WO2019139397A1 - Cathode slurry composition, cathode manufactured using same, and battery including same - Google Patents

Abstract

The present invention provides: a cathode slurry composition comprising a cathode active material, a binder, alcohol, and water, wherein the content of the alcohol is 0.1 to 10 wt%, based on the total weight of the composition; an electrode manufactured using same; and a battery including the electrode. The slurry composition for manufacture of a cathode according to the present invention has advantages in that: the dispersibility of a cathode active material and a conductive material is greatly improved; the surface roughness of an electrode is reduced; and the curling tendency of the electrode is significantly reduced. In addition, the slurry composition has an economic advantage in that there is no need to use a dispersant or the usage thereof can be significantly reduced.

Description

A positive electrode slurry composition, a positive electrode prepared using the same and a battery including the same

This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0003656, filed on January 11, 2018, and Korean Patent Application No. 10-2019-0003703, filed on January 11, 2019, All of which are incorporated herein by reference.

The present invention relates to a positive electrode composition, a positive electrode prepared using the same, and a battery comprising the same.

As the application fields of energy storage technology extend to mobile phones, tablets, laptops and camcorders, electric vehicles (EV) and hybrid electric vehicles (HEV), research and development of electrochemical devices for energy storage Is increasing.

In particular, the development of secondary batteries such as lithium-sulfur batteries capable of charging and discharging has become a focus of attention. In recent years, research and development on the design of new electrodes and batteries have been carried out in order to improve the capacity density and specific energy of secondary batteries. .

Lithium-sulfur (Li-S) batteries have a high energy density and are becoming popular as next-generation secondary batteries that can replace lithium-ion batteries. Generally, a lithium-sulfur battery includes a positive electrode containing a sulfur-carbon composite as an electrode active material, a negative electrode including a lithium metal or a lithium alloy, and a separator interposed between the positive electrode and the separator.

The positive electrode of such a lithium-sulfur battery is generally prepared by coating a positive electrode slurry on a metal foil. The positive electrode slurry includes a positive electrode active material for storing energy, a conductive material for imparting electrical conductivity, (PVdF) is mixed with a solvent such as water and NMP (N-methyl pyrrolidone).

In the positive electrode slurry, the dispersibility of the positive electrode active material and / or the conductive material significantly affects the processability of the electrode and the characteristics of the electrode formed thereby. Therefore, various methods for improving the dispersibility of the cathode active material and / or the conductive material in the cathode slurry have been studied.

For example, Korean Patent Publication No. 10-2015-0025665 discloses a positive electrode active material, a conductive material, a binder, a dispersant and an aqueous solvent, wherein the dispersant includes a main chain of ionic characteristics and a side chain of nonionic surfactant characteristic Quot; positive electrode slurry for a secondary battery "

However, as disclosed in the above patent documents, the use of a separate dispersant makes the manufacturing process of the electrode complicated and increases the manufacturing cost of the electrode, which is not economically preferable.

Therefore, there is a need for research on a method for improving the dispersibility of a cathode active material and / or a conductive material without using a separate dispersant.

[Prior Art Literature]

[Patent Literature]

Korean Patent Publication No. 10-2015-0025665

The present invention has been conceived to overcome the above-described problems of the prior art, and an object of the present invention is to provide a positive electrode manufacturing slurry which significantly improves the dispersibility of the positive electrode active material and the conductive material, reduces roughness of the electrode surface, And to provide a composition.

Another object of the present invention is to provide a slurry composition for cathode preparation, which has excellent dispersibility without using a separate dispersant and suppresses curling of the electrode, thereby having an advantage in a battery manufacturing process.

It is another object of the present invention to provide a positive electrode of a battery made of the slurry composition for preparing a positive electrode and a battery including the positive electrode.

In order to achieve the above object,

A positive electrode slurry composition comprising a positive electrode active material, a binder, an alcohol and water, wherein the content of the alcohol is 0.1 to 10% by weight based on the total weight of the composition.

Further, according to the present invention,

A positive electrode prepared by applying the positive electrode slurry composition of the present invention onto a current collector is provided.

Further, according to the present invention,

The positive electrode of the present invention;

A negative electrode comprising lithium metal or a lithium alloy as a negative electrode active material;

A separator provided between the anode and the cathode; And

And an electrolyte.

