KR20220086727A - Electrode composite sheet, all-solid-state battery using the same, and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an electrode composite sheet in which the thickness of the electrode composite is formed while uniformly distributing components constituting the electrode composite, an all-solid-state battery using the same, and a manufacturing method thereof. The present invention provides an electrode composite sheet for an all-solid-state battery comprising a metal foil current collector and an electrode composite formed in multiple layers by coating a slurry on the metal foil current collector.

Description

Electrode composite sheet, all-solid-state battery using same, and manufacturing method thereof

The present invention relates to an all-solid-state battery, and more particularly, to an electrode composite sheet having a more uniform and thick electrode composite, an all-solid-state battery using the same, and a manufacturing method thereof.

As the demand for electric vehicles and large-capacity power storage devices increases, various batteries have been developed to satisfy them.

Lithium secondary batteries have been widely commercialized because of their excellent energy density and output characteristics among various secondary batteries. As a lithium secondary battery, a lithium secondary battery (hereinafter referred to as a 'liquid-type secondary battery') including a liquid-type electrolyte containing an organic solvent is mainly used.

However, in the liquid type secondary battery, the liquid electrolyte is decomposed by the electrode reaction, causing the battery to expand, and the risk of ignition due to leakage of the liquid electrolyte is pointed out. In order to solve the problems of the liquid-type secondary battery, a lithium secondary battery (hereinafter referred to as an 'all-solid-state battery') to which a solid electrolyte having excellent stability is applied is attracting attention.

Solid electrolytes can be divided into oxide-based and sulfide-based electrolytes. Since sulfide-based solid electrolytes have high lithium ion conductivity and are stable over a wide voltage range compared to oxide-based solid electrolytes, sulfide-based solid electrolytes are mainly used as solid electrolytes for all-solid-state batteries.

In order to achieve high energy density of such an all-solid-state battery, a technique for uniformly manufacturing and thickening an electrode composite composed of an active material, a solid electrolyte, a conductive material, and a binder is important.

However, when the electrode composite is manufactured by the slurry mixing coating method of the conventional lithium ion battery method, there is a limit to forming a thick electrode composite while uniformly distributing the components constituting the electrode composite.

Unexamined Patent Publication No. 2019-0079135 (2019.07.05.)

Accordingly, an object of the present invention is to provide an electrode composite sheet in which the thickness of the electrode composite is formed while uniformly distributing the components constituting the electrode composite, an all-solid-state battery using the same, and a manufacturing method thereof.

In order to achieve the above object, the present invention is a metal foil current collector; And it provides an electrode composite sheet for an all-solid-state battery comprising a; and an electrode composite formed in multiple layers by coating the slurry on the metal foil current collector.

The slurry includes an active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

The electrode composite includes a plurality of unit electrode composites stacked on the metal foil current collector.

In the plurality of unit electrode composites, the content of the sulfide-based solid electrolyte included in the unit electrode composite may decrease as it rises upward from the metal foil current collector.

The plurality of unit electrode composites may have a thinner thickness as they rise upward from the metal foil current collector.

The electrode composite may include: a first unit electrode composite formed by coating a first slurry on the metal foil current collector; and a second unit electrode composite formed by coating a second slurry on the first unit electrode composite.

The first slurry may have a higher content of the sulfide-based solid electrolyte than the second slurry, and the first unit electrode composite may have a greater thickness than the second unit electrode composite.

The present invention also provides an all-solid-state battery comprising the electrode composite sheet.

And the present invention provides a method of manufacturing an electrode composite sheet for an all-solid-state battery comprising; forming an electrode composite in a multi-layer by coating the slurry on a metal foil current collector in multiple layers.

When the electrode composite sheet according to the present invention forms an electrode composite by applying sludge on a metal foil current collector, by forming a unit electrode composite in multiple layers through multiple coatings, the thickness of the electrode composite can be thickened.

Since the unit electrode composite is formed to have a relatively thin thickness compared to the electrode composite, the active material, the sulfide-based solid electrolyte, the conductive material, and the binder can be uniformly distributed in the unit electrode composite. By stacking such a unit electrode composite to form an electrode composite, components constituting the electrode composite can be uniformly distributed in the electrode composite.

