KR20220136713A - Method for manufacturing solid electrolyte for secondary battery by molded articles - Google Patents

Abstract

The present invention relates to a method for manufacturing a solid electrolyte for a secondary battery by a molded product and, more particularly, to a method for manufacturing a solid electrolyte for a secondary battery by a molded product, which increases synthesis efficiency by forming a molded product with a predetermined shape and size when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery and then stacking and synthesizing the molded products in two or more stages so that a sufficient reaction occurs as compared with in the form of a powder. The present invention provides the method for manufacturing the solid electrolyte for the secondary battery comprising: a preparation process for performing preparation by mixing synthetic powder raw materials at a predetermined ratio; a pulverization step of mixing the synthetic powder raw materials prepared in the preparation step and finely pulverizing the same to a predetermined size using a ball mill; a drying step of removing moisture from the synthesized powder raw materials, obtained by performing the pulverization step, using a dry oven; an annealing step for annealing a phenomenon in which the synthetic powder raw materials are agglomerated during the drying step; a molded product forming step of molding the synthetic powder raw materials, annealed in the annealing step, using a mold so as to have a predetermined shape and size; a stacking step of stacking the molded products, molded in the molded product forming step, inside a synthesis furnace in two or more stages; and a synthesis step of synthesizing (reacting) the stacked molded products using high-temperature heat, wherein the above steps are performed in order.

Description

Method for manufacturing solid electrolyte for secondary battery by molded articles}

The present invention relates to a method for manufacturing a solid electrolyte for a secondary battery by a molding, and more particularly, to form a molding having a certain shape and size when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, and then stacking the molding in two or more layers It relates to a method for manufacturing a solid electrolyte for a secondary battery using a molded product such that when synthesized, a sufficient reaction occurs than in the form of a powder to increase the synthesis efficiency.

Because lithium secondary batteries have large electrochemical capacity, high operating potential, and excellent charge/discharge cycle characteristics, they are in demand for use in portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. is increasing In accordance with the spread of such uses, there is a demand for improved safety and performance of lithium secondary batteries.

As a conventional lithium secondary battery uses a liquid electrolyte, it easily ignites when exposed to water in the air, and thus stability has always been raised. This stability problem is becoming more and more important as electric vehicles become visible.

Accordingly, research on an All-Solid-State Secondary Battery using a solid electrolyte made of an inorganic material, which is a non-combustible material, has been actively conducted in recent years for the purpose of improving safety. All-solid-state secondary batteries are attracting attention as next-generation secondary batteries from the viewpoints of safety, high energy density, high output, long life, simplification of manufacturing processes, enlargement/compactness of batteries, and low cost.

An all-solid-state secondary battery is composed of a positive electrode/solid electrolyte layer/cathode. Of these, the solid electrolyte of the solid electrolyte layer requires high ionic conductivity and low electronic conductivity. In addition, solid electrolytes are also included in the components of the anode and cathode layers, which are electrode layers, and a mixed conductive material having both high ionic and electronic conductivity is advantageous for the solid electrolyte used in the electrode layer.

Solid electrolytes that satisfy the requirements of the solid electrolyte layer of all-solid-state secondary batteries include sulfide-based, oxide-based, and the like. The double sulfide-based solid electrolyte has problems in that a resistance component is generated by an interfacial reaction with a positive electrode active material or a negative electrode active material, has strong hygroscopicity, and a toxic gas, hydrogen sulfide (H2S) gas, is generated.

Japanese Patent No. 4,779,988 discloses an all-solid-state lithium secondary battery having a stacked structure of anode/solid electrolyte layer/cathode and comprising a sulfide-based solid electrolyte layer.

Among these oxide-based solid electrolytes, LLTO (Li3xLa2/(3-x)TiO3) and LLZO (Li7La3Zr2O12) are widely known. It is attracting attention as a promising material.

