KR101627848B1 - Solid electrolyte for all solid state rechargeable lithium battery, method for preparing the same, and all solid state rechargeable lithium battery including the same - Google Patents

Abstract

There is provided a solid electrolyte for a lithium secondary battery represented by the following Chemical Formula 1, a process for producing the same, and a lithium secondary battery comprising the same.
[Chemical Formula 1]
Li _{5 + x} (M ¹ ) ₃ (M ² ) ₂ O _{12 - y} N _y
In Formula 1, the definitions of M ¹ , M ² , x and y are as described in the specification.

Description

TECHNICAL FIELD The present invention relates to a solid electrolyte for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the lithium secondary battery. BACKGROUND ART [0002]

The present invention relates to a solid electrolyte for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the solid electrolyte.

Conventional lithium-ion batteries use liquid electrolytes basically, and safety problems about explosion and ignition are constantly occurring. To solve these problems, many researches have been made, but there are still ways to solve them fundamentally I can not. Generally, in the case of a lithium ion battery using an oxide-based cathode active material, when the temperature of the battery instantaneously rises due to overcharge of the anode or short-circuit of the battery, the cathode active material decomposes and oxygen is generated. In this case, Which may cause swelling, explosion or fire. One of the most popular ways to solve this safety problem is to convert the organic electrolyte, which is a fuel, into a solid electrolyte so that explosion / ignition is not fundamentally generated.

The use of a solid electrolyte can solve safety problems by blocking the root cause of explosion / ignition, 2) it is possible to use a high voltage cathode material and a metal lithium as an anode material because of wide potential window, Theoretically, it is possible to increase the energy density 2-3 times. 3) In addition, since the present LiB degassing process can be omitted in the manufacturing process, the process yield can be improved and cost reduction can be realized through simplification.

However, despite these advantages, commercialization of the oxide-based solid electrolyte into the battery was almost impossible due to its low ionic conductivity. The idea of this remarkable improvement was proposed by Dr. J.Bates of Oak Ridge National Laboratory, USA, and Li ₃ PO ₄ The target was ion- _exchanged with nitrogen (Li ₃ PO _{3 .4} N _{0 .17} ) by reactive sputtering under a nitrogen atmosphere to increase the ionic conductivity by 100 times at 10 ^-8 S / cm to 10 ^-6 S / cm However, it greatly contributed to accelerating the commercialization of thin film batteries using sputtering. This is well described in U.S. Pat. No. 5,597,660.

In addition, Li ₃ BO ₃ In the case of Li ₃ BO _{2 .5} N _{0 .13} , which was replaced with nitrogen by reactive sputtering under the same nitrogen atmosphere using the target of the material, the ion conductivity was increased 200 times (KR 1047865).

However, such a method of producing an electrolyte is by vacuum deposition and can not be applied to a limited application field such as a smart card or a power source for MEMS driving. In order to realize a large-capacity all-solid-state battery, it is necessary to increase the amount of the cathode active material to be charged, which means that the battery must be manufactured by sintering the powdered electrolyte and the cathode active material together.

The present invention proposes a material providing a passage through which lithium ions can move more easily using a Garnet solid electrolyte, which is the most promising solid oxide ion conductor of all solid state batteries, and a manufacturing method thereof.

One embodiment of the present invention is to provide a solid electrolyte for a lithium secondary battery improved in ion conductivity.

Another embodiment of the present invention is to provide a method for producing the solid electrolyte for a lithium secondary battery.

Another embodiment of the present invention is to provide a lithium secondary battery including the solid electrolyte for the lithium secondary battery.

One embodiment of the present invention provides a solid electrolyte for a lithium secondary battery represented by the following general formula (1) .

[Chemical Formula 1]

Li _{5 + x} (M ¹ ) ₃ (M ² ) ₂ O _{12 - y} N _y

In Formula 1,

M ¹ is selected from the group consisting of La, Sr, Ba, Ca, In, Mg, Y, Sc, Cr,

M ² is Zr, Nb, Ta, Sb, Sn, Hf, Bi, W, Se, Ga, Ge,

0 < x? 2, and 0.001 < y <

M ¹ is La, M ² is Zr, x is 2, and y may be 0.005 <y <2.

The formula (1) may be represented by the following formula (2).

