KR102590896B1 - Method for preparing solid electrolyte and solid electrolyte prepared therefrom - Google Patents

Abstract

The present invention relates to a method for manufacturing a solid electrolyte and a solid electrolyte prepared therefrom. The present invention relates to a solid electrolyte having high ionic conductivity, small particle size, and uniform particle size by using an amine-based organic solvent and controlling the mixing order of the precursors. It is possible to provide a manufacturing method for manufacturing simply and inexpensively.

Description

Method for preparing solid electrolyte and solid electrolyte prepared therefrom}

The present invention relates to a method for producing a solid electrolyte and a solid electrolyte produced therefrom.

Lithium-ion batteries are used in many portable applications such as cell phones, laptops, video cameras and medical devices, and their high energy density allows them to be used in electric and hybrid electric vehicles.

However, since commercially available lithium-ion batteries use a flammable liquid electrolyte, the internal temperature of the battery system rises when a short circuit occurs, which poses a risk of explosion. To prevent this, use a non-flammable organic electrolyte or a device to suppress the temperature rise. Or, an additional system to prevent short circuit is required.

Therefore, instead of liquid electrolytes, much research is being conducted on solid electrolytes that have the advantages of excellent thermal stability at high temperatures, simple battery design, and low manufacturing costs.

However, the performance of batteries using solid electrolytes, such as capacity and output, does not match that of existing liquid electrolyte batteries due to low ionic conductivity, and existing solid electrolytes manufactured through the ball milling process require a long manufacturing time and high costs. Therefore, there were limits to mass production.

As an alternative to the ball milling process, solid electrolytes prepared through a solution process are disclosed in Patent Documents 1 to 4. For example, Patent Document 1 describes a solution process of crystalline Li ₃ PS ₄ using THF as a solvent. and its conductivity is about 10 ^-4 S/cm ^-1 . In addition, Patent Documents 2, 3, and 4 disclose toluene, NMP, and DME as organic solvents for solution synthesis of sulfide solid electrolyte, respectively, but these showed lower ionic conductivity than Patent Document 1.

Therefore, a solid electrolyte that can be mass-produced through a solution process and has high ionic conductivity is required.

U.S. Publication No. 2016-0104917 Japanese Patent Publication No. 2010-140893 International Publication No. 2004-093099 U.S. Publication No. 2015-0093652

The purpose of the present invention is to provide a solid electrolyte that has high ionic conductivity, has uniform particle size and distribution, and is capable of mass production.

The present invention includes the steps of mixing a first precursor containing a chalcogen element selected from the group consisting of S, Se, and O in an amine-based organic solvent to form a first precursor-solvent complex; and mixing a second precursor containing an alkali element selected from the group consisting of Li, Na, and K into the composite.

As an example, the amine-based organic solvent may be a solid electrolyte that is monoamine or diamine.

As an example, the amine-based organic solvent may be at least one selected from the group consisting of ethylenediamine, propylenediamine, and trimethylenediamine.

As an example, the first precursor may further include one element selected from the group consisting of P, Si, Al, B, Ge, Sn, Sb, Nb, Mo, and Bi.

As an example, the second precursor may be sulfide, selenide, or oxide.

As an example, the molar ratio of the first precursor and the second precursor may be 1:2 to 1:6.

As an example, the step of mixing a third precursor containing a halogen element selected from the group consisting of Cl, Br, I, and F with the composite may be further included.

As an example, a method for producing a solid electrolyte comprising 10 to 50 mol% of the second precursor and 3 to 50 mol% of the third precursor based on the total precursors.

As an example, a drying step to remove the solvent; And it may further include a heat treatment step.

As an example, the drying step may be performed at a temperature of 150 to 250°C for 3 to 7 hours.

As an example, the heat treatment step may be performed at 200 to 600°C.

Additionally, the present invention can provide a solid electrolyte manufactured using the above manufacturing method.

As an example, the solid electrolyte may have a particle size of 0.5 to 2 μm.

As an example, the solid electrolyte is Li ₂ S, Li ₃ PS ₄ , Li ₇ PS ₆ , Li ₇ P ₃ S ₁₁ , Li ₈ P ₂ S ₉ , Li ₉ P ₃ S ₁₂ , and argyrodite. ) may be at least one of the following types.

As an example, the babyrodite type may be at least one of Li _5.4 PS _4.4 Cl _1.6, Li _5.5 PS _4.5 Cl _1.3 , and Li _5.7 PS _4.7 Cl _1.3 .

As an example, the solid electrolyte may have an ionic conductivity of 10 ^-3 S/cm or more at 25°C.

Additionally, the present invention can provide an all-solid-state battery including the solid electrolyte.

The present invention can provide a solid electrolyte with high ionic conductivity, small and uniform particle size, and a manufacturing method for manufacturing a solid electrolyte simply and inexpensively.

