KR20210112925A - Catholyte for lithium metal battery, composite cathode for lithium metal battery including the same, preparing method thereof, and lithium metal battery comprising the same - Google Patents

Abstract

Disclosed are a catholyte for a lithium metal battery to increase the ionic conductivity of an anode, a composite cathode for a lithium metal battery including the same, a manufacturing thereof, and a lithium metal battery including the same. According to the present invention, the catholyte for a lithium metal battery including a lithium negative electrode comprises: i) a cross-linked polymer of a first monomer having at least two double bonds and a second monomer having one or more double bonds; and ii) a liquid electrolyte including lithium salt and a nitrile-based compound. The first monomer includes at least three or more repeating units represented by chemical formula 1 and one selected from a group represented by chemical formula 2 is bonded to both ends of the repeating unit. The content of the liquid electrolyte is 50 to 500 parts by weight based on 100 parts by weight of the cross-linked polymer.

Description

A cathode electrolyte for a lithium metal battery, a composite anode for a lithium metal battery including the same, a manufacturing method thereof, and a lithium metal battery comprising the same comprising the same}

A cathode electrolyte for a lithium metal battery, a composite anode for a lithium metal battery including the same, a manufacturing method thereof, and a lithium metal battery including the same.

A lithium metal battery using a lithium anode can lower the weight density of the battery and improve the energy density, making it possible to realize a battery with high capacity and high energy density. However, since lithium metal batteries have very high reactivity with liquid electrolytes, the interfacial resistance due to by-products on the surface of the lithium anode during the electrochemical reaction is rapidly increased, and the vertical growth of dendrites causes short circuits, resulting in reduced battery life or reduced battery life. An explosion due to a short circuit can cause serious problems in terms of safety.

Accordingly, in a lithium metal battery using a lithium negative electrode, a solid electrolyte or a polymer electrolyte is used, and a separate solid electrolyte or a polymer electrolyte is generally used as the positive electrolyte for the positive electrode.

However, the positive electrode electrolyte known so far has room for improvement because the effect of suppressing dendrite formation and improving ionic conductivity on the surface of the negative electrode does not reach a satisfactory level.

One aspect is to provide a positive electrode electrolyte for a lithium metal battery capable of delaying the formation of dendrites on the surface of the negative electrode and improving the ionic conductivity of the positive electrode.

Another aspect is to provide a composite anode for a lithium metal battery comprising the above-described cathode electrolyte, a method for manufacturing the same, and a lithium metal battery including the same.

According to one aspect, it is a positive electrolyte for a lithium metal battery including a lithium negative electrode,

The cathode electrolyte comprises: i) a cross-linked polymer of a first monomer having at least two double bonds and a second monomer having one or more double bonds; ii) a lithium salt; and a liquid electrolyte comprising a nitrile-based compound,

The first monomer is a compound containing at least three or more repeating units represented by the formula (1), and one selected from the group represented by the following formula (2) is bonded to both ends of the repeating unit,

The amount of the liquid electrolyte is 5 to 45 parts by weight based on 100 parts by weight of the cross-linked polymer. A cathode electrolyte for a lithium metal battery is provided.

[Formula 1]

,

,

In Formula 1, E is ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol, propoxylated alkanediol , trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxyl Lated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, propoxylate It is a residue derived from the group selected from bisphenol A and combinations thereof,

n of each repeating unit is independently an integer from 1 to 20,

[Formula 2]

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,

,

,

,

,

,

,

,

,

,

,

,

,

In Formula 2, R is independently a hydrogen atom, a C1-C10 alkyl group, a C6-C20 aryl group, or a combination thereof.

According to another aspect, there is provided a composite positive electrode for a lithium metal battery comprising the above-described positive active material, a conductive agent, a binder, and the above-described positive electrolyte.

According to another aspect, a composite anode; lithium negative electrode; and the above-described electrolyte interposed therebetween. A lithium metal battery containing is provided.

According to another aspect, a first monomer having at least two double bonds and a second monomer having one or more double bonds; lithium salt; and applying and curing the composite positive electrode composition containing a liquid electrolyte containing a nitrile-based compound on the positive electrode current collector;

The first monomer is a compound containing at least three or more repeating units represented by the formula (1), and one selected from the group represented by the following formula (2) is bonded to both ends of the repeating unit,

The content of the liquid electrolyte is 50 to 500 parts by weight based on 100 parts by weight of the cross-linked polymer is provided a method of manufacturing a composite cathode for a lithium metal battery.

[Formula 1]

,

,

In Formula 1, E is ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol, propoxylated alkanediol , trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxyl Lated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, propoxylate It is a residue derived from the group selected from bisphenol A and combinations thereof,

n of each repeating unit is independently an integer from 1 to 20,

[Formula 2]

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,

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,

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In Formula 2, R is independently a hydrogen atom, a C1-C10 alkyl group, a C6-C20 aryl group, or a combination thereof.

The positive electrolyte for a lithium metal battery according to an embodiment cannot effectively leach out of the positive electrode plate in a liquid form, so that when used in the positive electrolyte of a lithium metal battery using a lithium negative electrode, the growth of dendrites on the surface of the negative electrode can be effectively delayed. and can improve the ionic conductivity of the anode. By using such a positive electrolyte and a composite positive electrode containing the same, it is possible to manufacture a lithium metal battery that ensures safety and has a long lifespan.

1 schematically shows the structure of a cathode electrolyte according to an embodiment.
2A to 2C are graphs showing changes in voltage and current according to capacity in the lithium metal batteries of Example 3 and Comparative Examples 3 and 4, respectively.
3 is a photograph showing the lifespan characteristics of the lithium metal batteries of Example 3 and Comparative Example 3;
4A to 4C are photographs showing the external appearance of the positive electrode in the lithium metal battery of Example 3, Comparative Example 3, and Comparative Example 4, in which the cycle of the semi-finished state was not performed before the cell production.
5 shows the structure of a lithium metal battery according to an embodiment.

