KR102651625B1 - Lithium secondary battery solid electrolytes and method of preparing the same - Google Patents

Abstract

A lithium secondary battery solid electrolyte and a method for manufacturing the same are provided. Specifically, the lithium secondary battery solid electrolyte is a thio-LISICON II analog phase formed from an amorphous binder of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ). ) includes glass ceramics with Accordingly, the ionic conductivity and electrochemical stability of the solid electrolyte of a lithium secondary battery can be improved.

Description

Lithium secondary battery solid electrolyte and manufacturing method thereof {LITHIUM SECONDARY BATTERY SOLID ELECTROLYTES AND METHOD OF PREPARING THE SAME}

The present invention relates to a lithium secondary battery solid electrolyte and a manufacturing method thereof, and more specifically, to a lithium secondary battery solid electrolyte containing sulfide-based crystallized glass and a manufacturing method thereof.

Secondary batteries are used to supply power to small mobile electronic devices, electric vehicles, hybrid vehicles, etc. Recently, lithium secondary batteries using lithium ions have been widely studied and used as secondary batteries.

Currently commercialized lithium secondary batteries mainly contain flammable organic liquids as electrolyte materials, which poses a risk of explosion and leakage. To solve this problem, attempts are being made to develop lithium secondary batteries containing an all-solid-state electrolyte. Lithium secondary batteries containing a solid electrolyte are not only safer than those containing an organic liquid electrolyte, but also have the advantage of being stable and not decomposed even at high voltages. Accordingly, using a solid electrolyte makes it possible to utilize high-voltage electrode materials that were difficult to use in a liquid electrolyte.

Generally, solid electrolytes used in lithium secondary batteries can be classified into oxide-based solid electrolytes and sulfide-based solid electrolytes. Among these, sulfide-based solid electrolytes have the advantage of higher ionic conductivity compared to oxide-based solid electrolytes. As a sulfide-based solid electrolyte, a solid electrolyte containing lithium sulfide is being studied as having high ionic conductivity.

However, when an excessive amount of lithium sulfide is included in the solid electrolyte to increase ionic conductivity, the large amount of lithium sulfide remaining in the final product reacts with moisture or increases the interfacial reactivity with the active material, which actually reduces the electrochemical stability of the lithium secondary battery. There is a problem with reducing it. Accordingly, there is a need for technology to improve ionic conductivity while containing lithium sulfide.

The problem to be solved by the present invention is to provide a lithium secondary battery solid electrolyte that improves ionic conductivity and is electrochemically stable, and a method of manufacturing the same.

In order to solve the above problem, one aspect of the present invention provides a solid electrolyte for a lithium secondary battery. The lithium secondary battery solid electrolyte has a thio-LISICON II analog phase formed from an amorphous binder of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ). Contains glass ceramics.

The amorphous binder is 74 mol% to 75 mol% of lithium sulfide (Li ₂ S), 20 mol% to 22 mol% of phosphorus pentasulfide (P ₂ S ₅ ), and 3 mol% of lithium sulfate (Li ₂ SO ₄ ). It may contain from 5 mol%.

The amorphous binder may be combined by a ball mill.

The organic ceramic may be formed by heat treating the amorphous binder at 215°C to 230°C.

In order to solve the above problem, another aspect of the present invention provides a method for manufacturing a lithium secondary battery solid electrolyte. The manufacturing method includes forming an amorphous binder by mechanically pulverizing a mixture of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ), and forming the amorphous binder. It includes heat treatment to form a glass ceramic having a thio-LISICON II analog phase.

The mixture includes 74 mol% to 75 mol% of lithium sulfide (Li ₂ S), 20 mol% to 22 mol% of phosphorus pentasulfide (P ₂ S ₅ ), and 3 mol% to 5 mol% of lithium sulfate (Li ₂ SO ₄ ). It may contain mole %.

The step of mechanically pulverizing the mixed material to form an amorphous binder may include pulverizing the mixed material using a ball mill at 300 rpm to 550 rpm for 20 to 55 hours.

The step of heat treating the amorphous binder to form a glass ceramic having a thio-LISICON II-like phase may include heat treating the amorphous binder at 215°C to 230°C.

