Solid electrolyte and method of manufacturing the same

Abstract

The solid electrolyte comprises a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen (X) element, and includes a crystalline phase having an agirodite-type crystal structure. The crystallite size of the crystalline phase having an agirodite-type crystal structure is 40 nm or less. In the XRD pattern, when the intensity of peak A observed in the range of 2θ = 27.0° ± 0.5° is denoted as Ia and the intensity of peak B observed in the range of 2θ = 25.5° ± 1.0° is denoted as Ib, Ia / Ib is 0.2 or less.

Description

Technology Field

[0001] The present invention relates to a solid electrolyte and a method for manufacturing the same. The present invention also relates to an electrode composite comprising a solid electrolyte, a solid electrolyte layer, and a battery. Background Technology

[0002] In recent years, solid electrolytes have attracted attention as a substitute for the electrolytes used in many liquid batteries. Solid-state batteries using solid electrolytes are expected to be commercialized as batteries that possess high safety and high energy density compared to liquid batteries using flammable organic solvents. As solid electrolytes, sulfide solid electrolytes containing, for example, lithium (Li), phosphorus (P), sulfur (S), and halogen elements have been proposed (Patent Documents 1 and 2). Prior art literature

[0003] US2020 / 091552A1WO2020 / 095937A1 The problem to be solved

[0004] In recent years, research on solid electrolytes has been actively conducted, and there is a demand for the development of solid electrolytes capable of obtaining superior battery characteristics.

[0005] Therefore, the objective of the present invention is to provide a solid electrolyte with excellent battery characteristics and a method for manufacturing the same. means of solving the problem

[0006] The present invention comprises a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen (X) element, and

[0007] It includes a crystalline phase having an agirodite-type crystal structure,

[0008] The crystallite size of the crystal phase having the above-mentioned agirodite-type crystal structure is 40 nm or less, and

[0009] In an X-ray diffraction pattern measured by an X-ray diffraction device (XRD) using CuKα1 rays, when the intensity of peak A observed in the range of 2θ = 27.0°±0.5° is set to Ia and the intensity of peak B observed in the range of 2θ = 25.5°±1.0° is set to Ib, the ratio of Ia to Ib, Ia / Ib, is 0.2 or less, and a solid electrolyte is provided.

[0010] In addition, the present invention comprises a calcination process for obtaining a calcined product by calcining a raw material composition containing a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen (X) element at 200°C or higher, and

[0011] The present invention provides a method for manufacturing a solid electrolyte having a grinding process in which a grinding energy E represented by the following formula (1) is applied to the calcined material at a rate of 200 J·sec / g or more to grind the calcined material.

[0012] E(J·sec / g)=1 / 2ntmv 2 / s (1)

[0013] In the formula, n represents the number of grinding media, t represents the grinding time (sec), m represents the mass of one grinding media (kg), v represents the speed of the grinding media (m / sec), and s represents the mass of the object to be ground (g). Brief explanation of the drawing

[0014] Figure 1 is a diagram illustrating the X-ray diffraction patterns of solid electrolytes obtained in Examples 1 to 3. Figure 2 is a diagram illustrating the X-ray diffraction patterns of solid electrolytes obtained in Comparative Examples 1 and 2. Specific details for implementing the invention

[0015] The present invention will be described below based on its preferred embodiments. First, the solid electrolyte of the present invention will be described.

[0016] The solid electrolyte of the present invention contains the element Li, the element P, the element S, and the element X.

[0017] Examples of the X element include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). The X element may be one of these elements or a combination of two or more. In the view that the agirodite-type crystal structure described later is easily formed by solid-state reaction and lithium ion conductivity is increased, it is preferable for the solid electrolyte to contain at least a Cl element or a Br element as the X element, and it is even more preferable to contain a Cl element and a Br element.

[0018] When the solid electrolyte contains Br and Cl as X elements, the ratio of Br to the sum of the moles of Br and Cl, i.e., the value of Br / (Br+Cl), is preferably, for example, 0.2 or higher, more preferably 0.3 or higher, and even more preferably 0.4 or higher. Meanwhile, the value of Br / (Br+Cl) is preferably, for example, 0.8 or lower, more preferably 0.7 or lower, and even more preferably 0.6 or lower.

[0019] In the solid electrolyte of the present invention, it is preferable to set the molar ratio of element X to element P (X / P) to a relatively high value. For example, the X / P is preferably 1.1 or higher, more preferably 1.5 or higher, and even more preferably 1.8 or higher. On the other hand, the X / P is preferably 4.0 or lower, more preferably 3.5 or lower, and even more preferably 2.4 or lower. By having the X / P within a predetermined range, the solid electrolyte of the present invention exhibits superior lithium ion conductivity. Furthermore, when the solid electrolyte of the present invention is used in a solid battery, the solid battery exhibits superior battery characteristics. The X / P can be measured, for example, by ICP emission spectroscopy.

[0020] In the solid electrolyte of the present invention, the molar ratio of S element to P element (S / P) is preferably 4.9 or less, more preferably 4.5 or less, and even more preferably 4.2 or less. Meanwhile, the S / P is preferably 3.2 or more, more preferably 3.5 or more, and even more preferably 3.8 or more. By having the S / P within a predetermined range, the solid electrolyte of the present invention exhibits superior lithium ion conductivity. Furthermore, when the solid electrolyte of the present invention is used in a solid battery, the solid battery exhibits superior battery characteristics. The S / P can be measured, for example, by ICP emission spectroscopy.

