Solid electrolyte and lithium secondary battery containing the same

Abstract

The present invention relates to a sulfide-based solid electrolyte containing lithium (Li), phosphorus (P), sulfur (S) and a halogen element, having an argyrodite-based crystal structure, at least a portion of which is doped with one or more first doping elements selected from the Group 13 elements and one or more second doping elements selected from the Group 14 elements.

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte and a lithium secondary battery containing the same. [Background technology]

[0002] With research into the safety issues and energy density of high-capacity batteries gaining attention, solid-state batteries are gaining attention as the next generation of batteries.

[0003] The all-solid-state battery replaces the liquid electrolyte, which is prone to explosion, with a solid electrolyte, and therefore does not use a flammable solvent inside the battery. This means that no fire or explosion occurs due to reactions such as the decomposition reaction of conventional electrolytes, and therefore the safety of the battery is ensured.

[0004] Furthermore, since lithium metal or a 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.

[0005] The solid electrolyte used in the all-solid-state battery is generally an inorganic solid electrolyte, and various researches are being conducted on sulfide-based solid electrolytes having a composition such as Li6PS5Cl, which has an argyrodite structure among the all-solid-state batteries.

[0006] However, when the sulfide-based solid electrolyte is used in a cell, it generally has a problem of having lower lithium ion conductivity and inferior electrochemical properties of the battery compared to the liquid electrolytes used in conventional commercial lithium ion batteries. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a sulfide-based solid electrolyte that can achieve excellent ionic conductivity or improve the electrochemical properties of a battery, and a lithium secondary battery including the same. [Means for solving the problem]

[0008] One embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element, and having an argyrodite-based crystal structure, at least a portion of which is doped with one or more first doping elements selected from the Group 13 elements and one or more second doping elements selected from the Group 14 elements.

[0009] The first doping element may be at least one selected from the group consisting of B, Al, Ga, In, and Ti, and the second doping element may be at least one selected from the group consisting of Si, Ge, and Sn.

[0010] In one embodiment, the first doping element may be In and the second doping element may be Si.

[0011] In this case, the solid electrolyte may contain the first doping element in an amount of 0.005 to 0.04 mol % based on the total number of moles of the solid electrolyte.

[0012] The solid electrolyte may contain the second doping element in an amount of 0.02 to 0.2 mol % based on the total number of moles of the solid electrolyte.

[0013] The solid electrolyte may be represented by the following Chemical Formula 1: [Chemical formula 1] Li 6(1-x-y) In x Si y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y In the above formula 1, C is at least one of F, Cl, Br and I, <x<0.5であり、0.05<y<0.5である。

[0014] In another embodiment, the first doping element may be B and the second doping element may be Si.

[0015] In this case, the solid electrolyte may be represented by the following Chemical Formula 2: [Chemical formula 2] Li 6(1-x-y) B x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4 In the above formula 2, D is F, Cl, Br, I or a combination thereof, 0.014≦x≦0.05, and 0.04≦y≦0.4.

[0016] The x may be in the range of 0.02≦x≦0.035.

[0017] The y may be in the range of 0.08≦y≦0.25.

[0018] In yet another embodiment, the first doping element may be B and the second doping element may be Sn.

[0019] In this case, the solid electrolyte may be represented by the following Chemical Formula 3: [Chemical formula 3] Li 6(1-x-y) B x Sn y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the above formula 3, D is F, Cl, Br, I or a combination thereof, 0.013≦x≦0.043, and 0.04≦y≦0.42.

[0020] The x may be in the range of 0.02≦x≦0.035.

[0021] The y may be in the range of 0.08≦y≦0.17.

[0022] In yet another embodiment, the first doping element may be Al and the second doping element may be Si.

[0023] In this case, the solid electrolyte may be represented by the following Chemical Formula 4. [Chemical formula 4] Li 6(1-x-y) Al x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the above formula 4, D is F, Cl, Br, I or a combination thereof, 0.01≦x≦0.05, and 0.1≦y≦0.4.

[0024] The x may be 0.02≦x≦0.045.

[0025] The y may be in the range of 0.15≦y≦0.35.

[0026] In yet another embodiment, the first doping element may be B and the second doping element may be Ge.

[0027] In this case, the solid electrolyte may contain the first doping element in an amount of 0.02 to 0.04 mol % based on the total number of moles of the solid electrolyte.

[0028] The solid electrolyte may contain the second doping element in an amount of 0.1 to 0.3 mol % based on the total number of moles of the solid electrolyte.

[0029] The solid electrolyte may be represented by the following Chemical Formula 5: [Chemical formula 5] Li 6(1-x-y) B x Ge y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y In the above formula 5, C is at least one of F, Cl, Br and I, and <x<0.04であり、0.1<y<0.3である。

[0030] Another embodiment of the present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer located between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte layer comprises the above-described solid electrolyte.

[0031] Another embodiment of the present invention provides an electric vehicle including the lithium secondary battery. [Effects of the Invention]

[0032] A sulfide-based solid electrolyte according to an embodiment of the present invention has an argyrodite-based crystal structure, and at least a portion of the crystal structure is doped with one or more first doping elements selected from Group 13 elements and one or more second doping elements selected from Group 14 elements, thereby achieving excellent ion conductivity or improving the electrochemical properties of a battery. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows the results of XRD diffraction peak analysis according to Experimental Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0034] In describing the present invention, terms such as 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 only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may also be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0035] The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used in the specification, the term "comprising" means to embody certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0036] When a part is referred to as being "on" or "above" another part, this means that it is directly on top of the other part, or there may be other parts between them. In contrast, when a part is referred to as being "directly on top" of another part, there are no other parts between them.

[0037] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless otherwise defined.

[0038] Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0039] In this specification, the term "combination thereof" used in a Markush expression means a mixture or combination of one or more elements selected from the group of elements described in the Markush expression, and means including any one or more elements selected from the group of elements.

[0040] While the present invention may be embodied in many different forms, it is to be understood that the invention is not limited to the embodiments set forth herein.

[0041] [1. Solid electrolyte] One embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element, and having an argyrodite-based crystal structure, at least a portion of which is doped with one or more first doping elements selected from the Group 13 elements and one or more second doping elements selected from the Group 14 elements.

[0042] The first doping element may be at least one selected from the group consisting of B, Al, Ga, In, and Ti, and the second doping element may be at least one selected from the group consisting of Si, Ge, and Sn.

[0043] [First Example] In one embodiment, the first doping element may be In and the second doping element may be Si.

[0044] This will be explained in more detail below.

[0045] The solid electrolyte according to an embodiment of the present invention may be an argyrodite-type solid electrolyte containing a sulfate-based compound. The solid electrolyte is not a solid electrolyte interphase (SEI), which is a film formed at the interface of electrode materials during the initial charge-discharge reaction after battery fabrication, but rather a solid material having lithium (Li) ion conductivity that can be used as a substitute for an electrolyte solution and a separator when designing a battery.

[0046] The solid electrolyte of the present invention having the above composition is a sulfur-containing compound and may be a sulfide-based solid electrolyte. Specifically, the argyrodite-type may have an argyrodite-type structure containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element such as chlorine (Cl). The solid electrolyte may be in the form of particles or powder, and may be crystalline or amorphous.

[0047] In one embodiment, the argyrodite-type solid electrolyte may include a first compound and a second compound. In one embodiment, the first compound may be a compound containing a trivalent element, and the second compound may be a compound containing a tetravalent element. The trivalent element may be a Group 13 element on the periodic table, and the tetravalent element may be a Group 14 element on the periodic table.

[0048] The first compound and the second compound may contain at least one element of In, B, Al, Ga, Ti, Si, Ge, and Sn. Specifically, the first compound and the second compound may be at least one of an indium-based compound, a silicon-based compound, an aluminum-based compound, a boron-based compound, a gallium-based compound, a titanium-based compound, a germanium-based compound, and a tin-based compound.

[0049] In one embodiment, the first compound and the second compound may be different substances. Specifically, the first compound and the second compound may be compounds having different compositions. More specifically, the first compound may be an indium-based compound, and the second compound may be a silicon-based compound.

[0050] In this case, the solid electrolyte may contain the first doping element in an amount of 0.005 to 0.04 mol % based on the total number of moles of the solid electrolyte.

[0051] In addition, the solid electrolyte may include the second doping element in an amount of 0.02 to 0.2 mol % based on the total number of moles of the solid electrolyte.

[0052] That is, in one embodiment, the first compound may be included in a range of 0.005 to 0.04 mol %, more specifically, in a range of 0.01 to 0.03 mol %, and even more specifically, in a range of 0.02 to 0.03 mol %.

[0053] When the first compound satisfies the above range, a large number of voids due to a deficiency of lithium ions are generated, and an argyrodite-type solid electrolyte with excellent ionic conductivity can be obtained. When the first compound is outside the upper and lower limits of the above range, there is a problem in that the ionic conductivity decreases.

[0054] In one embodiment, the second compound may be included in a range of 0.02 to 0.3 mol %, more specifically, 0.1 to 0.2 mol %, and even more specifically, 0.1 to 0.15 mol %.

[0055] When the second compound satisfies the above range, a large number of voids due to a deficiency of lithium ions are generated, and an argyrodite-type solid electrolyte with excellent ionic conductivity can be obtained. When the second compound is outside the upper and lower limits of the above range, there is a problem in that the ionic conductivity decreases.

[0056] If the first compound and the second compound are out of the upper limit of the range, the argyrodite crystal structure cannot be formed, resulting in the presence of impurities.If the first compound and the second compound are out of the lower limit of the range, the ionic conductivity cannot be improved.

[0057] The argyrodite-type solid electrolyte has an advantage that the first compound and the second compound correspond to doping source materials, and the first compound and the second compound are simultaneously doped, thereby significantly improving ionic conductivity and thereby improving cell capacity characteristics.

[0058] In one embodiment, the argyrodite-type solid electrolyte is Li 6(1-x-y) A x B y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y can be satisfied.

[0059] In the solid electrolyte, A may be at least one of In, B, Al, Ga, and Ti.

[0060] The B may be at least one of Si, Ge, and Sn.

[0061] The C may be at least one of F, Cl, Br, and I.

[0062] where x is 0.1 <x<0.5であり、yは、0.05<y<0.5であってもよい。

[0063] In one embodiment, the Li 6(1-x-y) A x B y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y Li 6(1-x-y) In x Si y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y The argyrodite-type solid electrolyte contains a different element as a doping source material, which has the advantage of having superior ionic conductivity compared to a case where a single element is contained.

[0064] That is, the solid electrolyte may be represented by the following chemical formula 1: [Chemical formula 1] Li 6(1-x-y) In x Si y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y In the above formula 1, C is at least one of F, Cl, Br and I, <x<0.5であり、0.05<y<0.5である。

[0065] In one embodiment, the argyrodite-type solid electrolyte may have a peak intensity at a predetermined position in an X-ray diffraction pattern measured by an X-ray diffractometer (XRD). Specifically, the argyrodite-type solid electrolyte having the above composition may have an XRD peak at 2θ=30.25°±0.05°.

[0066] The presence of the diffraction peak value has the advantage of preventing the deterioration of the ionic conductivity and cell performance of the argyrodite-type solid electrolyte, whereas the absence of the diffraction peak value causes the problem of deviation from the argyrodite crystalline phase.

[0067] In one embodiment, the argyrodite-type solid electrolyte may have an ionic conductivity of 3.4 to 8.0 mS / cm or more. Specifically, the ionic conductivity may be 5.4 to 7.4 mS / cm or more. When the ionic conductivity satisfies this range, there is an advantage in that the cell capacity characteristics are improved.

[0068] A method for manufacturing an argyrodite-type solid electrolyte according to another embodiment of the present invention may include the steps of preparing a lithium source material, a sulfur source material, and a halogen source material; adding a first doping material and a second doping material to the prepared materials at 0.005 to 0.04 mol% and 0.02 to 0.3 mol%, respectively; mixing the resulting material with the doping materials added; and heat-treating the resulting mixture.

[0069] In the step of preparing a lithium source material, a sulfur source material, a halogen source material, and a doping source material, the lithium source material and the sulfur source material may be selected from known materials such as, but not limited to, LiS and LiS. More specifically, the lithium source material may be LiS.

[0070] The halogen source material may be a source material containing various halogen elements such as, but not limited to, F, Cl, and Br. Specifically, the halogen source material may be LiCl.

[0071] In the step of adding 0.005 to 0.05 mol% of a first doping material and 0.02 to 0.4 mol% of a second doping material to the prepared material, the first doping material and the second doping material may be added at 0.01 to 0.03 mol% and 0.1 to 0.2 mol%. More specifically, the first doping material and the second doping material may be added at 0.02 to 0.03 mol% and 0.1 to 0.15 mol%. When the contents of the first doping material and the second doping material satisfy the above ranges, a large number of voids due to a deficiency of lithium ions are generated, thereby increasing ionic conductivity.

[0072] If the contents of the first doping material and the second doping material are outside the upper limit of the range, the argyrodite phase may not be maintained and an impurity phase may be generated, whereas if the content of the first doping material is outside the lower limit of the range, the argyrodite phase may not be significantly different from the existing argyrodite phase.

