KR20220089899A - Method for preparing solid electrolyte and solid electrolyte prepared therefrom - Google Patents

Abstract

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

Description

Method for preparing a solid electrolyte and a solid electrolyte prepared therefrom

The present invention relates to a method for preparing a solid electrolyte and a solid electrolyte prepared 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 makes them suitable for use in electric and hybrid electric vehicles as well.

However, since commercially available lithium ion batteries use a flammable liquid electrolyte, when a short circuit occurs, the temperature inside the battery system rises and there is a risk of explosion. Alternatively, a system for preventing short circuits is additionally required.

Therefore, many studies have been conducted on solid electrolytes having excellent thermal stability at high temperatures, simple battery design, and low manufacturing cost instead of liquid electrolytes.

However, the battery to which the solid electrolyte is applied does not achieve performance such as capacity and output due to low ionic conductivity, and the conventional solid electrolyte manufactured by the ball milling process requires a long manufacturing time and high cost. Therefore, mass production was limited.

Solid electrolytes prepared through a solution process as an alternative to the ball milling process are disclosed in Patent Documents 1 to 4, for example, in Patent Document 1, a solution process of crystalline Li ₃ PS ₄ using THF as a solvent is described. 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 a sulfide solid electrolyte, respectively, but they exhibited lower ionic conductivity than Patent Document 1.

Therefore, a solid electrolyte having high ionic conductivity while capable of mass production through a solution process is required.

US Publication No. 2016-0104917 Japanese Laid-Open Patent Publication No. 2010-140893 International Publication No. 2004-093099 US Publication No. 2015-0093652

An object of the present invention is to provide a solid electrolyte having high ionic conductivity, uniform particle size and distribution, and mass production possible.

The present invention comprises the steps of mixing a first precursor including 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 including an alkali element selected from the group consisting of Li, Na and K to the composite.

In one embodiment, the amine-based organic solvent may be a solid electrolyte of monoamine or diamine.

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

As an embodiment, 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.

In one embodiment, the second precursor may be a sulfide, selenide or oxide.

In an embodiment, a molar ratio of the first precursor to the second precursor may be 1:2 to 1:6.

As an embodiment, the method may further include mixing a third precursor including a halogen element selected from the group consisting of Cl, Br, I and F to the complex.

As an embodiment, a method of manufacturing 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 precursor.

In one embodiment, a drying step of removing the solvent; and a heat treatment step.

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

In one embodiment, the heat treatment step may be performed at 200 to 600 ℃.

In addition, the present invention can provide a solid electrolyte prepared by using the above manufacturing method.

In one embodiment, the solid electrolyte may have a particle size of 0.5 to 2um.

In one embodiment, the solid electrolyte includes 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 types.

In one embodiment, the aramidite 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 embodiment, the solid electrolyte may have an ionic conductivity at 25° C. of 10 ⁻³ S/cm or more.

In addition, the present invention may provide an all-solid-state battery including the solid electrolyte.

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

1(a) to 1(c) are schematic diagrams of a method for manufacturing a solid electrolyte according to an embodiment of the present invention.
2 is an XRD measurement result of Examples 2 and 4 of the present invention.
3 is an XRD measurement result of Examples 7 and 8 of the present invention.
4 is an XRD measurement result of Examples 10 to 14 of the present invention.
5 is an XRD measurement result of Examples 15 to 17 of the present invention.
6 is an XRD measurement result of Examples 19 to 20 and Comparative Examples of the present invention.
7 is a measurement result of ion conductivity of Examples 1 to 6 of the present invention.
8 is an ionic conductivity measurement result of Examples 7 to 9 of the present invention.
9 is an ionic conductivity measurement result of Examples 10 to 14 of the present invention.
10 is an ionic conductivity measurement result of Examples 15 to 17 of the present invention.
11 is an ionic conductivity measurement result of Examples 18 to 20 and Comparative Examples of the present invention.
12 is an SEM image according to Example 13 and Comparative 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 will be described in detail in the detailed description.

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.

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.

Accordingly, the configuration shown in the embodiments described in the present specification is merely the most preferred embodiment of the present invention and does not represent all the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present application and variations.

1. Solid Electrolyte Composition

The solid electrolyte composition according to the present invention is an amine-based organic solvent, a first precursor including a chalcogen element selected from the group consisting of S (sulfur), Se (selenium) and O (oxygen), and Li (lithium), Na (sodium) ) and a second precursor comprising 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 including a halogen element selected from the group consisting of Cl (chlorine), Br (bromine) and I (iodine).

(1) Amine-based organic solvents

The amine-based organic solvent according to the present invention includes monoamines, diamines, triamines and tetraamines.

