KR102562150B1 - Garnet-based solid state electrolyte for lithium secondary battery including the sintering additives and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a garnet-based all-solid electrolyte for a lithium secondary battery including a sintering additive and a method for manufacturing the same. The sintering additive is used to lower the sintering temperature required for preparing the electrolyte and improve the density of the all-solid electrolyte, thereby providing Li during electrolyte sintering. It prevents volatilization and provides an all-solid electrolyte with high ionic conductivity.

Description

Garnet-based solid state electrolyte for lithium secondary battery including the sintering additives and manufacturing method of the same}

The present invention relates to a garnet-based all-solid electrolyte for a lithium secondary battery including a sintering additive and a manufacturing method thereof.

A secondary battery refers to a battery that can be reused a certain number of times or more through charging after use of the battery, and includes a nickel-cadmium battery, a lead storage battery, and a lithium secondary battery. Among them, the lithium secondary battery has a high energy density and a very high capacity-to-weight ratio, so it has been at the center of the secondary battery market to date.

In particular, lithium secondary batteries are free from the memory effect in which the maximum capacity of the battery decreases when recharged in a state where the discharge generated in the conventional secondary battery is not sufficient, and has been continuously used in batteries for small electronic devices due to its high electromotive force. Demand is rapidly increasing with the expansion of the pie in the medium and large battery markets such as automobiles and ESS (Energy Storage System). However, although safety is given the highest priority in medium and large batteries, the fact that organic electrolytes used in conventional lithium secondary batteries are vulnerable to fire has emerged as a problem, and technological development is required.

Currently commercially available and widely used lithium secondary batteries mainly use organic electrolytes or organic polymer electrolytes, but such organic materials have a disadvantage in that they are easily exposed to fire in a high temperature and high humidity environment. Electrolytes using organic polymers require a slightly higher process and cost compared to organic electrolytes, but have the advantage of maintaining more stable performance in a high temperature and high humidity environment. However, organic polymer electrolytes have a very low ion conductivity, and thus have a disadvantage in that they are difficult to function in a low temperature environment, and are therefore not suitable for batteries for electric vehicles.

As a way to solve this problem, research and development on inorganic all-solid electrolytes with high ion conductivity and chemical stability are being accelerated. Inorganic all-solid electrolytes are largely divided into sulfide-based and oxide-based. Sulfide-based all-solid electrolytes have a high ion conductivity, but react with the atmosphere to emit hydrogen sulfide, a toxic gas.

On the other hand, oxide-based all-solid electrolytes tend to have slightly lower ionic conductivity than sulfide-based electrolytes, but have the advantage of being free from environmental pollution problems, and research and development for practical use by increasing their ionic conductivity are actively progressing.

Among them, the most representative is an all-solid electrolyte LLZO (Li ₇ La ₃ Zr ₂ O ₁₂ ) having a Garnet structure, which has the advantage of having relatively high ionic conductivity. However, in order to increase the ionic conductivity of LLZO to a level that can be used in practice, it must be sintered at a high temperature for a long time, resulting in a very long process cost and time. At this time, volatilization of Li occurs due to sintering for a long time, and ionic conductivity is further reduced, so that the reproducibility of the electrolyte is lowered, the density is reduced, and a chemically unstable material is produced. In order to solve these problems, research on a method for increasing the density of the electrolyte while reducing the sintering temperature and at the same time reducing the sintering time is required.

Republic of Korea Patent Registration No. 10-1935218 (2021.12.13.) Republic of Korea Patent Registration No. 10-2038621 (2019.10.24.) Republic of Korea Patent Registration No. 10-2280683 (2021.07.16.)

In order to solve the above problems, an object of the present invention is to provide a garnet-based all-solid electrolyte for a lithium secondary battery including a sintering additive and a manufacturing method thereof.

The present invention relates to a method for providing a garnet-based all-solid electrolyte for a lithium secondary battery, wherein the garnet-based all-solid electrolyte for a lithium secondary battery is a metal oxide electrolyte composed of oxides of Li, La, Zr and Ta, and Al, Bi and Cu It may include a sintering additive made of any one or more metal oxides.