(2)

Li ₇ La ₃ Zr ₂ O _{10 .8} N _{1 .2}

The solid electrolyte for a lithium secondary battery may have an ionic conductivity of 8.0 X 10 &lt; ^-5 &gt; S / cm or more.

Another embodiment of the present invention is a process for producing a solid electrolyte comprising the steps of: preparing a solid electrolyte powder from Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ ; Preparing a solid electrolyte powder substituted with nitrogen from the solid electrolyte powder and the urea; And a step of preparing the nitrogen-substituted solid electrolyte powder with a pellet. The present invention also provides a method for producing a solid electrolyte for a lithium secondary battery.

The step of preparing the solid electrolyte powder includes mixing Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (mixing step); Crushing a mixture of Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (pulverizing step); A first firing step; And a second firing step.

The mixing step may mix Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ in a molar ratio of 3.7 to 4.4: 1.4 to 1.6: 1.9 to 2.1, respectively.

And drying the La ₂ O ₃ (drying step) before the mixing step.

The drying step may be performed at 700 to 1000 ° C for 12 to 24 hours.

The mixing step may further include adding an ammonia dispersant.

The first baking step may be performed at 850 to 950 ° C for 2 to 5 hours.

The second baking step may be performed at 1,100 to 1,250 ° C for 2 to 5 hours.

The step of producing the nitrogen-substituted solid electrolyte powder

Mixing the solid electrolyte powder and the urea; Crushing step; A first firing step; And a second firing step.

The step of mixing the solid electrolyte powder and the urea can be performed by mixing the solid electrolyte powder and the urea in a weight ratio of 1: 7: 4 to 6:

The pulverizing step may be a ball mill, a mortar, a sieve, an attrition mill, a disk mill, a jet mill, a jaw crusher, , A crusher, or a combination thereof.

The first baking step may be performed at a temperature of 400 to 500 ° C for 2 to 6 hours.

The second baking step may be performed at a temperature of 750 to 850 캜 for 3 to 6 hours.

The step of producing the nitrogen-substituted solid electrolyte powder with a pellet may include a compression step, a crushing step, and a firing step.

The compressing step may be carried out with an intensity of 1 to 3 tons / cm &lt; ² &gt;.

The firing step may be performed at a temperature of 800 to 950 DEG C for 3 to 6 hours.

Another embodiment of the present invention provides a pre-solid lithium secondary battery comprising a positive electrode and a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises the solid electrolyte described above.

The solid electrolyte layer may have a thickness of 0.1 to 1 mm.

A solid electrolyte for a lithium secondary battery improved in ion conductivity, a method of manufacturing the same, and a lithium secondary battery including the solid electrolyte can be realized.

1 is a schematic cross-sectional view of a lithium secondary battery according to one embodiment.
2 is a photograph of a solid electrolyte pellet for a lithium secondary battery according to an embodiment.
Fig. 3 shows XRD measurement results of the solid electrolyte according to Example 1 and Comparative Example 1. Fig.
4 is a graph showing the impedance measured at room temperature.
5 is an equivalent circuit used for CNLS fitting.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The solid electrolyte for a lithium secondary battery according to one embodiment may be represented by the following formula (1).

[Chemical Formula 1]

Li _{5 + x} (M ¹ ) ₃ (M ² ) ₂ O _{12 - y} N _y

In Formula ^1, M 1 is selected from the group consisting of La, Sr, Ba, Ca, In, Mg, Y, Sc, Cr, and combinations thereof, M ² is Zr, 0 < x? 2, and 0.001 < y < 3.

The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte for the lithium secondary battery is an oxide solid electrolyte, and the solid electrolyte is selected from the group consisting of Li, La, Sr, Ba, Ca, In, Mg, Y, Sc, Cr, Zr, Nb, Ta, Sb, Sn, Hf, Ga, Ge, and the like.

Particularly, by having a structure in which a part of oxygen is substituted with nitrogen, the crosslinking effect is increased in the Garnet-type structure, so that a solid electrolyte having a dense structure can be realized. Due to this compact structure improves the conductivity of the Li ion is expected, in fact the 8.0 X 10 ^-5 or more ionic conductivity is measured, conventional garnet structure the oxygen is not replaced with nitrogen (measured value: 6.0 X 10 ^-6) compared It was confirmed that the ionic conductivity was improved 10 times or more. That is, it can be seen that ion conductivity is greatly improved due to nitrogen substitution.