1(a) to 1(c) are schematic diagrams of a solid electrolyte manufacturing method according to an embodiment of the present invention.
Figure 2 shows the XRD measurement results of Examples 2 and 4 of the present invention.
Figure 3 shows the XRD measurement results of Examples 7 and 8 of the present invention.
Figure 4 shows the XRD measurement results of Examples 10 to 14 of the present invention.
Figure 5 shows the XRD measurement results of Examples 15 to 17 of the present invention.
Figure 6 shows the XRD measurement results of Examples 19 to 20 and Comparative Examples of the present invention.
Figure 7 shows the ionic conductivity measurement results of Examples 1 to 6 of the present invention.
Figure 8 shows the ionic conductivity measurement results of Examples 7 to 9 of the present invention.
Figure 9 shows the ionic conductivity measurement results of Examples 10 to 14 of the present invention.
Figure 10 shows the ionic conductivity measurement results of Examples 15 to 17 of the present invention.
Figure 11 shows the ionic conductivity measurement results of Examples 18 to 20 and Comparative Examples of the present invention.
Figure 12 is an SEM image according to Example 13 and Comparative Example of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

In the present invention, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Therefore, the configuration shown in the embodiments described in this specification is only one of the most preferred embodiments of the present invention and does not represent the entire technical idea of the present invention, so various equivalents can be substituted for them at the time of filing the present application. There may be variations.

1. Solid electrolyte composition

The solid electrolyte composition according to the present invention includes an amine-based organic solvent, a first precursor containing a chalcogen element selected from the group consisting of S (sulfur), Se (selenium), and O (oxygen), Li (lithium), and Na (sodium). ) and a second precursor containing an alkali element selected from the group consisting of K (potassium).

In addition, the solid electrolyte composition according to the present invention may further include a third precursor containing a halogen element selected from the group consisting of Cl (chlorine), Br (bromine), and I (iodine).

(1) Amine-based organic solvent

Amine-based organic solvents according to the present invention include monoamines, diamines, triamines and tetraamines.

The monoamines include propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, triethylamine, N, N-diisopropylethylamine, and N-methyldiamine. Propylamine, tripropylamine, tributylamine, triisobutylamine, trihexylamine, trioctylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, pyrrolidine, piperidine, methylpyrrolidine Peridine, peridine, 2,2-hydroquinoline, 6-tetramethylpiperidine, tetrahydroquinoline, N-methylcyclohexylamine, dicyclohexylamine, N,N-dimethylcyclohexylamine and N, N- It may be dicyclohexylmethylamine, for example, propylamine.

The diamines include ethylenediamine, propylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, and N,N'-diisopropylethylenediamine. , N,N'-di-tert-butylethylenediamine, N,N'-dibenzylethylenediamine, N,N'-dimethyl-1,3-propanediamine, N,N'-diethyl-1,3- Propanediamine, N,N'-diisopropyl-1,3-propanediamine, N,N'-dimethyl-1,6-hexanediamine, N,N,N',N'-tetramethylethylenediamine, N, N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetraethyl-1,3- Propanediamine, N,N,N',N'-tetramethyl-1,4-butanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, N-methylethylenediamine, N ,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, 1,2-diaminocyclo It may be hexane, 5-amino-1,3,3-trimethylcyclohexanemethylamine and m-xylylenediamine, for example, ethylenediamine (EDA), propylenediamine (1,2-diaminopropane) Or it may be trimethylenediamine (1,3-diaminopropane).

The triamine is diethylenetriamine, N,N-diethyldiethylenetriamine, N,N,N',N'-tetraethyldiethylenetriamine, N,N,N',N'',N' '-Pentamethyldiethylenetriamine, dipropylenetriamine, N,N-dimethyldipropylenetriamine, 3,3'-diamino-N-methyldipropylamine and 3,3'-iminobis (N, N -dimethylpropylamine).

The tetraamine includes triethylenetetramine, N,N'-bis(2-aminoethyl)-1,3-propanediamine, tris(2-aminoethyl)amine, tris[2-(methylamino)ethyl]amine, It may be tris[2-(dimethylamino)ethyl]amine and 1,1,4,7,10,10-hexamethyltriethylenetetraamine.

The amine-based organic solvent may be a single amine, a mixture of two or more amines, or a mixture of an amine and an alcohol.

The alcohol may be methanol, ethanol, propanol, or butanol, for example, ethanol.

When the solvent used in the present invention is a mixture of an amine-based organic solvent and an alcohol, the mixing ratio may be 3:7(v) to 7:3(v), for example, 4:6(v) to 6. :4(v).

By having a substituent of an amino group, the amine-based solvent can function as a catalyst for reacting the first precursor and the second precursor to obtain a result in which the first precursor and the second precursor are combined.

The amine-based solvent may dissolve the first precursor, but may render the second precursor insoluble.

(2) first precursor

The first precursor according to the present invention includes a chalcogen element selected from the group consisting of S (sulfur), Se (selenium), and O (oxygen).

