KR102546049B1 - 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 using a molded product, and more particularly, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, a molded product having a certain shape and size is formed and then the molded product is laminated in two or more stages. The present invention relates to a method for producing a solid electrolyte for a secondary battery using a molded product in which a sufficient reaction occurs than in the form of a powder to increase the synthesis efficiency. Preparation process for preparing by mixing; A pulverization step of mixing the synthetic powder raw materials prepared by the preparation step and finely pulverizing them to a certain size using a ball mill; a drying step of removing moisture from the synthesized powder raw material harvested by performing the grinding step using a dry oven; An annealing step for releasing the phenomenon in which the synthetic powder raw materials are agglomerated during the drying step; A molding forming step of molding the synthetic powder raw material released by the annealing step using a mold to have a predetermined shape and size; a lamination step of laminating the moldings made by the molding forming step inside a synthesis furnace in two or more stages; It is characterized in that it is manufactured in the order of a synthesis process in which the laminated moldings are synthesized (reacted) using high-temperature heat.

Description

Method for manufacturing solid electrolyte for secondary battery by molded article {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 using a molded product, and more particularly, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, a molded product having a certain shape and size is formed and then the molded product is laminated in two or more stages. It relates to a method for producing a solid electrolyte for a secondary battery by a molded article in which a sufficient reaction occurs than in the form of a powder when synthesized 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 applications such as portable information terminals, portable electronic devices, small power storage devices for home use, motorcycles, electric vehicles, and hybrid electric vehicles. It is increasing. In accordance with the spread of such uses, there is a demand for improved safety and higher performance of lithium secondary batteries.

As conventional lithium secondary batteries use liquid electrolytes, they are easily ignited when exposed to water in the air, so stability problems have always been raised. This stability problem is becoming more of an issue 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 recently been actively conducted 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 power, long lifespan, simplification of manufacturing processes, large/compact batteries, and low cost.

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

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

Japanese Patent Registration No. 4,779,988 discloses an all-solid-state lithium secondary battery having a stacked structure of positive electrode/solid electrolyte layer/negative electrode and composed of a sulfide-based solid electrolyte layer.

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

The LLZO has a cubic (cubic) and tetragonal (Tetragonal) structure, and the ionic conductivity is higher when the cubic structure than when the tetragonal structure. In order to manufacture the LLZO solid electrolyte with a cubic structure with high ion conductivity, sintering must be performed at a high temperature of 1,200 ° C or more. 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 technique for producing a LLZO solid electrolyte having high ion conductivity by adjusting the sintering characteristics and the like.

As shown in FIG. 1 of the accompanying drawings, the conventional method for manufacturing a solid electrolyte for a secondary battery as described above performs a preparation step (S10) of mixing and preparing powders such as synthetic powder raw materials LiCO ₃ , La ₂ O ₃ , ZrO ₂ and the like at a constant ratio. And mixing the synthetic powder raw material prepared by the preparation step (S10) and performing a pulverization step (S20) of finely pulverizing to a certain size using a ball mill.

On the other hand, a drying step (S30) of removing moisture from the synthesized powder raw material harvested by the grinding step (S20) is performed using a dry oven, and then charged into a synthesis furnace (Al ₂ O ₃ crucible) and heated with high temperature heat. (S40) and 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, the conventionally synthesized powder raw material is charged in an Al ₂ O ₃ crucible in a powder state and reacted at 900 ° C. for 5 hours to synthesize the synthesized powder raw material to have a molecular formula of Li ₇ La ₂ Zr ₂ O ₁₂ (reaction ), but as lithium was vaporized, as shown in FIG. 2a of the accompanying drawing, the La ₂ Zr ₂ O ₇ phase was confirmed. As such, a phenomenon in which the synthesized powder raw materials are not synthesized and agglomerated occurs, and due to the above-mentioned conventional problems, excessive use of synthesis time has resulted in a decrease in productivity.

Republic of Korea Patent Registration No. 1460113 Republic of Korea Patent Registration No. 1804211

In view of these conventional problems, the present invention, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, forms a molded product having a certain shape and size and then laminates the molded product in two or more stages to synthesize a more sufficient form than the powder form. It is an object of the present invention to provide a method for manufacturing a solid electrolyte for a secondary battery by a molded article in which a reaction occurs to increase synthesis efficiency, drastically reduce a production period, and improve conductivity.