According to the present invention, the lithium secondary battery solid electrolyte includes a glass ceramic having a thio-LISICON II analog phase formed from an amorphous binder of lithium sulfide, phosphorus pentasulfide, and lithium sulfate, so that the ions of the lithium secondary battery solid electrolyte Conductivity and electrochemical stability can be improved together.

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

Figure 1 is a flowchart showing a method of manufacturing a lithium secondary battery solid electrolyte according to an embodiment of the present invention.
Figure 2 is a diagram showing an X-ray diffraction of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.
Figure 3 is a diagram showing an X-ray diffraction diagram of glass ceramic included in a lithium secondary battery solid electrolyte according to embodiments of the present invention.
Figure 4 is a diagram measuring the ionic conductivity of a lithium secondary battery solid electrolyte according to embodiments of the present invention.
Figures 5a and 5b are cyclic voltammetry analysis diagrams showing the electrochemical stability of a lithium secondary battery solid electrolyte according to an example and a comparative example of the present invention.
Figure 6 is a diagram showing an X-ray diffraction diagram of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.
Figure 7 is a diagram showing an X-ray diffraction diagram of glass ceramic included in the solid electrolyte of a lithium secondary battery according to embodiments of the present invention.
Figure 8 is a diagram showing a differential thermal analysis diagram of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.
FIG. 9 is a partially enlarged view of the X-ray diffraction diagram of FIG. 7.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

1 is a flowchart showing a method of manufacturing a lithium secondary battery solid electrolyte according to an embodiment of the present invention.

Referring to FIG. 1, the method for manufacturing a lithium secondary battery solid electrolyte according to this embodiment includes mechanically pulverizing a mixture of lithium sulfide, phosphorus pentasulfide, and lithium sulfate to form an amorphous binder (S10), and forming an amorphous binder. It may include a step (S20) of heat treating to form a glass ceramic having a thio-LISICON II analog phase. Hereinafter, each step will be described in more detail.

In step S10, a mixture of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ) is prepared as a starting material, and the mixture is mechanically pulverized to form an amorphous binder. In the mixture, the mixing ratio of lithium sulfide, phosphorus pentasulfide, and lithium sulfate may be 74 to 75: 20 to 22: 3 to 5, respectively, based on the molar ratio (mol%). Lithium sulfide (Li ₂ S)-phosphorus pentasulfide (P ₂ S ₅ )-based lithium secondary battery solid electrolyte has higher ionic conductivity than oxide-based solid electrolyte, and accordingly, the content of lithium sulfide in the starting material is about 70 mol% or more. needs to be included. However, when the content of lithium sulfide is excessive, as the amount of lithium sulfide remaining in the final formed glass ceramic increases, moisture reactivity and reactivity with the active material interface increase, and electrochemical stability decreases. Therefore, the above-mentioned mixing ratio is the optimal ratio for improving ionic conductivity while reducing the content of lithium sulfide remaining in the final formed glass ceramic, which will be explained in detail later.

In step S20, the amorphous binder is heat treated to form a glass ceramic having a thio-LISICON II-like phase. When the conditions for heat treatment of the amorphous binder are appropriate, glass ceramics including a thio-LISICON II analog phase can be formed. Thio-LISICON II phase, Kanno et al., Lithium Ionic Conductor Thio-LISICON:The Li2S-GeS2-P2S5 System, Journal of The Electrochemical Society, 148(7) A742-A746, 2001. (hereinafter referred to as ‘Kanno’ ), as a crystal phase showing superionic conductivity (LISICON) for lithium ions, a specific crystal structure of Li _{4 - x} Ge _{1 -x} P _x S ₄ (x is 0.0 to 1.0) It is a crystal structure that appears only at mixing ratios. Specifically, in Kanno, in the crystal structure of Li _{4 - x} Ge _{1 - x} P _x S ₄ (x is 0.0 to 1.0), the thio-LISICON II phase appears when x = 0.65, 0.7, 0.75, and x = 0.8, 1.0 By confirming that the thio-LISICON Ⅲ phase appears, it was confirmed that although the ionic conductivity is improved even when the thio-LISICON Ⅲ phase is present, the ionic conductivity is higher when the thio-LISICON Ⅱ phase is present.

