Battery member and method for manufacturing battery member

Abstract

This battery member is a sheet-shaped member containing a sulfide solid electrolyte and a binder, and has one peak at 17.8±0.7° in XRD measurement.

Description

Battery component and method for manufacturing the battery component

[0001] This invention relates to a battery component and a method for manufacturing a battery component. Specifically, this invention relates to a battery component that has excellent ion conductivity and is suitable for mass production on an industrial scale, and a method for manufacturing a battery component.

[0002] With the recent advancements in mobile communications and information and electronic devices, the demand for high-capacity and lightweight lithium-ion secondary batteries is on the rise. Most electrolytes that exhibit high lithium-ion conductivity at room temperature are liquids, and most commercially available lithium-ion secondary batteries use organic electrolytes. However, lithium-ion secondary batteries using these organic electrolytes pose risks of leakage, ignition, or explosion, and there is a demand for safer batteries.

[0003] To address the above problems, all-solid-state lithium-ion batteries using safer solid electrolytes are expected to be the next generation of lithium-ion batteries. Sulfide solid electrolytes are attracting attention as solid electrolytes due to their excellent ion conductivity and battery processing properties.

[0004] The main component of sulfide-based solid electrolytes is Li ３ PS ４ However, this material alone lacks some ionic conductivity. On the other hand, Li ３ PS ４ Even so, techniques have been developed to improve ionic conductivity by effectively controlling crystallinity. For example, amorphous Li ３ PS ４ A technique has been proposed to improve conductivity by an order of magnitude by rapidly heating a powder to its crystallization temperature and holding it at that temperature for several seconds to several minutes (Patent Document 1). It has been revealed that the reason for this improvement in conductivity is that a different type of crystal, namely "α-crystal," precipitates compared to normal heating (Non-Patent Documents 1, 2).

[0005] Japanese Patent Publication No. 2013-118092

[0006] Hiroyuki Higuchi, Cutting-Edge Battery Technology - 2019, pp. 34-45. T. Kimura, et al., J. Am. Chem. Soc., 145, 26 (2023) 14466-14474.

[0007] In the above-mentioned document, rapid heating is achieved by quickly introducing Li ３ PS ４ powder between metal plates that have been pre-heated to a high temperature. However, with this method, mass production of Li ３ PS ４ -α crystals is difficult. For mass production, while it is necessary to increase the amount of Li ３ PS ４ powder introduced between the metal plates as much as possible, for the Li ３ PS ４ powder located away from the metal plates, it is impossible to supply thermal energy at the desired heating rate due to heat transfer problems. As a result, only low-conductivity crystals called "β crystals" instead of "α crystals" were obtained.

[0008] On the other hand, a technique of heating from inside a substance using microwaves is known. In theory, rapid heating is possible with this technique, but it was difficult to achieve uniform rapid heating on an industrial scale.

[0009] One object of the present invention is to provide a battery member having excellent ionic conductivity and suitable for mass production on an industrial scale, and a method for manufacturing the battery member.