[0021] The solid electrolyte may contain elements other than Li, P, S, and X. For example, some of the Li elements may be replaced with other alkali metal elements, some of the P elements may be replaced with other nictogen elements, or some of the S elements may be replaced with other chalcogen elements.

[0022] The solid electrolyte may have a material containing other elements in addition to the elements Li, P, S, and X, provided that such elements do not impair the effects of the present invention. The content of the other material may be, for example, no more than 5 mol%, preferably less than 3 mol%, and particularly preferably less than 1 mol%.

[0023] The solid electrolyte of the present invention is preferably a crystalline compound. A crystalline compound is a material in which diffraction peaks attributable to a crystalline phase are observed when measured using an X-ray diffraction (XRD) device. It is particularly preferable for the solid electrolyte to include a crystalline phase having an agirodite-type crystal structure, as this can increase the lithium ion conductivity of the solid electrolyte.

[0024] An agirodite crystal structure is a crystal structure possessed by a group of compounds derived from a mineral represented by the chemical formula Ag8GeS6. Whether a solid electrolyte has a crystal phase of an agirodite crystal structure can be confirmed by measurements such as XRD. For example, in the diffraction pattern measured by XRD using CuKα1 rays, the crystal phase of the agirodite crystal structure exhibits characteristic diffraction peaks at 2θ = 15.3°±1.0°, 17.7°±1.0°, 25.5°±1.0°, 30.0°±1.0°, 30.9°±1.0°, and 44.3°±1.0°. In addition, depending on the elemental species constituting the solid electrolyte, in addition to the above diffraction peaks, characteristic diffraction peaks may appear at 2θ=47.2°±1.0°, 51.7°±1.0°, 58.3°±1.0°, 60.7°±1.0°, 61.5°±1.0°, 70.4°±1.0°, and 72.6°±1.0°. For the identification of diffraction peaks originating from an agarodite-type crystal structure, data from PDF No. 00-034-0688, for example, can be used.

[0025] The solid electrolyte may or may not have a crystalline phase other than an agirodite-type crystal structure. In the present invention, it is preferable to include, for example, a crystalline phase having an agirodite-type crystal structure as a main phase. Here, "main phase" refers to the phase with the largest proportion relative to the total amount of all crystalline phases constituting the solid electrolyte. Accordingly, the content ratio of the crystalline phase having an agirodite-type crystal structure is preferably, for example, 60 mass% or more relative to the total crystalline phases constituting the solid electrolyte, and more preferably 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more. Furthermore, the ratio of the crystalline phase can be confirmed, for example, by XRD. By having a crystalline phase having an agirodite-type crystal structure as the main phase, lithium ion conductivity can be effectively increased, and furthermore, the performance of a battery containing the solid electrolyte, particularly the output characteristics, can be further improved.

[0026] It is preferable that the solid electrolyte of the present invention does not have a crystalline phase of, for example, Li2S. Furthermore, if it does have a crystalline phase of Li2S, it is preferable that its presence ratio be as low as possible. When the solid electrolyte has a crystalline phase of Li2S, a diffraction peak is observed at the position 2θ = 27.0° ± 0.5° in the X-ray diffraction pattern measured by XRD using CuKα1 rays. Accordingly, in the present invention, when the intensity of diffraction peak A observed at the position 2θ = 27.0° ± 0.5° is denoted as Ia and the intensity of diffraction peak B observed in the range 2θ = 25.5° ± 1.0° is denoted as Ib, it is preferable that the ratio of Ia to Ib, Ia / Ib, is 0.20 or less, more preferable that it is 0.17 or less, even more preferable that it is 0.15 or less, and even more preferable that it is 0. Additionally, diffraction peak B is a diffraction peak originating from an agarodite-type crystal structure. Since Ia / Ib is less than or equal to the above value, the movement of lithium ions at the interface between the active material and the solid electrolyte is improved, and as a result, the input / output characteristics of the battery can be improved.

[0027] The measurement methods for Ia and Ib will be explained in detail in the embodiments described below.

[0028] In addition, in this specification, the intensity of a diffraction peak refers to the height of the peak.

[0029] It is preferable that the solid electrolyte does not have any crystal phase other than the Li2S crystal phase described above. For example, depending on the manufacturing conditions of the solid electrolyte, a diffraction peak C may be observed in the range of 2θ = 21.3° ± 0.3° in the X-ray diffraction pattern. This diffraction peak C originates from a crystal phase other than an agirodite-type crystal structure. The inventors believe that this diffraction peak C originates from the crystal phase disclosed in Patent Document 2 described in the background art section. Since the crystal phase originating from the diffraction peak C is a thermodynamically more stable phase than the agirodite-type crystal structure, it may be generated in the solid electrolyte depending on the manufacturing conditions of the solid electrolyte. In the present invention, when IC is the maximum count of diffraction peak C observed in the range of 2θ = 21.3° ± 0.3° and I0 is the intensity of the background observed in the range of 2θ = 23.5° ± 0.5°, it is preferable that the ratio IC / I0 of IC to I0 is 1.55 or less, more preferable that it is 1.40 or less, and even more preferable that it is 1.25 or less. This is because lithium ion conductivity can be improved more effectively.

[0030] In the same regard as above, when the intensity of diffraction peak C observed in the range of 2θ = 21.3° ± 0.3° is denoted as Ic, it is preferable that the count of Ic be 300 counts or less, more preferable that it be 200 counts or less, and even more preferable that it be 100 counts or less. This is because lithium ion conductivity can be improved more effectively.

