Sulfide-based solid electrolyte, lithium ion battery and vehicle

Abstract

The invention provides a sulfide-based solid electrolyte, a lithium ion battery and a vehicle. A sulfide-based solid electrolyte having an argyrodite crystal structure is represented by the chemical formula Li6-aPS5-aX1 + a, where X is one or more halogen elements selected from the group consisting of Cl, Br, I, and combinations thereof, and the range of "a" is from 0 to 0.5. A halogen element is doped at 4a, 4c sites or both within the argyrodite structure. The variants of composition include Li5.5 PS4.5 X1.5 where X may be a single or mixed halogen, such as Cl, Br, I, or a combination thereof. The solid electrolyte may be synthesized using a ball milling process to ensure a uniform halogen distribution and achieve a disordered crystal structure that enhances ductility and breaking strength. In order to improve performance, mechanical properties such as formation energy, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are optimized. In addition, the electrolyte may be used in a lithium ion battery suitable for vehicle applications.

Description

Technical Field

[0001] The present disclosure relates to the field of solid electrolytes for electrochemical devices. More specifically, the present invention relates to sulfide-based solid electrolytes having an argyrodite crystal structure that are designed to enhance mechanical properties such as ductility and fracture strength. These solid electrolytes are particularly suitable for use in lithium-ion batteries, which can be used in various electronic devices and electric vehicles. The present disclosure also covers methods for synthesizing these electrolytes and their integration into battery systems. Background Art

[0002] Lithium-ion batteries are widely used in various devices that require energy storage. Depending on the application field of lithium-ion batteries, various battery properties are required, such as high energy density, long cycle life, fast charge and discharge, high / low temperature battery operation performance, etc.

[0003] Recently, as the automotive industry seeks to address environmental concerns caused by carbon dioxide (CO2) and avoid the use of fossil fuels, it has shown significant interest in electric vehicles using secondary batteries as a means of transportation. Currently developed lithium-ion batteries offer a range of approximately 400 km on a single charge, but they still face challenges such as instability at high temperatures and potential fire. To address these challenges, numerous companies are competing to develop next-generation secondary batteries.

[0004] All-solid-state batteries, which are attracting attention as next-generation secondary batteries, have all components made of solids and thus have advantages over lithium-ion batteries using flammable organic solvents as electrolytes, such as low fire and explosion risks and high mechanical strength.

[0005] As solid electrolytes for these all-solid-state batteries, oxide-based solid electrolytes and sulfide-based solid electrolytes are available, and in particular, intensive research into sulfide-based solid electrolytes with high lithium ion conductivity is underway. However, most patents for solid electrolyte compositions aim to improve ionic conductivity and electrochemical stability, and do not specify the mechanical properties of the solid electrolytes. Summary of the Invention

[0006] The present disclosure relates to sulfide-based solid electrolytes with improved ductility and fracture strength, and more particularly to sulfide-based solid electrolytes wherein ductility and fracture strength can be improved by doping a sulfide-based solid electrolyte having an argyrodite crystal structure with at least two, preferably three, halogen elements.

[0007] The present disclosure has been made in view of the problems encountered in the related art, and an object of the present disclosure is to provide a sulfide-based solid electrolyte that exhibits favorable mechanical properties as a solid electrolyte for an all-solid-state battery.

[0008] Specifically, an object of the present disclosure is to provide a sulfide-based solid electrolyte having high ductility and fracture strength by expanding the type of halogen elements doped with the sulfide-based solid electrolyte having an argyrodite crystal structure to a ternary composition.

[0009] The purpose of the present disclosure is not limited to the above content. Through the following description, the purpose of the present disclosure will be clearly understood and achieved through the technical means and combinations described in the claims.