The above object of the present invention is a method for manufacturing a solid electrolyte for a secondary battery, comprising: a preparation step of preparing by mixing synthetic powder raw materials in a constant ratio; A pulverization step of mixing the synthetic powder raw materials prepared by the preparation step and finely pulverizing them to a certain size using a ball mill; a drying step of removing moisture from the synthesized powder raw material harvested by performing the grinding step using a dry oven; An annealing step for releasing the phenomenon in which the synthetic powder raw materials are agglomerated during the drying step; A molding forming step of molding the synthetic powder raw material released by the annealing step using a mold to have a predetermined shape and size; a lamination step of laminating the moldings made by the molding forming step inside a synthesis furnace in two or more stages; It is achieved by a method for manufacturing a solid electrolyte for a secondary battery by a molding, characterized in that the laminated molding is produced by a synthesis process in which the laminated molding is synthesized (reacted) using high-temperature heat.

The solid electrolyte is achieved by a method for producing a solid electrolyte for a secondary battery by 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 using a molded product, characterized in that the molded product is stacked in an overlapping manner or stacked in a zigzag manner.

In the present invention, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, forming a molded product having a certain shape and size, and then stacking the molded product in two or more stages to synthesize, a sufficient reaction occurs than in the form of a powder, resulting in higher synthesis efficiency. It is a useful invention that has the effect of increasing the production period, reducing the production period, and improving the 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 manufacturing a solid electrolyte for a secondary battery.
3 is a manufacturing process diagram showing a method of 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 molded article 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 using a molding to which the technology of the present invention is applied.
Figures 5a and 5b are graphs and SEM pictures showing the effect on the synthesis when the conventional powder is used and when the pressure is applied differently to the molding molded in the form of a plate-shaped disk to which the technology of the present invention is applied.

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

Figure 3 is a manufacturing process diagram showing a method of manufacturing a solid electrolyte for a secondary battery by a molding to which the technology of the present invention is applied, and according to this, the present invention first performs a preparation step (S100) of mixing and preparing synthetic powder raw materials in a constant ratio .

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

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

A pulverization step (S200) of mixing the synthetic powder raw material prepared in the preparation step (S100) and finely pulverizing it to a certain size using a ball mill is performed.

In the crushing step (S200), after ball milling the starting raw materials Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ powders to have a certain size for the synthesis of LLZO, the first pulverized Li ₂ CO ₃ , The La ₂ O ₃ and ZrO ₂ powders are mixed and the second grinding is performed.

Since Li ₂ CO ₃ reacts with water in the primary chain, Et-OH was used as a solvent, and a ZrO ₂ ball with a size of Φ5 μm was selected and proceeded at 25 rpm. At this time, the ratio of raw material: ball: solvent is Mix at 1.0 : 0.8 : 2.0 and pulverize for a certain period of time.

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

In more detail about the secondary grinding, the 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 The mixture was mixed at a ratio of 4:6 with a Φ5 zirconia ball, and the raw material: mixing ball: solvent was charged at a volume ratio of 1.0: 1.0: 1.5, and milling was performed for 24 hours and 48 hours.

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

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㎛

In the present invention, it is described that the secondary grinding is performed, but it may be performed as a single grinding process. At this time, the synthetic powder raw materials used in the production of LLZO solid electrolyte are Li ₂ CO ₃ , La ₂ O ₃ , ZrO ₂ as before, and Et-OH was used as Al ₂ O ₃ as a solvent because it reacts with water. As a one-step grinding process, raw material: solvent: mixing balls are mixed at a mass ratio of 1: 1.5: 10 and ball milled for only 24 hours.

During the ball mill, the average particle size (D ₅₀ ) had to be 0.7 to 0.8 μm, and the ratio of Φ1mm and Φ5mm zirconia balls was maintained at 6:4, considering that the grinding efficiency decreases as the grinding time elapses for 24 hours , should have been set within 24 hours.

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

In the drying step (S300), the pulverized powders were dried at 90 ° C. for 6 hours using a drying oven, and in the annealing step (S400), when the drying step (S300) is performed, the synthetic powder raw materials are agglomerated, which is broken and dried This is to maintain the powder form.

A molded product forming step (S500) is performed in which the synthetic powder raw material released in the annealing step (S400) is molded using a mold to have a predetermined shape and size.

The molding forming process (S500) is formed into a certain shape and thickness using a press or CIP equipment, and the shape is formed into a plate shape (disk) or tetrahedron, for example.

As shown in FIGS. 5A to 5B, the effect of pressure on the synthesis of a molded article molded into a plate-shaped disk using the press was confirmed in the crystal phase of the unreacted raw material.

