KR20230060607A - Chloride-based solid electrolyte, all-solid batteries and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a chloride-based solid electrolyte, an all-solid battery, and a manufacturing method thereof capable of improving thermal stability and a side reaction with a cathode material. The present invention can provide the chloride-based solid electrolyte represented by the following chemical formula. By replacing some of chlorine ions (Cl^-) with oxygen ions (O^2-), the chloride-based solid electrolyte according to the present invention provides thermal and chemical stability while providing a stable structure and maintaining ion conductivity at a high temperature above 100 ℃ unlike a conventional chloride-based solid electrolyte. The chemical formula is Li_3+aMCl_6-bO_c, wherein M is at least one among Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and Ce (-0.5 < a+b-2c < 0.5, 0 < c <= 0.3).

Description

Chloride-based solid electrolyte, all-solid-state battery and manufacturing method thereof {Chloride-based solid electrolyte, all-solid batteries and manufacturing method thereof}

The present invention relates to an all-solid-state battery, and more particularly, to a chloride-based solid electrolyte with improved thermal stability and side reaction with a cathode material, an all-solid-state battery, and a manufacturing method thereof.

As the demand for electric vehicles and large-capacity power storage devices increases, various batteries have been developed to meet them.

Lithium secondary batteries have been widely commercialized because they have the best energy density and output characteristics among various secondary batteries. As a lithium secondary battery, a lithium secondary battery (hereinafter referred to as a 'liquid type secondary battery') including a liquid-type electrolyte containing an organic solvent is mainly used.

However, in the liquid type secondary battery, the liquid electrolyte is decomposed by an electrode reaction, causing expansion of the battery, and the risk of ignition due to leakage of the liquid electrolyte has been pointed out. In order to solve the problems of such a liquid-type secondary battery, a lithium secondary battery (hereinafter referred to as 'all-solid-state battery') to which a solid electrolyte having excellent stability is applied is attracting attention.

Solid electrolytes can be divided into sulfide-based, oxide-based and chloride-based. Since sulfide-based solid electrolytes have higher lithium ion conductivity than oxide-based solid electrolytes and are stable in a wide voltage range, sulfide-based solid electrolytes are mainly used as solid electrolytes for all-solid-state batteries.

However, since the sulfide-based solid electrolyte has relatively lower chemical stability than the oxide-based solid electrolyte, the operation of the all-solid-state battery is not stable. That is, sulfide-based solid electrolytes easily react with moisture in the atmosphere or moisture introduced in the process due to various factors such as residual L ₂ S or P ₂ S ₇ crosslinking sulfur contained in the structure, and when reacting with moisture, hydrogen sulfide (H ₂ S) Because there is a possibility that gas may be generated, it is handled in an environment such as a glove box with an argon gas atmosphere or a dry room where moisture is removed. Sulfide-based solid electrolytes have high reactivity with moisture and have problems in the manufacturing process, such as deterioration in ionic conductivity due to the generation of hydrogen sulfide gas.

Since chloride-based solid electrolytes use chloride ions (Cl ^- ), they provide improved high voltage stability compared to sulfide-based solid electrolytes. For this reason, studies on chloride-based solid electrolytes have recently been actively conducted.

However, glass-based chloride-based solid electrolytes have a problem in that ionic conductivity decreases because crystallization easily occurs even at a relatively low temperature of 100° C. or less due to the characteristics of the anion employed. In addition, since the chloride-based solid electrolyte causes a side reaction with a general cathode material at a low temperature, it suffers from poor thermal and chemical stability.

Publication No. 2019-0079135 (2019.07.05.)

Accordingly, an object of the present invention is to provide a chloride-based solid electrolyte, an all-solid-state battery, and a method for manufacturing the same, which are structurally stable even at a high temperature of 100° C. or higher and provide thermal and chemical stability while maintaining ionic conductivity.

Another object of the present invention is to provide a chloride-based solid electrolyte, an all-solid-state battery, and a manufacturing method thereof capable of solving the problem of decreasing ionic conductivity due to crystallization at a temperature of 100 ° C or less.

Another object of the present invention is to provide a chloride-based solid electrolyte, an all-solid-state battery, and a manufacturing method thereof, which provide thermal and chemical stability by suppressing side reactions with cathode materials.

In order to achieve the above object, the present invention provides a chloride-based solid electrolyte represented by the following chemical formula.

[chemical formula]

Li _3+a MCl _6-b O _c

(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and at least one of Ce, -0.5<a+b-2c<0.5, 0<c ≤0.3)

The M may be Y.

The b and the c may be the same.