The present inventors mechanically pulverized a mixture of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ) in the above-mentioned mixing ratio under appropriate conditions to form an amorphous binder. It was confirmed that when the glass ceramic was formed by heat treatment under appropriate temperature conditions, a thio-LISICON II-like phase appeared and ionic conductivity improved. In addition, it was confirmed that at the above-mentioned mixing ratio, the content of lithium sulfide remaining in the glass ceramic was reduced. This will be explained in more detail in the embodiments described later.

Meanwhile, mechanical grinding in step S10 may be performed by ball milling, in which case the crystallization temperature of the amorphous binder may vary depending on milling conditions. For example, milling speed, milling time, milling medium, ball to powder ratio, etc. may affect the crystallization temperature of the amorphous binder. In addition, the thio-LISICON Ⅱ pseudo-phase has higher ionic conductivity than the thio-LISICON Ⅲ pseudo-phase but is less chemically stable, so even if the heat treatment temperature is slightly different above the crystallization temperature, the thio-LISICON Ⅲ-like phase is formed. This makes it difficult to obtain thio-LISICON Ⅱ similar images. Therefore, a mixture of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ) in the above-mentioned mixing ratio is mechanically ground under appropriate grinding conditions to form an amorphous binder. And it is important to heat treat it under appropriate temperature conditions.

According to embodiments of the present invention, the mixture is ground by a ball mill at 300 rpm to 550 rpm for 20 to 55 hours to form an amorphous binder, and the amorphous binder is heat treated at 215°C to 230°C, Glass ceramics with a thio-LISICON II-like phase can be formed.

Below, a preferred embodiment (example) is presented to aid understanding of the present invention. However, the following examples are only intended to aid understanding of the present invention, and the present invention is not limited by the following examples.

Example 1

Lithium sulfide (Li ₂ S) was used with a purity of 99.9% provided by Alfa Aesar, and phosphorus pentasulfide (P ₂ S ₅ ) was used with a purity of 99% provided by Sigma-Aldrich. Using prepared lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ) and lithium sulfate (Li ₂ SO ₄ ) as starting materials, Li ₂ S : P ₂ S ₅ : Li was prepared in an argon gas atmosphere in a glove box. A mixed powder was prepared by mixing ₂ SO ₄ = 75:22:3 in a mixing ratio (mol%). Next, 120 g of 3 mm zirconia balls and 3 g of mixed powder were mixed in an alumina pot with a volume of 100 ml, and mechanically pulverized for 48 hours at a rotation speed of 370 rpm using a planetary ball mill from Fritsch. An amorphous binder was formed. The obtained amorphous binder was heat treated at 215°C for 3 hours in an argon atmosphere to form glass ceramic powder.

Example 2

Glass ceramic powder was formed in the same process as in Example 1, except that the mixing ratio (mol%) of the starting materials was Li ₂ S : P ₂ S ₅ : Li ₂ SO ₄ = 75 : 21 : 4. did.

Example 3

Glass ceramic powder was formed in the same process as Example 1, except that the mixing ratio (mol%) of the starting materials was Li ₂ S : P ₂ S ₅ : Li ₂ SO ₄ = 75 : 19 : 6. did.

Example 4

The mixing ratio (mol%) of the starting materials is Li ₂ S : P ₂ S ₅ : Li ₂ SO ₄ = 75 : 21 : 4 and mechanically pulverized at 520 rpm for 20 hours to form an amorphous binder. Glass ceramic powder was formed in the same process as Example 1, except that heat treatment was performed at 220°C and 230°C, respectively (Example 4-1 and Example 4-2).

Example 5

The mixing ratio (mol%) of the starting materials was mixed at Li ₂ S : P ₂ S ₅ : Li ₂ SO ₄ = 74 : 21 : 5, and the mechanically pulverized amorphous binder was heat treated at 220°C and 230°C, respectively. Glass ceramic powder was formed in the same process as Example 4, except for (Example 5-1 and Example 5-2).

Comparative Example 1

As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were mixed at a mixing ratio (mol %) of Li ₂ S : P ₂ S ₅ = 80 : 20. Glass ceramic powder was formed in the same process as Example 1.

