFSI, KNO 3, _{KPF 6, KFSI, KAsF 6,} KClO 4, KBF 4, NaTFSI, NaNO 3, NaPF 6, NaFSI, NaAsF 6, NaClO 4, NaBF 4, Ba (TFSI) 2, Ba (NO 3) 2, Ba (PF 6 _{) 2, Ba (FSI) 2} , Ba (AsF 6) 2, Ba (ClO 4) 2, Ba (BF 4) 2, Sr (TFSI) 2, Sr (NO 3) 2, Sr (PF 6) 2, _{Sr (FSI) 2, Sr (} AsF 6) 2, Sr (ClO 4) 2, Sr (BF 4) 2, Ca (TFSI) 2, Ca (NO 3) 2, Ca (PF 6) 2, Ca (FSI _{) 2, Ca (AsF 6)} 2, Ca (ClO 4) 2, Ca (BF 4) 2, Mg (TFSI) 2, Mg (NO 3) 2, Mg (PF 6) 2, Mg (FSI) 2, _{Mg (AsF 6) 2, Mg} (ClO 4) 2 and Mg (BF ₄₎ is at least one selected from the group consisting of _2, TFSI is methylsulfonyl represents a mid-bis-trifluoromethyl, FSI is A lithium metal battery showing bisfluorosulfonylimide. The method according to claim 1,
The nitrogen-containing additive may be selected from the group consisting of inorganic nitrate, organic nitrate, inorganic nitrite, organic nitrite, organic nitroso compound, organic nitroso compound, NO compound, Lithium (Li ₃ N). 5. The method of claim 4,
Wherein the inorganic nitrate is at least one selected from the group consisting of lithium nitrate, potassium nitrate, cesium nitrate, barium nitrate and ammonium nitrate,
Wherein the organic nitrate is at least one selected from the group consisting of C1 to C20 dialkyl imidazolium nitrate, guanidine nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite,
The organic nitrite is at least one selected from the group consisting of ethylnitrite, propylnitrite, butylnitrite, pentylnitrite, and octylnitrite,
Wherein the organic nitro compound is at least one selected from the group consisting of nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitrotoluene, dinitrotoluene and nitropyridine,
Wherein the NO compound is at least one selected from the group consisting of pyridine N-oxide, C1 to C20 alkylpyridine N-oxide, and tetramethylpiperidine N-oxyl (TEMPO). The method according to claim 1,
Wherein the content of at least one selected from a metal salt containing a group I or II element and a nitrogen-containing additive in the protective film is 0.1 to 100 parts by weight based on 100 parts by weight of the polymer. The method according to claim 1,
Wherein the protective film comprises a metal salt containing a group I or II element and a nitrogen containing additive and the content of the metal salt containing the group I or II element is 0.01 to 99.99 parts by weight based on 100 parts by weight of the polymer, The content of the nitrogen-containing additive is 0.01 to 99.99 parts by weight based on 100 parts by weight of the polymer. The method according to claim 1,
Wherein the protective film comprises a metal salt containing a Group 1 or Group 2 element and a nitrogen containing additive and wherein the mixing weight ratio of the metal salt containing a Group 1 or 2 element to the nitrogen containing additive is 1: 9 to 9: 1, . The method according to claim 1,
Wherein the polymer is at least one polymer selected from a homopolymer, a block copolymer, and a graft copolymer, or a mixture thereof. 10. The method of claim 9,
Wherein the homopolymer is selected from the group consisting of polyvinyl alcohol, polymethyl methacrylate, polymethyl acrylate, polyethyl methacrylate, polyethylacrylate, polypropyl methacrylate, polypropyl acrylate, polybutyl acrylate, polybutyl methacrylate Acrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, polyglycidyl methacrylate, Lt; RTI ID = 0.0 &gt; and / or &lt; / RTI &gt; polyacrylonitrile. The method according to claim 1,
The polymer is a block copolymer comprising a first polymer block and a second polymer block,
Wherein the first polymer block is selected from the group consisting of polystyrene, hydrogenated polystyrene, polymethacrylate, poly (methyl methacrylate), polyvinylpyridine, polyvinylcyclohexane, polyimide, polyamide, polyethylene, polybutylene, (Ethylene terephthalate), poly (dimethyl terephthalate), polydimethylsiloxane, polyacrylonitrile, polymaleic acid, polymaleic acid (4-methyl-1-pentene), poly (butylene terephthalate) (Cyclohexyl methacrylate), poly (cyclohexyl vinyl ether), polyvinylidene fluoride, and polydivinylbenzene, or may be one or more selected from the group consisting of the aforementioned A polymer comprising two or more kinds of repeating units constituting a polymer,
Wherein the second polymer block is selected from the group consisting of polyethylene oxide, polypropylene oxide, polymethylmethacrylate, polyethylmethacrylate, polydimethylsiloxane, polyacrylic acid, polymethacrylic acid, polymethylacrylate, (C1-C20 alkyl carbonate), polynitrile, poly (meth) acrylate, polyoxyethylene (meth) acrylate, A lithium metal battery comprising at least one selected from the group consisting of polyphosphazines, polyolefins, polydienes, polyisoprenes, polybutadienes, polychloroprenes, polyisobutylenes, polyurethanes, polyethylenes, polybutylenes and polypropylenes. The method according to claim 1,
Wherein the lithium metal cathode further comprises an ion conductive film between the lithium metal cathode and the protective film. The method according to claim 1,
In the protective film, a metal salt containing a Group 1 or Group 2 element and a nitrogen-
Is increased from the liquid electrolyte to a region adjacent to the lithium metal cathode. The method according to claim 1,
Wherein the protective film further comprises at least one selected from inorganic particles, an ionic liquid, a polymeric ionic liquid, and an oligomer. 15. The method of claim 14,
Wherein the inorganic particles are at least one selected from SiO ₂ , TiO ₂ , ZnO, Al ₂ O ₃ , BaTiO ₃ , silsesquioxane having a cage structure, and a metal-organic framework (MOF). 15. The method of claim 14,
Wherein the content of the inorganic particles is 1 to 40 parts by weight based on 100 parts by weight of the polymer. 15. The method of claim 14,
Wherein the ionic liquid is at least one selected from the group consisting of i) ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, At least one cation selected from the group consisting of triazolium,
^{_{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-, PF 6 -}} , 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 ^- . The method according to claim 1,
Wherein the liquid electrolyte comprises a lithium salt and an organic solvent,
Wherein the organic solvent is selected from the group consisting of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, fluoroethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylene glycol dimethyl ether, trimethylene 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 2,2,3,3-tetrafluoropropyl ether. The method according to claim 1,
Wherein the thickness of the protective film is 1 to 20 占 퐉. The method according to claim 1,
Wherein the nitrogen-containing additive is at least one selected from LiNO ₃ and Li ₃ N,
A metal salt is cesium bistrifluoromethyl containing the group 1 or group 2 element methylsulfonyl imide _{(CsTFSI), CsNO 3, CsPF} 6, CsFSI, CsAsF 6, CsClO 4, and CsBF ₄ in the selected one or more of lithium metal battery . The method according to claim 1,
Wherein the lithium metal battery further comprises at least one selected from a separator, a solid electrolyte, a gel electrolyte, and a polymer ionic liquid. mixing at least one selected from i) a polymer, ii) a metal salt containing a group I or II element, and a nitrogen-containing additive to obtain a composition for forming a protective film;
Supplying the composition for forming a protective film to a lithium metal anode; And
A method for protecting a lithium metal anode of a lithium metal battery as defined in any one of claims 1 to 21, comprising drying the resultant to form a protective film. A protective film produced according to the method of claim 22.

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