[0010] In some embodiments, the sulfide-based solid electrolyte comprises an argyrodite crystal structure and has the chemical formula Li 6-a PS 5-a X 1+a , wherein X is one or more halogen elements selected from Cl, Br, I and combinations thereof, and a is 0 to 0.5. The argyrodite crystal structure is doped with one or more halogen elements at the 4a site, the 4c ​​site, or both. In some embodiments, the sulfide-based solid electrolyte is composed of the formula Li 5.5 PS 4.5 X 1.5 In some embodiments, X includes at least two halogen elements selected from Cl, Br, and I. The electrolyte may be of the formula Li 5.5 PS 4.5 (Br, Cl) 1.5 、Li 5.5 PS 4.5 (Cl, I) 1.5 or Li 5.5 PS 4.5 (Br, I) 1.5 express.

[0011] In some embodiments, X includes all of the three halogen elements Cl, Br, and I, and is represented by the chemical formula Li 5.5 PS 4.5 (Br, Cl, I) 1.5 or Li 5.5 PS 4.5 Br b Cl c I d, wherein b is from 0.25 to 1.00, c is from 0.25 to 1.00, and d is from 0.25 to 0.50, wherein b + c + d equals 1.5. Specifically, the electrolyte may be composed of Li 5.5 PS 4.5 Br 1.00 Cl 0.25 I 0.25 The electrolyte has a formation energy ranging from about -1.116 to about -1.224 eV / atom, a bulk modulus from about 24.39 GPa to about 26.69 GPa, a shear modulus from about 12.66 GPa to about 13.68 GPa, a Young's modulus from about 32.37 GPa to about 34.81 GPa, and a Poisson's ratio from about 0.27 to about 0.29.

[0012] In some embodiments, the electrolyte further comprises an anion selected from F- and a combination of F- and Cl, Br, or I. The electrolyte may be synthesized using a ball milling process to ensure uniform distribution of the halogen elements within the argyrodite crystal structure. The halogen elements are doped at the 4a and 4c sites to produce a more disordered crystal structure, thereby improving ductility and fracture strength.

[0013] In some embodiments, a lithium-ion battery includes a sulfide-based solid electrolyte. A vehicle may include the lithium-ion battery.

[0014] As discussed, the methods and systems suitably include the use of a controller or processor.

[0015] In another embodiment, a vehicle is provided that includes an apparatus as disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above-mentioned and other features of the present disclosure will now be described in detail with reference to certain exemplary embodiments thereof as illustrated in the accompanying drawings, which are given hereinafter by way of illustration only and thus do not limit the present disclosure, and in which:

[0017] Figure 1 shows the structure of a sulfide-based solid electrolyte according to an embodiment of the present disclosure;

[0018] Figure 2 is a view explaining the reasons for optimizing the structure of sulfide-based solid electrolytes;

[0019] Figure 3 shows a crystal structure after optimizing the structure of a sulfide-based solid electrolyte according to an embodiment using density functional theory (DFT); and

[0020] Figure 4 is a graph showing the measurement results of Young's modulus of various Examples and Comparative Examples using density functional theory (DFT). DETAILED DESCRIPTION

[0021] The above and other purposes, features and advantages of the present disclosure will be more clearly understood from the following preferred embodiments in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein and can be modified into different forms. These embodiments are provided to thoroughly explain the present disclosure and fully convey the spirit of the present disclosure to those skilled in the art.

[0022] Throughout the accompanying drawings, the same reference numerals will indicate the same or similar elements. For the sake of clarity of this disclosure, the size of the structure is depicted as being larger than its actual size. It will be understood that although terms such as "first", "second" and the like can be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this disclosure, the "first" element discussed below can be referred to as the "second" element. Similarly, the "second" element can also be referred to as the "first" element. As used herein, unless the context clearly indicates otherwise, the singular form is intended to also include the plural form.

[0023] It will be further understood that when the terms "comprising," "including," "having," etc. are used in this specification, they specify the presence of the stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. Moreover, it will be understood that when an element, such as a layer, film, region, or sheet, is referred to as being "on" another element, the element can be directly on the other element, or intervening elements can be present between the element or the other element. Similarly, when an element, such as a layer, film, region, or sheet, is referred to as being "under" another element, the element can be directly under the other element, or intervening elements can be present between the element or the other element.