As described above, the electrode composite sheet according to the present invention can maximize the thickness of the electrode composite and smoothly secure the conduction channels of ions and electrons, thereby contributing to high energy density of the all-solid-state battery.

The multi-layered unit electrode composite forming the electrode composite according to the present invention has a concentration gradient by varying the ratios of the active material, the sulfide-based solid electrolyte, the conductive material and the binder, thereby improving the performance of the all-solid-state battery. That is, in the electrode composite, the performance of the all-solid-state battery can be improved by decreasing the content of the sulfide-based solid electrolyte contained in the unit electrode composite from the bottom to the top.

1 is a cross-sectional view showing an electrode composite sheet for an all-solid-state battery according to the present invention.
2 is a flowchart illustrating a method for manufacturing an electrode composite sheet for an all-solid-state battery according to the present invention.
3 is a photograph showing an energy dispersive spectroscopy (EDS) mapping result for a scanning electron microscope (SEM) image of an electrode composite according to Comparative Example 1. Referring to FIG.
4 is a photograph showing the EDS mapping result for the SEM image of the electrode composite according to Example 1.
5 is a photograph showing the EDS mapping result for the SEM image of the electrode composite according to Example 2.

It should be noted that, in the following description, only parts necessary for understanding the embodiments of the present invention will be described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to their ordinary or dictionary meanings, and the inventors have appropriate concepts of terms to describe their invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in Accordingly, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application It should be understood that there may be variations and variations.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a cross-sectional view showing an electrode composite sheet for an all-solid-state battery according to the present invention.

Referring to Figure 1, the electrode composite sheet 100 for an all-solid-state battery according to the present invention is a metal foil current collector 10, and a multi-coating slurry on the metal foil current collector 10 to form a multi-layered electrode composite 20. includes

The metal foil current collector 10 may be made of a metal material having good electrical conductivity. Aluminum, copper, etc. may be used as a metal material.

And the electrode composite 20 is formed in multiple layers by coating the slurry multiple times.

The slurry includes an active material, a sulfide-based solid electrolyte, a conductive material, and a binder. The active material, the sulfide-based solid electrolyte, the conductive material and the binder are mixed and slurried using a non-polar solvent.

Sulfide-based solid electrolytes are L _a M _b P _c S _d X _e (L=alkali metal, M=B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Cr , comprising at least one of Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, and W, where X=F, Cl, Br, I and O, 0≤a≤12, 0≤b≤6, 0≤c≤6, 0≤d≤12, 0≤e≤9). Meanwhile, the sulfide-based solid electrolyte may be a plurality of crystalline solid electrolytes, a plurality of amorphous sulfide-based solid electrolytes, or a mixture thereof. For example, as the sulfide-based solid electrolyte, Li ₁₀ GeP ₂ S ₁₂ , Li ₆ PS ₅ Cl, Li ₂ SP ₂ S ₅ solid solution, etc. may be used.

The conductive material is not particularly limited as long as it is a conductive material used in a battery. For example, as the conductive material, conductive carbon such as graphene, carbon nanotubes, Ketjen black, activated carbon, super p carbon in powder form, Denka in rod form, or vapor grown carbon fiber (VGCF) may be used.

As the binder, a high molecular compound of a fluorine-based, diene-based, acryl-based, or silicone-based polymer may be used. For example, the binder may be nitrile butadiene rubber (NBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyimide, or the like.

The electrode composite 20 includes a plurality of unit electrode composites 21 and 23 stacked on the metal foil current collector 10 .

Each of the plurality of unit electrode composites 21 and 23 may be formed of the same slurry or a slurry having different component ratios. For example, the content of the sulfide-based solid electrolyte included in the unit electrode composites 21 and 23 may decrease as the plurality of unit electrode composites 21 and 23 go up from the metal foil current collector 10 . In addition, the plurality of unit electrode composites 21 and 23 may have a thinner thickness as they rise upward from the metal foil current collector 10 .