In addition, the first precursor is P (phosphorus), Si (silicon), Al (aluminum), B (boron), Ge (germanium), Sn (tin), Sb (antimony), Nb (niobium), and Mo (molybdenum). and Bi (bismuth).

That is, the first precursor is a chalcogen element selected from the group consisting of S (sulfur), Se (selenium), and O (oxygen), P (phosphorus), Si (silicon), Al (aluminum), B (boron), It may contain one element selected from the group consisting of Ge (germanium), Sn (tin), Sb (antimony), Nb (niobium), Mo (molybdenum), and Bi (bismuth).

The first precursor may be a chalcogenide. For example, the first precursor may be a metal sulfide.

Examples of the first precursor include P ₂ O ₃ , P ₂ S ₅ , SiS ₂ , SiSe _{2 ,} Al ₂ S ₃ , Al ₂ Se 3 , Al 2 O ₃ , _{B 2 S 3} , B ₂ Se ₃ , B ₂ O ₅ , GeS ₂ , GeSe ₂ , GeO ₂ , SnS ₂ , SnSe ₂ , SnO ₂ , Sb 2 S ₃ , Sb ₂ Se ₃ , Sb ₂ O ₅ , MoS ₂ , NbSe _{2 ,} NbS ₂ , Bi ₂ S ₃ , Bi ₂ Se ₃ or Bi ₂ O ₃ , specifically P ₂ S ₅ .

The second precursor may be used alone or in a mixture of two or more of the above-mentioned compounds.

(3) second precursor

The second precursor according to the present invention includes an alkali element selected from the group consisting of Li (lithium), Na (sodium), and K (potassium).

Specifically, the second precursor may be sulfide, selenide, or oxide.

That is, the second precursor according to the present invention is a sulfide, selenide, or oxide containing an alkali element selected from the group consisting of Li (lithium), Na (sodium), and K (potassium).

When the second precursor is sulfide, the second precursor may be lithium sulfide (Li ₂ S), sodium sulfide (Na ₂ S), or potassium sulfide (K ₂ S).

When the second precursor is selenide, the first precursor may be lithium selenide (Li ₂ Se), sodium selenide (Na ₂ Se), or potassium selenide (K ₂ Se).

When the second precursor is an oxide, the first precursor may be lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), or potassium oxide (K ₂ O).

For example, the second precursor may be lithium sulfide (Li ₂ S) or lithium selenide (Li ₂ Se), and specifically, the second precursor may be lithium sulfide (Li ₂ S).

The second precursor may be used alone or in a mixture of two or more of the above-mentioned compounds.

(4) Third precursor

The solid electrolyte composition according to the present invention may further include a third precursor containing a halogen element selected from the group consisting of Cl (chlorine), Br (bromine), I (iodine), and F (fluorine).

The third precursor may be a halide, for example, lithium halide, sodium halide, potassium halide, sulfur halide, selenium halide, aluminum halide, silicon halide, germanium halide, phosphorus halide. , tin halide, antimony halide, niobium halide or bismuth halide.

The lithium halide may be LiCl, LiBr, LiI or LiF, the sodium halide may be NaCl, NaBr, NaI or NaF, and the potassium halide may be KCl, KBr, KI or KF.

The sulfur halide may be SCl ₂ , S ₂ Cl ₂ , S ₂ Br ₂ , SF ₂ , SF ₄ or SF ₅ , and the selenium halide may be SeCl ₂ , SeCl ₄ , SeF ₆ or SeBr _{4 ,} The aluminum halide is It may be AlCl ₃ , AlBr ₃ , AlI ₃ or AlF ₃ .

The silicon halide may be SiCl ₄ , SiBr ₄ , SiI ₄ , SiF ₄ , SiBr ₂ Cl _2, or Si ₂ Cl ₆ , and the germanium halide may be GeCl ₄ , GeCl ₂ , GeBr ₄ , GeBr ₂ , GeI ₄ , It may be GeI ₂ , GeF ₄ or GeI ₄ , and the phosphorus halide may be PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , PI ₃ , PI ₅ , PF ₃ or PF ₅ .

The tin halide may be SnCl ₄ , SnCl ₂ , SnBr ₄ , SnBr ₂ , SnI ₄ , SnI ₂ , SnF ₄ or SnF ₂ , and the antimony halide may be SbCl ₃ , SbCl ₅ , SbBr ₃ , SbBr ₅ , SbI ₃ , SbI ₅ , SbF ₃ or SbF ₅ , the niobium halide may be NbCl ₅ , NbBr ₅ , NbI ₅ and NbF ₅ , and the bismuth halide may be BiCl ₃ , BiBr ₃ , BiF ₃ and BiI ₃ It can be.

For example, the third precursor may be LiCl, LiBr, LiI, SiCl ₄ , SiBr ₄ or SiI ₄ , and specifically, the third precursor may be LiCl or LiBr.

The third precursor may be used alone or in a mixture of two or more of the above-mentioned compounds.

