KR20190068065A - Passivation Layer for Lithium Electrode, Lithium Electrode and Lithium Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to a protective film for a lithium electrode, a lithium electrode and a lithium secondary battery comprising the same. More specifically, the protective film of the lithium electrode containing nanocellulose and ion conductive polymers in a form of a nanocomposite exhibits high strength and high heat resistance. Therefore, the stability of the lithium secondary battery comprising the lithium electrode can be enhanced while suppressing the growth of the lithium dendrite.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a lithium electrode, a lithium electrode including the protective film, and a passivation layer for a lithium secondary battery,

The present invention relates to a lithium electrode protective film having high strength, high heat resistance and excellent ion conductivity and capable of inhibiting the formation and growth of lithium dendrite in a lithium electrode, a lithium electrode including the same, and a lithium secondary battery.

With the rapid development of the electronics, communications and computer industries, applications of energy storage technology to camcorders, mobile phones, notebooks, PCs, and even electric vehicles are expanding. Accordingly, development of high performance secondary batteries which are light and long-lasting and highly reliable is underway.

Lithium secondary batteries are attracting attention as a battery that satisfies these demands.

The lithium secondary battery has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is laminated or wound, and the electrode assembly is embedded in a battery case, and a non- do. The lithium secondary battery produces electrical energy by oxidation and reduction reactions when lithium ions are inserted / removed from the positive electrode and the negative electrode.

Typically, lithium metal, carbon, or the like is used as an anode of a lithium secondary battery, and lithium oxide, a transition metal oxide, a metal chalcogenide compound, and a conductive polymer are used as an anode.

In a lithium secondary battery using a double lithium metal as a negative electrode, a lithium foil is attached on the copper current collector or the lithium metal sheet itself is used as an electrode. Lithium metal has attracted a great deal of attention as a high-capacity cathode material because of its low dislocation and high capacity.

When the lithium metal is used as the cathode, nonuniformity of the electron density may occur on the surface of the lithium metal due to various factors when the battery is driven. Thus, lithium dendrite in the form of branches is formed on the surface of the electrode, and protrusions are formed or grown on the surface of the electrode, so that the electrode surface becomes very rough. Such lithium dendrites lead to deterioration of the performance of the battery and serious damage of the separator and short circuit of the battery. As a result, the temperature in the battery rises and there is a risk of explosion and fire of the battery.

In addition, the lithium used in the electrode, especially the lithium electrode, has high reactivity with the electrolyte component, and when the electrolyte component comes into contact with the lithium metal, a film called a passivation layer is formed by a spontaneous reaction. The protective film formed on the lithium surface during charging and discharging repeats destruction and formation. Therefore, when the battery is repetitively charged and discharged, the protective film component increases in the lithium negative electrode and the electrolyte is depleted. In addition, some of the reduced materials in the electrolyte cause side reactions with the lithium metal, thereby accelerating the consumption of lithium. As a result, the life of the battery is reduced.

Various studies have been conducted to stabilize the lithium metal. As a part of this research, a method of forming a protective film at a position in contact with the electrode has been proposed.

For example, a technique for forming a crosslinked polymer protective film for protecting the lithium electrode has been proposed. Although the crosslinked polymer protective film can inhibit the growth of lithium dendrites and stabilize the lithium electrode to increase the lifetime of the battery, the crosslinked polymer protective film has a problem of swelling or being damaged when it comes in contact with the electrolytic solution.

In addition, attempts have been made to stabilize the lithium metal and lower the interfacial resistance between the lithium electrode and the electrolyte by developing a lithium electrode protective film containing a polymer and inorganic particles. However, when the lithium dendrite is grown along the interface of the inorganic particles in the protective film There was a risk of a short circuit due to a problem.

Although lithium electrode protective films of various materials and shapes have been developed in this way, there are still many problems, and researches on protective films to solve these problems are continuing.

Japanese Laid-Open Patent Publication No. 2016-513860 discloses a cell having improved strength by forming a fibril-containing layer in the protective layer or on the protective layer on the electrochemically active material contained in the electrode. The fibrils may include cellulose or cellulose derivatives.

However, fibrils may be advantageous for improving the strength, but they may be vulnerable to improvement in heat resistance, and development of a lithium electrode protective film capable of preventing the growth of lithium dendrites while exhibiting high strength and high heat resistance characteristics is required.

Japanese Laid-Open Patent Application No. 2016-513860, "an electrochemical cell including a fibril material such as a fibril cellulose material"

As a result of various studies to solve the above problems, the inventors of the present invention have found that a lithium electrode protective film, which is a cellulose having a high strength property to maintain shape retention and electrochemical stability in an electrolyte solution and a low lithium ion conductivity In order to complement the characteristics, a protective film of a high strength and high heat resistant membrane type is prepared by mixing an ion conductive polymer which is easy to transfer lithium ion, and a cellulosic microparticle mixed with the ion conductive polymer so as to increase the inter- It was confirmed that the growth of lithium dendrites was suppressed and the electrochemical stability was high and the performance of the battery was improved.

Accordingly, an object of the present invention is to provide a protective film for a lithium electrode capable of suppressing the growth of lithium dendrites by high strength and high heat resistance.

Another object of the present invention is to provide a lithium electrode including a protective film capable of suppressing the growth of lithium dendrite due to high strength and high heat resistance.

Another object of the present invention is to provide a lithium secondary battery having improved electrochemical stability.

