Solid electrolyte, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

The present invention relates to a solid electrolyte, a method for manufacturing the same, and a lithium secondary battery including the same. In the solid electrolyte according to an embodiment of the present invention, a part of a halogen element can be doped with oxygen.

Description

[Technical Field]

[0001] This invention relates to batteries, and more particularly to solid electrolytes, methods for producing the same, and lithium secondary batteries containing the same. [Background technology]

[0002] Recently, the surge in demand for IT mobile devices and small power-driven devices such as electric bicycles and mini electric vehicles has led to increased interest in high-capacity batteries. This increased demand has also fueled active research into the safety and energy density of such batteries.

[0003] As a result, research into all-solid-state batteries is actively being conducted as a material to improve the safety of existing secondary batteries and increase energy density. All-solid-state batteries are batteries in which the liquid electrolyte used in existing lithium secondary batteries is replaced with a solid. Because they do not use flammable solvents in the battery and do not cause ignition or explosion due to reactions such as the decomposition reaction of conventional electrolytes, battery safety can be improved. In addition, since lithium metal or lithium alloy can be used as the negative electrode material, the energy density relative to the mass and volume of the battery can be improved.

[0004] In all-solid-state batteries, inorganic solid electrolytes are generally used, and various studies have been conducted on sulfide-based solid electrolytes having the same composition as Li6PS5Cl, which has an argyrodite structure. However, these sulfide-based solid electrolytes have the problem of being difficult to handle in general atmospheric conditions due to side reactions with moisture. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The technical problem that this invention aims to solve is to provide an all-solid-state battery that is easy to handle in the atmosphere.

[0006] Another technical problem that the present invention aims to solve is to provide a method for manufacturing an all-solid-state battery having the aforementioned advantages.

[0007] Another technical problem that the present invention aims to solve is to provide a lithium secondary battery, including an all-solid-state battery having the aforementioned advantages. [Means for solving the problem]

[0008] In one embodiment of the present invention, the solid electrolyte may be of the argyrodite type in which some of the halogen elements are doped with oxygen. In one embodiment, the solid electrolyte is Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The composition can be (1≦x≦2, 0.01≦y≦0.3). In one embodiment, the solid electrolyte can satisfy the following formula 1. <Expression 1> 3.5 ≤ [S] / [P] ≤ 4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.)

[0009] In one embodiment, the solid electrolyte had XRD peak values ​​of 2θ=15.5°±0.5°, 2θ=18°±0.5°, 2θ=25.5°±0.5°, 2θ=30.2°±0.5°, and 2θ= 31.5° Diffraction peaks can be present at ±0.5°deg. In one embodiment, the ionic conductivity of the solid electrolyte before exposure to air can be 3.1 mS / cm or higher. In one embodiment, the reduction rate of the ionic conductivity of the solid electrolyte after exposure to air compared to before exposure to air may be 35% or less.

[0010] The method for manufacturing a solid electrolyte according to another embodiment of the present invention includes steps of preparing a lithium raw material substance, a sulfur raw material substance, a halogen raw material substance, and a doping raw material substance, mixing the raw material substances, and heat-treating the resultant obtained by the mixing. The doping raw material substance may be a raw material substance containing oxygen. In one embodiment, the doping raw material substance may contain a phosphate-based compound.

[0011] In one embodiment, the phosphate-based compound may include at least one selected from the group consisting of Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3. In one embodiment, in the step of preparing the raw material substances, based on 100 mol% of the solid electrolyte, 0.01 to 0.3 mol% of the phosphate-based compound can be added.

[0012] In one embodiment, the lithium raw material substance may be Li2S, the sulfur raw material substance may be P2S5, and the halogen raw material substance may be LiCl. In one embodiment, the doping raw material substance may contain a phosphate-based compound.

[0013] In one embodiment, Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y (1 ≦ x ≦ 2, 0.01 ≦ y ≦ 0.3) may be satisfied. In one embodiment, the solid electrolyte can satisfy the following Formula 1. <Formula 1> 3.5 ≦ [S] / [P] ≦ 4.1 (In the above Formula 1, [S] and [P] respectively represent at% of S and P)

[0014] The lithium secondary battery according to another embodiment of the present invention includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte positioned between the positive electrode and the negative electrode. The solid electrolyte may be an argyrodite type in which a part of the halogen element is doped with oxygen. In one embodiment, the solid electrolyte is Li (xy-x-5y+7) P (1-y) S(xy-x-5y+6) Cl x-xy O 4y It can have a composition of the form (1 ≤ x ≤ 2, 0.01 ≤ y ≤ 0.3).