[0031] The method for measuring the maximum count IC and count Ic of the diffraction peak C will be explained in detail in the embodiments described below.

[0032] As described above, the solid electrolyte has a crystalline phase having an agirodite-type crystal structure, and it is desirable for the crystalline phase to be low-crystallinity from the perspective of improving the performance of a battery containing the solid electrolyte, particularly in terms of improving output characteristics. The inventors believe that because the solid electrolyte is less crystallinity, it becomes easier to plastically deform the solid electrolyte during the fabrication of an all-solid-state battery, and consequently, the contact with the active material is improved. The crystallinity of the crystalline phase having an agirodite-type crystal structure can be evaluated by the crystallite size of the crystalline phase as a measure. For the solid electrolyte, it is preferable that the crystallite size of the crystalline phase having an agirodite-type crystal structure be, for example, 40 nm or less, more preferable that it be 35 nm or less, and even more preferable that it be 30 nm or less. In addition, the crystallite size may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more.

[0033] The method for measuring the size of the crystallizer is explained in detail in the embodiments described below.

[0034] The particle size of the solid electrolyte is the volumetric cumulative particle size D at 50% volumetric cumulative volume determined by the laser diffraction scattering particle size distribution measurement method. 50 For example, it is preferable that the size is 5㎛ or less, more preferable that it is 3㎛ or less, even more preferable that it is 1.5㎛ or less, even more preferable that it is 1.3㎛ or less, and even more preferable that it is 1.1㎛ or less. This is because the contact points and contact area between the solid electrolyte and the active material particles increase, and the input / output characteristics of the battery can be effectively improved.

[0035] Also, the particle size D of the solid electrolyte 50For example, it is preferable that the surface area be 0.1 μm or larger, more preferable that it be 0.3 μm or larger, and especially more preferable that it be 0.5 μm or larger. This is because the excessive increase in the surface area of ​​the solid electrolyte is suppressed, thereby suppressing the increase in resistance. In addition, it facilitates mixing with the active material.

[0036] Particle size D 50 The measurement method is explained in detail in the embodiments described below.

[0037] It is preferable that the solid electrolyte of the present invention has lithium ion conductivity in a solid state. For example, it is preferable that it has lithium ion conductivity of 0.1 mS / cm or more at room temperature, i.e., 25°C, of ​​which 0.2 mS / cm or more, and particularly 0.4 mS / cm or more. Lithium ion conductivity can be measured using the method described in the examples described below.

[0038] Next, a suitable method for manufacturing the solid electrolyte of the present invention will be described. The manufacturing method comprises a calcination process for calcining a raw material composition of the solid electrolyte and a grinding process for strongly grinding the calcined product obtained in the calcination process.

[0039] As a method for manufacturing a solid electrolyte, for example, as described in Patent Document 1 above, a method of manufacturing a product by mechanical milling instead of performing calcination of the raw material composition, or as described in Patent Document 2 above, a method of manufacturing a product by performing calcination of the raw material composition but not performing mechanical milling is known.

[0040] In the method described in Patent Document 1, when a solid electrolyte is produced by mechanical milling, it is believed that lithium sulfide, a component included in the raw material composition, remains in the solid electrolyte even when the milling time is extended. Lithium sulfide is a substance that reduces the movement of lithium ions between the active material and the solid electrolyte when making a solid battery, and is a factor in degrading the input / output characteristics of the battery.

[0041] On the other hand, when the method described in Patent Document 2 is adopted, the residual amount of lithium sulfide is improved, but depending on the calcination conditions, instead of an agarodite-type crystal structure, a crystalline phase that is thermodynamically more stable than the said crystal structure is formed. This abnormality is a crystalline phase corresponding to the diffraction peak C described earlier and is a factor that lowers lithium ion conductivity.

[0042] Unlike the manufacturing methods described in Patent Documents 1 and 2, the present manufacturing method employs a method that combines the calcination of a raw material composition with the strong grinding of the calcined product by mechanical milling. As a result, lithium sulfide is less likely to remain, and an agrodite-type crystal structure is more likely to be formed as a main phase. The reasons for this are thought to be as follows. For example, the crystal phase corresponding to the aforementioned diffraction peak C is a crystal phase that undergoes a phase transition to an agrodite-type crystal structure at high temperatures, but in the case of conventional calcination methods, a stable crystal phase corresponding to diffraction peak C tends to be formed. In contrast, in the present manufacturing method, by performing mechanical milling treatment after calcination, the metastable agrodite-type crystal structure can be maintained even at room temperature. That is, it is thought that the formation of the crystal phase corresponding to diffraction peak C can be suppressed.

[0043] In the present manufacturing method, as described above, a calcination process is first performed to calcine the raw material composition of the solid electrolyte. The raw material composition can be obtained by mixing a predetermined raw material. The said raw material is a material containing an element constituting the solid electrolyte, and specifically, is a compound containing the element Li, a compound containing the element S, a compound containing the element P, and a compound containing the element X.

[0044] Examples of compounds containing the element Li include lithium compounds such as lithium sulfide (Li2S), lithium oxide (Li2O), and lithium carbonate (Li2CO3), as well as lithium metal elements.

[0045] Examples of compounds containing the element S include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5). Additionally, as a compound containing the element sulfur (S), the element sulfur (S) itself may be used.

[0046] Examples of compounds containing the element P include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and phosphorus element.