In order to achieve the above object, the present invention provides a protective film for a lithium electrode, comprising a nanocellulose and an ion conductive polymer.

The nanocellulose may be at least one selected from the group consisting of cellulose nanofibers (CNF), cellulose nanocrystals, and bacterial nanocellulose.

The nanocellulose may have a diameter of 1 nm to 10 mu m and a length of 100 nm to 10 mu m.

The viscosity of the 1% aqueous solution of the nanocellulose may be 1,000 to 4,000 Cp.

The nanocellulose may have a crystallinity of 50% to 80%.

The ion conductive polymer may be at least one selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl (meth) acrylate, polyvinyl chloride, polyvinylidene fluoride, (meth) acrylate, and poly (2-methoxyethyl) glycidyl ether may be used in combination with one or more of the above-mentioned monomers selected from the group consisting of ethylene glycol, propylene glycol monomethyl ether, ethylene glycol monomethyl ether,

And 100 to 400 parts by weight of the ion conductive polymer with respect to 100 parts by weight of the nanocellulose.

The nanocellulose and the ion conductive polymer may be contained in the form of a nanocomposite.

The protective film may further include at least one selected from the group consisting of a lithium salt and a particulate filler.

The lithium salt, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, _{CF 3 SO 3 Li, LiSCN,} LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenyl lithium borate, lithium Imides, and combinations thereof.

The particulate filler may include one selected from the group consisting of organic particles, inorganic particles, and combinations thereof.

The protective membrane may be in the form of a porous membrane.

The protective film may have a thickness of 10 nm to 10 탆.

The present invention also provides a lithium electrode in which a protective film as described above is laminated on one side or both sides of a lithium metal layer.

Wherein the lithium metal layer comprises lithium metal; Or lithium metal and at least one of Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Ge, Al, and a combination of these metals.

The present invention also provides a lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed therebetween and an electrolyte, wherein a protective film as described above is disposed between the negative electrode and the separator.

The protective film for a lithium electrode according to the present invention has a high strength property due to cellulose and can physically block the growth of lithium dendrites. In particular, since the nanocellulose in which cellulose is finely used is used, the mechanical strength is excellent and the coefficient of thermal expansion And it is possible to secure thermal stability. Also, it possesses a large amount of hydroxyl group (hydroxy group), so it is easy to control physical properties and control the functional groups.

In addition, since the protective film for a lithium electrode according to the present invention uses nano-cellulose and an ion conductive polymer together, it can improve the performance of the battery while exhibiting high strength by complementing the disadvantage of low ion conductivity cellulose.

In addition, since the protective film for a lithium electrode of the present invention includes nanocellulose and an ion conductive polymer in the form of a nanocomposite, it can exhibit heat-stable high heat resistance characteristics. In the case of nanocellulose, it forms strong interactions such as hydrogen bonding with PEO to form bonds with each other. CNF is dispersed uniformly in the form of nano to disperse in the form of a filler, and the protective film is formed in the form of a composite material to exhibit high heat resistance.

In addition, the protective film for a lithium electrode of the present invention can prevent the growth of lithium dendrite and enhance the stability of the battery.

1 is a schematic view of a lithium electrode according to the present invention.
2 is a FE-SEM (Field Emission Scanning Electron Microscope) photograph of a protective film formed on the lithium electrode of Example 3 and Comparative Example 2. Fig.
FIG. 3 is a graph showing storage modulus measurement results of the lithium electrode protective films of Examples 3, 4, 5, 6, and Comparative Example 1 in which no lithium salt is used in the production of the lithium electrode protective film.
4 is a graph showing storage modulus measurement results of the lithium electrode protective films of Examples 1 and 2 and Comparative Example 3 using a lithium salt in the production of the lithium electrode protective film according to temperature.
FIG. 5 is a graph showing the results of charge and discharge tests for a lithium secondary battery including the lithium electrode manufactured in Examples 1 and 2 and Comparative Example 3. FIG.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed in an ordinary or dictionary sense and the inventor can properly define the concept of the term to describe its invention in the best possible way It should be construed as meaning and concept consistent with the technical idea of the present invention.

Protection film for lithium electrode

The lithium electrode used as the cathode of the lithium secondary battery is formed of lithium metal and a protective film is formed on the surface of the lithium electrode to form and / or grow lithium dendrite on the surface of the protective electrode, thereby improving the battery characteristics Thereby preventing degradation. However, it has been impossible to sufficiently suppress the growth of lithium dendrites due to low strength, only with a protective film containing a conventional crosslinked polymer or inorganic particles. Therefore, in the present invention, cellulose is selected as a composition of a protective film, and a fibrous network structure having a dense structure is formed using the cellulose, thereby securing a sufficient level of strength to suppress the growth of lithium dendrite. In addition, the protective film compensates for the low ionic conductivity of the cellulose by using the ion conductive polymer together with the cellulose, so that the growth of the lithium dendrite can be suppressed and the performance of the battery can be secured at the same time.

The present invention relates to a protective film for a lithium electrode comprising nanocellulose and an ion conductive polymer.

Nano-cellulose is light in weight, has high strength and does not expand by heat. Therefore, high strength and high heat resistance can be imparted to a protective film for lithium electrode, thereby effectively preventing lithium dendrite growth and enhancing stability of battery .