[0015] In one embodiment, the solid electrolyte can satisfy the following formula 1. <Expression 1> 3.5 ≤ [S] / [P] ≤ 4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.) [Effects of the Invention]

[0016] An all-solid-state battery according to one embodiment of the present invention is Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y By including a composition with the following properties (1≦x≦2, 0.01≦y≦0.3), it is possible to provide an all-solid-state battery that is more stable in air, has superior initial capacity, and a longer lifespan compared to existing sulfide-based solid electrolytes.

[0017] A method for manufacturing an all-solid-state battery according to another embodiment of the present invention can manufacture an all-solid-state battery having the advantages described above.

[0018] Lithium secondary batteries according to other embodiments of the present invention can provide lithium secondary batteries, including all-solid-state batteries having the advantages described above. [Brief explanation of the drawing]

[0019] [Figure 1] This graph shows the relationship between XRD peak intensity and various embodiments of the present invention. [Figure 2] This is a flowchart for a method of producing a solid electrolyte according to one embodiment of the present invention. [Modes for carrying out the invention]

[0020] The terms first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section, without departing from the scope of the invention.

[0021] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form as used herein also includes the plural form unless the wording explicitly indicates the opposite. The meaning of “includes” as used herein is to embody a particular characteristic, domain, integer, step, operation, element and / or component, and does not exclude the presence or addition of other characteristics, domains, integers, steps, operations, elements and / or components.

[0022] When it is stated that one part is "on top of" or "above" another part, it may be directly on top of or above the other part, or it may have the other part between them. In contrast, when it is stated that one part is "directly on top of" another part, there is no other part between them.

[0023] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are additionally interpreted to have the meaning consistent with the relevant technical literature and the present disclosures, and are not interpreted in their ideal or highly formal sense unless otherwise defined.

[0024] Also, unless otherwise specified, % means weight percent, and 1 ppm is 0.0001 weight percent.

[0025] Figure 1 shows a graph of XRD peak intensity for various embodiments of the present invention.

[0026] Referring to Figure 1, the solid electrolyte according to one embodiment of the present invention may be an argyrodite type in which some of the halogen elements are doped with oxygen. The solid electrolyte refers to a solid material having lithium (Li) ion conductivity that can be used as a substitute for electrolyte and separator during battery design, for example, rather than a film SEI (Solid Electrolyte Interphase) that forms at the electrode material interface, such as in the initial charge-discharge reaction after battery manufacturing.

[0027] The solid electrolyte of the present invention having the above composition is a sulfur-containing compound and can be a sulfide-based solid electrolyte. Specifically, the argyrodite type can have an argyrodite-type structure containing halogen elements such as lithium (Li), phosphorus (P), sulfur (S), and chlorine (Cl). The solid electrolyte may be in the form of particles or powder and can be crystalline or amorphous.

[0028] In one embodiment, the solid electrolyte is Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The solid electrolyte can have a composition of (1≦x≦2, 0.01≦y≦0.3). By doping some of the halogen elements with oxygen, the solid electrolyte can be made moisture-safe and maintain stability even when exposed to the atmosphere without degrading the ionic conductivity and cell performance of the solid electrolyte.

[0029] In one embodiment, the solid electrolyte of the present invention satisfies the following formula 1. <Expression 1> 3.5 ≤ [S] / [P] ≤ 4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.)

[0030] The at% ratio of sulfur to phosphorus may be 3.5 to 4.1. The advantage of the value of formula 1 satisfying this range is that it prevents deterioration of the ionic conductivity and cell performance of the solid electrolyte.

[0031] If the value of Equation 1 exceeds the upper limit, there is a problem of decreased conductivity. If the value of Equation 1 exceeds the lower limit, there is a problem of decreased stability against moisture.

[0032] In one embodiment, the solid electrolyte can have a peak intensity at a predetermined position in the X-ray diffraction pattern measured by an X-ray diffractometer (XRD). Specifically, the solid electrolyte having the above composition has XRD peak values ​​of 2θ=15.5°±0.5°deg, 2θ=18°±0.5°deg, 2θ=25.5°±0.5°deg, 2θ=30.2°±0.5°deg, and 2θ= 31.5° It can have a range of ±0.5°.

[0033] In one embodiment, the solid electrolyte may be characterized by not having the XRD peak values ​​2θ=17°±0.5°deg and 2θ=21.5°±3°deg. The XRD peak values ​​2θ=17°±0.5°deg and 2θ=21.5°±3°deg correspond to impurity peaks, and by having a solid electrolyte in which these peaks are not observed, atmospheric stability and electrochemical stability can be improved.

