KR101502350B1 - Method of manufacturing solid electrolyte-lithium ion conductivity polymer composite powder - Google Patents

Abstract

A solid electrolyte-lithium ion conductive polymer composite powder capable of improving adhesion between particles while minimizing a decrease in ion conductivity during production of a solid electrolyte membrane and a method for producing the same are disclosed.
The solid electrolyte-lithium ion conductive polymer composite powder according to the present invention comprises an oxide-based solid electrolyte powder and a lithium ion conductive polymer. The lithium ion conductive polymer is selected from the group consisting of polyethylene oxide (PEO) or polyethylene glycol (PEG ).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing a solid electrolyte-lithium ion conductive polymer composite powder,

The present invention relates to a solid electrolyte-lithium ion conductive polymer composite powder and, more particularly, to a solid electrolyte-lithium ion conductive polymer composite powder capable of improving adhesion between particles while minimizing a decrease in ion conductivity during production of the solid electrolyte membrane And a manufacturing method thereof.

BACKGROUND ART [0002] Development of technology for practical use as a battery-powered device for environmentally friendly automobiles has been actively conducted worldwide by greatly improving the capacity and stability of batteries based on currently widely used lithium ion secondary batteries for portable electronic devices.

In recent years, interest in safety has been increasing in lithium-ion secondary batteries, and research has been actively conducted to replace them with solid electrolytes capable of greatly improving stability over current liquid electrolytes in which lithium solvents are dissolved in organic solvents.

On the other hand, there is a growing need for an ultra-compact power source for driving electronic devices that are becoming smaller and smaller. For this purpose, development of an all-solid-state thin film battery of a solid electrolyte is required.

The solid secondary battery comprises a positive electrode / solid electrolyte layer / negative electrode, wherein the solid electrolyte of the solid electrolyte layer is required to have high ionic conductivity and low electronic conductivity. And a solid electrolyte that satisfies this is such as sulfide, oxide, of which the oxide-based solid electrolyte, _{LLT (Li 3x La (2/3)} -x TiO 3 (0 <x <0.66)), LLZ (Li 7 La ₃ Zr ₂ O ₁₂ ) and the like are widely known.

Although LLZ has a high ionic conductivity, it is difficult to catch process conditions due to the volatilization of lithium (Li) in the sintering process, and the manufacturing process is complicated and complicated due to ovoid formation. LLT has a lower ionic conductivity than LLZ, but has a relatively good phase stability in the manufacturing process, thus facilitating the manufacturing process.

However, when a solid electrolyte membrane of an all solid secondary battery using LLT is manufactured by a room temperature spray coating method, the ionic conductivity is lower than that of a bulk material because the grain size is less than 1 탆.

Korean Unexamined Patent Publication No. 2012-0132533 (Dec. 12, 2012) discloses a full solid lithium secondary battery having excellent output characteristics by using a sulfide-based solid electrolyte as an electrolyte.

It is an object of the present invention to provide a solid electrolyte-lithium ion conductive polymer composite powder capable of improving the inter-particle adhesion while minimizing a decrease in ionic conductivity during the production of a solid electrolyte membrane, and a process for producing the solid electrolyte-lithium ion conductive polymer composite powder.

To achieve the above object, a solid electrolyte-lithium ion conductive polymer composite powder according to the present invention comprises an oxide-based solid electrolyte powder and a lithium ion conductive polymer, wherein the lithium ion conductive polymer is at least one selected from the group consisting of polyethylene oxide (PEO) And is a polyethylene glycol (PEG).

At this time, it is preferable that the oxide-based solid electrolyte powder is Li _{3 x} La _{(2/3) -x} TiO ₃ (0 <x <0.66) (LLT).

The content of the lithium ion conductive polymer is preferably 1 to 20% by weight based on the total weight of the solid electrolyte-lithium ion conductive polymer composite powder.

Also, the solid electrolyte-lithium ion conductive polymer composite powder has an ion conductivity of 1 x 10 ^-3 S / cm to 1 x 10 ^-6 S / cm.

The LLT preferably has a particle size of 0.5 to 200 mu m.

According to another aspect of the present invention, there is provided a method of preparing a solid electrolyte-lithium ion conductive polymer composite powder, comprising: (a) preparing a mixed solution by mixing an oxide-based solid electrolyte powder, a lithium ion conductive polymer, and a solvent; And (b) drying the mixed solution, wherein the lithium ion conductive polymer is polyethylene oxide (PEO) or polyethylene glycol (PEG).

