KR101417282B1 - sulfur electrode of lithium sulfur battery and manufacturing method for the same, and lithium sulfur battery appling the same - Google Patents

Abstract

The present invention relates to a lithium sulfur battery sulfur electrode capable of solving the problems of dissolving polysulfide and improving the energy density by maximizing the thickness of the sulfur electrode by securing an ion conduction path by applying a solid ion conductor A method for producing the same, and a lithium sulfur battery including a sulfur electrode.
In order to achieve the above object, the sulfur electrode of the lithium sulfur battery according to the present invention has a plurality of pores therein, and the sulfur active material containing sulfur, a conductive material and a binder is filled in the pores to conduct lithium ions to sulfur Solid ionic conductors made available; And a current collector formed on one surface of the ion conductor to maximize the amount of sulfur to be inserted, thereby improving the energy density.

Description

[0001] The present invention relates to a sulfur electrode for a lithium sulfur battery, a method for manufacturing the sulfur electrode, and a lithium sulfur battery using the sulfur electrode,

The present invention relates to a sulfur electrode of a lithium sulfur battery capable of maximizing the loading amount of sulfur to improve energy density, a method for producing the sulfur electrode, and a lithium sulfur battery using the sulfur electrode.

The lithium-sulfur battery has a much higher theoretical energy density of 2600 Wh / kg compared to conventional lithium-ion batteries with a theoretical energy density of 570 Wh / kg.

FIG. 1 is a cross-sectional view showing the structure of a conventional lithium sulfur unit cell. The lithium sulfur unit cell 1 includes a copper foil 15 as a collector of a negative electrode, a lithium electrode 14 as a negative electrode, A sulfur electrode 12 as an anode, and an aluminum thin plate 11 as a current collector of an anode.

The lithium electrode 14 may be manufactured by pressing a thin lithium plate on a copper foil 15 and the sulfur electrode 12 may be formed of aluminum And then applying a slurry containing sulfur to the thin plate 11.

Here, since sulfur is a nonconductor having a low ion / electron conductivity, a conductive material (conductive material) must be added when manufacturing the sulfur electrode 12.

At this time, the conductive material added to the sulfur electrode 12 provides a path for allowing the lithium ions dissolved in the electrolyte to move to the sulfur and react, and is also used as an electron transfer path between the aluminum current collector and the sulfur.

Meanwhile, when a conventional lithium-sulfur battery is applied to an electric vehicle, the energy density of the battery should satisfy 300 to 500 Wh / kg in order to have a distance similar to that of a gasoline vehicle.

In order to satisfy the above-mentioned energy density, the sulfur active material is thickened on the aluminum current collector, and the amount of sulfur per unit area is stacked as much as possible.

However, as shown in FIG. 2, when the thickness of the sulfur electrode 1 is 200 μm or more, securing of ion conductivity is the biggest problem. As the sulfur is reduced, polysulfide is dissolved in the liquid electrolyte, The conductivity is lowered.

In the early stage of manufacturing the sulfur electrode 1, there is no problem in conductivity. However, as charging / discharging is repeated, some active materials are separated from both ends of the surface of the sulfur electrode 1 far from the current collector 2 (see also Fig. Solid byproducts are formed from the surface of the sulfur electrode 1 to block or reduce the ion conduction path, thereby deteriorating the conductivity.

As a result, as the thickness of the sulfur electrode 1 becomes thicker, the conductivity is lowered, so that the thickness of the anode is limited to a certain thickness or more.

For example, although the thickness of the sulfur electrode 1 which is generally used is less than 100 탆, the sulfur electrode can be manufactured to a thickness of 200 탆 at maximum to increase the energy density in a battery cell or a battery pack unit.

Disclosure of Invention Technical Problem [8] The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a solid ion conductor capable of solving the problems of dissolving polysulfide, And a method for producing the same, and a lithium sulfur battery including a sulfur electrode.

In order to achieve the above object, the sulfur electrode of the lithium sulfur battery according to the present invention has a plurality of pores therein, and the sulfur active material containing sulfur, a conductive material and a binder is filled in the pores to conduct lithium ions to sulfur Solid ionic conductors made available; And a current collector formed on one surface of the ion conductor to maximize the amount of sulfur to be inserted, thereby improving the energy density.