The present invention also provides a method for producing a chloride-based solid electrolyte represented by the above chemical formula prepared by ball milling LiCl, Li ₂ O, and a metal (M) chloride.

The metal chloride may include YCl ₃ .

And the present invention provides an all-solid-state battery including a chloride-based solid electrolyte represented by the above chemical formula.

The all-solid-state battery includes a solid electrolyte membrane, an anode, a cathode, and a separator.

The chloride-based solid electrolyte is included in at least one of the solid electrolyte membrane, the anode, the cathode, and the separator.

A plurality of species having different compositions may be used as the chloride-based solid electrolyte included in at least one of the solid electrolyte membrane, the anode, the cathode, and the separator.

The chloride-based solid electrolyte may be prepared by synthesizing LiCl, Li ₂ O, and a metal (M) chloride by ball milling.

In addition, the all-solid-state battery according to the present invention may further include a chloride-based solid electrolyte represented by Li ₃ MCl ₆ .

Unlike conventional chloride-based solid electrolytes, the chloride-based solid electrolyte according to the present invention replaces some of the chlorine ions (Cl ^- ) with oxygen ions (O ^2- ), thereby maintaining ion conductivity by being structurally stable even at high temperatures of 100 ° C or higher. while providing thermal and chemical stability.

Since the chloride-based solid electrolyte according to the present invention does not crystallize even at 100° C., it is possible to solve the problem of decrease in ionic conductivity due to crystallization of the chloride-based solid electrolyte.

Since the chloride-based solid electrolyte according to the present invention can suppress side reactions with the cathode material, it provides improved thermal and chemical stability. As a result, the all-solid-state battery employing the chloride-based solid electrolyte according to the present invention can operate at high temperatures.

1 is a flow chart according to a method for preparing a chloride-based solid electrolyte according to the present invention.
2 is a graph showing the results of X-ray diffraction analysis of chloride-based solid electrolytes according to Examples and Comparative Examples.
3 is a graph showing results of X-ray diffraction analysis after heat treatment at 100° C. of chloride-based solid electrolytes according to Examples and Comparative Examples.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in this specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventors have appropriately used the concept of terms to describe their inventions in the best way. It should be interpreted as a meaning and concept consistent with the technical spirit of the present invention based on the principle that it can be defined in the following way. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can replace them at the time of the present application. It should be understood that there may be variations and variations.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

1 is a flow chart according to a method for preparing a chloride-based solid electrolyte according to the present invention.

Referring to FIG. 1, the method for preparing a chloride-based solid electrolyte according to the present invention includes preparing LiCl, Li ₂ O and metal (M) chloride (S10), LiCl, Li ₂ O and metal (M) chloride. and ball milling to prepare a chloride-based solid electrolyte represented by Chemical Formula 1 below (S20).

[Formula 1]

Li _3+a MCl _6-b O _c

(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and at least one of Ce, -0.5<a+b-2c<0.5, 0<c ≤0.3)

Here, all steps according to the method for preparing a chloride-based solid electrolyte according to the present invention are performed in a glove box or dry room or in an inert gas atmosphere so as not to be exposed to oxygen or moisture in the air.

In step S10, the metal chloride may include YCl ₃ .

In step S20, LiCl, Li ₂ O, and metal (M) chloride are added together with balls in a ball milling container at an appropriate molar ratio so as to have a composition ratio of Formula 1, and then synthesized by ball milling to obtain a chloride-based solid electrolyte according to Formula 1. manufacture A container made of zirconia may be used as a container for ball milling, and a zirconia ball may be used as a bowl.

As such, the chloride-based solid electrolyte prepared by the manufacturing method according to the present invention has a composition in which some of the chlorine ions (Cl ^- ) are replaced with oxygen ions (O ^2- ) in the existing chloride-based solid electrolyte represented by Li ₃ MCl ₆ . have The chloride-based solid electrolyte according to the present invention can be represented by Chemical Formula 1.

Since some of the chlorine ions (Cl ^- ) are replaced by oxygen ions (O ^2- ), the content (c) of oxygen ions (O ^2- ) replaced by chlorine ions (Cl ^- ) is lost. ^- It may be the same as the content (b) of ). That is, it may be b=c.

During the ball milling process, the chloride-based solid electrolyte according to the present invention may contain more or less lithium compared to the conventional chloride-based solid electrolyte represented by Li ₃ MCl ₆ . For example, lithium ions may be added in the same manner as the content (c) of oxygen ions (O ^2- ) to be substituted instead of chlorine ions (Cl ⁻ ). That is, a=b=c.

When YCl ₃ is used as the metal chloride in step S20, the prepared chloride-based solid electrolyte can be expressed as LiCl-Li ₂ O-YCl ₃ or Li _3+a YCl _6-b O _c .