(5) Additional compounds

An organometallic compound can be added to the solid electrolyte composition according to the present invention.

The organometallic compound may be an organosilane compound, an organic germanium compound, an organoaluminum compound, or an organotin compound.

The organic silane compounds include methylsilane, ethylsilane, butylsilane, hexylsilane, octadecylsilane, diethylsilane, di-tert-butylsilane, triethylsilane, tetramethylsilane, tetraethylsilane, tetrabutylsilane, and hexamethyl Disilazane, bis(dimethylamino)silane, bis(diethylamino)silane, tris(diethylamino)silane, bis(dimethylamino)dimethylsilane, phenylsilane, diphenylsilane, triphenylsilane, methyldiphenylsilane , dimethylphenylsilane, or benzyldimethylsilane.

The organic germanium compound may be tetramethyl germanium, tetraethyl germanium, or hexamethyldigermanium.

The organoaluminum compound may be trimethylaluminum, triethylaluminum, or triisobutylaluminum.

The organic tin compound may be tetramethyltin, tetraethyltin, trimethyl(phenyl)tin, or tetrabutyltin.

The organometallic compound may be, for example, tetraethylsilane or tetrabutyltin.

In addition to the organometallic compounds, _the solid electrolyte composition according to the present invention contains Li ₄ SiS ₄ , Li ₄ GeS ₄ , _{Li 4 SiSe 4 , Li 4 GeSe 4 , Li 4 SnS 4 , Li 4 SnSe 4 , Li 3 SbS 4 .} Li ₃ SbSe ₄ , Li ₃ AlS ₃ , Li ₃ AlSe ₃ , Na ₄ SiS ₄ , Na ₄ GeS ₄ , Na ₄ SiSe ₄ , Na ₄ GeSe ₄ , Na ₄ SnS ₄ , Na ₄ SnSe ₄ , Na ₃ SbS ₄ . It may include at least one selected from the group consisting of Na ₃ SbSe ₄ , Na ₃ AlS _{3 ,} Na ₃ AlSe ₃ and mixtures thereof. For example, the solid electrolyte composition according to the present invention includes Li ₄ SiS ₄ or Li ₄ It may further include GeS ₄ .

(6) Proportion of composition

The solid electrolyte composition according to the present invention may include 40 to 90% of the first precursor based on the total amount of precursors, for example, the first precursor may be 40 to 80% or 40 to 73% based on the total amount of precursors. , 45 to 67%, 45 to 65%, 45 to 60%, or 45 to 53%.

Specifically, when the solid electrolyte composition according to the present invention does not include the third precursor, the second precursor may be 60 to 90%, for example, 60 to 80% or 65 to 73%.

At this time, the molar ratio of the first precursor and the second precursor may be 1:2 to 1:6. For example, the molar ratio of the first precursor and the second precursor may be 1:2 to 1:4, 1:2. It may be from 1:3 or 1:2 to 2:5.

In addition, when the solid electrolyte composition according to the present invention includes a third precursor, the first precursor may be 10 to 50 mol% based on the total amount of precursors. For example, the first precursor may be 10 to 50 mol% based on the total amount of precursors. It may be 10 to 40 mol%, 10 to 28 mol%, or 10 to 20 mol%.

In addition, when the solid electrolyte composition according to the present invention includes a third precursor, the third precursor may be 3 to 50 mol% based on the total amount of precursors. For example, the third precursor may be 3 to 50 mol% based on the total amount of precursors. It may be 20 to 50 mol%, 28 to 50 mol%, 30 to 42 mol%, 35 to 42 mol%, or 35 to 38 mol%.

The total weight of the first precursor, second precursor, and third precursor may be 0.01 g/mL to 0.05 g/mL based on the volume of the solvent. For example, the total weight of the precursors may be 0.01 g/mL to 0.05 g/mL based on the volume of the solvent. It may be 0.02 g/mL to 0.04 g/mL.

Below this range, the precursor cannot be sufficiently dissolved or dispersed, and the viscosity of the solution increases, making it difficult to form a solid electrolyte. In addition, if it exceeds the above range, the time for the drying step to remove the solvent becomes longer, which may reduce productivity.

2. Manufacturing method of solid electrolyte

The present invention provides a method for producing a solid electrolyte using the solid electrolyte composition.

Referring to Figure 1(a), the method for producing a solid electrolyte according to the present invention is to mix a first precursor containing a chalcogen element selected from the group consisting of S, Se, and O in an amine-based organic solvent to form the first precursor- Forming a solvent complex (S100); and mixing a second precursor containing an alkali element selected from the group consisting of Li, Na, and K into the composite (S200).

At this time, the amine-based solvent described above may be used.

The second precursor is not dissolved in the amine-based solvent. However, the first precursor may be dissolved in the amine-based solvent. For example, when the first precursor is P ₂ S ₅ , the first precursor may be completely dissolved in the solvent to generate a green solution.