[0073] In one embodiment, the first doping material and the second doping material may include at least one element selected from the group consisting of In, B, Al, Ga, Ti, Si, Ge, and Sn. Specifically, the first doping material and the second doping material may be at least one of an indium-based compound, a silicon-based compound, an aluminum-based compound, a boron-based compound, a gallium-based compound, a titanium-based compound, a germanium-based compound, and a tin-based compound.

[0074] In one embodiment, the first doping material and the second doping material may be different materials. Specifically, the first doping material and the second doping material may be compounds having different compositions. More specifically, the first doping material may be an indium-based compound such as InCl3, and the second doping material may be a boron-based compound such as SiCl4.

[0075] The step of mixing the resultant material after adding the doping material may be performed by mechanical mixing or chemical mixing. For example, the mechanical mixing may be performed using a paint shaker, ball mill, bead mill, homogenizer, hammer mill, or planetary mill, while the chemical mixing may be performed using a melt quenching method. Specifically, the step of mixing the raw materials may be performed using a planetary mill.

[0076] In one embodiment, the step of mixing the raw materials may be performed at a speed of 200 to 400 rpm.

[0077] The step of heat-treating the mixed resultant is a step of synthesizing the mixed resultant. In one embodiment, the step of heat-treating the mixed resultant may be performed at a temperature range of 400 to 700°C. Specifically, the temperature range may be 500 to 600°C.

[0078] If the temperature is outside the upper limit of the range, the argyrodite phase may not be formed and an impurity phase may be generated, whereas if the temperature is outside the lower limit of the range, the argyrodite phase may not be formed or may exist as an amorphous crystalline structure.

[0079] In one embodiment, the step of heat-treating the mixed resultant may be performed in an inert atmosphere, which may be a stable atmosphere such as Ar, N2, H2, or He. Specifically, the inert atmosphere of the present invention may be an Ar atmosphere.

[0080] The argyrodite-type all-solid-state electrolyte prepared through the above steps is Li 6(1-x-y) A x B y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y can be satisfied.

[0081] In the solid electrolyte, A may be at least one of In, B, Al, Ga, and Ti.

[0082] The B may be at least one of Si, Ge, and Sn.

[0083] The C may be at least one of Cl, Br, and I.

[0084] where x is 0.1 <x<0.5であり、yは、0.05<y<0.5であってもよい。

[0085] For example, when the first doping material of the present invention is the indium-based compound InCl3 and the second doping material is the silicon-based compound SiCl4, an all-solid-state electrolyte having the following chemical formula can be obtained. <chemical formula> (1-xy)Li6PS5Cl+xInCl3+ySiCl4→Li 6(1-x-y) In x Si y P (1-x-y) S 5(1-x-y) Cl 1+2x+3y

[0086] For a detailed description of the solid electrolyte of the present invention manufactured by the method for manufacturing a solid electrolyte according to an embodiment of the present invention, please refer to the above description.

[0087] [Second Example] In another embodiment, the first doping element may be B and the second doping element may be Si.

[0088] This will be explained in more detail below.

[0089] Another embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element, and having an argyrodite-based crystal structure, at least a portion of which is doped with boron (B) and silicon (Si), and the boron and silicon are doped independently of each other.

[0090] In a sulfide-based solid electrolyte according to one embodiment of the present invention, at least a portion of the crystal structure is doped with boron (B) and silicon (Si). Here, the boron and silicon are independently doped. In other words, the doping amounts of boron and silicon may be independently controlled. The sulfide-based solid electrolyte of the present invention has a basic argyrodite crystal structure, Li6PS5Cl, which is independently doped with boron and silicon, thereby generating numerous voids due to a deficiency of lithium ions. This results in the formation of diverse lithium ion paths (channels), significantly improving lithium ion conductivity and cell capacity characteristics.

[0091] The sulfide-based solid electrolyte according to another embodiment of the present invention may be represented by the following Chemical Formula 2: [Chemical formula 2] Li 6(1-x-y) B x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the above formula 2, D is F, Cl, Br, I or a combination thereof, 0.014≦x≦0.05, and 0.04≦y≦0.4.

[0092] Specifically, B (boron) and Si (silicon) are doping elements in the above chemical formula 2. In this specification, "doping" can mean not only replacing some elements of a compound with new elements, but also the doped element becoming a component of the crystalline phase of the compound.

[0093] In the formula 2, x represents the doping amount of boron, which is a doping element, in moles, and satisfies 0.014≦x≦0.05.

[0094] More specifically, x may be in the range of 0.02≦x≦0.035 or 0.023≦x≦0.032. An excessively small x may result in an excessively low boron doping amount, while an excessively large x may result in an excessively high boron doping amount. If the boron doping amount is too low, the composition may not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a poor doping effect, i.e., a poor increase in ionic conductivity. On the other hand, if the boron doping amount is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, impairing the smooth movement of lithium ions and ultimately resulting in a significantly reduced ionic conductivity. Therefore, when x satisfies the above range, excellent ionic conductivity can be achieved.

[0095] In addition, in the above Chemical Formula 2, y represents the doping amount of silicon, which is a doping element, in moles, and satisfies 0.04≦y≦0.4.

[0096] More specifically, y may be 0.08≦y≦0.25 or 0.09≦y≦0.22. An excessively small y may result in an excessively low silicon doping amount, whereas an excessively large y may result in an excessively high silicon doping amount. If the silicon doping amount is too low, the composition may not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a poor doping effect, i.e., a poor increase in ionic conductivity. On the other hand, if the silicon doping amount is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, impairing the smooth movement of lithium ions and ultimately resulting in a significantly reduced ionic conductivity. Therefore, when y satisfies the above range, excellent ionic conductivity can be achieved.

[0097] In the above formula 2, D represents a halogen element, which may be one or more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0098] More specifically, D may be chlorine (Cl). Among halogen elements, the use of chlorine in particular can have the advantage of stabilizing the structure of the argyrodite-based solid electrolyte and being easier and less expensive to synthesize than other elements.

[0099] Such solid electrolytes may be in the form of particles or powders, and may be crystalline or amorphous.

[0100] In particular, the solid electrolyte may have a peak at 30.2°≦2θ≦30.3° when measuring its X-ray diffraction (XRD) pattern. Having this diffraction peak value has the advantage of preventing deterioration of the ionic conductivity and cell performance of the argyrodite-type solid electrolyte. If the solid electrolyte does not have this diffraction peak value, there may be a problem of deviation from the argyrodite crystalline phase.

[0101] A solid electrolyte according to another embodiment of the present invention may have an ionic conductivity of 3.3 mS / cm to 6 mS / cm at 30° C. More specifically, the solid electrolyte may have an ionic conductivity of 3.5 mS / cm, 4.0 mS / cm, 4.5 mS / cm or more, or 4.6 mS / cm or more, and may have an ionic conductivity of 6 mS / cm or 5 mS / cm or less, at 30° C. When the ionic conductivity satisfies the above range, there is an advantage in that the cell capacity characteristics are improved.

[0102] Another embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, the method comprising: mixing a lithium-containing sulfide, a phosphorus-containing compound, a halogen-containing compound, and a doping source material to form a mixture; and heat-treating the mixture to form a sulfide-based solid electrolyte, wherein the doping source material includes a boron-based compound and a silicon-based compound.

[0103] Hereinafter, each step of a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described in detail.

[0104] First, a lithium-containing sulfide, a phosphorus-containing compound, a chlorine-containing compound, and a doping source material are mixed to form a mixture.

[0105] The lithium-containing sulfide may be, for example, Li2S, Li2S2, or a combination thereof, but is not limited thereto. Specifically, the lithium-containing sulfide may be Li2S.

[0106] The phosphorus-containing compound may be, for example, but not limited to, P2S5, P2O5, or a combination thereof. Specifically, the phosphorus-containing compound may be P2S5.

[0107] The halogen-containing compound may be, for example, but not limited to, LiF, LiCl, LiBr, LiI, or a combination thereof. Specifically, the halogen-containing compound may be LiCl.

[0108] The doping source material includes a boron-based compound and a silicon-based compound.

[0109] In this case, the boron-based compound is not particularly limited as long as it is a compound containing boron, and may be, for example, BCl3 or B2S5.

[0110] In this case, the silicon-based compound is not particularly limited as long as it is a compound containing silicon, and may be, for example, SiCl4 or SiS2.

[0111] Meanwhile, in the step of forming the mixture, the content of the boron-based compound may be 0.014 to 0.05 mol% based on 100 mol% of the total mixture. More specifically, the content of the boron-based compound may be 0.02 to 0.035 mol% or 0.023 to 0.032 mol%. If the content of the boron-based compound added is too low, the amount of boron doping may be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., an increase in ionic conductivity. On the other hand, if the content of the boron-based compound added is too high, the amount of boron doping may be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impede the smooth movement of lithium ions and ultimately result in a significantly reduced ionic conductivity. Therefore, when the content of the boron-based compound to be mixed satisfies the above range, excellent ionic conductivity of the solid electrolyte can be obtained.

[0112] Furthermore, in the step of forming the mixture, the silicon-based compound may be mixed so that its content is 0.04 to 0.4 mol%, based on 100 mol% of the total mixture. More specifically, the silicon-based compound may be mixed so that its content is 0.08 to 0.25 mol% or 0.09 to 0.22 mol%. If the content of the silicon-based compound mixed is too low, the amount of silicon doping may be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., an increase in ionic conductivity. On the other hand, if the content of the silicon-based compound mixed is too high, the amount of silicon doping may be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impede the smooth movement of lithium ions and ultimately result in a significantly reduced ionic conductivity. Therefore, when the content of the silicon-based compound mixed satisfies the above range, excellent ionic conductivity of the solid electrolyte can be obtained.

[0113] The mixing may be carried out by dry mixing or wet mixing.

[0114] Preferably, the mixing may be dry mixing, which has the advantage that a separate solvent is not required as in wet mixing.

[0115] At this time, the dry mixing may be performed by a dry milling method.

[0116] The dry milling may be performed using a ball mill, a vibration mill, a turbo mill, a homogenizer, a hammer mill, a planetary mill, a mechanofusion, a disc mill, a bead mill, or a planetary mill, and more specifically, may be performed using a planetary mill.

[0117] The mixing may be performed for 4 to 12 hours, specifically 6 to 10 hours, and more specifically 7 to 9 hours. If the mixing time is too short, there is a possibility that the mixing may be insufficient. On the other hand, if the mixing time is too long, the mixing may be completed within a certain time, and the mixing state may remain the same even if further mixing is performed, which may cause problems in terms of process efficiency.

[0118] The mixing may be performed at a rotation speed of 100 to 500 rpm, specifically 150 to 450 rpm, and more specifically 200 to 400 rpm. If the rotation speed is too slow, the balls may not penetrate deep into the powder particles, resulting in insufficient mixing of the powder particles and insufficient atomization of the powder particles due to low energy. On the other hand, if the rotation speed is too fast, the powder particles may be concentrated in one area, resulting in insufficient uniform mixing.

[0119] Then, optionally, after the step of forming the mixture, the method can further include a step of compressing the mixture to form pellets.

[0120] The compression may be performed at a pressure of 100 to 500 MPa, specifically 150 to 450 MPa, and more specifically 200 to 400 MPa. If the pressure is too low, the powder particles may not bond well together, resulting in high interfacial resistance. On the other hand, if the pressure is too high, the powder particles may already be bonded together, and applying more pressure will not change the bonded state, which may result in problems in terms of process efficiency. Therefore, forming pellets at an appropriate pressure is preferable from the perspective of productivity.

[0121] The mixture is then heat-treated to form a sulfide-based solid electrolyte. Of course, if a pellet-forming step is further included, the pellet is heat-treated to form the sulfide-based solid electrolyte.

[0122] The heat treatment may be performed at a temperature of 300 to 800° C., specifically 400 to 700° C., and more specifically 500 to 600° C. If the heat treatment temperature is too low, the heat treatment effect may be reduced, whereas if the heat treatment temperature is too high, the elements constituting the solid electrolyte may be vaporized, resulting in loss of the solid electrolyte.

[0123] The heat treatment may be performed in an inert gas atmosphere, more specifically, in an argon (Ar) atmosphere.

[0124] [Third Example] In yet another embodiment, the first doping element may be B and the second doping element may be Sn.

[0125] This will be explained in more detail below.

[0126] Another embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element, and having an argyrodite-based crystal structure, at least a portion of the crystal structure being doped with boron (B) and tin (Sn), and the boron and tin are doped independently of each other.

[0127] In accordance with one embodiment of the present invention, at least a portion of the crystalline structure of a sulfide-based solid electrolyte is doped with boron (B) and tin (Sn). The boron and tin are doped independently of each other. In other words, the doping amounts of boron and tin do not have a fixed correlation and may be adjusted independently and randomly. The sulfide-based solid electrolyte of the present invention has a basic argyrodite crystalline structure, Li6PS5Cl, where boron and tin are independently doped. This allows for the generation of numerous voids due to the deficiency of lithium ions. This results in the formation of diverse lithium ion paths (channels), significantly improving lithium ion conductivity and cell capacity characteristics. The doping amounts of boron and tin can be independently and appropriately adjusted to maximize these effects.

