KR20210150718A - Sodium halide-based solid electrolyte, preparation method thereof and all-solid battery comprising the same - Google Patents

Abstract

The present invention relates to a sodium halide-based solid electrolyte, a method for manufacturing the same, and an all-solid-state battery including the same. The sodium halide-based solid electrolyte according to the present invention has excellent atmospheric stability compared to an existing sulfide-based solid electrolyte, has good sodium ion conductivity, and has higher safety than a battery to which an organic liquid electrolyte is applied, thereby being usefully used for the all-solid-state battery.

Description

Sodium halide-based solid electrolyte, manufacturing method thereof, and all-solid battery comprising the same

The present invention relates to a secondary battery, and more particularly, to a solid electrolyte and an all-solid-state battery including the same.

Recently, the industrial field that requires lithium-ion secondary batteries is expanding from the power supply of small mobile devices to the power supply of mid- to large-sized electric vehicles (EVs, HEVs, etc.) and energy storage devices (ESS). In particular, interest in electric vehicles, which are eco-friendly vehicles, is very high, and major automakers around the world are accelerating technology development by recognizing electric vehicles as the next-generation growth technology under the motto of eco-friendliness. In the case of such a medium and large-sized lithium ion secondary battery, unlike the small size, the operating environment (eg, temperature, impact) is harsh, and since it includes many batteries, it is essential to secure safety. Accordingly, as the industrial field requiring a lithium ion secondary battery expands its application range to a large battery, interest in the safety issue of the lithium ion secondary battery is also greatly increased.

Existing lithium-ion secondary batteries have problems such as low thermal stability, ignitability, and leakage because they use an organic liquid electrolyte. In fact, as explosion accidents of products to which this is applied are continuously reported, it is urgent to solve these problems. Accordingly, as a solution, an all-solid-state battery using a solid electrolyte is emerging as an alternative. In order to express the performance of such an all-solid-state battery, it is required that the solid electrolyte and the active material, which are the basis thereof, have excellent contact characteristics between particles. Accordingly, the sulfide-based solid electrolyte (eg, composition of Li _x PS _y , Li _x M _y S _z, etc.) is an oxide-based solid electrolyte (eg, Li _x La _y TiO ₃ , Li ₇ La ₃ Zr ₂ O). ₁₂ ) Because it has better ductile properties, it is possible to induce close contact between the solid electrolyte and active material particles only by cold pressing due to the particle properties, so that an all-solid-state battery with excellent lithium ion conductivity can be obtained. There are advantages.

However, the sulfide-based solid electrolytes have a problem in that atmospheric stability is lower than that of the oxide-based solid electrolytes, so there is a great difficulty in the all-solid-state battery manufacturing process.

Korean Patent Publication No. 2018-0094184

An object of the present invention is to provide a solid electrolyte having good atmospheric stability and sodium ion conductivity.

In addition, another object to be solved by the present invention is to provide a method for preparing the solid electrolyte.

Furthermore, another problem to be solved by the present invention is to provide an all-solid-state battery including the solid electrolyte.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above technical object, one aspect of the present invention provides a sodium halide-based solid electrolyte comprising a compound represented by the following formula (1).

[Formula 1]

Na _a M1 _b M2 _c X ₆

(In Formula 1,

1≤a<4, 0<b≤1, 0≤c<1,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element.)

The sodium halide-based solid electrolyte may include a compound represented by the following formula (2).

[Formula 2]

Na _2+x M1 _1-c M2 _c X ₆

(In Formula 2,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element,

When M2 has an oxidation number of +2, x=2c, 0≤c<1, 0≤x<2,

When M2 has an oxidation number of +3, x=c, 0≤c<1, 0≤x<1.)

M1 is Ti, Zr and Hf.

wherein M2 is Y, Sc, Cr, Mn, Fe, Co, Ni, Al, Ga, As, Sb, Bi, Mg, Ca, Zn, Cd, Tb, Dy, Ho, Er, Tm and Yb from the group consisting of can be selected.

X may be F, Cl or Br.