The first precursor may be completely dissolved in the solvent to form a first precursor-solvent complex. The first precursor-solvent complex may dissolve the second precursor. For example, when the second precursor is Li ₂ S, the second precursor may be dissolved in the first precursor-solvent complex.

Specifically, when the second precursor is Li ₂ S, the first precursor is P ₂ S ₅ , and the amine-based solvent is ethylenediamine (EDA), Li ₂ S is not soluble in EDA, but P ₂ S ₅ can be dissolved in EDA to form a P ₂ S ₅ -EDA complex, and when Li ₂ S is mixed with the P ₂ S ₅ -EDA complex, Li ₂ S is dissolved in the P ₂ S ₅ -EDA complex. At this time, the solubility of Li ₂ S varies depending on the concentration of P ₂ S ₅ present in the P ₂ S ₅ -EDA complex.

The mixture obtained in the above order can provide high ionic conductivity to the prepared solid electrolyte. Amine-based solvents can easily form a first precursor-second precursor bond due to the substituent of the amino group, but it has conventionally been difficult to use them due to problems with the solubility of the second precursor.

The method for producing a solid electrolyte according to the present invention first dissolves the first precursor in a solvent and then dissolves the second precursor, thereby forming a good bond between the first precursor and the second precursor, thereby increasing ionic conductivity.

Referring to FIG. 1(b), when the method for producing a solid electrolyte according to the present invention further includes a third precursor, it may further include mixing the third precursor with the first precursor-solvent complex (S210). You can.

At this time, the step of mixing the third precursor with the first precursor-solvent complex (S210) may be configured separately from the step of mixing the second precursor (S200) as shown in FIG. 1(b), or as shown in FIG. 1(c) ), it may be added in the form of mixing the second precursor and the third precursor together (S220).

The step of mixing the first precursor with the solvent or the step of mixing the second precursor and/or the third precursor into the first precursor-solvent complex is performed by stirring at 400 to 1200 rpm, 25° C. to 80° C., and 30 to 60 minutes. can do.

In addition, the method for producing a solid electrolyte may further include a drying step of removing the solvent from the mixture (S300) and a step of heat treating the dried mixture (S400).

The drying step (S300) is a step of recovering the solid electrolyte powder by removing the remaining solvent, and can be performed at 150 to 250°C for 3 to 7 hours.

The heat treatment step (S400) can be performed at 200 to 700°C for 1 to 15 hours.

Specifically, the heat treatment step (S400) is a step of heat treating the solid electrolyte powder, and the appropriate heat treatment temperature may vary depending on the composition of the solid electrolyte.

For example, when the composition of the solid electrolyte is Li ₃ PS ₄ , the heat treatment temperature may be 200 to 400°C, specifically 250 to 350°C, 280 to 350°C, or 280 to 340°C. At this time, the heat treatment time may be 2 to 5 hours.

In addition, for example, the composition of the solid electrolyte is Li- ₂ S, Li ₇ PS ₆ , In the case of Li ₈ P ₂ S ₉ or argyrodite type, the heat treatment temperature may be 400 to 700°C, specifically 450 to 650°C, 500 to 600°C, or 430 to 570°C. At this time, the heat treatment time may be 5 to 15 hours or 7 to 12 hours.

The method for producing a solid electrolyte according to the present invention has the advantage of being a safe process because it does not generate toxic gases such as H ₂ S or SO ₂ during the process.

In addition, there is no need to obtain the first precursor-second precursor or first precursor-second precursor-third precursor combination by synthesis or calcination, and it does not require a high-cost and low-productivity pulverization process, so it is low-cost and simple. A solid electrolyte can be obtained easily.

3. Solid electrolyte

The present invention provides a solid electrolyte prepared using the above composition or a solid electrolyte prepared using the above solid electrolyte preparation method.

The solid electrolyte according to the present invention may have a particle size of 0.5 to 2 um. The average particle size can be measured through SEM images. For example, the solid electrolyte may have a particle size of 0.6 to 1.8 um or 0.8 to 1.5 um.

When applied to an all-solid-state battery, a solid electrolyte having a small particle size as described above has good adhesion and can increase efficiency.

In addition, by having the above-mentioned small particle size, the contact area can be expanded and the ionic conductivity can be increased accordingly.

The solid electrolyte is at least one of Li ₂ S, Li ₃ PS ₄ , Li ₇ PS ₆ , Li ₇ P ₃ S ₁₁ , Li ₈ P ₂ S ₉ , Li ₉ P ₃ S ₁₂ , and argyrodite type. It may be, and the baby rhodite type may be at least one of Li _5.4 PS _4.4 Cl _1.6, Li _5.5 PS _4.5 Cl _1.3 , and Li _5.7 PS _4.7 Cl _1.3 .

The form of the solid electrolyte can be confirmed through X-ray diffraction analysis.

