KR20190083916A - A separator having porous coating layer and lithium metal secondary battery including the same - Google Patents

Abstract

The present invention relates to a separator having a porous coating layer and a lithium metal secondary battery including the same. The separator comprises a porous polymer substrate; and a porous coating layer which is formed on at least one surface of the porous polymer substrate and includes inorganic particles having no oxidation and reduction reaction in the operating voltage range of a battery, a binder polymer, and an additive which causes a reduction reaction at 0 V to 5 V relative to lithium. The additive includes an amount of 1 to 10% by weight to the total weight of the porous coating layer. The lifespan and safety of the battery can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a separator including a porous coating layer, and a separator having porous coating layer and lithium metal secondary battery including same,

The present invention relates to a separator including a porous coating layer and a lithium metal secondary battery including the separator. More particularly, the present invention relates to a separator having improved lithium dendrite growth and improved battery life and safety, and a lithium metal secondary battery .

As the electrical, electronic, communication and computer industries rapidly develop, there is a growing demand for high capacity batteries. In response to this demand, a lithium metal secondary battery using lithium metal or a lithium alloy as a cathode as a cathode having a high energy density has received attention.

A lithium metal secondary battery is a secondary battery using a lithium metal or a lithium alloy as a cathode. The lithium metal has a low density of 0.54 g / cm ³ and a standard reduction potential of -3.045 V (SHE: based on standard hydrogen electrode). Thus, lithium metal has attracted the greatest attention as an electrode material for high energy density cells.

In the case of such a lithium metal secondary battery, unlike a conventional lithium ion secondary battery, a lithium metal is plated, charged, stripped and discharged to the cathode. When the lithium metal surface is not uniform, There is a characteristic in which the loss of lithium is large and the lifetime performance is reduced. Therefore, for uniform plating and stripping of the lithium metal, the surface composition and shape of the initial lithium metal must be well controlled.

However, due to the nature of the lithium metal with high reactivity, there is a limitation in that the metal surface treatment performed before cell assembly is difficult to maintain even after cell assembly.

In order to solve this problem, after stripping the passivation layer of the metal surface by stripping the lithium metal first in the activation process after the cell assembly, the surface composition is made uniform and the surface area of the lithium metal is widened, A method of heightening the height is proposed.

However, when such a method is used, it is difficult to actually apply lithium ion from striped lithium ion into a cathode material such as LCO or NCM to cause a problem such as structural variation and reversibility.

In addition, a negative electrode protection layer for minimizing a side reaction between a lithium metal and an electrolyte has been developed. Such a protection layer is easily deteriorated due to the growth of the lithium dendrite, and the function is often lost. In order to solve such a problem, it is necessary to impart a function of suppressing the growth of lithium dendrites on the surface of the lithium metal in the protective layer.

Therefore, a problem to be solved by the present invention is to provide a separator and a separator which can improve the lifetime and safety of the battery by suppressing the growth of lithium dendrites by introducing an additive capable of reacting with lithium metal into the porous coating layer formed on the separator And a lithium metal secondary battery including the same.

According to an aspect of the present invention, there is provided a porous polymer substrate comprising: a porous polymer substrate; And a porous coating layer formed on at least one surface of the porous polymer base material, the porous coating layer including inorganic particles, which do not cause an oxidation and reduction reaction in an operating voltage range of the battery, a binder polymer, and an additive in which a reduction reaction occurs at 0 V to 5 V And the additive is contained in an amount of 1 to 10% by weight based on the total weight of the porous coating layer.

Here, the additive may be an inorganic additive, an organic additive, or a mixture of the inorganic additive and the organic additive.

At this time, the inorganic additive may be a metal selected from the group consisting of Al, Si, Zn, Ge, and Sn, or a mixture of two or more thereof; Or Li _x M _y O _{z where} 0? _X? 3.2, 0.8? _Y? 3.2, and 2.8? _Z ? 8.2 where M is Si, V, Cr, Mn, Fe, Co, Ni, Cu, And at least one selected from the group consisting of Sb and the like).