[0024] It is to be understood that the term "vehicle" or "vehicular" or other similar terms as used herein includes motor vehicles, such as passenger cars in general, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft (including various boats and ships), aircraft, etc., and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels obtained from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more energy sources, for example, both gasoline-powered and electric vehicles.

[0025] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to also include the plural forms. These terms are only intended to distinguish one component from another component, and these terms do not limit the properties, arrangement or order of the constituent components. As used herein, the term "and / or" includes any and all combinations of one or more related listed items. In addition, the terms "unit", "device", "machine" and "module" described in the specification are meant to refer to a unit for processing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0026] Although the exemplary embodiments are described as using multiple units to perform the exemplary processes, it should be understood that the exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device that includes a memory and a processor and is specifically programmed to perform the processes described herein. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes described further below.

[0027] Furthermore, the control logic of the present disclosure may be embodied as non-volatile computer-readable media on a computer-readable medium containing executable program instructions executed by a processor, controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable medium may also be distributed among network-coupled computer systems so that the computer-readable media is stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0028] Unless otherwise specified or obvious from the context, as used herein, the term "about" should be understood as being within the normal tolerance range in the art, for example, within 2 standard deviations of the mean. "About" can be understood as being within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values ​​provided herein are modified by the term "about."

[0029] Unless otherwise specified, all numbers, values ​​and / or expressions used herein to express components, reaction conditions, polymer compositions and amounts of mixtures should be considered approximate, including various uncertainties that affect measurement, which are inherent in obtaining these values, etc., and therefore should be understood in all cases as modified by the term "about". In addition, unless otherwise indicated, when a numerical range is disclosed in this specification, the range is continuous and includes all values ​​from the minimum value of the range to the maximum value of the range. In addition, unless otherwise indicated, when such a range involves integer values, all integers including the minimum value to the maximum value are included.

[0030] In this specification, when a range is described for a variable, it will be understood that the variable includes all values ​​including the endpoints described in the range. For example, a range of "5 to 10" will be understood to include any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as individual values ​​of 5, 6, 7, 8, 9, and 10, and will also be understood to include any values ​​between the valid integers in the range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. In addition, for example, a range of "10% to 30%" will be understood to include subranges such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and all integers including values ​​of 10%, 11%, 12%, 13%, etc. up to 30%, and will also be understood to include any values ​​between the valid integers in the range, such as 10.5%, 15.5%, 25.5%, etc.

[0031] Sulfide-based solid electrolytes are being researched worldwide due to their high lithium-ion conductivity and electrochemical stability. Sulfide-based solid electrolytes are categorized as crystalline or amorphous (non-crystalline) depending on the presence or absence of a crystal structure. Among crystalline systems, those with sulfur-lisicon, LGPS (LiGePS), and argyrodite crystal structures are representative. Among amorphous systems, those with glass or glass-ceramic structures, resulting from differences in heat treatment temperatures, are exemplary.

[0032] A solid electrolyte with an argyrodite crystal structure is a solid electrolyte with the same crystal structure as an argyrodite-type ore having the composition of Ag8GeS6 and exhibiting lithium ion conductivity. In an all-solid-state battery, lithium ions (Li + ) Conductive Li-argyrodite structured electrolytes are generally known as Li7PS6 and Li7PS6 in which some of the Li7PS6 is doped with halogen elements.

[0033] However, most technologies and patents involving sulfide-based solid electrolytes are limited to the improvement of lithium-ion conductivity and electrochemical stability.

[0034] The sulfide-based solid electrolyte according to the present disclosure aims to increase crack resistance and durability by improving the mechanical properties of the solid electrolyte, especially ductility and fracture strength, which has a significant impact on the practical operation of all-solid-state batteries.