[0034] Figure 2 is a flowchart showing a method for producing a solid electrolyte according to one embodiment of the present invention.

[0035] Referring to Figure 2, another embodiment of the present invention provides a method for producing an argyrodite-type solid electrolyte, comprising the steps of preparing lithium raw materials, sulfur raw materials, halogen raw materials, and doping raw materials (S100), mixing the raw materials (S200), and heat-treating the resulting product obtained by mixing (S300).

[0036] In one embodiment, the step (S100) of preparing a lithium raw material, a sulfur raw material, a halogen raw material, and a doping raw material can, for example, involve preparing Li2S as the lithium raw material, P2S5 as the sulfur raw material, and LiCl as the halogen raw material.

[0037] In one embodiment, the doping raw material may be a raw material containing oxygen. For example, the doping raw material may be a phosphate compound. By using the phosphate compound as a doping raw material, it is more stable in the atmosphere than existing argyrodite solid electrolytes, and its initial capacity and lifespan are improved.

[0038] In one embodiment, the phosphate compound may include at least one selected from the group consisting of Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3. Specifically, the doping material may be Li3PO4.

[0039] In one embodiment, the step of preparing the raw materials (S100) may involve adding 0.01 to 0.3 mol% of the phosphate compound. By ensuring that the amount of the phosphate compound added falls within this range, it is possible to include a sulfide-based solid electrolyte containing a certain proportion of oxygen (O), thereby providing a solid electrolyte with excellent moisture stability.

[0040] If the amount of the phosphate compound added exceeds the upper limit, problems arise such as the formation of an impurity phase or a decrease in ionic conductivity. If the amount of the phosphate compound added exceeds the lower limit, problems arise such as the difficulty in confirming the atmospheric stabilization effect.

[0041] In one embodiment, the argyrodite-type solid electrolyte is Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y It can have a composition of the form (1 ≤ x ≤ 2, 0.01 ≤ y ≤ 0.3).

[0042] The method for producing a solid electrolyte involves the step (S100) of preparing Li2S, P2S5, LiCl, and Li3PO4 raw materials, and the Li of the solid electrolyte composition described above. (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The raw material can be controlled to correspond to (1 ≤ x ≤ 2, 0.01 ≤ y ≤ 0.3).

[0043] The step of mixing the raw materials (S200) can be carried out by mechanical mixing or chemical mixing. For example, mechanical mixing can utilize methods such as paint shakers, ball mills, bead mills, homogenizers, hammer mills, and oil mills, while chemical mixing can utilize methods such as melt-quenching. Specifically, the step of mixing the raw materials (S200) can be carried out by mixing the raw materials with an oil mill.

[0044] The step of heat-treating the resulting product obtained by mixing (S300) is a calcination step, which involves applying heat to the mixed product. In one embodiment, the step of heat-treating the resulting product obtained by mixing (S300) can be carried out after additional steps such as drying, stirring, washing, sizing, and classification, as needed.

[0045] In one embodiment, the heat treatment can be carried out in an inert atmosphere. The inert atmosphere can be an H2, He, or Ar atmosphere, as an unrestricted example. Specifically, the inert atmosphere may be an Ar atmosphere.

[0046] In one embodiment, the heat treatment can be carried out at a temperature of 300°C or higher. Specifically, the heat treatment can be carried out in a temperature range of 300 to 800°C, more specifically 350 to 700°C, and more specifically 400 to 600°C. If the heat treatment is performed at a temperature lower than the above, there is a problem that the solid-phase reaction and crystallization reaction do not proceed smoothly.

[0047] Thus, the solid electrolyte produced through the steps described above is Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The solid electrolyte can have a composition of (1≦x≦2, 0.01≦y≦0.3), and exhibits excellent atmospheric stability, improved initial capacity, and lifespan. A detailed description of the solid electrolyte of the synthesized result is consistent with Figure 1 above to the extent that it does not contradict the original.

[0048] Lithium secondary batteries according to other embodiments of the present invention may include a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a solid electrolyte located between the positive and negative electrodes. The solid electrolyte may be shown in Figure 1 above, and the solid electrolyte is the same to the extent that it is not inconsistent with Figure 1 above.

[0049] The positive electrode is LiCoO2, LiNiO2, LiNi x Mn y O2, Li 1+z Ni x Mn y Co 1-x-y O2, LiLiLi x Co y Al z The positive electrode is one of the following: O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, LiFeO2, LiFePO4, and combinations thereof, where x is 0.3 to 0.8, y is 0.1 to 0.45, and z can be independently 0 to 0.2. More specifically, the positive electrode may be LiFePO4, LiCoO2, NCM811, and NCM622.