The organic additive may be any one selected from the group consisting of an organosulfur compound, an organic free radical compound and an organic carbonyl compound, or a mixture of two or more thereof Lt; / RTI >

On the other hand, the inorganic particles may be inorganic particles selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof.

Herein, the inorganic particles having a dielectric constant of 5 or more are BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where , 0 <x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ Or a mixture of two or more of them.

The inorganic particles having the lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) _x O _y- 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO _{3 ,} 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , x <4, 0 <y < 1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x _{Si y S z, 0 <x} <3, 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z < 7) series glass, or a mixture of two or more thereof.

According to another aspect of the present invention, there is provided a lithium metal secondary battery comprising a positive electrode, a negative electrode including a lithium metal active material layer, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte, There is provided a lithium metal secondary battery characterized by being a separator of the present invention.

At this time, the porous coating layer may be formed only on one surface of the porous polymer substrate, and the porous coating layer may face the lithium metal active material layer.

According to one embodiment of the present invention, the activation process of the lithium metal secondary battery can be facilitated by introducing an additive capable of reacting with the lithium metal in the porous coating layer of the separator.

The additive chemically inhibits the growth of lithium dendrites, thereby improving the lifetime and safety of the battery.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and together with the description of the invention serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a schematic view showing a part of a cross section of a lithium metal secondary battery having a conventional separator including a porous coating layer.
2 is a schematic view showing a part of a cross section of a lithium metal secondary battery including a separator having a porous coating layer containing an additive according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the constitution described in the embodiments described herein is merely the most preferred embodiment of the present invention, and does not represent all the technical ideas of the present invention, so that various equivalents And variations are possible.

A separator according to the present invention comprises: a porous polymer base; And a porous coating layer formed on at least one surface of the porous polymer base material, the porous coating layer including inorganic particles, which do not cause an oxidation and reduction reaction in an operating voltage range of the battery, a binder polymer, and an additive in which a reduction reaction occurs at 0 V to 5 V And the additive is contained in an amount of 1 to 10% by weight based on the total weight of the porous coating layer. When the content range is satisfied, the above effect can be maximized. If the amount is less than the above range, the lithium metal is not sufficiently activated, which is undesirable. If the content is exceeded, lithium metal is excessively consumed.

FIG. 1 is a schematic view showing a part of a cross-section of a lithium metal secondary battery having a separator including a conventional porous coating layer. FIG. 2 is a cross-sectional view of a separator having a porous coating layer containing an additive according to an embodiment of the present invention. FIG. 2 is a schematic view showing a part of a cross-section of a lithium metal secondary battery including the lithium secondary battery of FIG.

1 and 2, the conventional separator including the porous coating layer 2 physically suppresses the lithium dendrite 5 growing in the lithium metal active material layer 3 as the negative electrode, There is a problem in that the cell can be short-circuited because the grown lithium dendrite 5 penetrates the porous coating layer 2 and the porous polymer base material 1 because there is no inhibition through the reaction.

On the other hand, when the additive 21 in which the reduction reaction, that is, the lithium occlusion reaction occurs in the range of 0 V to 5 V based on Li / Li ⁺ , is provided in the porous coating layer 20 of the separator, When the lithium metal secondary battery is operated, the additive 21 which is in contact with the lithium metal active material layer 30 as the negative electrode is reduced to be the reduced additive 22, and the lithium metal is oxidized to lithium ions. That is, through this chemical reaction, the activation effect of the lithium metal electrode can be exhibited, and at the same time, it can act as a protective layer of the lithium metal electrode.

Further, the additive 21, which has been electrically isolated and not reduced during the initial activation and charging / discharging process, reacts with the lithium dendrite 50 electrochemically during the subsequent cycle to oxidize the lithium metal. Therefore, the lithium dendrite 50), thereby ensuring the lifetime performance and safety of the cell.