M1 may be Zr, and X may be Cl or Br.

M1 is Zr, M2 is Y, X is Cl or Br, and the range of c may be 0.5 or more and 0.9 or less.

M1 is Zr, M2 is Fe, X is Cl or Br, and the range of c may be 0.1 or more and 0.5 or less.

The sodium halide-based solid electrolyte may have a glass-ceramic structure.

In addition, another aspect of the present invention provides a method for preparing the sodium halide-based solid electrolyte. The method for preparing the sodium halide-based solid electrolyte may include preparing a solid electrolyte including the compound of Formula 1a by reacting a sodium (Na) halide and an M1 metal halide as a precursor.

[Formula 1a]

Na _a M1 _b X ₆

(In Formula 1a,

a=2, b=1,

M1 is a transition metal element having an oxidation number of +4,

X is a halogen element,

Formula 1a is included in Formula 1.)

In addition, the method for preparing the sodium halide-based solid electrolyte may include preparing a solid electrolyte comprising the compound of Formula 1b by reacting sodium (Na) halide, M1 metal halide, and M2 metal halide as a precursor. can

[Formula 1b]

Na _a M1 _b M2 _c X ₆

(In Formula 1b,

1≤a<4, 0<b<1, 0<c<1,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element

Formula 1b is included in Formula 1.)

The reaction may be carried out by solid-phase mixing.

The solid-phase mixing may be mechanical milling selected from the group consisting of a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill.

The mechanical milling may be performed at a rotational speed in the range of 400 rpm to 700 rpm.

The reaction may be carried out in an organic solvent.

Furthermore, another aspect of the present invention provides an all-solid-state battery. The all-solid-state battery includes a positive electrode layer; cathode layer; and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer includes a sodium halide-based solid electrolyte containing the compound of Formula 1 can do.

[Formula 1]

Na _a M1 _b M2 _c X ₆

(In Formula 1,

1≤a<4, 0<b≤1, 0≤c<1,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element.)

The sodium halide-based solid electrolyte according to the present invention has excellent atmospheric stability compared to the existing sulfide-based solid electrolyte, has good sodium ion conductivity, and has higher safety than a battery to which an organic liquid electrolyte is applied, so it can be usefully used in an all-solid-state battery have.

1 is a schematic diagram of an all-solid-state battery according to an embodiment of the present invention.
2 is an X-ray diffraction analysis (XRD) spectrum of reactants and products when a sodium halide-based solid electrolyte is prepared according to Preparation Example of the present invention.
3 is an X-ray diffraction analysis (XRD) spectrum of a solid electrolyte prepared according to a Preparation Example or Comparative Example of the present invention.
4 is a voltage-capacity graph of an initial charge/discharge cycle of an all-solid-state battery including a sodium halide-based solid electrolyte according to a preparation example of the present invention.
5 is a graph showing rate-rate characteristic evaluation according to cycles of an all-solid-state battery including a sodium halide-based solid electrolyte according to a preparation example of the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Sodium halide solid electrolyte

The present invention provides a sodium halide-based solid electrolyte comprising a compound represented by the following formula (1).

[Formula 1]

Na _a M1 _b M2 _c X ₆

(In Formula 1,

1≤a<4, 0<b≤1, 0≤c<1,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element.)

In addition, the sodium halide-based solid electrolyte may include a compound represented by the following formula (2).

[Formula 2]

Na _2+x M1 _1-c M2 _c X ₆

(In Formula 2,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element,

When M2 has an oxidation number of +2, x=2c, 0≤c<1, 0≤x<2,

When M2 has an oxidation number of +3, x=c, 0≤c<1, 0≤x<1.)

Specifically, M1 is Ti, Zr and Hf,

M2 is selected from the group consisting of Y, Sc, Cr, Mn, Fe, Co, Ni, Al, Ga, As, Sb, Bi, Mg, Ca, Zn, Cd, Tb, Dy, Ho, Er, Tm and Yb becomes,

X may be F, Cl or Br.