The LLZO has a cubic and tetragonal structure, and has higher ionic conductivity in the cubic structure than in the tetragonal structure. In order to produce a cubic LLZO solid electrolyte with high ionic conductivity, sintering must be performed at a high temperature of 1,200°C or higher, so it is difficult to manufacture a cubic structure with high ionic conductivity, and the high-temperature sintering process causes lithium in the solid electrolyte to be sintered. There was a problem with volatilization. Therefore, since there is a difference in ion conductivity depending on the crystal structure, it is necessary to develop a technology for manufacturing a LLZO solid electrolyte having high ionic conductivity by controlling the sintering characteristics and the like.

The above-described conventional solid electrolyte manufacturing method for a secondary battery is prepared by mixing powders such as synthetic powder raw materials LiCO ₃ , La ₂ O ₃ , ZrO ₂ at a certain ratio as shown in the accompanying drawings (S10). and performing a grinding process (S20) of mixing the raw material for the synthetic powder prepared by the preparation process (S10) and pulverizing it to a predetermined size using a ball mill.

On the other hand, a drying process (S30) of removing moisture from the synthetic powder raw material harvested by the pulverization process (S20) is performed using a dry oven, and charged into a synthesis furnace (Al ₂ O ₃ crucible) and heated with high temperature heat (S40) was synthesized (reacted) to prepare LLZO having a molecular formula of Li ₇ La ₂ Zr ₂ O ₁₂ , that is, a solid electrolyte composition for a secondary battery.

As described above, conventionally, a synthetic powder raw material is charged in a powder state into an Al ₂ O ₃ crucible, and the reaction is performed at 900 ° C. for 5 hours to synthesize the synthetic powder raw material to have a molecular formula of Li ₇ La ₂ Zr ₂ O ₁₂ (reaction ) was carried out, but as lithium was vaporized, as shown in FIG. 2a of the accompanying drawing, the La ₂ Zr ₂ O ₇ phase was confirmed. Synthetic powder raw materials are not synthesized, but agglomeration occurs, and due to the above-mentioned conventional problems, there is a problem in that the synthesis time is excessively used and, thereby, productivity is lowered.

Korean Patent Registration No. 1460113 Korean Patent Registration No. 1804211

The present invention devised in view of these conventional problems is that when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, a molded article having a certain shape and size is formed, and then the molded article is laminated in two or more stages to synthesize it. An object of the present invention is to provide a method for manufacturing a solid electrolyte for a secondary battery using a molded product such that a reaction occurs so that synthesis efficiency is increased, a production period is greatly reduced, and conductivity is improved.

An object of the present invention is to provide a method for preparing a solid electrolyte for a secondary battery, comprising: a preparation step of preparing by mixing a synthetic powder raw material in a predetermined ratio; a grinding process of mixing the synthetic powder raw materials prepared by the preparation process and finely pulverizing them to a predetermined size using a ball mill; a drying process of removing moisture from the synthetic powder raw material harvested by the pulverization process using a dry oven; An annealing process for releasing the synthetic powder raw material aggregation occurs during the drying process; a molding forming process of molding the synthetic powder raw material released by the annealing process using a mold to have a predetermined shape and size; a lamination process of laminating the molded article made by the molded article forming process in two or more stages inside the synthesis furnace; It is achieved by a method for manufacturing a solid electrolyte for a secondary battery by a molding, characterized in that it is manufactured by a synthesis process of synthesizing (reacting) the laminated moldings using high-temperature heat.

The solid electrolyte is achieved by a method for manufacturing a solid electrolyte for a secondary battery by a molding, characterized in that LLZO or LATP.

The molded article is achieved by a method for manufacturing a solid electrolyte for a secondary battery by a molded article, characterized in that any one of a plate shape and a rectangular parallelepiped shape.

The lamination process is achieved by a method for manufacturing a solid electrolyte for a secondary battery by a molded product, characterized in that the moldings are stacked to be overlapped or stacked in a zig-zag manner.

As described above, in the present invention, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, a molded article having a certain shape and size is formed and then the molded article is laminated in two or more stages to synthesize it, a sufficient reaction occurs than in the form of a powder, and the synthesis efficiency is increased It is a useful invention that has the effect of increasing, dramatically reducing the production period, and improving conductivity.

