SULFIDE-BASED SOLID ELECTROLYTE WITH IMPROVED MOISTURE STABILITY AND IONIC CONDUCTIVITY

Abstract

A sulfide-based solid electrolyte has an argyrodite-type crystal structure which is doped with an element having an oxidation number of 4 and a transition metal having an oxidation number of 6 so as to improve moisture stability and ionic conductivity of the sulfide-based solid electrolyte.

Claims

1. A sulfide-based solid electrolyte expressed as
Li.sub.5+2x+yA.sub.xSb.sub.yB.sub.1-x-yS.sub.5-zSe.sub.zX; wherein, A is an element having an oxidation number of 4, B is a transition metal having an o tion number of 6, X is at least one selected from Cl, Br, I, and combinations thereof, 0<x<1, 0<y<1,0<x+y<1, and 0<x<5.

2. The sulfide-based solid electrolyte of claim 1, wherein the element having the oxidation number of 4 comprises one selected from the group consisting of silicon (Si), germanium (Ge), tin (Sn), and combinations thereof.

3. The sulfide-based solid electrolyte of claim 1, wherein the transition metal having the oxidation number of 6 comprises one selected from the group consisting of tungsten (W), molybdenum (Mo), and a combination thereof.

4. The sulfide-based solid electrolyte of claim 1, configured to have an argyrodite-type crystal structure.

5. The sulfide-based solid electrolyte of claim 4, wherein the element having the oxidation number of 4 and the transition metal having the oxidation number of 6 are located at 4b sites of the argyrodite-type crystal structure.

6. The sulfide-based solid electrolyte of claim 1, wherein 1-x-y configured to indicate an amount of the transition metal having the oxidation number of 6 is greater than 0 but less than 0.5.

7. The sulfide-based solid electrolyte of claim 1, wherein z is greater than 0 but less than 3.5.

8. The sulfide-based solid electrolyte of claim 1, configured to belong to a space group F-43m.

9. The sulfide-based solid electrolyte of claim 1, wherein selenium (Se) is substituted for at least some of sulfur (S).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] The above and other features of the present disclosure will now be described in detail with reference to certain exemplary embodiments thereof illustrated in the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present disclosure, and wherein:

[0024] FIG. 1 is a view illustrating a crystal structure of a sulfide-based solid electrolyte according to the present disclosure;

[0025] FIG. 2 is a view illustrating migration paths of lithium ions in a sulfide-based solid electrolyte doped with silicon (Si) using molecular dynamics simulation;

[0026] FIG. 3 is a view illustrating migration paths of lithium ions in a sulfide-based solid electrolyte doped with silicon (Si) and tungsten (W) using molecular dynamics simulation; and

[0027] FIG. 4 is a view illustrating migration paths of lithium ions in a sulfide-based solid electrolyte doped with silicon (Si) and tungsten (W) and doped with selenium (Se) as substitutes for some of sulfur (S) using molecular dynamics simulation.

[0028] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the disclosure. The specific design features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

[0029] In the figures, reference numbers refer to the same or equivalent parts of the present disclosure throughout the several figures of the drawing.

DETAILED DESCRIPTION

[0030] The above-described objects, other objects, advantages and features of the present disclosure will become apparent from the descriptions of embodiments given hereinbelow with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein and may be implemented in various different forms. The embodiments are provided to make the description of the present disclosure thorough and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the drawings, the dimensions of structures may be exaggerated compared to the actual dimensions thereof, for clarity of description. In the following description of the embodiments, terms, such as first and second, may be used to describe various elements but do not limit the elements. These terms are used only to distinguish one element from other elements. For example, a first element may be named a second element, and similarly, a second element may be named a first element, without departing from the scope and spirit of the disclosure. Singular expressions may encompass plural expressions, unless they have clearly different contextual meanings.

[0032] In the following description of the embodiments, terms, such as including,,comprising, and having, are to be interpreted as indicating the presence of characteristics, numbers, steps, operations, elements or parts stated in the description or combinations thereof, and do not exclude the presence of one or more other characteristics, numbers, steps, operations, elements, parts or combinations thereof, or possibility of adding the same. In addition, it will be understood that, when a part, such as a layer, a film, a region or a plate, is said to be on another part, the part may be located directly on the other part or other parts may be interposed between the two parts. In the same manner, it will be understood that, when a part, such as a layer, a film, a region or a plate, is said to be under another part, the part may be located directly under the other part or other parts may be interposed between the two parts.

[0033] All numbers, values and/or expressions representing amounts of components, reaction conditions, polymer compositions and blends used in the description are approximations in which various uncertainties in measurement generated when these values are obtained from essentially different things are reflected and thus it will be understood that they are modified by the term about, unless stated otherwise. In addition, it will be understood that, if a numerical range is disclosed in the description, such a range includes all continuous values from a minimum value to a maximum value of the range, unless stated otherwise. Further, if such a range refers to integers, the range includes all integers from a minimum integer to a maximum integer, unless stated otherwise.

[0034] In the following description of the embodiments, it will be understood that, when the range of a variable is stated, the variable includes all values within the stated range including stated end points of the range. For example, it will be understood that a range of 5 to 10 includes not only values of 5, 6, 7, 8, 9 and 10 but also arbitrary subranges, such as a subrange of 6 to 10, a subrange of 7 to 10, a subrange of 6 to 9, and a subrange of 7 to 9, and arbitrary values between integers which are valid within the scope of the stated range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Further, for example, it will be understood that a range of 10% to 30% includes not only all integers including values of 10%, 11%, 12%, 13%, . . . 30% but also arbitrary subranges, such as a subrange of 10% to 15%, a subrange of 12% to 18%, and a subrange of 20% to 30%, and arbitrary values between integers which are valid within the scope of the stated range, such as 10.5%, 15.5%, and 25.5%.

[0035] A great deal of research on sulfide-based solid electrolytes is underway around the world due to high lithium ion conductivity and electrochemical stability thereof. The sulfide-based solid electrolytes are classified into a crystalline type and a non-crystalline type depending on presence or absence of a crystal structure. There are a thio-LiSiCON-type crystal structure, an LGPS-type crystal structure, and an argyrodite-type crystal structure as representative examples of the crystalline type, and the non-crystalline type may have a glass structure or a glass-ceramic structure depending on a heat treatment temperature.

[0036] The argyrodite-type crystal structure is one of a solid electrolyte which has the same crystal structure as argyrodite having composition Ag.sub.8GeS.sub.6 and exhibits lithium ion conductivity. As representative examples of an electrolyte having a Li-argyrodite structure having lithium ion (Li.sup.+) conductivity used in all-solid-state batteries, Li.sub.7PS.sub.6 and Li.sub.6PS.sub.5X (X being Cl, Br, or I) are known.

[0037] FIG. 1 is a view illustrating a crystal structure of a sulfide-based solid electrolyte according to the present disclosure. The sulfide-based solid electrolyte shown in FIG. 1 may be expressed as Chemical Formula 1 below.

Li.sub.5+2x+yA.sub.xSb.sub.yB.sub.1-x-yS.sub.5-zSe.sub.zXChemical Formula 1:

[0038] In chemical formula 1, A is an element having an oxidation number of 4, B is a transition metal having an oxidation number of 6, and X is at least one selected from Cl, Br, I, and combinations thereof, 0<x<1, 0<y<1, 0<x+y<1, and 0<x<5.