More specifically, M1 may be Zr, and X may be Cl or Br.

The sodium halide-based solid electrolyte according to the present invention is characterized in that it contains sodium, a transition metal having an oxidation number of +4 as M1, and a halogen element.

In the solid electrolyte according to the present invention, M1 includes a transition metal having an oxidation number of +4. The transition metal having an oxidation number of +4 is a metal having an oxidation number of +3, which has been used as a material for a solid electrolyte in the past. , for example, compared with In and Y, etc., the reserves are abundant, so it is easy to obtain and the unit price is low. Therefore, the solid electrolyte according to the present invention is manufactured by using a transition metal having an oxidation number of +4, which has abundant reserves and is inexpensive in unit price. Reduced mass production is possible. In addition, M1 alone shows the same conductivity as a metal having an oxidation number of +3, and when used together with a metal M2 having an oxidation number of +2 or +3, the conductivity is remarkably improved by more than twice, so it is suitable for a sodium battery. It can be used as a useful solid electrolyte material.

In the solid electrolyte according to the present invention, since the halogen element improves atmospheric stability as well as ion conduction, the solid electrolyte according to the present invention containing the halogen element may have superior atmospheric stability compared to the conventional sulfide-based solid electrolyte. .

In the halide-based solid electrolyte according to the present invention, the compound of Formula 1 exhibits a crystalline phase through X-ray diffraction analysis (XRD), and may have a glass-ceramic crystal structure.

The halide-based solid electrolyte according to the present invention can be formed in a composition of various molar ratios by adjusting the range of c according to the types of M1 and M2.

As an example, in Formula 2, when M1 is Zr and M2 is a metal having an oxidation number of +3, for example, Y, Fe, etc., the range of c is 0.1 or more and 0.9 or less, more specifically, the range of c is It may be 0.2 or more and 0.8 or less.

As an example, in Formula 2, when M1 is Zr and M2 is Y, the range of c may be 0.5 or more and 0.9 or less, and specifically, 0.6 or more and 0.8 or less.

As an example, in Formula 2, when M1 is Zr and M2 is Fe, the range of c may be 0.1 or more and 0.5 or less, and specifically, 0.2 or more and 0.4 or less.

Method for producing sodium halide-based solid electrolyte

In addition, the present invention provides a method for preparing the sodium halide-based solid electrolyte.

The solid electrolyte may be prepared by a dry or wet method, but is not limited thereto.

The method for preparing a sodium halide-based solid electrolyte according to an aspect of the present invention is

and reacting a sodium (Na) halide and an M1 metal halide as a precursor to prepare a solid electrolyte including the compound of Formula 1a below.

[Formula 1a]

Na _a M1 _b X ₆

(In Formula 1a,

a=2, b=1,

M1 is a transition metal element having an oxidation number of +4,

X is a halogen element,

Formula 1a is included in Formula 1.)

In addition, the method for producing a sodium halide-based solid electrolyte according to another aspect of the present invention is

and reacting sodium (Na) halide, M1 metal halide, and M2 metal halide as a precursor to prepare a solid electrolyte including the compound of Formula 1b below.

[Formula 1b]

Na _a M1 _b M2 _c X ₆

(In Formula 1b,

1≤a<4, 0<b<1, 0<c<1,

M1 is a transition metal element having an oxidation number of +4,

M2 is a metal element having an oxidation number of +2 or +3,

X is a halogen element,

Formula 1b is included in Formula 1.)

As the sodium halide, for example, NaCl or NaBr may be used, and as the M1 metal halide, for example, ZrCl ₄ , ZrBr ₄ and the like may be used. As the M2 metal halide, for example, YCl ₃ , FeCl ₃ and the like may be used.

In addition, the composition of the precursor is not particularly limited as long as it can finally obtain a desired halide-based solid electrolyte.

For example, _{when preparing Na 2} ZrCl _{6 , NaCl and ZrCl 4} may be used as the composition of the precursor, and when preparing _{Na 2.7} Zr _0.3 Y _0.7 Cl ₆ , the composition of the precursor includes NaCl, ZrCl ₄ and YCl ₃ may be used.