The chloride-based solid electrolyte prepared by the manufacturing method of the present invention is a glass-based chloride-based solid electrolyte.

The chloride-based solid electrolyte according to the present invention is used in an all-solid-state battery. An all-solid-state battery includes a solid electrolyte membrane, an anode, a cathode, and a separator. Here, the chloride-based solid electrolyte is included in at least one of a solid electrolyte membrane, an anode, a cathode, and a separator. The chloride-based solid electrolyte according to the present invention included in at least one of the solid electrolyte membrane, anode, cathode, and separator may be used together with a plurality of species having different compositions. For example, an electrode such as an anode or a cathode may include an active material, a binder, a conductive material, and a solid electrolyte. The solid electrolyte included in the electrode includes the chloride-based solid electrolyte according to the present invention, and the chloride-based solid electrolyte may be used together with a plurality of species having different compositions.

In the all-solid-state battery according to the present invention, the chloride-based solid electrolyte according to the present invention is used for at least one of a solid electrolyte membrane, an anode, a cathode, and a separator, and the conventional chloride represented by Li ₃ MCl ₆ together with the chloride-based solid electrolyte according to the present invention A solid electrolyte may be used together.

The chloride-based solid electrolyte prepared by the manufacturing method of the present invention has a chemical composition in which some of the chlorine ions (Cl ⁻ ) are replaced with oxygen ions (O ²⁻ ) in the solid electrolyte represented by Li ₃ MCl ₆ .

As described above, the chloride-based solid electrolyte according to the present invention replaces some of the chlorine ions (Cl ^- ) with oxygen ions (O ^2- ), so that, unlike the existing chloride-based solid electrolytes of Li ₃ MCl ₆ , the structural , providing thermal and chemical stability while maintaining ionic conductivity.

Since the chloride-based solid electrolyte according to the present invention does not crystallize even at 100° C., it is possible to solve the problem of decrease in ionic conductivity due to crystallization of the chloride-based solid electrolyte.

In addition, since the chloride-based solid electrolyte according to the present invention can suppress side reactions with the cathode material, it provides improved thermal and chemical stability. As a result, the all-solid-state battery employing the chloride-based solid electrolyte according to the present invention can operate at high temperatures.

[Examples and Comparative Examples]

In order to confirm the electrical conductivity, thermal and chemical stability of the chloride-based solid electrolyte prepared by the manufacturing method of the present invention, chloride-based solid electrolytes according to Examples and Comparative Examples were prepared as follows.

Comparative Example 1

A chloride-based solid electrolyte according to Comparative Example 1 was prepared by adding the starting materials LiCl and YCl ₃ together with zirconia balls having a diameter of 5 mm in a zirconia container at a molar ratio of 3:1, followed by ball milling for 10 hours.

Example 1-6

The starting materials LiCl, Li ₂ O, and YCl ₃ were added together with zirconia balls having a diameter of 5 mm in a zirconia container at a molar ratio according to Table 1, followed by ball milling for 10 hours to obtain a chloride system according to Examples 1-6. A solid electrolyte was prepared.

In the chloride-based solid electrolyte according to Example 1-6, the content (c) of oxygen ions (O ^2- ) substituted instead of chlorine ions (Cl ⁻ ) is 0.03≤c≤0.3, and a=b=c . That is, a+b-2c=0. The chloride-based solid electrolyte according to Examples 1-6 can be expressed as Li _3+3x YCl _6-3x O _3x (3x=c).

chemical formula Ionic conductivity before storage
(S/cm, 25℃)-A Ionic conductivity after storage
(S/cm, 25℃-B) Ionic conductivity retention rate
(%)-B/A Comparative Example 1 Li ₃ YCl ₆ 4.0*10^-4 3.7*10^-5 9.25 Example 1 Li _3.075 YCl _5.925 O _0.075 3.0*10^-4 1.6*10^-4 53.33 Example 2 Li _3.150 YCl _5.850 O _0.150 2.6*10^-4 2.9*10^-4 111.54 Example 3 Li _3.225 YCl _5.775 O _0.225 1.4*10^-4 1.4*10^-4 100.00 Example 4 Li _3.300 YCl _5.700 O _0.300 1.4*10^-4 1.9*10^-4 135.71 Example 5 Li _3.375 YCl _5.625 O _0.375 1.4*10^-4 1.6*10^-4 156.25 Example 6 Li _3.450 YCl _5.550 O _0.450 1.1*10^-4 4.3*10^-5 39.09

For the chloride-based solid electrolytes according to Comparative Example 1 and Examples 1-6, ion conductivities were measured through an AC-impedance method. In order to confirm thermal stability, after heat treatment at 100 ° C. for 12 hours in a vacuum, X-ray diffraction analysis and ionic conductivity were measured, and the results are shown in FIGS. 2, 3 and Table 1.

