KR102102212B1 - Aluminum-galium doped solid electrolyte material for all-solid-state lithium secondary battery and method for preparing the same - Google Patents

Abstract

The present invention relates to an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by Chemical Formula 1, and a method for manufacturing the same. The solid electrolyte of the present invention and its manufacturing method control the aluminum content, gallium content and lithium content of the starting material and control the feed rate of the raw material, thereby forming a high-precision cubic structure and improving the sintering properties to improve the ion conductivity of the solid electrolyte. It has the effect of improving.
[Formula 1]
Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

Description

Aluminum-gallium doped solid electrolyte for all-solid lithium secondary battery and its manufacturing method {ALUMINUM-GALIUM DOPED SOLID ELECTROLYTE MATERIAL FOR ALL-SOLID-STATE LITHIUM SECONDARY BATTERY AND METHOD FOR PREPARING THE SAME}

The present invention relates to an aluminum-gallium doped solid electrolyte for an all-solid lithium secondary battery and a method for manufacturing the same, more specifically, to control the aluminum (Al) content, gallium (Ga) content and lithium (Li) content of the starting material, For a solid-state lithium secondary battery capable of improving ion conductivity of a solid electrolyte by forming a highly accurate cubic structure and improving sintering characteristics by performing a coprecipitation reaction by a Taylor reaction method, but by controlling flow of mixture (turbulent control) It relates to a solid electrolyte and a method of manufacturing the same.

Lithium secondary batteries have high electrochemical capacity, high operating potential, and excellent charge / discharge cycle characteristics, so they are in demand for applications such as portable information terminals, portable electronic devices, small household electric power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. Is increasing. With the spread of these uses, it is required to improve the safety and performance of lithium secondary batteries.

Conventional lithium secondary batteries are easily ignited when exposed to water in the air by using a liquid electrolyte, and stability problems have always been raised. This stability issue is becoming more and more an issue as electric vehicles become visible.

Accordingly, recently, for the purpose of improving safety, research on an all-solid-state secondary battery using a solid electrolyte made of a non-combustible inorganic material has been actively conducted. The all-solid-state secondary battery is drawing attention as a next-generation secondary battery from the viewpoints of stability, high energy density, high output, long life, simplification of the manufacturing process, and large / compact and low cost of the battery.

The all-solid lithium secondary battery is composed of an anode / solid electrolyte layer / cathode, of which high ion conductivity and low electron conductivity are required for the solid electrolyte of the solid electrolyte layer. In addition, a solid electrolyte is also included in the components of the anode and cathode layers, which are electrode layers, and a mixed conductive material having both high ionic conductivity and electron conductivity is advantageous for the solid electrolyte used in the electrode layer.

There are sulfide-based and oxide-based solid electrolytes that satisfy the requirements of the solid electrolyte layer of the all-solid-state secondary battery. Among them, the sulfide-based solid electrolyte has a problem in that a resistance component is generated by an interface reaction with a positive electrode active material or a negative electrode active material, has strong hygroscopicity, and generates hydrogen sulfide (H ₂ S) gas, which is a toxic gas.

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

Oxide-based solid electrolyte is _{LATP (Li 1. 3 Al 0} . 3 Ti 1 .7 (PO 4) 3), LLTO (Li 3x La 2 / (3x) TiO 3) based, LLZO (Li ₇ La ₃ Zr ₂ O ₁₂ ), etc. are widely known, and among them, LLZO, which has a relatively high grain boundary resistance compared to LLTO, but is known to have excellent dislocation window characteristics, is attracting attention as a promising material.

The LLZO is difficult to grasp process conditions due to volatilization of lithium (Li) in the sintering process, despite the advantages of high ionic conductivity, low reactivity with the electrode material, and wide potential window (0-6V). However, due to the sinterability, the manufacturing process is complicated and difficult, so there is a difficulty in practical application. In addition, since the difference in ionic conductivity is large depending on the crystal structure, it is necessary to develop a technique for controlling the crystal structure of LLZO by adjusting the composition of the starting material, sintering characteristics, and the like.

The present invention is to solve the problems of the prior art as described above, the object of the present invention is to adjust the aluminum (Al) content, gallium (Ga) content and lithium (Li) content of the starting material and mix the raw materials of the Taylor reaction method It is to provide a solid electrolyte having improved ionic conductivity by forming a high-precision cubic structure and improving sintering characteristics by controlling the flow of materials (turbulent control) and a method for manufacturing the same.