In the present invention, the nanocellulose may be at least one selected from the group consisting of cellulose nanofiber (CNF), cellulose nanocrystal, and bacterial nanocellulose, which are nano-sized celluloses prepared by micronizing cellulose.

Among the nanocelluloses, the cellulose nanofibers are light in weight, have high strength and do not swell even when applied with heat, and can be more advantageous in strengthening the high strength and high heat resistance of the protective film for the lithium electrode.

The diameter of the nanocellulose may be 1 nm to 10 탆, preferably 1 nm to 1 탆, more preferably 1 nm to 50 nm. If the diameter of the nanocellulose is less than the above range, the effect of improving the strength may be insignificant. If the diameter of the nanocellulose is more than the above range, the binding force between cellulose may be deteriorated.

In addition, the length of the nanocellulose may be 100 nm to 10 탆, preferably 100 nm to 1 탆, and more preferably 100 nm to 800 nm. If the length of the nanocellulose is less than the above range, the effect of improving the strength may be insignificant. If the length of the nanocellulose is more than the above range, the bonding force between cellulose may be deteriorated.

In addition, the viscosity of the 1% aqueous solution of the nanocellulose may be 1,000 to 4,000 Cp, preferably 1,500 to 3,500 Cp, and more preferably 2,000 to 3,000 Cp. If the viscosity of the 1% aqueous solution of the nano-cellulose is less than the above-mentioned range, the nano-structure of the nanocellulose does not sufficiently proceed to deteriorate the mechanical properties of the protective film and the lithium dendrite growth inhibiting effect is insignificant. .

In addition, the nanocellulose may have a degree of crystallinity of 50% to 80%, preferably 65% to 80%, more preferably 70% to 75%. If the degree of crystallinity of the nanocellulose is less than the above range, the content of the impurity or amorphous region on the surface of the cellulose is increased, and the mechanical properties of the protective film And the effect of inhibiting the growth of lithium dendrites is insignificant. If it exceeds the above range, the lithium ion conductivity may be lowered.

In the present invention, the ion conductive polymer may function to complement the low ion conductivity of the nanocellulose.

The ion conductive polymer has a weight average molecular weight of 100 to 10,000,000, and the kind thereof is not particularly limited in the present invention, and any of those conventionally used in this field can be used. For example, a metal oxide such as polyethylene oxide (PEO), polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl (meth) acrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-co - at least one selected from the group consisting of hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethylene glycol (meth) acrylate and poly 2-methoxyethylglycidyl ether.

Among the above ion conductive polymers, polyethylene oxide is particularly excellent in lithium ion conductivity, and can form a network structure together with nanocellulose to enhance lithium ion conductivity, which is more advantageous as a material for a protective film for a lithium electrode.

The ion conductive polymer is introduced into the protective film in a crosslinked form. The crosslinking may be carried out by crosslinking between the ion conductive polymer and the crosslinking functional group, or by using a crosslinking agent.

The crosslinkable functional group is a functional group having at least three ethylenically unsaturated bonds in the molecular structure, and the functional group or a compound containing the functional group is chemically combined with the ion conductive polymer to make crosslinking.

The crosslinking agent is a compound having at least three ethylenically unsaturated bonds in the molecular structure.

Examples of the bifunctional crosslinking agent include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di Acrylate, neopentyl glycol adipate di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified di (meth) (Meth) acrylate, tricyclodecane dimethanol (meth) acrylate, dimethylol dicyclopentanedi (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, neopentyl glycol-modified trimethylpropane di (Meth) acrylate, polyethylene glycol diacrylate, divinylbenzene, polyester di (meth) acrylate, divinyl ether, ethoxylated bisphenol A di Etc. L) acrylate is possible. Examples of the trifunctional crosslinking agent include trimethylolpropane tri (meth) acrylate, trimethylolpropaneethoxylate tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol (Meth) acrylate, trimethylolpropane tri (meth) acrylate, tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylol propane tri (meth) acrylate, trimethylol propane and trimethylol propane tri (meth) acrylate. Examples of the tetrafunctional crosslinking agent include diglycerin tetra (meth) acrylate or pentaerythritol tetra (meth) acrylate. Examples of the pentafunctional crosslinking agent include propionic acid-modified dipentaerythritol penta (meth) acrylate Dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (metha) acrylate, and the like are used as the hexafunctional crosslinking agent.

Preferably, those having an ethylene oxide functional group in the molecular structure are used to increase the ionic conductivity of lithium ions, more preferably polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, trimethylolpropaneethoxylate triacrylate, Trimethylolpropane trimethacrylate and the like are used.

At this time, the content of the crosslinking agent is directly related to the film strength of the protective film, and preferably 5 to 200 parts by weight based on 100 parts by weight of the ion conductive polymer. If the crosslinking agent is used at a higher level, the strength of the protective film 3A is increased to easily break or damage. On the other hand, when the crosslinking agent is used in a low content, the strength of the protective film 3A is low, Therefore, the content of the crosslinking agent is appropriately adjusted so as to ensure the optimum coating film strength.

The protective film for a lithium electrode according to the present invention comprises 100 to 400 parts by weight, preferably 100 to 300 parts by weight, more preferably 100 to 300 parts by weight, of the ion conductive polymer based on 100 parts by weight of the nano-cellulose and 100 parts by weight of the nano- 200 parts by weight. If the content of the ion conductive polymer is less than the above range, the lithium ion conductivity of the protective film may be poor and the performance of the cell may deteriorate. If the content of the ion conductive polymer is less than the above range, the content of the nanocellulose is relatively decreased, Lithium dendrites may grow.