Comparative Example 2

As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were mixed at a mixing ratio (mol %) of Li ₂ S : P ₂ S ₅ = 75 : 25. Glass ceramic powder was formed in the same process as Example 1.

Comparative Example 3

The mixing ratio (mol%) of the starting materials was mixed at Li ₂ S : P ₂ S ₅ = 78 : 22, and the mechanically ground amorphous binder was heat-treated at 220°C and 230°C, respectively (Comparative Example 3-1 and Comparative Example 3-2), glass ceramic powder was formed in the same process as Example 4.

Figure 2 is a diagram showing an X-ray diffraction (XRD) of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.

Referring to FIG. 2, a small amount of lithium sulfide (Li ₂ S) crystals is confirmed in the amorphous binder obtained by mixing the starting materials by mechanical grinding. From the results of Comparative Example 1 and Comparative Example 2, it was confirmed that when the content of lithium sulfide was 75 mol%, the amorphous binder did not contain lithium sulfide crystals. However, as will be described later with reference to FIG. 3, in this case, only a thio-LISICON III-like phase with relatively low ionic conductivity is obtained through heat treatment. Therefore, in order to obtain a glass ceramic with high ionic conductivity while minimizing remaining lithium sulfide crystals, as in Example 1 or Example 2, Li ₂ S : P ₂ S ₅ : Li ₂ SO ₄ = 75: 21 : 4 Alternatively, it is necessary to configure the starting materials in a mixing ratio (mol%) of 75:22:3. In the case of Example 3, it was confirmed that the lithium sulfide crystals remaining in the amorphous binder were more prominent than those of Examples 1 and 2.

Figure 3 is a diagram showing an X-ray diffraction diagram of glass ceramic included in a lithium secondary battery solid electrolyte according to embodiments of the present invention.

Referring to FIG. 3, an X-ray diffraction pattern of glass ceramic formed by heat treating the amorphous binders of FIG. 2 is shown. When comparing Comparative Example 1 and Comparative Example 2, it was confirmed that although a thio-LISICON II-like phase appeared in the glass ceramic of Comparative Example 1, a peak of lithium sulfide crystals also appeared strongly. On the other hand, in the glass ceramic of Comparative Example 2, a thio-LISICON III-like phase was confirmed, which has lower ionic conductivity than the thio-LISICON II-like phase.

Meanwhile, Example 1 and Example 2 were each confirmed to have thio-LISICON II similarity. At this time, although the crystal pattern of lithium sulfide was confirmed in Examples 1 and 2, it was confirmed to have a weaker peak intensity compared to Comparative Example 1. In the case of Example 3, it was confirmed that the crystal pattern of lithium sulfide appeared strongly and the crystal structure of the thio-LISICON II-like phase did not appear well.

In this way, when lithium sulfate is not added to the lithium sulfide-phosphorus pentoxide mixture, if the amount of lithium sulfide is reduced (75 mol%), the remaining lithium sulfide is reduced, but the thio-LISICON II-like phase does not appear (Comparative Example 2) When the amount of lithium sulfide is increased (80 mol%), a thio-LISICON II-like phase appears, but the remaining lithium sulfide increases (Comparative Example 1).

In contrast, when lithium sulfate is added to a lithium sulfide-phosphorus pentoxide mixture, even if lithium sulfide is mixed in the same ratio (75 mol%), if the addition ratio of lithium sulfate is 3 mol% or 4 mol%, thio-LISICON II is similar. It can be seen that a phase appears and the amount of remaining lithium sulfide is reduced. However, when the addition ratio of lithium sulfate was 6 mol%, the thio-LISICON II-like phase did not appear well, and the amount of remaining lithium sulfide was also confirmed to increase.

Figure 4 is a diagram measuring the ionic conductivity of a lithium secondary battery solid electrolyte according to embodiments of the present invention.