[0128] Such a sulfide-based solid electrolyte according to one embodiment of the present invention may be represented by the following Chemical Formula 3. [Chemical formula 3] Li 6(1-x-y) B x Sn y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the above formula 3, D is F, Cl, Br, I or a combination thereof, 0.013≦x≦0.043, and 0.04≦y≦0.42.

[0129] Specifically, B (boron) and Sn (tin) are doping elements in the above chemical formula 3. In this specification, "doping" can mean not only replacing some elements of a compound with new elements, but also the doped element becoming a component of the crystalline phase of the compound.

[0130] In the formula 3, x represents the doping amount of boron, which is a doping element, in moles, and satisfies 0.013≦x≦0.043.

[0131] More specifically, x may be in the range of 0.02≦x≦0.035 or 0.023≦x≦0.032. An excessively small x may result in an excessively low boron doping amount, while an excessively large x may result in an excessively high boron doping amount. If the boron doping amount is too low, the composition may not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a poor doping effect, i.e., a poor increase in ionic conductivity. On the other hand, if the boron doping amount is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, impairing the smooth movement of lithium ions and ultimately resulting in a significantly reduced ionic conductivity. Therefore, when x satisfies the above range, excellent ionic conductivity can be achieved.

[0132] In addition, in the above Chemical Formula 3, y represents the doping amount of tin as a doping element in moles, and satisfies 0.04≦y≦0.42.

[0133] More specifically, y may be in the range of 0.08≦y≦0.25 or 0.08≦y≦0.17. An excessively small y may result in an excessively low tin doping amount, whereas an excessively large y may result in an excessively high tin doping amount. If the tin doping amount is too low, the composition may not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a poor doping effect, i.e., a poor increase in ionic conductivity. On the other hand, if the tin doping amount is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, impairing the smooth movement of lithium ions and ultimately resulting in a significantly reduced ionic conductivity. Therefore, when y satisfies the above range, excellent ionic conductivity can be achieved.

[0134] In the above formula 3, D represents a halogen element, which may be one or more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0135] More specifically, D may be chlorine (Cl). Among halogen elements, the use of chlorine in particular can have the advantage of stabilizing the structure of the argyrodite-based solid electrolyte and being easier and less expensive to synthesize than other elements.

[0136] Such solid electrolytes may be in the form of particles or powders, and may be crystalline or amorphous.

[0137] In particular, the solid electrolyte may have a peak at 30.2°≦2θ≦30.3° when measuring its X-ray diffraction (XRD) pattern. Having this diffraction peak value has the advantage of preventing deterioration of the ionic conductivity and cell performance of the argyrodite-type solid electrolyte. If the solid electrolyte does not have this diffraction peak value, there may be a problem of deviation from the argyrodite crystalline phase.

[0138] The solid electrolyte according to the present invention may have an ionic conductivity of 3.3 mS / cm to 6 mS / cm at 30° C. More specifically, the solid electrolyte may have an ionic conductivity of 3.3 mS / cm, 4.0 mS / cm, or 4.2 mS / cm or more, and may have an ionic conductivity of 6 mS / cm or 5 mS / cm or less at 30° C. When the ionic conductivity satisfies the above range, there is an advantage in that the cell capacity characteristics are improved.

[0139] Another embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, the method including: mixing a lithium-containing sulfide, a phosphorus-containing compound, a halogen source material, and a doping source material to form a mixture; and heat-treating the mixture to form a sulfide-based solid electrolyte, wherein the doping source material includes a boron-based compound and a tin-based compound.

[0140] Hereinafter, each step of a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described in detail.

[0141] First, a lithium-containing sulfide, a phosphorus-containing compound, a halogen source material, and a doping source material are mixed to form a mixture.

[0142] The lithium-containing sulfide may be, for example, Li2S, Li2S2, or a combination thereof, but is not limited thereto. Specifically, the lithium-containing sulfide may be Li2S.

[0143] The phosphorus-containing compound may be, for example, but not limited to, P2S5, P2O5, or a combination thereof. Specifically, the phosphorus-containing compound may be P2S5.

[0144] The halogen source material may be, for example, but not limited to, LiF, LiCl, LiBr, LiI, or a combination thereof. Specifically, the halogen-containing compound may be LiCl.

[0145] The doping source material includes a boron-based compound and a tin-based compound.

[0146] In this case, the boron-based compound is not particularly limited as long as it is a compound containing boron, and may be, for example, BCl3 or B2S5.

[0147] More specifically, the boron-based compound may be BCl3. Using BCl3 as the boron-based compound has the advantage that it is possible to dope B and design a composition rich in Cl.

[0148] In this case, the tin-based compound is not particularly limited as long as it is a compound containing tin, and may be, for example, SnCl4 or SnS2.

[0149] More specifically, the tin-based compound may be SnCl4. Using SnCl4 as the tin-based compound has the advantage that it is possible to dope Sn and also to design a composition rich in Cl.

[0150] Meanwhile, in the step of forming the mixture, the content of the boron-based compound may be 0.013 to 0.043 mol% based on 100 mol% of the total mixture. More specifically, the content of the boron-based compound may be 0.02 to 0.035 mol% or 0.023 to 0.035 mol%. If the content of the boron-based compound is too low, the amount of boron doping may be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., an increase in ionic conductivity. On the other hand, if the content of the boron-based compound is too high, the amount of boron doping may be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impede the smooth movement of lithium ions and ultimately result in a significantly reduced ionic conductivity. Therefore, when the content of the boron-based compound to be mixed satisfies the above range, excellent ionic conductivity of the solid electrolyte can be obtained.

[0151] Furthermore, in the step of forming the mixture, the tin-based compound may be mixed so that its content is 0.04 to 0.42 mol% based on 100 mol% of the total mixture. More specifically, the tin-based compound may be mixed so that its content is 0.08 to 0.25 mol% or 0.08 to 0.17 mol%. If the content of the tin-based compound mixed is too low, the amount of tin doping may be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., an increase in ionic conductivity. On the other hand, if the content of the tin-based compound mixed is too high, the amount of tin doping may be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impair the smooth movement of lithium ions and ultimately result in a significantly reduced ionic conductivity. Therefore, when the content of the tin-based compound mixed satisfies the above range, excellent ionic conductivity of the solid electrolyte can be obtained.

[0152] The mixing may be carried out by dry mixing or wet mixing.

[0153] Preferably, the mixing may be dry mixing, which has the advantage that a separate solvent is not required as in wet mixing.

[0154] At this time, the dry mixing may be performed by a dry milling method.

[0155] The dry milling may be performed using a ball mill, a vibration mill, a turbo mill, a homogenizer, a hammer mill, a planetary mill, a mechanofusion, a disc mill, a bead mill, or a planetary mill, and more specifically, may be performed using a planetary mill.

[0156] The mixing may be performed for 4 to 12 hours, specifically 6 to 10 hours, and more specifically 7 to 9 hours. If the mixing time is too short, there is a possibility that the mixing may be insufficient. On the other hand, if the mixing time is too long, the mixing may be completed within a certain time, and the mixing state may remain the same even if further mixing is performed, which may cause problems in terms of process efficiency.

[0157] The mixing may be performed at a rotation speed of 100 to 500 rpm, specifically 150 to 450 rpm, and more specifically 200 to 400 rpm. If the rotation speed is too slow, the balls may not penetrate deep into the powder particles, resulting in insufficient mixing of the powder particles and insufficient atomization of the powder particles due to low energy. On the other hand, if the rotation speed is too fast, the powder particles may be concentrated in one area, resulting in insufficient uniform mixing.

[0158] Then, optionally, after the step of forming the mixture, the method can further include a step of compressing the mixture to form pellets.

[0159] The compression may be performed at a pressure of 100 to 500 MPa, specifically 150 to 450 MPa, and more specifically 200 to 400 MPa. If the pressure is too low, the powder particles may not bond well together, resulting in high interfacial resistance. On the other hand, if the pressure is too high, the powder particles may already be bonded together, and applying more pressure will not change the bonded state, which may result in problems in terms of process efficiency. Therefore, forming pellets at an appropriate pressure is preferable from the perspective of productivity.

[0160] The mixture is then heat-treated to form a sulfide-based solid electrolyte. Of course, if a pellet-forming step is further included, the pellet is heat-treated to form the sulfide-based solid electrolyte.

[0161] The heat treatment may be performed at a temperature of 300 to 800° C., specifically 400 to 700° C., and more specifically 500 to 600° C. If the heat treatment temperature is too low, the heat treatment effect may be reduced, whereas if the heat treatment temperature is too high, the elements constituting the solid electrolyte may be vaporized, resulting in loss of the solid electrolyte.

[0162] The heat treatment may be performed in an inert gas atmosphere, more specifically, in an argon (Ar) atmosphere.

[0163] [Fourth Example] In yet another embodiment, the first doping element may be Al and the second doping element may be Si.

[0164] This will be explained in more detail below.

[0165] Another embodiment of the present invention provides a sulfide-based solid electrolyte comprising lithium (Li), phosphorus (P), sulfur (S), and a halogen element, and having an argyrodite-based crystal structure, at least a portion of which is doped with aluminum (Al) and silicon (Si), and the aluminum and silicon are doped independently of each other.

[0166] In another embodiment of the present invention, a sulfide-based solid electrolyte has at least a portion of its crystal structure doped with aluminum (Al) and silicon (Si). The aluminum and silicon are doped independently. In other words, the doping amounts of aluminum and silicon do not have a fixed correlation but may be controlled independently and randomly. The sulfide-based solid electrolyte of the present invention has a basic argyrodite crystal structure, Li6PS5Cl, where aluminum and silicon are doped independently, thereby generating numerous voids due to a deficiency of lithium ions. This results in the formation of various lithium ion paths (channels), significantly improving the lithium ion conductivity of the electrolyte and improving electrochemical properties such as the battery capacity, initial efficiency, and lifespan characteristics. The doping amounts of aluminum and silicon can be controlled independently and appropriately to maximize these effects.

[0167] The sulfide-based solid electrolyte according to another embodiment of the present invention may be represented by the following Chemical Formula 4. [Chemical formula 4] Li 6(1-x-y) Al x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the above formula 4, D is F, Cl, Br, I or a combination thereof, 0.01≦x≦0.05, and 0.1≦y≦0.4.

[0168] Specifically, Al (aluminum) and Si (silicon) are doping elements in the above chemical formula 4. In this specification, "doping" can mean not only replacing some elements of a compound with new elements, but also the doped element becoming a component of the crystalline phase of the compound.

[0169] In the formula 4, x represents the doping amount of aluminum as a doping element in moles, and satisfies 0.01≦x≦0.05.

[0170] More specifically, x may be in the range of 0.02≦x≦0.045. An excessively small x may result in an excessively low aluminum doping level, whereas an excessively large x may result in an excessively high aluminum doping level. If the aluminum doping level is too low, the composition may not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a reduced doping effect, i.e., a reduced increase in electrolyte ionic conductivity and improved battery electrochemical performance. On the other hand, if the aluminum doping level is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, impairing lithium ion mobility and ultimately resulting in a significantly reduced ionic conductivity. Therefore, when x satisfies the above range, the ionic conductivity of the electrolyte and the electrochemical performance of the battery may be maximized.

[0171] In addition, in the above Chemical Formula 4, y represents the doping amount of silicon as a doping element in moles, and 0.1≦y≦0.4 can be satisfied.

[0172] More specifically, y may be in the range of 0.15≦y≦0.35. An excessively small y may result in an excessively low silicon doping amount, whereas an excessively large y may result in an excessively high silicon doping amount. If the silicon doping amount is too low, the composition will not differ significantly from that of the basic Li6PS5Cl argyrodite, potentially resulting in a reduced doping effect, i.e., a reduced increase in electrolyte ionic conductivity and improved battery electrochemical performance. On the other hand, if the silicon doping amount is too high, the crystalline structure of the argyrodite in the sulfide-based solid electrolyte may be significantly distorted, resulting in less smooth lithium ion migration and ultimately in significantly reduced ionic conductivity. Therefore, when y satisfies the above range, the ionic conductivity of the electrolyte and the electrochemical performance of the battery can be maximized.

[0173] In the above formula 4, D represents a halogen element, which may be one or more of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0174] More specifically, D may be chlorine (Cl). Among halogen elements, the use of chlorine in particular can have the advantage of stabilizing the structure of the argyrodite-based solid electrolyte and being easier and less expensive to synthesize than other elements.

[0175] Such solid electrolytes may be in the form of particles or powders, and may be crystalline or amorphous.

[0176] The solid electrolyte according to the present invention may have an ionic conductivity of 3.5 mS / cm to 6 mS / cm at 30° C. More specifically, the solid electrolyte may have an ionic conductivity of 3.5 mS / cm, 3.6 mS / cm, or 4.0 mS / cm or more, and may have an ionic conductivity of 6 mS / cm or 5 mS / cm or less at 30° C. When the ionic conductivity satisfies the above range, there is an advantage in that the cell capacity characteristics are improved.