In the protective layer for a lithium electrode according to the present invention, the nanocellulose and the ion conductive polymer may form a nanocomposite.

The nanocomposite may include a polymer matrix and a nano-unit filler. Nanocellulose having a high aspect ratio is uniformly dispersed in the polymer resin and forms an interaction between the hydrophilic functional group of polyethylene oxide and the hydrophilic functional period of nanocellulose. Structures such as nanocomposites can improve the storage modulus and thermal properties (fracture temperature) due to the fillers present on the polymer matrix.

The nanocomposite forms a network structure of the nanocellulose and the ion conductive polymer, so that the nanocellulose and the ion conductive polymer may be advantageously improved in strength of the protective film, compared to a state where the nanocellulose and the ion conductive polymer are simply mixed.

In the protective film for a lithium electrode according to the present invention, the protective film may be in the form of a porous membrane.

As described above, the nanocellulose and the ion conductive polymer form a nanocomposite, and the protective film for the lithium electrode may be a porous membrane made of such a nanocomposite.

At this time, the porosity of the porous membrane may be more than 0 and less than 90%, and when the porosity is less than the above range, the lithium ion conductivity may be deteriorated.

In addition, the protective film may have a thickness of 10 nm to 10 mu m, preferably 10 nm to 1 mu m, more preferably 10 nm to 800 nm. If the thickness of the protective film is less than the above range, the effect of suppressing the growth of lithium dendrites is insignificant. If the thickness exceeds the above range, the battery may become thicker, which may be disadvantageous for commercialization.

The protective film for a lithium electrode according to the present invention may further include a material for further increasing the strength or for facilitating the lithium ion transfer for suppressing the growth of the lithium dendrite. The additive material may be at least one selected from the group consisting of lithium salts and particulate fillers.

The lithium salt is not particularly limited, and any lithium salt can be used as long as it can be used in a known lithium secondary battery. Specifically, is the above lithium salts _{LiCl, LiBr, LiI, LiClO 4} , LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO ₃ Li, CF ₃ SO ₃ Li, LiSCN, LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, Borate, lithium imide, and a combination thereof. Preferably, LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) represented by (CF ₃ SO ₂ ) ₂ NLi is available.

The lithium salt may be used in an amount of 1 to 200 parts by weight, preferably 50 to 150 parts by weight, more preferably 80 to 120 parts by weight, based on 100 parts by weight of the nano-cellulose. If the content of the lithium salt is less than the above range, the effect of improving the lithium ion conductivity may be insufficient. If the content of the lithium salt is less than the above range, the content of the nanocellulose may be decreased to lower the strength of the protective film.

The particulate filler can be inserted into the network structure of the protective film to form a space, and the lithium ions can move freely through the space thus formed, thereby further increasing the transfer speed of lithium ions. In addition, the particulate filler can contribute to suppression of lithium dendrite by increasing the strength of the protective film.

The particulate filler may include one selected from the group consisting of organic particles, inorganic particles, and combinations thereof, and may be made of a material having no electrically insulating and / or ionic conductivity.

Examples of the organic particles include olefin polymers such as polyethylene and polypropylene, acrylate polymers such as polyacrylate and polymethyl methacrylate, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoro Based polymer such as a fluorocarbon polymer (PFA), an ester-based polymer such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), a polysiloxane, a polysilazane, a polyethylene (PE) A siloxane-based polymer such as polycarbosilane, and the like can be used.

Examples of the inorganic particles include alumina, silica, titania, zirconia, zinc oxide, antimony oxide, ceria, talc, forsterite, calcium carbonate, aluminum hydroxide, talc, clay, mica, barium sulfate, zeolite, kaolin, mica, montmorillonite, Silicon nitride, boron nitride, barium titanate, and combinations thereof.

The particulate filler preferably has an average particle diameter of 1 nm to 5 占 퐉, preferably 5 nm to 1 占 퐉. If the average particle diameter is less than the above range, the particulate fillers 35 may aggregate to make it difficult to obtain uniform physical properties. On the other hand, if the average particle diameter is out of the above range, it is difficult to insert between the network structures of the protective film. .

The content of the particulate filler may be 0 to 100 parts by weight, preferably 1 to 50 parts by weight, more preferably 5 to 20 parts by weight based on 100 parts by weight of the nano-cellulose. If the content of the particulate filler exceeds the above range, the separation phenomenon with the nanocellulose in the process of producing the protective film may occur or the strength of the protective film may be excessively increased, so that the process of transferring or laminating the protective film on the lithium metal layer may not be easy. Adjust properly within the range.

Lithium electrode

The lithium electrode according to the present invention may have a protective film laminated on one side or both sides of the lithium metal layer.

1 is a schematic view of a lithium electrode according to the present invention, in which a protective film containing PEO and CNF is formed on one side of a lithium metal layer (Li foil). Further, the protective film may be adjacent to the separation membrane.

The composition, structure and characteristics of the protective film are as described above.

The lithium metal layer may be lithium metal or a lithium alloy. Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, and Ca are used as the elements of the lithium alloy. , Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, Al or an alloy thereof.