The reaction may be carried out by solid-phase mixing as a dry method.

As the solid-phase mixing, for example, mechanical milling may be used.

The mechanical milling is a method of pulverizing a sample while applying mechanical energy. Examples of such mechanical milling include a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill, and among them, a ball mill is preferable.

Various conditions of the mechanical milling may be set to obtain a desired solid electrolyte. For example, in the case of using a ball mill, the precursors and the grinding balls are added, and processing is performed at a predetermined number of revolutions and time. In general, the higher the number of revolutions, the faster the production rate of the solid electrolyte alloy, and the longer the processing time, the higher the conversion rate from the precursors to the solid electrolyte. The rotational speed when performing the ball mill is preferably performed at a high speed in the range of, for example, 400 rpm to 700 rpm. Moreover, it is preferable that the processing time at the time of performing a ball mill exists in the range of 1 hour - 100 hours, especially within the range of 1 hour - 70 hours, for example.

In addition, the solid electrolyte including the compound of Formula 1 prepared through the solid-phase mixing may be additionally heat-treated.

The heat treatment may be performed in a temperature range of greater than 100 °C and less than or equal to 600 °C. In general, since metals such as yttrium (Y) and zirconium (Zr) are crystallized at 100°C or higher, if the heat treatment temperature is 100°C or lower, the heat treatment effect of the solid electrolyte is insignificant, and when it exceeds 600°C, solid There is a problem in that the elements constituting the electrolyte are vaporized and the solid electrolyte is lost.

In addition, the reaction may be carried out in an organic solvent through a wet method, specifically

forming a solid electrolyte including the compound of Formula 1 by adding sodium (Na) halide and M1 metal halide as precursors to an organic solvent and reacting;

evaporating the organic solvent from the formed solid electrolyte solution to obtain a dried solid electrolyte; and

It may be carried out by a method comprising the step of heat-treating the dried solid electrolyte.

In addition, M2 metal halide may be further added as the precursor.

The wet method is a method known in the organic chemistry field in the art, and a detailed description thereof will be omitted.

All-solid-state battery containing sodium halide-based solid electrolyte

In addition, the present invention provides an all-solid-state battery comprising the sodium halide-based solid electrolyte.

1 is a schematic diagram of an all-solid-state battery according to an embodiment of the present invention.

Referring to FIG. 1 , an all-solid-state battery 100 according to the present invention includes a positive electrode layer 10 , a negative electrode layer 30 , and a solid electrolyte layer 50 .

At this time, at least one of the positive electrode layer 10, the negative electrode layer 30, and the solid electrolyte layer 50 is characterized in that it contains the sodium halide-based solid electrolyte.

anode layer

The positive electrode layer 10 is a layer containing a positive electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder, if necessary. At this time, the positive electrode layer 10 contains a solid electrolyte, and the solid electrolyte is preferably a sodium halide-based solid electrolyte according to the present invention.

The proportion of the sodium halide-based solid electrolyte contained in the positive electrode layer 10 varies depending on the type of battery, but is, for example, within the range of 0.1% by volume to 80% by volume, especially 1% by volume to 60% by volume It is preferred to be within the range, in particular from 10% by volume to 50% by volume.

The positive active material may be a metal oxide including sodium into which sodium ions can be inserted or desorbed electrochemically by redox reaction. For example, the positive electrode active material is NaCoO ₂ sodium-cobalt composite oxide, NaNiO ₂ such as sodium, nickel composite oxide, NaMn ₂ O _4, such as sodium, manganese-based composite oxide, NaV ₂ O _5, such as sodium of the - A sodium-iron complex oxide such as a vanadium-based complex oxide or NaFeO _{2 can be used.} In addition, the positive active material may be an NCM material. That is, the positive active material may be NaNi _x Co _y Mn _z O ₂ (x+y+z=1) , NaNi _x Co _y Mn _z M _a O ₂ (x+y+z+a=1), where M is B, Al, Ga, In, Si, Ge, Sn, Pb, As, Sb, Bi, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, It may be Ru, Rh, Pd, Ag, Hf, Ta, or W, or the like.