[0047] Examples of compounds containing element X include one or more elements selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and one or more elements selected from the group consisting of sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), and bismuth (Bi), or compounds in which oxygen or sulfur is also bonded to said compounds. More specifically, lithium halides such as LiF, LiCl, LiBr, and LiI; phosphorus halides such as PF3, PF5, PCl3, PCl5, POCl3, PBr3, POBr3, PI3, P2Cl4, and P2I4; and SF2, SF4, SF6, and S2F 10 Examples include sulfur halides such as SCl2, S2Cl2, and S2Br2, sodium halides such as NaI, NaF, NaCl, and NaBr, and boron halides such as BCl3, BBr3, and BI3. These compounds may be used individually or in combination of two or more. Among them, it is preferable to use lithium halide (LiX (where X indicates a halogen)).

[0048] As a device for preparing a raw material composition by mixing each of the raw materials described above, for example, an attritor, a paint shaker, an oil ball mill, a ball mill, a bead mill, a homogenizer, etc., may be used. The amount of each raw material added during mixing is appropriately adjusted to satisfy the composition of the desired solid electrolyte.

[0049] The obtained raw material composition is subjected to calcination to induce a solid-state reaction, and a calcined product containing a crystalline phase having an agarodite-type crystal structure is obtained. For example, an inert gas atmosphere such as an argon atmosphere or a nitrogen atmosphere, and a hydrogen sulfide atmosphere may be used as the calcination atmosphere.

[0050] From the perspective of ensuring a solid-state reaction of the raw material composition, the calcination temperature is preferably, for example, 200°C or higher, more preferably 300°C or higher, even more preferably 350°C or higher, and even more preferably 400°C or higher. Meanwhile, considering industrial production feasibility and economic efficiency, the calcination temperature is preferably, for example, 700°C or lower, more preferably 600°C or lower, and even more preferably 550°C or lower.

[0051] The firing time is not critical and is sufficient as long as the time required to obtain a fired product of the desired composition. Specifically, it is desirable for the firing time to be sufficient for the solid-state reaction of the raw material composition to occur. The firing time may be, for example, 30 minutes or more, 2 hours or more, or 3 hours or more. On the other hand, the firing time may be, for example, 10 hours or less, or 5 hours or less.

[0052] When the desired sintered product is obtained in this way, the sintered product is subjected to a grinding process for heavy grinding. For heavy grinding, for example, an attritor, a paint shaker, a planetary ball mill, a ball mill, a bead mill, a homogenizer, etc., can be used. In order to perform heavy grinding using these devices, it is advantageous to apply high energy by strongly stirring the sintered product. The energy applied to the sintered product is defined as the grinding energy E represented by the following equation (1).

[0053] E(J·sec / g)=1 / 2ntmv 2 / s (1)

[0054] In the formula, n represents the number of grinding media, t represents the grinding time (sec), m represents the mass of one grinding media (kg), v represents the speed of the grinding media (m / sec), and s represents the mass of the object to be ground (g).

[0055] The speed v of the grinding media can be calculated from Equation (2) in the case of a planetary ball mill, for example.

[0056] v(m / sec)=dπRα / 60 (2)

[0057] In the formula, d represents the diameter of the port container (m), R represents the rotational speed (rpm), and α represents the magnetic field ratio.

[0058] In addition, in a grinder equipped with a stirring mechanism such as a bead mill, the speed of the grinding media corresponds to the peripheral speed v (m / sec) of the stirring mechanism (disk, etc.).

[0059] In the grinding process, it is preferable to apply a grinding energy E, defined in the above formula, of 200 J·sec / g or more to the sintered material. Grinding with such high energy is referred to as "strong grinding" in this specification. By applying such high energy to the sintered material, there is an advantage in obtaining a solid electrolyte containing a crystalline phase having an agirodite-type crystal structure that is free of defects or has a very low proportion of defects. In order to make this advantage even more pronounced, the grinding energy E applied to the sintered work is more preferably 200 J·sec / g or more and 200,000 J·sec / g or less, more preferably 500 J·sec / g or more and 100,000 J·sec / g or less, more even more preferably 2000 J·sec / g or more and 100,000 J·sec / g or less, particularly more preferably 7000 J·sec / g or more and 50,000 J·sec / g or less, and most preferably 7000 J·sec / g or more and 20,000 J·sec / g or less.

[0060] As an example of a grinding condition for imparting grinding energy E of the above-described range to a sintered product, the following conditions may be cited.

[0061] · Device: Planetary ball mill

[0062] · Rotation speed: 100 rpm or more and 1,000 rpm or less

[0063] · Material of grinding media: Zirconia or alumina

[0064] · Diameter of crushed media: 2mm or more and 30mm or less

[0065] · Grinding time: 0.5 hours or more, 100 hours or less

[0066] The kinetic energy W(J) of one crushed media is

[0067] W=1 / 2mv 2 (3)

[0068] It can be expressed as follows. The definitions of m and v are as described above. These figures indicate that the collision energy of one grinding media is large. From the perspective of promoting mechanochemical reactions, it is preferable that the grinding process includes a process in which the kinetic energy W defined in the above-mentioned equation (3) is 0.0001J or more. It is more preferable that the kinetic energy W is 0.001J or more and 1.0J or less, even more preferable that it is 0.005J or more and 0.1J or less, and even more preferable that it is 0.01J or more and 0.05J or less.

[0069] After performing heavy grinding of the sintered product in this manner, a known grinding treatment can be performed with lower energy than that of heavy grinding for purposes such as adjusting the particle size.

