KR20230099910A - MANUFACTURING METHOD OF HYBRID TYPE LTAP(Li1.5Ti1.5Al0.5(PO4)3 AND LLZ(Li7La3Zr2O12) FOR ALL SOLID BATTERY USING WET/DRYING MILLING METHOD - Google Patents

Abstract

The present invention relates to an all-solid-state battery, which is the ultimate technology development goal in terms of stability, and particularly to the manufacture of a solid electrolyte, which is a core technology of all-solid-state batteries. (po4)3) or ltap (li1.5ti1.5al0.5 (po4)3) or ltap (li1.5ti1.5al0.5 (po4)3) / llz (li7la3zr2o12 that can replace the garnet structure) ) to prepare a hybrid solid oxide electrolyte.

Description

Manufacturing method of LTAP (Li1.5Ti1.5Al0.5(PO4)3/LLZ(Li7La3Zr2O12) hybrid solid oxide electrolyte using wet/dry reaction method {MANUFACTURING METHOD OF HYBRID TYPE LTAP(Li1.5Ti1.5Al0.5(PO4)3 AND LLZ(Li7La3Zr2O12) FOR ALL SOLID BATTERY USING WET/DRYING MILLING METHOD}

The present invention relates to an all-solid-state battery, which is the ultimate technology development goal in terms of stability, and in particular to the manufacture of a solid electrolyte, _which is a core technology of all-solid-state batteries. ₂ Si ₂ PO ₁₂ , NaZr ₂ (PO ₄ ) ₃ ) or LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) or LTAP (Li 1.5 Ti 1.5 Al 0.5 (Li _1.5 Ti _1.5 Al _0.5 ( It relates to the preparation of a PO ₄ ) ₃ )/LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) hybrid solid oxide electrolyte.

An all-solid-state secondary battery refers to a battery in which a liquid electrolyte is replaced with a solid electrolyte among the battery components described above. In this case, since all elements of the battery, such as electrodes and electrolytes, are solid, it becomes an all-solid-state battery in name and reality. Depending on the type of electrolyte, a polymer electrolyte or a ceramic electrolyte may be used. Using a solid electrolyte is advantageous in terms of battery performance such as safety, high energy density, high power, and long lifespan, and simplification of the manufacturing process, battery Interest is rising recently as it is known to be advantageous from the viewpoints of large/compact and low cost. Among lithium ion conductive solid electrolyte candidate materials, the perovskite structure of Li _3x Lal/ _3-2x TiO ₃ (LLTO) material has excellent mechanical strength and chemical stability in the air, so it is easy to manufacture the electrolyte. In general, LLTO materials show high bulk (grain/domain internal) conductivity of the level of 1x10 ^-3 S/cm, but there is a problem in that total conductivity is lowered due to very high interfacial resistance. LLZO has a tetragonal phase structure or a cubic phase structure depending on the heat treatment temperature. The cubic structure shows an ionic conductivity of 10 ^-4 S/cm or more, while the tetragonal structure shows ~10 ^-6 S It has been reported to have a conductivity of the order of /cm. On the other hand, oxide-based materials have high material stability, but low ionic conductivity. Another disadvantage is that a high-temperature heat treatment process is essential. The polymer series has the advantage of being based on the lithium polymer battery technology that we are already using. Bosch's SEEO has developed a polymer-based solid electrolyte (DryLyte). The sulfide series has high ionic conductivity, is stable against temperature changes, and is also stable with lithium metal (cathode material). Sulfur (S) is included, so it is a problem that it is vulnerable to moisture and oxygen, but sulfide-based solid electrolytes are most advanced in mass production due to many advantages. Sulfide-related research is being actively conducted in Japan, such as Toyota, Murata (acquired by Sony), and Tokyo Institute of Technology.

One aspect of the present invention relates to a solid electrolyte powder for a hybrid type all-solid-state battery, which is conventional NASICON (Na super-ionic conductor, β-alumina, Na ₃ Zr ₂ Si ₂ PO ₁₂ , NaZr ₂ (PO ₄ ) ₃ ) or Compared to LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) or LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ), ionic conductivity is improved, Ti reduction and Li loss problems are solved, and mass production for industrial application is possible It is intended to provide a solid electrolyte capable of this, and to provide a method for preparing a simple and easy LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) solid electrolyte material.

The object of the present invention is not limited to the above. Additional tasks of the present invention are described throughout the specification, and those skilled in the art will have no difficulty in understanding the additional tasks of the present invention from the contents described in the specification of the present invention.