Referring to Figure 4, the results of measuring ionic conductivity at room temperature (25°C) for the glass ceramics obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are shown. As confirmed in Figure 3, Comparative Example 1 (red) has a thio-LISICON II-like phase and thus exhibits high ionic conductivity. However, as confirmed in Figure 3, there is a problem with a lot of residual lithium sulfide (Li ₂ S). there is. In comparison, Comparative Example 2 had less residual lithium sulfide, but was measured to have the lowest ionic conductivity. In Examples 1 and 2, it was confirmed that the ionic conductivity was high while the residual lithium sulfide was reduced, and in Example 3, where the thio-LISICON II-like phase was not clearly observed, the ionic conductivity was confirmed to be reduced.

Figures 5a and 5b are cyclic voltammetry analysis diagrams showing the electrochemical stability of a lithium secondary battery solid electrolyte according to an example and a comparative example of the present invention. FIG. 5A shows the results of cyclic voltammetry measurements for the solid electrolyte of a lithium secondary battery containing the glass ceramic of Example 1, and FIG. 5B shows the results of cyclic voltammetry measurements of the solid electrolyte of a lithium secondary battery containing the glass ceramic of Comparative Example 1. Shows the results.

Referring to FIGS. 4, 5A, and 5B, both Example 1 and Comparative Example 1 have a thio-LISICON II-like phase and thus have high ionic conductivity, but in Comparative Example 1, there is a lot of residual lithium sulfide (Li ₂ S). , as a result of cyclic voltammetry measurements, it was confirmed that electrochemical stability was low. On the other hand, in Example 1, it can be seen that the ion conductivity is maintained high while being electrochemically stable.

Therefore, it can be seen that the ionic conductivity and electrochemical stability of the solid electrolyte of a lithium secondary battery are improved only when the starting materials are mixed at the mixing ratio of Example 1 or Example 2.

Figure 6 is a diagram showing an X-ray diffraction diagram of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.

Referring to FIG. 6, X-ray diffraction patterns for the amorphous binders of Examples 4, 5, and Comparative Example 3 are shown. In all of Examples 4, 5, and Comparative Example 3, it was confirmed that lithium sulfide (Li ₂ S) crystals remained in the amorphous binder. On the other hand, the diffraction peak of lithium sulfate (Li ₂ SO ₄ ) added to the mixture is not confirmed in the diffraction pattern of the amorphous binder, which shows that the lithium sulfate added to the lithium sulfide-phosphorus pentasulfide is completely amorphized by mechanical grinding and becomes amorphous. It can be seen that it is included in the binder.

Figure 7 is a diagram showing an X-ray diffraction diagram of glass ceramic included in the solid electrolyte of a lithium secondary battery according to embodiments of the present invention.

Referring to FIG. 7, an X-ray diffraction pattern of glass ceramic obtained by heat treating the amorphous binder of FIG. 6 at different temperatures is shown. As described above, the crystalline phase obtained from glass ceramic may vary depending on the conditions for heat treatment of the amorphous binder. In Comparative Example 3 and Example 4, a thio-LISICON II-like phase was obtained when heat treated at 220°C (Example 4-1, Comparative Example 3-1), but when heat treated at 230°C (Example 4-2 In Comparative Example 3-2), a thio-LISICON III-like phase with lower ionic conductivity was obtained. On the other hand, the glass ceramic of Example 5 was confirmed to contain a thio-LISICON II-like phase whether heat-treated at 220°C (Example 5-1) or 230°C (Example 5-2). do. In addition, it was confirmed that residual lithium sulfide (Li ₂ S) was reduced in the glass ceramic of Example 5. This result can be assumed to be because 5 mol% of sulfuric acid added to lithium sulfide-phosphorus pentasulfide improves the thermal stability of the thio-LISICON II-like phase.

Figure 8 is a diagram showing differential scanning calorimetry (DSC) of an amorphous binder used to form a lithium secondary battery solid electrolyte according to embodiments of the present invention.

Referring to Figure 8, in Comparative Example 3, the crystallization temperature peaks of the amorphous binder were 209.7°C and 241.4°C, in Example 4, the crystallization temperature peaks were 210.1°C and 258.1°C, and in Example 5 In this case, the crystallization temperature peaks were 213.5℃ and 262.7℃. At this time, the temperature of the second peak among the peaks of crystallization temperature is related to forming a thio-LISICON III-like phase, and from Comparative Example 3 to Example 4 and Example 5, the temperature of the second peak increases toward a higher temperature. It shifts. On the other hand, the temperature of the first peak among the crystallization temperatures did not change significantly, and in the case of Comparative Example 3, Example 4, and Example 5, the first peak appeared below 215°C.