[0035] A sulfide-based solid electrolyte according to an aspect of the present disclosure may have an argyrodite crystal structure and may be represented by the following Chemical Formula 1.

[0036] [Chemical Formula 1] Li 6-a PS 5-a X 1+a

[0037] Here, X may be any one of halogen elements selected from the group consisting of Cl, Br, I, and a combination of Cl, Br, and I, and a may satisfy 0≤a≤0.5. For example, the sulfide-based solid electrolyte according to an embodiment of the present disclosure may have Figure 1 The structure shown.

[0038] Therefore, any of the 4a and 4c sites in the argyrodite crystal structure can be substituted by halogen doping.

[0039] Typically, in sulfide-based solid electrolytes with the argyrodite crystal structure, sulfur anions (S 2- ) can be located at the 4c ​​site. In this state, when the sulfur anion (S 2- ) is replaced by halogen elements (X), the disorder of the crystal structure may be due to the sulfur anion (S 2- ) increases with the difference in ion size and oxidation number between the anion (X-) and the halogen anion (X-).

[0040] As disclosed herein, when any one of the 4a site and the 4c ​​site is doped and substituted with a halogen element and the disorder of the crystal structure is increased compared to existing sulfide-based solid electrolytes, the bulk modulus, shear modulus, Young's modulus, etc. can be reduced, and thus the ductility and fracture strength of the solid electrolyte can be increased.

[0041] In one embodiment, the sulfide-based solid electrolyte according to the present disclosure may have a doping halogen element composition ratio of 1.5. For example, the sulfide-based solid electrolyte may include an electrolyte represented by the following Chemical Formula 2.

[0042] [Chemical formula 2] Li 5.5 PS 4.5 X 1.5

[0043] Here, X is a halogen element selected from the group consisting of Cl, Br, I, and a combination of Cl, Br, and I.

[0044] Also, the halogen element used to dope the sulfide-based solid electrolyte according to the present disclosure may include at least two selected from Cl, Br, and I.

[0045] For example, the sulfide-based solid electrolyte may include one represented by the following Chemical Formula 3.

[0046] [Chemical formula 3] Li 5.5 PS 4.5 (Br, Cl) 1.5

[0047] In addition, the sulfide-based solid electrolyte may include one represented by the following Chemical Formula 4.

[0048] [Chemical Formula 4] Li 5.5 PS 4.5 (Cl, I) 1.5

[0049] In addition, the sulfide-based solid electrolyte may include one represented by the following Chemical Formula 5.

[0050] [Chemical Formula 5] Li 5.5 PS 4.5 (Br, I) 1.5

[0051] In Chemical Formulas 3 to 5, “(A, B) 1.5 ” means that elements A and B are included in respective amounts exceeding 0, but the total amount of elements A and B is limited to satisfy a composition ratio of 1.5 in the chemical formula.

[0052] Furthermore, the sulfide-based solid electrolyte according to the present disclosure is preferably configured such that the halogen element used for substitutional doping is expanded to include all ternary compositions of Cl, Br, and I. For example, the sulfide-based solid electrolyte may include one represented by the following Chemical Formula 6.

[0053] [Chemical Formula 6] Li 5.5 PS 4.5 (Br, Cl, I) 1.5

[0054] In Chemical Formula 6, “(Br, Cl, I)1.5” means that Br, Cl, and I are included in respective amounts exceeding 0, but the total amount of Br, Cl, and I is limited to satisfy the composition ratio of 1.5 in the Chemical Formula.

[0055] More specifically, the sulfide-based solid electrolyte may include one represented by the following Chemical Formula 7.

[0056] [Chemical Formula 7] Li 5.5 PS 4.5 Br b Cl c I d

[0057] Here, b, c, and d satisfy b+c+d=1.5, 0.25≤b≤1.00, 0.25≤c≤1.00, and 0.25≤d≤0.50.