The solid electrolyte may have an ionic conductivity of 10 ^-3 S/cm or more at 25°C. Specifically, the ionic conductivity can be measured using a Biologic SP 300 instrument in the frequency range of 7 MHz to 1 Hz at 25°C.

4. All-solid-state battery

The present invention provides an all-solid-state battery containing the above solid electrolyte.

The all-solid-state battery includes an anode, a cathode, and a solid electrolyte layer provided between the anode and the cathode. The solid electrolyte according to the present invention may be included in at least one of the anode, the cathode, and the solid electrolyte layer.

Example

Example 1

A sulfide solid electrolyte was prepared using lithium sulfide (Li ₂ S, purity: 99.9%, Aldrich) and phosphorus pentasulfide (P ₂ S ₅ , purity: 99%, Aldrich). In a glove box under Ar atmosphere, Li ₂ S and P ₂ S ₅ were taken at a molar ratio of 75.0:25.0 (Li ₃ PS ₄ ). First, P ₂ S ₅ was mixed with 20 mL of ethylenediamine (EDA) solvent and stirred until a green solution was formed. After P ₂ S ₅ was completely dissolved in EDA, Li ₂ S was added. The mixture was stirred at 800 rpm at 25°C for 30 minutes to form a clear solution. Afterwards, the mixture was vacuum dried at 180°C for 5 hours to remove the organic solvent. Finally, a solid electrolyte was prepared by heat treatment at 260°C for 3 hours at a heating rate of 2°C/min.

Example 2 and Example 3

A solid electrolyte was prepared in the same manner as Example 1, except that the heat treatment temperature was 300°C (Example 2) and 340°C (Example 3).

Examples 4 to 6

Except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 70.0:30.0, and the heat treatment was changed to 260 ℃ (Example 4), 300 ℃ (Example 5), and 340 ℃ (Example 6), respectively. prepared a solid electrolyte in the same manner as Example 1.

Example 7

A solid electrolyte was prepared in the same manner as in Example 1, except that 40 mL of EDA was used and the heat treatment temperature and time were changed to 550°C and 10 hours.

Example 8

Sulfide solid electrolyte using lithium sulfide (Li ₂ S, purity: 99.9%, Aldrich), phosphorus pentasulfide (P ₂ S ₅ , purity: 99%, Aldrich), and lithium chloride (LiCl, purity: 99.9%, Aldrich). was manufactured. In a glove box under Ar atmosphere, Li ₂ S, P ₂ S ₅ and LiCl were taken according to the molar ratio of 70.83:25.0:4.17. First, P ₂ S ₅ was mixed with 20 mL of ethylenediamine (EDA) solvent and stirred until a green solution was formed. After P ₂ S ₅ was completely dissolved in EDA, Li ₂ S and LiCl were added. The mixture was stirred at 800 rpm at 25°C for 30 minutes to form a clear solution. Afterwards, the mixture was vacuum dried at 180°C for 5 hours to remove the organic solvent. Finally, a solid electrolyte was prepared by heat treatment at 550°C for 10 hours at a heating rate of 2°C/min.

Example 9

A solid electrolyte was obtained in the same manner as in Example 8, except that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl was changed to 66.66:25.0:8.34.

Example 10

A solid electrolyte was prepared in the same manner as in Example 7, except that 80 mL of EDA was used and the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 87.5:12.5.

Example 11

A solid electrolyte was obtained in the same manner as in Example 8, except that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl was changed to 62.5:12.5:25.0.

Example 12

A solid electrolyte was obtained in the same manner as in Example 8, except that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl was changed to 55.0:12.5:32.5.

Example 13

A solid electrolyte was obtained in the same manner as in Example 8, except that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl was changed to 50.0:12.5:37.5.

Example 14

A solid electrolyte was obtained in the same manner as in Example 8, except that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl was changed to 47.5:12.5:40.0.

Example 15

A solid electrolyte was obtained in the same manner as Example 13, except that the solvent was changed to propylenediamine.

Example 16

A solid electrolyte was obtained in the same manner as Example 12, except that the solvent was changed to trimethylenediamine (TMEDA).

Example 17

A solid electrolyte was obtained in the same manner as Example 13, except that the solvent was changed to trimethylenediamine (TMEDA).

Example 18

A solid electrolyte was obtained in the same manner as in Example 12, except that the solvent was changed to a 5:5 (v) mixture of trimethylenediamine (TMEDA) and ethylenediamine (EDA).

Example 19

A solid electrolyte was obtained in the same manner as in Example 13, except that the solvent was changed to a 5:5 (v) mixture of trimethylenediamine (TMEDA) and ethylenediamine (EDA).

Example 20

A solid electrolyte was obtained in the same manner as in Example 12, except that the solvent was changed to a 5:5 (v) mixture of ethylenediamine (EDA) and ethanol.

Comparative example

A solid electrolyte was obtained in the same manner as in Example 12, except that the solvent was changed to ethanol.