This electrode composite 20 is a first unit electrode composite 21 formed by coating the first slurry on the metal foil current collector 10, and the second slurry is formed on the first unit electrode composite 21 by coating A second unit electrode composite 23 may be included. In this case, the content of the sulfide-based solid electrolyte may be higher in the first slurry than in the second slurry. The first unit electrode composite 21 may have a thickness greater than that of the second unit electrode composite 23 .

Meanwhile, although the present invention discloses an example in which the electrode composite 20 includes two unit electrode composites 21 and 23 , it may include three or more unit electrode composites.

As described above, when the electrode composite sheet 100 according to the present invention is formed by applying sludge on the metal foil current collector 10 to form the electrode composite 20, the unit electrode composites 21 and 23 are multilayered through multiple coatings. By forming, the thickness of the electrode composite 20 can be formed to be thick.

Since the unit electrode composites 21 and 23 can be formed to have a relatively thin thickness compared to the electrode composite 20 , the active material, the sulfide-based solid electrolyte, the conductive material and the binder are uniformly formed in the unit electrode composites 21 and 23 . can be distributed evenly. By stacking these unit electrode composites 21 and 23 to form the electrode composite 20 , components constituting the electrode composite 20 can be uniformly distributed in the electrode composite 20 .

The electrode composite sheet 100 according to the present invention can maximize the thickness of the electrode composite 20 and smoothly secure conduction channels of ions and electrons, thereby contributing to high energy density of the all-solid-state battery.

The multi-layered unit electrode composites 21 and 23 forming the electrode composite 20 according to the present invention have a concentration gradient by varying the ratio of the active material, the sulfide-based solid electrolyte, the conductive material, and the binder, so that the performance of the all-solid-state battery can improve That is, in the electrode composite 20, the performance of the all-solid-state battery can be improved by decreasing the content of the solid electrolyte included in the unit electrode composites 21 and 23 from the bottom to the top.

A method of manufacturing the electrode composite sheet 100 for an all-solid-state battery according to the present invention will be described with reference to FIGS. 1 and 2 as follows. Here, Figure 2 is a flow chart according to the manufacturing method of the electrode composite sheet 100 for an all-solid-state battery according to the present invention.

The method for manufacturing the electrode composite sheet 100 for an all-solid-state battery according to the present invention includes the steps (S10, S20) of forming the electrode composite 20 in multiple layers by coating the slurry on the metal foil current collector 10 in multiple layers.

Here, the step (S10, S20) of forming the electrode composite 20 in a multilayer is a step of coating the first slurry on the metal foil current collector 10 to form the first unit electrode composite 21 (S10), and the first The method may include coating the second slurry on the one-unit electrode composite 21 to form the second unit electrode composite 23 ( S20 ).

The loading level of the first and second unit electrode composites 21 and 23 may be 40 mg/cm ² or more.

Since the electrode composite sheet 100 according to the present invention can realize a capacity per area of 5 mAh/cm ² , the all-solid-state battery including the electrode composite sheet 100 according to the present invention can realize ultra-high energy density.

[Comparative Examples and Examples]

In order to confirm the physical and electrochemical properties of the electrode composite sheet prepared by the manufacturing method of the present invention, electrode composite sheets according to Comparative Examples and Examples were prepared. In order to confirm the electrochemical characteristics, electric charge/discharge evaluation was performed.

Here, the preparation of the electrode composite sheet according to Comparative Examples and Examples was performed in a glove box or dry room not exposed to moisture.

As a cathode active material, LiNbO ₃ surface-coated Li(Ni _0.6 Co _0.2 Mn _0.2 )O ₂ was used. Li ₆ PS ₅ Cl (LPSCL) as a sulfide-based solid electrolyte, conductive carbon as a conductive material, and butadiene rubber as a binder were used. A slurry was prepared by mixing the slurry using a non-polar solvent that did not react with the sulfide-based solid electrolyte.

Then, the slurry was applied on the carbon-coated aluminum foil current collector to prepare an electrode composite. At this time, by adjusting the coating gap of the blade, the coating thickness of the slurry and the loading level (mg/cm ² ) were controlled.