One aspect of the present invention for achieving the above object, relates to a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by the formula (1) will be.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may be represented by the following Chemical Formula 2.

[Formula 2]

Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4)

Also, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may have a molar ratio of aluminum (Al) and gallium (Ga) of 5:25 to 25: 5.

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may have a molar ratio of aluminum (Al) and gallium (Ga) of 5:22 to 5:18.

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) has an ion conductivity of 3.0 x 10 ^-4 to 1.5 x 10 ^-3 and may have a single phase cubic structure.

Another aspect of the present invention, a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by the following Chemical Formula 1; And conductive polymer; relates to a composite solid electrolyte containing.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

Another aspect of the present invention, (a) lanthanum (La), zirconium (Zr), aluminum (Al) and a metal aqueous solution containing gallium (Ga), a complexing agent, a mixed solution mixed with a pH adjuster Preparing a solid electrolyte precursor slurry by coprecipitation reaction; (b) washing and drying the solid electrolyte precursor slurry to prepare a solid electrolyte precursor; (c) mixing the solid electrolyte precursor with a lithium source to prepare a mixture; And (d) calcining the mixture at 600 to 1,000 ° C. to prepare a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum and gallium doped with Formula 1; , The step (a) relates to a method for producing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga), which is performed in a Kuet Taylor vortex reactor.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may be represented by the following Chemical Formula 2.

[Formula 2]

Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4)

In addition, by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) with respect to the mole number (M1) of the lithium element of the lithium source in step (c) The ratio (m1: m2) of the sum (m2) of the number of moles of aluminum element and gallium element (m1) to the number of moles (m1) of lithium element 1 can be controlled to be 6.7: 0.1 to 5.8: 0.4.

In addition, by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) with respect to the mole number (M1) of the lithium element of the lithium source in step (c) The ratio (m1: m2) of the sum (m2) of the number of moles of aluminum and gallium elements (m1) to the number of moles (m1) of lithium element 1 can be controlled to be 6.4: 0.2 to 6.1: 0.3.

In addition, after step (d), the solid electrolyte represented by Chemical Formula 1 may further include a step (e) of sintering at 1,000 to 1,300 ° C.

In addition, the metal aqueous solution is lanthanum nitrate hydrate (La (NO ₃ ) ₃ · xH ₂ O), zirconium hydrochloride hydrate (ZrOCl ₂ · xH ₂ O), aluminum nitrate hydrate (Al (NO ₃ ) ₃ · xH ₂ O) and gallium Nitrate hydrate (Ga (NO ₃ ) ₃ · xH ₂ O), and x may be each independently an integer of 1 to 9.

In addition, the complexing agent may be ammonium hydroxide (NH ₄ · OH).

In addition, the pH adjusting agent may be sodium hydroxide (NaOH).

In addition, the lithium source may be lithium hydroxide hydrate (LiOH · H ₂ O).

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) has an ion conductivity of 3.0 x 10 ^-4 to 1.5 x 10 ^-3 and may be a single phase cubic structure.

Another aspect of the present invention relates to an all-solid lithium secondary battery comprising an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) produced by the production method according to the present invention as described above.

The method for preparing the solid electrolyte of the present invention controls the aluminum (Al) content, gallium (Ga) content, and lithium (Li) content of the starting material and performs a coprecipitation reaction by a Taylor reaction method, but controls the feed rate of the raw material, thereby ensuring high precision. It has the effect of improving the ionic conductivity of the solid electrolyte by forming the cubic structure and improving the sintering properties.

1 is a flow chart of a method for producing a solid electrolyte of the present invention.
2 is a schematic diagram of a Kuet Taylor vortex reactor.
3 is a graph obtained by converting resistance values measured by the EIS method to ionic conductivity for pellet sintered bodies prepared according to Examples 1 and 3 and Comparative Examples 1 and 2.
4 is a result of XRD analysis of the solid electrolyte powder prepared according to Examples 1 to 4 and Comparative Examples 1 and 2.
Figure 5 is a SEM observation of the cross-section of the pellet sintered body prepared according to Examples 1 to 4 and Comparative Examples 1 and 2.
6 is a graph of LSV characteristics evaluation of the composite solid electrolyte sheet prepared according to Examples 1 and 3 and Comparative Examples 1 and 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains may easily practice.