Hereinafter, an exemplary cathode electrolyte for a lithium metal battery, a composite anode for a lithium metal battery including the same, a manufacturing method thereof, and a lithium metal battery including the same will be described in detail with reference to the accompanying drawings.

A positive electrolyte for a lithium metal battery including a lithium negative electrode is provided. The positive electrolyte comprises: i) a cross-linked polymer of a first monomer having at least two double bonds and a second monomer having one or more double bonds; ii) a lithium salt; and a liquid electrolyte including a nitrile-based compound, wherein the first monomer contains at least three or more repeating units represented by formula (1), and one selected from the group represented by formula (2) at both ends of the repeating unit is a bonded compound, and the content of the liquid electrolyte is 50 to 500 parts by weight based on 100 parts by weight of the crosslinked polymer.

[Formula 1]

,

,

In Formula 1, E is ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol, propoxylated alkanediol , trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxyl Lated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, propoxylate It is a residue derived from a group selected from tide bisphenol A and combinations thereof, and n of each repeating unit is independently an integer from 1 to 20;

[Formula 2]

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,

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,

,

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,

,

,

In Formula 2, R is independently a hydrogen atom, a C1-C10 alkyl group, a C6-C20 aryl group, or a combination thereof.

If the content of the liquid electrolyte is less than 50 parts by weight based on 100 parts by weight of the crosslinked polymer, the effect of improving the ionic conductivity of the positive electrode containing the positive electrolyte is insignificant, and if it exceeds 500 parts by weight, the capacity and lifespan characteristics of the lithium metal battery may be reduced. .

The content of the liquid electrolyte is, for example, 70 to 480 parts by weight, 80 to 450 parts by weight, 90 to 430 parts by weight, 95 to 400 parts by weight, or 100 to 300 parts by weight based on 100 parts by weight of the crosslinked polymer.

Three or more repeating units represented by Formula 1 constituting the first monomer are selected to be the same as or different from each other. That is, the first monomer includes a repeating unit represented by Formula 1, but E of Formula 1 may be selected to be the same as or different from each other.

The crosslinked polymer has a network structure through chemical and/or physical bonding of the first monomer and the second monomer.

The first monomer has two or more double bonds at the terminal and is an oligomer having a weight average molecular weight of 500 or more, for example, 1,000 to 1,000,000, and has a structure including a structure of repetitive polyalkylene oxide, polyisocyanate, polyol, and the like. And the second monomer has one double bond and is an alkylene acrylate having 4 or more and 10 or less carbon groups, and participates in random copolymerization and crosslinking together with the first monomer to form a structure of a polymer electrolyte.

The weight average molecular weight of the oligomer is, for example, 10,000 to 50,000, 20,000 to 30,000, or 25,000.

As an electrolyte for a lithium metal battery employing a lithium anode, it is known to use a polyethylene-based polymer electrolyte stable for lithium metal or a gel-type polymer electrolyte made by curing an acrylic polymer and an organic electrolyte by mixing them. Among them, the polyethylene-based polymer electrolyte can be driven only at high temperatures due to its low ionic conductivity. In addition, the gel-type polymer electrolyte has a disadvantage that there is a possibility of organic electrolyte leakage at a high temperature, and thus a side reaction may occur by reacting with the actual lithium metal. When such an electrolyte is used, the interfacial resistance due to by-products on the surface of the lithium negative electrode during the electrochemical reaction rapidly increases or a short circuit occurs, so that the lifespan of the lithium metal battery does not reach a satisfactory level, so improvement is required.

Accordingly, the present inventors have solved the above-described problems to effectively delay the formation of dendrites on the surface of the lithium negative electrode in a lithium metal battery using a lithium negative electrode and improve the ionic conductivity of the positive electrode, and a composite positive electrode including the same. The present invention has been completed.

1 schematically shows the structure of a cathode electrolyte according to an embodiment.

The positive electrode 10 has a structure in which a liquid electrolyte 12 doped with a lithium salt having high ion conductivity is impregnated in the polymer network 11 . The polymer network 11 contains a crosslinked polymer having a network structure through chemical and/or physical bonding of the first monomer and the second monomer. The crosslinked polymer may have, for example, a random copolymer crosslinked structure. The positive electrode electrolyte contains the cross-linked polymer to improve chain mobility so that lithium ions move smoothly, thereby improving ion conductivity.

The plastic crystal electrolyte (PCE) has a structure capable of collecting a lithium salt-doped liquid electrolyte with high ion conductivity. The liquid electrolyte is contained in the polymer network 11 having a cross-linked structure to obtain an effect of blocking it from leaking out. Through this, it is possible to prevent leakage in a high-temperature environment, and by securing the durability of the polymer structure, there is no risk of leakage of the liquid electrolyte contained therein even in a high-temperature environment. In addition, it is possible to improve the stability of the electrochemical reaction with the effect of improving the side reaction with lithium metal.

Since the liquid electrolyte contains a nitrile-based compound and the polymer electrolyte has a plastic crystal electrolyte form, the positive electrode electrolyte and the composite positive electrode employing the same have excellent ion conductivity. Herein, the term "plastic crystal electrolyte (PCE)" has a property that the orientation or degree of freedom of chemical molecules constituting the electrolyte changes depending on the temperature range. PCE may have crystallinity because the arrangement of the molecular structure varies depending on the temperature region.

The nitrile-based compound may include succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, or a combination thereof.

Lithium salts are for example LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N(LiTFSI), Li(FSO ₂ ) ₂ N(LiFSI), LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₃ C, LiBPh, or a combination thereof. FSI stands for bis(fluorosulfonyl)imide, TFSI stands for bis(trifluoromethanesulfonyl)imide, and Ph stands for phenyl.

