KR20190142572A - Sulfide-based Solid Electrolytes and All-Solid-State Lithium-Ion Secondary Batteries Including the Same - Google Patents

Abstract

Disclosed are a novel sulfide-based solid electrolyte and an all-solid lithium ion secondary battery containing the same. By introducing a specific element to a crystal structure of the existing sulfide-based solid electrolyte, it is possible not only to secure good lithium ion conductivity even at high temperatures, but also to have improved atmospheric stability.

Description

Sulfide-based Solid Electrolytes and All-Solid-State Lithium-Ion Secondary Batteries Including the Same}

The present disclosure relates to a sulfide-based solid electrolyte and an all solid lithium ion secondary battery containing the same. More specifically, the present disclosure not only shows good lithium ion conductivity even at high temperature by introducing a specific element into the crystal structure of an existing sulfide-based solid electrolyte, but also a novel sulfide-based solid electrolyte and an all-solid type containing the same having improved atmospheric stability. It relates to a lithium ion secondary battery.

BACKGROUND With the widespread use of small electronic devices and electric vehicles, interest in secondary batteries having high energy density is increasing. Lithium-ion secondary batteries using lithium ions as secondary batteries are widely used in applications ranging from small mobile device power supplies to medium and large electric vehicles (eg, EV, HEV, etc.) and energy storage devices (ESS). There is a trend. In particular, interest in electric vehicles, which are eco-friendly vehicles, is increasing very much, and major automobile companies around the world are accelerating the development of related technologies by recognizing battery vehicles as the next-generation growth technology under the motto of eco-friendliness.

In the case of such a medium-large Li-ion secondary battery, unlike small size, not only the harsh operating environment (for example, temperature and impact), but also includes a large number of batteries, it is essential to ensure safety. As the industrial field requiring a lithium ion secondary battery expands to an application range for large batteries, interest in the safety-related problems of the lithium ion secondary battery also increases significantly.

In the conventional lithium ion secondary battery, since a nonaqueous electrolyte in which lithium salt is dissolved in an organic solvent, that is, an organic liquid electrolyte is used, strict packaging due to low thermal stability, ignition phenomenon, and leakage of liquid electrolyte occurs. This is required, and accordingly, there is a technical limitation that it is difficult to increase the energy density above a certain level. In fact, explosion accidents of products using lithium-ion secondary batteries have been reported continuously. Therefore, it is urgent to solve these safety-related problems.

In order to solve the problems caused by the above-mentioned liquid electrolyte, all-solid-state lithium ion secondary batteries using a solid electrolyte made of an inorganic material which is a non-combustible material have emerged as an alternative. Although sulfides, oxides, and the like can be used as solid electrolytes of all-solid-state lithium ion secondary batteries, sulfide-based solid electrolytes are considered to be the most potent materials in terms of conductivity of lithium ions.

In order to express the performance of such an all-solid-state lithium ion battery, it is necessary to have good contact characteristics between the solid electrolyte on which it is based and the positive electrode active material particles. The reaction occurs at the interface between the solid electrolyte and the positive electrode active material particles during charging, because insufficient contact increases the interface resistance (that is, resistance when lithium ions move through the interface between the positive electrode active material particles and the solid electrolyte particles). Therefore, when the interface resistance increases, the conductivity of lithium ions decreases, so that the output of the all-solid-state lithium ion secondary battery decreases. Sulfide-based solid electrolytes (eg, Li _x PS _y , Li _x M _y S _z, etc.) are better than oxide-based solid electrolytes (eg, Li _x La _y TiO ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ ). Due to the ductile properties, the particle characteristics can lead to intimate contact between the solid electrolyte and the positive electrode active material particles even by cold pressing, and thus have an advantage of obtaining an all-solid-state battery having excellent lithium ion conductivity. have.