The LTAP(Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ(Li ₇ La ₃ Zr ₂ O ₁₂ ) hybrid oxide according to the present invention contains Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ powders in the same molar ratio by weight mixing with;

Injecting La ₂ O ₃ in an increased amount of 10 wt% to prevent loss of lithium in the mixed powder;

Putting the mixed powder into a 2-propanol bowl and reacting by wet milling;

drying the wetted reactant formed into sol;

Preparing LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) oxide through two-stage heat treatment and pulverization of the dried powder;

LLZ powder is prepared through, and subsequently

mixing a TiCl ₄ (99%, Aldrich) solution with distilled water to form TiO(OH) ₂ ;

Filtering the precipitated TiO(OH) ₂ precipitate and washing with Nitric acid (65%, aldrich);

Stabilizing TiO ₂ NO ₃ ^- prepared through nitric add washing with citric acid monohydrate (C ₆ H ₈ O ₇ );

preparing a salt by adding LiNO ₃ and Al(NO ₃ )3.H ₂ O to the stabilized TiO ₂ NO ₃ ⁻ ;

forming a sol by adding NH ₄ H ₂ PO ₄ to the prepared salt (solution);

stirring the formed sol to form a gel;

LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) oxide is prepared by drying, heat-treating, and pulverizing the formed gel

Steps for preparing LLZ powder and LTAP powder by

Heat-treating the prepared powder to produce round or square pellets;

Heat-treating the prepared pellets at high temperature again to finally prepare a hybrid type film-type solid oxide electrolyte in the form of a film;

Among the prepared hybrid solid electrolytes, using LTAP as a positive electrode and LLZ as a negative electrode facing lithium;

Through LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) hybrid oxide solid electrolyte is provided.

The solid electrolyte material for an all-solid-state battery provided by the present invention is a conventional solid electrolyte material, NASICON (Na super-ionic conductor, β-alumina, Na ₃ Zr ₂ Si ₂ PO ₁₂ , NaZr ₂ (PO ₄ ) ₃ ) or LTAP (Li It has ionic conductivity 10 times higher than _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) or LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ), so it can improve electrical conductivity, which is a problem of all-solid-state batteries, and can be used for positive and negative electrodes. LTAP for an all-solid-state battery (LTAP) that can improve battery performance by improving the electrode/electrolyte interface state through a uniform spherical shape without the problem of loss of lithium and loss of ionic conductivity by using different materials for the face electrode. A method for preparing a Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) hybrid solid electrolyte may be provided.

1 is an XRD result of LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) and LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) prepared according to the present invention.
Figure 2 is a SEM picture of LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) prepared by the present invention
3 is an ionic conductivity result of LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) prepared according to the present invention.

The present invention will be described in detail through the following examples, but these are only preferred examples of the present invention, and the scope of the present invention is not limited by the description of these examples.

Put 5 g of Li ₂ CO ₃ , 9 g of La ₂ O ₃ , and 5 g of ZrO ₂ in a bowl made of zirconium oxide (ZrO2), and perform wet milling with 50 ml of 2-propanol at 400 rpm for 6 hours. . At this time, the ratio of Li ₂ CO ₃ to La ₂ O ₃ and ZrO ₂ is preferably 0.2 to 0.5:0.2 to 0.4:0.1 to 0.6 in terms of molar ratio. At this time, when each molar ratio is 0.2:0.2:0.1 or less, LLZ is not generated due to overbonding of Li ₂ CO ₃ and La ₂ O ₃ , and when it is 0.5:0.4:0.6 or more, impurities are formed due to precipitation of ZrO ₂ . Formed and interstitial ZrO ₂ is precipitated in LLZ to reduce ionic conductivity.

On the other hand, the prepared Sol is dried at 60 to 120 ° C. for 1 to 24 hours to obtain a powder. At this time, if the temperature is less than 60 degrees and less than 4 hours, sol does not dry and hydrates remain, so LLZ is not formed. Since the electrical conductivity decreases due to growth, it is controlled.

Meanwhile, the prepared powder is subjected to one-step heat treatment to improve ionic conductivity through grain boundary growth. At this time, heat treatment is preferably performed at 700 to 1100 ° C for 4 to 8 hours. When heated to 700℃ for 4 hours or less, grain growth does not occur smoothly, making it impossible to improve ionic conductivity. When heated to 1100℃ for 8 hours or longer, grain growth becomes coarse, resulting in rapid secondary heat treatment. When producing the final solid electrolyte film due to particle growth, it is limited because the bonding of the films by pressure becomes difficult.

After the heat treatment, the powder is subjected to two-stage heat treatment again. At this time, heat treatment is preferably performed at 1150 to 1350 ° C for 4 to 8 hours. The reason for the two-stage heat treatment is that after each particle is grown through the first-stage heat treatment, heat treatment at a high temperature promotes particle growth, improves ionic conductivity, and is a tetragonal system in which ionic conductivity is optimal. structure).