However, the following description is not intended to limit the present invention to specific embodiments, and when it is determined that a detailed description of known technologies related to the present invention may obscure the subject matter of the present invention, the detailed description will be omitted. .

The terms used herein are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, or combination thereof described in the specification exists, or that one or more other features or It should be understood that the existence or addition possibilities of numbers, steps, actions, elements, or combinations thereof are not excluded in advance.

The present invention provides an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by Chemical Formula 1 below.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

The LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may be represented by the following Chemical Formula 2.

[Formula 2]

Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4)

The aluminum (Al) and gallium (Ga) doped LLZO solid electrolyte may have a molar ratio of aluminum (Al) and gallium (Ga) of 5:25 to 25: 5, preferably 5:22 to 5:18. have.

LLZO solid electrolyte, the aluminum (Al) and gallium (Ga) is doped with the ion conductivity of 3.0 x 10 ^-4 to 1.5 x 10 ^-3, preferably from 1.0 x 10 ^-3 to 1.3 x 10 ^{- 3,} and, on the single It can have a cubic structure.

The present invention is a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by Formula 1; And a conductive polymer; provides a composite solid electrolyte containing.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

1 is a flowchart of a method for manufacturing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) according to the present invention.

Hereinafter, a method of manufacturing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) of the present invention will be described in detail with reference to FIG. 1. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of claims to be described later.

The method of manufacturing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) of the present invention includes (a) a metal aqueous solution containing lanthanum (La), zirconium (Zr), aluminum (Al), and gallium (Ga). , Preparing a solid electrolyte precursor slurry by coprecipitating a mixed solution of a complexing agent and a pH adjusting agent; (b) washing and drying the solid electrolyte precursor slurry to prepare a solid electrolyte precursor; (c) mixing the solid electrolyte precursor with a lithium source to prepare a mixture; And (d) calcining the mixture at 600 to 1,000 ° C. to prepare a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum and gallium doped with Formula 1; , Step (a) may be performed in a Kuet Taylor vortex reactor.

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may be represented by the following Chemical Formula 2.

[Formula 2]

Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4)

First, a metal solution containing lanthanum, zirconium, aluminum, and gallium (Ga) is co-precipitated with a mixed solution of a complexing agent and a pH adjusting agent. Solid electrolyte  Prepare a precursor slurry (step a).

Nitrate, the metal solution lanthanum hydrate _{(La (NO 3) 3 ·} xH 2 O), zirconium hydrochloride hydrate _{(ZrOCl 2 · xH 2 O)} , aluminum nitrate hydrate _{(Al (NO 3) 3 ·} xH 2 O) and gallium nitrate Hydrate (Ga (NO ₃ ) ₃ · xH ₂ O), and x may be any one of an integer of 1 to 9, each independently.

In addition, the complexing agent may be ammonium hydroxide (NH ₄ · OH), sodium hydroxide and the like.

In addition, the pH adjusting agent may include sodium hydroxide (NaOH), ammonia, and the like, but is not limited thereto. Any other pH adjusting agent capable of adjusting the pH of the mixed solution is possible without affecting the physical properties of the ion-conducting solid oxide.

Step (a) can be carried out in a Couette-Taylor vortices reaction.

2 is a schematic diagram of a Taylor vortex reactor.

Referring to FIG. 2, a Kuet Taylor vortex reactor capable of performing a Kuet Taylor vortex reaction includes an external fixed cylinder and an internal rotating cylinder rotating therein. The inner rotating cylinder has a rotating shaft coinciding with the longitudinal axis of the outer fixed cylinder. The inner rotating cylinder and the outer fixed cylinder are installed to be spaced apart from each other at predetermined intervals, thereby forming a fluid passage through which the reaction liquid flows between the inner rotating cylinder and the outer fixed cylinder. When the inner rotating cylinder rotates, the fluid located on the inner rotating cylinder side in the fluid passage tends to go outward in the direction of the external fixed cylinder by centrifugal force, and as a result, the fluid becomes unstable and regularly rotates in the opposite direction along the rotation axis. A vortex in a twin pair is formed. It is said to be vortexed by Taylor or Kuet Taylor. The Kuet Taylor vortex promotes the co-precipitation reaction, thereby making the precursor more advantageous than the conventional co-precipitation reactor.