In this regard, sulfide-based solid electrolytes having various compositions have been developed. For example, in Korean Patent No. 1392689, lithium (Li), M (for example, Ge and P), and sulfur (S) are contained. Sulfide-based solid electrolytes, and Korean Patent Publication No. 2016-0032664 include at least sulfur and lithium, phosphorus (P), silicon (Si), boron (B), aluminum (Al), germanium (Ge), zinc A sulfide-based solid electrolyte further comprising at least one selected from (Zn), gallium (Ga), indium (In), and a halogen element is disclosed. In addition, Korean Patent No. 1506109 discloses a sulfide-based solid electrolyte comprising Li, A (A is at least one of P, Si, Ge, Al and B), X (X is halogen) and S. have.

However, since the reported sulfide-based solid electrolyte has a problem in that the atmospheric stability is lower than that of the oxide-based solid electrolyte, it causes a serious problem in the manufacturing process of the all-solid-state lithium ion secondary battery, and furthermore, hydrogen sulfide and Emissions of such harmful gases can potentially cause environmental pollution.

In order to solve the above problems, various studies have been conducted on sulfide-based solid electrolytes, and as an example, a material represented by Li ₄ SnS ₄ has been reported to improve atmospheric stability.

However, since Li ₄ SnS ₄ exhibits low lithium ion conductivity, attempts have been made to replace Sn sites with As or to add LiI in an amorphous state by using a solution process, but the toxicity of the substitution elements, and / or Due to the decrease in ionic conductivity at high temperature, the above-mentioned sulfide-based solid electrolyte is still a problem in the process of applying or manufacturing the all-solid-state battery. Accordingly, there is a need for a method that overcomes the limitations of the prior art.

In one embodiment of the present disclosure can provide excellent atmospheric stability while eliminating the substitution of toxic elements in the sulfide-based solid electrolyte material, furthermore can maintain the crystalline because no solvent is used during the manufacturing process is good even at high temperatures An object of the present invention is to provide a sulfide-based solid electrolyte and a method of manufacturing the same, which may exhibit lithium ion conductivity.

Another embodiment of the present disclosure is to provide an all-solid-type lithium ion secondary battery comprising the sulfide-based solid electrolyte described above.

According to the first aspect of the present disclosure, represented by the following Chemical Formula 1, an XRD peak appears in a range of 2θ of 16 to 18 °, a range of 25 to 27 °, and a range of 44 to 46 °, respectively, A sulfide-based solid electrolyte is provided which exhibits a split peak of the XRD peak in the range of 25 to 27 °:

[Formula 1]

Li _a M _1b M _2c S _d X _e (2 <a <4, 0 <b <1, 0 <c <1, 0 ≦ d ≦ 4, and 0 ≦ e ≦ 4)

Wherein M ₁ is Sn, Si, Ge or Pb,

M ₂ is Sb or Bi,

X is F, Cl, Br, I, Se, or Te.

According to the second aspect of the present disclosure, as a method for producing a sulfide-based solid electrolyte represented by the following formula (1),

a) pulverizing a raw material comprising lithium element, M ₁ element, M ₂ element, elemental sulfur and element X under inert atmosphere; And

b) heat-treating the pulverized product obtained in step a) under vacuum;

Including;

XRD peaks appear in the range 2θ is 16-18 °, 25-27 °, and 44-46 °, and split peaks of the XRD peak are in the range 25-27 °. Method for preparing sulfide solid electrolyte:

 [Formula 1]

Li _a M _1b M _2c S _d X _e (2 <a <4, 0 <b <1, 0 <c <1, 0 ≦ d ≦ 4, and 0 ≦ e ≦ 4)

Wherein M ₁ is Sn, Si, Ge or Pb,

M ₂ is Sb or Bi,

X is F, Cl, Br, I, Se, or Te.

According to the third aspect of the present disclosure, there is provided a lithium ion secondary battery comprising the sulfide-based solid electrolyte described above.

According to one embodiment, the sulfide-based solid electrolyte may be orthorhombic, and the space group may have a crystal structure belonging to Pnma.

According to one embodiment, the lithium ion conductivity at 30 ° C. of the sulfide-based solid electrolyte may be at least 1.0 × 10 ⁻⁴ S / cm.