Specifically, M ¹ is La, M ² is Zr, x is 2, and y may be 0.005 <y <2. When the y value is within the above range, an optimum cross linking structure can be realized, so that the movement of Li ions in the electrolyte can be efficiently performed.

The ratio of Li, La, and Zr in the solid electrolyte is not particularly limited as long as it is a ratio that a solid electrolyte material having a Garnett structure can be obtained. Usually, Li: La: Zr = 7: 3: 2 . However, since this ratio is somewhat variable, it means Li: La: Zr = 7: 2.8 to 3.2: 1.8 to 2.2.

For example, the formula (1) may be represented by the following formula (2).

(2)

Li ₇ La ₃ Zr ₂ O _{10 .8} N _{1 .2}

When the content of Li is within the above range, it is possible to obtain an effect of preventing deficiency due to evaporation of Li during high-temperature sintering.

In another embodiment of the present invention, there is provided a method for producing a solid electrolyte, comprising the steps of: preparing a solid electrolyte powder from Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ ; Preparing a solid electrolyte powder substituted with nitrogen from the solid electrolyte powder and the urea; And a step of preparing the nitrogen-substituted solid electrolyte powder with a pellet.

In the above manufacturing method, by applying the element method of introducing nitrogen substitution from the element, nitrogen substitution can be attempted at a relatively low cost compared with the conventional plasma nitriding method, and since the vacuum process is not used, the mass production is improved by simplifying the manufacturing process . In addition, since the battery can be manufactured by sintering the positive electrode active material and the solid electrolyte powder, it is easy to increase the amount of the positive electrode active material, which is necessary for realizing a large capacity all-solid battery.

The step of preparing the solid electrolyte powder includes mixing Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (mixing step); Crushing a mixture of Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (pulverizing step); A first firing step; And a second firing step.

The mixing step may mix Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ in a molar ratio of 3.7 to 4.4: 1.4 to 1.6: 1.9 to 2.1, respectively.

The amount of Li ₂ CO ₃ in the mixed molar ratio should be designed so as to be contained in an amount of about 5 to 10% by weight over the theoretical amount of Li ₂ CO ₃ for producing the desired solid electrolyte, that is, Li ₇ La ₃ Zr ₂ . This is because Li is lost in the course of the production of the solid electrolyte, specifically in the firing process, and in order to maintain the molar ratio of Li: La: Zr = 7: 3: 2 in the final composition in consideration of the amount of Li to be eliminated .

And drying the La ₂ O ₃ (drying step) before the mixing step. Almost all of the moisture adsorbed on La ₂ O ₃ can be removed by drying La ₂ O ₃ at 700 to 1000 ° C. for 12 to 24 hours before mixing each powder. By removing moisture adsorbed on La ₂ O ₃ , an effect of obtaining a composition having an accurate molar ratio can be obtained.

The mixing step may further include adding an ammonia dispersant. By adding an ammonia dispersant, the mixing performance is improved and a uniform mixture can be obtained.

The first firing step of producing the solid electrolyte powder may be performed at 850 to 950 캜 for 2 to 5 hours and the second firing step may be performed at 1,100 to 1,250 캜 for 2 to 5 hours have.

By performing the two-step sintering under the above-described conditions, a more rigid sintered body can be obtained.

The step of preparing the nitrogen-substituted solid electrolyte powder may include mixing the solid electrolyte powder and the urea (mixing step); Crushing step; A first firing step; And a second firing step.

The mixing step may be performed by mixing the solid electrolyte powder and the urea in a weight ratio of 1 to 7: 4 to 6, specifically 3 to 6: 4.5 to 5.5. By mixing and pulverizing the solid electrolyte powder with the above-mentioned weight ratio, the part of oxygen of the solid electrolyte powder is substituted with nitrogen to form an optimum garnet structure, thereby obtaining a solid electrolyte having improved ion conductivity .

The pulverizing step may be a ball mill, a mortar, a sieve, an attrition mill, a disk mill, a jet mill, a jaw crusher, A crusher, or a combination thereof, and may be performed, for example, by a ball mill, a mortar, and / or a sieve.

The calcining step may be performed in a synthesis gas atmosphere in which N ₂ : H ₂ is contained in a volume ratio of 90:10 to 96: 4.