As described above, the positive electrode electrolyte contains a cross-linked polymer of the first and second monomers to supplement the fluidity of a general plastic crystal electrolyte. Heat stability is ensured because softening does not occur even when added.

In addition, the positive electrolyte according to an embodiment does not change in structure when stored at a high temperature, and when it is used, the reactivity between the lithium metal and the positive electrolyte is suppressed. In addition, the positive electrolyte according to an embodiment has low reactivity with lithium at high temperature, so there is little concern about side reactions, and it is possible to manufacture a lithium metal battery having an advantageous long life while securing safety by inhibiting the growth of lithium dendrites. These lithium metal batteries are used in mobile and automobile batteries to ensure stability, and high-capacity batteries can be implemented using lithium metal.

The polymer network 11 and the PCE 12 may be impregnated with a liquid electrolyte having high ion conductivity due to intramolecular interaction.

When only an electrolyte having a polymer network containing a crosslinked polymer is used as the anode electrolyte, oxidation stability is reduced. And when only PCE is used as the positive electrolyte, SN is adsorbed to the positive electrode active material to increase resistance, and at a driving temperature of 60° C. or higher, it is liquefied and may be eluted to the outside of the positive electrode plate.

However, since the positive electrode electrolyte according to an embodiment has a structure in which PCE is impregnated in a polymer network, a problem in the case of using only PCE can be solved.

The second monomer cross-linked with the first monomer is a compound represented by the following formula (6), a compound represented by formula (7), a compound represented by formula (8), or a combination thereof.

[Formula 6]

In Formula 6, R is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, and L ₁ is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or its a combination, and A represents, independently of each other, a chemical bond or -CH ₂ -,

[Formula 7]

In Formula 7, L1 is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, -CH2CH2NHC(=O)OL ₂ , -(CH ₂ ) _k OC(=O )L ₃ , or -(CH ₂ ) _k O(=O)NH-(CH ₂ )O(C=O)(C=CH ₂ )R, or a combination thereof, R is hydrogen, a C1-C10 alkyl group or C6-C20 aryl group, k is an integer of 1 to 5,

L ₂ and L ₃ are each independently hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof,

[Formula 8]

In Formula 8, L ₁ is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof.

The first monomer is, for example, a compound represented by Formula 3 or a compound represented by Formula 3-1.

[Formula 3]

[Formula 3-1]

In Formulas 3 and 3-1, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane, and a, b and c are each independently 1 an integer from 7 to 7, an integer from 1 to 5, or an integer from 2 to 4, and l, m and n are each independently an integer from 1 to 20, an integer from 2 to 15, an integer from 3 to 10, and an integer from 3 to 8 It is an integer, or an integer of 4-6.

In Formulas 3 and 3-1, EG is -(OCH ₂ CH ₂ )-, and DEG is -(CH ₂ OCH ₂ )-. and

In Formulas 3 and 3-1, TMP is, for example, -C{(CH ₂ O) _k (CH ₂ CH ₃ )} _z -, where k is a number from 1 to 10, 1 to 8, or 1 to 5, and z is a number from 1 to 10, 1 to 10, 1 to 8, or 1 to 5.

As the first monomer, a compound represented by Formula 4 or a compound represented by Formula 5 may be used.

[Formula 4]

In Formula 4, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane,

l, m and n are each independently an integer from 1 to 20,

[Formula 5]

In Formula 5, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane,

l, m and n are each independently an integer from 1 to 20.

In Formulas 4 and 5, EG is -(OCH ₂ CH ₂ )-, DEG is -(CH ₂ OCH ₂ )-, and TMP is -C{(CH ₂ O) _k (CH ₂ CH ₃ )} _z - , k is a number from 1 to 10, 1 to 8, or 1 to 5 and z is a number from 1 to 10, 1 to 10, 1 to 8, or 1 to 5.

l, m and n are each independently an integer of 2 to 15, an integer of 3 to 10, an integer of 3 to 8, or an integer of 4 to 6;

The second monomer is, for example, a linear acrylate such as a compound represented by the following formula (9) (hexyl acrylate), pentyl acrylate, propyl acrylate, butyl acrylate, or a combination thereof.

[Formula 9]

The positive electrolyte according to an embodiment is 1 X 10 ^-6 S/cm or more, 1 X 10 ^-4 S/cm or more, for example, 5×10 ^-4 S/cm or more, specifically 1×10 at about 25°C. ^-3 S/cm or more, for example, 1 X 10 ^-6 S/cm to 1 X 10 ^-4 S/cm.

The above-described positive electrolyte includes a first monomer having two double bonds and a second monomer having one or more double bonds; lithium salt; And it can be prepared by coating and curing a cathode electrolyte composition comprising a nitrile-based compound on a substrate.

The mixing weight ratio of the first monomer and the second monomer is 95:5 to 20:80, for example, 50:50. When the mixing weight ratio of the first monomer and the second monomer is within the above range, a composite electrolyte having excellent ionic conductivity and strength can be obtained, and high-temperature storage characteristics are improved without deterioration of the lifespan of a lithium metal battery employing the positive electrode electrolyte.

The cathode electrolyte composition is, for example, obtained by mixing a first monomer and a second monomer to obtain a first mixture, separately mixing a lithium salt and a nitrile-based compound to prepare a second mixture, and mixing the first mixture and the second mixture It can be obtained according to the step of mixing. When the first mixture and the second mixture are mixed at a temperature of, for example, 20 to 70°C, or 30 to 65°C, a cathode electrolyte composition having a more uniform composition can be obtained.

The content of the nitrile-based compound in the positive electrolyte composition is 10 to 70 parts by weight based on 100 parts by weight of the first monomer. And the content of the lithium salt is 10 to 50 parts by weight based on 100 parts by weight of the first monomer.

The cathode electrolyte composition may include a polymerization initiator by heat or light.