1 is a manufacturing process diagram showing a conventional method for manufacturing a solid electrolyte for a secondary battery.
2A is a graph showing components of a solid electrolyte prepared by a conventional method for preparing a solid electrolyte for a secondary battery.
2B is an enlarged electron microscope photograph showing the structure of a solid electrolyte prepared by a conventional method for preparing a solid electrolyte for a secondary battery.
3 is a manufacturing process diagram showing a method for manufacturing a solid electrolyte for a secondary battery by a molding to which the technology of the present invention is applied.
4A is a graph showing components of a solid electrolyte prepared by a method for manufacturing a solid electrolyte for a secondary battery using a molding to which the technology of the present invention is applied.
4B is an enlarged electron microscope photograph showing the structure of a solid electrolyte prepared by a method for manufacturing a solid electrolyte for a secondary battery by a molding to which the technology of the present invention is applied.
5a and 5b are graphs and SEM photographs showing the effect on the synthesis when different pressures are applied to the molded product molded in the form of a plate-shaped disk to which the technology of the present invention is applied and when using conventional powder.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. However, the scope of the spirit of the present embodiment can be determined from the matters disclosed in this embodiment, and the spirit of the present embodiment is the implementation of addition, deletion, change, etc. of components with respect to the proposed embodiment It will be said to include transformations.

3 is a manufacturing process diagram showing a method for manufacturing a solid electrolyte for a secondary battery by a molding to which the technology of the present invention is applied. According to the present invention, first, a preparation process (S100) of preparing by mixing a synthetic powder raw material at a certain ratio is performed. .

Here, the synthetic powder raw material is a mixed powder made by mixing Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ for manufacturing LLZO, and LiNO ₃ , Al(H ₂ PO ₄ ), NH for manufacturing LATP ₄ H ₂ PO ₄ , Ti[OCH(CH ₃ ) ₂ ] ₄ Means any one of the mixed powders.

In the present invention, LLZO, an oxide-based electrolyte that is stable at high voltage among solid electrolytes, has an ionic conductivity value of up to 10 ^-4 to 10 ^-3 S/cm at room temperature, and does not react in the atmosphere, so that it is easy to synthesize. to explain

A grinding process (S200) of mixing the raw material for the synthetic powder prepared by the preparation process (S100) and pulverizing it to a predetermined size using a ball mill is performed.

The grinding process (S200) is a ball mill operation to each of the starting materials Li ₂ CO ₃ , La ₂ O ₃ , ZrO ₂ powder to have a constant size for the synthesis of LLZO, and then the primary grinding is completed Li ₂ CO ₃ , La ₂ O ₃ , ZrO ₂ Secondary grinding is performed by mixing the powder.

In the primary chain, since Li ₂ CO ₃ reacts with the aqueous system, Et-OH was used as a solvent, and a ZrO ₂ ball of Φ5 μm size was selected and proceeded at 25 rpm. At this time, the ratio of raw material: ball: solvent was 1.0: 0.8: 2.0 mixed and pulverized for a certain period of time.

The secondary grinding was performed by ball milling at a speed of 25 rpm for 12 to 48 hours at a speed of 25 rpm so that the volume ratio of raw material: mixed ball: solvent (anhydrous ethanol) was 1.0: 1.0: 1.5 using zirconia balls.

To describe the secondary grinding in more detail, Li ₂ CO ₃ , La ₂ O ₃ and ZrO ₂ powders were weighed so that the Li:La:Zr source had a molar ratio of 7.7:3:2, and the mixing balls used were Φ1 and Milling was carried out for 24 hours and 48 hours by mixing with a zirconia ball of Φ5 at a ratio of 4: 6 and charging the raw material: mixing ball: solvent in a volume ratio of 1.0: 1.0: 1.5.