At this time, the Kuet-Taylor reactor can distinguish the characteristics of the fluid flow by using a Taylor number (Ta), which is a dimensionless variable, and can express the definition of the corresponding area for each characteristic. Taylor number (Ta) is represented as a function of Reynolds number (Re) and is expressed by Equation 1 below.

[Equation 1]

In equation 1, w is the angular velocity of the inner cylinder, r _i is the radius of the inner cylinder, d is the parallel distance between the two cylinders, and v is the dynamic viscosity. In general, the value of the Taylor number (Ta) is adjusted by using the revolutions per minute (RPM) expressed by the angular velocity of the inner cylinder. In general, when a fluid flows between two plates, a Kuet flow occurs due to shear stress, and similarly, a Kuet flow occurs at a low RPM between two cylinders. However, when the RPM of the internal cylinder exceeds a certain threshold, the Kuet flow becomes a new Kuet-Taylor flow, and a Taylor vortex that cannot be seen in the Kuet flow occurs. Taylor vortex consists of a pair of two vortices and has a characteristic of line symmetry and is located in a toroidal direction. Therefore, vortices rotating counterclockwise exist on both sides of the vortex rotating clockwise, and each vortex affects each other. When the RPM of a certain size is increased in the Kuet-Taylor flow, it becomes a new flow due to the increase in the instability of the Taylor vortex, where the Taylor vortex has an azimuthal wavenumber. This flow is called a Wavy vortex flow, and the mixing effect at this time may increase than the Kuet-Taylor flow.

Next, above Solid electrolyte  The precursor slurry is washed and dried Solid electrolyte  Prepare the precursor (step b).

The pH of the solid electrolyte precursor may be about 7 by washing the solid electrolyte precursor slurry with water.

Then, the washed and dried Solid electrolyte  The precursor is mixed with a lithium source to prepare a mixture (step c).

Formula (1) by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) to the mole number (M1) of the lithium element of the lithium source of step (c) The ratio (m1: m2) of the sum (m2) of the number of moles of aluminum and gallium elements (m1: m2) to the number of moles (m1) of lithium elements can be controlled to be 6.7: 0.1 to 5.8: 0.4, preferably 6.4: 0.2 To 6.1: 0.3.

Here, by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) to the mole number (M1) of the lithium element of the lithium source in step (c) It is possible to improve the crystal structure control and sinterability of the solid electrolyte. If the ratio of moles (M1: M2) is less than 6.7: 0.1, the amount of Al and Ga doping required for the formation of the Cubic structure is insufficient, so it is difficult to control the sintering property and the ion conductivity may be lowered. Even if it exceeds 5.8: 0.4, Al and Ga are excessive As a result, a phenomenon in which the pellet sintering density decreases may occur, resulting in lower ion conductivity.

In addition, the lithium source may be lithium hydroxide hydrate (LiOHH ₂ O), lithium hydroxide (LiOH), lithium nitrate (LiNO ₃ ), or the like.

The lithium content of the lithium source may be added excessively in consideration of the amount of lithium evaporated during calcination or sintering, and the lithium content of 100 parts by weight of the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) as final products The lithium content of the lithium source with respect to 101 to 120 parts by weight, preferably 103 to 115 parts by weight, more preferably 105 to 115 parts by weight may be included in the mixture.

The structural cubic structure is advantageous in terms of ion conductivity, and in the case of the tetragonal structure, the ion conductivity may be lowered.

In some cases, the precursor may be pulverized before mixing the precursor and the lithium source.

The grinding and mixing may be performed by a ball mill process.

Finally, the mixture at 600 to 1,000 ℃ By calcination  Aluminum and gallium represented by the formula (1) Doped  A lithium lanthanum zirconium oxide (LLZO) solid electrolyte is prepared (step d).

[Formula 1]

Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3)

In addition, the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) may be represented by the following Chemical Formula 2.

[Formula 2]

Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4)

LLZO solid electrolyte, the aluminum (Al) and gallium (Ga) is doped with the ion conductivity of 3.0 x 10 ^-4 to 1.5 x 10 ^-3, preferably from 1.0 x 10 ^-3 to 1.3 x 10 ^{- 3,} and, on the single It may be a cubic structure.

The calcination may be performed at 600 to 1,000 ° C, preferably 800 to 950 ° C, more preferably 880 to 920 ° C.

The calcination can be performed for 1 to 20 hours, and preferably for 1 to 7 hours. However, the calcination time is not necessarily limited to this, and may vary depending on the calcination temperature.