[0010] As a result of intensive studies, the present inventors have found that a battery member having a specific configuration has excellent ionic conductivity and is also suitable for mass production on an industrial scale, and have completed the present invention. According to the present invention, the following battery members and the like can be provided. 1. A sheet-like member containing a sulfide solid electrolyte and a binder, and having one peak at 17.8 ± 0.7° in XRD measurement, the battery member. 2. The battery member according to 1, further having a peak at 19.1 ± 0.5° in XRD measurement. 3. The sulfide solid electrolyte is Li ３ PS ４A battery component according to 1 or 2. 4. A battery component according to any one of 1 to 3, wherein the binder comprises one or more selected from the group consisting of: styrene-butadiene-styrene block copolymer (SBS); polyvinylidene fluoride (PVDF); polytetrafluoroethylene (PTFE); ethylene propylene diene rubber (EPDM); cellulose resin; polyacrylic acid; and compounds having phosphorus and sulfur atoms as constituent atoms and having disulfide bonds. 5. A battery component according to any one of 1 to 4, comprising 0.1 to 20% by mass of the binder. 6. A battery component according to any one of 1 to 5, further comprising an electrode active material. 7. A battery component according to any one of 1 to 6, formed on a metal sheet or a plastic sheet. 8. A method for manufacturing a battery component, comprising: forming a sheet containing a sulfide solid electrolyte and a binder; supplying the sheet to a heat treatment apparatus; and heat-treating the sheet at a temperature of 150°C or higher using the heat treatment apparatus. 9. The method for manufacturing a battery component according to 8, wherein the heat treatment apparatus is configured to bring a heating member, preheated to 150°C or higher, into contact with the sheet. 10. The method for manufacturing a battery component according to 9, wherein the heat treatment apparatus is configured to sandwich the sheet between a pair of heating members, preheated to 150°C or higher. 11. The method for manufacturing a battery component according to 9 or 10, wherein the heating member is plate-shaped. 12. The method for manufacturing a battery component according to 9 or 10, wherein the heating member is roll-shaped. 13. The method for manufacturing a battery component according to 9 to 12, wherein the heating rate, treatment temperature, treatment time, and cooling rate in the heat treatment are set so that the XRD measurement of the obtained battery component has one peak at 17.8 ± 0.7°.

[0011] According to the present invention, it is possible to provide a battery component and a method for manufacturing a battery component that have excellent ion conductivity and are suitable for mass production on an industrial scale.

[0012] This figure shows the XRD measurement results for Manufacturing Example 1 and Comparative Examples 1-5. This figure shows the XRD measurement results for Comparative Example 6 and Examples 1-6. This figure shows the XRD measurement results for Comparative Examples 7 and 8 and Examples 7-12. This figure shows the XRD measurement results for Examples 13-18 (particularly the effect of heat treatment time).

[0013] The battery component and the method for manufacturing the battery component of the present invention will be described in detail below. In this specification, "x to y" represents a numerical range of "x or more, and y or less". The upper and lower limits described for the numerical range can be combined arbitrarily. Furthermore, it is possible to combine two or more non-conflicting embodiments of the embodiments of the present invention described below, and an embodiment that combines two or more embodiments is also an embodiment of the embodiments of the present invention.

[0014] 1. Battery Component A battery component according to one aspect of the present invention is a sheet-like component comprising a sulfide solid electrolyte and a binder, and has one peak at 17.8 ± 0.7° in XRD measurement.

[0015] The battery component according to this embodiment exhibits excellent ion conductivity and is suitable for mass production on an industrial scale. When the battery component has one peak at 17.8 ± 0.7° in XRD measurement, it can be determined that the sulfide solid electrolyte contained in this battery component has an α-crystal structure. The battery component according to this embodiment can exhibit excellent ion conductivity due to this α-crystallized sulfide solid electrolyte. On the other hand, there is no technology for mass-producing α-crystal powder of sulfide solid electrolyte, but many technologies for mass-producing sulfide solid electrolyte glass powder have been established. When incorporating this glass powder into a battery component, it is common to process the composition containing it into a sheet. If this sheet is rapidly heated, α-crystals will precipitate. Thus, by following the process of rapidly heating after forming the sulfide solid electrolyte glass into a sheet, it is possible to mass-produce α-crystals of sulfide solid electrolyte. In addition, this technology can reduce the quality variations that are a concern during mass production. For example, consider the case of rapidly heating solid electrolyte powder sandwiched between metal plates. In addition to the solid electrolyte powder, numerous voids exist between the metal plates. Because the distribution of these voids varies, heat transfer to the solid electrolyte powder also varies, leading to uneven crystal growth and, consequently, uneven conductivity. On the other hand, a sheet is a homogeneous molded body with very few voids. Therefore, there is very little unevenness in heat transfer during rapid heating, and a component with the same conductivity can be obtained no matter where you look on the sheet. Conversely, in the case of rapid heating of solid electrolyte powder, if you try to sufficiently precipitate α crystals, areas with relatively good heat transfer will undergo a crystal transition to β crystals. As a result, the rapid heating conditions (temperature, time, etc.) for precipitation of only α crystals become narrow. In a sheet, the heat transfer is uniform across the entire surface, making it possible to sufficiently precipitate only α crystals, thus widening the range of heating conditions for α crystal precipitation. In this sense as well, the battery component of this embodiment is suitable for mass production on an industrial scale.