Meanwhile, the prepared powder is manufactured in the form of pellets with a diameter of 10 mm and a diameter of 4 mm, and a platinum or copper electrode is dry deposited as an ion blocking electrode, and an AC voltage is applied to measure the impedance. At this time, the amplitude is set to 5 to 10 mV, and the measurement frequency range is set to 0.1 Hz to 1 MHz. The resistance (Rb) of the bulk electrolyte is obtained from the intersection point where the semicircle of the measured impedance trajectory meets the real axis, and the ionic conductivity ( σ ) is obtained from the area (A) and thickness (t) of the sample as in the formula below.

40 ml of titanium tetrachloride (TiCl ₄ , Aldrich) and 280 ml of distilled water are slowly dropped at a rate of 4 ml per second in TiCl ₄ into a reactor containing distilled water to prepare TiO(OH) ₂ precipitate. At this time, the addition rate of TiCl ₄ is preferably 2 to 10 ml/min, more preferably 3 to 6 ml/min. If the addition rate is less than 2ml _, it should be avoided because the reaction rate is slowed down and precipitation does not occur and TiCl ₄ is completely decomposed. It should be avoided because it deteriorates. Meanwhile, the precipitate produced by the reaction is filtered through a 325mech filter. At this time, Nitric acid (65%, aldrich) is used as a filtering cleaning solution. Citric acid monohydrate (C ₆ H ₈ O ₇ ) is added to TiO ₂ NO ₃ ^- prepared through washing to stabilize TiO ₂ NO ₃ ^- in a primary sol state. In this case, other than citric acid, polybasic carboxylic acids having a hydroxyl group (-OH), such as glucaric acid, gluconic acid, glucuronic acid, and glyceric acid, may be used. The primary reason for stabilizing TiO ₂ NO ₃ ^- in the sol state is secondary stabilization to control the rapid rise in reaction temperature when preparing a salt solution.

Meanwhile, a salt solution was prepared by adding 5 ml of each of LiNO ₃ and Al(NO ₃ ) _3. H ₂ O to the stabilized TiO ₂ NO ₃ ^- . At this time, the amount of LiNO ₃ and Al(NO ₃ ) _3. H ₂ O is added according to the stoichiometry capable of reacting with TiO ₂ NO ₃ ^- based on stoichiometry. Meanwhile, 10 ml of NH ₄ H ₂ PO ₄ was added to the prepared salt solution to form a sol, and the formed sol was stirred for 20 minutes to 1.5 hours to form a gel. At this time, if the stirring time is less than 20 minutes, the sol state does not change to a gel and finally powder cannot be formed. do. The formed gel is dried at 80 to 120 ° C for 30 minutes to 2 hours to remove moisture, and then heat-treated at 600 to 1000 ° C for 2 to 6 hours. At this time, if the drying time is less than 30 minutes at 80 ℃ or less, the moisture inside the powder cannot be sufficiently removed, and if it is dried for more than 2 hours at 120 ℃, the crystallization of the powder is accelerated by the supplied heat energy, resulting in crystal growth. Control it because it is done. On the other hand, the dried powder is heat-treated to form a crystal structure. When heat-treated at 600 ° C for 2 hours or less, crystallization of the powder does not occur and the ion conductivity decreases. When heat-treated at 1000 ° C for 6 hours or more, crystallization After that, since crystal growth is made and the ion conductivity is lowered, it is controlled. Meanwhile, the heat-treated powder is pulverized through a ball mill to obtain a final powder. At this time, the ball mill may use one or more of jet mill, planetary mill, attritor, and spex (Zet mill, Planatery, Attritor, Spex), and the ball mill speed is preferably 200 to 300 rpm rather than 100 to 500 rpm. A powder is obtained by ball milling for 30 minutes to 2 hours, more preferably 40 minutes to 1 hour. If the ball mill speed is 100 rpm for 30 minutes or less, the powder is not sufficiently pulverized and the ionic conductivity decreases due to the uneven particle size, so it is limited. Since the ionic conductivity decreases, it should be limited.

On the other hand, each prepared LLZ and LTAP is heat treated at 200 to 600 ° C, more preferably 400 to 500 ° C for 5 minutes to 2 hours, more preferably 10 minutes to 1 hour, and the process is repeated twice. At this time, when the temperature is less than 200 ℃ for 5 minutes or less, there is a problem that the solid electrolyte powder does not grow particles, and the interface itself acts as resistance to lower the ion conductivity. Conversely, it is limited because there is a problem in that the grain growth becomes too large during the final post-heat treatment.

On the other hand, the heat-treated powder is produced in the form of spherical or square pellets by applying pressure for 1 to 30 minutes at a pressure of 20 to 100 MPa, preferably 30 to 60 MPa, respectively. At this time, if the pressure is less than 20MPa for less than 1 minute, the strength of the pellet decreases and it is easily broken, so it is limited. .