The additive may be an inorganic additive, an organic additive, or a mixture of the inorganic additive and the organic additive, which does not dissolve in the electrolytic solution and undergoes a reduction reaction at 0 V to 5 V relative to lithium.

At this time, the inorganic additive may be a metal selected from the group consisting of Al, Si, Zn, Ge, and Sn, or a mixture of two or more thereof. And can dissolve the lithium metal at the interface when the lithium metal is contacted with the electrolyte impregnated.

And, as the inorganic additive, Li _x M _y O _z (0≤x≤3.2, 0.8≤y≤3.2, 2.8≤z≤8.2, and, M is Si, V, Cr, Mn, Fe, Co, Ni, Cu , Ge, Mo, Ru, and Sb) can be used. Here, y and z are determined according to the oxidation number of M and x. The lithium metal oxides are capable of causing a lithium intercalation reaction at 0 V to 5 V relative to lithium, and can dissolve the lithium metal at the interface when the lithium metal is in contact with the lithium metal in an impregnated state.

The organic additive may be any one selected from the group consisting of an organosulfur compound, an organic free radical compound and an organic carbonyl compound, or a mixture of two or more thereof Wherein the organic additive is capable of causing a lithium intercalation reaction at 0 V to 5 V relative to lithium and can dissolve the lithium metal at the interface when the lithium metal is contacted with the electrolyte impregnated.

At this time, the organic sulfur compounds ^{include, Dimeric organodisulfide (RSSR + 2e -} + 2Li + → 2LiSR, lithium occluding reaction voltage: 1.25 V to 1.63 V), Organodisulfide polymer (-SRS- n + 2ne - + 2nLi + → nLiSRSLi, Lithium intercalation reaction voltage: 2.3 V to 3.0 V), a polymer having a disulfide bond in a side chain, and a polymer having a polysulfide bond.

Examples of the organic free radical compound include Nitroxide compounds (RNOR + e ^- + Li ⁺ RNOLiR, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) 2,6,6-tetramethylpiperidinyloxy-4-yl-methacrylate)))).

Examples of the organic carbonyl compound include a carbonyl compound (RCOR + e ^- + Li ^{+ -} &gt; RCOLiR, quinone, quinine, etc .; a lithium intercalation reaction voltage: 3.0 V to 3.5 V, , 2.5 to 2.7 V in the case of a polymer, aromatic carboxylic acid derivatives, and conjugated carboxylate (lithium insertion reaction voltage: 0.8 V to 1.4 V).

For example, when Si is used as the additive, the following reaction takes place on the surface of the lithium metal electrode to activate the surface of the lithium metal electrode.

Si + 4.4 Li - &gt; Li _4.4 Si

Through this reaction, the surface of the lithium metal electrode can be activated without coating the protective layer of the lithium metal electrode or performing an additional process such as the activation process.

On the other hand, the average particle size of the inorganic particles is not particularly limited, but may be, but is not limited to, 0.001 μm to 10 μm in order to form a porous coating layer having a uniform thickness and a proper porosity.

The inorganic particles usable in the present invention are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as the oxidation and / or reduction reaction does not occur in the operating voltage range of the applied battery (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more. Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x , Ti _1-x ) O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where, 0 <x <1 Im), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, CaO, ZnO, ZrO 2, Y 2 O 3, Al 2 O 3, SiC and TiO ₂ , or a mixture of two or more thereof.

As the inorganic particles, inorganic particles having a lithium ion transferring ability, that is, inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium can be used. Non-limiting examples of inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li (LiAlTiP) _x O _y series glass (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as _3.25 Ge _0.25 P _0.75 S ₄ , (Li _x N _y , 0 <x <4, 0 <y <2) such as Li ₃ N and Li ₃ PO ₄ -Li ₂ S-SiS ₂ SiS ₂ based glass, such as _{(Li x Si y S z,} 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 There is P ₂ S ₅ based glass _{(Li x P y S z,} 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof as such.