The lithium metal layer may be a sheet or a foil. In some cases, a lithium metal or a lithium alloy is deposited or coated by a dry process on the current collector, or a metal or alloy on the particle is deposited or coated by a wet process or the like Lt; / RTI >

When a current collector is used, a current collector may be disposed on one side of the lithium metal layer 11, a protective film may be disposed on the other side, or a protective film may be disposed between the lithium metal layer and the current collector. Such a structure is not particularly limited in the present invention, and various arrangements other than the above structure are possible. Preferably, a protective film is formed only on one side of the lithium metal layer when the current collector is used, and a protective film is formed on one side or both sides of the lithium metal layer when the current collector is not used.

In this case, the current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery. Examples of the current collector include copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper, stainless steel, Titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric having fine irregularities formed on its surface may be used.

Most preferably, the lithium metal layer according to the present invention is a lithium metal sheet.

Protection film for lithium electrode and lithium electrode

The protective film for a lithium electrode according to the present invention comprises: (a) mixing a nanocellulose and an ion conductive polymer and preparing a protective film forming composition using a solvent; (b) casting said aqueous solution onto a substrate; And (c) a step of drying the lithium electrode.

In the step (a), specific types, physical properties, and mixing ratios of the nanocellulose and the ion conductive polymer are as described above.

The solvent for preparing the protective film forming composition may be a mixed solvent of water and alcohol or a mixture of one or more organic solvents. In this case, the alcohol may be a lower alcohol having 1 to 6 carbon atoms, preferably methanol, Ethanol, propanol, isopropanol, and the like. Examples of the organic solvent include polar solvents such as acetic acid, dimethyl-formamide (DMFO), and dimethyl sulfoxide (DMSO), acetonitrile, ethyl acetate, methyl acetate, fluoroalkane, pentane, 2,2,4-trimethylpentane, But are not limited to, hexane, cyclopentane, diisobutylene, 1-pentene, 1-chlorobutane, 1- chloropentane, o-xylene, diisopropyl ether, 2- chloropropane, toluene, 1- chloropropane, , Non-polar solvents such as diethyl ether, diethyl sulfide, chloroform, dichloromethane, 1,2-dichloroethane, aniline, diethylamine, ether, carbon tetrachloride and THF (tetrahydrofuran) may be used.

The content of the solvent may be such that the concentration of the solvent is such as to facilitate the coating, and the specific content varies depending on the coating method and apparatus.

When a transfer method or the like is used, it may be a detachable substrate, that is, a glass substrate or a plastic substrate. In this case, the plastic substrate is not particularly limited in the present invention, and may be selected from the group consisting of polyarylate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polysilane, polysiloxane, polysilazane, But are not limited to, polyethylene (PE), polycarbosilane, polyacrylate, polymethacrylate, polymethylacrylate, polymethyl (meth) acrylate (PMMA) (CO), polyethyl methacrylate, cyclic olefin polymer (COP), polypropylene (PP), polyimide (PI), polystyrene (PS) , Polyvinyl chloride (PVC), polyacetal (POM), polyetheretherketone (PEEK), polyester sulfone (PES), polytetrafluoroethylene (PTFE), polyvinylidene fluoride ), A perfluoroalkyl polymer (PFA), and the like.

The casting in the step (b) is not particularly limited, and any known wet coating method can be used. For example, a method of uniformly dispersing using a doctor blade or the like, a die casting method, a comma coating method, a screen printing method and the like can be given.

Next, a drying process for removing the solvent after coating is performed. The drying process is performed at a temperature and a time period sufficient to sufficiently remove the solvent, and the conditions may vary depending on the type of the solvent, so that the present invention is not specifically described. For example, drying can be carried out in a vacuum oven of 30 to 200, and drying methods such as hot air, hot air, low-humidity air drying and vacuum drying can be used. The drying time is not particularly limited, but is usually in the range of 30 seconds to 24 hours.

The coating thickness of the protective film to be finally coated can be controlled by adjusting the concentration of the composition for forming a protective film or the number of coatings according to the present invention.

In addition, the protective film according to the present invention further includes additional materials for further increasing the strength for suppressing the growth of lithium dendrites, or for more smoothly carrying lithium ions. The additive composition may be at least one of a lithium salt and a particulate filler, and the kind and amount thereof are as described above.

The thus-prepared protective film can be transferred or lapped on a lithium metal layer to produce a lithium electrode.

Lithium secondary battery

The present invention also provides a lithium secondary battery including a separator interposed between an anode, a cathode, and an electrode, and an electrolyte, wherein the above-described lithium electrode protective film is disposed between the cathode and the separator.

At this time, the protective film is disposed so as to be in contact with one side of the cathode, but not in a coated form on the cathode, but in a form of transfer or lamination.

Such a lithium secondary battery has excellent battery characteristics even at a high rate without shorting the battery, and has excellent charge / discharge characteristics without increasing resistance even in the formation of a protective film. Such a lithium secondary battery has no possibility of explosion and fire at a high rate in the prior art, and thus can be said to be suitable for battery commercialization.

The anode has a form in which the cathode active material is laminated on the cathode current collector.

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, carbon, nickel, Titanium, silver, or the like may be used.