For example, the synthesis gas atmosphere may be N ₂ : H ₂ of 96: 4.

The first firing step of producing the nitrogen-substituted solid electrolyte powder may be performed at a temperature of 400 to 500 ° C for 2 to 6 hours and the second firing step may be performed at a temperature of 750 to 850 ° C for 3 to 6 hours have.

By performing firing in two steps under the above conditions, the effect of removing the remaining elements can be obtained.

The step of producing the nitrogen-substituted solid electrolyte powder with a pellet may include a compression step, a crushing step, and a firing step.

The compression step may be carried out with an intensity of 1 to 3 ton / cm ² , specifically 1.5 to 2.5 ton / cm ² . In the case of compressing with the above strength, the energy density per volume of the electrode is increased, and it is possible to manufacture a battery with a high energy density.

The firing step of producing the nitrogen-substituted solid electrolyte powder with pellets is performed at a temperature of 800 to 950 ° C for 3 to 6 hours, specifically, at a temperature of 870 to 930 ° C for 4 to 5 hours .

Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode and a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode, wherein the solid electrolyte layer comprises the solid electrolyte for a lithium secondary battery.

The solid electrolyte layer may have a thickness of 0.1 to 1 mm.

A lithium secondary battery according to an embodiment of the present invention will be described with reference to FIG.

1 is a schematic cross-sectional view showing an example of a lithium secondary battery of the present invention. The lithium secondary battery 10 in Fig. 1 includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a solid electrolyte layer 3 formed between the positive and negative electrodes, and a positive electrode active material layer 1, An anode current collector 4 to be carried out, an anode current collector 5 for collecting the anode active material layer 2, and a battery case 6 for housing these members.

The solid electrolyte layer 3 is as described above.

The positive electrode includes a current collector 4 and a positive electrode active material layer 1 formed on the current collector. The positive electrode active material layer 1 includes a positive electrode active material.

As the positive electrode active material is, for example, _{LiCoO 2, LiMnO 2, Li 2} NiMn 3 O 8, LiVO 2, LiCrO 2, LiFePO 4, LiCoPO 4, LiNiO 2, LiNi 1/3 Co 1/3 Mn 1/3 O ₂ , and the like.

The positive electrode active material layer may further contain a solid electrolyte material. By adding the solid electrolyte material, the Li ion conductivity of the positive electrode active material layer can be improved. Examples of the solid electrolyte material include an oxide solid electrolyte material and a sulfide solid electrolyte material. The thickness of the positive electrode active material layer is preferably within a range of, for example, 0.1 mu m to 1000 mu m, but is not limited thereto.

The negative electrode includes a current collector 5 and a negative electrode active material layer 2 formed on the current collector. The negative electrode active material layer includes a negative electrode active material and a binder, and optionally, a conductive material.

Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon.

The conductive material, the solid electrolyte material and the binder used for the negative electrode active material layer are the same as those in the above-described positive electrode active material layer. The thickness of the negative electrode active material layer is preferably within a range of, for example, 0.1 mu m to 1000 mu m, but is not limited thereto.

As the material of the positive electrode current collector 4, for example, SUS, aluminum, nickel, iron, titanium, carbon and the like are exemplified, and among them, SUS is preferable. On the other hand, as the material of the anode current collector 5, for example, SUS, copper, nickel, carbon and the like are exemplified, and among them, SUS is preferable. The thickness and the shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected depending on the use of the lithium battery or the like. A battery case of a general lithium battery can be used for the battery case 10 used in the present invention. Examples of the battery case include a battery case made of SUS.

The negative electrode and the positive electrode respectively prepare powders of an active material and powders of a solid electrolyte, and then prepare respective slurries of the solid electrolyte layer, the positive electrode active material layer and the negative electrode active material layer. Then, the respective slurries of the solid electrolyte layer, the positive electrode active material layer and the negative electrode active material layer are molded to produce a green sheet. Thereafter, the green sheets of the solid electrolyte layer, the positive electrode layer and the negative electrode layer are laminated to form a laminate. Subsequently, the laminate is fired. The positive electrode active material layer and the negative electrode active material layer are bonded to the solid electrolyte layer by firing. Finally, the fired laminate is sealed in, for example, a coin cell. The sealing method is not particularly limited. For example, the fired laminated body may be sealed with a resin. Alternatively, an insulating paste having an insulating property such as Al ₂ O ₃ may be applied or dipped around the laminate, and the insulating paste may be sealed by heat treatment.