Optionally, after step (d), the solid electrolyte represented by Chemical Formula 1 may further include a step (e) of sintering at 1,000 to 1,300 ° C.

The sintering may be performed at 1,000 to 1,300 ° C, preferably 1,100 to 1,250 ° C, and more preferably 1,150 to 1,220 ° C.

The sintering may be performed for 3 to 7 hours, preferably 4 to 6 hours. However, the sintering time is not necessarily limited to this, and may vary depending on the sintering temperature.

The solid electrolyte and the solid electrolyte sintered body include at least one structure selected from a cubic structure and a tetragonal structure, and preferably, the solid electrolyte and the solid electrolyte sintered body may be a single phase cubic structure. . As described above, it is advantageous in terms of ion conductivity that the solid electrolyte has a cubic structure, and in the case of a tetragonal structure, ion conductivity may be lowered.

The present invention provides an all-solid lithium secondary battery comprising LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) produced by the manufacturing method according to the present invention as described above.

[Example]

Hereinafter, the present invention will be described in more detail through examples. However, this is for illustrative purposes, and the scope of the present invention is not limited thereby.

Example  1: Al 0.2mole  And Ga 0.05mole Doped Solid electrolyte  And Pellet  Sintered body manufacturing

Starting materials are lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) was dissolved in distilled water so that the molar ratio of their metal elements La: Zr: Al: Ga was 3: 2: 0.2: 0.05 to prepare a starting material solution having a starting material concentration of 1 mol. .

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours, and then pulverized, so that aluminum (Al) 0.2 mole, gallium (Ga) 0.05 mole doped Li _{6 . 25} Al _{0 . 2} Ga _{0 . 05} La ₃ Zr ₂ O _{12 A} solid electrolyte was prepared.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Example  2: Al 0.2mole  And Ga 0.1mole Doped Solid electrolyte  And Pellet  Sintered body manufacturing

Starting materials are lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) was dissolved in distilled water so that the molar ratio of their metal element La: Zr: Al: Ga was 3: 2: 0.2: 0.1 to prepare a starting material solution having a starting material concentration of 1 mol. .

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours and then pulverized, so that Li ₆ doped with 0.2 mol of aluminum (Al) and 0.1 mol of gallium (Ga) _{. 1} Al _{0 . 2} Ga _{0 . A 1} La ₃ Zr ₂ O ₁₂ solid electrolyte was prepared.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Example  3: Al 0.05mole  And Ga 0.2mole Doped Solid electrolyte  And Pellet  Sintered body manufacturing

Starting materials are lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) was dissolved in distilled water so that the molar ratio of their metal elements La: Zr: Al: Ga was 3: 2: 0.05: 0.2 to prepare a starting material solution having a starting material concentration of 1 mol. .

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours and then pulverized, so that Li ₆ doped with aluminum (Al) 0.05 mole and gallium (Ga) 0.2 mole _{. 25} Al _{0 . 05} Ga _{0 . A 2} La ₃ Zr ₂ O ₁₂ solid electrolyte was prepared.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Example  4: Al 0.1mole  And Ga 0.2mole Doped Solid electrolyte  And Pellet  Sintered body manufacturing

Starting materials are lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) was dissolved in distilled water so that the molar ratio of their metal elements La: Zr: Al: Ga was 3: 2: 0.1: 0.2 to prepare a starting material solution having a starting material concentration of 1 mol. .

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours and then pulverized, so that Li ₆ doped with 0.1 mol of aluminum (Al) and 0.2 mol of gallium (Ga) _{. 1} Al _{0 . 1} Ga _{0 . A 2} La ₃ Zr ₂ O ₁₂ solid electrolyte was prepared.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Example 5: Preparation of composite solid electrolyte sheet using Example 1

Al-Ga-LLZO and polyethylene oxide (PEO, melting temperature: 65 ° C) prepared according to Example 1, Al-Ga-LLZO content is 70 wt% based on the total weight (Al-Ga-LLZO + PEO) -Ga-LLZO and PEO solid electrolyte binder were weighed and stirred at 2,000 rpm for 15 minutes using a Sinky mixer to prepare a mixture.

At this time, the PEO solid electrolyte binder is a mixed solution containing PEO, ACN and LiClO ₄ , and the PEO solid electrolyte binder is designed to have ion conductivity, and the content ratio of PEO and LiClO ₄ is [PEO]: [LiClO ₄ ] = 15: 1.