[0016] Furthermore, "having one peak at 17.8 ± 0.7° in XRD measurements" means that in XRD measurements (measurements by X-ray diffraction), there is only one peak within the diffraction angle range of 2θ = 17.8 ± 0.7°. Here, even if a peak is observed in this range due to the influence of noise, it will not be judged as a peak. Also, even if multiple peaks are observed after ignoring the influence of noise, if the diffraction angles of the peak tops are not separated by more than 0.25°, these will be judged as a single peak.

[0017] Furthermore, as mentioned above, if "the XRD measurement shows one peak at 17.8 ± 0.7°", it is determined that the sulfide solid electrolyte contained in this battery component has an α-crystal crystal structure. Depending on the elemental composition of the sulfide solid electrolyte, in addition to the above diffraction peak (the peak at 17.8 ± 0.7°), there may also be a peak in the diffraction angle range of 19.1 ± 0.5°. In such cases as well, it is determined that the sulfide solid electrolyte contained in this battery component has an α-crystal crystal structure. Note that the XRD measurement is performed by the method described in the examples.

[0018] "Battery components" refer to components that make up a battery, such as separators and electrodes. The electrodes may be either positive or negative electrodes. The battery itself is not particularly limited, but examples include lithium-ion batteries. A lithium-ion battery may be, for example, an all-solid-state lithium-ion battery.

[0019] (Sulfide Solid Electrolytes) The sulfide solid electrolyte is not particularly limited as long as it can form an α-crystal upon heating. Examples of sulfide solid electrolytes include those with an argyrodite crystal structure, Li ３ PS ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P ３ S １１ Crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４Thio-Lisicon Region II type crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples include sulfide solid electrolytes having a crystalline structure similar to that of the thio-LISICON Region II system. Among these, Li ３ PS ４ A sulfide solid electrolyte having a crystalline structure is preferred. Li ３ PS ４ As a sulfide solid electrolyte having a crystalline structure, Li ３ PS ４ For example, Li ３ PS ４ Sulfide solid electrolytes containing halogen atoms, oxygen atoms, etc., based on the above are also examples. Specifically, sulfide solid electrolytes that satisfy the conditions of composition 1 or composition 2 below are examples. <Composition 1> (1-a)Li ３ PS ４ +aLiX Here, X is a halogen atom, and 0 < a < 0.15. <Composition 2> (1-a)Li ３ PS ４－ｙ O ｙ +aLiX Here, X is a halogen atom, 0 < a < 0.5, and 0 < y < 1. In composition 1 and composition 2, the halogen atom of X may be a single halogen atom or two or more halogen atoms may be used in combination. The halogen atom of X may be one or more selected from the group consisting of, for example, iodine, bromine, chlorine, etc. In one embodiment, the sulfide solid electrolyte is Li ３ PS ４ In this case, additives such as LiX mentioned above, which enhance ionic conductivity, become unnecessary, thus eliminating the cost of such additives and the energy required to incorporate them into the solid electrolyte. Furthermore, even in this case, excellent ionic conductivity is exhibited due to the presence of α-crystals.

[0020] The method for producing sulfide solid electrolytes is not particularly limited. For example, they can be produced by mechanical milling methods using ball mills, bead mills, kneaders, powder compounding machines, etc., calcination methods in which mixed raw material powders are heated and reacted, and melt-quenching methods in which the raw materials are reacted in a molten state and then rapidly cooled. ３ PS ４ For example, Li ２ S and P ２ S ５ It can be manufactured by processing with a ball mill. The sulfide solid electrolyte according to composition 1 described above is, for example, Li ３ PS ４ It can be manufactured by processing LiX in a ball mill. The sulfide solid electrolyte according to composition 2 described above is, for example, Li ３ PS ４－ｙ O ｙ It can be manufactured by processing LiX with a ball mill.