In this way, the temperature interval between the first peak and the second peak increases as the amount of lithium sulfate (Li ₂ SO ₄ ) is added to the starting material, which shows that lithium sulfate crystallizes into a thio-LISICON III-like phase even at a high heat treatment temperature. It can be assumed that it plays a role in stabilizing the thio-LISICON II analogue by suppressing .

FIG. 9 is a partially enlarged view of the X-ray diffraction diagram of FIG. 7.

Referring to FIG. 9, it is confirmed that the thio-LISICON II-like peaks shift to higher angles from Comparative Example 3 to Examples 4 and 5. This can be assumed to be because, in the crystal lattice of the thio-LISICON II-like phase, sulfur atoms are replaced by oxygen atoms with smaller ionic radii, thereby reducing the crystal lattice. In this case, the SO bond is broken within the anion, and a new PO bond is formed in the PS ₄ ^3- anion of the tetrahedral structure, which should be incorporated into the network of the thio-LISICON II-like phase. Although more detailed structural changes have not yet been confirmed, according to calculations considering the effective radius of the ion, the radius of the anion due to the PO bond (0.292 nm) is smaller than that of the PS ₄ ^3- anion (0.385 nm), It can be assumed that the crystal lattice of the thio-LISICON II pseudophase is reduced. In this way, it can be seen that as an appropriate amount of lithium sulfate (Li ₂ SO ₄ ) is added to the lithium sulfide-phosphorus pentasulfide solid electrolyte, the thio-LISICON II-like phase is better formed and more stable.

As described above, according to the present invention, the lithium secondary battery solid electrolyte includes a glass ceramic having a thio-LISICON II analog phase formed from an amorphous binder of lithium sulfide, phosphorus pentasulfide, and lithium sulfate, thereby forming a lithium secondary battery. The ionic conductivity and electrochemical stability of the solid electrolyte can be improved together.

Meanwhile, the embodiments of the present invention disclosed in the specification and drawings are merely provided as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that in addition to the embodiments disclosed herein, other modifications based on the technical idea of the present invention can be implemented.

Claims (8)

It includes a glass ceramic having a thio-LISICON II analog phase formed from an amorphous binder of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ),
The amorphous binder is 74 mol% to 75 mol% of lithium sulfide (Li ₂ S), 20 mol% to 22 mol% of phosphorus pentasulfide (P ₂ S ₅ ), and 3 mol% of lithium sulfate (Li ₂ SO ₄ ). A solid electrolyte for a lithium secondary battery containing from 5 mol%. delete According to paragraph 1,
The amorphous binder is a lithium secondary battery solid electrolyte combined by a ball grinder. According to paragraph 1,
The glass ceramic is a lithium secondary battery solid electrolyte that is formed by heat treating the amorphous binder at 215°C to 230°C. Forming an amorphous binder by mechanically pulverizing a mixture of lithium sulfide (Li ₂ S), phosphorus pentasulfide (P ₂ S ₅ ), and lithium sulfate (Li ₂ SO ₄ ); and
Comprising the step of heat treating the amorphous binder to form a glass ceramic having a thio-LISICON II analog phase,
The mixture includes 74 mol% to 75 mol% of lithium sulfide (Li ₂ S), 20 mol% to 22 mol% of phosphorus pentasulfide (P ₂ S ₅ ), and 3 mol% to 5 mol% of lithium sulfate (Li ₂ SO ₄ ). Method for producing a lithium secondary battery solid electrolyte containing mol%. delete According to clause 5,
The step of mechanically pulverizing the mixture to form an amorphous binder includes grinding the mixture using a ball mill at 300 rpm to 550 rpm for 20 to 55 hours. According to clause 5,
The step of heat-treating the amorphous binder to form a glass ceramic having a thio-LISICON II-like phase includes heat-treating the amorphous binder at 215°C to 230°C. A method of producing a solid electrolyte for a lithium secondary battery.