[0039] The sulfide-based solid electrolyte according to the present disclosure may have an argyrodite-type crystal structure. Referring to FIG. 1, in the argyrodite-type crystal structure, sulfur (S) may form tetrahedrons AS.sub.4.sup.3-, BS.sub.4.sup.3- and SbS.sub.4.sup.3- centering around elements A and B and antimony (Sb), respectively. Here, the centers of the tetrahedrons may be located at 4b sites.

[0040] The conventional sulfide-based solid electrolyte Li.sub.6PS.sub.5X (X being Cl, Br, or I) having the argyrodite-type crystal structure includes tetrahedrons PS.sub.4.sup.3- in the crystal structure, and phosphorus (P) may be located at the centers of the tetrahedrons. Referring to this, in the present disclosure, the sites of phosphorus (P) of the conventional sulfide-based solid electrolyte Li.sub.6PS.sub.5X having the argyrodite-type crystal structure may be substitutionally doped with the elements A and B and antimony (Sb).

[0041] Here, the sulfide-based solid electrolyte according to the present disclosure may be configured such that the elements A and B and antimony (Sb) may be substituted for all phosphorus (P) of the conventional sulfide-based solid electrolyte having the composition Li.sub.6PS.sub.5X. Therefore, the sulfide-based solid electrolyte according to the present disclosure may not include phosphorus (P).

[0042] Further, referring to FIG. 1, the elements A and B and antimony (Sb) may be expressed as being located at the 4b sites of the argyrodite-type crystal structure.

[0043] According to the present disclosure, as the transition metal B having the oxidation number of 6 and a large ionic radius is substituted for the sites of phosphorus (P), a crystal lattice volume may be increased. As the crystal lattice volume is increased, activation energy with respect to migration of lithium ions in the crystal lattice may be reduced, and thereby, lithium ion conductivity may be increased.

[0044] Further, the transition metal B substituted for the sites of phosphorus (P) may induce occurrence of vacancies in the crystal lattice. Occurrence of vacancies may facilitate formation of a cubic phase, and the cubic phase has sufficient migration paths of lithium ions (Li.sup.+) and may thus facilitate 3D fast conduction. Thereby, improvement in lithium ion conductivity of the sulfide-based solid electrolyte may be promoted.

[0045] Here, 1-x-y indicating the amount of the transition metal B in the sulfide-based solid electrolyte may be greater than 0 but less than 1. Preferably, 1-x-y may be greater than 0 but less than 0.5. When 1-x-y indicating the amount of the transition metal B in the sulfide-based solid electrolyte is less than 0.5, lithium ion conductivity of the sulfide-based solid electrolyte may be further improved.

[0046] Further, the transition metal B reacts with sulfur (S) and thus forms BS.sub.2 during a process of generating H.sub.2S gas through reaction between moisture (H.sub.2O) present in the air and the sulfide-based solid electrolyte, thereby being capable of suppressing generation of toxic hydrogen sulfide gas.

[0047] In one embodiment, the element A having the oxidation number of 4 may include a group 4 element on the periodic table. Preferably, the element A may include at least one selected from the group consisting of silicon (Si), germanium (Ge), tin (Sn), and combinations thereof. Further, the transition metal B having the oxidation number of 6 may include at least one selected from the group consisting of tungsten (W), molybdenum (Mo), and a combination thereof.

[0048] z indicating the amount of selenium (Se) in the sulfide-based solid electrolyte may be greater than 0 but less than 5. Preferably, z may be greater than 0 but less than 3.5. When z indicating the amount of selenium (Se) in the sulfide-based solid electrolyte is less than 3.5, generation of H.sub.2S gas caused by hydrolysis may be further suppressed. Here, selenium (Se) may be substituted for at least some of sulfur (S).

[0049] Further, the sulfide-based solid electrolyte according to the present disclosure may belong to, for example, a cubic crystal system, and more concretely, may belong to the space group F-43m.

[0050] Hereinafter, the present disclosure will be described in more detail through the following Examples and Comparative Examples. The following Examples and Comparative Examples serve merely to exemplarily describe the present disclosure, and are not intended to limit the scope and spirit of the disclosure.

Test Example 1: Detection of Migration Paths of Lithium Ions (Lit)

[0051] Migration paths of lithium ions (Li.sup.+) in sulfide-based solid electrolytes having the argyrodite-type crystal structure were predicted using molecular dynamics simulation.

[0052] Concretely, molecular dynamics simulation of a sulfide-based solid electrolyte having composition Li.sub.6.5Si.sub.0.5Sb.sub.0.5S.sub.5I, which does not include a transition metal having an oxidation number of 6 and selenium (Se), was executed, and simulation results are shown in FIG. 2. Here, green areas indicate tetrahedrons including Si and Sb, and purple lines indicate migration paths of lithium ions (Li.sup.+).

[0053] Further, molecular dynamics simulation of a sulfide-based solid electrolyte having composition Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I, which does not include selenium (Se), was executed, and simulation results are shown in FIG. 3. Here, blue areas indicate tetrahedrons including Si, Sb, W and S, and purple lines indicate migration paths of lithium ions (Li.sup.+).

[0054] Moreover, molecular dynamics simulation of a sulfide-based solid electrolyte having composition Li.sub.6.5Si.sub.0.75W0.sub..25S.sub.4.75Se.sub.0.25I, which includes a transition metal having an oxidation number of 6 and selenium (Se) but does not include antimony (Sb), was executed, and simulation results are shown in FIG. 4. Here, blue areas indicate tetrahedrons including Si, W, Se and S, and purple lines indicate migration paths of lithium ions (Li.sup.+).

[0055] Referring to FIGS. 2 to 4, it may be confirmed that, in the sulfide-based solid electrolyte including W, which is a transition metal having an oxidation number of 6, lithium ions (Li.sup.+) more actively migrate around the tetrahedrons. Thereby, it may be predicted that the sulfide-based solid electrolyte including W has higher lithium ion conductivity.

Test Example 2: Lithium Ion Conductivities and Synthesis Possibilities of Sulfide-Based Solid Electrolytes Having Various Compositions

[0056] Lithium ion conductivities of sulfide-based solid electrolytes having various compositions, activation energies (E.sub.a) required for migration of lithium ions, and energies above hull (E.sub.hull) of the sulfide-based solid electrolytes were calculated using a molecular dynamics calculation method through machine learning, and are set forth in Table 1 below.

[0057] The energy above hull (E.sub.hull) is an index to evaluate synthesis possibility of a material, it is determined that synthesis possibility of the material is higher as the energy above hull (E.sub.hull) is closer to 0, and it is generally evaluated that it is possible to synthesize the material when the energy above hull (E.sub.hull) is 100 or less.

[0058] 80% ionic conductivity (80% IC) was calculated by Equation below.

.sub.exp.=.sub.calc.X.sub.c.sup.7.14Equation:

[0059] Here, X.sub.c indicates a degree of crystallinity, and 0.8 is substituted thereinto in the case of a 80% crystal structure. .sub.calc. indicates a calculated lithium ion conductivity, i.e., a bulk ionic conductivity (BIC).