In addition, a conductive layer such as a metal layer may be formed on the positive electrode and the negative electrode to efficiently draw current from the positive electrode and the negative electrode. The conductive layer may be formed by, for example, sputtering. The metal paste may be heat-treated by applying or dipping the metal paste.

The method of forming the green sheet is not particularly limited, but tape casting, die coater, comma coater, screen printing and the like can be used. The method of laminating the green sheet is not particularly limited, but a green sheet can be laminated by using hot isostatic press (HIP), cold isostatic press (CIP), hydrostatic press (WIP) or the like.

The slurry for forming the green sheet can be produced by wet mixing an organic vehicle in which a polymer material is dissolved in a solvent, a positive electrode active material powder, a negative electrode active material powder, a solid electrolyte powder, or a current collector material powder. As the wet mixing, a medium can be used. Specifically, a ball mill method, a visco mill method, or the like can be used. On the other hand, a wet mixing method that does not use media may be used, and a sand mill method, a high pressure homogenizer method, a kneader dispersion method, or the like can be used.

The slurry may include a plasticizer. The kind of plasticizer is not particularly limited, but phthalate esters such as dioctyl phthalate, diisononyl phthalate and the like may be used.

In the sintering step, the atmosphere is not particularly limited, but it is preferable to conduct the sintering under the condition that the valence of the transition metal contained in the electrode active material does not change. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

Hereinafter, specific examples of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

In addition, contents not described here can be inferred sufficiently technically if they are skilled in the art, and a description thereof will be omitted.

Example  One

(Synthesis of Solid Electrolyte Powder)

Powders were prepared by weighing Li ₂ CO ₃ (purity 4N), La ₂ O ₃ (purity 4N) and ZrO ₂ (purity 99%) at a molar ratio of 3.5: 1.5: 2, respectively. Prior to mixing the powders, La ₂ O ₃ was dried at 900 ° C. for 24 hours to remove any adsorbed moisture. Dried La ₂ O ₃ , Li ₂ CO ₃ and ZrO ₂ were mixed, and then charged into a Nalgen bottle charged with a ball mixed with zirconia balls 3 mm + 5 mm at a ratio of 1: 1, IPA (iso-propyl alcohol: isopropyl alcohol) was added and the ball mill was performed for 24 hours. At this time, a small amount of an ammonia dispersant (28% ammonia water) was added to improve mixing performance. After the ball mill and drying, it was fired in a sintering furnace at 900 ° C for 3 hours, and the heating rate was 2 ° C / min. After grinding in an agate mortar, it was classified by using a 100 μm mesh and then subjected to secondary firing at 1125 ° C. for 3 hours to prepare a final powder.

10 g of the solid electrolyte powder and 50 g (1: 5 weight ratio) of urea (Alfa Aesar) were mixed and ball milled for 24 hours to uniformly mix the solid electrolyte powder and the urea. This was dried, classified, and then primarily heat-treated at 500 ° C for 2 hours using a furnace in an atmosphere of a flowing synthetic gas (N ₂ : H ₂ = 96: 4). Most of the elements were found to evaporate at this time. The remaining elements were again subjected to a second heat treatment at 800 ° C. for 3 hours in a furnace in an atmosphere of a flowing synthetic gas (N ₂ : H ₂ = 96: 4), and they were pulverized and classified into 80 to 90 μm, One powder was taken. The prepared powders were changed from white to gray, so that it was indirectly confirmed that the solid electrolyte powder was chemically changed, that is, nitrogen was substituted.

(Production of solid electrolyte pellets)

The solid electrolyte powder was used to prepare pellets. 0.5 g of the powder was poured into a pellet under a mold having a width of 1 cm ² using a high-pressure press (pressure: 1 ton / cm ² ) and sintered. The sintering conditions were heat treatment at 900 캜 for 3 hours in a syngas (N ₂ : H ₂ = 96: 4) atmosphere.

FIG. 2 is a photograph of a nitrogen-substituted solid electrolyte pellet heat-treated at 900.degree.

Comparative Example  One

A solid electrolyte was prepared in the same manner as in Example 1, except that the nitrogen substitution was not performed using the urea method.