Comparative Example 1

The mixed slurry was applied with a coating gap of 450 μm on the blade, and an electrode composite sheet was prepared in Comparative Example 1 including an electrode composite having a loading level of 48 mg/cm ² and a thickness of about 270 μm. The electrode composite sheet according to Comparative Example 1 was coated with a slurry in a single coating method to form an electrode composite.

Example 1

A first unit electrode composite was formed by first coating and drying the mixed slurry with a blade coating gap of 250 μm. Next, the mixed slurry with a blade coating gap of 200 μm was applied and dried a second time on the first unit electrode composite to prepare an electrode composite sheet according to Example 1 including a second unit electrode composite.

The electrode composite sheet according to Example 1 also includes an electrode composite having a loading level of 48 mg/cm ² and a thickness of about 270 μm in the same manner as in Comparative Example 1. The electrode composite according to Example 1 has a structure in which first and second unit electrode composites are stacked, and the slurry forming the first and second unit electrode composites is the same.

Example 2

A first unit electrode composite was formed by first coating and drying the mixed slurry with a blade coating gap of 250 μm. Next, the mixed slurry with a blade coating gap of 200 μm was applied and dried a second time on the first unit electrode composite to prepare an electrode composite sheet according to Example 2 including a second unit electrode composite.

At this time, the ratio of the active material, the sulfide-based solid electrolyte, the conductive material and the binder of the primary slurry and the secondary slurry was different. That is, the ratio of the sulfide-based solid electrolyte of the primary slurry is higher than the ratio of the solid electrolyte of the secondary slurry.

The electrode composite sheet according to Example 2 also includes an electrode composite having a loading level of 48 mg/cm ² and a thickness of about 270 μm, similar to Comparative Examples 1 and 1. The electrode composite according to Example 2 has a structure in which the first and second unit electrode composites are stacked, and the ratio of the sulfide-based solid electrolyte in the slurry forming the first and second unit electrode composites is different.

In order to evaluate the battery characteristics of the electrode composite prepared in this way, an all-solid-state battery was manufactured using a dedicated pressure cell. The prepared electrode composite sheet was used as the positive electrode. The sulfide-based solid electrolyte layer was used by pressing the powdered sulfide-based solid electrolyte layer into pellets. A lithium-indium alloy was used as the counter electrode. Table 1 below shows the results of evaluating the constant current charge/discharge characteristics at a rate of 0.05 C at room temperature of 25°C. In Table 1, "single coating" indicates the coating method of Comparative Example 1 in which the electrode composite was prepared by one slurry coating. "Multiple coating" refers to the coating method of Example 1, in which an electrode composite was prepared by multiple coatings with the same slurry. "Concentration gradient multiple coating" refers to the coating method of Example 2, in which an electrode composite was prepared by multiple coatings with slurries having different ratios of sulfide-based solid electrolytes.

Produce L/L
(mg/cm2) Initial discharge capacity
(mAh/g) capacity per area
(mAh/cm2) Initial charging and discharging efficiency
(%) Comparative Example 1 single coating 48.4 153.7 5.20 70.8 Example 1 multiple coatings 48.2 165.2 5.56 74.8 Example 2 Concentration Gradient Multiple Coatings 49.9 168.3 6.30 75.2

Referring to Table 1, as compared to the electrode composite according to Comparative Example 1, it can be confirmed that the electrode composite according to Example 1 exhibits high initial discharge capacity and initial charge/discharge efficiency. This is considered to be because the positive electrode active material, the sulfide-based solid electrolyte, the conductive material and the binder in the positive electrode are properly mixed and uniformly dispersed by the multi-coating effect, so that the conduction channels of ions and electrons are properly formed.

It can be seen that the electrode composite according to Example 2 exhibits high initial discharge capacity and initial charge/discharge efficiency, as compared with the electrode composites according to Comparative Examples 1 and 1 . It can be confirmed that the thicker the electrode, the more important factor is uniform dispersion through proper mixing of the positive electrode active material, the sulfide-based solid electrolyte, the conductive material and the binder in the layer with a thickness of several hundred μm. In addition, it is expected that the electrode composite prepared through the concentration gradient multiple coating as in Example 2 can maximize the performance of the all-solid-state battery.