The curing may be carried out by a polymerization reaction applying heat or light.

Curing is, for example, thermosetting, and can be performed by heat-treating at 40-120 degreeC.

The cathode electrolyte composition may include a polymerization initiator by heat or light.

As the thermal polymerization initiator by heat, one or more selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used.

The photopolymerization initiator by light is, for example, an acetophenone-based compound; benzophenone compounds; thioxanthone-based compounds; benzoin compounds; A triazine-based compound or the like can be used. The content of the polymerization initiator is, for example, 0.01 to 10 parts by weight, for example, 0.2 to 5 parts by weight based on 100 parts by weight of the total composition weight.

The substrate may be a release film. The substrate serves to support the cathode electrolyte composition and the like, and may include, as non-limiting examples, a polyethylene terephthalate film, a Mylar film, and the like.

According to another aspect, there is provided a composite anode for a lithium metal battery comprising the above-described cathode electrolyte.

The composite anode contains a cathode electrolyte, a cathode active material, a conductive agent, and a binder. The content of the positive electrode electrolyte is 1 to 20 parts by weight, 3 to 15 parts by weight, or 5 to 10 parts by weight based on 100 parts by weight of the composite anode. When the cathode electrolyte is in the above range, a composite anode having excellent ionic conductivity can be obtained.

Hereinafter, a method for manufacturing a composite anode according to an embodiment will be described.

A composite positive electrode can be manufactured by mixing a positive electrode active material, a conductive agent, and a binder with a positive electrolyte composition to obtain a composite positive electrode composition, and then coating and curing the composite positive electrode composition on an upper portion of a positive electrode current collector. The composite positive electrode composition may further include a solvent.

It is possible to prepare a composite positive electrode by coating the composite positive electrode composition on the upper portion of the positive electrode current collector as described above, and in addition to performing a coating and curing process on a separate support of the composite positive electrode composition and separating from the support to prepare a composite positive electrode possible.

The positive electrolyte composition comprises: a first monomer having at least two double bonds and a second monomer having one or more double bonds; lithium salt; and nitrile-based compounds.

The cathode electrolyte composition is, for example, obtained by mixing a first monomer and a second monomer to obtain a first mixture, separately mixing a lithium salt and a nitrile-based compound to prepare a second mixture, and mixing the first mixture and the second mixture It can be obtained according to the step of mixing. When the first mixture and the second mixture are mixed at a temperature of, for example, 20 to 70°C, or 30 to 65°C, a cathode electrolyte composition having a more uniform composition can be obtained.

The content of the nitrile-based compound in the positive electrolyte composition is 10 to 70 parts by weight based on 100 parts by weight of the first monomer. And the content of the lithium salt is 10 to 50 parts by weight based on 100 parts by weight of the first monomer.

The composite anode composition may include a polymerization initiator by heat or light.

The curing may be carried out by a polymerization reaction applying heat or light.

When the curing reaction is carried out by heat, the heat treatment is carried out at 40 to 120°C.

The positive active material is a lithium composite oxide, and any one commonly used in the art may be used without limitation.

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

The positive active material may be, for example, one or more of a complex oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and specific examples thereof include Li _a A _1-b B _b D ₂ (wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any one of the formulas of LiFePO _{4 may be used:}

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

Of course, a compound having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may include a coating element compound of oxide or hydroxide of the coating element, oxyhydroxide of the coating element, oxycarbonate of the coating element, or hydroxycarbonate of the coating element. The compound constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. In the coating layer forming process, any coating method may be used as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material (eg, spray coating, dipping, etc.) by using these elements in the compound. Since the content can be well understood by those engaged in the field, a detailed description thereof will be omitted.

As the cathode active material, for example, a compound represented by the following Chemical Formula 10, a compound represented by the following Chemical Formula 11, or a compound represented by the Chemical Formula 12 may be used.

[Formula 10]

Li _a Ni _b Co _c Mn _d O ₂

In Formula 10, when 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, the sum of b, c and d is 1, and b, c and d are 0 at the same time is excluded,

[Formula 11]

Li ₂ MnO ₃

[Formula 12]

LiMO ₂

In Formula 12, M is Mn, Fe, Co, or Ni.

Examples of the conductive agent include carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber; metal powder or metal fibers or metal tubes such as carbon nanotubes, copper, nickel, aluminum, and silver; Conductive polymers such as polyphenylene derivatives may be used, but are not limited thereto, and any conductive agent may be used in the art.

Examples of the binder include vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyimide, polyethylene, polyester, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), A carboxymethyl cellulose-styrene-butadiene rubber (SMC/SBR) copolymer, a styrene-butadiene rubber-based polymer, or a mixture thereof may be used. The binder is not limited thereto, and any binder that can be used as a binder in the art may be used.

As the solvent, N-methylpyrrolidone, acetone, or water may be used, but the solvent is not limited thereto and any solvent that can be used in the art may be used.

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

A lithium metal battery according to an embodiment includes a battery case including a composite positive electrode, a negative electrode, and an electrolyte interposed therebetween, and accommodating them. For example, the lithium metal battery may be manufactured by the following method.

First, a composite anode is prepared according to the above-described method.

Next, a lithium metal thin film or a lithium alloy thin film is prepared as a lithium negative electrode.

As the lithium negative electrode, a lithium metal thin film or a lithium metal alloy thin film may be used. The thickness of the lithium metal thin film or the lithium metal alloy thin film may be 100 μm or less. For example, the lithium battery may have stable cycle characteristics even with respect to a lithium metal thin film or a lithium metal alloy thin film having a thickness of 100 μm or less. For example, in the lithium battery, the thickness of the lithium metal thin film or the lithium metal alloy thin film may be 80 μm or less, for example 60 μm or less, specifically 0.1 to 60 μm.

The lithium metal battery may use an electrolyte commonly used in lithium metal batteries as an electrolyte.