[0058] The sulfide-based solid electrolyte according to the present disclosure can be configured such that the halogen elements used to dope the solid electrolyte are expanded to include all ternary compositions of Cl, Br, and I, as represented by Chemical Formulas 6 and 7, thereby exhibiting excellent lithium ion conductivity and also reducing the bulk modulus, shear modulus, Young's modulus, etc., thereby increasing the ductility and fracture strength of the solid electrolyte.

[0059] Specifically, when the sulfide-based solid electrolyte is composed of Li 5.5 PS 4.5 Br 1.00 Cl 0.25 I 0.25 Such mechanical properties can be maximized when expressed.

[0060] In one embodiment, the formation energy of the sulfide-based solid electrolyte having a ternary halogen element composition including all of Cl, Br, and I may be -1.116 eV / atom to -1.224 eV / atom. When the formation energy of the sulfide-based solid electrolyte falls within the above numerical range, the synthesis possibility may be determined to be high.

[0061] In one embodiment, the bulk modulus of the sulfide-based solid electrolyte having a ternary halogen element composition including all of Cl, Br, and I may be 24.39 GPa to 26.69 GPa.

[0062] In one embodiment, the shear modulus of the sulfide-based solid electrolyte having a ternary halogen element composition including all of Cl, Br, and I may be 12.66 GPa to 13.68 GPa.

[0063] In one embodiment, the Young's modulus of the sulfide-based solid electrolyte having a ternary halogen element composition including all of Cl, Br, and I may be 32.37 GPa to 34.81 GPa.

[0064] In one embodiment, the Poisson's ratio of the sulfide-based solid electrolyte having a ternary halogen element composition including all of Cl, Br, and I may be 0.27 to 0.29.

[0065] When the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio of the sulfide-based solid electrolyte fall within the above numerical ranges, the ductility and fracture strength of the solid electrolyte may be increased and high crack resistance may be exhibited.

[0066] Meanwhile, an all-solid-state battery generally includes an anode current collector, an anode active material layer disposed on the anode current collector and including an anode active material, a solid electrolyte layer disposed on the anode active material layer and including a solid electrolyte, a cathode active material layer disposed on the solid electrolyte layer and including a cathode active material, and a cathode current collector disposed on the cathode active material layer.

[0067] The sulfide-based solid electrolyte according to the present disclosure may be included in the solid electrolyte layer. In addition, the sulfide-based solid electrolyte may be included in the anode active material layer together with the anode active material to form a composite anode layer, or the sulfide-based solid electrolyte may be included in the cathode active material layer together with the cathode active material to form a composite cathode layer.

[0068] An anode current collector, an anode active material, a cathode active material, and a cathode current collector constituting the all-solid-state battery may be those commonly used in the related technical field.

[0069] A better understanding of the present disclosure can be obtained through the following examples and comparative examples. These examples should not be construed as limiting the scope of the present disclosure.

[0070] Test Example 1 - Possibility of Synthesizing Sulfide-Based Solid Electrolytes with Different Compositions

[0071] In order to confirm the possibility of synthesizing the sulfide-based solid electrolyte according to the present disclosure, the formation energy was calculated using density functional theory (DFT).

[0072] More specifically, 1) by replacing Li with halogen elements in the argyrodite crystal structure 5.5 PS 4.5 X 1.5 The structure of the sulfide-based solid electrolyte was designed by focusing on the 4a and 4c sites of (X = Cl, Br, I). The specific composition of the designed sulfide-based solid electrolyte is listed in Table 2 below.

[0073] 2) Use DFT to optimize the structure of the solid electrolyte to be calculated. Because the structure of the designed argyrodite can be different from the structure of the actual synthesized argyrodite, this optimization can be understood as the process of using DFT to modify the structure of the argyrodite to be close to the actual structure.

[0074] Figure 2 This is a view that explains the disorder of anions depending on the substitution of halogen doping sites. Figure 2 , Li 5.5 PS 4.5 X 1.5 The composition structures of (X = Cl, Br, I) are classified into three unique structural groups as shown in Table 1 below by anion disorder (depending on substitution of halogen element doping sites) even in the same composition, and the actually synthesized argyrodite can be in a state of mixing the three unique structural groups.