In this case, the metal oxide electrolyte may be composed of 24 to 28 atomic% Li, 11 to 13 atomic% La, 4 to 7 atomic% Zr, 1 to 4 atomic% Ta, and the balance O.

The garnet-based all-solid electrolyte for a lithium secondary battery may include 5 parts by weight or less of the sintering additive based on 100 parts by weight of the metal oxide electrolyte.

The garnet-based all-solid electrolyte for a lithium secondary battery may have an ion conductivity of 1.0×10 ^-4 S cm ^-1 or more.

The present invention is a method for producing the above garnet-based all-solid electrolyte for a lithium secondary battery, (A) 400 to 800 parts by weight of La ₂ O ₃ and 75 to 130 parts by weight of ZrO ₂ based on 100 parts by weight of LiOH , Preparing a powder such that Ta ₂ O ₅ is 120 to 200 parts by weight, and mixing them to prepare a mixed powder; (B) adding a sintering additive to the mixed powder and milling; and (C) sintering the milled powder.

In the step (A), ball milling may be performed on the powder, followed by drying and calcination.

In the step (A), the ball mill may be performed by introducing powders of LiOH, La ₂ O ₃ , ZrO ₂ and Ta ₂ O ₅ into an organic solvent.

In the step (A), the calcination of the powder may be performed by maintaining a temperature of 600 to 900 ° C. for 6 to 12 hours.

In step (B), the sintering additive may be one or more selected from among Al ₂ O ₃ , CuO and Bi ₂ O ₃ .

In the step (B), the sintering additive is included in an amount of 5 parts by weight or less with respect to 100 parts by weight of the garnet-based all-solid electrolyte for a lithium secondary battery. Method for producing a garnet-based all-solid electrolyte.

In addition, the present invention provides a lithium secondary battery including the garnet-based all-solid electrolyte for a lithium secondary battery.

The garnet-based all-solid electrolyte for a lithium secondary battery according to the present invention performs sintering of electrolyte particles using a sintering additive, thereby improving the density of the electrolyte and increasing ion conductivity, and sintering is performed at a lower temperature than the prior art Even when this is done, there is an effect of increasing the density of the particles.

1 shows XRD (X-Ray Diffraction) measurement results of Examples before sintering.
Figure 2 shows the XRD measurement results of the examples after sintering.
Figure 3 shows the results of measuring EIS (Electrochemical Impedance Spectroscopy) of Examples and Comparative Examples sintered at 1100 °C.
Figure 4 shows the results of measuring the EIS of Examples and Comparative Examples sintered at 1000 ° C.

Hereinafter, a garnet-based all-solid electrolyte for a lithium secondary battery including a sintering additive according to the present invention and a manufacturing method thereof will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Therefore, the present invention may be embodied in other forms without being limited to the drawings presented below, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used in the present invention, they have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, and in the following description and accompanying drawings, the present invention Descriptions of well-known functions and configurations that may unnecessarily obscure the gist of will be omitted.

The present invention relates to a method for providing a garnet-based all-solid electrolyte for a lithium secondary battery, wherein the garnet-based all-solid electrolyte for a lithium secondary battery is a metal oxide electrolyte composed of oxides of Li, La, Zr and Ta, and Al, Bi and Cu It may include a sintering additive made of any one or more metal oxides.

At this time, the metal oxide electrolyte is composed of 24 to 28 atomic% Li, 11 to 13 atomic% La, 4 to 7 atomic% Zr, and 1 to 4 atomic% Ta, the balance being O, and the chemical formula is Li _{7 -x} La ₃ Zr _2-x Ta _x O ₁₂ (0<x<1). These metal oxide electrolytes have higher ionic conductivity and lower charge-transfer resistance than Li ₇ La ₃ Zr ₂ O ₁₂ all-solid electrolytes represented by the conventional LLZO system, which can further improve the performance of lithium secondary batteries. can Here, the ion conductivity may mean conductivity of Li ions in particular.