In addition to the above-described electrolyte in the lithium metal battery according to an embodiment, one or more selected from a liquid electrolyte, a solid electrolyte, a gel electrolyte, and a polymer ionic liquid may be further used.

According to another embodiment, the lithium metal battery may further include a liquid electrolyte, at least one selected from a solid electrolyte, a gel electrolyte, and a polymer ionic liquid, and a separator.

The liquid electrolyte further includes at least one selected from an organic solvent, an ionic liquid, and a lithium salt. Any organic solvent can be used as long as it is commonly used in lithium metal batteries, and non-limiting examples include a carbonate-based compound, a glyme-based compound, and a dioxolane-based compound.

The gel electrolyte may be used as long as it is well known in the art as an electrolyte having a gel form.

The gel electrolyte may contain, for example, a polymer and a polymeric ionic liquid.

The polymer may be, for example, a solid graft (block) copolymer electrolyte.

An ionic liquid has a melting point below room temperature and refers to a salt in a liquid state at room temperature or a molten salt at room temperature composed of only ions. Ionic liquids are for example N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidium bis(3-trifluoromethylsulfonyl)imi de, at least one selected from the group consisting of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide am.

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

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, etc. can be used

The inorganic solid _{electrolyte, Cu 3 N, Li 3 N} , LiPON, Li 3 PO 4 .Li 2 S.SiS 2, Li 2 S.GeS 2 .Ga 2 S 3, (Na, Li) 1 + x Ti _2-x Al _x (PO ₄ ) ₃ (0.1≤x≤0.9), Li _1+x Hf _2-x Al _x (PO ₄ ) ₃ (0.1≤x≤0.9), Na ₃ Zr ₂ Si ₂ PO ₁₂ , Li ₃ Zr ₂ Si ₂ PO ₁₂ , Na ₅ ZrP ₃ O ₁₂ , Na ₅ TiP ₃ O ₁₂ , Na ₃ Fe ₂ P ₃ O ₁₂ , Na ₄ NbP ₃ O ₁₂ , NLi _0.3 La _0.5 TiO ₃ , Na ₅ MSi ₄ O ₁₂ (M is a rare earth element such as Nd, Gd, Dy) Li ₅ ZrP ₃ O ₁₂ , Li ₅ TiP ₃ O ₁₂ , Li ₃ Fe ₂ P ₃ O ₁₂ , Li ₄ NbP ₃ O ₁₂ , Li _1+x (M,Al,Ga) _x (Ge _1-y Ti _y ) _2-x (PO ₄ ) ₃ (0≤X≤0.8, 0≤Y≤1.0, M is Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm or Yb), Li _1+x+y Q _x Ti _2-x Si _y P _3-y O ₁₂ (0<x≤0.4, 0<y≤0.6, Q is Al or Ga), Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₅ La ₃ Nb ₂ O ₁₂ , Li ₅ La ₃ M ₂ O ₁₂ (M is Nb or Ta), Li _7+x A _x La _3-x Zr ₂ O ₁₂ (0<x<3, A is Zn) and the like may be used.

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

A lithium metal battery according to an embodiment contains a separator and an impregnated solid electrolyte. The impregnated solid electrolyte contains, for example, a lithium salt and an ionic liquid.

The impregnated solid electrolyte may contain a filler such as _{SiO 2} and TiO _{2 .} The content of such a filler is 1 to 20% by weight, for example, 5 to 15% by weight, based on the total weight of the impregnated solid electrolyte.

The impregnated solid electrolyte is included in the pores of the separator and may exist on the surface of the separator. The impregnated solid electrolyte has a semi-solid, gel or solid form and can be fixed, so there is no risk of leakage to the outside, unlike a liquid electrolyte.

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

As shown in FIG. 5 , a lithium metal battery 51 according to an embodiment includes a positive electrode 53 , a lithium negative electrode 52 , and an electrolyte 54 . The above-described positive electrode 53 , negative electrode 52 , and electrolyte 54 are wound or folded and accommodated in the battery case 55 . The positive electrode 53 may be a composite positive electrode containing a positive electrolyte according to an embodiment. The electrolyte 54 may be a composite electrolyte containing a separator and an impregnated solid electrolyte.

Next, the electrolyte according to an embodiment is injected into the battery case 55 and sealed with a cap assembly to complete the lithium metal battery 51 . The battery case may have a cylindrical shape, a prismatic shape, or a thin film type. For example, the lithium metal battery may be a large-sized thin-film battery. The lithium metal battery may be a lithium ion battery.

Since the lithium metal battery has excellent lifespan characteristics and high rate characteristics, it can be used in medium and large-sized devices. Examples of mid-to-large devices include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like. -bike) and an electric two-wheeled vehicle power tool power storage device including an electric scooter (E-scooter), but is not limited thereto. In addition, it can be used in fields requiring a large amount of power storage. For example, it can be used for electric bicycles, power tools, and the like.

The lithium metal battery according to an embodiment may be, for example, an all-solid-state secondary battery. Since a liquid electrolyte is not used in the lithium metal battery according to an embodiment, a composite anode having improved ion conductivity may be manufactured by using the cathode electrolyte as a medium to be responsible for the transfer path of lithium ions on the anode side as well.

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

(Preparation of anode electrolyte)

Example 1

The compound (DRIC) represented by Formula 4-1 and hexyl acrylate were mixed in a weight ratio of 5:2, and succinonitrile (SN) in which LiTFSI was dissolved in 3M was added and mixed to obtain a cathode electrolyte composition. When dissolving LiTFSI in SN, after liquefying SN in an oven at 60°C, LiTFSI was added and then dissolved. Here, i) SN dissolved in 3M LiTFSI, and ii) the total content of the compound represented by Chemical Formula 4 and hexyl acrylate are mixed in a 3:1 weight ratio, and 2,2'-azobis(2,4) as a thermal polymerization initiator -dimethylvaleronitrile) was added and mixed to obtain a cathode electrolyte composition. The content of the polymerization initiator is 0.1 parts by weight based on 100 parts by weight of the total of the compound represented by Formula 4-1 and hexyl acrylate.