[0075] [Table 1]

[0076]

[0077] Even when sulfide-based solid electrolytes have the same composition, there may be differences in energy levels due to the disordered anions at the 4a and 4c sites, and the properties may vary based on this. Therefore, representative values ​​for specific properties of sulfide-based solid electrolytes were calculated and used.

[0078]

[0079] A representative value for a specific property, P, can be calculated by independently calculating the corresponding properties from the three structure groups (P1, P2, and P3) and then assigning contributions based on energy stability. This contribution can be considered a weighted average of the designed argyrodite crystal structure groups. This is based on the assumption that structures with lower energy have higher stability and are therefore closest to the structures actually synthesized.

[0080] All DFT calculations for this test example were performed using density functional theory implemented in the Vienna Ab Initio Simulation Package (VASP), a DFT calculation package based on a plane-wave basis set. For all structure optimizations and energy calculations, a cutoff energy of 520 eV, a 2 x 2 x 2 K-point grid, and the generalized gradient approximation (GGA)-Perdew-Burke-Ernzerhof (PBE) were used.

[0081] 3) Thereafter, the formation energy of the sulfide-based solid electrolyte having the optimized argyrodite crystal structure was calculated and compared with the formation energy of Li6PS5Cl as a reference. The results of the comparison are shown in Table 2 below.

[0082] Regarding formation energy, Gibbs free energy (G) is a function indicating the direction of a spontaneous chemical reaction and is expressed as follows.

[0083]

[0084] Since the DFT calculations in this disclosure assume a system temperature (T) of 0 K and a pressure (P) of 0, the internal energy difference (ΔE) can be used to calculate the change in Gibbs free energy. With this in mind, the specific method for calculating the formation energy of a sulfide-based solid electrolyte is as follows.

[0085]

[0086] Here, when the formation energy (ΔE f ) has a negative value, the energy of the product is more stable than the energy of the reactants, and the associated structure is therefore assumed to be thermodynamically stable. Conversely, when the formation energy has a positive value, the associated structure is assumed to be thermodynamically unstable. Because thermodynamically stable structures have a high probability of synthesis, using DFT to calculate the formation energy may ultimately be used as a criterion for determining the synthetic probability of a structure.

[0087] [Table 2]

[0088]

[0089] As shown in Table 2, the formation energy was negative in all combinations designed for doping substitution with a halogen element X at a composition ratio of 1.5. Specifically, in many reported synthesis cases, the difference from the formation energy of -1.191 eV / atom of Li6PS5Cl was within ±7%.

[0090] In this way, it was confirmed that the sulfide-based solid electrolyte with an argyrodite crystal structure designed in the present disclosure has a negative formation energy value according to DFT calculations, and its formation energy is similar to the formation energy of Li6PS5Cl, the synthesis of which has been reported. Therefore, it was demonstrated that these are thermodynamically stable materials with high practical synthesis possibility.

[0091] Test Example 2 - Lattice Constants of Sulfide-Based Solid Electrolytes with Different Compositions

[0092] In order to determine the lattice constant depending on the size of the halogen element used to dope the sulfide-based solid electrolyte having the argyrodite crystal structure and the relationship between the lattice constant and the physical properties described later, the lattice constant of the solid electrolyte optimized in Test Example 1 was calculated. The calculated results are shown in Table 3 below.

[0093] [Table 3]

[0094]

[0095] As shown in Table 3, an increase or decrease in the lattice constant depending on the type of the halogen element used to dope the solid electrolyte is clearly visible.

[0096] Specifically, in the case of substitutional doping with one type of halogen element, the lattice constant is the largest when doped with I, followed by Br and Cl.

[0097] In the case of substitutional doping with two types of halogen elements, the lattice constant increases with increasing amount of Br or I doped for each group.