A lamination process (S600) of stacking the moldings made in the molding formation process (S500) in two or more stages inside the synthesis furnace and a synthesis process (S700) of synthesizing (reacting) the laminated moldings using high-temperature heat, in order. manufactured by

In the method of the synthesis process (S700), the molded product stacked in two or more stages is charged into an Al ₂ O ₃ crucible (synthesis furnace), and the Al ₂ O ₃ crucible (synthesis furnace) is heated at 900 to 1200 ° C for 2 to 10 hours. Synthesis is performed in the form of a disc during the process, and in the lamination process (S600), moldings may be overlapped or stacked in a zigzag manner.

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

In the present invention, in the case of a disc having a short distance between moldings made by the molding forming process (S500), that is, between molecules, it is more advantageous for LLZO synthesis than in the form of powder, and as the synthesis temperature and time increase, the LLZO phase increases. It was confirmed. Therefore, in the conventional manufacturing method using the powder, about 16% of mass loss occurred while La ₂ Zr ₂ O ₇₂ was formed, 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 according to the present invention as described above was tested as follows.

<Experiment method>

[Comparative Example 1]

Using 0.6 g of LLZO powder in an Al ₂ O ₃ crucible, heated at 1200 ° C for 2 hours and measuring ionic conductivity.

[Comparative Example 2]

In an Al ₂ O ₃ crucible, 0.6 g of LLZO powder was heated at 1200 ° C for 10 hours and the ionic conductivity was measured.

[Comparative Example 3]

In an Al ₂ O ₃ crucible, 0.6 g of LLZO powder was heated at 1250 ° C for 10 hours and the ionic conductivity was measured.

[Example 1]

Ion conductivity was measured by pressing 0.6 g of LLZO powder in an Al ₂ O ₃ crucible at a pressure of 566 kgf/cm 2 to form a disc having a diameter of 15 mm and heating it at 1200 ° C for 2 hours.

[Example 2]

Ion conductivity was measured by pressing 0.6 g of LLZO powder in 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 heating it at 1200 ° C for 10 hours.

[Example 3]

Ion conductivity was measured by pressing 0.6 g of LLZO powder in an Al ₂ O ₃ crucible at a pressure of 566 kgf/cm 2 to form a disc having a diameter of 15 mm and heating it at 1250 ° C for 10 hours.

division Synthesis efficiency (%) ionic conductivity Heating for 2 hours at 1200℃ Comparative Example 1 78.2 5.47×10 ^-6 Example 1 79.3 3.12×10 ^-5 Heating for 10 hours at 1200℃ Comparative Example 2 79.6 1.87×10 ^-5 Example 2 80.8 5.23×10 ^-5 Heating for 10 hours at 1250℃ 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, when forming the molding, it was found that the shape according to the synthesis of the pressure appeared as shown in FIGS. 5a and 5b in the accompanying drawings.

In the present invention, when synthesizing a synthetic powder raw material used as a solid electrolyte for a secondary battery, forming a molded product having a certain shape and size, and then stacking the molded product in two or more stages to synthesize, a sufficient reaction occurs than in the form of a powder, resulting in higher synthesis efficiency. It is a useful invention that has the effect of increasing the production period, reducing the production period, and improving the conductivity.

S100: Preparation process S200: Grinding process
S300: Drying process S400: Annealing process
S500: Formation process S600: Lamination process
S700: synthesis process

Claims (4)

In the method for manufacturing a solid electrolyte for a secondary battery,
A preparation step of preparing by mixing synthetic powder raw materials in a constant ratio;
A pulverization step of mixing the synthetic powder raw materials prepared by the preparation step and finely pulverizing them to a certain size using a ball mill;
a drying step of removing moisture from the synthesized powder raw material harvested by performing the grinding step using a dry oven;
An annealing step for releasing the phenomenon in which the synthetic powder raw materials are agglomerated during the drying step;
A molding forming step of molding the synthetic powder raw material released by the annealing step using a mold to have a predetermined shape and size;
a lamination step of laminating the molded article produced by the molded article forming step inside a synthesis furnace in two or more stages;
It is produced by a synthesis process in which the laminated molding is synthesized (reacted) using high-temperature heat,
In the method of the synthesis process, the LLZO powder in which the two or more stacked moldings were charged into an Al ₂ O ₃ crucible (synthesis furnace) and synthesized in a disc form at 900 to 1200 ° C for 2 to 10 hours The Li ₇ La ₃ Zr ₂ O ₁₂ phase was confirmed, and the method for manufacturing a solid electrolyte for a secondary battery by molding, characterized in that the LLZO phase increased as the synthesis temperature and time increased.
delete delete According to claim 1,
The lamination process is a method for manufacturing a solid electrolyte for a secondary battery by a molding, characterized in that the molding is stacked overlapping or stacked in a zigzag manner.

Images