And the pores are formed in an open pore structure connected to the pores so that the reactivity between the sulfur and the ion conductor can be maximized.

The ion conductor has a pore size of 2 to 100 탆 to activate interfacial reactivity between the sulfur and the ion conductor, to insert the sulfur active material into the pores, and to have a porosity of 50 to 95%, making full use of the sulfur active material and securing the ion conduction path So as to be able to perform the operation.

The ion conductor may be a LiSICON (? -Li ₃ PO ₄ derivative), a Thio-LiSICON (Li _3.25 Ge _0.25 P _0.75 S ₄ derivative), NaSiCON (NaZr ₂ P ₃ O ₁₂ derivative), Perovskite (La _2/3 Li _{1 / 3} TiO ₃ derivative), Garnet (Li ₅ La ₃ M ₂ O ₁₂ , M = Ta, Nb derivative), LiPON, LiPOS, LiSON and LiSIPON or a mixture thereof.

The method for manufacturing a sulfur electrode of a lithium sulfur battery according to the present invention comprises the steps of: preparing a solid ion conductor having a porous structure; And filling the pores of the solid ion conductor with a sulfur active material including sulfur and a conductive material.

The step of preparing the solid ion conductor of the porous structure may be performed by a method such as a colloidal crystal template method, a carbon template method, a freeze casting method, an aerogel method, a tape casting method, ) Method according to the present invention.

The step of charging the sulfur active material into the pores of the solid ion conductor may be performed using any one of a sulfur active material particle slurry filling method, a sulfur melting method, and a sulfur deposition method.

The present invention provides a lithium sulfur battery to which a sulfur electrode manufactured using a solid ion conductor having a porous structure is applied.

Advantages of the present invention will be described as follows.

First, a porous three-dimensional solid ion conductor is prepared and the sulfur active material is filled in the pores of the porous structure by various methods to manufacture the sulfur electrode. This solves the polysulfide dissolution problem generated in the sulfur electrode when the conventional liquid electrolyte is applied Thereby improving the charge / discharge cycle life.

Second, since the ion conduction path is stably secured in the entire thickness range, the thickness of the sulfur electrode can be maximized up to 500 탆, thereby realizing a battery cell of high energy density.

Third, it is expected that a sulfur electrode using a porous three - dimensional solid ion conductor can be applied to a lithium sulfur battery to develop a next - generation electric vehicle which can be compared with the endurance level of an internal combustion engine automobile.

1 is a cross-sectional view showing the structure of a lithium sulfur battery cell according to the prior art;
FIG. 2 is a schematic view for explaining a problem of the prior art when the thickness of the sulfur electrode is 200 μm or more in FIG.
3 is a schematic view showing the structure of a sulfur electrode of a lithium sulfur battery according to an embodiment of the present invention;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

FIG. 3 is a schematic view showing a structure of a sulfur electrode of a lithium-sulfur battery according to an embodiment of the present invention.

The present invention provides a sulfur electrode (20) capable of maximizing the thickness of the sulfur electrode (20) to 500 탆 by stably securing the ion conduction path over the entire thickness range, a method for producing the sulfur electrode (20) 20). ≪ / RTI >

To this end, the present invention can solve the problem that the polysulfide is dissolved in the existing liquid electrolyte by applying the solid ion conductor 21 having high ion conductivity as high as the liquid electrolyte even at room temperature instead of the existing liquid electrolyte.

In other words, the ion conductor 21 serves to move lithium ions to the sulfur electrode 20, and has a plurality of pores 22 therein.

The pores 22 are porous three-dimensional open pores 22 and the pores 22 are connected to each other.

That is, it is possible to move the material between the pores 22.

The open pores 22 having the above structure are filled with the sulfur active material 23 and the sulfur active material 23 is moved between the open pores 22 and the pores 22 are formed into a spherical shape Thereby maximizing the interfacial reactivity between the sulfur and the ion conductor 21.