[0070] The grinding treatment is the particle size D of the solid electrolyte of the present invention. 50For example, it is preferable to make the area 5㎛ or less, more preferable to make it 3㎛ or less, even more preferable to make it 1.5㎛ or less, even more preferable to make it 1.3㎛ or less, and even more preferable to make it 1.1㎛ or less. This is because the contact area between the solid electrolyte and the active material increases, and the output characteristics of the battery are improved.

[0071] In the manufacturing method of this invention, it is also preferable that the total grinding energy of the aforementioned steel grinding and the known grinding treatment (a grinding treatment with lower energy than steel grinding) be within the aforementioned range. This is because by applying such grinding energy, it is easier to obtain a solid electrolyte containing a crystalline phase having an agirodite-type crystal structure in which no abnormalities exist or the proportion of abnormalities is very low.

[0072] The solid electrolyte of the present invention obtained by the above method has a slightly dark color, unlike, for example, the solid electrolyte described in Patent Document 1. The solid electrolyte described in Patent Document 1 has a white color, unlike the solid electrolyte of the present invention. The inventors believe that this difference is due to a difference in the manufacturing method. Specifically, the solid electrolyte of the present invention is obtained by undergoing a calcination process as described above, and it is believed that the solid electrolyte has a slightly dark color due to undergoing the calcination process. In contrast, the solid electrolyte described in Patent Document 1 is believed to have a white color because it is obtained without undergoing a calcination process.

[0073] The color exhibited by the solid electrolyte of the present invention is L ＊ a ＊ b ＊ Lightness L in the color system ＊It is expressed as a value, preferably 90 or less, more preferably 50 or more and 90 or less, even more preferably 60 or more and 85 or less, and even more preferably 75 or more and 82 or less.

[0074] Brightness L ＊ The method for measuring the value is explained in detail in the embodiments described below.

[0075] The solid electrolyte obtained by the above method can be used as a material constituting a solid electrolyte layer, a positive electrode layer, or a negative electrode layer. Specifically, the solid electrolyte of the present invention can be used in a battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. That is, the solid electrolyte can be used in so-called solid batteries. More specifically, it can be used in lithium solid batteries. The lithium solid battery may be a primary battery or a secondary battery. There are no particular restrictions on the shape of the battery, and shapes such as laminate, cylindrical, and prismatic types may be adopted. The term "solid battery" includes not only solid batteries that do not contain any liquid or gel-like substances as an electrolyte, but also embodiments that contain, for example, 50 mass% or less, 30 mass% or less, or 10 mass% or less of a liquid or gel-like substance as an electrolyte.

[0076] When the solid electrolyte layer of the present invention is included, the solid electrolyte layer may be manufactured by, for example, by dropping a slurry consisting of a solid electrolyte, a binder, and a solvent onto a gaseous phase and cutting it by rubbing with a doctor blade, etc., by cutting it with an air knife after contacting the gaseous phase with the slurry, or by forming a film using a screen printing method, etc., and then removing the solvent by heat drying. Alternatively, the solid electrolyte in powder form may be manufactured by compacting it into a powder body using a press, etc., and then processing it appropriately.

[0077] The thickness of the solid electrolyte layer is typically preferably 5㎛ or more and 300㎛ or less, from the balance of short-circuit prevention and volumetric capacity density, and among them, it is more preferably 10㎛ or more and 100㎛ or less.

[0078] The solid electrolyte of the present invention is used together with an active material to form an electrode composite. The proportion of the solid electrolyte in the electrode composite is typically 10 mass% or more and 50 mass% or less. The electrode composite may include other materials such as a conductivity aid or a binder as needed. An electrode layer, such as a positive electrode layer and / or a negative electrode layer, can be produced by mixing the electrode composite with a solvent to produce a paste, applying it onto a current collector such as an aluminum foil, and drying it.

[0079] As the positive electrode material constituting the positive electrode layer, a positive electrode material currently used as a positive electrode active material for lithium-ion batteries can be appropriately used. Examples include positive electrode active materials containing lithium, specifically spinel-type lithium transition metal oxides and lithium metal oxides having a layered structure. By using a high-voltage positive electrode material as the positive electrode material, an improvement in energy density can be achieved. In addition to the positive electrode active material, the positive electrode material may include a conductive material or other materials.

[0080] As the negative electrode material constituting the negative electrode layer, a negative electrode material used as a negative electrode active material for lithium-ion batteries can be appropriately used. The solid electrolyte of the present invention is electrochemically stable and has a low potential comparable to lithium metal or lithium metal (approx. 0.1V vs. Li +Carbon-based materials such as graphite, artificial graphite, natural graphite, and hard carbon, which are materials that are charged and discharged with (Li), can be used as negative electrode materials. This can significantly improve the energy density of the solid-state battery. In addition, silicon or tin, which are promising materials for high capacity, can be used as active materials. In batteries using a conventional electrolyte, the deterioration of battery characteristics is significant due to the reaction between the electrolyte and the active material during charging and discharging, and the occurrence of corrosion on the surface of the active material. In contrast to this, if the solid electrolyte of the present invention is used instead of the electrolyte and silicon or tin is used as the negative electrode active material, the aforementioned corrosion reaction does not occur, thereby improving the durability of the battery. Regarding the negative electrode material, a conductive material may be included in addition to the negative electrode active material, or other materials may be included.

[0081] Examples

[0082] The present invention will be explained in more detail below by way of examples. However, the scope of the present invention is not limited to these examples.