Table 1 below shows the particle size distribution and microstructure of the mixed powder of the starting material prepared by the grinding process. When the ball mill time is 48 hours, it is possible to prepare a starting material mixed powder for synthesizing LLZO powder having an average particle size of 0.71 um, which is similar to that of the mixed powder prepared by secondary grinding.

In the secondary grinding, the size by time is shown in Table 1.

milling time La ₂ O ₃ Li ₂ CO ₃ ZrO ₂ 0 hours 53.68㎛ 145.69㎛

1.54㎛ 12 hours 4.86㎛ 5.60㎛ 24 hours 3.49㎛ 4.22㎛ 36 hours 2.88㎛ 3.62㎛ 48 hours 2.67㎛ 3.29㎛

Although the present invention has been described as performing the secondary grinding, it may be carried out in a single grinding process. At this time, the synthetic powder raw material used to manufacture LLZO solid electrolyte is the same as before, using Li ₂ CO ₃ , La ₂ O ₃ , ZrO ₂ , and Since it reacts in an aqueous system, Et-OH was used as Al ₂ O ₃ as a solvent. In a one-step grinding process, raw material:solvent:mixing balls are mixed in a mass ratio of 1:1.5:10 and ball milled for only 24 hours.

At the time of the ball mill, the average particle size (D ₅₀ ) had to be satisfied from 0.7 to 0.8 μm, and the ratio of Φ1mm and Φ5mm zirconia balls was maintained at 6:4, and as the grinding time elapsed for 24 hours, the grinding efficiency decreased. , should be set within 24 hours.

On the other hand, during the drying process (S300) of removing moisture from the synthetic powder raw material harvested by the pulverization process (S200) using a dry oven and the drying process (S300), a phenomenon in which the synthetic powder raw material is agglomerated occurs. An annealing process (S400) for releasing is performed.

In the drying process (S300), the pulverized powders were dried at 90 ° C. for 6 hours using a drying oven. To maintain the powder form.

A molding process (S500) of molding the synthetic powder raw material released by the annealing process (S400) using a mold to have a predetermined shape and size is performed.

The molded article forming process (S500) is formed in a certain shape and thickness using a press or CIP equipment, and the form is, for example, a plate shape (disk), or a cuboid.

The crystalline phase of the unreacted raw material was confirmed as shown in the accompanying drawings 5a to 5b on the effect of pressure on the synthesis of the molded product molded in the form of a plate-shaped disk using the press.

The lamination process (S600) of laminating the molded product made by the molding product forming process (S500) in two or more stages inside the synthesis furnace, and the synthesis process (S700) of synthesizing (reacting) the laminated molding using high-temperature heat manufactured by

In the method of the synthesis process (S700), the Al ₂ O ₃ crucible was charged, and the synthesis was performed in an Al ₂ O ₃ crucible (synthesis furnace) at 900 to 1200° C. for 2 to 10 hours, and the lamination process (S600) The silver moldings can be stacked to each other or stacked in a zig-zag manner.

As described above, in the present invention, when the synthetic powder raw materials are synthesized by laminating the molding, the technology of the present invention is applied as shown in the accompanying drawings 2a and 4a to form the molding in the form of a disc, and LLZO is synthesized. In the powder, the Li ₇ La ₃ Zr ₂ O ₁₂ phase was confirmed, but in the LLZO powder synthesized in the powder form, the La ₂ Zr ₂ O ₇ phase was confirmed.

l The present invention is advantageous for LLZO synthesis rather than powder form in the case of a disc having a close distance between molecules, that is, between moldings made by the molding process (S500), and it was confirmed that the LLZO phase increases as the synthesis temperature and time increase. . Therefore, in the conventional manufacturing method using powder, La ₂ Zr ₂ O ₇₂ is formed and a mass loss of about 16% occurs, but in the present invention, it was confirmed that Li ₇ La ₃ Zr ₂ O ₁₂ was synthesized.

The ionic conductivity of the LLZO powder prepared by the present invention as described above was tested as follows.