The conductive material is not particularly limited as long as it is a conductive material used in batteries, but graphene, carbon nanotubes, Ketjen black, activated carbon, powder form Super p carbon, rod form Denka, or vapor grown carbon fiber (VGCF) It is preferable to use

As the binder, it is generally preferable to use a high molecular compound of a fluorine-based, diene-based, acryl-based, or silicone-based polymer. For example, the binder may be nitrile butadiene rubber (NBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyimide, etc. can

The positive electrode layer 10 may be prepared by applying a first slurry formed by mixing at least one of a positive electrode active material, a sodium halide-based solid electrolyte according to the present invention, a solvent, a solid electrolyte if necessary, a conductive material, and a binder. can

The thickness of the anode layer 10 is, for example, preferably in the range of 0.1 μm to 1000 μm.

cathode layer

The negative electrode layer 30 is a layer containing an anode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder, if necessary. In this case, the negative electrode layer 20 contains a solid electrolyte, and the solid electrolyte is preferably a sodium halide-based solid electrolyte according to the present invention.

The proportion of the sodium halide-based solid electrolyte contained in the negative electrode layer 30 varies depending on the type of battery, but is, for example, within the range of 0.1% by volume to 80% by volume, especially 1% by volume to 60% by volume It is preferred to be within the range, in particular from 10% by volume to 50% by volume.

Here, the negative electrode layer 30 is manufactured through the same composition and manufacturing method as the positive electrode layer 10 except for the negative electrode active material. Therefore, the same description is not repeated.

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

The negative electrode layer 30 is a negative electrode active material, a sodium halide-based solid electrolyte according to the present invention, a solvent, and if necessary, a second slurry formed by mixing at least one of a solid electrolyte, a conductive material, and a binder to be prepared through a coating process. can

The thickness of the negative electrode layer 30 is, for example, preferably in the range of 0.1 μm to 1000 μm.

solid electrolyte layer

The solid electrolyte layer 50 is a layer formed between the positive electrode layer 10 and the negative electrode layer 30, and preferably contains the sodium halide-based solid electrolyte according to the present invention.

The ratio of the sodium halide-based solid electrolyte contained in the solid electrolyte layer 50 is, for example, in the range of 10% by volume to 100% by volume, and more preferably in the range of 50% by volume to 100% by volume. In addition, the solid electrolyte layer 50 may be composed of only the sodium halide-based solid electrolyte.

The thickness of the solid electrolyte layer 50 is, for example, preferably in the range of 0.1 μm to 1000 μm, and particularly preferably in the range of 0.1 μm to 300 μm. In addition, as a method of forming the solid electrolyte layer, for example, a method of compression molding the sodium halide-based solid electrolyte or a method of applying a third slurry formed by mixing the sodium halide-based solid electrolyte with a binder and a solvent, etc. can

other configuration

In general, the all-solid-state battery may further include a positive electrode current collector for collecting current in the positive electrode layer, and a negative electrode current collector for collecting current in the negative electrode layer.

Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium and carbon, and among these, SUS is preferable.

On the other hand, as the material of the negative electrode current collector, for example, SUS, copper, nickel, carbon and the like can be mentioned, and SUS is preferable among them.

The thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the battery and the like.

In addition, the all-solid-state battery may further include a battery case for accommodating it.

As the battery case, a battery case of a general battery can be used, and examples thereof include a battery case made of SUS.

The all-solid-state battery according to the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. As a shape of the battery of this invention, a coin shape, a laminate type, cylindrical shape, a square shape, etc. are mentioned, for example. In addition, the manufacturing method of the battery of this invention will not be specifically limited if it is a method which can obtain the above-mentioned battery, The method similar to the manufacturing method of a general battery can be used. For example, a method of sequentially pressing the material constituting the positive electrode layer, the material constituting the solid electrolyte layer, and the material constituting the negative electrode layer, then storing it inside the battery case and caulking the battery case, etc. have.