ACN was mixed with the mixture, and the mixture was stirred with a syncy mixer to adjust the viscosity. Next, a slurry was prepared by adding 5 mm zircon balls and stirring at 2,000 rpm for 15 minutes with a Sinky mixer. The slurry was cast on a PET (polyethylene terephthalate) film, dried at room temperature, and adjusted to a thickness of 150 μm to prepare a composite solid electrolyte sheet.

Example 6: Preparation of a composite solid electrolyte sheet using Example 3

A composite solid electrolyte sheet was prepared in the same manner as in Example 5, except that Al-Ga-LLZO prepared according to Example 3 was used instead of Al-Ga-LLZO prepared according to Example 1.

Comparative Example 1: Preparation of Al 0.25mole doped solid electrolyte and pellet sintered body

The starting materials lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O) and aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) are their metal elements La: A starting material solution having a starting material concentration of 1 mol was prepared by dissolving Zr: Al in distilled water so that the molar ratio was 3: 2: 0.25.

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours and then pulverized to prepare Li _6.25 Al _0.25 La ₃ Zr ₂ O ₁₂ solid electrolyte doped with aluminum (Al) 0.25 mole.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Comparative Example 2: Preparation of Ga 0.25mole doped solid electrolyte and pellet sintered body

The starting materials lanthanum nitrate (La (NO ₃ ) ₃ · 6H ₂ O), zirconium hydrochloride (ZrOCl ₂ · 2H ₂ O) and gallium nitrate (Ga (NO ₃ ) ₃ · 9H ₂ O) are their metal elements, La: A starting material solution having a starting material concentration of 1 mol was prepared by dissolving in distilled water so that the molar ratio of Zr: Ga is 3: 2: 0.25.

Referring to FIG. 2, a solid electrolyte was prepared using a Kuet Taylor vortex reactor. The Kuet Taylor vortex reactor includes a solution injection part (1), a temperature control solution discharge part (2), a temperature control solution injection part (3), a reaction solution drain part (4), and a reactant (slurry form) discharge part (5). , A stirring rod (6), a solution reaction unit (7), a reaction solution temperature control unit (8). An appropriate amount of the starting material solution, 0.6 mol of ammonia water, and an aqueous sodium hydroxide solution is added as a complexing agent through the injection section 1 of the Kuet Taylor vortex reactor so that the pH is adjusted to 11 and the reaction temperature is 25 ° C. The reaction time was 4 hr, and the stirring speed of the stirring rod was co-precipitated at 1,000 rpm to discharge the precursor slurry in the form of a liquid slurry to the discharge portion 5.

The precursor slurry was washed with purified water and dried for 24 hours. After pulverizing the dried precursor with a ball mill, excess LiOHH ₂ O was added and mixed with a ball mill to prepare a mixture. The LiOH · H ₂ O content of the mixture was added in excess of 10 wt% so that 110 parts by weight of Li in 100 parts by weight of Li in the solid electrolyte in which the content of Li in LiOH · H ₂ O was generated. The mixture was calcined at 900 ° C. for 2 hours and then pulverized to prepare Li _6.25 Ga _0.25 La ₃ Zr ₂ O ₁₂ solid electrolyte doped with gallium (Ga) 0.25 mole.

Subsequently, pellets were produced by using a molding mold for the calcined powder, and then sintered at 1,200 ° C for 5 hours to prepare pellet sintered bodies.

Comparative Example 3: Preparation of a composite solid electrolyte sheet using Comparative Example 1

A composite solid electrolyte sheet was prepared in the same manner as in Example 5, except that Al-LLZO prepared according to Comparative Example 1 was used instead of Al-Ga-LLZO prepared according to Example 1.

Comparative Example 4: Preparation of a composite solid electrolyte sheet using Comparative Example 2

A composite solid electrolyte sheet was prepared in the same manner as in Example 5, except that Ga-LLZO prepared according to Comparative Example 2 was used instead of Al-Ga-LLZO prepared according to Example 1.

[Test Example]

Test Example 1: Measurement of ion conductivity and specific resistance

Tables 1 and 3 show the results of measuring ionic conductivity and specific resistance by the Electrochemical Impedance Spectroscopy (EIS) method for the pellet sintered bodies prepared according to Examples 1 to 4 and Comparative Examples 1 and 2.