The monoamine is propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, triethylamine, N,N-diisopropylethylamine, N-methyldi Propylamine, tripropylamine, tributylamine, triisobutylamine, trihexylamine, trioctylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, pyrrolidine, piperidine, methylpi 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 diamine is ethylenediamine, propylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, 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 (ethylenediamine, EDA), propylenediamine (Propylenediamine, 1,2-diaminopropane) Or trimethylenediamine (Trimethylenediamine, 1,3-diaminopropane) may be.

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 is triethylenetetramine, N,N'-bis(2-aminoethyl)-1,3-propanediamine, tris(2-aminoethyl)amine, tris[2-(methylamino)ethyl]amine, 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 alcohol, the mixing ratio may be 3:7(v) to 7:3(v), for example, 4:6(v) to 6 :4(v).

The amine-based solvent may function as a catalyst for obtaining a result in which the first precursor and the second precursor are combined by reacting the first precursor and the second precursor by having a substituent of an amino group.

In the amine-based solvent, the first precursor may be dissolved, but the second precursor may be 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), Mo (molybdenum) And Bi (bismuth) may further include one element selected from the group consisting of.

That is, the first precursor is a chalcogen element selected from the group consisting of S (sulfur), Se (selenium) and O (oxygen), and P (phosphorus), Si (silicon), Al (aluminum), B (boron), It may include 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.

For example, the first precursor, 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 , and specifically P ₂ S ₅ .

The second precursor may be used alone or as 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 a 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).

The second precursor may be, for example, 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 as 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 including 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 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 is GeCl _{4 , GeCl 2 , GeBr 4 , GeBr 2 , GeI 4} , GeI ₂ , GeF ₄ or GeI ₄ may be used, 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 is 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 . 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 as a mixture of two or more of the above-mentioned compounds.

(5) additional compounds

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

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

The organosilane compound is methylsilane, ethylsilane, butylsilane, hexylsilane, octadecylsilane, diethylsilane, di-tert-butylsilane, triethylsilane, tetramethylsilane, tetraethylsilane, tetrabutylsilane, 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 tetramethylgermanium, tetraethylgermanium, or hexamethyldigermanium.

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

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

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

The solid electrolyte composition according to the present invention, in addition to the organometallic compound, 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 . Na ₃ SbSe ₄ , Na ₃ AlS _{3 ,} Na ₃ AlSe ₃ may include at least one selected from the group consisting of and mixtures thereof, for example, the solid electrolyte composition according to the present invention is Li ₄ SiS ₄ or Li ₄ GeS ₄ may be further included.

(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 the precursor, for example, the first precursor may include 40 to 80%, 40 to 73%, based on the total amount of the precursor. , 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%.

In this case, the molar ratio of the first precursor to the second precursor may be 1:2 to 1:6, for example, the molar ratio of the first precursor to the second precursor is 1:2 to 1:4, 1:2 to 1:3 or 1:2 to 2:5.

In addition, when the solid electrolyte composition according to the present invention includes the third precursor, the first precursor may be 10 to 50 mol% based on the total amount of the precursor, for example, the first precursor is based on the total amount of the precursor. as 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 the third precursor, the third precursor may be 3 to 50 mol% based on the total amount of the precursor, for example, the third precursor is based on the total amount of the precursor. 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, the second precursor, and the 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 precursor may be based on the volume of the solvent. 0.02 g/mL to 0.04 g/mL.

If it is less than the above range, the precursor may not be sufficiently dissolved or dispersed, and the viscosity of the solution may increase, so that it may be difficult to form a solid electrolyte. In addition, when it exceeds the above range, the time of the drying step of removing the solvent may be prolonged, thereby reducing productivity.

2. Manufacturing method of solid electrolyte

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

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

In this case, the amine-based solvent may be the amine-based solvent described above.

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 a solvent to generate a green solution.

The first precursor may be completely dissolved in a 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 dissolved in EDA, but P ₂ S ₅ may be dissolved in EDA to form a P ₂ S ₅ -EDA complex. 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. In this case, 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. The amine-based solvent may well form the first precursor-second precursor bond due to the substituent of the amino group, but it has been difficult to use the amine-based solvent due to the solubility of the second precursor in the prior art.

In the method of manufacturing a solid electrolyte according to the present invention, by dissolving the first precursor in a solvent first and then dissolving the second precursor, a bond between the first precursor and the second precursor can be well formed, thereby increasing ionic conductivity.

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

In this case, 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 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 with 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 of manufacturing the solid electrolyte may further include a drying step of removing the solvent from the mixture (S300) and a heat treatment of the dried mixture (S400).

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

The heat treatment step (S400) may 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 a suitable heat treatment temperature may be different 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. In this case, the heat treatment time may be 2 to 5 hours.