Hereinafter, preferred preparation examples and experimental examples are presented to help the understanding of the present invention. However, the following preparation examples and experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following preparation examples.

Preparation of solid electrolyte: Preparation Examples 1 to 4

<Preparation Example 1: Preparation of Na ₂ ZrCl ₆ >

As a precursor, 0.6660 mol of NaCl and 0.3330 mol of ZrCl ₄ were ball milled at 500 rpm to prepare _{Na 2} ZrCl _{6 .}

The results of X-ray diffraction analysis (XRD) of the precursors as reactants and the product after ball milling are shown in FIG. 2 .

2 is an XRD spectrum of a reactant and a product according to Preparation Example 1 of the present invention.

As shown in FIG. 2 , in the XRD spectrum of the product, the peak of the reactant disappeared and a new peak appeared, confirming that precursors as reactants were successfully synthesized into an alloy.

<Preparation Example 2: Preparation of Na _2.7 Zr _0.3 Y _0.7 Cl ₆ >

As a precursor, NaCl 0.4330 mol, YCl ₃ 0.3751 mol, and ZrCl ₄ 0.1919 mol were ball milled at 500 rpm to prepare _{Na 2.7} Zr _0.3 Y _0.7 Cl _{6 .}

<Preparation Example 3: Preparation of Na _2.25 Zr _0.75 Fe _0.25 Cl ₆ >

As a precursor, NaCl 0.3791 mol, FeCl ₃ 0.1169 mol, and ZrCl ₄ 0.5039 mol were ball milled at 500 rpm to prepare _{Na 2.25} Zr _0.75 Fe _0.25 Cl _{6 .}

<Preparation Example 4: Preparation of Na ₂ ZrBr ₆ >

As precursors, 0.6663 mol of NaBr and 0.3337 mol of ZrBr ₄ were ball milled at 500 rpm to prepare _{Na 2} ZrBr _{6 .}

<Analysis>

(1) X-ray diffraction measurement

X-ray diffraction analysis (XRD) was performed on the solid electrolytes prepared in Preparation Examples 1 to 4, and the results are shown in FIG. 3 .

3 is an XRD spectrum of the solid electrolyte prepared in Preparation Examples 1 to 4 above.

As shown in FIG. 3 , it was confirmed that the solid electrolyte was successfully synthesized by ball milling through the spectrum of the solid electrolyte.

(2) Measurement of Na ion conductivity

Na ion conductivity was measured at 30° C. for the solid electrolytes prepared in Preparation Examples 1 to 4.

First, in a glove box in an argon atmosphere, an appropriate amount of the sample is weighed, put into a polyethylene terephthalate tube (PET tube, inner diameter 10 mm, outer diameter 30 mm, height 20 mm), and from top to bottom, a powder containing carbon tool steel S45C anvil sandwiched between forming jigs. Next, using a uniaxial press machine (P-6 manufactured by Rikken Seiki Co., Ltd.), it was pressed at a display pressure of 6 MPa (molding pressure of about 110 MPa), and pellets having a diameter of 10 mm and an arbitrary thickness were molded. Next, on both sides of the pellet, 13 mg to 15 mg of gold powder (manufactured by Nilaco, water phase, particle size of about 10 μm) was added in increments of 13 mg to 15 mg, uniformly dispersed on the surface of the pellet, and displayed at a pressure of 30 MPa (forming pressure of about 560 MPa). ) was molded. Thereafter, the obtained pellets were placed in a closed electrochemical cell capable of maintaining an argon atmosphere.

For the measurement, an impedance/gain phase analyzer (solartron 1260) manufactured by Solartron Corporation is used as a frequency response analyzer FRA (Frequency Response Analyzer), and a small environmental tester (Espec corp, SU-241, -40°C to -40°C) is used as a constant temperature device. 150°C) was used. Measurement was started from the high frequency region under the conditions of an alternating voltage of 10 mV to 1000 mV, a frequency range of 1 Hz to 10 MHz, an integration time of 0.2 second, and a temperature of 30°C. Zplot was used for the measurement software, and Zview was used for the analysis software. The obtained results are shown in Table 1.