[0083] [Example 1]

[0084] (1) Preparation of raw material composition

[0085] To obtain the composition Li5PS4ClBr, lithium sulfide (Li2S) powder, phosphorus pentasulfide (P2S5) powder, lithium chloride (LiCl) powder, and lithium bromide (LiBr) powder were each weighed to a total weight of 5g. 10mL of heptane was added to these powders to prepare a slurry. This slurry was placed in a zirconia container with a volume of 80mL and set in a planetary ball mill (Fritsch P-5). 90g of ZrO2 balls with a diameter of 5mm were used as the grinding media. The ball mill was operated at 100rpm and ground for 10 hours. The solvent was removed by vacuum drying the obtained slurry at room temperature, thereby obtaining the raw material composition.

[0086] (2) Sintering

[0087] A calcined product was obtained by calcining the raw material composition. Calcination was carried out using a tubular electric furnace. During calcination, 100% pure nitrogen gas was circulated inside the electric furnace. The calcination temperature was set to 600°C and calcination was carried out over 4 hours.

[0088] (3) Strong crushing

[0089] The calcined material was subjected to heavy grinding using a planetary ball mill (Fritsch P-5). The calcined material was weighed to a total weight of 5 g. 10 mL of heptane was added to this powder to prepare a slurry. This slurry was placed in a zirconia container with a volume of 80 mL. 90 g of ZrO2 balls with a diameter of 10 mm were used as the grinding media. The ball mill was operated at 370 rpm, and the grinding time was set to 2 hours. Heavy grinding was performed on the powder particle size D 50 This was carried out until the result was about 10㎛. The solvent was removed by vacuum drying the obtained slurry at room temperature.

[0090] (4) Fine grinding

[0091] The powder obtained by heavy grinding was finely ground using a planetary ball mill. The powder was weighed to a total weight of 2 g. A slurry was prepared by adding 10 mL of toluene and a dispersant to this powder. This slurry was placed in a zirconia container with a volume of 80 mL. 90 g of ZrO2 balls with a diameter of 0.8 mm were used as the grinding media. The ball mill was operated at 100 rpm, and grinding was carried out over 3 hours. The solvent was removed by vacuum drying the obtained slurry at 150°C. In this way, the desired solid electrolyte powder was obtained. The X / P molar ratio measured by ICP emission spectroscopy was 2, and the S / P molar ratio was 4.

[0092] The grinding energy E [J·sec / g] in this embodiment was calculated as follows.

[0093] First, the grinding energy for heavy grinding and fine grinding was calculated, respectively.

[0094] (Strong crushing)

[0095] The density of the ZrO2 grinding media used in this embodiment is 6.0 g / cm². The number of grinding media n and the mass (kg) of one grinding media were calculated based on an input mass of 90 g, assuming that the grinding media is spherical. As a result, the number of balls n was 28.6. The mass of one grinding media was 0.00314 kg.

[0096] The speed (m / sec) of the grinding media when the planetary ball mill device is operated at 370 rpm was calculated from the above-described equation (2). Since the magnetic field ratio α of the planetary ball mill device used for grinding is 2.19 and the inner diameter of the mill pot used for grinding is 0.065 m, the ball speed was calculated to be 2.76 (m / sec). Based on this value, the grinding energy E was calculated from the above-described equation (1) and was 493 J·sec / g.

[0097] (Fine grind)

[0098] The grinding energy during fine grinding was calculated in the same way as in the case of steel grinding, and it was 135 J·sec / g.

[0099] Therefore, by adding the grinding energy from the steel grinding process and the fine grinding process, a grinding energy E of 628 J·sec / g, as described in Table 1 below, was obtained.

[0100] [Examples 2 and 3]

[0101] In the steel grinding process of Example 1, the grinding times were set to 10 hours and 50 hours, respectively. Except for this, the process was carried out in the same manner as in Example 1 to obtain a solid electrolyte powder.

[0102] [Comparative Example 1]

[0103] This comparative example corresponds to the embodiment of Patent Document 2.

[0104] (1) Preparation of raw material composition

[0105] It was performed in the same manner as Example 1.

[0106] (2) Sintering

[0107] A calcined product was obtained by calcining the raw material composition. Calcination was carried out using a tubular electric furnace. During calcination, 100% pure nitrogen gas was circulated inside the electric furnace. The calcination temperature was set to 600°C and calcination was carried out over 4 hours.

[0108] (3) We crushed the medicine

[0109] The calcined material was lightly ground using a planetary ball mill. The calcined material was weighed to a total weight of 5 g. A slurry was prepared by adding 10 mL of toluene and a dispersant to this powder. This slurry was placed in a zirconia container with a volume of 80 mL. 90 g of ZrO2 balls with a diameter of 5 mm were used as the grinding media. The ball mill was operated at 100 rpm, and light grinding was performed over 3 hours. The obtained slurry was vacuum dried at room temperature, and the solvent was removed.

[0110] (4) Fine grinding

[0111] It was performed in the same manner as Example 1.

[0112] [Comparative Example 2]

[0113] This comparative example corresponds to the embodiment of Patent Document 1.

[0114] (1) Preparation of raw material composition

[0115] It was performed in the same manner as Example 1.

[0116] (2) Mechanical Milling

[0117] The raw material composition was subjected to mechanical milling using a planetary ball mill device. Each raw material composition was weighed to a total weight of 5g. 10g of heptane was added to these powders to prepare a slurry. This slurry was placed in a zirconia container with a volume of 80mL. 90g of ZrO2 balls with a diameter of 10mm were used as the grinding media. The operating conditions of the ball mill device were set to 370rpm, and the grinding time was set to 50 hours. The obtained slurry was vacuum dried at room temperature, and the solvent was removed.

