KR20180046204A - Protected anode and Lithium battery comprising protected anode, and Preparation method of protected andoe - Google Patents

Abstract

Provided are a protective negative electrode, a lithium battery including the same, and a method for producing the protective negative electrode. To this end, the protective negative electrode comprises: a negative electrode including lithium metal; and a protective layer disposed on one side of the negative electrode. The protective layer comprises a polymer having an anionic functional group and lithium ion, and content of lithium ions in the protective layer is 0.5 to 0.99 in terms of an equivalent ratio to the anionic functional group. According to the present invention, it is possible to improve charge/discharge properties of lithium batteries.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a protective anode, a lithium battery including the same,

A lithium battery including the same, and a method of manufacturing a protective cathode.

As the markets for electric vehicles (EVs) and energy storage systems (ESS) increase as well as the portable electronic devices market such as smart phones, notebooks and cameras, there is an increasing need to develop eco-friendly large-capacity energy storage technologies have.

The lithium secondary battery was commercialized by Sony Corporation in 1992. It has excellent charge / discharge efficiency and capacity, has no memory effect, and has a low degree of natural discharge even when not in use. Thus, after commercialization, It is used as a core component. BACKGROUND ART [0002] Recently, lithium secondary batteries have been expanded to the fields where mid- to large-sized batteries such as electric vehicles, energy storage devices, and various robots are used in the field where the use of small secondary batteries such as cleaners and power tools is used.

A lithium secondary battery using a conventional carbon-based anode material has a low energy density and a low discharge capacity. Thus, cathodes for lithium secondary batteries, which provide improved energy density and capacity, have been attempted.

When the lithium metal is used as the cathode in the lithium secondary battery, the energy density per unit weight and the energy density per unit volume of the lithium secondary battery are lower than the current level due to the low density of lithium and the low oxidation and reduction potential (-3.045 V vs. SHE) Can be increased by about 3 times.

The specific surface area of the negative electrode is increased by the growth of the dendritic lithium in the electrochemical plating / stripping process of the lithium metal and the charge / discharge of the lithium metal negative electrode due to the side reaction between the lithium metal and the electrolyte and / Characteristics are poor.

Therefore, a lithium anode having improved charge / discharge characteristics is required.

One aspect is to provide a protective cathode that can provide improved charge and discharge characteristics.

Another aspect is to provide a lithium battery including the protective cathode.

Another aspect provides a method for manufacturing the protective cathode.

According to one aspect,

A negative electrode comprising a lithium metal; And

And a protective layer disposed on one surface of the cathode,

Wherein the protective layer comprises a polymer having an anionic functional group and lithium ion,

A protective negative electrode is provided in which the lithium ion content in the protective layer is 0.5 to 0.99 in terms of an equivalent ratio to the anionic functional group.

According to another aspect,

anode; A protective cathode according to any one of the preceding claims; And

There is provided a lithium battery including an electrolyte disposed between the anode and the cathode.

According to another aspect,

Preparing a second polymer powder having an anionic functional group and lithium ion;

Preparing an anionic functional group and a third polymer having at least one selected from the group consisting of sodium, potassium and hydrogen ions;

Preparing a polymer composition by adding a second polymer powder and a third polymer in an organic solvent;

And coating and drying the polymer composition on one side of the lithium negative electrode to dispose a protective layer.

According to one aspect, the charge / discharge characteristics of the lithium battery can be improved by adopting a protective negative electrode having an equivalent ratio of the lithium ion content to the corresponding anionic functional group in the polymer included in the protective layer.

1 is a scanning electron microscope (SEM) image of the protective cathode section prepared in Example 1. Fig.
2 is a scanning electron microscope (SEM) image of the protective cathode surface prepared in Example 1. Fig.
Fig. 3 shows the results of charge and discharge tests of the symmetric cell manufactured in Comparative Example 4. Fig.
4 is a graph showing the charge / discharge test results of the symmetric cell manufactured in Comparative Example 5. FIG.
FIG. 5 is a graph showing a charge / discharge test result of the symmetric cell fabricated in Example 6. FIG.
6 is a graph showing a charge / discharge test result of the symmetric cell manufactured in Example 7. FIG.
7 is a graph showing the results of charging / discharging experiments of the symmetric cell fabricated in Example 8. Fig.
8 is a graph showing a charge / discharge test result of the symmetric cell fabricated in Example 9. FIG.
9 is a graph showing the charge / discharge test results of the symmetric cell fabricated in Example 10. Fig.
10 is a graph showing the charging / discharging efficiency of the lithium battery manufactured in Example 11 and Comparative Example 7 according to charge / discharge cycles.
11 is a scanning electron microscope (SEM) image of a surface of a negative electrode after a charge and discharge test of a lithium battery manufactured in Example 11. FIG.
12 is a scanning electron microscope (SEM) image of the surface of the negative electrode after the charge and discharge test of the lithium battery manufactured in Comparative Example 7. [
13 is a schematic view of a lithium battery according to one embodiment.
Description of the Related Art
1: Lithium battery 2: cathode
3: anode 4: separator
5: Battery case 6: Cap assembly

Hereinafter, a protective cathode according to exemplary embodiments, a lithium battery including the same, and a method for manufacturing the protective cathode will be described in more detail.

The protective cathode according to one embodiment comprises a cathode comprising a lithium metal; And a protective layer disposed on one side of the cathode, wherein the protective layer comprises an anionic functional group and a polymer having lithium ion, wherein the lithium ion content in the protective layer is in the range of 0.5 to 5 equivalents relative to the anionic functional group, 0.99.

By replacing some of the total anionic functional groups contained in the protective layer in the protective electrode, for example, 0.5 to 0.99 equivalents of the counter ion of the anionic functional group with lithium ions, the protective negative electrode has excellent ionic conductivity and elastic modulus mechanical properties at the same time Thus, the charge / discharge characteristics of the lithium battery including the protective cathode can be improved.

In addition, since the protective layer in the protective cathode includes the polymer including the anionic functional group and the doped lithium ion in the above-mentioned equivalent ratio range, the anion of the electrolyte included in the lithium battery is prevented from being directly transferred to the lithium metal, Side reactions between anions can be prevented. Anionically functional groups and lithium ions uniformly distributed in the above-described equivalent ratio range in the protective layer induce a uniform current distribution on the surface of the lithium negative electrode, thereby improving the charge / discharge characteristics of the lithium battery. For example, a protective layer comprising an anionic functional group having the above-described equivalence ratio range and a polymer having a doped lithium ion prevents the depletion of local lithium ions on the surface of the lithium negative electrode, so that lithium dendrites and / The growth of dendritic lithium can be suppressed.