The cathode active material may be varied depending on the use of the lithium secondary battery, and a known material is used for the specific composition. For example, any lithium transition metal oxide selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium copper oxide, lithium nickel oxide and lithium manganese composite oxide, and lithium-nickel-manganese- More specifically, lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Lithium nickel oxide represented by LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga and x = 0.01 to 0.3); LiMn _2-x MxO ₂ (where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 to 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni , Cu or Zn) of lithium manganese complex oxide, Li (Ni _a Co _b Mn _c expressed in), O ₂ (where, 0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), Fe ₂ (MoO ₄ ) ₃ ; Sulfur element, disulfide compound, organosulfur compound and carbon-sulfur polymer ((C ₂ S _x ) _n : x = 2.5 to 50, n≥2); Graphite materials; Carbon black based materials such as Super-P, Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black and carbon black; Carbon derivatives such as fullerene; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; And conductive polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole; And a form in which a catalyst such as Pt or Ru is supported on the porous carbon support, but the present invention is not limited thereto.

The conductive material is used to further improve the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Polyphenylene derivatives and the like can be used.

The positive electrode may further include a binder for coupling the positive electrode active material to the conductive material and for coupling to the current collector. The binder may include a thermoplastic resin or a thermosetting resin. For example, it is possible to use polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride- Vinylidene fluoride copolymer, fluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoro Ethylene-chlorotrifluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymers, ethylene -Acrylic acid copolymer or the like may be used alone or in combination, but not always limited thereto, Anything that can be used as a binder in the technical field is possible.

The positive electrode may be prepared by a conventional method. Specifically, a composition for forming a positive electrode active material layer, which is prepared by mixing a positive electrode active material, a conductive material and a binder in an organic solvent, is applied and dried on a current collector, It can be produced by compression-molding the current collector for improving the electrode density. At this time, it is preferable that the organic solvent, the cathode active material, the binder and the conductive material can be uniformly dispersed and easily evaporated. Specific examples thereof include acetonitrile, methanol, ethanol, tetrahydrofuran, water, isopropyl alcohol and the like.

A conventional separation membrane may be interposed between the anode and the cathode. The separation membrane is a physical separation membrane having a function of physically separating the electrode. Any separator membrane can be used without any particular limitations as long as it is used as a conventional separation membrane. Particularly, it is preferable that the separator membrane is low in resistance against ion movement of the electrolyte solution and excellent in electrolyte wettability.

In addition, the separator separates or insulates the positive electrode and the negative electrode from each other, and enables transport of lithium ions between the positive electrode and the negative electrode. Such a separator may be made of a porous, nonconductive or insulating material. The separator may be an independent member such as a film, or a coating layer added to the anode and / or the cathode.

Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / (meth) Or nonwoven fabrics made of conventional porous nonwoven fabrics such as high melting point glass fibers and polyethylene terephthalate fibers can be used, but the present invention is not limited thereto.

The electrolyte solution of the lithium secondary battery is a lithium salt-containing electrolyte, which may be an aqueous or non-aqueous non-aqueous electrolyte, preferably a non-aqueous electrolyte comprising an organic solvent electrolyte and a lithium salt. An organic solid electrolyte or an inorganic solid electrolyte, but the present invention is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, -Dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, 4-methyl- The organic solvent may be selected from the group consisting of diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivative, Dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

As the non-aqueous solvent, an ether-based solvent is used to resemble the electrode protecting layer of the present invention. Examples thereof include tetrahydrofuran, ethylene oxide, 1,3-dioxolane, 3,5-dimethylisoxazole, Dimethylfuran, furan, 2-methylfuran, 1,4-oxane, 4-methyl dioxolane and the like are used

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium , Lower aliphatic carboxylic acid lithium, lithium 4-phenylborate, lithium imide, and the like can be used.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous electrolyte may contain, for example, at least one selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like may be added. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The shape of the above-described lithium secondary battery is not particularly limited and may be, for example, a jelly-roll type, a stack type, a stack-folding type (including a stack-Z-folding type), or a lamination- Stack-folding type.

An electrode assembly in which the positive electrode, the separator, and the negative electrode are sequentially stacked is prepared, and then inserted into a battery case. Then, an electrolyte is injected into the upper part of the case and sealed with a cap plate and a gasket to assemble a lithium secondary battery .

The lithium secondary battery can be classified into various types of batteries such as a lithium-sulfur battery, a lithium-air battery, a lithium-oxide battery, and a lithium total solid battery depending on the type of the anode material and the separator used. Coin type, pouch type, etc., and can be divided into a bulk type and a thin film type depending on the size. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

The lithium secondary battery according to the present invention can be used as a power source for a device requiring a high capacity and a high rate characteristic. Specific examples of the device include a power tool which is powered by an electric motor and moves; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (Escooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

Example  1: Preparation of lithium-sulfur battery

(1) Preparation of lithium electrode

211 parts by weight of polyethylene oxide (PEO) was mixed with 100 parts by weight of cellulose nano fiber (CNF) having a diameter of 3 nm and a length of 300 nm, and 89 parts by weight of LiTFSi as a lithium salt was mixed with purified water to prepare an aqueous solution ).

The aqueous solution was subjected to solution casting on a polyethylene terephthalate (PET) substrate subjected to corona treatment, and the film formed on the substrate was dried in a vacuum oven at 60 캜 for 3 hours to prepare a protective film having a thickness of 3 탆.

The protective film was rolled on a lithium metal film having a thickness of 150 mu m and transferred to fabricate a lithium electrode.