[0177] Another embodiment of the present invention provides a method for producing a sulfide-based solid electrolyte, the method including: mixing a lithium-containing sulfide, a phosphorus-containing compound, a halogen source material, and a doping source material to form a mixture; and heat-treating the mixture to form a sulfide-based solid electrolyte, wherein the doping source material includes an aluminum-based compound and a silicon-based compound.

[0178] Hereinafter, each step of a method for manufacturing a sulfide-based solid electrolyte according to another embodiment of the present invention will be described in detail.

[0179] First, a lithium-containing sulfide, a phosphorus-containing compound, a halogen source material, and a doping source material are mixed to form a mixture.

[0180] The lithium-containing sulfide may be, for example, Li2S, Li2S2, or a combination thereof, but is not limited thereto. Specifically, the lithium-containing sulfide may be Li2S.

[0181] The phosphorus-containing compound may be, for example, but not limited to, P2S5, P2O5, or a combination thereof. Specifically, the phosphorus-containing compound may be P2S5.

[0182] The halogen source material may be, for example, but not limited to, LiF, LiCl, LiBr, LiI, or a combination thereof. Specifically, the halogen-containing compound may be LiCl.

[0183] The doping source material includes an aluminum-based compound and a silicon-based compound.

[0184] In this case, the aluminum-based compound is not particularly limited as long as it is a compound containing aluminum, and may be, for example, AlCl3 or Al2O3.

[0185] More specifically, the aluminum-based compound may be AlCl3. Using AlCl3 as the aluminum-based compound has the advantage that Al can be doped and a composition rich in Cl can be designed.

[0186] In this case, the silicon-based compound is not particularly limited as long as it is a compound containing silicon, and may be, for example, SiCl4 or SiS2.

[0187] More specifically, the silicon-based compound may be SiCl4. Using SiCl4 as the silicon-based compound has the advantage that Si can be doped and a composition rich in Cl can be designed.

[0188] Meanwhile, in the step of forming the mixture, the aluminum-based compound may be mixed so that its content is 0.01 to 0.05 mol % based on 100 mol % of the total mixture. More specifically, the aluminum-based compound may be mixed so that its content is 0.02 to 0.045 mol %. If the content of the aluminum-based compound mixed is too low, the aluminum doping amount may be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., an increase in electrolyte ionic conductivity and an improvement in the electrochemical characteristics of the battery. On the other hand, if the content of the aluminum-based compound mixed is too high, the aluminum doping amount may be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impair the smooth movement of lithium ions and ultimately result in a significant decrease in ionic conductivity. Therefore, when the content of the aluminum-based compound mixed satisfies the above range, the ionic conductivity of the electrolyte and the electrochemical characteristics of the battery may be maximized.

[0189] Furthermore, in the step of forming the mixture, the silicon-based compound may be mixed so that its content is 0.1 to 0.4 mol % based on 100 mol % of the total mixture. More specifically, the silicon-based compound may be mixed so that its content is 0.15 to 0.35 mol %. If the content of the silicon-based compound mixed is too low, the silicon doping amount will be too low, resulting in a composition that is not significantly different from the basic Li6PS5Cl argyrodite composition, which may result in a reduced doping effect, i.e., a reduced increase in electrolyte ionic conductivity and improved electrochemical properties of the battery. On the other hand, if the content of the silicon-based compound mixed is too high, the silicon doping amount will be too high, resulting in a significant deformation of the crystalline structure of the argyrodite in the sulfide-based solid electrolyte, which may impair the smooth movement of lithium ions and ultimately result in a significant decrease in ionic conductivity. Therefore, when the content of the silicon-based compound mixed satisfies the above range, the ionic conductivity of the electrolyte and the electrochemical properties of the battery can be maximized.

[0190] The mixing may be carried out by dry mixing or wet mixing.

[0191] Preferably, the mixing may be dry mixing, which has the advantage that a separate solvent is not required as in wet mixing.

[0192] At this time, the dry mixing may be performed by a dry milling method.

[0193] The dry milling may be performed using a ball mill, a vibration mill, a turbo mill, a homogenizer, a hammer mill, a planetary mill, a mechanofusion mill, a disc mill, a bead mill, or a planetary mill, and more specifically, may be performed using a planetary mill.

[0194] The mixing may be performed for 4 to 12 hours, specifically 6 to 10 hours, and more specifically 7 to 9 hours. If the mixing time is too short, there is a possibility that the mixing may be insufficient. On the other hand, if the mixing time is too long, the mixing may be completed within a certain time, and the mixing state may remain the same even if further mixing is performed, which may cause problems in terms of process efficiency.

[0195] The mixing may be performed at a rotation speed of 100 to 500 rpm, specifically 150 to 450 rpm, and more specifically 200 to 400 rpm. If the rotation speed is too slow, the balls may not penetrate deep into the powder particles, resulting in insufficient mixing of the powder particles and insufficient atomization of the powder particles due to low energy. On the other hand, if the rotation speed is too fast, the powder particles may be concentrated in one area, resulting in insufficient uniform mixing.

[0196] Then, optionally, after the step of forming the mixture, the method can further include a step of compressing the mixture to form pellets.

[0197] The compression may be performed at a pressure of 100 to 500 MPa, specifically 150 to 450 MPa, and more specifically 200 to 400 MPa. If the pressure is too low, the powder particles may not bond well together, resulting in high interfacial resistance. On the other hand, if the pressure is too high, the powder particles may already be bonded together, and applying more pressure will not change the bonded state, which may result in problems in terms of process efficiency. Therefore, forming pellets at an appropriate pressure is preferable from the perspective of productivity.

[0198] The mixture is then heat-treated to form a sulfide-based solid electrolyte. Of course, if a pellet-forming step is further included, the pellet is heat-treated to form the sulfide-based solid electrolyte.

[0199] The heat treatment may be performed at a temperature of 300 to 800° C., specifically 400 to 700° C., and more specifically 500 to 600° C. If the heat treatment temperature is too low, the heat treatment effect may be reduced, whereas if the heat treatment temperature is too high, the elements constituting the solid electrolyte may be vaporized, resulting in loss of the solid electrolyte.

[0200] The heat treatment may be performed in an inert gas atmosphere, more specifically, in an argon (Ar) atmosphere.

[0201] Fifth Example In yet another embodiment, the first doping element may be B and the second doping element may be Ge.

[0202] This will be explained in more detail below.

[0203] The solid electrolyte according to an embodiment of the present invention may be an argyrodite-type solid electrolyte containing a sulfate-based compound. The solid electrolyte is not a solid electrolyte interphase (SEI), which is a film formed at the interface of electrode materials during the initial charge-discharge reaction after battery fabrication, but rather a solid material having lithium (Li) ion conductivity that can be used as a substitute for an electrolyte solution and a separator when designing a battery.

[0204] The solid electrolyte of the present invention having the above composition may be a sulfur-containing compound, i.e., a sulfide-based solid electrolyte. Specifically, the argyrodite-type may have an argyrodite-type structure containing lithium (Li), phosphorus (P), sulfur (S), and a halogen element such as chlorine (Cl). The solid electrolyte may be in the form of particles or powder, and may be crystalline or amorphous.

[0205] In one embodiment, the argyrodite-type solid electrolyte may be simultaneously doped with a first doping element, boron (B), and a second doping element, germanium (Ge). In one embodiment, the first doping element may be a compound containing a trivalent element, and the second doping element may be a compound containing a tetravalent element. The trivalent element may be a Group 13 element on the periodic table, and the tetravalent element may be a Group 14 element on the periodic table.

[0206] In one embodiment, the first doping element may be boron derived from a boron-based compound. The boron-based compound may be at least one of borate, borole, and borane. Specifically, the boron-based compound may be, for example, boron trichloride (BCl3).

[0207] In one embodiment, the first doping element may be included in an amount of 0.02 to 0.04 mol% based on the total number of moles of the solid electrolyte. That is, the solid electrolyte may include the first doping element in an amount of 0.02 to 0.04 mol% based on the total number of moles of the solid electrolyte. By including the first doping element in the above range, there is an advantage in that ionic conductivity is increased.

[0208] If the first doping element is out of the upper limit of the range, the first doping element may act as an impurity, resulting in a decrease in ionic conductivity. If the first doping element is out of the lower limit of the range, the effect of adding the first doping element may not be achieved because the composition does not deviate significantly from the existing composition.

[0209] In one embodiment, the second doping element may be germanium resulting from a germanium (Ge)-based compound, for example, germanium tetrachloride (GeCl4).

[0210] In one embodiment, the second doping element may be included in an amount of 0.1 to 0.3 mol% based on the total number of moles of the solid electrolyte. That is, the solid electrolyte may include the second doping element in an amount of 0.1 to 0.3 mol% based on the total number of moles of the solid electrolyte. More specifically, the second doping element may be included in an amount of 0.2 to 0.3 mol% based on the total number of moles of the solid electrolyte. The inclusion of the second doping element has the advantage of improving ionic conductivity.

[0211] If the second doping element is out of the upper limit of the range, the second doping element acts as an impurity, resulting in a decrease in ionic conductivity. If the second doping element is out of the lower limit of the range, the effect of adding the second doping element is not achieved because the composition does not deviate significantly from the existing composition.

[0212] The argyrodite-type solid electrolyte has an advantage that the first element and the second element correspond to doping raw materials, and the ionic conductivity is significantly improved by simultaneously doping the first element and the second element, thereby improving cell capacity characteristics.

[0213] In one embodiment, the argyrodite-type solid electrolyte may satisfy the following chemical formula: <chemical formula> Li 6(1-x-y) A x B y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y (In the above chemical formula, A is B (Boron), B is Ge (Germanium), C may be at least one of Cl, Br, and I, and x is 0.02 <x<0.04であり、yは、0.1<y<0.3である。)

[0214] The argyrodite-type solid electrolyte has an advantage that it has superior ionic conductivity compared to a case where a single element is included, since it contains a different element as a doping source material.

[0215] That is, the solid electrolyte may be represented by the following chemical formula 5: [Chemical formula 5] Li 6(1-x-y) B x Ge y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y In the above formula 5, C is at least one of F, Cl, Br and I, and <x<0.04であり、0.1<y<0.3である。

[0216] In one embodiment, the argyrodite-type solid electrolyte may satisfy the following formula 1: <Expression 1> 0.37≦[Second element]×ionic conductivity[mS / cm]≦1.30 (In the above formula 1, [second element] means mol% of the second element, and the ionic conductivity means the impedance value when 10 mV is applied at 30°C.)

[0217] The above formula 1 shows the relationship between the number of moles (mol%) of the second element, for example, a germanium compound, and ionic conductivity. The formula 1 may have a value of 0.37 to 1.30. Specifically, the value of the formula 1 may have a value of 0.37 to 1.14. By satisfying the formula 1, it is possible to manufacture a solid electrolyte with high ionic conductivity. If the value of the formula 1 is outside the upper limit, there is a problem that an impurity phase is generated, resulting in a decrease in ionic conductivity. If the value of the formula 1 is outside the lower limit, there is a problem that the doping effect is small and the improvement in the ionic conductivity of the solid electrolyte is not achieved.

[0218] In one embodiment, the argyrodite-type solid electrolyte may have an ionic conductivity of 3.3 to 8.0 mS / cm or more. Specifically, the ionic conductivity may be 3.3 to 4.4 mS / cm or more. When the ionic conductivity satisfies this range, there is an advantage in that the cell capacity characteristics are improved.

[0219] A method for manufacturing an argyrodite-type solid electrolyte according to another embodiment of the present invention may include the steps of preparing a lithium source material, a sulfur source material, and a halogen source material; adding a first doping material and a second doping material to the prepared materials at 0.02 to 0.04 mol% and 0.1 to 0.3 mol%, respectively; mixing the resulting material with the doping materials added; and heat-treating the resulting mixture.

[0220] In the step of preparing a lithium source material, a sulfur source material, a halogen source material, and a doping source material, the lithium source material and the sulfur source material may be selected from known materials such as, but not limited to, LiS and LiS. More specifically, the lithium source material may be LiS.

[0221] The halogen source material may be a source material containing various halogen elements such as, but not limited to, F, Cl, and Br. Specifically, the halogen source material may be LiCl.

[0222] In the step of adding 0.02 to 0.04 mol% of a first doping material and 0.1 to 0.3 mol% of a second doping material to the prepared material, the first doping material and the second doping material may be added at 0.02 to 0.04 mol% and 0.2 to 0.3 mol%. When the contents of the first doping material and the second doping material satisfy the above ranges, a large number of voids due to a deficiency of lithium ions are generated, thereby increasing ionic conductivity.

[0223] If the contents of the first doping material and the second doping material are outside the upper limit of the range, the argyrodite phase may not be maintained and an impurity phase may be generated.If the contents of the first doping material and the second doping material are outside the lower limit of the range, the argyrodite phase may not be significantly different from the existing argyrodite phase, making it difficult to achieve the above-mentioned advantages.

[0224] The step of mixing the resultant material after adding the doping material may be performed by mechanical mixing or chemical mixing. For example, the mechanical mixing may be performed using a paint shaker, ball mill, bead mill, homogenizer, hammer mill, or planetary mill, while the chemical mixing may be performed using a melt quenching method. Specifically, the step of mixing the raw materials may be performed using a planetary mill.