[0098] Similarly, in the case of substitutional doping with three types of halogen elements, the lattice constant increases with increasing amount of doped Br or I.

[0099] For reference, the ionic radius of each element is as follows.

[0100] R Cl- = 1.87 Å, R Br- = 1.96 Å, R I- = 2.20 Å

[0101] Test Example 3 - Mechanical properties of sulfide-based solid electrolytes with different compositions

[0102] In order to determine the mechanical properties of the optimized sulfide-based solid electrolyte in Test Example 1, the bulk modulus, shear modulus, Young's modulus and Poisson's ratio of the sulfide-based solid electrolyte were calculated using DFT. The calculated results are shown in Tables 4 and Figure 4 middle.

[0103] The specific calculation method and the meanings of the symbols used in the method are as follows.

[0104] - C ij = Component of the elasticity tensor = elastic constant

[0105] -s ij = Component of the elastic compliance tensor = elastic compliance constant

[0106] -K v= Voigt bulk modulus

[0107] -K R = Reuss bulk modulus

[0108] -K VRH = Voigt-Reuss-Hill bulk modulus

[0109] -G v = Voigt shear modulus

[0110] -G R = Reuss shear modulus

[0111] -G VRH = Voigt-Reuss-Hill shear modulus

[0112] - B = bulk modulus

[0113] - G = shear modulus

[0114] - E = Young's modulus

[0115] - v = Poisson's ratio

[0116] 1) Elasticity tensor

[0117] After optimizing the calculated structure using DFT, we calculated the elasticity tensor, which has up to 21 independent components. We used the elasticity tensor and the formulas corresponding to each property to calculate the physical properties. The elasticity tensor is as follows.

[0118] = 立方 = Elastic tensor = Elastic modulus

[0119]

[0120] 2) Method for calculating bulk modulus

[0121]

[0122]

[0123]

[0124] Bulk modulus =

[0125] 3) Method for calculating shear modulus

[0126]

[0127]

[0128]

[0129] Shear modulus =

[0130] 4) Method for calculating Young's modulus

[0131]

[0132] 5) Method for calculating Poisson's ratio

[0133]

[0134] [Table 4]

[0135]

[0136] As shown in Table 4, when sulfur (S) is further substituted with halogen elements based on the reference composition of Li6PS5Cl, the bulk modulus, shear modulus, and Young's modulus all decrease. However, this decrease in mechanical properties is consistent with the Li 5.5 PS 4.5 X 1.5 The proportions of the halogen elements in (X = Cl, Br, I) are not proportional.

[0137] Meanwhile, generally, as Young's modulus decreases, ductility and fracture strength tend to increase. Figure 4 The ratio of halogen elements is increased by 0.5 compared with the reference composition of Li6PS5Cl. 5.5 PS 4.5 X 1.5 (X = Cl, Br, I), the Young's modulus decreases for all of one type of substitution, two types of substitution, and three types of substitution. However, as described above, it is difficult to confirm the trend of the change in Young's modulus depending on the halogen composition.

[0138] Specifically, it can be found that the ductility and fracture strength of the sulfide-based solid electrolyte in which the argyrodite crystal structure is replaced by doping with a halogen element increase with an increase in the amount of the halogen element, and the influence of the composition ratio is not significant.

[0139] Specifically, all of Li6PS5 (Cl, Br, I) doped with three types of halogen elements 1.5 In the 5.5 PS 4.5 Br 1.00 Cl 0.25 I 0.25It has lower modulus values ​​(bulk modulus, shear modulus, Young's modulus, Poisson's ratio) than other compositions. Therefore, it is expected that when an all-solid-state battery is manufactured using a sulfide-based solid electrolyte having the above composition ratio and high ductility and fracture strength, the crack resistance will be high.

[0140] As apparent from the above description, the sulfide-based solid electrolyte according to the present disclosure has an argyrodite crystal structure and is substitutionally doped with at least two types of halogen elements, thereby improving ductility and fracture strength. Specifically, substitutional doping with three types of halogen elements is possible.