Also, for example, if 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. In this case, the heat treatment time may be 5 to 15 hours or 7 to 12 hours.

The method for manufacturing a solid electrolyte according to the present invention has an advantage in that the process is safe because it does not generate a toxic gas 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 the first precursor-second precursor-third precursor combination by synthesis or firing, and since a pulverization process with high cost and low productivity is not required, it is simple and inexpensive. A solid electrolyte can be obtained.

3. Solid electrolyte

The present invention provides a solid electrolyte prepared by using the composition or a solid electrolyte prepared by using the method for preparing the solid electrolyte.

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

The solid electrolyte having a small particle size as described above has good adhesion when applied to an all-solid-state battery, so that efficiency can be increased.

In addition, by having the small particle size as described above, the contact area may be increased, and thus the ionic conductivity may be increased.

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. may be, and the aramidite 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 shape of the solid electrolyte may be confirmed through X-ray diffraction analysis.

The solid electrolyte may have an ionic conductivity at 25° C. of 10 ⁻³ S/cm or more. Specifically, the ionic conductivity may be measured using a Biologic SP 300 instrument in a 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 including the solid electrolyte.

The all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode, and the solid electrolyte according to the present invention may be included in at least one of the positive electrode, the negative electrode, 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 the glove box of Ar atmosphere, Li ₂ S and P ₂ S ₅ were taken according to 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 obtained. After P ₂ S ₅ was completely dissolved in EDA, Li ₂ S was added. The mixture was stirred at a speed of 800 rpm at 25° C. for 30 minutes to become a clear solution. Thereafter, 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.

Examples 2 and 3

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

Examples 4 to 6

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 ° C. (Example 4), 300 ° C. (Example 5) and 340 ° C. (Example 6), respectively, except that prepared a solid electrolyte in the same manner as in 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 prepared. Li ₂ S, P ₂ S ₅ and LiCl in an Ar atmosphere glove box were taken according to a 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 obtained. After P ₂ S ₅ was completely dissolved in EDA, Li ₂ S and LiCl were added. The mixture was stirred at a speed of 800 rpm at 25° C. for 30 minutes to become a clear solution. Thereafter, 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 in Example 13, except that the solvent was changed to propylenediamine.

Example 16

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

Example 17

A solid electrolyte was obtained in the same manner as in 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.

Experimental example

(1) X-ray diffraction (XRD) measurement

)이 있는 Rigaku-Ultima(IV) X-선 회절계를 사용하여 실시예 및 비교예의 고체 전해질의 구조를 분석하였다. Cu Ka radiation at a scan rate of 2 °C/min (1.5418

) with a Rigaku-Ultima (IV) X-ray diffractometer was used to analyze the structures of the solid electrolytes of Examples and Comparative Examples.

The X-ray diffraction measurement results are shown in FIGS. 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 FIG. 3 , Examples 7 and 8 showed crystal structures 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 slightly had a crystal structure of Li ₇ PS ₆ . In addition, Example 11 showed the crystal structure of Li ₆ PS ₅ Cl, and Examples 12 to 14 were aragiodite of Li _5.7 PS _4.7 Cl _1.3 , Li _5.5 PS _4.5 Cl _1.5 , Li _5.4 PS _4.4 Cl _1.6 , respectively. It had a crystal structure.

6 shows the XRD spectra of Examples 18 to 20 and Comparative Examples, Examples 18 to 10 and Comparative Examples have an aramidite crystal structure, and a small amount of Li ₂ S, LiCl, Li ₄ P ₂ S ₆ and had the same impurity phase.

division Li ₂ S
(%) P ₂ S ₅
(%) LiCl
(%) menstruum heat treatment
Temperature (℃) shape Ion Conductivity (S/cm, 25℃) Example 1 75 25 - EDA 260 Li ₃ PS ₄ 2.85 x 10 ^-5 Example 2 75 25 - EDA 300 Li ₃ PS ₄ 4.19 x 10 ^-5 Example 3 75 25 - EDA 340 Li ₃ PS ₄ 3.82 x 10 ^-5 Example 4 70 30 - EDA 260 Li ₃ PS ₄ 4.12 x 10 ^-5 Example 5 70 30 - EDA 300 Li ₃ PS ₄ 7.27 x 10 ^-5 Example 6 70 30 - EDA 340 Li ₃ PS ₄ 6.44 x 10 ^-5 Example 7 75 25 - EDA 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 EDA 550 Li ₂ S, Li ₇ PS ₆ 1.20 x 10 ^-4 Example 9 66.66 25 8.34 EDA 550 Li ₂ S, Li ₇ PS ₆ 1.09 x 10 ^-4 Example 10 87.5 12.5 - EDA 550 Li ₂ S, Li ₇ PS ₆ 2.26 x 10 ^-6 Example 11 62.5 12.5 25 EDA 550 Li ₆ PS ₅ Cl 2.38 x 10 ^-3 Example 12 55 12.5 32.5 EDA 550 Li _5.7 PS _4.7 Cl _1.3 2.42 x 10 ^-3 Example 13 50 12.5 37.5 EDA 550 Li _5.5 PS _4.5 Cl _1.5 2.87 x 10 ^-3 Example 14 47.5 12.5 40 EDA 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 having a diameter of 10 mm and a pressure of 30 MPa was applied to form pellets. The thickness of the pellets was 0.11 to 0.12 cm. Thereafter, indium foil was attached to both sides of the pellet for measurement of ionic conductivity. Ion conductivity analysis was performed at 25° C. in a frequency range of 7 MHz to 1 Hz using an SP 300 (Biologic) instrument.