The binder polymer may be at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichlorethylene, But are not limited to, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, Cyanoethylcellulose, cyanoethylcellulose, One selected from the group consisting of cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer and polyimide; And mixtures of two or more thereof. However, the present invention is not limited thereto.

The content of the binder polymer may be 1 to 30 parts by weight, or 1 to 15 parts by weight, based on 100 parts by weight of the inorganic particles. When the content of the binder polymer satisfies the above range, it is possible to appropriately prevent the inorganic particles from desorbing, prevent an increase in the internal resistance of the separator, and maintain a proper porosity of the porous coating layer.

In the porous coating layer, the binder polymer is coated on a part or the whole of the surface of the inorganic particles, and the inorganic particles are connected and fixed to each other by the binder polymer in an adhered state, and an interstitial volume (Interstitial volume) is formed, and the interstitial volume between the inorganic particles becomes empty space to form pores.

The thickness of the porous coating layer is not particularly limited, but may be 0.01 탆 to 50 탆, or 0.5 탆 to 10 탆 in order to prevent internal resistance increase and ensure safety of the battery.

On the other hand, the porous polymer substrate may be any porous polymer substrate commonly used in a battery. For example, a polyolefin porous membrane or a nonwoven fabric may be used. However, the porous polymer substrate is not particularly limited thereto.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, One membrane can be mentioned.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfide, polyethylene naphthalate, and the like are used alone Or a nonwoven fabric formed of a polymer mixed with these. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the porous polymer base material is not particularly limited, but is 1 탆 to 100 탆, or 5 탆 to 50 탆.

The size and porosity of the pores existing in the porous polymer substrate are also not particularly limited, but may be 0.001 탆 to 50 탆 and 10% to 95%, respectively.

According to another aspect of the present invention, there is provided a lithium metal secondary battery including a cathode, a cathode including a lithium metal active material layer, a separator interposed between the anode and the cathode, and a non-aqueous electrolyte, Is a separator according to the present invention.

Here, the porous coating layer is formed only on one surface of the porous polymer substrate, and the porous coating layer faces the lithium metal active material layer, so that the additive introduced into the porous coating layer plays the role of the above-mentioned.

On the other hand, the positive electrode may be composed of a positive electrode collector and a positive electrode active material layer coated on one side or both sides thereof. The positive electrode active material layer may be formed of a material selected from the group consisting of LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO _4, LiNiMnCoO _2, and LiNi _1-xyz Co _x M1 _y M2 _z O ₂ (M1 and M2 are independently selected from Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo each other X, y and z are independently selected from the group consisting of 0? X <0.5, 0? Y <0.5, 0? Z <0.5, x + y + z? , Or a mixture of two or more thereof.

The cathode active material layer may further include a conductive material to improve electrical conductivity. At this time, the conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the lithium secondary battery. In general, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material and the like can be used. Commercially available products as the conductive material include acetylene black series (manufactured by Chevron Chemical Co., (Chevron Chemical Company or Gulf Oil Company products), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MM (MMM)). For example, acetylene black, carbon black and graphite.

As a binder having a function of holding the positive electrode active material on the positive electrode collector and connecting the active materials therebetween, for example, polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene Polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, styrene butadiene rubber (SBR), carboxyl methyl cellulose (CMC) ) May be used.

The negative electrode has a lithium metal active material layer formed on the negative electrode collector. The negative electrode collector is not particularly limited as long as it has electrical conductivity without causing chemical change in the battery. For example, Nickel, titanium, silver or the like on the surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel and aluminum-cadmium alloy.

Meanwhile, the electrolyte salt included in the nonaqueous electrolyte solution which can be used in the present invention is a lithium salt. The lithium salt can be used without limitation as those conventionally used in an electrolyte for a lithium secondary battery. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

Examples of the organic solvent included in the non-aqueous electrolyte include those commonly used in an electrolyte for a lithium secondary battery, such as an ether, an ester, an amide, a linear carbonate, a cyclic carbonate, etc., Can be mixed and used.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Propylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC) and the like.

Specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate And mixtures of two or more of them may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte more easily. In addition, such cyclic carbonates can be used as dimethyl carbonate and diethyl carbonate When a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having a higher electric conductivity can be produced.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone and? -Caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The injection of the non-aqueous electrolyte may be performed at an appropriate stage of the manufacturing process of the lithium metal secondary battery, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling a lithium metal secondary battery or in a final stage of assembling a lithium secondary battery.

The lithium metal secondary battery according to the present invention is capable of winding, laminating, stacking and folding electrodes. The battery case may be cylindrical, square, pouch type, coin type, or the like.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

1. Manufacture of separator

A slurry for preparing a porous coating layer was prepared according to the composition shown in Table 1 below. Thereafter, the slurry was applied to one surface of a polyethylene porous polymer substrate to a thickness of 5 탆, and then dried at a temperature of 80 캜 to prepare a separator having a porous coating layer formed on one surface thereof.

Additive
Kinds Additive
weight% Slurry composition for preparing porous coating layer (g) Additive content Al ₂ O ₃ content PVDF content NMP content Example 1-1 Si 2 0.8 36.2 3.0 60.0 Example 2-1 V ₂ O ₅ 5 2.0 35.0 3.0 60.0 Example 3-1 Quinone 10 4.0 33.0 3.0 60.0 Comparative Example 1-1 Si 15 6.0 31.0 3.0 60.0 Comparative Example 2-1 V ₂ O ₅ 0.5 0.2 36.8 3.0 60.0 Comparative Example 3-1 Quinone 20 8.0 29.0 3.0 60.0 Comparative Example 4-1 - 0 0 37.0 3.0 60.0 Comparative Example 5-1 CaO 5 2.0 35.0 3.0 60.0 Comparative Example 6-1 Li ₃ PO ₄ 5 2.0 35.0 3.0 60.0

2. Manufacturing and Performance Evaluation of Lithium Metal Secondary Battery

(1) Production of Lithium Metal Secondary Battery

A cathode active material slurry was prepared by adding 96 wt% of LiCoO 2 as a cathode active material, 2 wt% of carbon black as a conductive material, and 2 wt% of PVDF as a binder to N-methyl-2-pyrrolidone (NMP). The prepared positive electrode active material slurry was coated on one surface of the aluminum current collector to a thickness of 65 μm, dried and rolled, and then punched to a predetermined size to prepare a positive electrode.

A lithium metal layer was coated on one surface of the copper collector and then rolled to prepare a lithium metal negative electrode.

Each of the separators of Examples and Comparative Examples described in Table 1 was sandwiched between the positive electrode and the negative electrode prepared as described above and inserted into a pouch-shaped battery case. Then, ethylene carbonate (EC), ethyl methyl carbonate ) Were mixed in a volume ratio of 50:50, and 1 M LiPF6 dissolved in an electrolyte was injected into the battery case to produce lithium metal secondary batteries. At this time, the porous coating layer formed on one surface of the separator faces the lithium metal layer of the negative electrode.

(2) Performance evaluation of lithium metal secondary battery

The lithium metal secondary batteries thus prepared were allowed to stand at room temperature for 2 days, sufficiently impregnated with the electrolytic solution, charged to 4.25 V at 0.1 C for 10 hours, left at room temperature for 2 days, and aged.

Thereafter, charging and discharging were performed at 0.1 C in the range of 3 V to 4.25 V, and the initial discharging capacity was measured. Thereafter, the discharging capacity was measured 100 times after 0.3 C charging and 0.5 C discharging. The results of calculating the discharge capacity retention rate are shown in Table 2 below.