The slurry composition for preparing an anode of the present invention greatly improves the dispersibility of the cathode active material and the conductive material, reduces the roughness of the electrode surface, and significantly reduces the curling of the electrode. It also provides economic advantages in that no dispersant is used or usage is greatly reduced.

The battery including the positive electrode prepared from the slurry composition for positive electrode production provides the effect of greatly improving the capacity, lifetime characteristics, and economical efficiency.

Fig. 1 is a photograph showing the electrode curling state of the electrodes of Examples 5 to 8 and Comparative Examples 4 and 5 confirmed by Test Example 1. Fig.

Hereinafter, the present invention will be described in detail.

The present invention relates to a positive electrode slurry composition comprising a positive electrode active material, a binder, an alcohol and water, wherein the content of the alcohol is 0.1 to 10% by weight based on the total weight of the composition.

The present inventors have paid attention to the reason why the positive electrode active material and the conductive material of the battery do not mix well with a binder or water having a high polarity in an aqueous slurry. That is, materials having extremely low polarity are used as the cathode active material and the conductive material, so that they do not mix well with the polar binder or water in the aqueous slurry. Accordingly, the present invention provides a solution to the above problem. That is, in the present invention, the technical feature is to improve the dispersibility of carbon and sulfur particles having low polarity by adding an alcohol solvent having an amphipathic nature. Since the alcohol solvent evaporates during the drying process and does not remain in the electrode, it does not increase the weight of the electrode and does not increase the resistance, so that the energy density of the electrode does not decrease.

As the alcohol aqueous solution, a C1-C5 lower alcohol aqueous solution may be used. In the case of alcohol having a too low vapor pressure, the solid content in the slurry may be reduced during the slurry production due to the rapid evaporation rate. In the case of alcohol having a too high vapor pressure, the drying speed is slow, have. Of the C1-C5 lower alcohol aqueous solutions, an aqueous propanol solution is more preferably used. This is because the aqueous solution has a vapor pressure similar to that of water at a temperature range of 20 to 80 ° C. at which the slurry preparation and the electrode drying proceed, so that the dispersion effect due to the evaporation of alcohol during slurry production and the possibility of a change in solid content in the slurry are small, This is preferable because it can be applied without greatly changing the electrode drying process. Examples of the aqueous propanol solution include 1-propanol aqueous solution.

In the present invention, the alcohol may be contained in an amount of 0.1 to 10% by weight, more preferably 1 to 7% by weight based on the total weight of the composition.

When the content of the aqueous alcohol solution contained in the positive electrode slurry composition is within the range described above, the dispersibility of the positive electrode active material and / or the conductive material is greatly improved, the roughness of the electrode surface is reduced, do. Particularly, when the electrode is dried during manufacturing of the electrode, cracks may be generated in the electrode during the process of manufacturing the battery, or the electrode may be removed from the current collector, so that the process age and cost are increased. The improvement provides significant advantages in the electrode manufacturing process.

When the content of the alcohol is less than 0.1% by weight, it is difficult to expect the above-mentioned objective effect. If the content of the alcohol is more than 10% by weight, the solubility of the binder in alcohol is lowered, .

The positive electrode slurry composition may include, but is not limited to, 10-78 wt% of a positive electrode active material, 1-50 wt% of a binder, 0.1-10 wt% of an alcohol, and residual water, based on the total weight of the composition.

The composition may further comprise 0.1 to 10% by weight of a conductive material.

The positive electrode slurry composition of the present invention may contain alcohol in an amount of 2 to 45 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the positive electrode active material and the conductive material.

The positive electrode slurry composition of the present invention may contain 0.1-15 wt% of alcohol and 85-99.9 wt% of water based on the total weight of alcohol and water, more preferably 0.5-10 wt% of alcohol % Of water and 90 to 99.5% by weight of water, more preferably 1 to 7% by weight of alcohol, and 93 to 99% by weight of water.