<Formula 4-1>

In Formula 4-1, E is a residue derived from ethylene glycol, -(OCH ₂ CH ₂ )-, DEG is a residue derived from diethylene glycol, -(CH ₂ OCH ₂ )-, and TMP is trimethyl a residue derived from allpropane, -C(CH ₂ O)(CH ₂ CH ₃ )-, L is 5, m is 5, and n is 5.

The cathode composition was coated on a substrate using a barcoater and heat-treated at 110° C., followed by a curing reaction to prepare a cathode electrolyte with a thickness of about 100 μm. The mixing weight ratio of the crosslinked polymer of DRIC and hexyl acrylate and the liquid electrolyte (3M LiTFSI in succinonitrile (SN)) in the positive electrolyte is 1:3. And the content of the liquid electrolyte is 300 parts by weight based on 100 parts by weight of the crosslinked polymer.

Example 2

A positive electrolyte was prepared in the same manner as in Example 1, except that the thickness of the positive electrolyte was manufactured to a thickness of about 110 μm by controlling the coating gauge of the bar coater.

Comparative Example 1

The total content of SN in which LiTFSI was dissolved with 3M, the compound represented by Formula 4, and hexyl acrylate was changed in a 1:1 weight ratio and the thickness of the cathode electrolyte was controlled to about 110 μm by controlling the coating gauge of the bar coater. Except that, in the same manner as in Example 1, a cathode electrolyte was prepared.

Comparative Example 2

A positive electrolyte was prepared in the same manner as in Comparative Example 1, except that the thickness of the positive electrolyte was controlled to about 90 μm by controlling the coating gauge of the bar coater.

(Manufacture of composite anode and battery)

Example 3

A composite cathode composition was obtained by mixing the cathode electrolyte composition of Example 1, LiNi _0.8 Co _0.1 Al _0.1 O ₂ , denka black as a conductive agent, and polyvinylidene fluoride as a binder. In the composite positive electrode composition, _{the mixing weight ratio of LiNi 0.8} Co _0.1 Al _0.1 O ₂ (NCA), the conductive agent, the binder, and the positive electrolyte composition is 82.8:3.6:3.6:10.

The composite anode composition was coated on a current collector and subjected to a curing reaction through a process of heat treatment at 110° C. to prepare a composite cathode containing a cathode electrolyte to a thickness of about 100 μm. In the composite anode, the mixing weight ratio of the crosslinked polymer of DRIC and hexyl acrylate and the liquid electrolyte (3M LiTFSI in succinonitrile (SN)) is 1:3. And the content of the liquid electrolyte is 300 parts by weight based on 100 parts by weight of the crosslinked polymer.

A lithium metal battery (coin cell 2032 type) was prepared by interposing a polyethylene/polypropylene separator and an impregnated solid electrolyte between the lithium metal having a thickness of about 20 μm as the composite positive electrode and the negative electrode obtained according to the above procedure. Here, the impregnated solid electrolyte is an ionic liquid of 2.8M LiFSI, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (N-Propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide: PYR13FSI) and SiO ₂ . Here, _{the content of SiO 2} is 10% by weight based on the total weight of the impregnated solid electrolyte.

Example 4

A positive electrolyte, a composite anode and a lithium metal battery (a positive electrolyte, a composite anode and a lithium metal battery ( coin cell) was prepared.

Example 5

A positive electrolyte, a composite anode, and a lithium metal battery (coin cell) were carried out in the same manner as in Example 3, except that the content of liquid electrolyte (SN dissolved in LiTFSI 3M) was changed to 200 parts by weight based on 100 parts by weight of the crosslinked polymer. ) was prepared.

Comparative Example 3

LiNi _0.8 Co _0.1 Al _0.1 O ₂ (NCA), denka black as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a weight ratio of 92:4:4, and then N-methylpyrrolidone was mixed thereto to prepare a positive electrode composition. got it The content of N-methylpyrrolidone is 65 parts by weight based on 100 parts by weight of NCA.

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

A lithium metal battery (coin cell) was prepared by interposing a polyethylene/polypropylene separator between the lithium metal having a thickness of about 20 μm, which is the positive electrode and the negative electrode obtained according to the above procedure. Here, a liquid electrolyte was added between the positive electrode and the negative electrode. As the liquid electrolyte, an electrolyte solution in which 1M LiFOB was dissolved in a mixed solvent of FEC and DEC in a 3:7 volume ratio was used.

Comparative Example 4

The same as in Example 3, except that an electrolyte obtained by coating a polyethylene/polypropylene separator and an impregnated polymer electrolyte composition with a thickness of about 12 mm on top of a polyethylene separator having a thickness of about 17 μm was used instead of an impregnated solid electrolyte It was carried out according to the method.

Comparative Example 5

A positive electrolyte, a composite anode and a lithium metal battery (a positive electrode, a composite anode and a lithium metal battery ( coin cell) was prepared.

Comparative Example 6

A positive electrolyte, a composite anode and a lithium metal battery (coin cell) were carried out in the same manner as in Example 3, except that the content of liquid electrolyte (SN dissolved in LiTFSI 3M) was changed to 550 parts by weight based on 100 parts by weight of the crosslinked polymer. ) was prepared.

Evaluation Example 1: Ion Conductivity

The ionic conductivities of the positive electrolytes prepared according to Examples 1 and 2 and the positive electrolytes prepared according to Comparative Examples 1 and 2 were measured using a multustat analyzer manufactured by Solartron, and are shown in Table 1 below. Table 1 below shows the thickness of the cathode electrolyte.

division Mixed weight ratio of PCE and PIOB Ion Conductivity (mS/cm) Thickness of positive electrolyte (㎛) Example 1 3:1 0.53 100 Example 2 3:1 0.53 110 Comparative Example 1 1:1 0.06 110 Comparative Example 2 1:1 0.06 90

In Table 1, PCE denotes the sum of SN and lithium salt, and PIOB denotes the total of the positive electrode active material, conductive agent, and binder.