In a protective cathode comprising a protective layer made of an ionic polymer containing no lithium ion as a counter ion, an initial overvoltage may occur due to the initial substitution of the lithium ion of the electrolyte as an ionic polymer in the protective layer at the time of initial charge / discharge . In addition, the ionic polymer containing only lithium ion as the counter ion has a problem in that it is brittle due to the lack of flexibility and can not withstand the volume change accompanied by charging / discharging of the lithium negative electrode, It is difficult to do. On the other hand, an ionic polymer that does not contain lithium ion as a counter ion has relatively high flexibility and tensile strength as compared with an ionic polymer containing only lithium ion, so that cracks do not readily occur even when the volume of lithium is changed. In both cases, however, the mechanical properties of the lithium metal are insufficient to mechanically prevent dendritic growth.

In the protective cathode, the protective layer includes a first polymer having an anionic functional group and lithium ion, and the lithium ion content of the first polymer may be 0.55 to 0.95 in terms of an equivalent ratio to the anionic functional group. And the protective layer may include an anionic functional group-containing first polymer partially substituted with lithium ions. For example, the content of the lithium ion substituted in the first polymer may be 0.6 to 0.95 in terms of the monomer ratio to the anionic functional group. Of the total anionic functional groups included in the first polymer, the counter ion of the anionic functional group of 0.6 to 0.9 equivalents may be a lithium ion. For example, the content of lithium ion substituted in the first polymer may be from 0.65 to 0.9 in terms of the monomer ratio to the anionic functional group. For example, the content of lithium ions substituted in the first polymer may be from 0.65 to 0.85 in terms of monomer ratio to the anionic functional group. For example, the content of lithium ions substituted in the first polymer may be from 0.65 to 0.85 in terms of monomer ratio to the anionic functional group. For example, the content of the lithium ion substituted in the first polymer may be 0.7 to 0.85 in terms of the monomer ratio to the anionic functional group. For example, the content of lithium ions substituted in the first polymer may be 0.7 to 0.8 in terms of the monomer ratio to the anionic functional group. By having the protective layer containing the first polymer having such a substituted lithium metal content range, the protective cathode can simultaneously provide excellent ion conductivity and mechanical properties.

Alternatively, in the protective cathode, the protective layer comprises a second polymer and a third polymer, the second polymer has an anionic functional group and lithium ion, and the third polymer has an anionic functional group and a sodium ion, a potassium ion and a hydrogen ion And may have more than one selected. That is, it may include a mixture of an anionic functional group-containing second polymer in which the protective layer is substituted with lithium ion and an anionic functional group-containing third polymer not substituted in lithium ion. In the second polymer, the counter ions of all the anionic functional groups are replaced with lithium ions. Therefore, the content of lithium ions substituted in the second polymer is 1 in terms of an equivalent ratio to anionic functional groups. The third polymer includes an anionic functional group substituted with at least one selected from the group consisting of sodium ion, potassium ion and hydrogen ion other than lithium ion, and does not contain lithium ion.

In the protective cathode, the content of the second polymer and the third polymer included in the protective layer may be 55:45 to 95: 5 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 60:40 to 95: 5 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 60:40 to 90:10 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 65:35 to 95: 5 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 65:35 to 85:15 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 70:30 to 85:15 by weight. For example, the content of the second polymer and the third polymer included in the protective layer in the protective cathode may be 70:30 to 80:20 by weight. By having the protective layer containing the second polymer and the third polymer mixed in such a weight ratio, the protective cathode can provide both excellent ion conductivity and mechanical properties.

The anionic functional group contained in the polymer having the anionic functional group in the protective cathode is preferably one selected from a sulfonate group (-SO ₃ ^- ), a phosphate group (-PO ₄ ^2- ), and a carboxylate group (-COO ^- ) But it is not necessarily limited to these, and it is possible to use any of the anionic functional groups in the art.

The molecular weight of the polymer having anionic functional groups in the protective cathode may be 10,000 to 1,000,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be 10,000 to 500,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be 10,000 to 400,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be 10,000 to 300,000 Dalton. For example, the molecular weight of an anionic functional group-containing polymer may be 10,000 to 200,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be from 20,000 to 150,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be from 25,000 to 140,000 Dalton. For example, the molecular weight of the polymer having anionic functional groups may be 30,000 to 100,000 Dalton. The charge and discharge characteristics can be further improved in a protective negative electrode comprising an anionic functional group-containing polymer having a molecular weight in this range.

The equivalent weight of the polymer having anionic functional groups in the protective cathode may be 300 to 1,400 Dalton. The ion equivalent is defined as the weight of the polymer per anionic functional group. That is, the ion equivalent is a value obtained by dividing the molecular weight of the polymer by the number of anionic functional groups containing the polymer. For example, the equivalent weight of the polymer having anionic functional groups in the protective cathode may be 400 to 1,300 Dalton. For example, the equivalent weight of the polymer having anionic functional groups in the protective cathode may be 500 to 1,200 Dalton. For example, the equivalent weight of the polymer having anionic functional groups in the protective cathode may be 600 to 1,200 Dalton. For example, the equivalent weight of the polymer having anionic functional groups in the protective cathode may be 700 to 1,200 Dalton. For example, the equivalent weight of the polymer having anionic functional groups in the protective cathode may be 800 to 1,200 Dalton. The charge and discharge characteristics can be further improved in a protective negative electrode comprising an anionic functional group-containing polymer having an ion equivalent in such a range.

The modulus of the polymer having anionic functional groups in the protective cathode may be from 5 to 400 MPa. For example, the modulus of the polymer having anionic functional groups may be from 10 to 400 MPa. For example, the modulus of the polymer having anionic functional groups may be 20 to 350 MPa. For example, the modulus of the polymer having anionic functional groups may be 30 to 350 MPa. For example, the modulus of the polymer having anionic functional groups may be 50 to 350 MPa. The modulus may be an indentation modulus. Cracks in the protective layer can be suppressed while the strength of the protective layer is improved in a protective negative electrode comprising an anionic functional group-containing polymer having such a range of modulus. Therefore, the protective layer effectively accommodates the volume change of the lithium negative electrode, and the charge / discharge characteristics of the lithium battery can be further improved.