According to an embodiment of the present disclosure, it is possible to provide a sulfide-based solid electrolyte having a good lithium ion conductivity while having excellent atmospheric stability compared to a conventional sulfide-based solid electrolyte. In addition, by including the sulfide-based solid electrolyte, there is an advantage that can manufacture an all-solid-state lithium ion secondary battery having high safety and good battery performance compared to the case of applying an organic liquid electrolyte.

1 is a graph showing an X-ray diffraction peak with a change of x in Li _4-x Sn _x-1 Sb _x S ₄ , a sulfide-based solid electrolyte prepared according to Example 1;
2 is a view schematically showing an example of an apparatus for measuring the ion conductivity of a sulfide-based solid electrolyte prepared in Example 1; And
Figure 3 is a graph showing the result of measuring the ion conductivity according to the change of x in Li _4-x Sn _x-1 Sb _x S _{4 which} is a sulfide-based solid electrolyte prepared according to Example 1.

The present invention can be achieved by the following description. The following description is to be understood as describing preferred embodiments of the invention, but the invention is not necessarily limited thereto. In addition, the accompanying drawings are for ease of understanding, and the present invention is not limited thereto. Details of individual components may be appropriately understood by specific gist of the related description to be described later.

"Solid electrolyte" means a solid electrolyte capable of transferring ions therein, and since it is solid in a steady state, it is usually not dissociated or liberated with cations and anions. Therefore, it is also distinguished from an electrolyte salt (LiPF ₆ , LiBF ₄ , LiFSI, LiCl, etc.) in which cations and anions are dissociated or released in an electrolyte solution or a polymer.

"Sulfide-based solid electrolyte" is a kind of inorganic solid electrolyte, which may include sulfur (S), and also have ionic conductivity of a metal belonging to group 1 or group 2 of the periodic table, and may also have electronic insulation. .

When "includes" any component, this means that it can further include other components, unless stated otherwise.

Sulfide solid electrolyte

Sulfide-based solid electrolyte according to the present disclosure is represented by the following formula (1).

[Formula 1]

Li _a M _1b M _2c S _d X _e (2 <a <4, 0 <b <1, 0 <c <1, 0 ≦ d ≦ 4, and 0 ≦ e ≦ 4)

Wherein M ₁ is Sn, Si, Ge or Pb,

M ₂ is Sb or Bi,

X is F, Cl, Br, I, Se, or Te.

According to an exemplary embodiment, the proportion of member elements in the compound according to Formula 1 may be 3 <a <4, 0 <b <1, 0 <c <0.5, 0 ≦ d ≦ 4, and 0 ≦ e ≦ 4 have.

According to another exemplary embodiment, the proportion of member elements in the compound according to Formula 1 is 3.5 <a <4, 0.5 <b <1, 0.1 <c <0.5, 2 ≦ d ≦ 4, and 0 ≦ e ≦ 4 days Can be.

In particular, as a result of XRD analysis, the sulfide-based solid electrolyte according to an embodiment of the present disclosure has an XRD peak in a range of 2 to 16 to 18 degrees, a range of 25 to 27 degrees, and a range of 44 to 46 degrees, respectively. And split peaks of the XRD peak appear in the range of 25 to 27 °.

The above-mentioned compounds are compared with sulfide compounds known to have good properties in recent years, specifically, compounds consisting of lithium element, M element (for example, tin or germanium), phosphorus (P) element, sulfur (S) element and halogen element. It offers the advantage of increasing the ionic conductivity, in particular the ionic conductivity of lithium ions. Although the present invention is not limited to a specific theory, the reason for exhibiting such improved characteristics can be explained as follows.

In all-solid-state cells, ion transport in solid electrolytes generally depends on the concentration and distribution of defects. Ion diffusion mechanisms based on Schottky and Frenkel point defects include simple Vacancy mechanisms and relatively complex diffusion mechanisms (eg, divacancy mechanisms). , Interstitial mechanisms, interstitial-substitutional exchange mechanisms, and collective mechanisms. To achieve fast ion conductivity, three initial criteria must be met: (i) the number of equivalent sites that mobile ions can occupy is much greater than the number of mobile species, and (ii) adjacent sites. The migration barrier energy of the liver must be low enough to allow ions to jump from one site to another, and (iii) these sites must be connected to form a continuous diffusion path.