The sintering additive is one or more metal oxides selected from Al, Bi, and Cu, and may be added within 5 parts by weight based on 100 parts by weight of the metal oxide electrolyte in the garnet-based all-solid electrolyte for a lithium secondary battery. The garnet-based all-solid electrolyte for a lithium secondary battery contains a sintering additive that is an oxide of one or more metals selected from Al, Bi, and Cu as described above, thereby stabilizing the crystal structure and improving the sintering characteristics, thereby increasing the ion conductivity of the all-solid electrolyte can be improved In this case, the sintering characteristics may mean the degree to which particles are sintered when sintering is performed at a specific temperature.

In this way, in order to improve the sintering characteristics of the all-solid-state electrolyte for a lithium secondary battery, 0.1 to 2.0 atomic percent of a metal in the electrolyte may be substituted with one or more metals selected from Al, Bi, and Cu. At this time, it is preferable to use Al and Bi together as such a substitution metal. In this case, the temperature required for sintering can be significantly lowered, and the density and sintering characteristics of the electrolyte are further improved during sintering, so that the ionic conductivity of the all-solid electrolyte can be greatly improved.

At this time, when the contents of Al, Bi, and Cu are smaller than the above ranges, sintering properties may hardly be improved, and when larger than the above ranges, sintering properties may be further improved. It is not good to have adverse effects such as deterioration of ionic conductivity due to a decrease in conductive parts or decrease in stability of the lattice structure, which may cause the lattice structure to collapse during actual use of the battery and reduce the usable area.

The garnet-based all-solid electrolyte for a lithium secondary battery may have an ion conductivity of 1.0×10 ^-4 S cm ^-1 or more. In this case, the ionic conductivity may be preferably 2.5×10 ^-4 S cm ^-1 or more, more preferably 4.0×10 ^-4 S cm ^-1 or more. One of the reasons for the difficulty in using the conventional all-solid electrolyte is that the capacity of the battery is very small because the ionic conductivity is lower than that of the liquid electrolyte, but the present invention can further improve the capacity of the battery by having such a high ionic conductivity.

The present invention is a method for producing the above garnet-based all-solid electrolyte for a lithium secondary battery, (A) 400 to 800 parts by weight of La ₂ O ₃ and 75 to 130 parts by weight of ZrO ₂ based on 100 parts by weight of LiOH , Preparing a powder such that Ta ₂ O ₅ is 120 to 200 parts by weight, and mixing them to prepare a mixed powder; (B) adding a sintering additive to the mixed powder and milling; and (C) sintering the milled powder.

In step (A), 400 to 800 parts by weight of La ₂ O ₃ , 75 to 130 parts by weight of ZrO ₂ , and 120 to 200 parts by weight of Ta ₂ O ₅ were mixed with respect to 100 parts by weight of LiOH. it may be A composition as described above may be obtained by preparing an electrolyte by mixing materials within this range.

In this case, the amount of LiOH mixed in the step (A) may be added in excess of the amount calculated from the stoichiometry of the composition of the garnet-based all-solid electrolyte for a lithium secondary battery as described above. This is because Li volatilization occurs during drying, calcination, and subsequent sintering of the electrolyte. If an excessive amount of LiOH is not added, the composition content of Li in the electrolyte is insufficient, resulting in a decrease in Li ionic conductivity in the electrolyte and phase separation of the electrolyte. It's not good because it can happen.

In this case, the amount of LiOH added in excess may be 10 to 30% of the amount of LiOH calculated stoichiometrically in the garnet-based all-solid electrolyte for a lithium secondary battery. By further adding LiOH within this range, the composition range of the garnet-based all-solid electrolyte for a lithium secondary battery may be satisfied. However, when the above amount is exceeded, the effect of preparing for Li volatilization as described above is not better, which is not preferable in terms of cost and stoichiometry.

In the step (A), ball milling may be performed on the powder, followed by drying and calcination.