<Experiment method>

[Comparative Example 1]

Using 0.6g of LLZO powder in an Al ₂ O ₃ crucible, heated to 1200℃ for 2 hours and measured ionic conductivity.

[Comparative Example 2]

Using 0.6 g of LLZO powder in an Al ₂ O ₃ crucible, it was heated to a temperature of 1200℃ for 10 hours and the ionic conductivity was measured.

[Comparative Example 3]

Al ₂ O ₃ crucible was heated to 1250 ℃ temperature for 0.6 g of LLZO powder for 10 hours and the ionic conductivity was measured.

[Example 1]

0.6 g of LLZO powder was pressed into an Al ₂ O ₃ crucible at a pressure of 566 kgf/cm 2 to form a disk having a diameter of 15 mm and heated at 1200° C. for 2 hours to measure ionic conductivity.

[Example 2]

0.6 g of LLZO powder was pressed into an Al ₂ O ₃ crucible at a pressure of 566 kgf/cm 2 to form a disk having a diameter of 15 mm and heated at 1200° C. for 10 hours to measure ionic conductivity.

[Example 3]

0.6 g of LLZO powder was pressed into an Al ₂ O ₃ crucible at a pressure of 566 kgf/cm 2 to form a disk having a diameter of 15 mm and heated at 1250° C. for 10 hours to measure ionic conductivity.

division Synthesis efficiency (%) ionic conductivity Heating at 1200℃ for 2 hours Comparative Example 1 78.2 5.47×10 ^-6 Example 1 79.3 3.12×10 ^-5 Heating at 1200℃ for 10 hours Comparative Example 2 79.6 1.87×10 ^-5 Example 2 80.8 5.23×10 ^-5 Heating at 1250℃ for 10 hours Comparative Example 3 81.4 2.84×10 ^-4 Example 3 84.1 2.34×10 ^-4

Ion conductivity measurement method: 0.5g LLZO powder and 1wt% PVB were mixed with ethanol to form a plate with a thickness of 1.0mm and a diameter of 10mm, and measured by impedance measurement using an ion conductivity meter.

On the other hand, it was found that when the molding was formed, the shape according to the pressure was synthesized as shown in the accompanying drawings 5a and 5b.

As described above, in the present invention, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, a molded article having a certain shape and size is formed and then the molded article is laminated in two or more stages to synthesize it, a sufficient reaction occurs than in the form of a powder, and the synthesis efficiency is increased It is a useful invention that has the effect of increasing, dramatically reducing the production period, and improving conductivity.

S100: Preparation process S200: Grinding process
S300: drying process S400: annealing process
S500: forming process S600: lamination process
S700: Synthesis process

Claims (4)

In the method for manufacturing a solid electrolyte for a secondary battery,
A preparation process of preparing by mixing synthetic powder raw materials in a certain ratio;
a grinding process of mixing the synthetic powder raw materials prepared by the preparation process and finely pulverizing them to a predetermined size using a ball mill;
a drying process of removing moisture from the synthetic powder raw material harvested by the pulverization process using a dry oven;
An annealing process for releasing the synthetic powder raw material aggregation occurs during the drying process;
a molding forming process of molding the synthetic powder raw material released by the annealing process using a mold to have a predetermined shape and size;
a lamination process of laminating the molded article made by the molded article forming process in two or more stages inside the synthesis furnace;
A method for manufacturing a solid electrolyte for a secondary battery by a molding, characterized in that it is manufactured by a synthesis process of synthesizing (reacting) the laminated moldings using high-temperature heat.
The method of claim 1,
The solid electrolyte is a method for producing a solid electrolyte for a secondary battery by a molding, characterized in that LLZO or LATP.
The method of claim 1,
The molded article is a method for manufacturing a solid electrolyte for a secondary battery by a molded article, characterized in that any one of a plate shape and a rectangular parallelepiped shape.
The method of claim 1,
The lamination process is a method for manufacturing a solid electrolyte for a secondary battery by a molded product, characterized in that the moldings are stacked to be overlapped or stacked in a zig-zag manner.

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