On the other hand, each manufactured pellet is bonded with a binder through pressure to finally prepare a hybrid solid electrolyte. The binder used at this time is coated on each pellet using a spray, doctor blade method, spin coating method, etc., and the coating method is not limited at this time. As for the binder that can be used at this time, a mixed solution containing PEO, ACN, and LiC104 may be used as a PEO solid electrolyte binder, and a conductive material may be polyethylene oxide, polyethylene glycol, or polypropylene oxide. ), polyphosphazene, polysiloxane, and copolymers thereof.

On the other hand, each of the electrodes coated with the binder and the conductive material is made into spherical or square pellets by applying pressure for 1 to 30 minutes at a pressure of 30 to 60 MPa more preferably than 20 to 100 MPa. At this time, if the pressure is less than 20MPa for less than 1 minute, the strength of the pellet decreases and it is easily broken, so it is limited. .

1 shows the crystal structures of LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) and LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) of JCPDS and LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ prepared by the present invention). ) powder and LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) XRD diffraction pattern analysis results can be seen. As can be seen from the results, it can be confirmed that the prepared powders have LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ and LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) tetragonal crystal structures, respectively.

Figure 2 is a cross section SEM picture of the electrode manufactured according to the present invention, and it has a spherical particle size of 4 ~ 6um, and it can be confirmed that LTAP and LLZ are formed through the interfacial layer, respectively. Since spherical particles are easy to improve ionic conductivity, the ion conductivity of LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ /LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) prepared according to the present invention can be improved. can confirm that it can.

On the other hand, Figure 3 shows the results of measuring the ionic conductivity of the powder prepared according to the present invention, the area and thickness obtained from the diameter of the solid electrolyte sample, and the resistance of the bulk electrolyte are substituted into the formula to obtain 5.58x10 ^-4 ( Ω cm) The ionic conductivity value of ^-1 was measured, and it can be confirmed that the ionic conductivity has improved more than 10 times compared to the existing NASICON (10 ^-5 ( Ω cm) ^-1 .

Claims (5)

mixing Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ powders in the same molar ratio by weight;
Adding La ₂ O ₃ to the mixed powder in an increased amount of 10 wt % to prevent loss of lithium;
Putting the mixed powder into a 2-propanol bowl and reacting by wet milling;
drying the wetted reactant formed into sol;
Step of heat-treating the dried powder in two stages and grinding;
LLZ powder is prepared through, and subsequently
mixing a TiCl ₄ (99%, Aldrich) solution with distilled water to form TiO(OH) ₂ ;
Filtering the precipitated TiO(OH) ₂ precipitate and washing with Nitric acid (65%, aldrich);
Stabilizing TiO ₂ NO ₃ ^- prepared through Nitric acid washing with citric acid (Citric acid monohydrate, C ₆ H ₈ O ₇ );
preparing a salt by adding LiNO ₃ and Al(NO ₃ )3.H ₂ O to stabilized TiO ₂ NO ₃ ⁻ ;
forming a sol by adding NH ₄ H ₂ PO ₄ to the prepared salt (solution);
stirring the formed sol to form a gel;
LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ ) oxide is prepared by drying, heat-treating, and pulverizing the formed gel
Steps for preparing LLZ powder and LTAP powder by
Heat-treating the prepared powder to produce round or square pellets;
Heat-treating the prepared pellets at high temperature again to finally prepare a hybrid type film-type solid oxide electrolyte in the form of a film;
Among the prepared hybrid solid electrolytes, using LTAP as a positive electrode and LLZ as a negative electrode facing lithium;
LTAP (Li _1.5 Ti _1.5 Al _0.5 (PO ₄ ) ₃ )/LLZ (Li ₇ La ₃ Zr ₂ O ₁₂ ) solid electrolyte manufacturing method for hybrid oxide all-solid-state battery through The method of claim 1,
Materials used in wet milling are 2-propanol (2-Propanol), dimethylcarbinol (Dimethylcarbinol), β-hydroxypropane (β-Oxy-propan), 2-hydroxy A solid electrolyte manufacturing method using a material consisting of one or more mixtures of propane (2-hydroxypropane, 2-Oxypropan), The method of claim 1,
A solid electrolyte manufacturing method in which Li2CO3, La2O3, and ZrO2 are mixed at a molar ratio of 0.2 to 0.5:0.2 to 0.4:0.1 to 0.6, and wet milling is performed by adding 5 to 20 wt% of Li2CO3 in a weight ratio to suppress lithium loss The method of claim 1,
A method of producing a solid electrolyte by drying the sol obtained after wet milling at 60 to 120 ° C for 1 to 24 hours to obtain a powder The method according to claim 1, wherein the first heat treatment is performed at 700 to 1100 ° C for 4 to 8 hours, followed by a second heat treatment, and at this time, heat treatment is performed at 1150 to 1350 ° C for 4 to 8 hours to obtain a solid electrolyte. manufacturing method

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