Additive
Kinds Additive
weight% Performance evaluation of lithium metal secondary battery 1 discharge capacity (mAh) Capacity retention after 100 times charge / discharge (%) Examples 1-2 Si 2 57.6 71.1 Example 2-2 V ₂ O ₅ 5 58.1 69.7 Example 3-2 Quinone 10 57.4 73.8 Comparative Example 1-2 Si 15 58.8 32.4 Comparative Example 2-2 V ₂ O ₅ 0.5 56.9 57.5 Comparative Example 3-2 Quinone 20 57.5 41.4 Comparative Example 4-2 - 0 57.8 57.8 Comparative Example 5-2 CaO 5 58.0 54.0 Comparative Example 6-2 Li ₃ PO ₄ 5 58.2 56.7

As can be seen from the above Table 2, in the case of the lithium metal secondary batteries of Examples 1-2, 2-2 and 3-2 using the additive of the present invention in an appropriate amount, the porous coating layer formed on the separator activates the surface of the lithium metal layer It can be confirmed that the life characteristic is remarkably improved. These results are remarkable in comparison with Comparative Examples 5-2 and 6-2 using an electrochemically stable additive.

On the other hand, in the case of Comparative Examples 1-2 and 3-2 in which the content of the additive exceeded the range of the additive, it was confirmed that the additive occluded excess lithium and the lifetime performance was rather reduced. In the case of 2-2, it can be confirmed that the additive does not sufficiently activate the surface of the lithium metal layer, so that the lifetime performance is not improved.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

1, 10: Porous polymer substrate
2, 20: Porous coating layer
3, 30: Lithium metal active material layer
4, 40: cathode collector
5, 50: lithium dendrite
21: Additive
22: Reduced additives

Claims (9)

Porous polymeric substrates; And
A porous polymer layer formed on at least one side of the porous polymer base material and containing an inorganic particle which does not cause an oxidation and reduction reaction in an operating voltage range of the battery, a binder polymer, and an additive that causes a reduction reaction at 0 V to 5 V relative to lithium Respectively,
Wherein the additive is contained in an amount of 1 to 10% by weight based on the total weight of the porous coating layer. The method according to claim 1,
Wherein the additive is an inorganic additive, an organic additive, or a mixture of the inorganic additive and the organic additive. 3. The method of claim 2,
Wherein the inorganic additive is a metal selected from the group consisting of Al, Si, Zn, Ge, and Sn, or a mixture of two or more thereof; Or Li _x M _y O _{z where} 0? _X? 3.2, 0.8? _Y? 3.2, and 2.8? _Z ? 8.2 where M is Si, V, Cr, Mn, Fe, Co, Ni, Cu, And at least one element selected from the group consisting of Sb and the like). 3. The method of claim 2,
The organic additive may be any one selected from the group consisting of an organosulfur compound, an organic free radical compound and an organic carbonyl compound, or a mixture of two or more thereof Features a separator. The method according to claim 1,
Wherein the inorganic particles are inorganic particles selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having a lithium ion transporting ability, and mixtures thereof. 6. The method of claim 5,
Inorganic particles is greater than or equal to the dielectric constant of _{5, BaTiO 3, Pb (Zr x} , Ti 1-x) O 3 (PZT, where, 0 <x <1 _{Im), Pb 1 - x La x} Zr 1 - y Ti y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where 0 (x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ , Or a mixture of two or more thereof. 6. The method of claim 5,
Wherein the inorganic particles having lithium ion transferring ability are selected from the group consisting of lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) x O y series glass (0 <x <4, 0 < y <13), lithium lanthanum titanate (Li _x La _y TiO _{3 ,} 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 4, 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y _{S z, 0 <x <3} , 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 < z <7) series glass, or a mixture of two or more thereof. A lithium metal secondary battery comprising a negative electrode including a positive electrode and a lithium metal active material layer, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte,
The lithium metal secondary battery according to any one of claims 1 to 7, wherein the separator is a separator. 9. The method of claim 8,
Wherein the porous coating layer is formed only on one surface of the porous polymer substrate,
Wherein the porous coating layer faces the lithium metal active material layer.

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