Experiment example

(1) X-ray diffraction (XRD) measurement

Cu Ka radiation (1.5418 ) The structures of the solid electrolytes of the Examples and Comparative Examples were analyzed using a Rigaku-Ultima(IV) X-ray diffractometer.

The X-ray diffraction measurement results are shown in Figures 2 to 6 and Table 1 below.

Referring to FIG. 2, it was confirmed that Examples 2 and 4 had a Li3PS4 crystal structure.

Referring to Figure 3, Examples 7 and 8 showed a crystal structure in which Li ₃ PS ₄ , Li ₇ PS ₆ , and Li ₈ P ₂ S ₉ were mixed.

Referring to FIG. 4, it was confirmed that Example 10 mainly showed the Li ₂ S phase and had a slightly Li ₇ PS ₆ crystal structure. In addition, Example 11 showed the crystal structure of Li ₆ PS ₅ Cl, and Examples 12 to 14 showed babyrodite of Li _5.7 PS _4.7 Cl _1.3 , Li _5.5 PS _4.5 Cl _1.5 , and Li _5.4 PS _4.4 Cl _1.6, respectively. It had a crystal structure.

_{Figure 6 shows the} had the same impurity phase.

division Li ₂ S
(%) P ₂ S ₅
(%) LiCl
(%) menstruum heat treatment
Temperature (℃) form Ion conductivity (S/cm, 25℃) Example 1 75 25 - EDAs 260 Li ₃ PS ₄ 2.85 x 10 ^-5 Example 2 75 25 - EDAs 300 Li ₃ PS ₄ 4.19 x 10 ^-5 Example 3 75 25 - EDAs 340 Li ₃ PS ₄ 3.82 x 10 ^-5 Example 4 70 30 - EDAs 260 Li ₃ PS ₄ 4.12 x 10 ^-5 Example 5 70 30 - EDAs 300 Li ₃ PS ₄ 7.27 x 10 ^-5 Example 6 70 30 - EDAs 340 Li ₃ PS ₄ 6.44 x 10 ^-5 Example 7 75 25 - EDAs 550 Li ₃ PS ₄ , Li ₇ PS _6, Li ₈ P ₂ S ₉ 8.10 x 10 ^-6 Example 8 70.83 25 4.17 EDAs 550 Li ₂ S, Li ₇ PS ₆ 1.20 x 10 ^-4 Example 9 66.66 25 8.34 EDAs 550 Li ₂ S, Li ₇ PS ₆ 1.09 x 10 ^-4 Example 10 87.5 12.5 - EDAs 550 Li ₂ S, Li ₇ PS ₆ 2.26 x 10 ^-6 Example 11 62.5 12.5 25 EDAs 550 Li ₆ PS ₅ Cl 2.38 x 10 ^-3 Example 12 55 12.5 32.5 EDAs 550 Li _5.7 PS _4.7 Cl _1.3 2.42 x 10 ^-3 Example 13 50 12.5 37.5 EDAs 550 Li _5.5 PS _4.5 Cl _1.5 2.87 x 10 ^-3 Example 14 47.5 12.5 40 EDAs 550 Li _5.4 PS _4.4 Cl _1.6 2.59 x 10 ^-3 Example 15 50 12.5 37.5 Propylenediamine 550 Li _5.5 PS _4.5 Cl _1.5 1.93 x 10 ^-3 Example 16 55 12.5 32.5 TMEDA 550 Li _5.7 PS _4.7 Cl _1.3 6.34 x 10 ^-4 Example 17 50 12.5 37.5 TMEDA 550 Li _5.5 PS _4.5 Cl _1.5 4.96 x 10 ^-4 Example 18 55 12.5 32.5 TMEDA+ EDA 550 Li _5.7 PS _4.7 Cl _1.3 6.70 x 10 ^-4 Example 19 50 12.5 37.5 TMEDA+ EDA 550 Li _5.5 PS _4.5 Cl _1.5 7.23 x 10 ^-4 Example 20 55 12.5 32.5 Ethanol+ EDA 550 Li _5.7 PS _4.7 Cl _1.3 9.67 x 10 ^-4 Comparative example 55 12.5 32.5 Ethanol 550 Li _5.7 PS _4.7 Cl _1.3 3.40 x 10 ^-4

(2) Ion conductivity measurement

The prepared solid electrolyte was placed in a mold with a diameter of 10 mm and a pressure of 30 MPa was applied to form a pellet. The thickness of the pellets was 0.11 to 0.12 cm. Afterwards, indium foil was attached to both sides of the pellet to measure ionic conductivity. Ion conductivity analysis was performed using an SP 300 (Biologic) instrument in the frequency range of 7 MHz to 1 Hz at 25°C.

Figures 7 to 11 and Table 1 show the ionic conductivity measured according to the Examples and Comparative Examples of the present invention.