[0225] In one embodiment, the step of mixing the source materials may be performed at a speed of 200 to 400 rpm. By mixing the source materials at this speed range, it is possible to easily fuse the doping material.

[0226] If the speed is outside the upper limit of the above range, the raw materials may not be mixed uniformly, and if the speed is outside the lower limit of the above range, the raw materials may not be milled and mixed sufficiently.

[0227] The step of heat-treating the mixed resultant is a step of synthesizing the mixed resultant. In one embodiment, the step of heat-treating the mixed resultant may be performed at a temperature range of 400 to 700°C. Specifically, the temperature range may be 500 to 600°C.

[0228] If the temperature is outside the upper limit of the range, the argyrodite phase may not be formed and an impurity phase may be generated, whereas if the temperature is outside the lower limit of the range, the argyrodite phase may not be formed or may exist as an amorphous crystalline structure.

[0229] In one embodiment, the step of heat-treating the mixed resultant may be performed in an inert atmosphere, which may be a stable atmosphere such as Ar, N2, H2, or He. Specifically, the inert atmosphere of the present invention may be an Ar atmosphere.

[0230] Through the above steps, the argyrodite-type solid electrolyte can satisfy the following chemical formula: <chemical formula> Li 6(1-x-y) A x B y P (1-x-y) S 5(1-x-y) C 1(1-x-y)+3x+4y (In the above chemical formula, A is B (Boron), B is Ge (Germanium), C may be at least one of Cl, Br, and I, and x is 0.02 <x<0.04であり、yは、0.1<y<0.3である。)

[0231] For example, when the first doping material of the present invention is the boron-based compound BCl3 and the second doping material is the germanium-based compound GeCl4, an all-solid-state electrolyte having the following chemical formula can be obtained. <chemical formula> (1-xy)Li6PS5Cl+xBCl3+yGeCl4→Li 6(1-x-y) B x GeP (1-x-y) S 5(1-x-y) Cl 1+2x+3y

[0232] For a detailed description of the solid electrolyte of the present invention manufactured by the method for manufacturing a solid electrolyte according to an embodiment of the present invention, please refer to the above description.

[0233] A lithium secondary battery according to another embodiment of the present invention may include a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator separating the positive electrode and the negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode. The solid electrolyte may refer to the argyrodite-type solid electrolyte described above, and may be the same as the solid electrolyte described above to the extent not inconsistent.

[0234] In one embodiment, the lithium secondary battery may satisfy the following formula 2: <Expression 2> 0.24≦([first element]+[second element]) / (ionic conductivity [mS / cm] / charge capacity [mAh / g]×100)≦0.65 (In the above formula 2, [first element] and [second element] mean the mol% of the first element and the second element, the ionic conductivity means the impedance value when 10 mV is applied at 30°C, and the charge capacity means the capacity evaluation value at a reference capacity of 180 mAh / g after forming a positive electrode on the solid electrolyte.)

[0235] The above formula 2 shows the relationship between the first and second elements and the ionic conductivity of the argyrodite-type solid electrolyte and the charge capacity of an electrode manufactured using the same. The value of formula 2 may be 0.24 to 0.65. Specifically, the value of formula 2 may be 0.25 to 0.56. Satisfying the value of formula 2 has the advantage of improving ionic conductivity.

[0236] If the value of the formula 2 is outside the upper limit, an impurity phase is generated, which reduces ionic conductivity. If the value of the formula 2 is outside the lower limit, the doping effect is small, which results in little improvement in ionic conductivity compared to existing solid electrolytes.

[0237] [2. Lithium secondary battery] Another embodiment of the present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte layer comprises the above-described solid electrolyte.

[0238] The solid electrolyte is the same as that described above, so the remaining components will be described in detail below.

[0239] The positive electrode may include a current collector and a positive electrode active material layer disposed on the current collector, and the positive electrode active material layer may include a positive electrode active material.

[0240] The positive electrode active material may be a compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound). Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used. Specific examples thereof include compounds represented by any one of the following chemical formulas:

[0241] Li a A 1-b B b D2 (wherein, in the above formula, 0.90≦a≦1.8, and 0≦b≦0.5); Li a E 1-b B b O 2-c D c (wherein 0.90≦a≦1.8, 0≦b≦0.5, and 0≦c≦0.05); LiE 2-b B b O 4-c D c (wherein 0≦b≦0.5 and 0≦c≦0.05); Li a Ni 1-b-c Co b B c D α (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α≦2); Li a Ni 1-b-c Cob B c O 2-α T α (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Co b B c O 2-α T2 (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Mn b B c D α (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α≦2); Li a Ni 1-b-c Mn b B c O 2-α T α (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Mn b B c O 2-α T2 (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni b E c G d O2 (wherein 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and 0.001≦d≦0.1 in the above formula); Li a Ni b Co c Mn d GeO2 (wherein the formula is 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, and 0.001≦e≦0.1); Li a NiG b O2 (wherein 0.90≦a≦1.8 and 0.001≦b≦0.1 in the above formula); Li a CoG b O2 (wherein 0.90≦a≦1.8 and 0.001≦b≦0.1 in the above formula); Li a MnG bO2 (wherein 0.90≦a≦1.8 and 0.001≦b≦0.1 in the above formula); Li a Mn2G b O4 (where 0.90≦a≦1.8, 0.001≦b≦0.1 in the above formula); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3(0≦f≦2); and LiFePO4.

[0242] In the above chemical formula, A can be Ni, Co, Mn, or a combination thereof; B can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D can be O, F, S, P, or a combination thereof; E can be Co, Mn, or a combination thereof; T can be F, S, P, or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q can be Ti, Mo, Mn, or a combination thereof; I can be Cr, V, Fe, Sc, Y, or a combination thereof; and J can be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0243] Of course, the compound may have a coating layer on its surface, or the compound may be mixed with a compound having a coating layer.

[0244] The coating layer may include at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. These coating layer compounds may be amorphous or crystalline. Examples of coating elements included in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, and mixtures thereof. The coating layer formation process may use any coating method (e.g., spray coating, dipping, etc.) that does not adversely affect the physical properties of the positive electrode active material and is easily understood by those skilled in the art, so a detailed description will be omitted.

[0245] The positive electrode active material layer may further include a conductive material and / or a binder in addition to the positive electrode active material.

[0246] The binder serves to facilitate adhesion of positive electrode active material particles to each other and to facilitate adhesion of the positive electrode active material to a current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0247] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive without causing a chemical change in the constructed battery can be used. Examples of such a conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, silver, and the like; conductive polymer materials such as polyphenylene derivatives; and conductive materials containing mixtures of these.

[0248] The current collector may be made of aluminum, but is not limited thereto.

[0249] The negative electrode includes a current collector and a negative electrode active material layer disposed on the current collector, the negative electrode active material layer including a negative electrode active material.

[0250] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0251] The material capable of reversibly intercalating / deintercalating lithium ions may be any carbonaceous negative electrode active material commonly used in lithium ion secondary batteries, representative examples of which include crystalline carbon, amorphous carbon, or a combination of these. Examples of crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous graphite, such as natural graphite or artificial graphite. Examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0252] For the alloy of the lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0253] Examples of the substance capable of doping and undoping lithium include Si, SiOx (0 < x < 2), Si - Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), Sn, SnO2, Sn - Y (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Sn), etc. Also, at least one of these can be mixed with SiO2 and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0254] Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, etc.

[0255] The negative electrode active material layer further includes a binder and may selectively further include a conductive material.

[0256] The binder serves to facilitate adhesion of negative electrode active material particles to each other and to facilitate adhesion of the negative electrode active material to a current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0257] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive without causing a chemical change in the constructed battery can be used. Examples of such a conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber of copper, nickel, aluminum, silver, and the like; conductive polymer materials such as polyphenylene derivatives; and conductive materials containing mixtures of these.

[0258] The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0259] The negative and positive electrodes are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the composition on a current collector. Since this electrode preparation method is widely known in the art, a detailed description thereof will be omitted here. Examples of the solvent include, but are not limited to, N-methylpyrrolidone.

[0260] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these materials, including mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator.

[0261] Another embodiment of the present invention provides an electric vehicle including the lithium secondary battery. [Example]

[0262] Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are merely preferred examples of the present invention and are not intended to limit the scope of the present invention.

[0263] [Experimental Group I. First Example (In and Si doping)] <Comparative example 1-1-Li6PS5Cl solid electrolyte> Li6PS5Cl is synthesized by dry milling. Specifically, Li2S, P2S5, and LiCl are mixed in a planetary mill at 300 rpm for 8 hours, then pelletized at 300 MPa and heat-treated at 550°C in an argon (Ar) atmosphere.

[0264] Comparative Example 1-2 - Li6PS5Cl solid electrolyte containing 0.02 mol% In The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl 3 was added as a doping material.

[0265] <Comparative Example 1-3 - Li6PS5Cl solid electrolyte containing 0.1 mol% Si> The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.1 mol % of SiCl3 was added as a doping material.

[0266] Example 1-1 - Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.02 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.02 mol % of SiCl4 were added.

[0267] Example 1-2: Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.05 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.05 mol % of SiCl4 were added.

[0268] Example 1-3 - Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.1 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0269] Example 1-4 - Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.15 mol% Si The solid electrolyte was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.15 mol % of SiCl4 were added to the solid electrolyte prepared in Comparative Example 1-1.

[0270] Example 1-5 - Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.2 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.2 mol % of SiCl4 were added.

[0271] <Example 1-6—Li6PS5Cl solid electrolyte containing 0.02 mol% In and 0.3 mol% Si> The solid electrolyte was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.3 mol % of SiCl4 were added to the solid electrolyte prepared in Comparative Example 1-1.

[0272] Comparative Example 1-4—Li6PS5Cl Solid Electrolyte Containing 0.02 mol% In and 0.4 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.02 mol % of InCl3 and 0.4 mol % of SiCl4 were added.

[0273] Example 1-7 - Li6PS5Cl solid electrolyte containing 0.005 mol% In and 0.1 mol% Si The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.005 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0274] <Example 1-8 - Li6PS5Cl solid electrolyte containing 0.01 mol% In and 0.1 mol% Si> The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.01 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0275] <Example 1-9 - Li6PS5Cl solid electrolyte containing 0.015 mol% In and 0.1 mol% Si> The solid electrolyte was synthesized under the same conditions as in Comparative Example 1-1, except that 0.015 mol % of InCl3 and 0.1 mol % of SiCl4 were added to the solid electrolyte prepared in Comparative Example 1-1.

[0276] <Example 1-10—Li6PS5Cl solid electrolyte containing 0.025 mol% In and 0.1 mol% Si> The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.025 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0277] <Example 1-11—Li6PS5Cl solid electrolyte containing 0.03 mol% In and 0.1 mol% Si> The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.03 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0278] <Example 1-12—Li6PS5Cl solid electrolyte containing 0.04 mol% In and 0.1 mol% Si> The solid electrolyte was synthesized under the same conditions as in Comparative Example 1-1, except that 0.04 mol % of InCl3 and 0.1 mol % of SiCl4 were added to the solid electrolyte prepared in Comparative Example 1-1.

[0279] <Comparative Example 1-5—Li6PS5Cl Solid Electrolyte Containing 0.05 mol% In and 0.1 mol% Si> The solid electrolyte prepared in Comparative Example 1-1 was synthesized under the same conditions as in Comparative Example 1-1, except that 0.05 mol % of InCl3 and 0.1 mol % of SiCl4 were added.

[0280] [Experimental Example 1: Composition Analysis] The composition analysis of the examples and comparative examples was carried out by chemical analysis to confirm the actual composition of the synthesized samples. The composition of the solid electrolyte was measured using an ICP (Inductively Coupled Plasma Emission Spectrometry) device. Specifically, the samples prepared in the examples and comparative examples were dissolved in HNO3 solvent, then diluted with DI water, and the element content was measured using the ICP device.

[0281] [Experimental Example 2: Evaluation of ionic conductivity at 30°C and 0.1C] The solid electrolytes of the examples and comparative examples were electrochemically evaluated using a pressure powder cell. The synthesized solid electrolyte was crushed and formed into a 300 MPa pellet. The cell was then clamped under a pressure of 70 MPa using Sodium hydroxide as the working electrode, and the ionic conductivity was measured by impedance. Impedance was measured by applying 10 mV at 30°C.

[0282] [Table 1]

[0283] From Table 1, it can be seen that the ionic conductivities of Comparative Examples 1-1 to 1-3, which correspond to the cases where no InCl3 or SiCl4 was added or where InCl3 and SiCl4 were not added simultaneously, were lower than those of the Examples of the present invention. Furthermore, when the SiCl4 content was 0.4 mol% or more, as in Comparative Example 1-4, or when the InCl3 content was 0.05 mol% or more, as in Comparative Example 1-5, excessive impurities were formed, resulting in low ionic conductivity. From Table 1, it can be seen that the material properties of the argyrodite-type solid electrolyte of the present invention can be confirmed. Specifically, it can be seen that the simultaneous mixing of InCl3 and SiCl4 resulted in superior ionic conductivity compared to the case where InCl3 or SiCl4 was mixed alone. In the case of InCl3, it can be seen that the ionic conductivity was superior when the InCl3 content was 0.005 to 0.04 mol%, specifically 0.01 to 0.03 mol%, and more specifically 0.02 to 0.03 mol%. In addition, in the case of SiCl4, it can be confirmed that excellent ionic conductivity is achieved when the content is 0.02 to 0.3 mol%, specifically 0.1 to 0.2 mol%, and more specifically 0.1 to 0.15 mol%.