[0118] (3) Fine grinding

[0119] It was performed in the same manner as Example 1.

[0120] [Evaluation 1]

[0121] XRD measurements were performed on the solid electrolytes obtained in the examples and comparative examples, and the values ​​of Ia / Ib were calculated. The results are shown in Table 1. Additionally, XRD patterns are illustrated in Figures 1 and 2. Examples 1, 2, and 3 and Comparative Examples 1 and 2 are graphs offset by +3000, +6000, +9000, +12000, and +18000 counts, respectively, from the measured values.

[0122] The method for calculating Ia / Ib is as follows.

[0123] The average value of the peak intensity counts at 2θ = 23.5° ± 0.5° was set as background I0. In addition, the maximum number of peak intensity counts in the range of 2θ = 25.5° ± 1.0° was set as IB. The value obtained by subtracting background I0 from IB was set as the peak intensity Ib attributable to the agarodite crystal structure.

[0124] In addition, the maximum count of peak intensity in the range of 27.0°±0.5° was set as IA. The value obtained by subtracting the background I0 from IA was set as the peak intensity Ia attributable to the Li2S crystal structure.

[0125] In this XRD measurement, the background I0 value was measured to be between 400 and 800 counts. In addition, the maximum peak intensity in this XRD measurement was measured to be 1500 counts or more.

[0126] The maximum count IC of the diffraction peak C was set to the maximum count in the range of 2θ=21.3°±0.3°.

[0127] The count number Ic of the diffraction peak C was set as the value obtained by subtracting the background I0 from the maximum count number IC.

[0128] In addition, the obtained X-ray diffraction patterns were imported into Smart Lab Studio II, and the crystallite size of the crystalline phase having an agarodite-type crystal structure was calculated for the sulfide solid electrolytes obtained in the examples and comparative examples using the WPPF method. Device-derived parameters were corrected using standard samples. The results are shown in Table 1. Si from NIST SRM 640f was used as the standard sample for angle correction. LaB6 from NIST SRM 660c was used as the standard sample for width correction. A hermetic holder for ASC manufactured by Rigaku Co., Ltd. (A00012149) was used for the air-exposure cell. The hermetic cover was a transparent hermetic film, and the atmosphere was set to Ar.

[0129] XRD measurements were performed using the X-ray diffractometer “Smart Lab SE” manufactured by Rigaku Co., Ltd. The measurement conditions were set as follows: no exposure to air, scanning axis: 2θ / θ, scanning range: 10° or more and 120° or less, step width: 0.02°, and scanning speed: 1° / min.

[0130] The X-ray source was set to CuKα1. The tube voltage was set to 40 kV and the tube current to 80 mA. By measuring under these conditions, the background I0 count was in the range of 400 to 800, and the maximum peak intensity was 1500 counts or more.

[0131] [Evaluation 2]

[0132] For the solid electrolytes obtained in the examples and comparative examples, the particle size D50 was measured by the following method. The results are shown in Table 1 below.

[0133] Using an automatic sample feeder for a laser diffraction particle size distribution measuring device ("Microtorac SDC" manufactured by Nikkiso Co., Ltd.), the flow rate of the measurement sample containing solid electrolyte was set to 50%, and 30W ultrasound was irradiated onto the measurement sample containing solid electrolyte for 60 seconds. Subsequently, the particle size distribution was measured using the laser diffraction particle size distribution measuring instrument "MT3000II" manufactured by Nikkiso Co., Ltd., and from the obtained volume-based particle size distribution chart, the particle sizes at which the cumulative volume reached 10 vol%, 50 vol%, and 95 vol% were determined, respectively, D 10 , D 50 and D 95 ...did so. Also, D 10 , D 50 and D 95 During the measurement, the organic solvent was passed through a 60 µm filter. Additionally, the solvent refractive index was set to 1.50, the particle permeability condition to "transmissive," the particle refractive index to 1.59, and the shape to "non-spherical." The measurement range was set to 0.133 µm to 704.0 µm, and the measurement time to 10 seconds. The measurement was performed twice, and the arithmetic mean of the obtained measurements was D 10 , D 50 and D 95 ...did so.

[0134] [Evaluation 3]

[0135] For the solid electrolytes obtained in the examples and comparative examples, the lightness L is determined by the following method. ＊ ...was measured. The results are shown in Table 1 below.

[0136] Solid electrolyte powder was filled into a glass holder used for XRD measurements, and measurements were taken using a spectrophotometer (Konica Minolta, CM-2600d). A CIE standard light source D65 was used as the light source.

[0137] [Evaluation 4]

[0138] Solid-state batteries were fabricated using the solid electrolytes obtained in the examples and comparative examples, and rate characteristics were measured for the solid-state batteries using the following method. The results are shown in Table 1 below.

[0139] (ingredient)

[0140] As a positive electrode active material, LiNi, a layered compound 0.6 Co 0.2 Mn 0.2 O2(NCM) powder with a coating layer composed of Li-Nb-O was used. Graphite was used as the negative electrode active material. As the solid electrolyte used in the positive electrode layer, the solid electrolyte obtained in the examples or comparative examples was used. A general agirodite-type sulfide solid electrolyte was used for the separator layer and the negative electrode layer.