When the content ratio of the alcohol contained in the positive electrode slurry composition satisfies the respective ranges described above, the dispersibility of the positive electrode active material and / or the conductive material is greatly improved, the roughness of the electrode surface is reduced, . Particularly, when the electrode is dried during manufacturing of the electrode, cracks may be generated in the electrode during the process of manufacturing the battery, or the electrode may be removed from the current collector, so that the process age and cost are increased. The improvement provides significant advantages in the electrode manufacturing process.

The positive electrode slurry composition of the present invention has a very excellent dispersibility of the positive electrode active material and / or the conductive material without using a dispersant.

The positive electrode slurry composition of the present invention can be preferably used for producing a positive electrode of a lithium-sulfur battery. At this time, as the cathode active material, a sulfur-carbon composite may be preferably used.

In addition,

And a positive electrode prepared by applying the positive electrode slurry composition of the present invention onto a current collector.

As the current collector, those known in the art may be used, and the method of manufacturing the positive electrode may be performed according to a known method.

The positive electrode of the present invention provides a very good effect on the energy density of the electrode.

In addition,

The positive electrode of the present invention;

A negative electrode comprising lithium metal or a lithium alloy as a negative electrode active material;

A separator provided between the anode and the cathode; And

And an electrolyte.

The battery may be a lithium-sulfur battery.

As for the positive electrode, the above-described contents can be directly applied.

As the negative electrode of the battery of the present invention, a negative electrode known in the art as a negative electrode containing lithium metal or a lithium alloy as the negative electrode active material can be used without limitation.

As the lithium alloy, lithium and an alloy of a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn may be used as the negative electrode active material.

The separator positioned between the positive and negative electrodes separates or insulates the positive and negative electrodes from each other and enables lithium ion transport between the positive and negative electrodes. The separator may be made of a porous nonconductive or insulating material, but is not limited thereto, Separators known in the art can be used.

The separator may be an independent member such as a film, or may be a coating layer added to the anode and / or the cathode. The material of the separator includes, for example, a polyolefin such as polyethylene and polypropylene, a glass fiber filter paper, and a ceramic material, but is not limited thereto. The thickness of the separator is about 5 탆 to about 50 탆, Lt; / RTI >

As the electrolyte, those known in the art may be used, and for example, an electrolyte including a lithium salt and an organic solvent may be used. The electrolyte may be impregnated into a negative electrode, a positive electrode and a separator.

As the organic solvent contained in the electrolyte, for example, a single solvent or a mixed organic solvent of two or more may be used. When two or more mixed organic solvents are used, at least one solvent may be selected from two or more of the weak polar solvent group, the strong polar solvent group, and the lithium metal protective solvent group. Wherein said weak polar solvent is defined as a solvent having a dielectric constant of less than 15 that is capable of dissolving a sulfur element in an aryl compound, bicyclic ether, or acyclic carbonate, said strong polar solvent being selected from the group consisting of bicyclic carbonates, sulfoxide compounds, A lithium metal protective solvent is defined as a solvent having a dielectric constant higher than 15 that is capable of dissolving lithium polysulfide in a compound, a ketone compound, an ester compound, a sulfate compound, or a sulfite compound, and the lithium metal protective solvent is a saturated ether compound, an unsaturated ether compound, , A cyclic compound having a cyclic efficiency of not less than 50% to form a stable SEI (Solid Electrolyte Interface) on a lithium metal such as a heterocyclic compound containing O, S, or a combination thereof.

Specific examples of the weak polar solvent include xylene, dimethoxyethane, 2-methyltetrahydrofuran, diethyl carbonate, dimethyl carbonate, toluene, dimethyl ether, diethyl ether, diglyme and tetraglyme. However, the present invention is not limited thereto.

Specific examples of the strong polar solvent include hexamethyl phosphoric triamide,? -Butyrolactone, acetonitrile, ethylene carbonate, propylene carbonate, N-methylpyrrolidone, 3-methyl- But are not limited to, zolyidone, dimethylformamide, sulfolane, dimethylacetamide, dimethylsulfoxide, dimethylsulfate, ethylene glycol diacetate, dimethylsulfite, ethylene glycol sulfite and the like.

Specific examples of the lithium protecting solvent include tetrahydrofuran, ethylene oxide, dioxolane, 3,5-dimethylisoxazole, furan, 2-methylfuran, 1,4-oxane and 4-methyldioxolane. But is not limited thereto.