[0284] [Experimental Group II. Second Example (B and Si doping)] Example 2-1: Li 5.76 B 0.02 Si 0.02 P 0.96S 4.8 Cl 1.1 Solid Electrolyte Manufacturing The final product is Li 6(1-x-y) B x Si y P (1-x-y) S 5(1-x-y) Cl 1(1-x-y)+3x+4y The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified in a solid electrolyte so that x = 0.02 and y = 0.02, and BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and the mixture was mixed at 300 rpm for approximately 8 hours using a planetary mill to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550°C in an argon (Ar) atmosphere to form Li 5.76 B 0.02 Si 0.02 P 0.96 S 4.8 Cl 1.1 A solid electrolyte was prepared.

[0285] Example 2-2: Li 5.58 B 0.02 Si 0.05 P 0.93 S 4.65 Cl 1.19 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.05, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.05 mol% based on 100 mol% of the total reactants. 5.58 B 0.02 Si 0.05 P 0.93 S 4.65 Cl 1.19 A solid electrolyte was prepared.

[0286] Example 2-3: Li5.28 B 0.02 Si 0.1 P 0.88 S 4.4 Cl 1.34 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.28 B 0.02 Si 0.1 P 0.88 S 4.4 Cl 1.34 A solid electrolyte was prepared.

[0287] Example 2-4: Li 4.98 B 0.02 Si 0.15 P 0.83 S 4.15 Cl 1.49 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.15, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.15 mol% based on 100 mol% of the total reactants. 4.98 B 0.02 Si 0.15 P 0.83 S 4.15 Cl 1.49 A solid electrolyte was prepared.

[0288] Example 2-5: Li 4.68 B 0.02 Si 0.2 P 0.78 S 3.9 Cl 1.64 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.2, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.2 mol% based on 100 mol% of the total reactants. 4.68 B 0.02 Si 0.2 P 0.78 S 3.9 Cl 1.64 A solid electrolyte was prepared.

[0289] Example 2-6: Li 4.08 B 0.02 Si 0.3 P 0.68 S 3.4 Cl 1.94 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.3, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.3 mol% based on 100 mol% of the total reactants. 4.08 B 0.02 Si 0.3 P 0.68 S 3.4 Cl 1.94 A solid electrolyte was prepared.

[0290] Example 2-7: Li 3.48 B 0.02 Si 0.4 P 0.58 S 2.9 Cl 2.24 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.4, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.4 mol% based on 100 mol% of the total reactants. 3.48B 0.02 Si 0.4 P 0.58 S 2.9 Cl 2.24 A solid electrolyte was prepared.

[0291] Example 2-8: Li 5.37 B 0.005 Si 0.1 P 0.895 S 4.475 Cl 1.31 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.005 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.005 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.37 B 0.005 Si 0.1 P 0.895 S 4.475 Cl 1.31 A solid electrolyte was prepared.

[0292] Example 2-9: Li 5.34 B 0.01 Si 0.1 P 0.89 S 4.45 Cl 1.32 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.01 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.01 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.34 B 0.01 Si 0.1 P 0.89 S 4.45 Cl 1.32 A solid electrolyte was prepared.

[0293] Example 2-10: Li 5.31 B 0.015 Si0.1 P 0.885 S 4.425 Cl 1.33 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.015 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.015 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.31 B 0.015 Si 0.1 P 0.885 S 4.425 Cl 1.33 A solid electrolyte was prepared.

[0294] Example 2-11: Li 5.25 B 0.025 Si 0.1 P 0.875 S 4.375 Cl 1.35 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.025 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.025 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.25 B 0.025 Si 0.1 P 0.875 S 4.375 Cl 1.35 A solid electrolyte was prepared.

[0295] Example 2-12: Li 5.22 B 0.03 Si 0.1 P 0.87 S 4.35 Cl 1.36 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.03 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.03 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.22 B 0.03 Si 0.1 P 0.87 S 4.35 Cl 1.36 A solid electrolyte was prepared.

[0296] Example 2-13: Li 5.16 B 0.04 Si 0.1 P 0.86 S 4.3 Cl 1.38 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.04 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.04 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.16 B 0.04 Si 0.1 P 0.86 S 4.3 Cl 1.38 A solid electrolyte was prepared.

[0297] Example 2-14: Li 5.1 B 0.05 Si 0.1 P 0.85 S 4.25 Cl 1.4 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SiCl4 were quantified so that x = 0.05 and y = 0.1, and the same procedure as in Example 2-1 was carried out except that BCl3 was adjusted to 0.05 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants.5.1 B 0.05 Si 0.1 P 0.85 S 4.25 Cl 1.4 A solid electrolyte was prepared.

[0298] <Comparative Example 2-1: Production of Li6PS5Cl solid electrolyte> The reactants Li2S, P2S5 and LiCl were mixed in a planetary mill at 300 rpm for approximately 8 hours to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550° C. in an argon (Ar) atmosphere to prepare a Li6PS5Cl solid electrolyte.

[0299] <Comparative example 2-2: Li 5.58 B 0.02 P 0.98 S 4.9 Cl 1.04 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 2-1 was carried out, except that 0.02 mol% of BCl3 was further added as a doping source material based on the total moles of the mixture to form a mixture. 5.58 B 0.02 P 0.98 S 4.9 Cl 1.04 A solid electrolyte was prepared.

[0300] <Comparative example 2-3: Li 5.4 Si 0.1 P 0.9 S 4.5 Cl 1.3 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 2-1 was carried out, except that 0.1 mol% of SiCl4 was further added as a doping source material based on the total moles of the mixture to form a mixture. 5.4 Si 0.1 P 0.9 S 4.5 Cl 1.3 A solid electrolyte was prepared.

[0301] [Experimental Example 3: Analysis of the composition of solid electrolytes and evaluation of ionic conductivity] The solid electrolytes prepared according to the examples and comparative examples were analyzed for composition and subjected to an experiment to evaluate ionic conductivity, and the results are shown in Table 2. The specific experimental method is as follows.

[0302] (1) Analysis of the composition of solid electrolyte The composition of the solid electrolyte was measured using an ICP (Inductively Coupled Plasma Emission Spectrometry) device. All synthesized solid electrolyte samples were dissolved in HNO3 solvent, then diluted with DI water, and the element content was measured using the ICP device.

[0303] (2) Evaluation of ionic conductivity An experiment to evaluate the ionic conductivity of solid electrolytes was conducted using a pressure powder cell. Specifically, the synthesized solid electrolyte was crushed and then fabricated into pellets under a pressure of 300 MPa. A cell was then fabricated at a pressure of 700 MPa using SUS as the working electrode. A voltage of 10 mV was then applied at 30°C to measure the impedance.

[0304] [Table 2]

[0305] Referring to Table 2, it can be seen that Comparative Example 2-2, which was doped only with boron, and Comparative Example 2-3, which was doped only with silicon, had significantly lower ionic conductivity than Examples 2-1 to 2-14, which were doped with both boron and silicon. It can also be seen that the ionic conductivity was actually lower than that of Comparative Example 2-1, which had the basic argyrodite crystal structure.

[0306] On the other hand, in Examples 2-2 to 2-7 and 2-10 to 2-14, where x is in the range of 0.014 to 0.05 and y is in the range of 0.04 to 0.4, the ionic conductivity was 3.3 mS / cm or more, which was superior to that of Comparative Example 2-1, which has the basic argyrodite crystal structure.

[0307] In particular, in Examples 2-3 to 2-5 and 2-11 to 2-12, in which x is in the range of 0.02 to 0.035 and y is in the range of 0.08 to 0.25, the ionic conductivity was 4 mS / cm or more, which was significantly superior to that of Comparative Example 2-1, which has the basic argyrodite crystal structure.

[0308] Considering the boron-based compound and silicon-based compound mixed during the preparation of the solid electrolyte, in Examples 2-2 to 2-7 and 2-10 to 2-14 in which the content of BCl3 mixed was within the range of 0.014 to 0.05 mol% and the content of SiCl4 mixed was within the range of 0.04 to 0.4 mol%, the ionic conductivity was 3.3 mS / cm or more, which was superior to that of Comparative Example 2-1, which had a basic argyrodite crystal structure.

[0309] In particular, in Examples 2-3 to 2-5 and 2-11 to 2-12, in which the content of BCl3 added was within the range of 0.02 to 0.035 mol% and the content of SiCl4 added was within the range of 0.08 to 0.25 mol%, the ionic conductivity was 4 mS / cm or more, which was significantly superior to that of Comparative Example 2-1, which had the basic argyrodite crystal structure.

[0310] [Experimental Group III. Third Example (B and Sn doping)] Example 3-1: Li 5.76 B 0.02 Sn 0.02 P 0.96 S 4.8 Cl 1.1 Solid Electrolyte Manufacturing The final product is Li6(1-x-y) B x Sn y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified in a solid electrolyte so that x = 0.02 and y = 0.02, and BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and the mixture was mixed at 300 rpm for about 8 hours using a planetary mill to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550°C in an argon (Ar) atmosphere to form Li 5.76 B 0.02 Sn 0.02 P 0.96 S 4.8 Cl 1.1 A solid electrolyte was prepared.

[0311] Example 3-2: Li 5.58 B 0.02 Sn 0.05 P 0.93 S 4.65 Cl 1.19 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.05, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.05 mol% based on 100 mol% of the total reactants. 5.58 B 0.02 Sn 0.05 P 0.93 S 4.65 Cl 1.19 A solid electrolyte was prepared.

[0312] Example 3-3: Li 5.28 B 0.02 Sn 0.1 P 0.88 S4.4 Cl 1.34 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.28 B 0.02 Sn 0.1 P 0.88 S 4.4 Cl 1.34 A solid electrolyte was prepared.

[0313] Example 3-4: Li 4.98 B 0.02 Sn 0.15 P 0.83 S 4.15 Cl 1.49 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.15, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.15 mol% based on 100 mol% of the total reactants. 4.98 B 0.02 Sn 0.15 P 0.83 S 4.15 Cl 1.49 A solid electrolyte was prepared.

[0314] Example 3-5: Li 4.68 B 0.02 Sn 0.2 P 0.78 S 3.9 Cl 1.64 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.2, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.2 mol% based on 100 mol% of the total reactants. 4.68 B 0.02 Sn 0.2 P 0.78 S 3.9 Cl 1.64 A solid electrolyte was prepared.

[0315] Example 3-6: Li 4.08 B 0.02 Sn 0.3 P 0.68 S 3.4 Cl 1.94 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.3, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.3 mol% based on 100 mol% of the total reactants. 4.08 B 0.02 Sn 0.3 P 0.68 S 3.4 Cl 1.94 A solid electrolyte was prepared.

[0316] Example 3-7: Li 3.48 B 0.02 Sn 0.4 P 0.58 S 2.9 Cl 2.24 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.02 and y = 0.4, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.4 mol% based on 100 mol% of the total reactants. 3.48B 0.02 Sn 0.4 P 0.58 S 2.9 Cl 2.24 A solid electrolyte was prepared.

[0317] Example 3-8: Li 5.37 B 0.005 Sn 0.1 P 0.895 S 4.475 Cl 1.31 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.005 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.005 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.37 B 0.005 Sn 0.1 P 0.895 S 4.475 Cl 1.31 A solid electrolyte was prepared.

[0318] Example 3-9: Li 5.34 B 0.01 Sn 0.1 P 0.89 S 4.45 Cl 1.32 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.01 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.01 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.34 B 0.01 Sn 0.1 P 0.89 S 4.45 Cl 1.32 A solid electrolyte was prepared.

[0319] Example 3-10: Li 5.31 B 0.015 Sn0.1 P 0.885 S 4.425 Cl 1.33 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.015 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.015 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.31 B 0.015 Sn 0.1 P 0.885 S 4.425 Cl 1.33 A solid electrolyte was prepared.

[0320] Example 3-11: Li 5.25 B 0.025 Sn 0.1 P 0.875 S 4.375 Cl 1.35 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.025 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.025 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.25 B 0.025 Sn 0.1 P 0.875 S 4.375 Cl 1.35 A solid electrolyte was prepared.

[0321] Example 3-12: Li 5.22 B 0.03 Sn 0.1 P 0.87 S 4.35 Cl 1.36 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.03 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.03 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.22 B 0.03 Sn 0.1 P 0.87 S 4.35 Cl 1.36 A solid electrolyte was prepared.

[0322] Example 3-13: Li 5.16 B 0.04 Sn 0.1 P 0.86 S 4.3 Cl 1.38 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.04 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.04 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.16 B 0.04 Sn 0.1 P 0.86 S 4.3 Cl 1.38 A solid electrolyte was prepared.