The ball mill may be wet milling, which is performed by adding powders of LiOH, La ₂ O ₃ , ZrO ₂ and Ta ₂ O ₅ to an organic solvent. At this time, more specifically, it may be to use an anhydride having a water content of less than 1 ppm as an organic solvent. By performing wet milling using such an organic solvent, a phenomenon in which Li ₂ CO ₃ is formed due to moisture in the solvent can be prevented. If Li ₂ CO ₃ is generated, it is preferable to perform wet milling as described above because it does not react with the La ₂ O ₃ and ZrO ₂ and remains as an impurity that does not conduct Li ions, lowering the ionic conductivity of the solid electrolyte. In addition, when water is used as a solvent, LiOH having a high ionization degree is dissolved in the above powder, and the reaction is not properly performed, so that the Li content in the electrolyte is insufficient, and the conductivity of Li ions may decrease, and the stability of the lattice structure may be reduced. It's not good because it can decrease.

Therefore, it is preferable to use an anhydride having a moisture content of less than 1 ppm as the organic solvent, and the type of the organic solvent is not particularly limited. Absolute ethanol can be used. However, since methanol is hygroscopic and has an azeotrope with water, it is not easy to manufacture anhydrous methanol, so the advantages obtained in the process compared to the investment cost compared to anhydrous ethanol are small.

At this time, the ball mill may be performed for 8 to 20 hours at 100 to 500 rpm. In addition, the ball used in the ball mill is preferably a zirconia ball, and preferably has a diameter of 1 to 10 mm.

As described above, after the wet ball milling of the powder is performed, a step of drying the powder may be performed. Drying of the powder may be performed at a temperature of 60 to 120 ℃. By removing anhydrous ethanol by performing drying in this temperature range, the metal oxide electrolyte particles are not agglomerated and the formation of bubbles and pores can be reduced during the subsequent calcination of the powder.

Subsequently, calcination of the powder may be performed by maintaining a temperature of 600 to 900 ° C. for 6 to 12 hours. At this time, preferably, the calcination temperature of the powder may be 650 to 900 ° C, more preferably 700 to 900 ° C. Also, preferably, the calcination of the powder is performed for 7 to 12 hours, more preferably for 8 to 12 hours. By performing the calcination of the powder under such conditions, the composition of the metal oxide electrolyte particles becomes more uniform, and aggregation of the particles can be prevented in a subsequent sintering process.

In step (B), the sintering additive may be one or more selected from among Al ₂ O ₃ , Bi ₂ O ₃ and CuO. At this time, it is preferable to use Al ₂ O ₃ and Bi ₂ O ₃ . By using such a sintering additive, the proper sintering temperature can be lowered by about 100 ° C. compared to the prior art. At this time, the appropriate sintering temperature is the temperature required for the garnet-based all-solid electrolyte particles for lithium secondary batteries to be sintered to have high ionic conductivity. ) can be observed indirectly through means such as For example, when the degree of sintering of the electrolyte is high, the impedance (resistance) component of the EIS becomes smaller, and in the opposite case, the impedance component of the EIS becomes larger.

In addition, in the step (B), the sintering additive may be added within 5 parts by weight based on 100 parts by weight of the metal oxide electrolyte. By including the sintering additive within this range, the formation of a secondary phase in the electrolyte is prevented, and the ionic conductivity can be further improved. The secondary phase may occur when Li is excessively volatilized during a sintering process during the manufacture of a garnet-based all-solid electrolyte for a lithium secondary battery, and a phase such as La-Zr may be formed. Such a secondary phase cannot conduct Li, and phase separation occurs with the garnet-based all-solid electrolyte for lithium secondary batteries, which can have a very adverse effect on the performance of the electrolyte, such as resistance and ionic conductivity. The present invention can prevent the formation of such a secondary phase by lowering the sintering temperature and shortening the required time through the sintering additive.

For this effect, the sintering additive is preferably added within 4.5 parts by weight, more preferably within 4 parts by weight, based on 100 parts by weight of the metal oxide electrolyte. The lower limit of the amount of the sintering additive is not particularly limited, but it is preferable to include at least 0.5 parts by weight or more, more preferably 1 part by weight or more in order to exhibit the above effects. However, when added in excess of the above range, the ionic conductivity of the electrolyte may be lowered and the lattice structure may become unstable, which is not good.