At this time, the oxide-based solid electrolyte powder is preferably LLT.

In addition, the lithium ion conductive polymer is preferably added to the solvent in an amount of 1 to 20% by weight based on the total weight of the solid content.

The drying of step (b) is preferably carried out at 60 to 100 ° C.

Also, the mixing of step (a) is preferably performed using a shear mixer.

The present invention provides a solid electrolyte-lithium ion conductive polymer composite powder in which an oxide-based solid electrolyte powder and a lithium ion conductive polymer are combined. By adding a lithium ion conductive polymer having a function as an adhesive at the same time as imparting ionic conductivity to the composite powder, the adhesion of the powder can be improved while minimizing deterioration of ionic conductivity during the production of the solid electrolyte membrane.

1 is a scanning electron microscope (SEM) photograph showing the microstructure of the LLT-PEO composite powder according to Example 1 of the present invention.
2 is a SEM photograph showing the microstructure of the LLT-PEG composite powder according to Example 2 of the present invention.
3 is a SEM photograph showing the microstructure of the LLT powder according to Comparative Example 1 of the present invention.
4 is a SEM photograph showing the microstructure of the LLT powder according to Comparative Example 2 of the present invention.
5 is a graph showing ionic conductivity measurement results of powders according to Examples 2 to 4 and Comparative Example 2 of the present invention.
6 is an SEM photograph showing the microstructure of the films according to Examples 5 to 7 and Comparative Examples 3 to 4 of the present invention.
7 is a graph showing ionic conductivity measurement results of films according to Examples 5 to 7 and Comparative Example 3 of the present invention.
8 is an enlarged graph of part A of Fig.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below.

However, it should be understood that the present invention is not limited to the embodiments disclosed herein but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Hereinafter, solid electrolyte-lithium ion conductive polymer composite powders capable of improving the adhesiveness in the production of the solid electrolyte membrane according to the present invention will be described in detail.

The solid electrolyte-lithium ion conductive polymer composite powder according to the present invention is a powder in which an oxide-based solid electrolyte powder and a lithium ion conductive polymer are combined.

At this time, the oxide-based solid electrolyte powder is preferably _{Li 3x La 2 / (3x)} TiO 3 (0 <x <0.66) ( hereinafter, referred to as LLT).

LLT is the most widely known lithium ion conductive oxide solid electrolyte, having a high ionic conductivity of about 10 ^-5 S / cm or higher and a perovskite structure and stability at a voltage of 1.8 V or higher.

When such LLT is used as a solid electrolyte, solid electrolyte-lithium ion conductive polymer composite powder having high ion conductivity can be produced.

LLT, which is used as an electrolyte in a solid secondary battery, provides a path for lithium (Li) ions between a cathode layer and a cathode layer, and preferably has a particle size of 0.5 to 200 탆 in order to satisfy this requirement. At this time, when the size of the LLT particles is less than 0.5 mu m, it may be difficult to provide sufficient migration paths of lithium ions between the anode layer and the cathode layer. On the other hand, when the size of the LLT particles exceeds 200 mu m, it may be difficult to make the solid electrolyte membrane thinner.

Since the ionic conductivity is proportional to the size of the LLT particles, it is more preferable to use the LLT having a larger particle size in terms of improving the ion conductivity.

The lithium ion conductive polymer serves as a lithium ion transfer path between the LLT particles in the powder. In addition, the lithium ion conductive polymer can have a function as an adhesive, contributing to imparting an adhesive function to LLT.

For this purpose, the lithium ion conductive polymer is preferably polyethylene glycol (PEG) or polyethylene oxide (PEO).

Polyethylene glycol (PEG) and polyethylene oxide (PEO) are known as polymeric materials with lithium ion conductivity when lithium ions are provided. Polyethylene glycol (PEG) has a molecular weight of about 20,000 or less, and polyethylene oxide (PEO) has a molecular weight of about 20,000 or more.

However, when polyethylene glycol (PEG) has a molecular weight of 800 or less, it is present as a liquid at room temperature, resulting in poor stability. When polyethylene oxide (PEO) has a molecular weight of 8,000,000 or more, It is difficult to produce a target film by bouncing.