TABLE-US-00001 TABLE 1 BIC 80% IC Category Chemical formula E.sub.a (eV) (mS/cm) (mS/cm) E.sub.hull P Li.sub.6PS.sub.5I 0.32 4.17 0.85 15 PW Li.sub.5.75P.sub.0.75W.sub.0.25SsI 0.43 0.01 2.03 10.sup.3 19 Li.sub.5..sub.5P.sub.0.5W.sub.0.5S.sub.5I 0.36 0.06 0.01 31 Li.sub.5.25P.sub.0.25W.sub.0.75S.sub.5I 0.42 0.02 4.07 10.sup.3 42 PMo Li.sub.5.75P.sub.0.75Mo.sub.0.25SsI 0.45 0.004 8.13 10.sup.4 25 Li.sub.5..sub.5P.sub.0.5Mo.sub.0.5S.sub.5I 0.46 0.005 1.02 10.sup.3 48 Li.sub.5.25P.sub.0.25Mo.sub.0.75S.sub.5I 0.47 0.004 8.13 10.sup.4 67 SiSb Li.sub.6.25Si.sub.0.25Sb.sub.0.75S.sub.5I 0.20 10.4 2.11 25 Li.sub.6.5Si.sub.0.5Sb.sub.0.5S.sub.5I 0.20 13.6 2.76 Li.sub.6.75Si.sub.0.75Sb.sub.0.25S.sub.5I 0.21 14.8 3.01 0 Sb Li.sub.6SbS.sub.5I 0.71 0.00004 8.13 10.sup.6 34 Si Li.sub.7SiS.sub.5I 0.19 47.85 9.73 SiS.sub.4S Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.25S.sub.4.75I 0.15 11.73 Single S Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.25S.sub.4.75I 0.15 5.02 4 SiSbW Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I 0.16 33.74 6.86 5 Li.sub.6Si.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5I 0.32 0.16 0.03 19 Li.sub.5.75Si.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5I 0.21 0.40 0.08 35 SbW Li.sub.5.75Sb.sub.0.75W.sub.0.25S.sub.5I 0.28 0.19 0.04 37 Li.sub.5..sub.5Sb.sub.0.5W.sub.0.5S.sub.5I 0.37 0.11 0.02 48 Li.sub.5.25Sb.sub.0.25W.sub.0.75S.sub.5I 0.35 0.14 0.03 62 SiW Li.sub.6.5Si.sub.0.75W.sub.0.25S.sub.5I 0.14 62.93 12.79 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5I 0.34 0.30 0.06 9 Li.sub.5..sub.5Si.sub.0.25W.sub.0.75S.sub.5I 0.21 0.40 0.08 33 SiSbMo Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5I 0.15 33.05 6.72 10 Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5I 0.33 0.06 0.01 47 Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5I 027 0.30 0.06 24 SbMo Li.sub.5.75Sb.sub.0.75Mo.sub.0.25S.sub.5I 0.25 0.23 0.05 46 Li.sub.5..sub.5Sb.sub.0.5Mo.sub.0.5S.sub.5I 0.20 0.46 0.09 65 Li.sub.5.25Sb.sub.0.25Mo.sub.0.75S.sub.5I 0.43 0.016 3.25 10.sup.3 87 SiMo Li.sub.6.5Si.sub.0.75Mo.sub.0.25S.sub.5I 0.15 52.14 10.60 3 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5I 0.28 1.03 0.21 21 Li.sub.5..sub.5Si.sub.0.25Mo.sub.0.75S.sub.5I 0.24 1.25 0.25 57 GeSbW Li.sub.6.25Ge.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I 0.17 17.78 3.61 30 Li.sub.6Ge.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5I 0.36 0.06 0.01 31 Li.sub.5.75Ge.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5I 0.20 1.27 0.26 44 GeW Li.sub.6.5Ge.sub.0.75W.sub.0.25S.sub.5I 0.15 51.98 10.57 35 Li.sub.6Ge.sub.0.5W.sub.0.5S.sub.5I 0.22 2.22 0.45 33 GeMo Li.sub.6.5Ge.sub.0.75Mo.sub.0.25S.sub.5I 0.16 27.14 5.52 43 Li.sub.6Ge.sub.0.5Mo.sub.0.5S.sub.5I 0.18 5.5 1.12 49 GeSbMo Li.sub.6.25Ge.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5I 0.17 16.35 3.32 37 Li.sub.6Ge.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5I 0.29 0.21 0.043 39 Li.sub.5.75Ge.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5I 0.15 0.86 0.17 60

[0060] In general, it may be determined that, when 80% ionic conductivity of a solid electrolyte is 1 mS/cm or more, there is a possibility of commercialization of the solid electrolyte. Referring to Table 1, the bulk ionic conductivities of sulfide-based solid electrolytes having phosphorus (P) were calculated to be low.

Test Example 3: Hydrolysis Reactions and Hydrogen Sulfide Gas Generation Energies of Sulfide-Based Solid Electrolytes Having Various Compositions

[0061] In order to evaluate moisture stabilities of sulfide-based solid electrolytes according to the present disclosure, hydrogen sulfide gas generation energies of the sulfide-based solid electrolytes were calculated using Density Functional Theory (DFT). A calculation process is as follows. [0062] 1). A pseudo-binary reaction formula to the composition C of products formed as the result of a reaction between a solid electrolyte SE to be calculated and H.sub.2O was designed.

C.sub.products(SE,H.sub.2O,x)=x.Math.C(SE)+(1x)C(H.sub.2O)Reaction Formula 1: [0063] 2). Reaction energy for such a formula was calculated as below.

E.sub.reaction(SE,H.sub.2O,x)=E.sub.eq(C.sub.products(SE,H.sub.2O,x))E(C.sub.products(SE,H.sub.2O,x))Reaction Formula 2:

[0064] Here, eq indicates a phase equilibria state among the products acquired from the reaction formula (1). [0065] 3). Reaction energies E.sub.reaction of x were calculated by substituting values of x in the range of 0<x<1 into the above formula, and reaction with the value of x having the lowest reaction energy was determined as a reaction formula between the solid electrolyte SE to be calculated and H.sub.2O. [0066] 4). The reaction formula was normalized with respect to H.sub.2S so as to compare the reaction energies of various solid electrolytes SE. [0067] 5). Hydrogen sulfide gas generation energy E.sub.g was finally acquired by dividing the reaction energy by a conversion factor, acquired in consideration of a conversion rate indicating participation of sulfur (S) included in the solid electrolyte SE, which is a reactant, in hydrogen sulfide gas generation.

[0068] The hydrogen sulfide gas generation energies E.sub.g of the solid electrolytes SE and the reaction formulas used to calculate the hydrogen sulfide gas generation energies E.sub.g are set forth in Table 2 below.