In the step (C), the sintering may be performed at 900 to 1200 ° C. for 6 to 12 hours. In this case, preferably, the sintering is performed at 925 to 1175 ° C, more preferably at 950 to 1150 ° C. By performing sintering at such a temperature, it is possible to prepare an all-solid electrolyte having excellent electrochemical characteristics due to high density and high ionic conductivity while minimizing volatilization of Li. At this time, as described in the description of step (B), if the sintering temperature is too high, the volatilization of Li is accelerated and the amount of secondary phase such as La-Zr is increased, resulting in an increase in physical properties such as ionic conductivity and physical strength of the electrolyte. At a temperature lower than this, sintering of the particles does not occur easily, which is undesirable because the intergranular resistance of the electrolyte is very high.

In addition, the present invention provides a lithium secondary battery including the garnet-based all-solid electrolyte for a lithium secondary battery.

The lithium secondary battery may include a cathode; cathode; and the garnet-based all-solid electrolyte for a lithium secondary battery, wherein the garnet-based all-solid electrolyte for a lithium secondary battery may be positioned between the positive electrode and the negative electrode.

The cathode may include a cathode active material; conductive material; bookbinder; And it may include a positive electrode current collector.

The cathode active material is a metal oxide containing lithium, specifically LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ , LiFe _1-x M _x PO ₄ (M is a divalent or trivalent transition metal), LiCoO ₂ , LiMnO ₂ , LiNiO ₂ LiMn ₂ O ₄ , LiNi _1-x Co _x O ₂ , LiNi _x Co _y Mn _z O ₂ (x+y+z=1), LiNi _x Co _y Al _z O ₂ (x+y+z=1) , LiNi _x Mn _y Mt _z O ₂ (x+y+z=1, Mt is a divalent or trivalent transition metal), Li _1.2 Ni _0.13 Co _0.13-x Mn _0.54 Al _x O _2(1-y) F _2y (x, y are real numbers from 0 to 0.05 independent of each other), Li _1.2 Mn _(0.8-a) Mt _a O ₂ (Mt is a divalent or trivalent transition metal), a(Li ₂ MnO ₃ )*b(LiNi _x Co _y Mn _z O ₂ )(a+b=1, x+y+z=1), Li ₂ Nt _1-x Mt _x O ₃ (Nt is a divalent, trivalent or tetravalent transition metal, Mt is divalent or trivalent transition metal), Li _1+x Nt _yz Mt _z O ₂ (Nt is Ti or Nb, Mt is V, Ti, Mo or W), Li _x Mt _2-x O ₂ (Mt is Ti, A transition metal oxide containing lithium composed of a transition metal such as Zr, Nb, or Mn) and Li ₂ O/Li ₂ Ru _1-x Mt _x O ₃ (Mt is a transition metal such as Ti, Zr, Nb, or Mn). Any one or a mixture of two or more selected from the group may be used, but this is only an example and is not necessarily limited thereto.

The conductive material is used to impart conductivity to the electrode, and is excellent in chemical stability and has electronic conductivity. Specific examples include graphite, carbon black, super blood, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, carbon nanotube, carbon nanowire, graphene, graphitized mesocarbon microbeads , carbon-based materials such as fullerene and amorphous carbon; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives, and the like, and one or a mixture of two or more of them may be used, but this is only an example and is not necessarily limited thereto.

The binder imparts adhesion between the cathode active material, the conductive material and the cathode current collector, and specific examples include polyvinylidene fluoride (PVdF), polyimide (PI), fluoropolyimide (FPI), polyacrylic acid (PAA) , polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), tetrafluoroethylene (PTFE), polyethylene, polypropylene, polyurethane, ethylene-propylene-diene polymer (EPDM), sulfonated ethylene-propylene-diene polymer (S-EPDM), styrene-butadiene rubber (SBR), fluororubber or copolymers thereof, algin, and the like, among which Any one or more selected may be used, but this is only an example and is not necessarily limited thereto.