The modulus of the second polymer in the protective cathode may be greater than the modulus of the third polymer. The second polymer has improved modulus as compared to the third polymer, but lacks flexibility and is cracked and brittle. The third polymer is more flexible than the second polymer and can accommodate the volume change of the lithium anode without cracking. However, since the modulus is too low, it is difficult to suppress the growth of dendritic lithium on the surface of the lithium anode. Since the modulus of the second polymer in the protective layer is greater than the modulus of the third polymer, the modulus of the mixed layer can be controlled by adjusting the mixing ratio of the second polymer and the first polymer. Alternatively, the modulus of the protective layer comprising the first polymer can be controlled by adjusting the lithium content of the first polymer.

For example, in a protective cathode, a first polymer may be represented by the following formulas (1) and (2):

≪ Formula 1 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, _{and, R 1, R 2, R} 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13, R 14, R 15, and R ₁₆ Wherein A is Li, H, Na, or K, wherein the Li content in A is from 0.5 to 0.99, x is from 1 to 10, y is from 1 to 10, and z is from 1 to 10, An integer of 1000 ,

(2)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- A is Li, H, Na, or K, and the Li content in A is 0.5 to 0.99, and a + b = 1, 0 < a < 1, 0 b &lt; 1.

For example, in a protective cathode, a first polymer may be represented by the following formulas 3 to 4:

(3)

Wherein A is Li, H, Na, or K, x is an integer from 1 to 10, y is an integer from 1 to 10, and z is an integer from 1 to 1000,

&Lt; Formula 4 >

Wherein A is Li, H, Na, or K, a + b = 1, and 0 < a 1, 0 b 1.

For example, in a protective cathode, a second polymer may be represented by the following formulas 5 to 6:

&Lt; Formula 5 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, _{and, R 1, R 2, R} 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13, R 14, R 15, and R ₁₆ At least one of them contains fluorine, x is 1 to 10, y is 1 to 10, and z is an integer of 1 to 1000,

(6)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- An aryl group having 1 to 20 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms which is substituted or unsubstituted with halogen, a + b = 1, and 0 < a?

For example, in a protective cathode, a third polymer may be represented by the following formulas (7) to (8):

&Lt; Formula 7 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, and, M is H, Na, or _{K, R 1, R 2,} R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13 At least one of R ₁₄ , R ₁₅ and R ₁₆ contains fluorine, x is 1 to 10, y is 1 to 10, and z is an integer of 1 to 1000,

(8)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- Or a heteroaryl group having 2 to 20 carbon atoms which is substituted or unsubstituted with halogen and M is H, Na or K, a + b = 1, 0 < a 1, 1.

For example, in the protective cathode, the second polymer may be represented by the following formulas (9) to (10):

&Lt; Formula 9 >

Wherein x is from 1 to 10, y is from 1 to 10, and z is an integer from 1 to 1000,

&Lt; Formula 10 >

In the above formula, a + b = 1, 0 < a? 1, 0 b <1.

For example, in a protective cathode, a third polymer may be represented by the following formulas (11) to (12):

&Lt; Formula 11 >

Wherein M is H, Na, or K, x is an integer from 1 to 10, y is an integer from 1 to 10, and z is an integer from 1 to 1000,

&Lt; Formula 12 >

Wherein M is H, Na, or K, a + b = 1, and 0 < a 1, 0 b 1.

In the protective cathode, the thickness of the protective layer may be 20 占 퐉 or less. For example, the thickness of the protective layer in the protective cathode may be 0.1 to 20 占 퐉. For example, the thickness of the protective layer in the protective cathode may be 0.5 to 20 占 퐉. For example, the thickness of the protective layer in the protective cathode may be 1 to 20 占 퐉. For example, the thickness of the protective layer in the protective cathode may be between 1 and 15 mu m. For example, the thickness of the protective layer in the protective cathode may be 1 to 10 mu m. For example, the thickness of the protective layer in the protective cathode may be between 1 and 8 mu m. For example, the thickness of the protective layer in the protective cathode may be between 1 and 5 mu m. By including the protective layer in this thickness range, the protective cathode can provide improved charge-discharge characteristics. If the thickness of the protective layer is too thin, it may be difficult to effectively protect the lithium negative electrode from the electrolytic solution. If the thickness of the protective layer is too thick, the internal resistance of the protective cathode may increase and the charge / discharge characteristics of the lithium battery may be deteriorated.

In the protective cathode, the protective layer may further include at least one selected from inorganic particles and a binder. By including at least one selected from the inorganic particles and the binder, the mechanical strength, conductivity, adhesion and the like can be improved.

The inorganic particles may include at least one selected from the group consisting of metal oxides, carbon oxides, carbon-based materials and organic-inorganic composites. However, the inorganic particles are not necessarily limited to them, and if they are capable of improving ionic conductivity and mechanical strength of the electrolyte in the art Everything is possible. For example, the inorganic particles can be selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , BaTiO ₃ , MOF (Metal Organic Framework), graphite oxide, graphene oxide, POSS (Polyhedral Oligomeric Silsesquioxanes) And may be at least one selected from Li ₂ CO ₃ , Li ₃ PO ₄ , Li ₃ N, Li ₃ S ₄ , Li ₂ O, and montmorillonite.

The particle size of the inorganic particles may be less than 500 nm. For example, the particle size of the inorganic particles may be between 1 nm and 500 nm. For example, the particle size of the inorganic particles may be from 5 nm to 500 nm. For example, the particle size of the inorganic particles may be from 5 nm to 400 nm. For example, the particle size of the inorganic particles may be from 5 nm to 200 nm. For example, the particle size of the inorganic particles may be from 5 nm to 100 nm. For example, the particle size of the inorganic particles may be 50 nm to 500 nm. For example, the particle size of the inorganic particles may be 100 nm to 500 nm. For example, the particle size of the inorganic particles may be 200 nm to 500 nm. For example, the particle size of the inorganic particles may be 300 nm to 500 nm. For example, the particle size of the inorganic particles may be 400 nm to 500 nm.

The content of the inorganic particles in the protective cathode may be 1 to 95% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 5% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 10% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 30% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be more than 30% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 35% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 40% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 45% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 50% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 55% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. For example, the content of the inorganic particles may be 60% by weight to 90% by weight based on the total weight of the inorganic particles and the anionic functional group-containing polymer. The mechanical properties of the protective layer can be further improved in such an inorganic particle content range. The anionic functional group-containing polymer contained in the protective layer can be attached to the surface of the inorganic particles.

The inorganic particles may be porous. For example, the inorganic particles may be mesoporous particles. For example, the inorganic particles may include a shape in which specific inorganic particles such as Al ₂ O ₃ and SiO ₂ described above are porous.