TABLE-US-00002 TABLE 2 Eg Category Chemical formula Reaction formula (eV) Orig Li.sub.6PS.sub.5Cl 0.33Li.sub.6PS.sub.5Cl + 1.33H.sub.2O .fwdarw. H.sub.2S + 0.67LiHS + 0.44 0.33LiCl + 0.33Li.sub.3PO.sub.4 Li.sub.6PS.sub.5I 1.33 H.sub.2O + 0.33 Li.sub.6PS.sub.5I .fwdarw. H.sub.2S + 0.67 LiHS + 0.23 0.33 LiI + 0.33 Li.sub.3PO.sub.4 SiI Li.sub.7SiS.sub.5I H.sub.2O + 0.33 Li.sub.7SiS.sub.5I .fwdarw. H.sub.2S + 0.67 Li.sub.2S + 0.33 0.21 LiI + 0.33 Li.sub.2SiO.sub.3 SbI Li.sub.6SbS.sub.5I H.sub.2O + Li.sub.6SbS.sub.5I .fwdarw. 0.5 Li.sub.3SbS.sub.3 + 0.25 Li.sub.2SO.sub.4 + 0.08 H.sub.2S + 0.75 Li.sub.2S + 0.5 Li.sub.5SbS.sub.3I.sub.2 SiSbI Li.sub.6.25Si.sub.0.25Sb.sub.0.75S.sub.5I 0.14 Li.sub.25SiSb.sub.3S.sub.20I.sub.4 + H.sub.2O .fwdarw. 0.14 Li.sub.3SbS.sub.3 + 0.03 0.11 Li.sub.2SO.sub.4 + H.sub.2S + 0.46Li.sub.2S + 0.14 Li.sub.4SiO.sub.4 + 0.29 Li.sub.5SbS.sub.3I.sub.2 Li.sub.6.5Si.sub.0.5Sb.sub.0.5S.sub.5I 0.5 Li.sub.6.5Si.sub.0.5Sb.sub.0.5S.sub.5I + H.sub.2O .fwdarw. 0.25 Li.sub.5SbS.sub.3I.sub.2 + 0.07 H.sub.2S + 0.69 Li.sub.2S + 0.25 Li.sub.2SiO.sub.3 + 0.06Li.sub.2SO.sub.4 Li.sub.6.75Si.sub.0.75Sb.sub.0.25S.sub.5I 0.11 Li.sub.27Si.sub.3SbS.sub.20I.sub.4 + H.sub.2O .fwdarw. 0.11 Li.sub.3SbS.sub.4 + 0.16 H.sub.2S + 0.78 Li.sub.2S + 0.44 LiI + 0.33 Li.sub.2SiO.sub.3 SiSbWI Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I H.sub.2O + 0.13 Li.sub.25Si.sub.2SbWS.sub.20I.sub.4 .fwdarw. 0.063 Li.sub.2SO.sub.4 + 0.07 H.sub.2S + 0.81 Li.sub.2S + 0.25 LiI + 0.25 Li.sub.2SiO.sub.3 + 0.13 WS.sub.2 + 0.13 Li.sub.5SbS.sub.3I.sub.2 Li.sub.6Si.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5I H.sub.2O + 0.14 Li.sub.24SiSb.sub.2WS.sub.20I.sub.4 .fwdarw. 0.11 Li.sub.2SO.sub.4 + 0.02 H.sub.2S + 0.61 Li.sub.2S + 0.14 Li.sub.4SiO.sub.4 + 0.14 WS.sub.2 + 0.29 Li.sub.5SbS.sub.3I.sub.2 Li.sub.5.75Si.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5I H.sub.2O + 0.14 Li.sub.23SiSbW.sub.2S.sub.20I.sub.4 .fwdarw. 0.11 Li.sub.2SO.sub.4 + 0.02 H.sub.2S + 0.75 Li.sub.2S + 0.29 LiI + 0.14 Li.sub.4SiO.sub.4 + 0.29 WS.sub.2 + 0.14 Li.sub.5SbS.sub.3I.sub.2 SbWI Li.sub.5.75Sb.sub.0.75W.sub.0.25S.sub.5I 0.096Li.sub.23Sb.sub.3W.sub.2S.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.539 Li.sub.2S + 0.36 0.038 Sb + 0.39 LiI + 0.192 WS.sub.2 + 0.25 Li.sub.3SbO.sub.4 Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5I Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5I + H.sub.2O .fwdarw. 0.5 Li.sub.5SbS.sub.3I.sub.2 + H.sub.2S + 0.07 1.25 Li.sub.2S + 0.5 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 Li.sub.5.25Sb.sub.0.25W.sub.0.75S.sub.5I 0.25 Li.sub.21SbW.sub.3S.sub.20I.sub.4 + H.sub.2O .fwdarw. 0.25 Li.sub.5SbS.sub.3I.sub.2 + 0.06 H.sub.2S + 1.5 Li.sub.2S + 0.5 LiI + 0.75 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 SiWI Li.sub.6.5Si.sub.0.75W.sub.0.25S.sub.5I 0.1 Li.sub.26Si.sub.3WS.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.78 Li.sub.2S + 0.15 0.4 LiI + 0.3 Li.sub.2SiO.sub.3 + 0.1 WS.sub.2 + 0.025 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5I 0.5 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5I + H.sub.2O .fwdarw. H.sub.2S + 0.94 Li.sub.2S + 0.10 0.5 LiI + 0.25 Li.sub.2SiO.sub.3 + 0.25 WS.sub.2 + 0.06Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25W.sub.0.75S.sub.5I 0.14 Li.sub.22SiW.sub.3S.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.90 Li.sub.2S + 0.15 0.57 LiI + 0.14 Li.sub.4SiO.sub.4 + 0.43 WS.sub.2 + 0.11 Li.sub.2SO.sub.4 SiSbWBr Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5Br 0.143 Li.sub.25Si.sub.2SbWS.sub.20Br.sub.4 + H.sub.2O .fwdarw. 0.143 Li.sub.3SbS.sub.4 + 0.10 0.571 LiBr + H.sub.2S + 0.964 Li.sub.2S + 0.286Li.sub.2SiO.sub.3 + 0.143 WS.sub.2 + 0.04 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5Br 0.143 Li.sub.24SiSb.sub.2WS.sub.20Br.sub.4 + H.sub.2O .fwdarw. 0.286Li.sub.3SbS.sub.3 + 0.02 0.571 LiBr + H.sub.2S + 0.607 Li.sub.2S + 0.143 Li.sub.4SiO.sub.4 + 0.143 WS.sub.2 + 0.107 Li.sub.2SO.sub.4 Li.sub.5.75Si.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5Br 0.143 Li.sub.23SiSbW.sub.2S.sub.20Br.sub.4 + H.sub.2O .fwdarw. 0.143 Li.sub.3SbS.sub.3 + 0.004 0.571 LiBr + H.sub.2S + 0.75 Li.sub.2S + 0.143 Li.sub.4SiO.sub.4 + 0.286WS.sub.2 + 0.107 Li.sub.2SO.sub.4 SbWBr Li.sub.5.75Sb.sub.0.75W.sub.0.25S.sub.5Br H.sub.2O + 0.25 Li.sub.23Sb.sub.3WS.sub.20Br.sub.4 .fwdarw. 0.75 Li.sub.3SbS.sub.3 + 0.07 LiBr + H.sub.2S + Li.sub.2S + 0.25 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5Br H.sub.2O + Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5Br .fwdarw. 0.5 Li.sub.3SbS.sub.3 + LiBr + 0.06 H.sub.2S + 1.25 Li.sub.2S + 0.5 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 Li.sub.5.25Sb.sub.0.25W.sub.0.75S.sub.5Br H.sub.2O + 0.25 Li.sub.21SbW.sub.3S.sub.20Br.sub.4 .fwdarw. 0.25 Li.sub.3SbS.sub.3 + 0.04 LiBr + H.sub.2S + 1.5 Li.sub.2S + 0.75 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 SiWBr Li.sub.6.5Si.sub.0.75W.sub.0.25S.sub.5Br H.sub.2O + 0.1 Li.sub.26Si.sub.3WS.sub.20Br.sub.4 .fwdarw. 0.4 LiBr + H.sub.2S + 0.15 0.78 Li.sub.2S + 0.3 Li.sub.2SiO.sub.3 + 0.1 WS.sub.2 + 0.03 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5Br H.sub.2O + 0.5 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5Br .fwdarw. 0.5 LiBr + H.sub.2S + 0.10 0.94 Li.sub.2S + 0.25 Li.sub.2SiO.sub.3 + 0.25 WS.sub.2 + 0.06Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25W.sub.0.75S.sub.5Br H.sub.2O + 0.143 Li.sub.22SiW.sub.3S.sub.20Br.sub.4 .fwdarw. 0.571 LiBr + 0.01 H.sub.2S + 0.893 Li.sub.2S + 0.143 Li.sub.4SiO.sub.4 + 0.429 WS.sub.2 + 0.107 Li.sub.2SO.sub.4 SiSbWCl Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5Cl H.sub.2O + 0.14 Li.sub.25Si.sub.2SbWS.sub.20Cl.sub.4 .fwdarw. 0.14 Li.sub.3SbS.sub.4 + 0.10 H.sub.2S + 0.96Li.sub.2S + 0.571 LiCl + 0.29 Li.sub.2SiO.sub.3 + 0.14 WS.sub.2 + 0.036Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5Cl H.sub.2O + 0.14 Li.sub.24SiSb.sub.2WS.sub.20Cl.sub.4 .fwdarw. 0.29 Li.sub.3SbS.sub.3 + 0.02 H.sub.2S + 0.61 Li.sub.2S + 0.57 LiCl + 0.14 Li.sub.4SiO.sub.4 + 0.14 WS.sub.2 + 0.11 Li.sub.2SO.sub.4 Li.sub.5.75Si.