3 is a photograph showing an energy dispersive spectroscopy (EDS) mapping result for a scanning electron microscope (SEM) image of an electrode composite according to Comparative Example 1. Referring to FIG. 4 is a photograph showing the EDS mapping result for the SEM image of the electrode composite according to Example 1. And FIG. 5 is a photograph showing the EDS mapping result for the SEM image of the electrode composite according to Example 2.

Here, FIGS. 3 to 5 show the dispersion state of the positive electrode active material, the sulfide-based solid electrolyte and the conductive material through elemental analysis after cross-section processing of the electrode composites according to Comparative Example 1, Example 1 and Example 2 was observed through an electron microscope. Show the analysis results.

3 to 5, compared to the electrode composite of a single coating method according to Comparative Example 1, the electrode composites according to Examples 1 and 2 prepared through multiple coatings and concentration gradient multiple coatings have good dispersibility It can be seen that indicates

As such, the electrode composites according to Comparative Examples 1, 1 and 2 were formed to have the same thickness, but the electrode composites according to Examples 1 and 2 formed by a multi-coating method showed better electrical properties than Comparative Example 1. can check that

In addition, the electrode composite according to Examples 1 and 2 is not limited thereto. When the electrode composite is formed by a multi-coating method, good electrical properties can be provided while being thicker than the electrode composite according to Comparative Example 1.

On the other hand, the embodiments disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

10: metal foil current collector
20: electrode complex
21: first unit electrode composite
23: second unit electrode complex
100: electrode composite sheet

Claims (12)

metal foil current collector; and
an electrode composite formed in multiple layers by multiple coating the slurry on the metal foil current collector;
Electrode composite sheet for an all-solid-state battery comprising a. According to claim 1,
The slurry is an electrode composite sheet for an all-solid-state battery, characterized in that it comprises an active material, a sulfide-based solid electrolyte, a conductive material and a binder. 3. The method of claim 2,
The electrode composite sheet is an electrode composite sheet for an all-solid-state battery, characterized in that it includes a plurality of unit electrode composites stacked on the metal foil current collector. The method of claim 3, wherein the plurality of unit electrode composites,
The electrode composite sheet for an all-solid-state battery, characterized in that the content of the sulfide-based solid electrolyte contained in the unit electrode composite decreases as it rises upward from the metal foil current collector. The method of claim 4, wherein the plurality of unit electrode composites,
An electrode composite sheet for an all-solid-state battery, characterized in that the thickness increases as it goes up from the metal foil current collector. According to claim 2, wherein the electrode composite,
a first unit electrode composite formed by coating a first slurry on the metal foil current collector; and
a second unit electrode composite formed by coating a second slurry on the first unit electrode composite;
Electrode composite sheet for an all-solid-state battery comprising a. 7. The method of claim 6,
The electrode composite sheet for an all-solid-state battery, characterized in that the first slurry has a higher content of sulfide-based solid electrolyte than the second slurry, and the first unit electrode composite has a thickness greater than that of the second unit electrode composite. An all-solid-state battery comprising the electrode composite sheet according to any one of claims 1 to 7. forming an electrode composite in multiple layers by multiple coating the slurry on a metal foil current collector;
A method of manufacturing an electrode composite sheet for an all-solid-state battery comprising a. 10. The method of claim 9,
The slurry is an all-solid-state battery electrode composite sheet, characterized in that it comprises an active material, a sulfide-based solid electrolyte, a conductive material, a binder, and a non-polar solvent. 11. The method of claim 10, wherein the step of forming the electrode composite in the multi-layer,
forming a first unit electrode composite by coating a first slurry on the metal foil current collector; and
forming a second unit electrode composite by coating a second slurry on the first unit electrode composite;
A method of manufacturing an electrode composite sheet for an all-solid-state battery, comprising: 12. The method of claim 11,
The method of manufacturing an electrode composite sheet for an all-solid-state battery, characterized in that the first slurry has a higher content of sulfide-based solid electrolyte than the second slurry, and the first unit electrode composite has a thickness greater than that of the second unit electrode composite.

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