In this regard, M ₁ is an element that determines the basic crystal structure of the sulfide-based solid electrolyte, orthorhombic, and the space group may provide a crystal structure belonging to Pnma. On the other hand, M ₂ affects the lattice size in the crystal structure affected by M ₁ of the sulfide-based solid electrolyte, and allows lithium ions to move easily by changing the distance between the crystal lattice.

In particular, in the case of the sulfide-based solid electrolyte according to the present disclosure, by introducing M ₂ in the crystal structure affected by M ₁ causes cracking in the range of 25 to 27 ° of the XRD peak to determine the lattice parameter; Increasing the size of the unit cell in the lattice, resulting in a significant increase in the ion conductivity of lithium ions.

In addition, in the conventional sulfide-based solid electrolyte, phosphorus (P) element is an element that improves the ionic conductivity, but has an unstable characteristic in the air, and thus may degrade the performance of the electrolyte during the preparation of the solid electrolyte. And the need to maintain an inert atmosphere in many manufacturing facilities, which increases the investment cost for the process equipment. In addition, hydrogen sulfide may be generated due to low atmospheric stability, which may cause problems of air pollution.

However, in the sulfide-based solid electrolyte according to the present disclosure, the atmospheric stability can be improved by introducing antimony (Sb) or bismuth (Bi) into the crystal structure as the M ₂ element instead of containing the phosphorus element. As a result, in the process of applying to a variety of objects using the compound according to formula 1 can be carried out in a general dryer, it is possible to minimize the generation of hydrogen sulfide.

According to an exemplary embodiment, the average particle diameter of the sulfide-based solid electrolyte may be, for example, in the range of about 0.1 to 50 μm, specifically about 1 to 30 μm, more specifically about 5 to 20 μm.

In an exemplary embodiment, the lithium ion conductivity (30 ° C.) of the sulfide-based solid electrolyte described above is, for example, at least about 1.0 × 10 ⁻⁴ S / cm, specifically at least about 1.0 × 10 ⁻³ / cm, more Specifically at least about 3 × 10 ⁻³ S / cm. It is noteworthy that such ion conductivity is significantly higher than that when M ₂ is not contained as a conventional sulfide-based solid electrolyte compound.

Method for preparing sulfide solid electrolyte

According to one embodiment of the present disclosure, the sulfide-based solid electrolyte according to Chemical Formula 1 may be prepared without using a solvent, and will be described in detail below.

First, a raw material including lithium element, M ₁ element, M ₂ element, sulfur element, and X element (optional component) constituting the compound according to Formula 1 is formed.

Lithium element

The elemental lithium can be provided from a lithium source known in the art, typically Li ₂ S, Li ₂ S ₈ , Li ₂ S ₆ , Li ₂ S ₄ , Li ₂ S ₂ , Li ₂ S or combinations thereof In particular, it may be advantageous to use Li ₂ S, more specifically, high purity Li ₂ S containing no impurities as possible. In addition to the above-mentioned lithium sulfide-based sources, the use of Li ₄ SiO ₄ , Li ₄ GeO _4, etc. is not excluded. However, as long as the source to which lithium and sulfur are bonded (specifically, Li ₂ S) does not contain oxygen, It may be preferred as a source of elemental lithium.

M _One  element

In one embodiment, the M ₁ element may be used in the form of a compound or precursor known in the art as Sn, Si, Ge or Pb.

Examples of the source of tin element may include SnS ₂ , SnF ₄ , SnCl ₄ , SnBr ₄ , SnI ₄ , SnF ₂ , SnCl ₂ , SnBr ₂ , SnI ₂ , and the like, and may be used alone or in combination. Can be. Preferably SnS ₂ can be used.