The battery may be constructed by applying techniques known in the art, except for the characteristic features of the present invention described above.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as set forth in the appended claims. Such changes and modifications are intended to be within the scope of the appended claims.

Example 1: Preparation of slurry composition for cathode preparation

Sulfur (product of sigma-aldrich) and CNT (carbon nanotube) were mixed and heat-treated at 155 ° C to prepare a sulfur-carbon composite. VGCF (vapor-grown carbon fiber) was used as the conductive material. As the binder, a solution of 3% aqueous solution of two kinds of polyacrylic acids (sigma Aldrich product having a molecular weight of 450,000 and 1,250,000 5: 2 weight ratio) completely neutralized with lithium hydroxide (Sigma-aldrich product) was used. The above-described sulfur-carbon composite, conductive material, and binder solution were mixed in an aqueous 1-propanol solution to prepare a slurry composition for producing a positive electrode. The ratio of the solid content: solvent (1-propanol and water) in the weight ratio was 23:77, the content of 1-propanol in the slurry was 1: 0.77% by weight

Example 2: Preparation of slurry composition for cathode preparation

A slurry composition for preparing a cathode was prepared in the same manner as in Example 1, except that the content of 1-propanol in the slurry in Example 1 was 3.85 wt%.

Example 3: Preparation of slurry composition for cathode preparation

A slurry composition for preparing a positive electrode was prepared in the same manner as in Example 1, except that the content of 1-propanol in the slurry was changed to 7.7% by weight in Example 1.

Example 4: Preparation of slurry composition for cathode preparation

In Example 1, ethanol was used instead of 1-propanol in the slurry, and a slurry composition for preparing a cathode was prepared in the same manner as in Example 1, except that the content of ethanol was 3.85 wt%.

Comparative Example 1: Preparation of a slurry composition for preparing an anode

A slurry composition for preparing a positive electrode was prepared in the same manner as in Example 1, except that water was used in place of the 1-propanol aqueous solution as the solvent in Example 1.

Comparative Example 2: Preparation of slurry composition for cathode preparation

The sulfur-carbon composite material, the conductive material and the binder used in Comparative Example 1 were further mixed with a dispersant (PVA poly vinyl alcohol) so that the ratio was 87: 5: 7: 1 by weight, and the ratio of solid content: water was 25 : ≪ / RTI > 75 by weight.

Comparative Example 3: Preparation of slurry composition for cathode preparation

A slurry composition for preparing a cathode was prepared in the same manner as in Example 1, except that the content of 1-propanol in the slurry was changed to 11.55 wt% in Example 1. However, since the solubility of the binder deteriorated, the viscosity of the slurry was increased to such an extent that mixing could not be performed, and the slurry could not be normally produced.

Example 5: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Example 1 was coated on an aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Example 6: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Example 2 was coated on an aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Example 7: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Example 3 was coated on an aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Example 8: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Example 4 was coated on an aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Comparative Example 4: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Comparative Example 1 was coated on the aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Comparative Example 5: Preparation of positive electrode

The slurry composition for preparing an anode prepared in Comparative Example 2 was coated on an aluminum current collector at 11.4 mg / cm ² to prepare a positive electrode.

Examples 9 to 12 and Comparative Examples 6 to 7: Manufacture of batteries

Each of the positive electrodes prepared in Examples 5 and 8 and Comparative Examples 4 and 5; A lithium foil having a thickness of about 45 mu m as a cathode; 1 M LiTFSI and 1 wt% LiNO ₃ in an ether solvent; And 20 micron polyolefin as a separator were used in Examples 9 to 12 and Comparative Examples 6 and 7 Lithium-sulfur secondary A battery was prepared. Specific details are shown in Table 1 below.

battery	Used anode
Example 9	Example 5 Preparation Anode (prepared as the slurry of Example 1 (using 0.77 wt% of 1-propanol)
Example 10	Example 6 Production anode (prepared from slurry of Example 2 (using 3.85 wt% of 1-propanol))
Example 11	Example 7 Preparation Anode (prepared from slurry of Example 3 (using 7.7 wt% of 1-propanol))
Example 12	Example 8 Production anode (prepared as the slurry of Example 4 (using 3.85 wt% ethanol))
Comparative Example 6	COMPARATIVE EXAMPLE 4 Production anode (prepared as a slurry of Comparative Example 1 (only water as a solvent))
Comparative Example 7	COMPARATIVE EXAMPLE 5 Production anode (prepared as a slurry of Comparative Example 2 (using water as a solvent + dispersant))