As the binder, the same binder as that used in the production of the electrode of the lithium battery described below may be used.

The protective layer may additionally comprise a lithium salt. By further including the lithium salt in the protective layer, the ion conductivity of the protective layer can be further improved. The lithium salt further including the protective layer may be the same as the lithium salt contained in the organic electrolyte of the lithium battery described later. The content of the lithium salt in addition to the protective layer may be 1 to 10 parts by weight based on 100 parts by weight of the polymer containing the anionic functional group. Lithium in the lithium salt, which is simply added to the protective layer, is distinguished from lithium doped with counter ions of anionic functional groups in the polymer.

A lithium battery according to another embodiment includes a positive electrode; The protective cathode described above; And an electrolyte disposed between the anode and the cathode.

A lithium battery including a protective cathode can be made as follows.

First, a protective cathode comprising a cathode containing a lithium metal and a protective layer is prepared.

The lithium metal thin film can be used as the negative electrode containing lithium metal as it is. Alternatively, the negative electrode containing lithium metal may include a current collector and a negative electrode active material layer disposed on the current collector. For example, a negative electrode containing a lithium metal may be used as a counter electrode disposed on a conductive substrate where a lithium metal thin film is a current collector. The lithium metal thin film can form an integrated body with the current collector.

In the negative electrode containing lithium metal, the current collector may be any one selected from the group consisting of stainless steel, copper, nickel, iron and cobalt, but is not limited thereto. If the metallic substrate is a conductive material which can be used in the art Everything is possible. For example, the current collector may be a conductive oxide substrate, a conductive polymer substrate, or the like. The current collector may have various structures such as a structure in which the entire substrate is made of a conductive material, a form in which a conductive metal, a conductive metal oxide, and a conductive polymer are coated on one surface of an insulating substrate. The current collector may be a flexible substrate. Therefore, the current collector can be easily bent. Further, after bending, the current collector may be easily restored to its original shape.

Further, the negative electrode containing lithium metal may further include a negative electrode active material in addition to lithium metal. The negative electrode containing lithium metal may be an alloy of a lithium metal and another negative active material, a composite of a lithium metal and another negative active material, or a mixture of a lithium metal and another negative active material.

Other negative electrode active materials that can be added to the negative electrode containing lithium metal include, for example, at least one selected from the group consisting of lithium-alloyable metals, transition metal oxides, non-transition metal oxides, and carbon-based materials .

For example, the metal that can be alloyed with lithium is at least one selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, and Sb Si-Y alloys (Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Or a combination thereof and not Si), Sn-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element or a combination element thereof, And so on. The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Se, Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0 <x <2), or the like.

For example, the carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in amorphous form, plate form, flake form, spherical form or fiber form, and the amorphous carbon may be soft carbon or hard carbon, Mesophase pitch carbide, calcined coke, and the like.

A protective layer is disposed on a negative electrode containing lithium metal.

The protective layer may be prepared using a composition comprising a polymer having an anionic functional group.

For example, after a composition comprising a polymer having an anionic functional group is prepared, a protective negative electrode is obtained by coating directly on a negative electrode containing lithium metal, or an anionic functional group cast on a separate support and peeled off from the support Containing polymer film is laminated on a negative electrode containing lithium metal to obtain a protective negative electrode. The protective cathode is not limited to those listed above and may be any other form that can be used in the art. For example, the protective cathode can be produced by printing an anionic functional group-containing polymer composition ink on a negative electrode containing a lithium metal by an ink jet method or the like.

A composition comprising an anionic functional group may be prepared by separately preparing a second polymer powder having an anionic functional group and a lithium metal, a third polymer having an anionic functional group and at least one selected from sodium ion, potassium ion and hydrogen ion, These can be prepared by mixing in an organic solvent. Alternatively, a composition comprising a polymer having an anionic functional group is prepared by dissolving a first polymer powder having an anionic functional group and a lithium ion, wherein the lithium ion content is 0.55 to 0.95 in terms of an equivalent ratio to an anionic functional group, in an organic solvent . The type of the organic solvent used in the composition containing the anionic functional group-containing polymer is not particularly limited and dimethylacetamide, dimethylsulfoxide and the like can be used.

A more detailed description of the manufacturing method of the protective cathode will be given in the protective cathode manufacturing method section which will be described later.

Next, an anode is prepared.

A cathode active material composition, a conductive material, a binder and a solvent are mixed to prepare a cathode active material composition. The positive electrode active material composition is directly coated on the aluminum current collector and dried to produce a positive electrode plate in which the positive electrode active material layer is formed. Alternatively, the cathode active material composition may be cast on a separate support, and then a film obtained by peeling from the support may be laminated on the aluminum current collector to produce a cathode plate having a cathode active material layer.

The cathode active material is a lithium-containing metal oxide, and any of those conventionally used in the art can be used without limitation. For example, at least one of complex oxides of metal and lithium selected from cobalt, manganese, nickel, and combinations thereof may be used. Specific examples thereof include Li _a A _1-b B _b D ₂ In the formula, 0.90? A? 1.8, and 0? B? 0.5); Li _a E _1-b B _b O _{2 -c} D _c wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05; LiE (in the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05) 2-b B b O 4-c D c; Li _a Ni _{1 -bc} Co _b B _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _{2 -?} F _? Wherein? 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? Li _a Ni _{1- b c} Co _b B _c O _2-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 _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, 0 <? 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 wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8, and 0.001? B? 0.1); Li _a CoG _b O ₂ wherein, in the above formula, 0.90? A? 1.8, and 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 wherein, in the above formula, 0.90? A? 1.8, and 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); In the formula of LiFePO ₄ may be used a compound represented by any one:

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

For example, LiCoO ₂ , LiMn _x O ₂ x (x = 1, 2), LiNi _1-x Mn _x O _2x (0 <x <1), Ni _1-xy Co _x Mn _y O ₂ ? 0.5, 0? Y? 0.5), LiFePO _4, or the like can be used.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise an oxide, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a coating element compound of the hydroxycarbonate of the coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be any coating method as long as it can coat the above compound by a method that does not adversely affect physical properties of the cathode active material (for example, spray coating, dipping, etc.) by using these elements, It will be understood by those skilled in the art that a detailed description will be omitted.

As the conductive material, metal powders such as acetylene black, ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers and the like can be used. Polyphenylene derivatives, and the like can be used alone or in admixture of one or more. Any conductive material can be used as long as it can be used as a conductive material in the technical field of the present invention.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, and styrene butadiene rubber-based polymers. But are not limited to, and may be used as long as they can be used as binders in the art.