Referring to Table 1, the positive electrode electrolytes of Examples 1 and 2 had significantly increased ionic conductivity compared to the positive electrolytes of Comparative Examples 1 and 2.

In addition, the ionic conductivity of the positive electrode electrolytes prepared according to Examples 4 and 5 and the positive electrode electrolytes prepared according to Comparative Examples 5-6 was measured in the same manner as in the case of the positive electrode electrolyte of Example 1 described above.

As a result, it can be confirmed that the positive electrolytes prepared according to Examples 4 and 5 exhibited an ionic conductivity equivalent to that of the positive electrolyte of Example 1, and improved compared to the positive electrolyte prepared according to the electrolyte and Comparative Examples 5-6. could

Evaluation Example 2: Charging/discharging efficiency

The charging and discharging characteristics of the lithium metal battery of Example 3 and the lithium metal battery of Comparative Examples 3 and 4 were evaluated according to the following method.

Constant current charging was performed at 25°C with a current of 0.1C rate until the voltage reached 4.10V (vs. Li), and then cut-off was performed at a current of 0.25C rate while maintaining 4.30V in the constant voltage mode. Then, it was discharged at a constant current of 0.1C rate until the voltage reached 3.0V (vs. Li) during discharge (1 ^st cycle).

The ^{coin cell that has completed the 1st} cycle is charged with a constant current of 0.2C at 25°C until it reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C while maintaining 4.30V in the constant voltage mode. off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3V (vs. Li) during discharge (2 ^nd cycle).

After 2 ^nd cycle, the lithium battery is charged with a constant current at 25°C at a rate of 0.2C until the voltage reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.10V in the constant voltage mode (cut-off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (3 ^st cycle).

A ^{lithium battery that has undergone 3 st} cycles is charged with a constant current at 25°C at a rate of 0.2C until the voltage reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C while maintaining 4.10V in the constant voltage mode (cut-off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (4 ^st cycle).

The evaluation results of the charging and discharging characteristics are shown in Table 2 and FIGS. 2A to 2C.

Capacity (mAh) Charging/discharging efficiency (%) division charge Discharge Example 3 1.38322 1.25730 90.2 Comparative Example 3 1.04763 0.89172 85.1 Comparative Example 4 1.23265 1.09367 88.7

As shown in Table 2 and FIGS. 2A to 2C, the lithium metal battery of Example 3 had improved charge/discharge efficiency compared to Comparative Examples 3 and 4.

Evaluation Example 3: Life characteristics

The lifespan and charge/discharge efficiency characteristics of the lithium metal batteries of Example 3 and Comparative Examples 3 and 4 were evaluated as follows.

Constant current charging was performed at 25°C with a current of 0.1C rate until the voltage reached 4.10V (vs. Li), and then cut-off was performed at a current of 0.25C rate while maintaining 4.30V in the constant voltage mode. Then, it was discharged at a constant current of 0.1C rate until the voltage reached 3.0V (vs. Li) during discharge (1 ^st cycle).

The ^{coin cell that has completed the 1st} cycle is charged with a constant current of 0.2C at 25°C until it reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C while maintaining 4.30V in the constant voltage mode. off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3V (vs. Li) during discharge (2 ^nd cycle).

After 2 ^nd cycle, the lithium battery is charged with a constant current at 25°C at a rate of 0.2 C until the voltage reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.10V in the constant voltage mode (cut-off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (3 ^st cycle).

A ^{lithium battery that has undergone 3 st} cycles is charged with a constant current at 25°C at a rate of 0.2C until the voltage reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C while maintaining 4.10V in the constant voltage mode (cut-off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (4 ^st cycle).

A ^{lithium battery that has undergone 4 st} cycles is charged with a constant current at 25°C at a rate of 0.2C until the voltage reaches 4.10V (vs. Li), and then cut-off at a current of 0.05C rate while maintaining 4.10V in the constant voltage mode (cut-off). Then, it was discharged at a constant current of 0.2C rate until the voltage reached 3.0V (vs. Li) during discharge (5 ^st cycle).

The above cycle was repeated for a total of 10 cycles.

The lifespan characteristics are shown in FIGS. 3 and 4A to 4C . 4A is a photograph showing the semi-finished state of the lithium metal battery of Example 3 before assembling the battery, FIG. 4B is a photograph showing the semi-finished state of the lithium metal battery of Comparative Example 3 before assembling the battery, and FIG. 4C is the battery assembly of Comparative Example 4 This is a picture showing the state of the semi-finished product.

As shown in FIG. 4a, in the lithium metal battery of Example 3, it was found that the cathode electrolyte was clean without clumping in the cathode plate.

In contrast, in the lithium metal batteries of Comparative Examples 3 and 4, it was observed that the aluminum foil surface protruded from the block as shown in FIGS. 4B and 4C.

In addition, as shown in FIG. 3 , it was found that the lithium metal battery of Example 3 had improved lifespan characteristics and charge/discharge characteristics compared to the lithium metal battery of Comparative Example 3.