(2) Preparation of lithium-sulfur battery

A slurry was prepared in a weight ratio of 90: 5: 5, which was a normal sulfur-carbon composite material: conductive material (carbon black): barrell (styrene butadiene rubber and carboxymethyl cellulose mixed 5: 5) And then coated on a current collector of aluminum foil having a thickness of 탆 to prepare a sulfur electrode loaded at 5 mAh / cm 2. A coin cell was fabricated by placing 50 μl of ether electrolyte after placing the electrode and the sulfur electrode transferred with the protective film using the polymer and nano-cellulose on the separator.

Example  2 to 6: Preparation of lithium electrode and lithium secondary battery

176 parts by weight (Example 2), 100 parts by weight (Example 3) and 233 parts by weight (Example 3) were added to 100 parts by weight of the cellulose nanofibers (CNF), respectively, (Example 4), 300 parts by weight (Example 5) and 400 parts by weight (Example 6), respectively, to prepare a lithium electrode and a lithium secondary battery.

In Example 2, 124 parts by weight of LiTFSi was used, and in Examples 3 to 6, LiTFSi was not used.

Example  7

The same procedure as in Example 1 was carried out except that bacterial cellulose biosynthesized instead of cellulose nanofibers (CNF) was used. Gluconacetobacter xylinus strain was used as a strain. Liquid medium used for biosynthesis was mannitol, yeast and peptone mixed aqueous solution. The medium was sterilized through a high-pressure sterilizer and cultured in a 26 ° C incubator. The cultured bacterial cellulose was purified by NaOH solution, washed with water and stored in distilled water.

Bacterial cellulose and ion conductive polymer were mixed with 1 wt% aqueous solution of ion conductive polymer (PEO) and sufficiently impregnated with bacterial cellulose, followed by drying.

A lithium electrode and a lithium-sulfur battery were fabricated using a bacterial cellulose membrane, but without using LiTFSi.

Comparative Example  1: Manufacture of protective film and lithium electrode using ion conductive polymer

A lithium electrode and a lithium secondary battery were fabricated in the same manner as in Example 1 except that a protective film was prepared using PEO, which is an ion conductive polymer, without using cellulose nanofibers in manufacturing a protective film for a lithium electrode.

Comparative Example  2: Nano-cellulose  Preparation of protective film and lithium electrode

A lithium electrode and a lithium secondary battery were prepared in the same manner as in Example 1 except that a protective film was prepared using CNF without using PEO in the production of a protective film for a lithium electrode.

Comparative Example  3: Preparation of lithium electrode and lithium-sulfur battery

A lithium electrode (bare Li - REF) without a protective film was prepared and a lithium - sulfur battery was prepared with the above - described sulfur electrode.

Experimental Example  1: Evaluation of strength and ionic conductivity of protective film for lithium electrode

The strength of the protective film was evaluated according to the content of the nanocellulose and PEO used as the material of the protective film and the content of the LiTFSI used as the lithium salt. The results are shown in Table 1 below.

(1) Strength measurement

The protective films for lithium electrodes prepared in Examples 1 to 6 and Comparative Example 1 were measured for modulus according to temperature using a Dynamic Mechanical Analyzer (RSA-G2, TA instrument) to evaluate the strength of the protective film.

Referring to the following Table 1, it can be seen that Examples 1 to 6 exhibit excellent strength properties such as modulus at 30 ° C as compared with Comparative Example 1, and particularly superior strength characteristics when the content of CNF is relatively large. In addition, when the content of CNF is relatively increased, unlike Comparative Example 1, it has strength at a temperature of 60 ° C or higher, and the heat resistance property is improved.

(2) Measurement of electrolyte impregnation amount and ion conductivity

Electrolyte uptake was defined as the ratio of the membrane of Examples 3 to 6 and Comparative Example 2 divided by the weight before carrying out the weight of the membrane after carrying it in the ether-based electrolyte for 48 hours.

The ionic conductivity was measured by Electrochemical Impedance Spectroscopy (EIS) using a potentiostat using a polymer membrane having been previously impregnated with an electrolyte solution.

Referring to the following Table 1, it can be seen that the impregnation amount and the ion conductivity of the electrolytic solution in Examples 3 to 6 are superior to those in Comparative Example 2, and that the ion impregnation amount is increased when the content of CNF is decreased.

Example 7 showed a high electrolytic solution impregnation amount and ion conductivity even though the impregnation amount of PEO was lower than those of Examples 3 to 6. It can be expected that the migration of lithium ions is effective in the protective film prepared using bacterial cellulose.

Content (unit: parts by weight) Features of Nano-Cellulose Strength (MPa) Amount of impregnated electrolyte (%) Ion conductivity
(S / cm) Nano-cellulose Ion conductive polymer Lithium salt 30 ℃ 180 DEG C CNF PEO LiFSI diameter Length Example 1 100 211 89 3 nm 300 nm 1203 319 200 1.0 x 10 ^-4 Example 2 100 176 124 3 nm 300 nm 714 347 180 1.5 x 10 ^-4 Example 3 100 100 0 3 nm 300 nm 4949 1432 77 1.5 x 10 ^-5 Example 4 100 223 0 3 nm 300 nm 3402 734 150 4 x 10 ^-5 Example 5 100 300 0 3 nm 300 nm 3139 359 200 0.9 × 10 ^-4 Example 6 100 400 0 3 nm 300 nm 2634 Melting 210 1.3 × 10 ^-4 Example 7 Bacterial Nano-Cellulose: 100 40 0 3 nm 300 nm - - 49.5 2.0 x 10 ^-5 Comparative Example 1 0 100 0 - - 555 Melting - - Comparative Example 2 100 0 0 3 nm 300 nm - - 17 3.6 × 10 ^-9 Comparative Example 3 Bare Li - - - - - -

(3) Evaluation of surface morphology of CNF and ion conductive polymer mixed membrane

The protective films of Example 3 and Comparative Example 2 were confirmed by FE-SEM (Field Emission Scanning Electron Microscope).