LLZO doping composition
(Al: Ga, molar ratio) Specific resistance (Ω.cm) Ion conductivity (S / cm) at R.T Example 1 0.20: 0.05 1627 6.15 x 10 ^-4 Example 2 0.20: 0.10 2592 3.86 x 10 ^-4 Example 3 0.05: 0.20 873 1.14 x 10 ^-3 Example 4 0.10: 0.20 2378 4.21 x 10 ^-4 Comparative Example 1 0.25: 0.00 3304 3.03 x 10 ^-4 Comparative Example 2 0.00: 0.25 954 1.05 x 10 ^-3

Referring to Table 1 and FIG. 3, the ion composition of Comparative Example 1 doped with aluminum (Al) was changed to gallium (Ga) at a specific ratio with respect to 3.03 x 10 ^-4 S / cm. 3 of Li _{6 . 25} Al _{0 . 05} Ga _{0 . It} was confirmed that the ion conductivity of ₂ La ₃ Zr ₂ O ₁₂ increased to 1.14 x 10 ^-3 S / cm.

It was confirmed that in Examples 2 and 4, in which the doping content was increased from 0.25 to 0.3, the increase in ionic conductivity was very small despite the increase in the Ga content. In the case of increasing the Ga content in the Al and Ga compositions, it is a factor of cost increase and a study is required to synthesize the Ga content by minimizing it.

Test Example 2: Crystal structure characteristics (XRD) of LLZO material according to the process and doping element composition

XRD analysis results for the solid electrolyte powders prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 are shown in FIG. 4. Referring to FIG. 4, in the case of Comparative Example 1, it was confirmed that an impurity peak was observed, and some tetragonal peaks were also observed. However, Examples 1 to 4 and Comparative Example 2 showed typical Cubic structures with increasing Ga content.

Test Example 3: Sintering characteristics of LLZO pellets according to the process and doping element composition (SEM)

The results of SEM observation of the cross-sections of the pellet sintered bodies prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 are shown in FIG. 5. In the case of Comparative Example 1 and Example 1, the cross-section of the pellet was a property in which grain boundaries of particles were clearly observed, and it was confirmed that sintering was not sufficiently performed. As the Ga doping content increased, the sintering properties improved and almost similar sintering properties were observed in Examples 2 to 4 and Comparative Example 2. The sintering characteristics alone do not determine the ion conductivity, and can be confirmed from the ion conductivity values of Examples 3 and 2, which are conditions under which sintering is improved while the doped heterogeneous elements are controlled at a 0.25 mole ratio.

Test Example 4: Evaluation of LSV characteristics of the composite solid electrolyte film sheet

6 is a graph evaluating the high potential stability by Linear Sweep Voltammetry (LSV) for the composite solid electrolyte sheets prepared according to Examples 5 and 6 and Comparative Examples 3 and 4. Referring to FIG. 6, in the case of Example 5, a phenomenon in which the electrochemical oxidation potential shifted in the direction of about 0.5 V or more (+) compared to Example 6 and Comparative Examples 3 and 4 occurred at a potential of 5.0 V or more was observed. In other words, Li ₆ synthesized at a molar ratio of 0.2 to 0.05 molar ratio of Ga _{. 25} Al _{0 . 2} Ga _{0 . 05} It can be seen that the composite solid electrolyte sheet with LLZO powder of La ₃ Zr ₂ O ₁₂ composition exhibits the best electrochemical potential stability. However, in Comparative Example 1, which is an LLZO powder-applied composite solid electrolyte sheet designed with an Al 0.25 molar ratio composition, the oxidation peak started at around 4.75 V, and Ga 0.05 molar ratio doping played a large role in moving the oxide peak in the (+) direction. You can see that there is. In the case of LLZO prepared by Example 3 or Comparative Example 2 having a relatively high Ga doping content, ionic conductivity showed excellent properties at a level of ~ 10 ^-3 S / cm, but the high potential stability was confirmed to be relatively reduced. , In the case of LLZO prepared by Example 1 and Comparative Example 1 having a relatively high Al doping content, the ion conductivity of ~ 10 ^-4 S / cm was shown, but the high potential stability was confirmed to be relatively improved. Therefore, depending on the characteristics required by the cell, if the ion conductivity is an important factor, the Ga doping content is increased, and when the potential window factor is more important, the Al doping content is required. To satisfy the two conditions at the same time, Al -Conditions for doping Ga with an appropriate composition are required, and in the present invention, the characteristic that satisfies the ionic conductivity and the potential window at the same time is Example 5, the composite solid electrolyte sheet using LLZO prepared with the composition according to Example 1, is the best. It shows characteristics.