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

The content of the cathode active material, the conductive material, the binder and the solvent is a level commonly used in a lithium battery. Depending on the use and configuration of the lithium battery, one or more of the conductive material, the binder, and the solvent may be omitted.

Next, a separator to be disposed between the positive electrode and the negative electrode is prepared.

The separator can be used as long as it is conventionally used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fibers, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) or a combination thereof, in the form of a nonwoven fabric or a woven fabric. For example, a rewindable separator such as polyethylene, polypropylene or the like may be used for the lithium ion battery. For example, a separator having excellent ability to impregnate an organic electrolyte can be used for a lithium ion polymer battery. A separator having an excellent ability to impregnate an organic electrolyte can be produced by the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition may be coated directly on the electrode and dried to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support may be laminated on the electrode to form a separator.

The polymer resin that can be used in the production of the separator is not particularly limited, and all the materials used for the binder of the electrode plate can be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, or a mixture thereof may be used.

Next, a liquid electrolyte is prepared.

For example, an organic electrolytic solution is prepared. The organic electrolytic solution can be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be any organic solvent that can be used in the art. Examples of the solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, vinylethylene carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, But are not limited to, furan, gamma -butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, Examples of the solvent include ethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methyl isopropyl carbonate, succinonitrile, diethyl glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethyl glycol dimethyl ether, polyethyl glycol dimethyl ether, ethyl propyl carbonate, Propyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether or the like A mixture thereof.

Lithium salts may also be used as long as they can be used in the art as lithium salts. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , _x F _{2x + 1} SO 2) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

For example, as shown in FIG. 13, the lithium battery 1 includes an anode 3, a cathode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 described above are wound or folded and housed in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and is sealed with a cap assembly 6 to complete the lithium battery 1. Although not shown in the drawing, an electrolyte layer including a composite electrolyte is formed on the cathode 2. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium battery may be a thin film battery. The lithium battery may be a lithium ion battery.

Alternatively, a separator is disposed between the positive electrode and the negative electrode to form a battery structure, the battery structure is laminated in a bi-cell structure, the battery is impregnated with the organic electrolyte, and the resulting product is received in the pouch and sealed. do.

A plurality of battery structures are stacked to form a battery pack, and such a battery pack can be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle (EV), and the like.

The lithium battery is not limited to a lithium ion battery or a lithium polymer battery, and may include a lithium air battery, a lithium total solid battery, and the like.

According to another embodiment, there is provided a method of manufacturing a protective cathode, comprising: preparing a second polymer powder having an anionic functional group and lithium ion; Preparing an anionic functional group and a third polymer having at least one selected from the group consisting of sodium ions, potassium ions and hydrogen ions; Preparing a polymer composition by adding a second polymer powder and a third polymer in an organic solvent; And coating and drying the polymer composition on one side of the lithium negative electrode to dispose the protective layer.

First, in preparing the second polymer powder having an anionic functional group and lithium ion, lithium hydroxide (LiOH) or the like is added to an aqueous solution selectively containing an alcohol including a third polymer containing an anionic functional group, A solution containing a second polymer can be prepared by replacing a proton of a polymer with a lithium metal ion. The solvent may be removed from the solution containing the second polymer to prepare the second polymer powder.

A third polymer including a hydrogen ion, a sodium ion, and a potassium ion as a counter ion of an anionic functional group in the step of preparing an anionic functional group and a third polymer having at least one selected from sodium ion, potassium ion and hydrogen ion They may be obtained commercially or used as they are or may be prepared separately.

In the step of preparing the polymer composition by adding the second polymer powder and the third polymer to the organic solvent, the second and third polymers may be added in the organic solvent to prepare the polymer composition. The content of the polymer in the polymer composition may be 10 wt% or less.

In the step of coating and drying the polymer composition on one side of the lithium anode and arranging the protective layer, side reactions with the lithium metal can be suppressed by including the organic solvent in the polymer composition. The polymer composition containing an aqueous solution can not be applied to a lithium metal.

On the other hand, a protective film can be prepared by coating a polymer composition on a separate support and drying the polymer film to prepare a polymer film, and then disposing the polymer film on the lithium cathode.

Further, after the protective layer is disposed on one surface of the negative electrode, a step of rolling and bonding the protective layer and the negative electrode may be further included. Rolling may be performed by applying heat and pressure.

Alternatively, the method for preparing a protective cathode comprises preparing a first polymer powder having an anionic functional group and a lithium metal, wherein the lithium metal content is in the range of 0.55 to 0.95 in terms of an equivalent ratio to the anionic functional group; Preparing a polymer composition by adding a first polymer powder to an organic solvent; And disposing the polymer composition on one surface of the lithium negative electrode and drying to form a protective layer. Further, after the protective layer is disposed on one surface of the negative electrode, a step of rolling and bonding the protective layer and the negative electrode may be further included.

In the present specification, a substituent is derived by replacing one or more hydrogen ions with other atomic ions or functional groups in an unsubstituted mother group. Unless otherwise stated, when a functional group is considered "substituted ", it is meant that the functional group is an alkyl group having 1 to 40 carbon atoms, an alkenyl group having 2 to 40 carbon atoms, an alkynyl group having 2 to 40 carbon atoms, An alkyl group, a cycloalkenyl group having 3 to 40 carbon atoms, and an aryl group having 7 to 40 carbon atoms. When a functional group is described as "optionally substituted ", it is meant that the functional group may be substituted with the substituent described above.

In the present specification, a and b of "carbon number a to b" mean the carbon number of a specific functional group. That is, the functional group may include a carbon atom from a to b. For example, "alkyl group of 1 to 4 carbon atoms" is an alkyl group having from 1 to 4 carbon atoms, _{i.e., CH 3 -, CH 3 CH} 2 -, CH 3 CH 2 CH 2 -, (CH 3) 2 CH-, CH ₃ CH ₂ CH ₂ CH ₂ -, CH ₃ CH ₂ CH (CH ₃ ) - and (CH ₃ ) ₃ C-.

Nomenclature for a particular radical may include mono-radical or di-radical depending on the context. For example, if a substituent requires two points of attachment to the remaining molecule, the substituent should be understood as a diradical. For example, a particular substituent group requiring two connecting points comprises a di-radical, such as _{-CH 2-, -CH 2 CH 2-,} -CH 2 CH (CH 3) CH 2-,. Other radical nomenclature such as "akylene" clearly indicates that the radical is a di-radical.