The lithium ion conductive polymer may be added in an amount of 1 to 20% by weight, more preferably 5% by weight or less, based on the total weight of the solid electrolyte-lithium ion conductive polymer composite powder .

At this time, if the amount of the lithium ion conductive polymer is less than 1% by weight, the effect of the addition may be insufficient. On the other hand, when the content of the lithium ion conductive polymer is more than 20% by weight, the ionic conductivity of the composite powder may be significantly lowered without further improving the adhesion.

The solid electrolyte-lithium ion conductive polymer composite powder according to the present invention is an LLT-based oxide polymer composite powder in which lithium ion conductive polymers such as LLT and PEO or PEG are combined. When the film is coated at room temperature, ^It may have an ionic conductivity of ^-7 S / cm or more, preferably 1 ^10-5 S / cm to 1 ^10-3 S / cm.

The solid electrolyte-lithium ion conductive polymer composite powder according to the present invention can be used for the production of solid electrolyte membranes of all solid secondary batteries and the like. The addition of lithium ion conductive polymer minimizes deterioration of ionic conductivity, The adhesion of the electrolyte powder can be improved.

The method for preparing a solid electrolyte-polymer composite powder according to an embodiment of the present invention includes the steps of: (a) preparing a mixed solution by mixing an oxide-based solid electrolyte powder, a lithium ion conductive polymer, and a solvent; And (b) drying the mixed solution, wherein the lithium ion conductive polymer is polyethylene oxide (PEO) or polyethylene glycol (PEG).

The mixed solution prepared in the step _{LLT (Li 3x La 2 / (} 3x) TiO 3 (0 <x <0.66)) with a selected one of the oxide-based solid electrolyte powder, polyethylene oxide (PEO) or polyethylene glycol (PEG) Of the lithium ion conductive polymer and the solvent are mixed to prepare a mixed solution.

First, LLT powder and lithium ion conductive polymer, either PEO or PEG, are charged into a solvent such as primary purified water or ethanol and mixed. The LLT powder may have a particle size of 0.5 to 200 mu m as described above.

The lithium ion conductive polymer added for imparting ionic conductivity and adhesion to the oxide based antistatic electrolyte powder is preferably charged into the solvent in an amount of 1 to 20% by weight based on the total weight of the solid content.

At this time, when the lithium ion conductive polymer is charged at less than 1% by weight, the effect of improving the adhesiveness of the oxide-based solid electrolyte powder may be insufficient. On the other hand, when the lithium ion conductive polymer is charged in an amount exceeding 20%, the ionic conductivity of the composite powder may be significantly lowered.

The solvent may be an organic solvent such as primary water (D.I. water) or ethanol, but is not limited thereto.

Particularly, in the preparation of the mixed solution of the present invention, in order to prevent the particle size of the oxide-based solid electrolyte powder of the powder from being changed, a mixture of an oxide-based solid electrolyte powder, a lithium ion conductive polymer and a solvent .

In the preparation of the mixed solution, it is preferable that the mixed solution containing the oxide-based solid electrolyte powder, the lithium ion conductive polymer and the solvent is sufficiently stirred for 10 minutes to 1 hour. If the stirring time is less than 10 minutes, mixing may be insufficient. On the other hand, if the stirring time exceeds 1 hour, the production time can be prolonged without any further effect.

The LLT powder used in the mixed solution preparation step of the present invention may be a directly manufactured product or a purchased commercial product.

When the LLT powder directly used is produced, the LLT powder can be prepared by different synthesis methods depending on the desired particle size.

For example, the LLT powder may be prepared by forming a mixed powder of Li ₂ CO ₃ , La ₂ O ₃ and TiO ₂ , and then sequentially performing a first milling, a first drying, a calcination, a second milling, And can be synthesized via sieving.

At this time, the primary milling can be performed for about 6 to 30 hours, and the secondary milling can be performed for about 6 to 50 hours. For example, each of the primary and secondary milling can be mechanically pulverized and uniformly mixed for a predetermined period of time while considering the size of the target particles, while rotating the ball mill at a speed of about 50 to 500 rpm using a ball mill.