2 is an FE-SEM photograph of a protective film formed on the lithium electrode of Example 3 and Comparative Example 2

2 (a) and 2 (b) are FE-SEM photographs of the protective films formed on the lithium electrodes of Example 3 and Comparative Example 2, respectively. In the case of the protective film of Example 3, the CNFs were well dispersed in the ion conductive polymer And nanocomposite was formed on the surface.

Experimental Example  2: Save Measurement of storage modulus

The storage elastic modulus of the lithium electrode protective film was measured using dynamic mechanical analysis (DMA).

FIG. 3 is a graph showing storage modulus measurement results of the lithium electrode protective films of Examples 3, 4, 5, 6, and Comparative Example 1 in which no lithium salt is used in the production of the lithium electrode protective film.

FIG. 4 is a graph showing storage modulus measurement results for Examples 1 and 2 and Comparative Example 3 using a lithium salt in the preparation of a lithium electrode protective film according to temperature. FIG.

Referring to FIG. 3 and FIG. 4, it can be seen that the embodiment has better storage elasticity than the comparative example. In Comparative Example 3, it was impossible to evaluate the storage elastic modulus when the lithium electrode protective film was not used.

Experimental Example  3: Charging and discharging  evaluation

The first cycle of the lithium-sulfur battery produced in Examples 1 and 2 and Comparative Example 3 according to the battery operation was charged and discharged at 0.1 C, and the cycle of charging and discharging at 0.2 C was repeated about 100 times Charge / discharge efficiency was measured.

FIG. 5 is a graph showing the results of charge and discharge tests for a lithium secondary battery including the lithium electrode manufactured in Examples 1 and 2 and Comparative Example 3. FIG.

Referring to FIG. 5, it can be seen that the battery life of Examples 1 and 2 is longer than that of Comparative Example 3. It was also found that charging and discharging proceeded about 100 times in Examples 1 and 2 without occurrence of an overvoltage. In particular, although the uniformity of charging and discharging was reduced in the first 10 cycles, the charging / discharging efficiency of the lithium - sulfur battery was recovered and confirmed to be well maintained. From these results, it can be seen that the protective film according to the present invention is excellent in not only the suppression performance of lithium dendrites but also the ion transport performance.

While the present invention has been described in connection with certain exemplary embodiments and drawings, it is to be understood that the present invention is not limited thereto and that various changes and modifications will be apparent to those skilled in the art. And various modifications and variations are possible within the scope of the appended claims.

Claims (16)

A protective film for a lithium electrode, comprising nanocellulose and an ion conductive polymer. The method according to claim 1,
Wherein the nanocellulose is at least one selected from the group consisting of cellulose nanofibers (CNF), cellulose nano-crystals, and bacterial nanocellulose. The method according to claim 1,
Wherein the nanocellulose has a diameter of 1 nm to 10 占 퐉 and a length of 100 nm to 10 占 퐉. The method according to claim 1,
Wherein the viscosity of the 1% aqueous solution of the nanocellulose is 1,000 to 4,000 Cp. The method according to claim 1,
Wherein the nanocellulose has a degree of crystallinity of 50% to 80%. The method according to claim 1,
The ion conductive polymer may be at least one selected from the group consisting of polyethylene oxide (PEO), polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl (meth) acrylate, polyvinyl chloride, polyvinylidene fluoride, which is at least one selected from the group consisting of -CO-hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethylene glycol (meth) acrylate and poly 2-methoxyethylglycidyl ether, Shield for the Dragon. The method according to claim 1,
And 100 to 400 parts by weight of an ion conductive polymer with respect to 100 parts by weight of the nanocellulose. The method according to claim 1,
Wherein the nanocellulose and the ion conductive polymer are contained in the form of a nanocomposite. The method according to claim 1,
Wherein the protective film further comprises at least one selected from the group consisting of a lithium salt and a particulate filler. 10. The method of claim 9,
The lithium salt, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, _{CF 3 SO 3 Li, LiSCN,} LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenyl lithium borate, lithium Imide, and a combination thereof. 10. The method of claim 9,
Wherein the particulate filler is one selected from the group consisting of organic particles, inorganic particles, and combinations thereof. The method according to claim 1,
Wherein the protective layer is a porous membrane. The method according to claim 1,
Wherein the protective film has a thickness of 10 nm to 10 탆. A lithium electrode in which a protective film is laminated on one side or both sides of a lithium metal layer,
Wherein the protective film is a protective film according to any one of claims 1 to 13. 15. The method of claim 14,
Wherein the lithium metal layer comprises lithium metal; Or lithium metal and at least one of Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Ge, Al, and a combination thereof. The lithium electrode according to claim 1, An anode, a cathode, and a separator interposed therebetween and an electrolyte,
The lithium secondary battery according to any one of claims 1 to 13, wherein a protective film is disposed between the cathode and the separator.

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