The source of the silicon element may be, for example, SiS ₂ , SiF ₄ , SiCl ₄ , SiBr ₄ , SiBrCl ₃ , SiBr ₂ Cl ₂ , SiI _4, or the like, and one or two of these may be used in combination. However, considering the synthesis reaction and the composition of the final product, it may be advantageous to use SiS ₂ .

As a source of germanium element, for example, _{GeS 2, GeF 4, GeCl 4} , GeBr 4, GeI 4 , etc. can be mentioned, can be used alone or in combination of two or more of them. However, it may be preferable to use GeS ₂ .

In the case of a source of lead element, PbS ₂ , PbF ₄ , PbCl ₄ , PbBr ₄ , PbI ₄ , and the like can be exemplified, and one or two of them can be used in combination. However, it may be preferable to use PbS ₂ .

M ₂  element

In one embodiment, the M ₂ element may be used in the form of a compound or precursor known in the art as Sb or Bi.

Examples of sources of antimony elements may include Sb ₂ S ₃ , Sb ₂ S ₅ , SbF ₃ , SbCl ₃ , SbBr ₃ , SbI ₃ , SbF ₅ , SbCl _5, or a combination thereof. More specifically, it may be Sb ₂ S ₃ , Sb ₂ S ₅ , or a combination thereof.

As a source of the bismuth element, for example, Bi ₂ S ₃ , BiF ₃ , BiCl ₃ , BiBr ₃ , BiI ₃ or a combination thereof may be used, more specifically, Bi ₂ S ₃ .

Elemental sulfur

According to an exemplary embodiment, the elemental sulfur may be provided alone (ie, in the form of elemental sulfur (S ₈ )) or in combination with other elements (lithium, M ₁ and / or M ₂ ). Specific examples of such sulfur sources will be omitted as described above.

X element

In this embodiment, the element X may be halogen (F, Cl, Br, or I), Se, or Te.

In this regard, the source of the halogen element may be provided in a form combined with other elements (lithium, M ₁ and / or M ₂ ) as described above. Examples of this type of halogen source are omitted as described above.

On the other hand, in the case of the element selenium, typically may be SeS ₂ , SeF ₄ , Se ₂ F ₆ , Se ₂ Cl ₂ , SeBr ₂ , SeI _2, etc., one or two of these may be used in combination. More specifically, it may be SeS ₂ .

Further, examples of the tellurium element source may be TeS, Te ₂ S ₆ , TeF ₄ , Te ₂ F ₁₀ , TeF ₆ , TeCl ₂ , TeCl ₄ , TeBr ₂ , TeBr ₄ , TeI _4, or a combination thereof. More specifically, TeS, Te ₂ S ₆ or a combination thereof may be used.

Then, as described above, the source of the element corresponding to the formula (1) is added in an appropriate amount in consideration of the desired ratio (that is, the ratio between the elements specified in the formula 1), and it is pulverized to form a raw material pulverized product. At this time, the grinding process may be performed under an inert atmosphere, for example, it may use nitrogen, helium, neon, argon, or a mixed gas thereof. When pulverizing in the atmosphere, it may be advantageous to pulverize while maintaining an inert atmosphere, as oxygen may be partially mixed in the pulverizing process to partially form oxides in the final product.

Meanwhile, in the grinding process, the raw material may be pulverized by using mechanical milling (specifically, high energy mechanical milling), and all of the above-described sources of the elements may be put in a crushing apparatus in one step, and may be milled. A plurality of raw material sources may be added first to be pulverized, and then the remaining raw material sources may be pulverized in a sequential or additional manner to be milled. At this time, the temperature in the milling process is not particularly limited, for example, may be in the range of about 10 to 40 ℃, specifically about 15 to 30 ℃, more specifically about 20 to 25 ℃.

Then, the raw pulverized product is heat treated to induce a reaction. According to an exemplary embodiment, the reaction can be carried out under vacuum, for which the inert atmosphere can be replaced by a vacuum atmosphere in such a way as to seal after removing the previously supplied inert gas through a suction process. Thereafter, the pulverized product may be converted to a sulfide-based solid electrolyte according to Chemical Formula 1 by heating under elevated temperature. In this case, the heat treatment temperature may be, for example, about 400 to 800 ° C, specifically about 500 to 700 ° C, and more specifically about 520 to 600 ° C. In addition, the heat treatment time may be selected, for example, within the range of about 5 to 30 hours, specifically about 8 to 25 hours, more specifically about 10 to 15 hours.