As used herein, the term "alkyl group" or "alkylene group" refers to a branched or unbranched aliphatic hydrocarbon group. In one embodiment, the alkyl group may be substituted or unsubstituted. The alkyl group includes alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, But are not necessarily limited thereto, and each of them may be optionally substituted or unsubstituted. In one embodiment, the alkyl group may have from 1 to 6 carbon atoms. For example, the alkyl group having 1 to 6 carbon atoms may be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, hexyl and the like.

As used herein, the term "alkenyl group" refers to a hydrocarbon group containing from 2 to 20 carbon atoms including at least one carbon-carbon double bond and includes an ethenyl group, a 1-propenyl group, Butenyl, 2-butenyl, cyclopropenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, and the like. In one embodiment, the alkenyl group may be substituted or unsubstituted. In one embodiment, the alkenyl group may have from 2 to 40 carbon atoms.

As used herein, the term "alkynyl group" refers to a hydrocarbon group containing from 2 to 20 carbon atoms including at least one carbon-carbon triple bond and includes an ethynyl group, a 1-propynyl group, a 1-butynyl group, But are not limited to these. In one embodiment, the alkynyl group may be substituted or unsubstituted. In one embodiment, the alkynyl group may have from 2 to 40 carbon atoms.

As used herein, the term "cycloalkyl group" means a fully saturated carbocycle ring or ring system. Means, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl.

As used herein, the term "aromatic" refers to a ring or ring system having a conjugated pi electron system and includes a carbon ring aromatic (e.g., phenyl) and a heterocyclic aromatic (e.g., pyridine) . The term includes monocyclic rings or fused polycyclic rings (i.e., rings that share adjacent pairs of atoms) if the whole ring system is aromatic.

As used herein, the term "aryl group" refers to an aromatic ring in which the ring backbone contains only carbon, a ring system (i.e., two or more fused rings sharing two adjacent carbon atoms) Wherein the ring is a single bond, -O-, -S-, -C (= O) -, -S (= O) _2- , -Si (Ra) (Rb) - (Ra and Rb are, C10 alkyl group), an alkylene group having 1 to 10 carbon atoms which is substituted or unsubstituted with halogen, or -C (= O) -NH-. If the aryl group is a ring system, then each ring in the system is aromatic. For example, the aryl group includes, but is not limited to, a phenyl group, a biphenyl group, a naphthyl group, a phenanthrenyl group, a naphthacenyl group, and the like. The aryl group may be substituted or unsubstituted.

The term "arylene group" as used herein is an aryl group requiring two or more connecting points. The tetravalent arylene group is an aryl group requiring four connecting points, and the divalent arylene group is an aryl group requiring two connecting points. For example, -C ₆ H ₅ -OC ₆ H ₅ -.

As used herein, the term "heteroaryl group" refers to a single ring, a plurality of fused rings, or a plurality of rings wherein a single bond is replaced by a single bond, -O-, -S-, -C (= O) O) ₂ -, -Si (Ra) (Rb) - (Ra and Rb are independently of each other an alkyl group having 1 to 10 carbon atoms), an alkylene group having 1 to 10 carbon atoms, O) -NH-, and at least one ring atom is not a carbon, i. E., A heteroatom. In the fused ring system, one or more heteroatoms may be present in only one ring. In the fused ring system, one or more heteroatoms may be present in only one ring. For example, heteroatoms include, but are not necessarily limited to, oxygen, sulfur and nitrogen. For example, heteroaryl groups include furanyl, thienyl, imidazolyl, quinazolinyl, quinolinyl, isoquinolinyl, quinolinyl, quinolinyl, But are not limited to, quinoxalinyl, pyridinyl, pyrrolyl, oxazolyl, indolyl, and the like.

The term "heteroarylene group" as used herein is a heteroaryl group requiring two or more connecting points. The tetravalent heteroarylene group is a heteroaryl group requiring four connecting points, and the divalent heteroarylene group is a heteroaryl group requiring two connecting points.

The term "aralkyl group" and "alkylaryl group" used herein mean an aryl group connected as an substituent group via an alkylene group, such as an aralkyl group having 7 to 14 carbon atoms, Phenylpropyl group, naphthylalkyl group, and the like. In one embodiment, the alkylene group is a lower alkylene group (i.e., an alkylene group having from 1 to 4 carbon atoms).

As used herein, a "cycloalkenyl group" is a carbocycle ring or ring system having one or more double bonds, which is an aromatic ring-free ring system. For example, a cyclohexenyl group.

As used herein, a "heterocyclyl group" is a non-aromatic ring or ring system comprising at least one heteroatom in the ring skeleton.

As used herein, "halogen" is a stable element belonging to Group 17 of the Periodic Table of the Elements, for example, fluorine, chlorine, bromine or iodine, in particular fluorine and / or chlorine.

The weight average molecular weights of the first to third polymers are measured by GPC (Gel Permeation Chromatography) on a polystyrene standard sample.

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

(Preparation of protective cathode)

Example 1: Li-Nafion: H-Nafion = 80: 20

1.0 equivalent of LiOH aqueous solution was added to the sulfonic acid in an equivalent ratio to Nafion ^® solution (Aldrich, ~ 5% water / alcohol mixed solution, equivalent weight 1000 to 1100 g / Nafion is a -SO ₃ H 1 equivalent of -SO ₃ H to prepare a lithium ion-containing Nafion solution was replaced with -SO ₃ Li.

The solvent was removed from the lithium ion-containing Nafion solution to obtain a lithium ion-containing Nafion powder.

Lithium ion containing Nafion powder and Nafion ^® solution (Aldrich, ~ 5% water / alcohol mixed solution) were added to the DMAc (dimethylacetamide) solvent to prepare a mixed solution having a Nafion content of 5%.

In the mixed solution, the weight ratio of non-supported nafion to lithium ion containing nafion was 80:20.

The mixed solution was coated on a lithium foil using a micrometer bladder and vacuum dried to prepare a protective negative electrode coated with a protective layer having a thickness of about 3 mu m on the lithium metal.

1 and 2 show scanning electron microscope (SEM) images of a cross section and a surface of a protective cathode coated with a protective layer.

Example 2: Li-Nafion: H-Nafion = 60: 40

A protective cathode was prepared in the same manner as in Example 1, except that the weight ratio of non-supported nafion to lithium ion containing nafion was changed to 60:40 in the mixed solution.