[0323] Example 3-14: Li 5.1 B 0.05 Sn 0.1 P 0.85 S 4.25 Cl 1.4 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, BCl3, and SnCl4 were quantified so that x = 0.05 and y = 0.1, and the same procedure as in Example 3-1 was carried out except that BCl3 was adjusted to 0.05 mol% based on 100 mol% of the total reactants, and SnCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants.5.1 B 0.05 Sn 0.1 P 0.85 S 4.25 Cl 1.4 A solid electrolyte was prepared.

[0324] <Comparative Example 3-1: Preparation of Li6PS5Cl solid electrolyte> The reactants Li2S, P2S5 and LiCl were mixed in a planetary mill at 300 rpm for approximately 8 hours to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550° C. in an argon (Ar) atmosphere to prepare a Li6PS5Cl solid electrolyte.

[0325] <Comparative example 3-2: Li 5.58 B 0.02 P 0.98 S 4.9 Cl 1.04 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 3-1 was carried out, except that BCl3 was further added as a doping source material at 0.02 mol% based on the total moles of the mixture to form a mixture. 5.58 B 0.02 P 0.98 S 4.9 Cl 1.04 A solid electrolyte was prepared.

[0326] <Comparative example 3-3: Li 5.4 Sn 0.1 P 0.9 S 4.5 Cl 1.3 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 3-1 was carried out, except that SnCl4 was further added as a doping source material in an amount of 0.1 mol% based on the total moles of the mixture to form a mixture. 5.4 Sn 0.1 P 0.9 S 4.5 Cl 1.3 A solid electrolyte was prepared.

[0327] [Experimental Example 5: Analysis of the composition of solid electrolytes and evaluation of ionic conductivity] The solid electrolytes prepared according to the examples and comparative examples were analyzed for composition and subjected to an experiment to evaluate ionic conductivity, and the results are shown in Table 3 below. The specific experimental method is as follows.

[0328] (1) Analysis of solid electrolyte composition The composition of the solid electrolyte was measured using an ICP (Inductively Coupled Plasma Emission Spectrometry) device. More specifically, all the synthesized solid electrolyte samples were dissolved in HNO3 solvent, then diluted with DI water, and the element contents were measured using the ICP device.

[0329] (2) Evaluation of ionic conductivity An experiment to evaluate the ionic conductivity of solid electrolytes was conducted using a pressure powder cell. Specifically, the synthesized solid electrolyte was crushed and then fabricated into pellets under a pressure of 300 MPa. A cell was then fabricated at a pressure of 700 MPa using SUS as the working electrode. A voltage of 10 mV was then applied at 30°C to measure the impedance.

[0330] [Table 3]

[0331] Referring to Table 3, Comparative Example 3-2, which was doped only with boron, and Comparative Example 3-3, which was doped only with tin, exhibited significantly lower ionic conductivity than Examples 3-1 to 3-14, which were doped with both boron and tin, and were even lower than Comparative Example 3-1, which had a basic argyrodite crystal structure. In contrast, the solid electrolytes of Examples 3-2 to 3-7 and Examples 3-10 to 3-13, in which the ranges of x and y were appropriately adjusted, exhibited superior ionic conductivity compared to Comparative Example 3-1, which had a basic argyrodite crystal structure. In particular, Examples 3-3 to 3-4 and Examples 3-11 to 3-12 exhibited excellent ionic conductivities of 4.0 mS / cm or higher.

[0332] Considering the content of boron-based compounds and tin-based compounds mixed during the manufacturing process of the solid electrolyte, the solid electrolytes according to Examples 3-2 to 3-7 and 3-10 to 3-13, in which the content of BCl3 and the content of SnCl4 were appropriately adjusted, were confirmed to have superior ionic conductivity compared to Comparative Example 1, which has a basic argyrodite crystal structure. In particular, the solid electrolytes according to Examples 3-3 to 3-4 and 3-11 to 3-12 were confirmed to have extremely superior ionic conductivities of 4.0 mS / cm or more.

[0333] [Experimental Example 6: XRD Diffraction Analysis Experiment] The solid electrolytes prepared in Examples 3-3, 3-11, and Comparative Example 3-1 were subjected to XRD analysis, and the results are shown in FIG.

[0334] Referring to FIG. 1, it can be seen that in Examples 3-3 and 3-11, peaks are present at 30.2°≦2θ≦30.3°. It was thus confirmed that the presence of these diffraction peak values ​​prevents the deterioration of the ionic conductivity and cell performance of the argyrodite-type solid electrolyte.

[0335] [Experimental Group IV. Fourth Example (Al and Si doping)] Example 4-1: Li 5.28 Al 0.02 Si 0.1 P 0.88 S 4.4 Cl 1.34 Solid Electrolyte Manufacturing The final product is Li 6(1-x-y) Al x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified in a solid electrolyte so that x = 0.02 and y = 0.1, and AlCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. The mixture was mixed at 300 rpm for approximately 8 hours using a planetary mill to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550°C in an argon (Ar) atmosphere to form Li 5.28 Al 0.02 Si 0.1 P 0.88 S 4.4 Cl 1.34 A solid electrolyte was prepared.

[0336] Example 4-2: Li 4.68 Al 0.02 Si 0.2 P 0.78 S 3.9 Cl 1.64 Solid Electrolyte Manufacturing The reactants LiS, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.2, and the AlCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and the SiCl4 was adjusted to 0.2 mol% based on 100 mol% of the total reactants. 4.68 Al 0.02 Si 0.2 P 0.78 S 3.9 Cl1.64 A solid electrolyte was prepared.

[0337] Example 4-3: Li 4.08 Al 0.02 Si 0.3 P 0.68 S 3.4 Cl 1.94 Solid Electrolyte Manufacturing The reactants LiS, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.3, and the AlCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and the SiCl4 was adjusted to 0.3 mol% based on 100 mol% of the total reactants. 4.68 Al 0.02 Si 0.2 P 0.78 S 3.9 Cl 1.64 A solid electrolyte was prepared.

[0338] Example 4-4: Li 3.48 Al 0.02 Si 0.4 P 0.58 S 2.9 Cl 2.24 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.02 and y = 0.4, and the same procedure as in Example 4-1 was carried out except that AlCl3 was adjusted to 0.02 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.4 mol% based on 100 mol% of the total reactants. 3.48 Al 0.02 Si 0.4 P 0.58 S 2.9 Cl 2.24 A solid electrolyte was prepared.

[0339] Example 4-5: Li 5.34 Al 0.01 Si 0.1 P 0.89 S 4.45 Cl 1.32Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.01 and y = 0.1, and the same procedure as in Example 4-1 was carried out except that AlCl3 was adjusted to 0.01 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.34 Al 0.01 Si 0.1 P 0.89 S 4.45 Cl 1.32 A solid electrolyte was prepared.

[0340] Example 4-6: Li 5.22 Al 0.03 Si 0.1 P 0.87 S 4.35 Cl 1.36 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.03 and y = 0.1, and the same procedure as in Example 4-1 was carried out except that AlCl3 was adjusted to 0.03 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.22 Al 0.03 Si 0.1 P 0.87 S 4.35 Cl 1.36 A solid electrolyte was prepared.

[0341] Example 4-7: Li 5.16 Al 0.04 Si 0.1 P 0.86 S 4.3 Cl 1.38 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.04 and y = 0.1, and the same procedure as in Example 4-1 was carried out except that AlCl3 was adjusted to 0.04 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.16 Al 0.04 Si 0.1 P 0.86 S 4.3 Cl 1.38 A solid electrolyte was prepared.

[0342] Example 4-8: Li 5.1 Al 0.05 Si 0.1 P 0.85 S 4.25 Cl 1.4 Solid Electrolyte Manufacturing The reactants Li2S, P2S5, LiCl, AlCl3, and SiCl4 were quantified so that x = 0.05 and y = 0.1, and the same procedure as in Example 4-1 was carried out except that AlCl3 was adjusted to 0.05 mol% based on 100 mol% of the total reactants, and SiCl4 was adjusted to 0.1 mol% based on 100 mol% of the total reactants. 5.1 Al 0.05 Si 0.1 P 0.85 S 4.25 Cl 1.4 A solid electrolyte was prepared.

[0343] <Comparative Example 4-1: Production of Li6PS5Cl solid electrolyte> The reactants Li2S, P2S5 and LiCl were mixed in a planetary mill at 300 rpm for approximately 8 hours to form a mixture. The mixture was then subjected to a pressure of 300 MPa to form pellets. Next, the pellet was heat-treated at 550° C. in an argon (Ar) atmosphere to prepare a Li6PS5Cl solid electrolyte.

[0344] <Comparative example 4-2: Li5.58 Al 0.02 P 0.98 S 4.9 Cl 1.04 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 4-1 was carried out, except that AlCl3 was further added as a doping source material at 0.02 mol% based on the total moles of the mixture to form a mixture. 5.58 Al 0.02 P 0.98 S 4.9 Cl 1.04 A solid electrolyte was prepared.

[0345] <Comparative example 4-3: Li 5.4 Si 0.1 P 0.9 S 4.5 Cl 1.3 Solid Electrolyte Manufacturing The same procedure as in Comparative Example 4-1 was carried out, except that 0.1 mol% of SiCl4 was further added as a doping source material based on the total moles of the mixture to form a mixture. 5.4 Si 0.1 P 0.9 S 4.5 Cl 1.3 A solid electrolyte was prepared.

[0346] [Experimental Example 7: Analysis of the composition of solid electrolyte] The solid electrolytes prepared according to the examples and comparative examples were analyzed for their compositions, and the results are shown in Table 4 below. 6(1-x-y) Al x Si y P (1-x-y) S 5(1-x-y) D 1(1-x-y)+3x+4y In the composition formula, the x and y values, as well as the mole percentages of AlCl3 and SiCl4 used in the mixing in the manufacturing step, are also shown. The specific experimental method is as follows.

[0347] The composition of the solid electrolyte was measured using an ICP (Inductively Coupled Plasma Emission Spectrometry) device. More specifically, all the synthesized solid electrolyte samples were dissolved in HNO3 solvent, then diluted with DI water, and the element contents were measured using the ICP device.

[0348] [Table 4]

[0349] Referring to Table 4, it was confirmed that the targeted solid electrolyte composition could be obtained by appropriately adjusting the mole percentages of AlCl3 and SiCl4 during the manufacturing process to match the targeted values ​​of x and y.

[0350] Tables 5 and 6 below are summaries of the evaluation results of the solid electrolyte ionic conductivity and the electrochemical properties of the lithium secondary batteries according to Experimental Examples 7 and 8, which will be described later.

[0351] [Table 5]

[0352] [Table 6]

[0353] [Experimental Example 7: Evaluation of ionic conductivity of solid electrolyte at 30°C] An experiment to evaluate the ionic conductivity of the solid electrolytes prepared according to the examples and comparative examples was carried out. The specific experimental method is as follows.

[0354] An experiment to evaluate the ionic conductivity of solid electrolytes was conducted using a pressure powder cell. Specifically, the synthesized solid electrolyte was crushed and then fabricated into pellets under a pressure of 300 MPa. A cell was then fabricated at a pressure of 70 MPa using SUS as the working electrode. A voltage of 10 mV was then applied at 30°C to measure the impedance.

[0355] Referring to Tables 5 and 6, it was confirmed that the solid electrolytes of Comparative Example 4-2, which was doped only with aluminum, and Comparative Example 4-3, which was doped only with silicon, had lower ionic conductivity than the solid electrolyte of Comparative Example 4-1, which had the basic argyrodite crystal structure.

[0356] In contrast, the solid electrolytes of Examples 4-2 to 4-3 and Examples 4-6 to 4-7, in which aluminum and silicon were all doped and the ranges of x and y were appropriately adjusted, were confirmed to have superior ionic conductivity compared to Comparative Example 4-1, which had the basic argyrodite crystal structure.

[0357] Considering the content of aluminum-based compounds and silicon-based compounds mixed during the manufacturing process of the solid electrolyte, it was confirmed that the solid electrolytes of Examples 4-2 to 4-3 and 4-6 to 4-7, in which the content of AlCl3 and SiCl4 mixed was appropriately adjusted, had superior ionic conductivity compared to Comparative Example 4-1, which had a basic argyrodite crystal structure.

[0358] [Experimental Example 8: Evaluation of electrochemical properties of lithium secondary batteries] When the solid electrolytes prepared according to the examples and comparative examples were applied to batteries, capacity and life characteristics were evaluated. The specific experimental method is as follows.

[0359] The solid electrolytes of the comparative example and the example were electrochemically evaluated using a pressure powder cell. The composite positive electrode had a positive electrode: solid electrolyte: conductive material (Denka Black) ratio of 70:29:1 wt%, and the thickness was 0.785 cm 2An electrode was fabricated with a 20.0 mg loading at an area of ​​1000 μm and densified to 300 MPa. An indium-lithium counter electrode was then bonded at 50 MPa, and the cell was clamped at the same pressure. After fabrication, the cells were aged at room temperature for 2 hours and then subjected to charge-discharge tests. Capacity evaluation was based on a reference capacity of 180 mAh / g, and the charge-discharge conditions were CC / CV 1.9 to 3.60 V with a 1 / 20 C cutoff. Initial capacity was measured under 0.1 C charge / 0.1 C discharge conditions. Lifetime characteristics were evaluated by calculating the discharge capacity after 30 cycles relative to the initial discharge capacity as a percentage of the first discharge capacity after 30 charge-discharge cycles.