The sulfur active material 23 inserted into the pores 22 includes a conductive material, a binder, and sulfur. In addition to the sulfur, the conductive material, the binder, and the like are included in the pores 22, , It is possible to ensure the maximum contact area between the sulfur in the pores 22 and the ion conductor 21 by making the pores 22 into a spherical shape.

The size of the pores 22 is determined according to the thickness of the sulfur electrode 20 so that the interface reactivity between the sulfur and the ion conductor 21 is maximized and the sulfur active material 23 is separated from the open pores 22 The size of the pores 22 is preferably 2 to 100 탆.

The porosity of the ion conductor 21 is preferably selected within the range of 50 to 95 in consideration of the structure and physical stability of the ion conductor 21 for securing the ion conduction path while maximally utilizing the sulfur sulfur material.

The porous three-dimensional structure is manufactured in an ordered pore structure that is uniformly distributed in terms of ensuring fairness and ionic conductivity, but irregular and unaligned porous structures are also possible.

This is because the arrangement of the pores 22 can be irregularly designed by increasing the porosity in order to utilize the sulfur active material 23 as necessary.

The present invention also provides a sulfur electrode 20 to which a porous three-dimensional solid ion conductor 21 is applied.

The sulfur electrode 20 is composed of a solid ion conductor 21 having a plurality of porous three-dimensional pores 22 therein and a current collector 23 formed on one surface of the ion conductor 21.

The sulfur active material 23 is inserted into the pores 22 of the ion conductor 21 and the thickness of the sulfur electrode 20 is increased by 2 in comparison with the thickness of the existing lithium ion battery 23 in order to increase the insertion amount of the sulfur active material 23. [ Fold, and up to 500μm.

Possible solid ion applying the present invention conductor 21 is oxide and sulfide boundaries specifically _{LiSICON (γ-Li 3 PO 4} derivative), Thio-LiSICON (Li 3.25 Ge 0.25 P 0.75 S 4 derivative), NaSiCON (NaZr 2 P ₃ O ₁₂ derivative), Perovskite (La _2/3 Li _1/3 TiO ₃ derivative), Garnet (Li ₅ La ₃ M ₂ O ₁₂ , M = Ta, Nb derivative), LiPON, LiPOS, LiSON, And an amorphous structure.

The present invention relates to a method for manufacturing a sulfur electrode 20 using a porous three-dimensional ion conductor 21, which comprises the steps of: preparing a plurality of porous solid three-dimensional ion conductors 21 in the interior thereof; 21 by inserting and filling the sulfur active material 23 into the pores 22.

The solid ion conductor 21 having a porous three-dimensional structure may be formed by a method such as a colloidal crystal template method, a carbon template method, a freeze casting method, an aerogel method, Method, a tape casting method, or the like is used.

Particularly, the colloidal crystal template method and the carbon template method are advantageous in that the pore 22 can be easily aligned and the size can be easily controlled.

The freeze casting method has a characteristic of being aligned while growing in the form of a rod.

The method of filling the sulfur active material 23 in the pores 22 of the porous three-dimensional solid ion conductor 21 manufactured by the above method is a method of filling the slurry of the sulfur active material 23 (including the conductive material and the binder) A melting method, and a sulfur deposition method.

The present invention can maximize the insertion amount of sulfur in the sulfur electrode (20) using the ion conductor (21) having a porous structure by manufacturing the lithium sulfur battery using the sulfur electrode (20) The energy density of the lithium ion battery can be improved.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited by the following examples.

Example

In the case of the first embodiment according to the present invention, the pore 22 is well-arranged with a porosity of 70% by the colloidal crystal template method using the oxide-based ion conductor 21 (La _2/3 Li _1/3 TiO ₃ ) , And a pore size of about 2 탆.

1: 1: 1 mixture of sulfur (Aldrich), a conductive material (CNT, Hanwha Nanotech) and a binder (PVdF-co-HFP, Kynar) in NMP (N-methyl-2-pyrrolidone) And the sulfur active material 23 is prepared in such a manner that the slurry does not flow, and then the sulfur active material 23 is inserted and filled into the fabricated porous three-dimensional porous structure to produce the sulfur electrode 20 .