Evaluation 1: X-ray diffraction  ( XRD : X- ray diffraction ) Measure

X-ray diffraction (XRD) measurement was performed on the solid electrolyte material according to Example 1 and Comparative Example 1 using CuK? Ray, and the results are shown in FIG.

Referring to FIG. 3, the solid electrolyte according to Comparative Example 1 has a tetragonal structure from two split peaks near 30 ° and six split peaks near 50 °. It can be seen that it has.

On the other hand, in the solid electrolyte according to Example 1, the appearance of the peak appearing in the solid electrolyte according to Comparative Example 1 disappears, and a peak relating to lithium oxide and lithium nitride appears mainly. .

Evaluation 2: Measurement of ion conductivity

Au was sputtered at 300 nm on the upper and lower portions of the solid electrolyte pellet prepared in Example 1 to prepare an electrode, and the ion conductivity of Li was measured by the AC impedance method. The measurement was conducted under the conditions of an applied voltage of 5 mV at room temperature and an AC impedance of 7 MHz to 0.5 Hz in the measurement frequency range. The results are shown in FIG. 4.

In order to calculate the ion conductivity in consideration of the area and thickness of the Au electrode on the pellet, CNLS fitting was performed using the equivalent circuit of Fig.

Referring to FIG. 4, it can be seen that a semicircle appears distinctly when measured at room temperature. This means that the semiconductors in the high frequency (Hz) region have ion conductivity of Li ion due to the combination of the resistance and the capacitance term. Lt; RTI ID = 0.0 &gt; Hz) &lt; / RTI &gt; is known to be caused by diffusion.

Referring to FIG. 5, R _bulk denotes a grain boundary internal resistance, R _gb denotes a grain boundary resistance, and R _el denotes a metal resistance for conductivity measurement. As a result of calculating the ion conductivity by the sum of R _bulk and R _gb , Ion conductivity of 8 X 10 ^-5 S / cm can be confirmed. That is, the ion conductivity of the Garnet-type structure having the tetragonal structure is 10 times or more higher than that of the ion conductivity of 6 × 10 ^-6 S / cm.

Rating 3: XPS  Quantitative analysis

The results of XPS quantitative analysis of the solid electrolyte pellets prepared according to Example 1 are shown in Table 1 below.

XPS is an analytical method for confirming the chemical bonding state of the surface with a beam transmission range of several tens nm thick, and is effective for confirming whether N is substituted. In this analysis, we used 250 ESCA Model VG Scientific, Inc., using the ^{Li1s La3d 5, Zr3d, O1s,} N1s spectrum was analyzed for each element.

Referring to Table 1, the amount of Zr and La is relatively small, which means that the depth of the XPS analysis is several tens of nanometers, and the surface mainly contains oxygen and nitride. That is, it can be indirectly confirmed that the nitrogen substitution effect by the element is excellent.

peak center SF PK area FWHM Tx. Function Norm area [AT]% La 3d ⁵ 836.70 28.12 1603.535 1.011 6611.5 0.00018 0.134 O1s 534.10 2.93 29000.900 2.400 5471.0 0.02952 22.402 N 1s 400.80 1.80 13590.222 2.353 5101.8 0.02232 16.940 C 1s 287.14 1.00 17972.928 4.976 4829.4 0.05288 40.129 Zr 3d 183.50 7.04 488.658 1.732 4608.3 0.00020 0.155 Li 1s 57.30 0.06 519.197 1.266 4368.0 0.02667 20.241

As described above, according to the embodiment of the present invention, by replacing part of the oxygen of the solid electrolyte with nitrogen by using the element, it is possible to produce a solid electrolyte having an optimum garnet structure by a more easy method, A lithium secondary battery having a high ionic conductivity including a solid electrolyte can be produced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And it goes without saying that they are within the scope of the present invention.