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

51: lithium metal battery 52: lithium negative electrode
53: positive electrode 54: composite electrolyte
55: battery case

Claims (15)

It is a positive electrolyte for a lithium metal battery including a lithium negative electrode,
The cathode electrolyte comprises: i) a cross-linked polymer of a first monomer having at least two double bonds and a second monomer having one or more double bonds; ii) a lithium salt; and a liquid electrolyte comprising a nitrile-based compound,
The first monomer is a compound containing at least three or more repeating units represented by the formula (1), and one selected from the group represented by the following formula (2) is bonded to both ends of the repeating unit,
The content of the liquid electrolyte is 50 to 500 parts by weight based on 100 parts by weight of the cross-linked polymer cathode electrolyte for a lithium metal battery.
[Formula 1]

,
In Formula 1, E is ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol, propoxylated alkanediol , trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxyl Lated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, propoxylate It is a residue derived from the group selected from bisphenol A and combinations thereof,
n of each repeating unit is independently an integer from 1 to 20,
[Formula 2]

,

,

,

,

,

,

,
In Formula 2, R is independently a hydrogen atom, a C1-C10 alkyl group, a C6-C20 aryl group, or a combination thereof. The cathode electrolyte for a lithium metal battery according to claim 1, wherein the first monomer is a compound represented by Formula 3 or a compound represented by Formula 3-1:
[Formula 3]

[Formula 3-1]

In Formulas 3 and 3-1, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane,
a, b and c are each independently an integer from 1 to 7, and l, m and n are each independently an integer from 1 to 20. The cathode electrolyte for a lithium metal battery according to claim 1, wherein the first monomer is a compound represented by the following formula (4) or a compound represented by formula (5):
[Formula 4]

In Formula 4, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane,
l, m and n are each independently an integer from 1 to 20,
[Formula 5]

In Formula 5, EG is a residue derived from ethylene glycol, DEG is a residue derived from diethylene glycol, TMP is a residue derived from trimethylolpropane,
l, m and n are each independently an integer from 1 to 20. The cathode electrolyte for a lithium metal battery according to claim 1, wherein the second monomer is a compound represented by the following formula (6), a compound represented by formula (7), a compound represented by formula (8), or a combination thereof.
[Formula 6]

In Formula 6, R is hydrogen, a C1-C10 alkyl group, or a C6-C20 aryl group, and L ₁ is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or its a combination, and A represents, independently of each other, a chemical bond or -CH ₂ -,
[Formula 7]

In Formula 7, L1 is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, -CH ₂ CH ₂ NHC(=O)OL ₂ , -(CH ₂ ) _k OC(=O)L ₃ , or -(CH ₂ ) _k O(=O)NH-(CH ₂ )O(C=O)(C=CH ₂ )R, or a combination thereof, R is hydrogen, C1 -C10 alkyl group or C6-C20 aryl group, k is an integer of 1 to 5;
L ₂ and L ₃ are each independently hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof,
[Formula 8]

In Formula 8, L ₁ is hydrogen, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof. The cathode electrolyte for a lithium metal battery according to claim 1, wherein the second monomer is a compound represented by the following Chemical Formula 9, pentyl acrylate, propyl acrylate, butyl acrylate, or a combination thereof.
[Formula 9]

According to claim 1, wherein the nitrile-based compound succinonitrile (succinonitrile), glutaronitrile (glutaronitrile), adiponitrile (adiponitrile), pimelonitrile (pimelonitrile), suberonitrile (suberonitrile) or a combination thereof A cathode electrolyte for a lithium metal battery comprising a. The cathode electrolyte for a lithium metal battery according to claim 1, wherein the mixing weight ratio of the first monomer and the second monomer is 95:5 to 20:80. According to claim 1, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, Li(FSO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₃ C, and LiBPh, or a combination thereof, a cathode electrolyte for a lithium metal battery. A composite cathode for a lithium metal battery comprising a cathode active material, a conductive agent, a binder, and the cathode electrolyte of any one of claims 1 to 8. The composite cathode for a lithium metal battery according to claim 9, wherein the content of the cathode electrolyte is 1 to 20 parts by weight based on 100 parts by weight of the total weight of the cathode. The composite anode of claim 9; lithium negative electrode; And electrolyte; Lithium metal battery containing. The lithium metal battery according to claim 11, wherein the lithium metal battery is an all-solid-state secondary battery. a first monomer having at least two double bonds and a second monomer having one or more double bonds; lithium salt; and applying and curing the composite positive electrode composition containing a liquid electrolyte containing a nitrile-based compound on the positive electrode current collector;
The first monomer is a compound containing at least three or more repeating units represented by the formula (1), and one selected from the group represented by the following formula (2) is bonded to both ends of the repeating unit,
The content of the liquid electrolyte is 100 to 300 parts by weight based on 100 parts by weight of the crosslinked polymer.
[Formula 1]

,
In Formula 1, E is ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, diethylene glycol, alkanediol, ethoxylated alkanediol, propoxylated alkanediol , trimethylolpropane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ditrimethylolpropane, ethoxylated ditrimethylolpropane, propoxylated ditrimethylolpropane, pentaerythritol, ethoxyl Lated pentaerythritol, propoxylated pentaerythritol, dipentaerythritol, ethoxylated dipentaerythritol, propoxylated dipentaerythritol, bisphenol A, ethoxylated bisphenol A, propoxylate It is a residue derived from the group selected from bisphenol A and combinations thereof,
n of each repeating unit is independently an integer from 1 to 20,
[Formula 2]

,

,

,

,

,

,

,
In Formula 2, R is independently a hydrogen atom, a C1-C10 alkyl group, a C6-C20 aryl group, or a combination thereof. 14. The method of claim 13, wherein the curing is carried out by heat or light,
A method of manufacturing a composite anode for a lithium metal battery, wherein the curing is carried out by heat treatment at a temperature of 40 to 120 °C. According to claim 13, wherein the nitrile-based compound is succinonitrile (succinonitrile), glutaronitrile (glutaronitrile), adiponitrile (adiponitrile), pimelonitrile (pimelonitrile), suberonitrile (suberonitrile) or a combination thereof includes,
The lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, Li(FSO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li(CF _{3 )} SO ₂ ) ₃ C, and LiBPh, or a combination thereof, a method of manufacturing a composite anode for a lithium metal battery.

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