The cathode current collector provides an electrical passage between the cathode active material and the power source, and may be made of aluminum processed into an aluminum foil or aluminum mesh.

The negative electrode may include a negative electrode active material, a conductive material, a binder, and a negative electrode current collector.

The anode active material is a material capable of storing lithium ions, and includes carbon-based materials such as graphite, activated carbon, hard carbon, and soft carbon; and lithium metal; It may be to use any one selected from, but this is only an example and is not necessarily limited thereto. At this time, since the specific capacity and energy density of the battery can be greatly increased, it is preferable to use lithium metal as an anode active material.

Since the conductive material and the binder are the same as those described above, overlapping descriptions will be omitted.

The anode current collector provides an electrical passage between the anode active material and the power source, and may be made of copper processed into a copper foil or copper mesh.

Hereinafter, the sintering additive according to the present invention, a method for manufacturing a garnet-based all-solid electrolyte for a lithium secondary battery using the same, and a garnet-based all-solid electrolyte for a lithium secondary battery prepared therefrom will be described in more detail through examples. However, the following examples are only one reference for explaining the present invention in detail, but the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the present invention. In addition, the unit of additives not specifically described in the specification may be % by weight.

[Example]

LiOH, La ₂ O ₃ , ZrO ₂ and Ta ₂ O ₅ powders were weighed and mixed to match the composition ratio of Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ . At this time, the LiOH powder was increased by 20% from the above weighed amount and mixed to prevent the formation of a La—Zr secondary phase due to an insufficient Li content due to volatilization of Li. The powder mixed as above was put into absolute ethanol together with a zirconia ball, and wet milling was performed at 200 to 250 rpm for 12 hours.

After completion of the wet milling of the mixed powder, absolute ethanol was evaporated in an oven maintained at about 100° C., and then the remaining powder was calcined at 900° C. for 12 hours.

Next, with respect to 100 parts by weight of the powder, 1.5 parts by weight of Al ₂ O ₃ and 2 parts by weight of Bi ₂ O ₃ were added and ball milled, and the ball milled powder was put into a mold, flattened, and pressed to obtain a diameter of 12 mm. Phosphorus pellets were produced. At this time, the pressurization was performed for 3 minutes by applying a pressure of 2 Ton.

[Comparative example]

All procedures were performed in the same manner as in Example, but Al ₂ O ₃ and Bi ₂ O ₃ were not added.

[Characteristic evaluation method]

A. Crystal structure analysis

Referring to Figure 1, it can be confirmed the XRD (X-Ray Diffraction) measurement results after calcination of the embodiment. Comparing this with JCPDS (Joint Committee on Powder Diffraction Standards) data of LLZTO having a cubic structure, it can be seen that the positions of the peaks coincide and the peaks are formed narrowly and sharply. From this, it can be seen that it has the same crystal structure as LLZTO at the time immediately after calcination, and that the crystal structure is very dense.

Referring to Figure 2, it can be confirmed the XRD measurement results performed after sintering the embodiment at 1000 ℃. Comparing this with the JCPDS data of LLZTO having a cubic structure, it can be seen that the peak position is consistent and the peak width slightly increased, but the crystal structure remains the same.

B. Measurement of ionic conductivity

A total of 4 specimens were prepared by sintering Examples and Comparative Examples at 1000 ° C and 1100 ° C for 12 hours, respectively. The specimen was mirror polished using #600, 1000, 1500, 2000, and 4000 sandpaper, and electrodes were deposited on both sides of the specimen through dry Au sputtering. Such an Au electrode serves as a blocking electrode in the experiment.

EIS (Electrochemical Impedance Spectroscopy) measurement was performed by setting the amplitude to 0.1V in the frequency range of 9MHz to 1Hz at OCP (Open Circuit Potential). Based on the measured EIS results, the total resistance (R) of the electrolyte was obtained, and the ionic conductivity (σ) was calculated from the thickness (t) and width (A) of the specimen through the following formula.

σ (Ω cm) ^-1 = (1/R)(t/A)

The ionic conductivity calculation results are shown in Table 1.