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5Cl H.sub.2O + 0.14 Li.sub.23SiSbW.sub.2S.sub.20Cl.sub.4 .fwdarw. 0.143 Li.sub.3SbS.sub.3 + 0.004 H.sub.2S + 0.75 Li.sub.2S + 0.571 LiCl + 0.143 Li.sub.4SiO.sub.4 + 0.286WS.sub.2 + 0.107 Li.sub.2SO.sub.4 SbWCl Li.sub.5.75Sb.sub.0.75W.sub.0.25S.sub.5Cl 0.25 Li.sub.23Sb.sub.3WS.sub.20Cl.sub.4 + H.sub.2O .fwdarw. 0.75 Li.sub.3SbS.sub.3 + 0.07 H.sub.2S + Li.sub.2S + LiCl + 0.25 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5Cl Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5Cl + H.sub.2O .fwdarw. 0.5 Li.sub.3SbS.sub.3 + H.sub.2S + 0.06 1.25 Li.sub.2S + LiCl + 0.5 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 Li.sub.5.25Sb.sub.0.25W.sub.0.75S.sub.5Cl 0.25 Li.sub.21SbW.sub.3S.sub.20Cl.sub.4 + H.sub.2O .fwdarw. 0.25 Li.sub.3SbS.sub.3 + 0.04 H.sub.2S + 1.5 Li.sub.2S + LiCl + 0.75 WS.sub.2 + 0.25 Li.sub.2SO.sub.4 SiWCl Li.sub.6.5Si.sub.0.75W.sub.0.25S.sub.5Cl H.sub.2O + 0.1 Li.sub.26Si.sub.3WS.sub.20Cl.sub.4 .fwdarw. H.sub.2S + 0.78 Li.sub.2S + 0.15 0.4 LiCl + 0.3 Li.sub.2SiO.sub.3 + 0.1 WS.sub.2 + 0.03 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5Cl H.sub.2O + 0.5 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5Cl .fwdarw. H.sub.2S + 0.94 Li.sub.2S + 0.10 0.5 LiCl + 0.25 Li.sub.2SiO.sub.3 + 0.25 WS.sub.2 + 0.06Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25W.sub.0.75S.sub.5Cl H.sub.2O + 0.14 Li.sub.22SiW.sub.3S.sub.20Cl.sub.4 .fwdarw. H.sub.2S + 0.89 Li.sub.2S + 0.01 0.57 LiCl + 0.14 Li.sub.4SiO.sub.4 + 0.43 WS.sub.2 + 0.11 Li.sub.2SO.sub.4 SiSbMoI Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5I H.sub.2O + 0.13 Li.sub.25Si.sub.2SbMoS.sub.20I.sub.4 .fwdarw. 0.063 Li.sub.2SO.sub.4 + 0.07 H.sub.2S + 0.81 Li.sub.2S + 0.25 LiI + 0.25 Li.sub.2SiO.sub.3 + 0.13 MoS.sub.2 + 0.13 Li.sub.5SbS.sub.3I.sub.2 Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5I H.sub.2O + 0.14 Li.sub.24SiSb.sub.2MoS.sub.20I.sub.4 .fwdarw. 0.11 Li.sub.2SO.sub.4 + 0.21 H.sub.2S + 0.61 Li.sub.2S + 0.14 Li.sub.4SiO.sub.4 + 0.14 MoS.sub.2 + 0.29 Li.sub.5SbS.sub.3I.sub.2 Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5I H.sub.2O + 0.14 Li.sub.23SiSbMo.sub.2S.sub.20I.sub.4 .fwdarw. 0.11 Li.sub.2SO.sub.4 + 0.02 H.sub.2S + 0.75 Li.sub.2S + 0.29 LiI + 0.14 Li.sub.4SiO.sub.4 + 0.29 MoS.sub.2 + 0.14 Li.sub.5SbS.sub.3I.sub.2 SbMoI Li.sub.5.75Sb.sub.0.75Mo.sub.0.25S.sub.5I 0.077 Li.sub.23Sb.sub.3MoS.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.37 Li.sub.2S + 0.42 0.31 LiI + 0.077 MoS.sub.2 + 0.019 Li.sub.2SO.sub.4 + 0.23 Li.sub.3SbO.sub.4 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5I 0.4 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5Cl + H.sub.2O .fwdarw. H.sub.2S + 0.55 0.28 Li.sub.2S + 0.4 LiCl + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 + 0.2 Li.sub.3SbO.sub.4 Li.sub.5.25Sb.sub.0.25Mo.sub.0.75S.sub.5I 0.14 Li.sub.21SbMo.sub.3S.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.89 Li.sub.2S + 0.18 0.571 LiI + 0.43 MoS.sub.2 + 0.11 Li.sub.2SO.sub.4 + 0.14 Li.sub.3SbO.sub.4 SiMoI Li.sub.6.5Si.sub.0.75Mo.sub.0.25S.sub.5I 0.1 Li.sub.26Si.sub.3MoS.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.775 Li.sub.2S + 0.15 0.4 LiI + 0.3 Li.sub.2SiO.sub.3 + 0.1 MoS.sub.2 + 0.025 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5I H.sub.2O + 0.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5Cl .fwdarw. H.sub.2S + 0.55 Li.sub.2S + 0.05 0.4 LiCl + 0.2 Li.sub.4SiO.sub.4 + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25Mo.sub.0.75S.sub.5I 0.143 Li.sub.22SiMo.sub.3S.sub.20I.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.893 0.01 Li.sub.2S + 0.571 LiI + 0.143 Li.sub.4SiO.sub.4 + 0.429 MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 SiSbMoBr Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5Br 0.5 Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5Br + H.sub.2O .fwdarw. 0.0625 0.08 Li.sub.2SO.sub.4 + 0.125 Li.sub.3SbS.sub.3 + 0.125 MoS.sub.2 + 0.5 LiBr + H.sub.2S + 0.25 Li.sub.2SiO.sub.3 + 0.8125 Li.sub.2S Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5Br 0.5714 Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5Br + H.sub.2O .fwdarw. 0.1071 0.02 Li.sub.2SO.sub.4 + 0.2857 Li.sub.3SbS.sub.3 + 0.1429 MoS.sub.2 + 0.5714 LiBr + H.sub.2S + 0.1429 Li.sub.4SiO.sub.4 + 0.6071 Li.sub.2S Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5Br 0.5714 Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5Br + H.sub.2O .fwdarw. 0.00 0.1071 Li.sub.2SO.sub.4 + 0.1429 Li.sub.3SbS.sub.3 + 0.2857 MoS.sub.2 + 0.5714 LiBr + H.sub.2S + 0.1429 Li.sub.4SiO.sub.4 + 0.75 Li.sub.2S SbMoBr Li.sub.5.75Sb.sub.0.75Mo.sub.0.25S.sub.5Br H.sub.2O + 0.0769 Li.sub.23Sb.sub.3MoS.sub.20Br.sub.4 .fwdarw. 0.308 LiBr + 0.41 H.sub.2S + 0.365 Li.sub.2S + 0.077 MoS.sub.2 + 0.019 Li.sub.2SO.sub.4 + 0.231 Li.sub.3SbO.sub.4 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5Br H.sub.2O + 0.4 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5Br .fwdarw. 0.4 LiBr + H.sub.2S + 0.28 0.55 Li.sub.2S + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 + 0.2 Li.sub.3SbO.sub.4 Li.sub.5.25Sb.sub.0.25Mo.sub.0.75S.sub.5Br H.sub.2O + 0.143 Li.sub.21SbMo.sub.3S.sub.20Br.sub.4 .fwdarw. 0.571 LiBr + 0.15 H.sub.2S + 0.893 Li.sub.2S + 0.429 MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 + 0.143 Li.sub.3SbO.sub.4 SiMoBr Li.sub.6.5Si.sub.0.75Mo.sub.0.25S.sub.5Br H.sub.2O + 0.1 Li.sub.26Si.sub.3MoS.sub.20Br.sub.4 .fwdarw. 0.4 LiBr + H.sub.2S + 0.15 0.78 Li.sub.2S + 0.3 Li.sub.2SiO.sub.3 + 0.1 MoS.sub.2 + 0.03 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5Br H.sub.2O + 0.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5Br .fwdarw. 0.4 LiBr + H.sub.2S + 0.05 0.55 Li.sub.2S + 0.2 Li.sub.4SiO.sub.4 + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25Mo.sub.0.75S.sub.5Br H.sub.2O + 0.143 Li.sub.22SiMo.sub.3S.sub.20Br.sub.4 .fwdarw. 0.571 LiBr + 0.014 H.sub.2S + 0.893 Li.sub.2S + 0.143 Li.sub.4SiO.sub.4 + 0.429 MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 SiSbMoCl Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5Cl H.sub.2O + 0.1.sub.25 Li.sub.25Si.sub.2SbMoS.sub.20Cl.sub.4 .fwdarw. 