In the case of the second embodiment according to the present invention, pores 22 are arranged in a well-aligned manner using a colloidal crystal template method using oxide-based ion conductor 21 (Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ ) A porous structure having a porosity of 65% and a pore size of about 6 탆 is prepared.

The solid content of sulfur and conductive material (CNT, Hanwha Nanotech) and binder (PVdF-co-HFP, Kynar) was adjusted to NMP (N-methyl-2-pyrrolidone) The sulfur active material 23 is prepared by adjusting the concentration so that the slurry does not flow, and then the sulfur active material 23 is inserted into the prepared porous three-dimensional pore structure to prepare the sulfur electrode 20.

The ion conductivity in the ion conductor 21 of the sulfur electrode 20 fabricated in the above embodiment was about 10 ^-5 S / cm at room temperature, and the ion conductivity in the current collector 23 of the sulfur electrode 20 The electrical conductivity was about 10 ² ~ 10 ³ S / cm.

Although the above embodiment is only a few examples, the components and the manufacturing method of the sulfur electrode 20 applying the porous three-dimensional solid ion conductor 21 shown in the drawings can be manufactured by various methods.

Therefore, according to the present invention, the porous three-dimensional solid ion conductor 21 is manufactured and the sulfur active material 23 is filled in the pores of the porous structure by various methods to manufacture the sulfur electrode 20, It is possible to solve the problem of polysulfide dissolution generated in the sulfur electrode 20 and to improve the life of the charge / discharge cycle.

In addition, since the ion conduction path is stably secured in the entire thickness range, the thickness of the sulfur electrode 20 can be maximized up to 500 탆, thereby realizing a battery cell of high energy density.

In addition, it is expected that the sulfur electrode 20 using the porous three-dimensional solid ion conductor 21 can be applied to a lithium sulfur battery to develop a next-generation electric vehicle which can be compared with the endurance level of an internal combustion engine vehicle.

20: sulfur electrode
21: Solid ion conductor
22: Groundwork
23: The whole house
24: Sulfur active material

Claims (8)

In a sulfur electrode of a lithium sulfur battery,
A solid ion conductor 21 having a plurality of pores 22 therein and filled with a sulfur active material 23 containing sulfur, a conductive material and a binder in the pores 22 to conduct lithium ions to sulfur, ;
A current collector 23 formed on one surface of the ion conductor 21;
And a second electrode connected to the second electrode.
The method according to claim 1,
Wherein the pores (22) are made of an open pore structure in which pores (22) are connected to each other.
The method according to claim 1,
Wherein the ion conductor (21) has a pore size of 2 to 100 μm and a porosity of 50 to 95%.
The method according to claim 1,
The ion conductor 21 is _{LiSICON (γ-Li 3 PO 4} derivative), Thio-LiSICON (Li 3.25 Ge 0.25 P 0.75 S 4 derivative), NaSiCON (NaZr 2 P 3 O 12 derivative), Perovskite (La 2/3 Li ₃ TiO ₃ derivative), Garnet (Li ₅ La ₃ M ₂ O ₁₂ , M = Ta, Nb derivative), LiPON, LiPOS, LiSON and LiSIPON or a mixture thereof Sulfur electrode of lithium sulfur battery.
A method of manufacturing a sulfur electrode of a lithium sulfur battery,
Preparing a solid ion conductor (21) having a porous structure; And
Filling the pores (22) of the solid ion conductor (21) with sulfur and a sulfur active material (23) including a conductive material;
Wherein the lithium sulfur battery is a lithium sulfur battery.
The method of claim 5,
The step of preparing the solid ion conductor 21 of the porous structure may be performed by a method such as a colloidal crystal template method, a carbon template method, a freeze casting method, an aerogel method, (Tape casting) method. ≪ RTI ID = 0.0 > [10] < / RTI >
The method of claim 5,
The step of filling the sulfur active material 23 into the pores 22 of the solid ion conductor 21 is carried out by using any one of a sulfur active material particle slurry filling method, a sulfur melting method, and a sulfur vapor deposition method A method for manufacturing a sulfur electrode of a lithium sulfur battery.
A lithium sulfur battery using the sulfur electrode according to any one of claims 1 to 4.

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