[0141] (Preparation of positive and negative combinations)

[0142] The positive electrode mixture was prepared by mortar-and-mortar mixing the positive electrode active material, solid electrolyte, and conductive aid (acetylene black) powder in a mass ratio of 60:37:3.

[0143] The negative electrode mixture was prepared by mortar-and-mortar mixing graphite and a solid electrolyte in a mass ratio of 64:36.

[0144] (Fabrication of solid-state battery cells)

[0145] 0.05g of solid electrolyte was injected into a ceramic cylinder (opening diameter 10.5mm, height 18mm) with open upper and lower ends, while the lower opening was sealed with a SUS electrode. An electrode was mounted on the upper opening and uniaxial press molded at approximately 0.8 tf / cm² to produce an electrolyte layer. The upper electrode was removed, a positive electrode composite was injected onto the electrolyte layer, and after smoothing the positive electrode composite, the upper electrode was remounted. Subsequently, the lower electrode was removed, and a negative electrode composite was injected onto the electrolyte layer. The lower electrode was remounted and uniaxial press molded at approximately 4.6 tf / cm². Afterward, the upper and lower electrodes were clamped together and constrained with a torque of 4 N·m to produce an all-solid-state battery equivalent to 1 mAh. The fabrication process of the all-solid-state battery was carried out in a glove box replaced with dry air having an average dew point of -70°C.

[0146] The all-solid-state battery obtained in this way was loaded into an environment tester maintained at 25°C and connected to a charge / discharge measuring device to evaluate the battery characteristics.

[0147] The battery was charged and discharged using 1mA as 1C. The battery was charged from 0.2C to 4.5V using the CC-CV method, and the first charge capacity was obtained. The battery was discharged from 0.2C to 2.5V using the CC method, and the first discharge capacity was obtained.

[0148] Next, after charging from 0.2C to 4.5V using the CC-CV method, discharging from 5C to 2.5V using the CC method was performed, and the discharge capacity at 5C was obtained. The ratio of the discharge capacity at 5C to the discharge capacity at 0.2C, set to 100%, was calculated, and the rate characteristic (5C / 0.2C[%]) was obtained.

[0149]

[0150] As is evident from the results shown in Table 1, the solid-state battery obtained using the solid electrolyte obtained in each example has higher rate characteristics than the comparative example.

[0151] In addition, as is evident from the XRD patterns shown in Figures 1 and 2, no diffraction peaks of lithium sulfide were observed in the solid electrolyte obtained in the example. Industrial applicability

[0152] As described above in detail, excellent battery characteristics can be obtained according to the solid electrolyte of the present invention. Furthermore, such a solid electrolyte can be easily manufactured according to the manufacturing method of the present invention.

Claims

Claim 1 A solid electrolyte comprising a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen (X) element, and a crystal phase having an agirodite-type crystal structure, wherein the crystallite size of the crystal phase having the agirodite-type crystal structure is 40 nm or less, and in an X-ray diffraction pattern measured by an X-ray diffraction device (XRD) using CuKα1 rays, when the intensity of peak A observed in the range 2θ = 27.0° ± 0.5° is Ia and the intensity of peak B observed in the range 2θ = 25.5° ± 1.0° is Ib, the ratio of Ia to Ib, Ia / Ib, is 0.2 or less. Claim 2 A solid electrolyte according to claim 1, wherein, in the X-ray diffraction pattern, IC is the maximum count of peak C observed in the range of 2θ = 21.3° ± 0.3° and I0 is the intensity of the background observed in the range of 2θ = 23.5° ± 0.5°, and the ratio IC / I0 of IC to I0 is 1.55 or less. Claim 3 In paragraph 1 or 2, L ＊ a ＊ b ＊ Lightness L in the color system ＊ A solid electrolyte with a value of 90 or less. Claim 4 In claim 1 or 2, the volume cumulative particle size D at 50% volume cumulative volume by the laser diffraction scattering particle size distribution measurement method 50 A solid electrolyte with a size of 5㎛ or less. Claim 5 A solid electrolyte according to claim 1 or 2, wherein the molar ratio of the halogen (X) element to the phosphorus (P) element is 1.1 or higher, and the molar ratio of the sulfur (S) element to the phosphorus (P) element is 4.9 or lower. Claim 6 A solid electrolyte according to claim 1 or 2, wherein the halogen (X) element is a chlorine (Cl) element and a bromine (Br) element. Claim 7 A method for manufacturing a solid electrolyte comprising: a calcination process for obtaining a calcined product by calcining a raw material composition containing lithium (Li) element, phosphorus (P) element, sulfur (S) element and halogen (X) element at 200°C or higher; and a grinding process for grinding the calcined product by applying a grinding energy E represented by the following formula (1) at a rate of 200 J·sec / g or higher to the calcined product. E(J·sec / g)=1 / 2ntmv 2 / s (1) In the equation, n represents the number of grinding media, t represents the grinding time (sec), m represents the mass of one grinding media (kg), v represents the speed of the grinding media (m / sec), and s represents the mass of the object to be ground (g). Claim 8 In claim 7, the volumetric cumulative particle size D at 50% volumetric cumulative volume by the laser diffraction scattering particle size distribution measurement method 50 A manufacturing method of grinding until it becomes 5㎛ or less. Claim 9 An electrode composite comprising a solid electrolyte and an active material as described in claim 1 or 2. Claim 10 A solid electrolyte layer containing the solid electrolyte described in paragraph 1 or 2. Claim 11 A battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, and containing the solid electrolyte described in claim 1 or 2.

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