Example 3: Li-Nafion: H-Nafion = 40: 60

A protective cathode was prepared in the same manner as in Example 1, except that the weight ratio of non-supported nafion to lithium ion-containing naphion was changed to 40:60 in the mixed solution.

Example 4: Li-Nafion: H-Nafion = 20: 80

A protective negative electrode was prepared in the same manner as in Example 1, except that the weight ratio of non-supported nafion to lithium ion containing nafion was changed to 20:80 in the mixed solution.

Example 5: Addition of Li-Nafion: H-Nafion = 80: 20 and inorganic particles

A protective cathode was prepared in the same manner as in Example 1, except that 25 parts by weight of Al ₂ O ₃ (particle diameter: 480 nm) as inorganic particles was further added to 100 parts by weight of Nafion in the mixed solution.

Comparative Example 1: Li foil

Lithium foil was used as the negative electrode.

Comparative Example 2: Li-Nafion: H-Nafion = 0: 100

A protective negative electrode was prepared in the same manner as in Example 1 except that only unsupported nafion was used in the mixed solution and no lithium ion containing nafion was added.

Comparative Example 3: Li-Nafion: H-Nafion = 100: 0

A protective negative electrode was prepared in the same manner as in Example 1, except that only the Nafion containing lithium ion was used in the mixed solution and the non-supported Nafion was not added.

(Preparation of Li symmetric cell)

Example 6

The protective cathode and the lithium foil prepared in Example 1 were used as a first electrode and a second electrode, respectively. A polypropylene separator (Celgard 3510) was disposed between the first and second electrodes, and 1.0 M LiPF _A symmetric cell was prepared using a liquid electrolyte dissolved in a 1: 1 volume ratio mixed solvent of ethylene carbonate (EC): diethyl carbonate (DEC).

Examples 7 to 10

A symmetric cell was prepared in the same manner as in Example 6 except that the protective negative electrode prepared in Examples 2 to 5 was used.

Comparative Examples 4 to 6

A symmetric cell was prepared in the same manner as in Example 6, except that the protective negative electrode prepared in Comparative Examples 1 to 3 was used.

(Preparation of pull cell)

Example 11

A mixture of LiCoO ₂ powder and Super-P (Timcal Ltd.) was uniformly mixed at a weight ratio of 90: 5 and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a mixture of active material: carbon conductive material: Lt; RTI ID = 0.0 &gt; wt / 5 &lt; / RTI &gt;

The prepared slurry was coated on an aluminum substrate (thickness: 15 mu m) using a doctor blade, dried under reduced pressure at 120 DEG C, rolled by a roll press to form a sheet, and a positive electrode was prepared.

A glass fiber separator (Whatman, CAT No. 1823-047) was disposed between the anode prepared above and the protective cathode prepared in Example 1, and a liquid electrolyte was injected to prepare a coin cell. The protective cathode was disposed such that the protective layer was opposed to the positive electrode.

The liquid electrolyte is a solution in which 1.0 M LiPF ₆ is dissolved in a 1: 1 volume ratio mixed solvent of ethylene carbonate (EC): diethyl carbonate (DEC).

Examples 12 to 15

Full-cell was prepared in the same manner as in Example 11, except that the protective negative electrode prepared in Examples 2 to 5 was used.

Comparative Examples 7 to 9

Except that the protective negative electrode prepared in Comparative Examples 1 to 3 was used.

Evaluation Example 1: Evaluation of electrochemical stability

A plating / stripping cycle was repeatedly performed using the current density of 1 mA / cm &lt; ² &gt; for the symmetric cells prepared in Examples 6 to 10 and Comparative Examples 4 to 6, 9 respectively

During the repetitive plating / stripping cycle using the current density of 1 mA / cm &lt; ² &gt; for the symmetric cells prepared in Comparative Example 4, Comparative Example 5 and Examples 6 to 10, The changes are shown in Figs. 3 to 9, respectively.

The time required per one plating / elution cycle was 2 hours.

As shown in FIG. 3, the symmetric cell of Comparative Example 4 including a lithium foil anode without a protective layer became unstable after 470 hours.

As shown in FIG. 4, the symmetric cell of Comparative Example 5 including a protective anode having a protective layer made of unsupported Nafion became unstable after about 250 hours. The stability of the symmetric cell of Comparative Example 5 was lower than that of the symmetric cell of Comparative Example 4. [

5 to 8, the symmetric cells of Examples 6 to 9 including the protective cathode in which the protective layer simultaneously containing the lithium-containing Nafion and the unsubstituted Nafion were disposed showed a Stable voltage behavior and low overvoltage. In particular, as shown in FIG. 5, the voltage of the symmetric cell of Example 6 was stable up to about 800 hours, and the overvoltage was also low.

9, the symmetric cell of Example 10 including a protective cathode having a protective layer simultaneously containing lithium-containing Nafion and unsubstituted Nafion and Al ₂ O ₃ inorganic particles was subjected to a voltage And the overvoltage was also low.

Evaluation example  2: Full cell Charging and discharging  Experiment

The full cells prepared in Examples 11 to 15 and Comparative Examples 7 to 9 were charged and discharged at a constant current of 0.65 mA / cm &lt; ² &gt; at a voltage of 3.0 to 4.2 V relative to lithium metal at room temperature (25 DEG C) . Some of the results of charge-discharge experiments are shown in Fig.

FIG. 10 shows the charge / discharge test results of the lithium battery in Example 11 and Comparative Example 7. FIG.

FIG. 10 shows the Coulomb efficiency of the lithium battery according to charge / discharge cycles. Coulomb efficiency is calculated from the following equation (1).

&Quot; (1) &quot;

Coulomb efficiency (%) = [n ^th cycle discharge capacity / n ^th cycle charge capacity] × 100

As shown in FIG. 10, the lithium battery of Example 11 including a protective negative electrode showed no significant change in charging / discharging efficiency up to 800 cycles.

On the contrary, the lithium battery of Comparative Example 7 including the lithium foil anode having no protective layer continuously decreased the charge-discharge efficiency as the cycle was increased.

Further, as shown in Fig. 11, the growth of dendrid and / or dendritic lithium was confirmed on the surface of lithium metal in the lithium battery of Comparative Example 7. On the other hand, as shown in FIG. 12, it was confirmed that the lithium battery of Example 11 maintained a relatively uniform negative electrode surface.

Therefore, in the lithium battery of Example 11, the protective layer of the protective cathode suppresses the growth of dendrite or dendritic lithium on the surface of the lithium metal, thereby suppressing the decomposition of the electrolyte on the surface of the negative electrode. .