0.125 0.08 Li.sub.3SbS.sub.3 + H.sub.2S + 0.813 Li.sub.2S + 0.5 LiCl + 0.25 Li.sub.2SiO.sub.3 + 0.125 MoS.sub.2 + 0.063 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5Cl H.sub.2O + 0.143 Li.sub.24SiSb.sub.2MoS.sub.20Cl.sub.4 .fwdarw. 0.286Li.sub.3SbS.sub.3 + 0.02 H.sub.2S + 0.607 Li.sub.2S + 0.571 LiCl + 0.143 Li.sub.4SiO.sub.4 + 0.143 MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5Cl H.sub.2O + 0.143 Li.sub.23SiSbMo.sub.2S.sub.20Cl.sub.4 .fwdarw. 0.143 0.004 Li.sub.3SbS.sub.3 + H.sub.2S + 0.75 Li.sub.2S + 0.571 LiCl + 0.143 Li.sub.4SiO.sub.4 + 0.286MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 SbMoCl Li.sub.5.75Sb.sub.0.75Mo.sub.0.25S.sub.5Cl 0.077 Li.sub.23Sb.sub.3MoS.sub.20Cl.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.37 0.41 Li.sub.2S + 0.308 LiCl + 0.077 MoS.sub.2 + 0.019 Li.sub.2SO.sub.4 + 0.23 Li.sub.3SbO.sub.4 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5Cl 0.4 Li.sub.5..sub.5Sb.sub.0.5Mo.sub.0.5S.sub.5Cl + H.sub.2O .fwdarw. H.sub.2S + 0.55 0.28 Li.sub.2S + 0.4 LiCl + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 + 0.2 Li.sub.3SbO.sub.4 Li.sub.5.25Sb.sub.0.25Mo.sub.0.75S.sub.5Cl 0.14 Li.sub.21SbMo.sub.3S.sub.20Cl.sub.4 + H.sub.2O .fwdarw. H.sub.2S + 0.89 Li.sub.2S + 0.15 0.57 LiCl + 0.43 MoS.sub.2 + 0.107 Li.sub.2SO.sub.4 + 0.14 Li.sub.3SbO.sub.4 SiMoCl Li.sub.6.5Si.sub.0.75Mo.sub.0.25S.sub.5Cl H.sub.2O + 0.1 Li.sub.26Si.sub.3MoS.sub.20Cl.sub.4 .fwdarw. H.sub.2S + 0.78 Li.sub.2S + 0.15 0.4 LiCl + 0.3 Li.sub.2SiO.sub.3 + 0.1 MoS.sub.2 + 0.03 Li.sub.2SO.sub.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5Cl H.sub.2O + 0.4 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5Cl .fwdarw. H.sub.2S + 0.55 Li.sub.2S + 0.05 0.4 LiCl + 0.2 Li.sub.4SiO.sub.4 + 0.2 MoS.sub.2 + 0.05 Li.sub.2SO.sub.4 Li.sub.5.5Si.sub.0.25Mo.sub.0.75S.sub.5Cl H.sub.2O + 0.143 Li.sub.22SiMo.sub.3S.sub.20Cl.sub.4 .fwdarw. H.sub.2S + 0.89 0.014 Li.sub.2S + 0.57 LiCl + 0.143 Li.sub.4SiO.sub.4 + 0.43 MoS.sub.2 + 0.11 Li.sub.2SO.sub.4 Se Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.5S.sub.4.5I 0.44 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.0.5S.sub.4..sub.5I.sub.1 + H.sub.2O .fwdarw. 0.11 0.18 Li.sub.2Se + 0.11 Se + 0.44 LiI + H.sub.2S + 0.33 Li.sub.2SiO.sub.3 + 0.78 Li.sub.2S + 0.11 WS.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25SeS.sub.4I 0.44 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.1S.sub.4I.sub.1 + H.sub.2O .fwdarw. 0.33 Li.sub.2Se + 0.2 0.11 Se + 0.44 LiI + H.sub.2S + 0.33 Li.sub.2SiO.sub.3 + 0.56 Li.sub.2S + 0.11 WS.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se1..sub.25S.sub.3.75I 0.44 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.1.25S.sub.3.75I.sub.1 + H.sub.2O .fwdarw. 0.44 0.21 Li.sub.2Se + 0.11 Se + 0.44 LiI + H.sub.2S + 0.33 Li.sub.2SiO.sub.3 + 0.44 Li.sub.2S + 0.11 WS.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.1.75S.sub.3.25I 4 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.1.75S.sub.3..sub.25I.sub.1 + 6 H.sub.2O .fwdarw. 6 Li.sub.2Se + 0.28 3 SiO.sub.2 + Se + 4 LiI + WS.sub.2 + H.sub.2S + 10 LiHS Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2S.sub.3I Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.2S.sub.3I.sub.1 + 3 H.sub.2O .fwdarw. 3.5 Li.sub.2Se + 1.5 0.29 SiO.sub.2 + 0.5 Se + 2 LiI + 0.5 WS.sub.2 + H.sub.2S + 4 LiHS Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.25S.sub.2.75I 1.33 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.2..sub.25S.sub.2.75I.sub.1 + 2 H.sub.2O .fwdarw. 0.31 2.667 Li.sub.2Se + SiO.sub.2 + 0.33 Se + 1.33 LiI + 0.33 WS.sub.2 + H.sub.2S + 2 LiHS Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.5S.sub.2.5I Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.2..sub.5S.sub.2..sub.5I.sub.1 + 1.5 H.sub.2O .fwdarw. 2.25 0.32 Li.sub.2Se + 0.75 SiO.sub.2 + 0.25 Se + LiI + 0.25 WS.sub.2 + H.sub.2S + LiHS Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.75S.sub.2.25I 0.8 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.2.75S.sub.2..sub.25I.sub.1 + 1.2 H.sub.2O .fwdarw. 2 0.34 Li.sub.2Se + 0.6 SiO.sub.2 + 0.2 Se + 0.8 LiI + 0.2 WS.sub.2 + H.sub.2S + 0.4 LiHS Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3S.sub.2I 0.6667 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.3S.sub.2I.sub.1 + H.sub.2O .fwdarw. 1.8 0.37 Li.sub.2Se + 0.5 SiO.sub.2 + 0.17 Se + 0.67 LiI + H.sub.2S + 0.167 WS.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.25S.sub.1.75I 0.67 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.3..sub.25S.sub.1.75I.sub.1 + H.sub.2O .fwdarw. 1.83 0.41 Li.sub.2Se + 0.5 SiO.sub.2 + 0.17 Se + 0.08 WSe.sub.2 + 0.67 LiI + H.sub.2S + 0.08 WS.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.5S.sub.1.5I 0.67 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.3..sub.5S.sub.1.5I.sub.1 + H.sub.2O .fwdarw. 1.83 0.47 Li.sub.2Se + 0.5 SiO.sub.2 + 0.167 Se + 0.17 WSe.sub.2 + 0.67 LiI + H.sub.2S Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.75S1..sub.25I 1.33 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.3.75S.sub.1.25I.sub.1 + 2 H.sub.2O .fwdarw. 3.67 0.52 Li.sub.2Se + 0.67 H.sub.3S + SiO.sub.2 + 0.67 Se + 0.33 WSe.sub.2 + 1.33 LiI + H.sub.2S Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4SI Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.4S.sub.1I.sub.1 + H.sub.2O .fwdarw. 2.75 Li.sub.2Se + 0.46 H.sub.2S + 0.5 SiO.sub.2 + 0.25 Se + 0.25 WSe.sub.2 + LiI + 0.25 SiSe.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.25S.sub.0.75I 1.33Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.4..sub.25S.sub.0.75I.sub.1 + H.sub.2O .fwdarw. 3.67 0.45 Li.sub.2Se + H.sub.2S + 0.5 SiO.sub.2 + 0.33 Se + 0.33 WSe.sub.2 + 1.33 LiI + 0.5 SiSe.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.5S.sub.0.5I 2 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.4..sub.5S.sub.0.5I.sub.1 + H.sub.2O .fwdarw. 5.5 Li.sub.2Se + 0.43 H.sub.2S + 0.5 SiO.sub.2 + 0.5 Se + 0.5 WSe.sub.2 + 2 LiI + SiSe.sub.2 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.75S.sub.0.25I 4 Li.sub.6..sub.5Si.sub.0.75W.sub.0.25Se.sub.4..sub.75S.sub.0.25I.sub.1 + H.sub.2O .fwdarw. 11 Li.sub.2Se + 0.43 H.sub.2S + 0.5 SiO.sub.2 + Se + WSe.sub.2 + 4 LiI + 2.5 SiSe.sub.2