The above heat treatment conditions may be suitably adjusted so that the sulfide-based compound formed preferably has a single crystal, for example, first about 5 to 30 ° C./h (specifically about 10 to 25 ° C./h, more specifically about 15 to The temperature is maintained after the temperature is raised to the heat treatment temperature at a temperature increase rate of 20 ° C./h, followed by a constant cooling rate (eg, about 2 to 10 ° C./h, specifically about 3 to 7 ° C./h, more specifically To about 4 to 6 ° C./h).

Fabrication of all-solid lithium ion secondary battery

According to another embodiment of the present disclosure, an all-solid-state lithium ion secondary battery may be manufactured by applying a sulfide-based compound of Formula 1 prepared as described above as an electrolyte. The configuration of such an all-solid-state lithium ion secondary battery is known in the art, components other than the solid electrolyte can be briefly described as follows.

First, in the case of an all-solid-state lithium ion secondary battery, the above-mentioned sulfide type between the positive electrode active material layer attached to a cathode, the negative electrode active material layer attached to an anode, and the positive electrode active material layer and the negative electrode active material layer A solid electrolyte layer is interposed.

It is preferable that the positive electrode active material can reversibly insert and release lithium ions. It does not specifically limit as a material of such a positive electrode active material, It may be an element which can be compounded with Li, such as a transition metal oxide and sulfur. Especially, a transition metal oxide can be used and one or more types of elements chosen from Co, Ni, Fe, Mn, Cu, V can be illustrated as such a transition metal element.

Examples of the transition metal oxide include a transition metal oxide having a layered rock salt structure, a spinel transition metal oxide, a lithium-containing transition metal phosphate compound, a lithium-containing transition metal halide phosphate compound, a lithium-containing transition metal silicon compound, and the like. Can be.

In this connection, as a transition metal oxide having a layered rock salt structure, LiCoO ₂ (LCO), LiNi ₂ O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ (NCA), LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (NMC), LiNi _0.5 Mn _0.5 O can be illustrated. Examples of the spinel transition metal oxide include LiCoMnO ₄ , Li ₂ FeMn ₃ O ₈ , Li ₂ CuMn ₃ O ₈ , Li ₂ CrMn ₃ O ₈ , and Li ₂ NiMn ₃ O ₈ . In addition, examples of the lithium-containing transition metal phosphate compound may include LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , LiFeP ₂ O ₇ , LiCoPO ₄ , and Li ₃ V ₂ (PO ₄ ) ₃ , and lithium As the -containing transition metal halide phosphoric acid compound, for example, Li ₂ FePO ₄ F, Li ₂ MnPO ₄ F, Li ₂ CoPO ₄ F and the like can be exemplified. In addition, examples of the lithium-containing transition metal silicon compound include Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO ₄ , and the like.

In the case of the negative electrode active material, it is preferable that lithium ions can be reversibly inserted and released. The material of the negative electrode active material is not particularly limited, and examples thereof include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium or lithium alloys. More specifically, carbonaceous materials or lithium composite oxides can be used.

In this regard, the carbonaceous material is substantially a material made of carbon, for example, petroleum pitch, carbon black such as acetylene black (AB), artificial graphite such as natural graphite, vapor-grown graphite, and PAN (polyacrylonitrile). Carbonaceous materials which baked various synthetic resins, such as a reel) type resin and a furfuryl alcohol resin, can be illustrated. Moreover, various carbon fibers, such as PAN type | system | group carbon fiber, cellulose type carbon fiber, pitch type carbon fiber, vapor-growth carbon fiber, lignin carbon fiber, glassy carbon fiber, and activated carbon fiber, a graphite of a flat plate, etc. can be illustrated.