Solid electrolyte composition Na ion conductivity (mS/cm) Preparation Example 1 Na ₂ ZrCl ₆ 0.002 Preparation 2 Na _{2 . 7} Zr _{0 . 3} Y _{0 . 7} Cl ₆ 0.0013 Preparation 3 Na _2.25 Zr _0.75 Fe _0.25 Cl ₆ 0.0024 Preparation 4 Na ₂ ZrBr ₆ 0.000039

As shown in Table 1, the prepared halide materials can be usefully used as electrolytes because they exhibit ionic conductivity.

Preparation of all-solid-state battery: Preparation Examples 5 to 8

<Preparation Example 5: Preparation of all-solid-state battery>

The anode layer was prepared by applying a coating process. _{Specifically, NaCoO 2} was used as the cathode active material, and the sodium halide-based solid electrolyte prepared in Preparation Example 1 was used as the solid electrolyte. Super-C was used as a conductive material.

A positive electrode layer was prepared by mixing positive active material: solid electrolyte: conductive material = 70:30:3 (parts by weight).

An all-solid-state battery was prepared using the prepared positive electrode layer, the solid electrolyte layer including the sodium halide-based solid electrolyte prepared in Preparation Example 1, and Na-Sn as the negative electrode, using an internally manufactured pressure cell.

<Preparation Examples 6 to 8>

An all-solid-state battery was prepared in the same manner as in Preparation Example 5, except that the sodium halide-based solid electrolyte prepared in Preparation Examples 2 to 4 was used as the solid electrolyte.

<Experimental example: battery charge/discharge characteristics>

Charge-discharge characteristics were evaluated using the all-solid-state battery prepared according to Example 5.

The battery was charged with a constant current of 0.112 mA up to 3.6 V compared to Na-Sn, and the battery was discharged with a constant current of -0.112 mA up to 2.0 V.

Rate-rate characteristic evaluation was performed by calculating the charging and discharging rates based on the charging and discharging capacities at 0.1C before performing the rate-rate characteristic evaluation.

As a result of the charging/discharging characteristic experiment, the initial charging/discharging characteristics were measured and shown in FIG. 4 , and rate characteristics according to the charging/discharging cycle were measured and shown in FIG. 5 .

4 is a voltage-capacity graph of an initial charge/discharge cycle of an all-solid-state battery including the sodium halide-based solid electrolyte prepared in Preparation Example 5 of the present invention.

As shown in FIG. 4 , it was confirmed that the all-solid-state battery including the sodium halide-based solid electrolyte according to the present invention exhibited a high capacity with an initial discharge capacity of about 112 mAh/g.

5 is a graph showing the rate-rate characteristic evaluation according to the cycle of the all-solid-state battery including the sodium halide-based solid electrolyte prepared in Preparation Example 5 of the present invention.

As shown in FIG. 5 , the all-solid-state battery including the sodium halide-based solid electrolyte according to the present invention exhibited excellent rate-rate characteristics for maintaining high capacity even when the number of charge/discharge cycles increased.

Therefore, the sodium halide-based solid electrolyte according to the present invention has superior atmospheric stability compared to the existing sulfide-based solid electrolyte, has good sodium ion conductivity, and has higher safety than a battery to which an organic liquid electrolyte is applied. Since the included all-solid-state battery exhibits excellent charge/discharge characteristics, it can be usefully used instead of the conventional all-solid-state battery.