[0360] Referring to Tables 5 and 6, it was confirmed that in Comparative Example 4-2, which was doped only with aluminum, and Comparative Example 4-3, which was doped only with silicon, the charge capacity, discharge capacity, and lifespan characteristics were significantly deteriorated compared to Comparative Example 4-1, which had the basic argyrodite crystal structure.

[0361] In contrast, in Examples 4-1 to 4-8, in which aluminum and silicon were all doped and the ranges of x and y were appropriately adjusted, it was confirmed that the electrochemical properties were generally superior to those of Comparative Example 4-1, which had the basic argyrodite crystal structure.

[0362] In particular, in Examples 4-2 to 4-3 and Examples 4-6 to 4-7, in which the ranges of x and y were more appropriately adjusted, it was confirmed that not only the ionic conductivity but also the discharge capacity, initial efficiency, and life characteristics were equally excellent.

[0363] In summary, this example confirmed that the ionic conductivity of the solid electrolyte and the electrochemical properties of the battery can be improved simultaneously by doping aluminum and silicon into the basic argyrodite crystal structure and appropriately adjusting the doping amounts of aluminum and silicon.

[0364] [Experimental Group V. Fifth Example (B and Ge doping)] <Comparative Example 5-1-Li6PS5Cl solid electrolyte> Li6PS5Cl is synthesized by dry milling. Specifically, Li2S, P2S5, and LiCl are mixed in a planetary mill at 300 rpm for 8 hours, then pelletized at 300 MPa and heat-treated at 550°C in an argon (Ar) atmosphere.

[0365] Comparative Example 5-2 - Li6PS5Cl solid electrolyte containing 0.02 mol% of B The solid electrolyte prepared in Comparative Example 5-1 was synthesized under the same conditions as in Comparative Example 5-1, except that 0.02 mol % of BCl 3 was added as a doping material.

[0366] Comparative Example 5-3 - Li6PS5Cl solid electrolyte containing 0.1 mol% of Ge The solid electrolyte prepared in Comparative Example 5-1 was synthesized under the same conditions as in Comparative Example 5-1, except that 0.1 mol % of GeCl 3 was added as a doping material.

[0367] <Reference Example 5-1 - Li6PS5Cl solid electrolyte containing 0.02 mol% B and 0.1 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.02 mol % of BCl3 and 0.2 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0368] <Example 5-1 - Li6PS5Cl solid electrolyte containing 0.02 mol% B and 0.2 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.02 mol % of BCl3 and 0.2 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0369] Example 5-2 - Li6PS5Cl solid electrolyte containing 0.02 mol% B and 0.3 mol% Ge The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.02 mol % of BCl3 and 0.3 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0370] <Reference Example 5-2 - Li6PS5Cl solid electrolyte containing 0.02 mol% B and 0.4 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.02 mol % of BCl3 and 0.4 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0371] <Reference Example 5-3 - Li6PS5Cl solid electrolyte containing 0.01 mol% of B and 0.1 mol% of Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.01 mol % of BCl3 and 0.1 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0372] <Example 5-3 - Li6PS5Cl solid electrolyte containing 0.03 mol% B and 0.1 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.03 mol % of BCl3 and 0.1 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0373] <Example 5-4 - Li6PS5Cl solid electrolyte containing 0.04 mol% B and 0.1 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.04 mol % of BCl3 and 0.1 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0374] <Reference Example 5-4 - Li6PS5Cl solid electrolyte containing 0.05 mol% B and 0.1 mol% Ge> The solid electrolyte was synthesized under the same conditions as in Comparative Example 5-1, except that 0.05 mol % of BCl3 and 0.1 mol % of GeCl4 were added to the solid electrolyte prepared in Comparative Example 5-1.

[0375] [Experimental Example 9: Composition Analysis] The composition analysis of the examples and comparative examples was carried out by chemical analysis to confirm the actual composition of the synthesized samples. The composition of the solid electrolyte was measured using an ICP (Inductively Coupled Plasma Emission Spectrometry) device. Specifically, the samples prepared in the examples and comparative examples were dissolved in HNO3 solvent, then diluted with DI water, and the element content was measured using the ICP device.

[0376] [Experimental Example 10: Evaluation of ionic conductivity at 30°C] The solid electrolytes of the examples and comparative examples were electrochemically evaluated using a pressure powder cell. The synthesized solid electrolyte was crushed and formed into a 300 MPa pellet. The cell was then clamped under a pressure of 70 MPa using Sodium hydroxide as the working electrode, and the ionic conductivity was measured by impedance. Impedance was measured by applying 10 mV at 30°C.

[0377] [Experimental Example 11: Evaluation of cell electrochemical characteristics at 30°C] The solid electrolytes of the comparative example and the example were electrochemically evaluated using a pressure powder cell. The composite positive electrode had a positive electrode: solid electrolyte: conductive material (Denka Black) ratio of 70:29:1 wt%, and the thickness was 0.785 cm. 2 The electrodes were fabricated with a loading of 20.0 mg and densified to 300 MPa.

[0378] The cells were then bonded at 50 MPa using an indium-lithium counter electrode and clamped together at the same pressure. After aging at room temperature for 2 hours, charge and discharge tests were performed. The capacity was evaluated based on a reference capacity of 180 mAh / g, with CC / CV conditions of 1.9 to 3.60 V and a 1 / 20 C cutoff. The initial capacity was measured under 0.1 C charge / 0.1 C discharge conditions.

[0379] [Table 7]

[0380] [Table 8]

[0381] [Table 9]

[0382] From Tables 7 to 9, it was confirmed that the ionic conductivity, charge capacity, discharge capacity, initial efficiency, and lifespan of Comparative Examples 5-1 to 5-3, which correspond to the cases where BCl3 and GeCl4 were not added at all or where BCl3 and GeCl4 were not added simultaneously, were lower than those of the Examples of the present invention. Furthermore, it was confirmed that when GeCl4 was added in a small amount of 0.1 mol%, as in Reference Example 5-1, the ionic conductivity, charge capacity, discharge capacity, and lifespan were inferior to those of the Examples. It was confirmed that when GeCl4 was added in an excessive amount of 0.4 mol%, as in Reference Example 5-2, the charge capacity and lifespan were inferior to those of the Examples.

[0383] In addition, when the content of BCl3 was added in a small amount of 0.01 mol% as in Reference Example 5-3, it was confirmed that the ionic conductivity, charge capacity, discharge capacity, and lifespan were inferior to those of the Examples.When the content of BCl3 was added in an excessive amount of 0.05 mol% as in Reference Example 5-4, it was confirmed that the ionic conductivity and charge capacity were inferior to those of the Examples.

[0384] The material properties of the argyrodite-type solid electrolyte of the present invention can be confirmed by examining the examples in Tables 7 to 9. Specifically, it was confirmed that the ionic conductivity was superior when BCl3 and GeCl4 were mixed together, compared to when BCl3 or GeCl4 was mixed alone. In the case of BCl3, it was confirmed that the ionic conductivity, charge capacity, discharge capacity, initial efficiency, and life characteristics were excellent when 0.02 to 0.04 mol% of BCl3 was included. Furthermore, it was confirmed that the ionic conductivity, charge capacity, discharge capacity, initial efficiency, and life characteristics were excellent when 0.1 to 0.3 mol%, specifically 0.2 to 0.3 mol%, of GeCl4 was included. The sulfide-based solid electrolyte of the present invention thus prepared exhibited flexible and soft properties, excellent moldability, and strong interfacial contact with the active material, and therefore exhibited superior battery properties compared to other oxide all-solid-state batteries.

[0385] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention.

[0386] Therefore, the true scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. containing lithium (Li), phosphorus (P), sulfur (S) and halogen elements, A sulfide-based solid electrolyte having an argyrodite-based crystal structure, at least a portion of which is doped with one or more first doping elements selected from Group 13 elements and one or more second doping elements selected from Group 14 elements.

2. 2. The sulfide-based solid electrolyte according to claim 1, wherein the first doping element is at least one selected from the group consisting of B, Al, Ga, In, and Ti, and the second doping element is at least one selected from the group consisting of Si, Ge, and Sn.

3. The sulfide-based solid electrolyte according to claim 1 , wherein the first doping element is In and the second doping element is Si.

4. The sulfide-based solid electrolyte of claim 3 , wherein the first doping element is contained in an amount of 0.005 to 0.04 mol % based on the total number of moles of the solid electrolyte.

5. The sulfide-based solid electrolyte of claim 3 , wherein the second doping element is contained in an amount of 0.02 to 0.2 mol % based on the total number of moles of the solid electrolyte.

6. The sulfide-based solid electrolyte according to claim 3 , wherein the solid electrolyte is represented by the following chemical formula 1: [Chemical formula 1] Li ６（１－ｘ－ｙ） I ｘ Yes ｙ P （１－ｘ－ｙ） S ５（１－ｘ－ｙ） C １（１－ｘ－ｙ）＋３ｘ＋４ｙ In the above formula 1, C is at least one of F, Cl, Br and I, 0.1<x<0.5, and 0.05<y<0.

5.

7. The sulfide-based solid electrolyte according to claim 1 , wherein the first doping element is B and the second doping element is Si.

8. The sulfide-based solid electrolyte according to claim 7, wherein the solid electrolyte is represented by the following chemical formula 2: [Chemical formula 2] Li ６（１－ｘ－ｙ） B ｘ Yes ｙ P （１－ｘ－ｙ） S ５（１－ｘ－ｙ） D １（１－ｘ－ｙ）＋３ｘ＋４ｙ In Formula 2, D is F, Cl, Br, I, or a combination thereof, and 0.014≦x≦0.05 and 0.04≦y≦0.

4.

9. The sulfide-based solid electrolyte according to claim 8, wherein 0.02≦x≦0.

035.

10. The sulfide-based solid electrolyte according to claim 8, wherein 0.08≦y≦0.

25.

11. The sulfide-based solid electrolyte according to claim 1 , wherein the first doping element is B and the second doping element is Sn.

12. The sulfide-based solid electrolyte according to claim 11, wherein the solid electrolyte is represented by the following chemical formula 3: [Chemical formula 3] Li ６（１－ｘ－ｙ） B ｘ Sn ｙ P （１－ｘ－ｙ） S ５（１－ｘ－ｙ） D １（１－ｘ－ｙ）＋３ｘ＋４ｙ In Formula 3, D is F, Cl, Br, I, or a combination thereof, and 0.013≦x≦0.043 and 0.04≦y≦0.

42.

13. The sulfide-based solid electrolyte according to claim 12, wherein 0.02≦x≦0.

035.

14. The sulfide-based solid electrolyte according to claim 12, wherein 0.08≦y≦0.

17.

15. The sulfide-based solid electrolyte according to claim 1 , wherein the first doping element is Al and the second doping element is Si.

16. The sulfide-based solid electrolyte according to claim 1 , wherein the solid electrolyte is represented by the following chemical formula 4: [Chemical formula 4] Li ６（１－ｘ－ｙ） Al ｘ Yes ｙ P （１－ｘ－ｙ） S ５（１－ｘ－ｙ） D １（１－ｘ－ｙ）＋３ｘ＋４ｙ In Formula 4, D is F, Cl, Br, I, or a combination thereof, and 0.01≦x≦0.05 and 0.1≦y≦0.

4.

17. The sulfide-based solid electrolyte according to claim 16, wherein 0.02≦x≦0.

045.

18. The sulfide-based solid electrolyte according to claim 16, wherein 0.15≦y≦0.

35.

19. The sulfide-based solid electrolyte according to claim 1 , wherein the first doping element is B and the second doping element is Ge.

20. The sulfide-based solid electrolyte of claim 19 , wherein the first doping element is contained in an amount of 0.02 to 0.04 mol % based on the total number of moles of the solid electrolyte.

21. The sulfide-based solid electrolyte of claim 19 , wherein the second doping element is contained in an amount of 0.1 to 0.3 mol % based on the total number of moles of the solid electrolyte.

22. The sulfide-based solid electrolyte according to claim 19, wherein the solid electrolyte is represented by the following chemical formula 5: [Chemical formula 5] Li ６（１－ｘ－ｙ） B ｘ Ge ｙ P （１－ｘ－ｙ） S ５（１－ｘ－ｙ） C １（１－ｘ－ｙ）＋３ｘ＋４ｙ In the above formula 5, C is at least one of F, Cl, Br and I, 0.02<x<0.04, and 0.1<y<0.

3.

23. a positive electrode; a negative electrode; and a solid electrolyte layer located between the positive electrode and the negative electrode; A lithium secondary battery, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte layer comprises the solid electrolyte according to claim 1.

24. An electric vehicle comprising the lithium secondary battery of claim 23.

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