2 is a graph showing the results of X-ray diffraction analysis of chloride-based solid electrolytes according to Examples and Comparative Examples. And Figure 3 is a graph showing the results of X-ray diffraction analysis after 100 ℃ heat treatment of the chloride-based solid electrolyte according to Examples and Comparative Examples.

Referring to FIGS. 2, 3 and Table 1, it can be confirmed that the chloride-based solid electrolyte according to Examples 1-6 has a crystal structure similar to that of trigonal Li ₃ YCl ₆ as a result of X-ray rotation analysis. there was.

The ion conductivity of the chloride-based solid electrolyte according to Comparative Example 1 was measured as 4.0 × 10^-4 S/cm at room temperature, and after heat treatment in a vacuum of 100 °C, it decreased to 3.7 × 10^-5 S/cm. Therefore, the ionic conductivity retention rate of the chloride-based solid electrolyte according to Comparative Example 1 was calculated to be 9.25%.

As such, the reason why the ion conductivity retention rate of the chloride-based solid electrolyte according to Comparative Example 1 is low is determined to be the result of the tendency for crystallization to occur even at a relatively low temperature of 100 °C.

The ionic conductivity of the chloride-based solid electrolyte according to Examples 1-6 after heat treatment at room temperature and vacuum at 100 ° C is shown in Table 1. The ionic conductivity retention rate of the chloride-based solid electrolyte according to Examples 1-6 was calculated to be 53.33 to 156.25%.

As shown in FIGS. 2 and 3, the chloride-based solid electrolyte according to Examples 1-6 did not undergo crystallization even after heat treatment in a vacuum of 100° C.

As a result, it was confirmed that the chloride-based solid electrolyte according to Examples 1-6 had an ionic conductivity retention rate of 53.33% or more. Furthermore, it was confirmed that the chloride-based solid electrolyte according to Example 2 had a high ionic conductivity retention rate of 111.54%.

As described above, since the chloride-based solid electrolyte according to Examples 1-6 does not crystallize even at 100 ° C. compared to the chloride-based solid electrolyte according to Comparative Example 1, it shows good ion conductivity retention.

On the other hand, the embodiments disclosed in this specification and drawings are only presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is obvious to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

Claims (12)

A chloride-based solid electrolyte represented by the chemical formula below.
[chemical formula]
Li _3+a MCl _6-b O _c
(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and at least one of Ce, -0.5<a+b-2c<0.5, 0<c ≤0.3) According to claim 1,
The chloride-based solid electrolyte, characterized in that M is Y. According to claim 1,
A chloride-based solid electrolyte, characterized in that b and c are the same. A method for producing a chloride-based solid electrolyte represented by the following chemical formula prepared by ball milling LiCl, Li ₂ O, and a metal (M) chloride.
[chemical formula]
Li _3+a MCl _6-b O _c
(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and at least one of Ce, -0.5<a+b-2c<0.5, 0<c ≤0.3) According to claim 4,
The metal chloride is a method for producing a chloride-based solid electrolyte, characterized in that it comprises YCl ₃ . According to claim 4,
A method for producing a chloride-based solid electrolyte, characterized in that b and c are the same. An all-solid-state battery comprising a chloride-based solid electrolyte represented by the following chemical formula.
[chemical formula]
Li _3+a MCl _6-b O _c
(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Al, Y, In, Ga, Yb, Er, and at least one of Ce, -0.5<a+b-2c<0.5, 0<c ≤0.3) According to claim 7,
The all-solid-state battery includes a solid electrolyte membrane, an anode, a cathode, and a separator,
The all-solid-state battery, characterized in that the chloride-based solid electrolyte is included in at least one of the solid electrolyte membrane, the positive electrode, the negative electrode, and the separator. According to claim 7,
An all-solid-state battery, characterized in that a plurality of species having different compositions are used for the chloride-based solid electrolyte included in at least one of the solid electrolyte membrane, the positive electrode, the negative electrode, and the separator. According to claim 7,
The chloride-based solid electrolyte is an all-solid-state battery, characterized in that prepared by synthesizing LiCl, Li ₂ O and metal (M) chloride by ball milling. According to claim 10,
The metal chloride is an all-solid-state battery, characterized in that it comprises YCl ₃ . According to claim 7,
An all-solid-state battery further comprising a chloride-based solid electrolyte represented by Li ₃ MCl ₆ .

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