On the other hand, the embodiments of the present invention disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

100: all-solid-state battery
10: anode layer
30: cathode layer
50: solid electrolyte layer

Claims (16)

A sodium halide-based solid electrolyte comprising a compound represented by the following formula (1).
[Formula 1]
Na _a M1 _b M2 _c X ₆
(In Formula 1,
1≤a<4, 0<b≤1, 0≤c<1,
M1 is a transition metal element having an oxidation number of +4,
M2 is a metal element having an oxidation number of +2 or +3,
X is a halogen element.) According to claim 1,
The sodium halide-based solid electrolyte is a sodium halide-based solid electrolyte comprising a compound represented by the following formula (2).
[Formula 2]
Na _2+x M1 _1-c M2 _c X ₆
(In Formula 2,
M1 is a transition metal element having an oxidation number of +4,
M2 is a metal element having an oxidation number of +2 or +3,
X is a halogen element,
When M2 has an oxidation number of +2, x=2c, 0≤c<1, 0≤x<2,
When M2 has an oxidation number of +3, x=c, 0≤c<1, 0≤x<1.) According to claim 1,
M1 is Ti, Zr And sodium halide-based solid electrolyte, characterized in that selected from the group consisting of Hf. According to claim 1,
wherein M2 is Y, Sc, Cr, Mn, Fe, Co, Ni, Al, Ga, As, Sb, Bi, Mg, Ca, Zn, Cd, Tb, Dy, Ho, Er, Tm and Yb from the group consisting of Sodium halide-based solid electrolyte, characterized in that selected. According to claim 1,
Wherein X is a sodium halide-based solid electrolyte, characterized in that F, Cl or Br. According to claim 1,
Wherein M1 is Zr,
Wherein X is a sodium halide-based solid electrolyte, characterized in that Cl or Br. 3. The method of claim 2,
wherein M1 is Zr, M2 is Y, X is Cl or Br, and the range of c is 0.5 or more and 0.9 or less. 3. The method of claim 2,
wherein M1 is Zr, M2 is Fe, X is Cl or Br, and the range of c is 0.1 or more and 0.5 or less. According to claim 1,
The sodium halide-based solid electrolyte is a sodium halide-based solid electrolyte, characterized in that it has a glass-ceramic (glass-ceramic) structure. A method for preparing a sodium halide-based solid electrolyte, comprising the step of reacting a sodium (Na) halide and an M1 metal halide as a precursor to prepare a solid electrolyte comprising the compound of Formula 1a.
[Formula 1a]
Na _a M1 _b X ₆
(In Formula 1a,
a=2, b=1,
M1 is a transition metal element having an oxidation number of +4,
X is a halogen element,
Formula 1a is included in Formula 1.) A method for preparing a sodium halide-based solid electrolyte, comprising the step of reacting a sodium (Na) halide, an M1 metal halide, and an M2 metal halide as a precursor to prepare a solid electrolyte comprising the compound of Formula 1b.
[Formula 1b]
Na _a M1 _b M2 _c X ₆
(In Formula 1b,
1≤a<4, 0<b<1, 0<c<1,
M1 is a transition metal element having an oxidation number of +4,
M2 is a metal element having an oxidation number of +2 or +3,
X is a halogen element
Formula 1b is included in Formula 1.) 12. The method of claim 10 or 11,
The reaction is a method for producing a sodium halide-based solid electrolyte, characterized in that carried out by solid-phase mixing. 13. The method of claim 12,
The solid-phase mixing is a method for producing a sodium halide-based solid electrolyte, characterized in that mechanical milling selected from the group consisting of a ball mill, a vibration mill, a turbo mill, a mechanofusion and a disk mill. 14. The method of claim 13,
The method for producing a sodium halide-based solid electrolyte, characterized in that the mechanical milling is performed at a rotation speed in the range of 400 rpm to 700 rpm. 12. The method of claim 10 or 11,
The method for producing a sodium halide-based solid electrolyte, characterized in that the reaction is carried out in an organic solvent. anode layer;
cathode layer; and
An all-solid-state battery including a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer,
At least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer includes a sodium halide-based solid electrolyte containing a compound of Formula 1 below, an all-solid-state battery.
[Formula 1]
Na _a M1 _b M2 _c X ₆
(In Formula 1,
1≤a<4, 0<b≤1, 0≤c<1,
M1 is a transition metal element having an oxidation number of +4,
M2 is a metal element having an oxidation number of +2 or +3,
X is a halogen element.)

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