As the metal oxide and the metal complex oxide, in particular, an amorphous oxide can be used, and chalcogenide, which is a reaction product of a metal element and an element of group 16 of the periodic table, can also be used. In the compound consisting of such an amorphous oxide and chalcogenide, an amorphous oxide of a semimetal element or chalcogenide can be used, and more specifically, one of Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi. Oxides composed of single or a combination thereof and chalcogenide can be used, for example Ga ₂ O ₃ , SiO, GeO, SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , SnSiO ₃ , GeS, SnS, SnS ₂ , PbS, PbS ₂ , Sb ₂ S ₃ , Sb ₂ S ₅ , SnSiS ₃ and the like can be used.

Meanwhile, the all-solid-state lithium ion secondary battery may include a current collector, and an electronic conductor may be used as a material of the current collector. In the case of the current collector of the positive electrode, aluminum, stainless steel, nickel, titanium, or the like may be used, and in addition, it may be advisable to treat carbon, nickel, titanium, or silver on the surface of aluminum or stainless steel. On the other hand, aluminum, copper, stainless steel, nickel, titanium, etc. can be used as an electrical power collector of a negative electrode. The shape of the current collector may be typically in the form of a film, but a network structure, a punching structure, a porous body, a foam, or the like may also be applied. By way of example, the thickness of the current collector may be in the range of, for example, about 1 to 300 μm, specifically about 10 to 250 μm, more specifically about 50 to 200 μm, but this may be understood in an exemplary sense.

Hereinafter, preferred examples are provided to aid in understanding the present invention, but the following examples are provided only for better understanding of the present invention, and the present invention is not limited thereto.

Example 1

Li ₂ S, SnS ₂ , Sb ₂ S ₃ , S and Sb ₂ S ₅ were each put into a milling apparatus, and after forming an argon atmosphere in the glovebox, they were ground. Thereafter, the raw material pulverized product was put in a silica ampoule and sealed after applying a vacuum. Thereafter, the raw material pulverized product was heat treated using a gas burner, wherein the heat treatment temperature was 550 ° C., and the heat treatment time was 12 hours. A sulfide-based solid electrolyte represented by Li _4-x Sn _x-1 Sb _x S ₄ was prepared through the above-described heat treatment.

XED analysis was performed on the prepared sulfide-based solid electrolyte, and the XRD peak characteristics according to the change of x are shown in FIG. 1.

Referring to FIG. 1, when x = 0 (that is, when M ₂ is not introduced into the crystal structure in Chemical Formula 1), a peak is detected in a range of 25 to 27 °, but no crack is found and a smooth peak shape is observed. Indicated. However, as x increased to 0.1, the detected peak in the range of 25 to 27 ° showed a cracked form, and this cracked peak was found even when x increased to 0.15, 0.167, 0.2 and 0.3.

In order to measure the ionic conductivity of the prepared sulfide-based solid electrolyte, as shown in FIG. 2, an ion conductivity measuring apparatus was manufactured by itself, and the ionic conductivity according to the change of x was measured. The results are shown in FIG.

According to FIG. 3, the ion conductivity continuously increased until it gradually increased at x = 0 and reached 0.2. However, when x increased to 0.3, the ionic conductivity decreased slightly, but this was significantly higher than when x was 0 (that is, when M ₂ was not introduced into the crystal structure).

Therefore, in the sulfide-based solid electrolyte containing lithium, tin and sulfur, it can be seen that the mobility of lithium ions was significantly increased by introducing antimony into the lattice structure.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (1)

The XRD peak is represented by the following Chemical Formula 1, wherein 2θ is in the range of 16 to 18 °, in the range of 25 to 27 °, and in the range of 44 to 46 °, respectively, and in the range of 25 to 27 °. Sulfide-based solid electrolytes with split peaks:
[Formula 1]
Li _a M _1b M _2c S _d X _e (2 <a <4, 0 <b <1, 0 <c <1, 0 ≦ d ≦ 4, and 0 ≦ e ≦ 4)
Wherein M ₁ is Sn, Si, Ge or Pb,
M ₂ is Sb or Bi,
X is F, Cl, Br, I, Se, or Te.

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