Referring to FIG. 7, in the solid electrolyte having the Li ₃ PS ₄ structure of Examples 1 to 6, the higher the content of the first precursor (P2s5), that is, the molar ratio of the first precursor and the second precursor is 1:3 (practice The ionic conductivity was higher in the case of 3:7 (Examples 4 to 6) than in the case of Examples 1 to 3).

In addition, when the composition ratio was the same, the heat treatment temperature of 300°C (Examples 2 and 4) showed the highest conductivity. However, as in Example 7, when the heat treatment temperature increased, the ionic conductivity rapidly decreased.

Referring to Figure 8, compared to Example 7, the ionic conductivity of Examples 8 and 9 is much higher. That is, the case containing the third precursor had higher ionic conductivity than the case without it, and in the case of having the same crystal structure as Examples 7 to 9, the ionic conductivity was higher when the content of the third precursor was low.

Referring to FIG. 9, in the agyrhodite crystal structure, ionic conductivity increased as the content of the third precursor (LiCl) increased, but when the content of the third precursor was 40 mol%, the ionic conductivity actually decreased.

Referring to Figure 10, it can be seen that there is a significant difference in ionic conductivity when different types of solvents are used. Specifically, Example 13 using EDA showed 2.87 x 10 ^-3 (S/cm), but Examples 15 to 17 using propylenediamine and TMEDA showed ionic conductivity lower than this.

Referring to Figure 11, when a composite solvent was used, ionic conductivity was shown to be intermediate compared to when a single solvent was used. Ethanol in Example 20 showed the highest ionic conductivity when combined with EDA.

Referring to Table 1, the non-amine-based organic solvent of the comparative example showed lower ionic conductivity compared to Example 12 using the amine-based organic solvent.

This appears to be because the amine-based organic solvent has a substituent that is good at forming a bond between Li ₂ S and P ₂ S ₅ or Li ₂ S, P ₂ S ₅ and LiCl. In addition, it is believed that adjusting the order of addition to the solvent due to differences in solubility had an effective effect on dispersibility.

(3) Particle size measurement by SEM

The particle sizes of Example 13 and Comparative Example were measured using SEM images. Referring to FIG. 12, Example 13 using an EDA solvent showed a particle size of 0.8 to 1.5 μm, while the comparative example using ethanol as a solvent showed a particle size of 0.3 to 3 μm.

Through this, it can be seen that when EDA was used as a solvent, the particle size was small and formed uniformly through excellent dispersibility.

When a solid electrolyte with a small and uniform particle size as described above is applied to a secondary battery, excellent adhesion to the electrode complex is achieved.

Claims (17)

Forming a first precursor-solvent complex by mixing a first precursor containing a chalcogen element selected from the group consisting of S, Se, and O with at least one amine-based organic solvent selected from the group consisting of diamine, triamine, and tetraamine. steps;
mixing a second precursor containing an alkali element selected from the group consisting of Li, Na, and K into the composite;
mixing a third precursor containing a halogen element selected from the group consisting of Cl, Br, I, and F into the complex;
A drying step of removing the solvent at a temperature of 150 to 250°C for 3 to 7 hours; and
A method for producing a solid electrolyte comprising a heat treatment step performed at 200 to 600°C,
The amine-based solvent can dissolve the first precursor, but is insoluble in the second precursor, and acts as a catalyst to react the first precursor and the second precursor to obtain a result in which the first precursor and the second precursor are combined, providing a combination of the first precursor and the second precursor,
The molar ratio of the first precursor and the second precursor is 1:2 to 1:6,
Comprising 10 to 50 mol% of the second precursor and 3 to 50 mol% of the third precursor based on the total precursor,
The composition of the solid electrolyte further includes an organic silane compound, an organic germanium compound, an organic aluminum compound, or an organic tin compound,
Method for producing a solid electrolyte having an ionic conductivity of 10 ^-3 S/cm or more at 25°C.
delete delete According to paragraph 1,
The first precursor further includes one element selected from the group consisting of P, Si, Al, B, Ge, Sn, Sb, Nb, Mo, and Bi.
According to paragraph 1,
A method of producing a solid electrolyte wherein the second precursor is sulfide, selenide, or oxide. delete delete delete delete delete delete A solid electrolyte manufactured using the manufacturing method of any one of claims 1, 4, and 5.
According to clause 12,
A solid electrolyte with a particle size of 0.5 to 2um.
According to clause 12,
The solid electrolyte is at least one of Li ₂ S, Li ₃ PS ₄ , Li ₇ PS ₆ , Li ₇ P ₃ S ₁₁ , Li ₈ P ₂ S ₉ , Li ₉ P ₃ S ₁₂ , and argyrodite type. Phosphorus solid electrolyte.
According to clause 14,
The agyrhodite type is a solid electrolyte that is at least one of Li _5.4 PS _4.4 Cl _1.6, Li _5.5 PS _4.5 Cl _1.3 , and Li _5.7 PS _4.7 Cl _1.3 .
delete An all-solid-state battery comprising the solid electrolyte of claim 12.