[0141] Here, these mechanical properties can be further improved when the 4a site or 4c site of the sulfide-based solid electrolyte with an argyrodite crystal structure is substituted by three types of halogen elements.

[0142] The effects of the present disclosure are not limited to the above-mentioned effects. It should be understood that the effects of the present disclosure include all effects that can be inferred from the description of the present disclosure.

[0143] Because the embodiments of the present disclosure have been described above, it should be understood by those skilled in the art that various modifications and changes are possible by modifying, deleting or adding parts without departing from the scope and spirit of the present disclosure described in the appended claims, which will also be considered to be included in the scope of the rights of the present disclosure.

Claims

1. A sulfide-based solid electrolyte comprising an argyrodite crystal structure and having a chemical formula of Li 6-a PS 5-a X 1+a express, in, X is one or more halogen elements selected from the group consisting of Cl, Br, I and combinations thereof, Where a is 0 to 0.5, The argyrodite crystal structure is doped with the one or more halogen elements at the 4a site, the 4c ​​site, or both.

2. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula is Li 5.5 PS 4.5 X 1.5 express, in, X is one or more halogen elements selected from the group consisting of Cl, Br, I, and combinations thereof.

3. The sulfide-based solid electrolyte according to claim 1, wherein X includes at least two halogen elements selected from the group consisting of Cl, Br, and I.

4. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula Li 5.5 PS 4.5 (Br, Cl) 1.5 express.

5. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula Li 5.5 PS 4.5 (Cl, I) 1.5 express.

6. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula Li 5.5 PS 4.5 (Br, I) 1.5 express.

7. The sulfide-based solid electrolyte according to claim 1, wherein X includes all of the three halogen elements Cl, Br and I.

8. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula Li 5.5 PS 4.5 (Br, Cl, I) 1.5 express.

9. The sulfide-based solid electrolyte according to claim 1, wherein the chemical formula Li 5.5 PS 4.5 Br b Cl c I d express, in, b is 0.25 to 1.00, c is 0.25 to 1.00, and d is 0.25 to 0.50, and Where b + c + d = 1.

5.

10. The sulfide-based solid electrolyte according to claim 7, wherein the chemical formula Li 5.5 PS 4.5 Br 1.00 Cl 0.25 I 0.25 express.

11. The sulfide-based solid electrolyte according to claim 7, wherein The formation energy of the sulfide-based solid electrolyte is -1.116 eV / atom to -1.224 eV / atom.

12. The sulfide-based solid electrolyte according to claim 7, wherein The bulk modulus of the sulfide-based solid electrolyte is 24.39 GPa to 26.69 GPa.

13. The sulfide-based solid electrolyte according to claim 7, wherein The shear modulus of the sulfide-based solid electrolyte is 12.66 GPa to 13.68 GPa.

14. The sulfide-based solid electrolyte according to claim 7, wherein The Young's modulus of the sulfide-based solid electrolyte is 32.37 GPa to 34.81 GPa.

15. The sulfide-based solid electrolyte according to claim 7, wherein The sulfide-based solid electrolyte has a Poisson's ratio of 0.27 to 0.

29.

16. The sulfide-based solid electrolyte according to claim 1, wherein The electrolyte further includes an anion selected from the group consisting of F − and a combination of F − with Cl, Br, or I.

17. The sulfide-based solid electrolyte according to claim 1, wherein The electrolyte is synthesized using a ball milling process to ensure uniform distribution of the halogen elements within the argyrodite crystal structure.

18. The sulfide-based solid electrolyte according to claim 1, wherein The halogen elements are doped at the 4a site and the 4c ​​site to produce a more disordered crystal structure, thereby improving ductility and fracture strength.

19. A lithium ion battery comprising the sulfide-based solid electrolyte according to claim 1.

20. A vehicle comprising the lithium-ion battery according to claim 19.

Images