[0069] As the gas generation energy decreases, generation of hydrogen sulfide gas is easier in hydrolysis of the sulfide-based solid electrolyte. That is, as the gas generation energy increases, generation of hydrogen sulfide gas may be suppressed and moisture stability may be increased.

[0070] Referring to Table 2, the gas generation energies of the sulfide-based solid electrolytes doped with an element having an oxidation number of 4 or a transition metal having an oxidation number of 6 were calculated to be higher. It is predicted that tungsten (W) and molybdenum (Mo) reacted with sulfur (S) to form WS.sub.2 and MoS.sub.2, and thereby, generation of H.sub.2S gas was suppressed.

Test Example 4: Interfacial Energies Between Sulfide-Based Solid Electrolytes Having Various Compositions and Respective Elements of Cathode

[0071] Interfacial reaction energies between a cathode active material and a coating composition thereof generally included in a cathode and sulfide-based solid electrolytes having various compositions were calculated through computer simulation. A detailed calculation method is as follows.

xC.sup.a+(1x)C.sup.b.fwdarw.C.sub.equilEquation eq1:

[0072] (C.sup.a and C.sup.b=compositions of two phases in contact, C.sub.equil=low phase equilibrium energy, and 0<x<1)

E[C.sup.a,C.sup.b]=min{E.sub.pd[xC.sup.a+(1x)C.sup.b]xE[C.sup.a](1x)E[C.sup.b]}Equation eq2:

[0073] (E.sub.pd: a combination of reaction products having the lowest energy in xC.sup.a+(1x)C.sup.b)

[0074] Related energy calculated using DFT may be acquired from the database of the materials project, and a function to find the minimum value is in the materials project.

[0075] Equation eq3 was derived using Equation eq2 in order to describe a phenomenon in a battery cell.

.sub.pd[C,.sub.Li]=min{E.sub.pd[c+.sub.Li]n.sub.Li[c].sub.Li}Equation eq3:

[0076] .sub.pd[c, .sub.Li] indicates the composition c having the lowest energy in .sub.Li, in the same manner as E.sub.pd. Here, lithium potential determined from a calculated average cathode voltage is used.

[0077] In Equation eq4, electric potential on the interface is changed by causing the electrolyte to be in equilibrium with the external lithium potential and to react with the cathode, and interfacial stability is determined by a .sub.Li function. The magnitude of determines thermodynamic stability.