Milling tool steel (tool steel), stainless steel (stainless steel), hard metal (cemented carbide), silicon nitride (silicon nitride), alumina (alumina) and zirconia milling container (jar) of a material selected from (zirconia) and select from these , And it is not particularly limited to this. A ball having a diameter of 1 to 30 mm may be used, and all balls having the same size or balls having two or more sizes may be used together.

Meanwhile, the secondary milling may be carried out using a jet mill which injects a high-pressure gas at a flow rate of 150 to 700 L / min.

The calcination can be carried out at a temperature of 1100 to 1300 ° C for 1 to 20 hours. If the calcination temperature is less than 1100 ° C, the phase synthesis of the LLT powder may be difficult to be completely completed. On the other hand, when the calcination temperature is higher than 1300 ° C, the coagulation phenomenon of the LLT powder may occur severely and a secondary phase may occur due to the volatilization of lithium (Li). When the calcination time is out of the above range, the same problem as the calcination temperature may occur.

Next, in the mixed solution drying step, the mixed solution containing the oxide-based solid electrolyte powder, the lithium ion conductive polymer, and the solvent is dried to complete the synthesis of the solid electrolyte-lithium ion conductive polymer composite powder.

At this time, the drying of the mixed solution is preferably performed at 60 to 100 ° C for 1 to 30 hours. If the drying temperature is less than 60 占 폚 or the drying time is less than 1 hour, drying may be insufficient. On the other hand, if the drying temperature exceeds 100 DEG C or the drying time exceeds 30 hours, excessive heating may lead to an increase in manufacturing cost.

By drying, the solvent is volatilized to obtain a solid electrolyte-lithium ion conductive polymer composite powder in which the final oxide-based solid electrolyte powder and lithium ion conductive polymer are combined.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Preparation of Solid Electrolyte - Lithium Ion Conducting Polymer Composite Powder

Example 1. Preparation of LLT + 5 wt% PEO composite powder

1.5 g of 5 wt% PEO having an average molecular weight of 600,000 and 28.5 g of 95 wt% LLT powder having a particle size of 140 mu m were charged into 200 mL of ethanol and stirred with a shear mixer for 30 minutes to prepare a mixed solution. Then, the mixed solution was dried at 80 DEG C for 18 hours to obtain a final LLT-PEO composite powder.

Example 2. Preparation of LLT + 1 wt% PEG composite powder

1% by weight of PEG having an average molecular weight of 1,000 was added to LLT powder having a particle size of 140 탆 and charged into distilled water, followed by stirring with a stirrer for 30 minutes to prepare a mixed solution. The mixed solution was dried at 80 DEG C for 18 hours to obtain a final LLT-PEG composite powder.

Example 3. Preparation of LLT + 2 wt% PEG composite powder

The remainder was the same as Example 2 except that PEG was added in an amount of 2% by weight.

Example 4. Preparation of LLT + 3 wt% PEG composite powder

The remainder was the same as in Example 2, except that PEG was added in an amount of 3% by weight.

2. Preparation of LLT Powder - <Comparative Example>

Comparative Example 1. LLT powder

Was prepared using a conventional solid phase synthesis method. 21.27 g of Li ₂ CO _3, 147.37 g of La ₂ O _{3 and} 131.37 g of TiO ₂ were mixed and dried for 24 hours and then for 8 hours, followed by calcination at 1100 ° C. for 2 hours to prepare an LLT calcined powder. The prepared LLT calcined powder was re-milled for 48 hours and then dried for 8 hours and then sieved to prepare LLT powder having a final particle size of 1.8 μm.

Comparative Example 2 LLT powder

Except that the LLT calcined powder was re-milled for 24 hours to prepare an LLT powder having a particle size of 140 mu m.

The microstructure of each powder according to Examples 1 to 2 and Comparative Examples 1 to 2 was photographed by SEM and shown in Figs. 1 to 4, respectively.

Referring to FIGS. 1 to 4, it can be seen that the particle sizes of Examples 1 and 2 in which PEO or PEG is complexed with LLT are larger than those of Comparative Examples 1 and 2 comprising LLT powder alone.

3. Property evaluation

The AC impedance of the LLT-PEO composite powder according to Example 2, the LLT-PEG composite powder according to Examples 3 to 4 and the LLT powder according to Comparative Example 2 was measured to measure the ion conductivity. The results are shown in Tables 1 and 5 Respectively.