The scope of the present invention is indicated by the following claims rather than the above detailed description, and it should be interpreted that all changes or modified forms derived from the meaning and scope of the claims and equivalent concepts thereof are included in the scope of the present invention. do.

Claims (17)

(a) lanthanum nitrate hydrate _{(La (NO 3) 3 ·} xH 2 O), zirconium hydrochloride hydrate _{(ZrOCl 2 · xH 2 O)} , aluminum nitrate hydrate _{(Al (NO 3) 3 ·} xH 2 O) and gallium nitrate hydrate (Ga (NO ₃ ) ₃ · xH ₂ O), and x is a solid solution by coprecipitating a mixed solution of a metal aqueous solution, a complexing agent, and a pH adjusting agent, each independently being an integer of 1 to 9, Preparing an electrolyte precursor slurry;
(b) washing and drying the solid electrolyte precursor slurry to prepare a solid electrolyte precursor;
(c) mixing the solid electrolyte precursor with a lithium source to prepare a mixture;
(d) The mixture is calcined at 600 to 1,000 ° C. to prepare a lithium lanthanum zirconium oxide (LLZO) solid electrolyte doped with aluminum (Al) and gallium (Ga) represented by Chemical Formula 1 below. To do; And
(e) sintering the solid electrolyte at 1,000 to 1,300 ° C;
Step (a) is carried out in a Kuet Taylor vortex reactor,
The aluminum (Al) and gallium (Ga) doped LLZO solid electrolytes have aluminum (Al) and gallium (Ga) in which the molar ratio of the aluminum (Al) and gallium (Ga) is 5:22 to 5:18. Method for preparing doped LLZO solid electrolyte:
[Formula 1]
Li _x Al _y Ga _z La _w Zr _u O ₁₂ (5≤x≤9, 0 <y≤4, 0 <z≤4, 2≤w≤4, 1≤u≤3) According to claim 1,
A method of manufacturing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga), wherein the LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga) is represented by the following Chemical Formula 2.
[Formula 2]
Li _{7-3 (x + y)} Al _x Ga _y La ₃ Zr ₂ O ₁₂ (0 <x <0.4, 0 <y <0.4, 0.1≤x + y≤0.4) delete delete According to claim 1,
The aluminum (Al) and gallium (Ga) doped LLZO solid electrolyte has an ionic conductivity of 1.14 x 10 ^-3 and has a single phase cubic structure, and the aluminum (Al) and gallium (Ga) doped LLZO Method for preparing solid electrolyte. delete delete delete According to claim 1,
Formula (1) by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) to the mole number (M1) of the lithium element of the lithium source of step (c) Aluminum (Al), characterized in that the ratio of the sum of the number of moles of aluminum elements and gallium elements (m2) (m1: m2) to the number of moles of lithium elements (m1) of 6.7: 0.1 to 5.8: 0.4 Method for manufacturing LLZO solid electrolyte doped with gallium (Ga). According to claim 1,
Formula (1) by adjusting the ratio (M1: M2) of the sum (M2) of the number of moles of the aluminum element and the gallium element of the metal aqueous solution of step (a) to the mole number (M1) of the lithium element of the lithium source of step (c) Aluminum (Al), characterized in that the ratio of the sum of the number of moles of aluminum elements and gallium elements (m2) (m1: m2) to the number of moles of lithium elements (m1) of 6.4: 0.2 to 6.1: 0.3 and Method for manufacturing LLZO solid electrolyte doped with gallium (Ga). delete delete According to claim 1,
The complexing agent is ammonium hydroxide (NH ₄ · OH), characterized in that the aluminum (Al) and gallium (Ga) doped LLZO solid electrolyte manufacturing method. According to claim 1,
A method of manufacturing an LLZO solid electrolyte doped with aluminum (Al) and gallium (Ga), characterized in that the pH adjusting agent is sodium hydroxide (NaOH). According to claim 1,
The lithium source is a lithium hydroxide hydrate (LiOH · H ₂ O) characterized in that the aluminum (Al) and gallium (Ga) doped LLZO solid electrolyte manufacturing method. delete delete

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