Ionic conductivity (Ω cm) ^-1 Example (sintering at 1100°C) 5.512 × 10 ^-4 Example (sintering at 1000°C) 4.630 × 10 ^-4 Comparative Example (sintering at 1100°C) 2.084 × 10 ^-4 Comparative Example (sintering at 1000°C) 2.120 × 10 ^-4

Referring to Table 1, regardless of the sintering temperature, it can be seen that the ionic conductivity of the examples is more than twice as high as that of the comparative examples.

In addition, referring to FIG. 3 , it can be seen that the x-intercept of Comparative Example has a lower resistance value than the x-intercept of Example, and it can be seen that the size difference of the formed semicircles is large. Furthermore, referring to FIG. 4 , it can be seen that the size of the semicircle of the comparative example is very large, making it difficult to recognize the change in the example.

Through the above EIS measurement results, the comparative example does not have a very large increase in ionic conductivity when sintering at 1000 ° C, but the density of the all-solid electrolyte is lowered and the resistance is increased to the extent that practical use is difficult, so that sintering is well performed at 1000 ° C. It can be inferred that this has not been done. On the other hand, in the case of sintering at 1000 ° C., the ion conductivity slightly decreases in the examples, but the change in density and resistance is not so large, so it can be seen that the temperature conditions required for sintering are alleviated compared to the comparative examples.

Although the present invention has been described through specific details and limited examples as described above, these are only provided to help the overall understanding of the present invention, and the present invention is not limited to the above examples, and the field to which the present invention belongs Those skilled in the art can make various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and it will be said that not only the claims to be described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the present invention. .

Claims (13)

In the garnet-based all-solid electrolyte for lithium secondary batteries,
A metal oxide electrolyte composed of 24 to 28 atomic% Li, 11 to 13 atomic% La, 4 to 7 atomic% Zr, and 1 to 4 atomic% Ta, and the remainder being O;
A garnet-based all-solid electrolyte for a lithium secondary battery comprising a sintering additive composed of Al ₂ O ₃ and Bi ₂ O ₃ . delete According to claim 1,
A garnet-based all-solid electrolyte for a lithium secondary battery, characterized in that it contains within 5 parts by weight of the sintering additive based on 100 parts by weight of the metal oxide electrolyte. According to claim 1,
The garnet-based all-solid electrolyte for lithium secondary batteries has an ion conductivity of 1.0×10 ^-4 S cm ^-1 or more. As a method for manufacturing a garnet-based all-solid electrolyte for a lithium secondary battery,
The manufacturing method,
(A) preparing powders of LiOH, La ₂ O ₃ , ZrO ₂ , and Ta ₂ O ₅ and mixing them to prepare a mixed powder;
(B) adding a sintering additive composed of Al ₂ O ₃ and Bi ₂ O ₃ to the mixed powder and milling; and
(C) sintering the milled powder by maintaining it at 925 to 1100° C. for 6 to 12 hours;
Method for producing a garnet-based all-solid electrolyte for a lithium secondary battery comprising a. According to claim 5,
In step (A), powder is prepared by increasing LiOH in an amount of 10 to 30% by weight relative to the stoichiometric equivalent of the garnet-based all-solid electrolyte for lithium secondary battery Preparation of a garnet-based all-solid electrolyte for a lithium secondary battery method. According to claim 5,
In step (A), the method for producing a garnet-based all-solid electrolyte for a lithium secondary battery, characterized in that performing a ball mill on the powder and then further performing drying and calcination. According to claim 7,
In step (A), a ball mill is performed by adding LiOH, La ₂ O ₃ , ZrO ₂ and Ta ₂ O ₅ powder to an organic solvent. According to claim 7,
In step (A), the calcination of the powder is performed by maintaining a temperature of 600 to 900 ° C. for 6 to 12 hours. delete According to claim 5,
In step (B), the sintering additive is added in an amount of less than 5 parts by weight based on 100 parts by weight of the mixed powder. delete A lithium secondary battery comprising the garnet-based all-solid electrolyte for a lithium secondary battery according to any one of claims 1, 3, and 4.