Test Example 1: Physical properties and morphological evaluation of an electrode made of a slurry composition for preparing an anode

The surface roughness (roughness) of the positive electrode prepared in Examples 5 to 8 and Comparative Examples 4 and 5 was measured and the shape of the electrode after drying was visually confirmed. The results are shown in Table 2 below.

As can be seen from the above Table 2, it can be seen that the surface roughnesses of the electrodes of Examples 5 to 8 of the present invention were improved to be equivalent or greatly improved as compared with the electrode of Comparative Example 4 using only water as a solvent.

In addition, the electrode curl after drying of the electrodes of Examples 5 to 8 of the present invention was remarkably improved as compared with the electrode of Comparative Example 4 using only water as a solvent, and showed an improvement equal to or better than Comparative Example 5 using a dispersant.

Also, in the electrode of Comparative Example 4 using only water as a solvent, cracks were generated in the electrode during the process of spreading the dried electrode, and the electrode was desorbed. In Examples 5 to 8 of the present invention, Did not occur.

Test Example 2: Evaluation of energy density of a battery

The energy density of the batteries prepared in Examples 9 to 12 and Comparative Example 7 was measured by the following method.

<Analysis condition>

- Device: 100mA charge / discharge unit

- Discharge: 0.1C, constant current mode, discharge termination when 1.8V voltage is reached

- Temperature: 25 ^o C

After discharging, the energy of the measured cell was divided by the weight of the anode except the current collector, and the energy density was obtained.

Test cell	Condition	Energy density (Wh / kg)
Example 9	1-propanol 0.77% (Examples 1 and 5)	1416
Example 10	1-propanol 3.85% (Examples 2 and 6)	1381
Example 11	1-propanol 7.7% (Examples 3 and 7)	1429
Example 12	Ethanol 3.85% (Examples 4 and 8)	1426
Comparative Example 7	Water, dispersant (Comparative Examples 2 and 5)	1348

As can be seen from the above Table 3, the batteries of Examples 9 to 12 of the present invention exhibited higher energy densities than the batteries of Comparative Example 7 using the dispersing agent, although no separate dispersing agent was used.

Claims (12)

1. A positive electrode slurry composition comprising a positive electrode active material, a binder, an alcohol and water, wherein the content of the alcohol is 0.1 to 10% by weight based on the total weight of the composition.
2. The method according to claim 1,

   Wherein the composition comprises from 0.1 to 15% by weight of alcohol, based on the total weight of the alcohol and water, and from 85 to 99.9% by weight of water.
3. The method according to claim 1,

   Wherein the alcohol is a C1 to C5 lower alcohol.
4. The method of claim 3,

   Wherein the C1 to C5 lower alcohol is propanol.
5. The method according to claim 1,

   Wherein the positive electrode slurry composition comprises 10 to 78% by weight of the positive electrode active material, 1 to 50% by weight of a binder, 0.1 to 10% by weight of an alcohol and residual water.
6. 6. The method of claim 5,

   Wherein the composition further comprises 0.1 to 10% by weight of a conductive material.
7. The method according to claim 6,

   Wherein the composition comprises 2 to 45 parts by weight of an alcohol based on 100 parts by weight of the cathode active material and the conductive material.
8. The method according to claim 1,

   Wherein the composition is for preparing a positive electrode of a lithium-sulfur battery.
9. 9. The method of claim 8,

   Wherein the cathode active material is a sulfur-carbon composite.
10. A positive electrode prepared by applying the positive electrode slurry composition of claim 1 onto a current collector.
11. A positive electrode of claim 10;

    A negative electrode comprising lithium metal or a lithium alloy as a negative electrode active material;

    A separator provided between the anode and the cathode; And

    A battery comprising: an electrolyte;
12. 12. The method of claim 11,

    Wherein the lithium alloy is an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn.

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