.sub.pd[c.sub.cathode,c.sub.electrode,.sub.Li]=min{.sub.pd[X.sup.c.sup.cathode+(1X).sup.c.sup.cathode,.sub.Li]X.sup.([c.sub.cathode,.sub.Li](1X).sup.c.sup.cathode,.sub.Li}Equation eq4:

[0078] Finally, interfacial reaction energy between the electrolyte and the cathode may be confirmed using .

[0079] The interfacial reaction energies of the sulfide-based solid electrolytes having various compositions were calculated through the above process, and are set forth in Table 3 below.

TABLE-US-00003 TABLE 3 Cathode active material and coating material (meV/atom) Chemical formula NCM811 Li.sub.2ZrO.sub.3 NiNbO.sub.3 Si C.sub.6 LiF LiI Li.sub.6PS.sub.5Cl 0.424 0.091 0.108 0.087 0.000002 0.000002 0.000002 Li.sub.6.25Si.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I 0.38 0.065 0.064 0.059 0.000 0.000 0.000 Li.sub.6Si.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5I 0.37 0.042 0.036 0.090 0.000 0.000 0.000 Li.sub.5.75Si.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5I 0.37 0.043 0.036 0.086 0.000 0.000 0.000 Li.sub.5.75Sb.sub.0.75W.sub.0.25S.sub.5I 0.36 0.013 0.010 0.119 0.000 0.000 0.000 Li.sub.5.5Sb.sub.0.5W.sub.0.5S.sub.5I 0.36 0.015 0.011 0.115 0.000 0.000 0.000 Li.sub.5.25Sb.sub.0.25W.sub.0.75S.sub.5I 0.36 0.015 0.012 0.112 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25S.sub.5I 0.39 0.082 0.086 0.033 0.003 0.000 0.000 Li.sub.6Si.sub.0.5W.sub.0.5S.sub.5I 0.38 0.068 0.066 0.064 0.007 0.000 0.000 Li.sub.5.5Si.sub.0.25W.sub.0.75S.sub.5I 0.37 0.051 0.042 0.093 0.011 0.000 0.000 Li.sub.6.25Si.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5I 0.37 0.065 0.064 0.065 0.000 0.000 0.000 Li.sub.6Si.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5I 0.36 0.042 0.036 0.095 0.000 0.000 0.000 Li.sub.5.75Si.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5I 0.36 0.043 0.036 0.097 0.000 0.000 0.000 Li.sub.5.75Sb.sub.0.75Mo.sub.0.25S.sub.5I 0.36 0.013 0.01 0.125 0.000 0.000 0.000 Li.sub.5.5Sb.sub.0.5Mo.sub.0.5S.sub.5I 0.35 0.015 0.011 0.126 0.000 0.000 0.000 Li.sub.5.25Sb.sub.0.25Mo.sub.0.75S.sub.5I 0.35 0.015 0.012 0.127 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75Mo.sub.0.25S.sub.5I 0.38 0.082 0.086 0.038 0.003 0.000 0.000 Li.sub.6Si.sub.0.5Mo.sub.0.5S.sub.5I 0.37 0.068 0.066 0.074 0.007 0.000 0.000 Li.sub.5.5Si.sub.0.25Mo.sub.0.75S.sub.5I 0.36 0.051 0.042 0.109 0.011 0.000 0.000 Li.sub.6.5Ge.sub.0.75W.sub.0.25S.sub.5I 0.355 0.008 0.01 0.056 0.003 0.000 0.000 Li.sub.6Ge.sub.0.5W.sub.0.5S.sub.5I 0.358 0.016 0.013 0.078 0.007 0.000 0.000 Li.sub.5.5Ge.sub.0.25W.sub.0.75S.sub.5I 0.36 0.022 0.016 0.1 0.011 0.000 0.000 Li.sub.6.25Ge.sub.0.5Sb.sub.0.25W.sub.0.25S.sub.5I 0.356 0.008 0.009 0.074 0.000 0.000 0.000 Li.sub.6Ge.sub.0.25Sb.sub.0.5W.sub.0.25S.sub.5I 0.357 0.011 0.01 0.096 0.000 0.000 0.000 Li.sub.5.75Ge.sub.0.25Sb.sub.0.25W.sub.0.5S.sub.5I 0.358 0.012 0.011 0.093 0.000 0.000 0.000 Li.sub.6.5Ge.sub.0.75Mo.sub.0.25S.sub.5I 0.352 0.008 0.01 0.061 0.003 0.000 0.000 Li.sub.6Ge.sub.0.5Mo.sub.0.5S.sub.5I 0.352 0.016 0.013 0.088 0.007 0.000 0.000 Li.sub.5.5Ge.sub.0.25Mo.sub.0.75S.sub.5I 0.352 0.022 0.016 0.0115 0.011 0.000 0.000 Li.sub.6.25Ge.sub.0.5Sb.sub.0.25Mo.sub.0.25S.sub.5I 0.353 0.008 0.009 0.079 0.000 0.000 0.000 Li.sub.6Ge.sub.0.25Sb.sub.0.5Mo.sub.0.25S.sub.5I 0.354 0.011 0.01 0.102 0.000 0.000 0.000 Li.sub.5.75Ge.sub.0.25Sb.sub.0.25Mo.sub.0.5S.sub.5I 0.352 0.012 0.011 0.103 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.25S.sub.4.75I 0.384 0.08 0.089 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.25S.sub.4.75I 0.384 0.08 0.089 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.5S.sub.4.5I 0.384 0.08 0.092 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.0.75S.sub.4.25I 0.384 0.08 0.096 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25SeS.sub.4I 0.383 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.1.25S.sub.3.75I 0.383 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.1.5S.sub.3.5I 0.383 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.1.75S.sub.3.25I 0.382 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2S.sub.3I 0.382 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.25S.sub.2.75I 0.381 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.5S.sub.2.5I 0.381 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.2.75S.sub.2.25I 0.381 0.08 0.098 0.024 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3S.sub.2I 0.38 0.08 0.098 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.25S.sub.1.75I 0.38 0.081 0.099 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.5S.sub.1.5I 0.38 0.082 0.1 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.3.75S.sub.1.25I 0.38 0.083 0.1 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4SI 0.378 0.084 0.099 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.25S.sub.0.75I 0.376 0.085 0.099 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.5S.sub.0.5I 0.371 0.086 0.097 0.022 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.4.75S.sub.0.25I 0.365 0.086 0.096 0.023 0.000 0.000 0.000 Li.sub.6.5Si.sub.0.75W.sub.0.25Se.sub.5I 0.355 0.086 0.096 0.024 0.000 0.000 0.000

[0080] Referring to Table 3, it may be confirmed that the interfacial reaction energies of the sulfide-based solid electrolytes according to the present disclosure are higher than the conventional argyrodite-type sulfide-based solid electrolyte (Li.sub.6PS.sub.5Cl). Thereby, it is predicted that, it is difficult to cause decomposition reaction in the sulfide-based solid electrolytes according to the present disclosure, and thus, stability on the interfaces of the sulfide-based solid electrolytes according to the present disclosure may be increased.

[0081] As is apparent from the above description, the present disclosure provides a sulfide-based solid electrolyte having an argyrodite-type crystal structure which includes an element having an oxidation number of 4 and a transition metal having an oxidation number of 6 so as to improve both ionic conductivity and moisture stability of the sulfide-based solid electrolyte in a balanced way.

[0082] The disclosure has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the appended claims and their equivalents.