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 electrolytes having the Li ₃ PS ₄ structure of Examples 1 to 6, the higher the content of the first precursor P2s5, that is, the greater the molar ratio of the first precursor to the second precursor is 1:3 (implemented). The ionic conductivity was higher in the case of 3:7 (Examples 4 to 6) than in Examples 1 to 3).

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

Referring to FIG. 8 , the ionic conductivity of Examples 8 and 9 is much higher than that of Example 7. That is, the case in which the third precursor was not included had higher ionic conductivity, and in the case of having the same crystal structure as in Examples 7 to 9, the lower the content of the third precursor, the higher the ionic conductivity.

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

Referring to FIG. 10 , it can be seen that there are many differences in ionic conductivity when the types of solvents are different. Specifically, Example 13 using EDA showed 2.87 x 10 ^-3 (S/cm), but Examples 15 to 17 using propylenediamine and TMEDA showed lower ionic conductivity.

Referring to FIG. 11 , when a complex solvent was used, the ionic conductivity of the intermediate level was shown when a single solvent was used. The ethanol of Example 20 showed the highest ionic conductivity when combined with EDA.

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

This seems to be because the amine-based organic solvent has a substituent that well forms 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 judged that the adjustment of the order of addition to the solvent due to the difference in solubility has an effective effect on dispersibility.

(3) Measurement of particle size by SEM

The particle size of Example 13 and Comparative Example was measured using the SEM image. Referring to FIG. 12 , the particle size of Example 13 using the EDA solvent was 0.8 to 1.5 μm, but the comparative example using ethanol as the solvent showed a particle size of 0.3 to 3 μm.

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

As described above, when a uniform solid electrolyte having a small particle size is applied to a secondary battery, excellent adhesion to the electrode composite is obtained.

Claims (17)

Forming a first precursor-solvent complex by mixing a first precursor including a chalcogen element selected from the group consisting of S, Se and O in an amine-based organic solvent; and
A method of manufacturing a solid electrolyte comprising mixing a second precursor including an alkali element selected from the group consisting of Li, Na and K to the composite.
According to claim 1,
The amine-based organic solvent is a method for producing a solid electrolyte of monoamine or diamine.
According to claim 1,
The amine-based organic solvent is at least one selected from the group consisting of ethylenediamine, propylenediamine and trimethylenediamine.
According to claim 1,
The method of manufacturing a solid electrolyte wherein the first precursor further comprises one element selected from the group consisting of P, Si, Al, B, Ge, Sn, Sb, Nb, Mo and Bi.
According to claim 1,
The method for producing a solid electrolyte wherein the second precursor is sulfide, selenide or oxide. According to claim 1,
A method for producing a solid electrolyte wherein the molar ratio of the first precursor to the second precursor is 1:2 to 1:6.
The method of claim 1,
The method of manufacturing a solid electrolyte further comprising mixing a third precursor including a halogen element selected from the group consisting of Cl, Br, I and F to the complex.
8. The method of claim 7,
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 precursor.
According to claim 1,
a drying step to remove the solvent; and
A method of manufacturing a solid electrolyte further comprising a heat treatment step.
10. The method of claim 9,
The drying step is a method of manufacturing a solid electrolyte that is dried at a temperature of 150 to 250 ℃ 3 to 7 hours.
10. The method of claim 9,
The heat treatment step is a method of manufacturing a solid electrolyte performed at 200 to 600 ℃.
A solid electrolyte prepared by using the method according to any one of claims 1 to 11.
13. The method of claim 12,
A solid electrolyte having a particle size of 0.5 to 2 um.
13. The method of claim 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.
15. The method of claim 14,
The aradite-type solid electrolyte 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 .
13. The method of claim 12,
A solid electrolyte having an ionic conductivity of 10 ^-3 S/cm or more at 25°C.
An all-solid-state battery comprising the solid electrolyte of claim 12 .

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