[0050] The negative electrode is made of carbonaceous materials such as natural graphite, artificial graphite (mesophase carbon microbeads), pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase pitches, and petroleum or coal tar pitch-derived cokes; lithium-containing titanium composite oxide (LTO), metals such as Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe (Me); alloys composed of the aforementioned metals; and oxides of the aforementioned metals (MeO x ); and the aforementioned metals (Me) and carbon composites, and combinations thereof may also be used. Specifically, the negative electrode may be natural graphite nanoparticles, synthetic graphite nanoparticles, Sn nanoparticles, Li4Ti5O 12 The negative electrode may be fine particles, Si fine particles, Si-C composite fine particles, or combinations thereof. More specifically, the negative electrode may be natural graphite, artificial graphite, silicon, or combinations thereof.

[0051] Thus, a lithium secondary battery containing the solid electrolyte of the present invention can maintain stability in the atmosphere and improve its initial capacity and lifespan. [Examples]

[0052] The following describes specific embodiments of the present invention. However, the following embodiments are merely specific examples of the present invention, and the present invention is not limited to these embodiments.

[0053] [Comparative Example 1] (Preparation of Li6PS5Cl) A common argyrodite solid electrolyte, Li6PS5Cl, was prepared.

[0054] [Comparative Example 2] (Li 5.5 PS 4.5 Cl 1.5 (Manufacturing) Li 5.5 PS 4.5 Cl 1.5It is synthesized through dry milling. In the dry milling process, Li2S, P2S5, and LiCl are mixed using an oil-based mill (planetary mill) at 300 rpm for 8 hours, then pellets are produced at 300 MPa, and the mixture is synthesized through heat treatment at 550°C in an argon (Ar) atmosphere.

[0055] [Example 1] (Li 5.465 P 0.99 S 4.465 Cl 1.485 O 0.04 (Manufacturing) Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y Using a solid electrolyte, Li2S, P2S5, LiCl, and Li2PO4 were quantified by applying x=1.5 and y=0.01. After adding 0.01 mol% of Li3PO4, the mixture was mixed at 300 rpm for approximately 8 hours using an oil-based mill, and then pellets were prepared at 300 MPa. The mixture was then synthesized by heat treatment at 550°C in an argon (Ar) atmosphere.

[0056] [Example 2] (Li 5.395 P 0.97 S 4.395 Cl 1.455 O 0.12 (Manufacturing) Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The procedure was carried out in the same manner as in Example 1, except that y=0.03 was applied to the solid electrolyte and 0.03 mol% of Li3PO4 was added.

[0057] [Example 3] (Li 5.325 P 0.95 S 4.325 Cl 1.425 O 0.20 (Manufacturing) Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4yThe solid electrolyte with y = 0.05 was applied, and the procedure was the same as in Example 1 except that 0.05 mol% of Li3PO4 was added.

[0058] [Example 4] (Manufacture of (Li 5.15 P 0.90 S 4.15 Cl 1.35 O 0.40 ) Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The solid electrolyte with y = 0.10 was applied, and the procedure was the same as in Example 1 except that 0.1 mol% of Li3PO4 was added.

[0059] [Example 5] (Manufacture of (Li 4.80 P 0.80 S 3.80 Cl 1.20 O 0.80 ) Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y The solid electrolyte with y = 0.20 was applied, and the procedure was the same as in Example 1 except that 0.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Table 1 below shows the electrochemical evaluation and moisture stability assessment for Comparative Examples 1 and 2 and Examples 1-6. The electrochemical evaluation was performed using ionic conductivity at 30°C and 0.1C. The solid electrolytes for Comparative Examples 1 and 2 and Examples 1-6 were evaluated using a powder compaction cell. After administering the electrolyte, the compaction was densified at 300 MPa. Subsequently, the cell was fastened at a pressure of 70 MPa using a SUS electrode, and the impedance was measured by applying 10 mV at 25°C. The impedance represents the measurement of ionic conductivity.

[0062] The aforementioned moisture stability was evaluated by leaving 2 g of powdered solid electrolyte in a dry room with a dew point of approximately -40°C for about 12 hours, then collecting it and measuring its impedance, such as ionic conductivity.

[0063] The at% ratio of sulfur to phosphorus can be confirmed through EDS component mapping results. Specifically, the reduction rate means ((ionic conductivity after atmospheric exposure - ionic conductivity before atmospheric exposure) / (ionic conductivity before atmospheric exposure)) × 100 [%].