1: positive electrode active material layer 2: negative electrode active material layer
3: solid electrolyte layer 4: positive electrode collector
5: cathode current collector 6: battery case
10: Lithium secondary battery
R _bulk : grain boundary internal resistance R _gb : grain boundary resistance
R _el : metal resistance
CPE _bulk : the capacitance inside the grain boundaries taking into account the phase angle.
CPE _gb : Capacitance of grain boundary considering phase angle
CPE _diff : capacitance in the diffusion region considering the phase angle

Claims (22)

1. A solid electrolyte for a lithium secondary battery represented by the following formula 1 and having an ion conductivity of 8.0 X 10 < ^-5 &gt; S / cm or more:
[Chemical Formula 1]
Li _{5 + x} (M ¹ ) ₃ (M ² ) ₂ O _{12 -y} N _y
In Formula 1,
M ¹ is selected from the group consisting of La, Sr, Ba, Ca, In, Mg, Y, Sc, Cr,
M ² is Zr, Nb, Ta, Sb, Sn, Hf, Bi, W, Se, Ga, Ge,
0 < x? 2, and 0.001 &lt; y &lt; The method according to claim 1,
Wherein M < ^{1 &gt;} is La,
M ² is Zr,
X is 2,
Y is 0.005 &lt; y &lt; 2
Solid electrolyte for lithium secondary battery. The method according to claim 1,
(1) is a solid electrolyte for a lithium secondary battery represented by the following formula (2): &lt; EMI ID =
(2)
Li ₇ La ₃ Zr ₂ O _{10 .8} N _{1 .2} delete Preparing a solid electrolyte powder from Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ ;
Preparing a solid electrolyte powder substituted with nitrogen from the solid electrolyte powder and the urea; And
And a pellet of the solid electrolyte powder substituted with nitrogen. The solid electrolyte for a lithium secondary battery according to claim 1,
Preparing the nitrogen-substituted solid electrolyte powder by mixing the solid electrolyte powder and the urea; Crushing step; A first firing step; And a second firing step.
(JP) METHOD FOR PRODUCING SOLID ELECTROLYTE FOR LITHIUM SECONDARY BATTERY. 6. The method of claim 5,
The step of producing the solid electrolyte powder comprises
Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (mixing step);
Crushing a mixture of Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ (pulverizing step);
A first firing step; And
Second firing step
Wherein the solid electrolyte is a lithium salt. The method according to claim 6,
Wherein the mixing step comprises mixing Li ₂ CO ₃ , La ₂ O ₃ , and ZrO ₂ in a molar ratio of 3.7 to 4.4: 1.4 to 1.6: 1.9 to 2.1, respectively, to the solid electrolyte for lithium secondary batteries. The method according to claim 6,
And drying the La ₂ O ₃ before the mixing step (drying step). 9. The method of claim 8,
Wherein the drying step is performed at 700 to 1000 ° C for 12 to 24 hours. The method according to claim 6,
Wherein the mixing step further comprises adding an ammonia dispersing agent to the solid electrolyte. The method according to claim 6,
Wherein the first baking step is performed at 850 to 950 캜 for 2 to 5 hours. The method according to claim 6,
Wherein the second baking step is performed at 1,100 to 1,250 ° C for 2 to 5 hours. delete 6. The method of claim 5,
Wherein mixing the solid electrolyte powder and the urea is performed by mixing the solid electrolyte powder and the urea at a weight ratio of 1: 7: 4 to 6: 1. The method according to claim 5 or 6,
The pulverizing step may be a ball mill, a mortar, a sieve, an attrition mill, a disk mill, a jet mill, a jaw crusher, , A crusher, or a combination thereof. 2. A method for producing a solid electrolyte for a lithium secondary battery, comprising the steps of: 6. The method of claim 5,
Wherein the first firing step is performed at a temperature of 400 to 500 ° C for 2 to 6 hours. 6. The method of claim 5,
Wherein the second baking step is performed at a temperature of 750 to 850 캜 for 3 to 6 hours. 6. The method of claim 5,
The step of producing the nitrogen-substituted solid electrolyte powder with a pellet
A compression step, a pulverization step, and a firing step. 19. The method of claim 18,
Wherein the compressing step is performed at a strength of 1 to 3 tons / cm &lt; ² &gt;. 20. The method of claim 19,
Wherein the sintering step is performed at a temperature of 800 to 950 캜 for 3 to 6 hours. Anode and cathode, and
And a solid electrolyte layer between the anode and the cathode,
Wherein the solid electrolyte layer comprises the solid electrolyte for a lithium secondary battery according to any one of claims 1 to 3. 22. The method of claim 21,
Wherein the solid electrolyte layer has a thickness of 0.1 to 1 mm.

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