[Table 1]

Referring to Table 1 and FIG. 5, the results of Examples 2 to 4 and Comparative Example 2 were compared, and it was confirmed that the total conductivity was the best in Example 2 in which 1 wt% of PEG was added to LLT.

4. Manufacture of Solid Electrolyte - Lithium Ion Conducting Polymer Composite Film

Example 5. Production of LLT + 5 wt% PEO composite film

A composite powder comprising LLT powder having a particle size of 1.8 탆 and PEO having a particle size of 5 탆 was coated on a stainless steel (STS304) substrate having a thickness of 0.5 mm at 25 캜 by an aerosol coating method to prepare a 100 탆 thick solid electrolyte film Respectively. At this time, PEO having a molecular weight of 600,000 was used.

Example 6. Production of LLT + 5 wt% PEO composite film

The remainder was performed in the same manner as in Example 5, except that the aerosol coating was performed while the substrate was heated to 100 캜.

Example 7. Production of LLT + 5 wt% PEO composite film

The rest was performed in the same manner as in Example 5, except that the LLT powder having a particle size of 140 탆 was used and the aerosol coating was carried out while the substrate was heated to 100 캜.

5. Preparation of solid electrolyte film - < Comparative Example >

Comparative Example 3 LLT film manufacturing

A LLT powder having a particle size of 1.8 탆 was coated on a stainless steel (STS304) substrate having a thickness of 0.5 mm by an aerosol coating method to prepare a 10 탆 thick solid electrolyte membrane.

Comparative Example 4 LLT film manufacturing

Except that the LLT powder having a particle size of 140 mu m was used.

Microstructures of the respective films according to Examples 5 to 7 and Comparative Examples 3 to 4 were photographed by SEM and are shown in Figs. 6 (a) to 6 (e), respectively.

Referring to FIG. 6, it can be seen that coating films are well formed in all of Examples 5 to 7 according to the present invention. Particularly, as a result of comparing Examples 6 and 7, it can be seen that the particle size of the coating film was greatly increased while PEO surrounded the particles of the coating film in Example 7 where the LLT particles were large.

On the other hand, in the case of Comparative Examples 3 and 4 in which the LLT powder was coated alone, all of the coatings were only partially formed in Comparative Example 4 in which the particle size was small and the LLT powder was large in comparison with Comparative Example 3 .

6. Property evaluation

The alternating current impedances of the respective films according to Examples 5 to 7 and Comparative Examples 3 to 4 were measured. The results are shown in Fig. 7, and the portion A in Fig. 7 is enlarged and shown in Fig.

7 and 8, the results of AC impedance measurement of the films according to Examples 5 to 7 and Comparative Examples 3 and 4 show that in Example 7 using relatively large particles of LLT powder, 8.06 × 10 ^-5 S / cm and ion conductivity was the best.

On the other hand, in the case of Comparative Example 4 in which a coating film was partially formed, the film was not uniformly formed and conductivity measurement was impossible.

As described above, by using the composite powder in which the lithium ion conductive polymer such as PEO or PEG is mixed with the LLT powder and by further combining the LLT powder having a large particle size with the lithium ion conductive polymer, a dense coating film is formed, The size of particles in the film can be increased, which is advantageous in terms of improving the ionic conductivity of the solid electrolyte film.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

Claims (9)

delete delete delete delete delete delete delete delete A method for producing a solid electrolyte-lithium ion conductive polymer composite powder for room temperature spray coating,
(a) a powder of Li _{3 x} La _{(2/3) -x} TiO ₃ (0 <x <0.66) having a particle size of 0.5 to 200 μm as a powder of an oxide solid electrolyte, a lithium ion conductive polymer and a solvent, Lt; / RTI &gt; And
(b) drying the mixed solution,
The lithium ion conductive polymer may be polyethylene oxide or polyethylene glycol,
The lithium-ion conductive polymer is contained in 1 to 5% by weight based on the total amount of _{Li 3x La (2/3) -x TiO} 3 (0 <x <0.66) powder and a lithium ion conductive polymer,
The mixing of the step (a) is performed using a shear mixer for 10 minutes to 1 hour, and the solid electrolyte in the solid electrolyte-lithium ion conductive polymer composite powder to be produced is maintained at a particle size of 0.5 to 200 μm Lithium ion conductive polymer composite powder for normal temperature spray coating.

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