[0064] [Table 1]

[0065] As can be seen in Table 1, the ionic conductivity of the solid electrolyte of the present invention is in the range of 3.1 to 9.0 mS / cm before exposure to air, and as can be seen in Examples 1 to 6, it can be confirmed that the ionic conductivity increases as the amount of Li3PO4 added increases. Specifically, compared to the ionic conductivity before exposure to air, it can be confirmed that the ionic conductivity decreases as the amount of Li3PO4 added increases, and through the ionic conductivity and reduction rate after exposure to air, it can be confirmed that the reduction rate of ionic conductivity decreases as the amount of Li3PO4 added increases. Since the reduction rate of ionic conductivity decreases, it can be confirmed that the degree of air stabilization improves as the amount of Li3PO4 added increases. The electrical conductivity may fluctuate depending on the particle size, and the electrical conductivity may change during the pulverization process, so the examples of the present invention do not limit the present invention. Specifically, the solid electrolyte may have a reduction rate of ionic conductivity of 35% or less after exposure to air compared to before exposure to air. The aforementioned solid electrolyte satisfies the requirement that the reduction rate of ion conductivity is 35% or less when comparing before and after exposure to the atmosphere, thereby solving the problem of difficulty in handling in general atmospheric conditions due to side reactions with moisture, and providing a solid electrolyte with improved moisture stability without deterioration of ionic conductivity and cell performance.

[0066] The present invention is not limited to the above-described examples and / or embodiments, and can be manufactured in a variety of different forms. A person with ordinary skill in the art to which the present invention belongs will understand that the invention can be carried out in other specific forms without altering the technical idea or essential features of the invention. Therefore, the above-described examples and / or embodiments should be understood in all respects as illustrative and not limiting.

Claims

1. Some of the halogen elements are doped with oxygen, An argyrodite-type solid electrolyte having the composition Li (xy - x - 5y + 7) P (1 - y) S (xy - x - 5y + 6) Cl x - xy O 4y (1 ≤ x ≤ 2, 0.01 ≤ y ≤ 0.3).

2. A solid electrolyte according to claim 1, satisfying the following formula 1. <Formula 1> 3.5≦[S] / [P]≦4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.)

3. The solid electrolyte according to claim 1, wherein the XRD peak values ​​have diffraction peaks at 2θ = 15.5° ± 0.5°, 2θ = 18° ± 0.5°, 2θ = 25.5° ± 0.5°, 2θ = 30.2° ± 0.5°, and 2θ = 31.5° ± 0.5° deg.

4. Steps include preparing lithium raw materials, sulfur raw materials, halogen raw materials, and doping raw materials; The step of mixing the raw materials; and The step includes heat treatment of the result obtained by mixing, The aforementioned doping material is a raw material containing oxygen, A method for producing an argyrodite-type solid electrolyte, where Li (xy - x - 5y + 7), P (1 - y), S (xy - x - 5y + 6), Cl x - xy, O 4y (1 ≤ x ≤ 2, 0.01 ≤ y ≤ 0.3).

5. The method for producing an argyrodite-type solid electrolyte according to claim 4, wherein the doping raw material substance includes a phosphate compound.

6. The phosphate compound is Li ３ PO ４ 、Li ４ SiO ４ 、Li ４ GeO ４ 、Li ３ BO ３ 、and Li ３ AlO ３ The method for producing an aldite-type solid electrolyte according to claim 5, comprising at least one selected from the group consisting of

7. A method for producing an argyrodite-type solid electrolyte according to claim 6, wherein in the step of preparing the raw materials, 0.01 to 0.3 mol% of the phosphate compound is added to a standard of 100 mol% of the solid electrolyte.

8. The lithium raw material is Li ２ It is S, The aforementioned sulfur raw material is P ２ S ５ And, The method for producing an argyrodite-type solid electrolyte according to claim 4, wherein the halogen raw material is LiCl.

9. The method for producing an argyrodite-type solid electrolyte according to claim 4, wherein the solid electrolyte satisfies the following formula 1. <Formula 1> 3.5≦[S] / [P]≦4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.)

10. Positive electrode containing positive electrode active material; A negative electrode containing a negative electrode active material; and A solid electrolyte located between the positive and negative electrodes; The solid electrolyte is of the argyrodite type, in which some of the halogen elements are doped with oxygen, and has the composition Li (xy-x-5y+7) P (1-y) S (xy-x-5y+6) Cl x-xy O 4y (1≦x≦2, 0.01≦y≦0.3), and is a lithium secondary battery.

11. The lithium secondary battery according to claim 10, wherein the solid electrolyte satisfies the following formula 1. <Formula 1> 3.5≦[S] / [P]≦4.1 (In formula 1 above, [S] and [P] represent at% of S and P, respectively.)

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