On the other hand, in the lithium battery of Comparative Example 7, since the dendrite or the dendritic lithium continuously grows on the surface of the lithium metal, the decomposition of the electrolyte solution on the surface of the negative electrode is accelerated, do.

Claims (20)

A negative electrode comprising a lithium metal; And
And a protective layer disposed on one surface of the cathode,
Wherein the protective layer comprises a polymer having an anionic functional group and lithium ion,
Wherein the lithium ion content in the protective layer is 0.5 to 0.99 in terms of an equivalent ratio to the anionic functional group. The protective cathode according to claim 1, wherein the protective layer comprises a first polymer having an anionic functional group and lithium ion, and the lithium ion content in the first polymer is 0.55 to 0.95 in terms of an equivalent ratio to an anionic functional group. The method of claim 1, wherein the protective layer comprises a second polymer and a third polymer, the second polymer has an anionic functional group and lithium ion, and the third polymer is selected from anionic functional groups and sodium, A protective cathode having one or more of the following: The protective cathode according to claim 3, wherein the second polymer and the third polymer have a weight ratio of 55:45 to 95: 5. The protective cathode according to claim 1, wherein the anionic functional group is at least one selected from a sulfonate group (-SO ₃ ^- ), a phosphate group (-PO ₄ ^- ), and a carboxylate group (-COO ^- ). The protective cathode according to claim 1, wherein the polymer has a molecular weight of 10,000 to 1,000,000 Dalton. The protective cathode according to claim 1, wherein an equivalent weight of the polymer is 300 to 1,400 Dalton. The protective cathode according to claim 1, wherein a modulus of the polymer is 5 to 400 MPa. The protective cathode according to claim 4, wherein the modulus of the second polymer is larger than the modulus of the third polymer. The protective cathode according to claim 2, wherein the first polymer is represented by the following general formulas (1) and (2):
&Lt; Formula 1 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, _{and, R 1, R 2, R} 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13, R 14, R 15, and R ₁₆ Wherein A is Li, H, Na, or K, wherein the Li content in A is from 0.5 to 0.99, x is from 1 to 10, y is from 1 to 10, and z is from 1 to 10, An integer of 1000 ,
(2)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- A is Li, H, Na, or K, and the Li content in A is 0.5 to 0.99, and a + b = 1, 0 < a &lt; 1, 0 b < 1. The protective cathode according to claim 2, wherein the first polymer is represented by the following general formulas (3) to (4):
(3)

Wherein A is Li, H, Na, or K, x is an integer from 1 to 10, y is an integer from 1 to 10, and z is an integer from 1 to 1000,
&Lt; Formula 4 >

Wherein A is Li, H, Na, or K, a + b = 1, and 0 < a 1, 0 b 1. 4. The protective cathode according to claim 3, wherein the second polymer is represented by the following general formulas (5) to (6):
&Lt; Formula 5 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, _{and, R 1, R 2, R} 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13, R 14, R 15, and R ₁₆ At least one of them contains fluorine, x is 1 to 10, y is 1 to 10, and z is an integer of 1 to 1000,
(6)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- An aryl group having 1 to 20 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms which is substituted or unsubstituted with halogen, a + b = 1, and 0 < a? 4. The protective cathode according to claim 3, wherein the third polymer is represented by the following general formulas (7) to (8):
&Lt; Formula 7 >

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ is independently selected from the group consisting of hydrogen, halogen, alkyl of 1 to 10 carbon atoms, unsubstituted or substituted with halogen, alkenyl of 2 to 10 carbon atoms, unsubstituted or substituted with halogen, A cycloalkyl group having 5 to 10 carbon atoms which is substituted or unsubstituted with halogen, an aryl group having 6 to 20 carbon atoms which is substituted or unsubstituted with halogen, or a heteroaryl group having 2 to 20 carbon atoms, and, M is H, Na, or _{K, R 1, R 2,} R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, R 12, R 13 At least one of R ₁₄ , R ₁₅ and R ₁₆ contains fluorine, x is 1 to 10, y is 1 to 10, and z is an integer of 1 to 1000,
(8)

Wherein R ₁₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ , R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ , R ₂₉ , R ₃₀ , R ₃₁ , R ₃₂ , R _{33 , R 34, R 35, R} 36, R 37, R 38, R 39, and R ₄₀ independently represent hydrogen, a halogen, a halogen substituted or unsubstituted carbon alkyl group of hydrogen from 1 to 10, a halogen substituted or unsubstituted A substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted C6-C10 cycloalkyl group, a substituted or unsubstituted C6- Or a heteroaryl group having 2 to 20 carbon atoms which is substituted or unsubstituted with halogen and M is H, Na or K, a + b = 1, 0 < a 1, 1. 4. The protective cathode according to claim 3, wherein the second polymer is represented by the following general formulas (9) to (10):
&Lt; Formula 9 >

Wherein x is from 1 to 10, y is from 1 to 10, and z is an integer from 1 to 1000,
&Lt; Formula 10 >

In the above formula, a + b = 1, 0 < a? 1, 0 b <1. The protective cathode according to claim 3, wherein the third polymer is represented by the following general formula (11) to (12):
&Lt; Formula 11 >

Wherein M is H, Na, or K, x is an integer from 1 to 10, y is an integer from 1 to 10, and z is an integer from 1 to 1000,
&Lt; Formula 12 >

Wherein M is H, Na, or K, a + b = 1, and 0 < a 1, 0 b 1. The protective cathode according to claim 1, wherein the thickness of the protective layer is 20 占 퐉 or less. The protective cathode according to claim 1, wherein the protective layer further comprises at least one selected from inorganic particles and a binder. 18. The method of claim 17, wherein the inorganic particles are selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , BaTiO ₃ , MOF (Metal Organic Framework), graphite oxide, graphene oxide, Wherein the protective cathode comprises at least one selected from the group consisting of silsesquioxanes, Li ₂ CO ₃ , Li ₃ PO ₄ , Li ₃ N, Li ₃ S ₄ , Li ₂ O, montmorillonite. anode; A protective cathode according to any one of claims 1 to 18; And
And an electrolyte disposed between the anode and the cathode. Preparing a second polymer powder having an anionic functional group and lithium ion;
Preparing an anionic functional group and a third polymer having at least one selected from the group consisting of sodium, potassium and hydrogen ions;
Preparing a polymer composition by adding a second polymer powder and a third polymer in an organic solvent;
Applying the polymer composition on one surface of a lithium negative electrode and drying the negative electrode active material to form a protective layer.

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