[0021] In one embodiment, the battery component contains 10 to 99.9% by mass of sulfide solid electrolyte. However, the amount of sulfide solid electrolyte required varies depending on the battery component. For example, when manufacturing a separator as a battery component, the amount of sulfide solid electrolyte may be 80 to 99.9% by mass, and when manufacturing an electrode, the amount of sulfide solid electrolyte may be 10 to 70% by mass.

[0022] (Binder) The binder is not particularly limited as long as it has the function of binding the sulfide solid electrolyte, and examples include styrene-butadiene-styrene block copolymer (SBS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene propylene diene rubber (EPDM), cellulose resins, polyacrylic acid, etc.

[0023] Furthermore, compound α, described below, can be used as a binder. Compound α is a compound that contains phosphorus and sulfur atoms as constituent atoms and has a disulfide bond. In such a compound, the disulfide bond may be connecting two phosphorus atoms.

[0024] In one embodiment, compound α includes one or more structures selected from the group consisting of structures (repeating units) represented by the following formulas (α1) to (α6). Preferably, compound α includes one or more structures selected from the group consisting of structures (repeating units) represented by the following formulas (α1) to (α2).

[0025]

[0026] In equations (α1) to (α4), X is any group, for example, a metal atom (e.g., Li, Na, Mg, Al, etc.). In equation (α5), Y is any group, for example, =PS ２ Therefore, in equation (α6), Z １ and Z ２ Each of these is an arbitrary base, and they may be identical or different from one another, for example, -PS ３ That is the case.

[0027] Compound α can be produced by adding an oxidizing agent to a starting compound containing phosphorus and sulfur atoms as constituent atoms (or a starting compound containing phosphorus and sulfur atoms, as well as one or more elements selected from the group consisting of oxygen, nitrogen, and halogen atoms as constituent atoms), and by reacting the starting compound with the oxidizing agent. Examples of starting compounds include PS. ４ Compounds containing the structure (e.g., Li ３ PS ４ etc.) or PS ｘ O ｙ Structure (where 1 ≤ x and 0 < y) (e.g., Li ３ PS ３ Compounds containing (e.g., O) can be used as oxidizing agents. For example, elemental halogens (e.g., I) can be used. ２ or Br ２ ) can be used. The reaction between the starting compound and the oxidizing agent can be carried out, for example, by mechanical milling.

[0028] The binders described above may be used individually or in combination of two or more types.

[0029] In one embodiment, the battery component contains 0.1 to 20% by mass of a binder. If the binder content is 0.1% by mass or more, the function of the binder (the function of integrally binding the battery components together) is fully exhibited. If the binder content is 20% by mass or less, a sufficient amount of sulfide solid electrolyte and electrode active material described later can be included, and the battery component can perform its function well.

[0030] (Electrode Active Material) In one embodiment, the battery member includes an electrode active material. The battery member including the electrode active material can be suitably used as an electrode for a battery. Here, the electrode may be either a positive electrode or a negative electrode. When the electrode is a positive electrode, examples of the electrode active material (positive electrode active material) include oxides known as positive electrode active materials such as NCM (nickel-cobalt-manganese oxide), olivine iron, sulfur, etc. When the electrode is a negative electrode, examples of the electrode active material (negative electrode active material) include silicon, graphite, lithium titanate (LTO), lithium sulfide, etc.

[0031] In one embodiment, the battery component contains 20 to 90% by mass of electrode active material.

[0032] In one embodiment, 50% or more by mass of the battery component is a sulfide solid electrolyte and binder, or is a sulfide solid electrolyte, binder and electrode active material. In the case of "substantially 100% by mass", unavoidable impurities may be included.

[0033] In one embodiment, the battery component is formed on a metal sheet or a plastic sheet. Such a battery component can be used together with the metal sheet or plastic sheet as a laminate to form a battery.

[0034] The battery component can be any sheet-like material, and its thickness is not particularly limited, but it may be, for example, 5 to 200 μm. However, the thickness will vary depending on the battery design and the battery component. For example, 5 to 100 μm is suitable for a separator, and 50 to 200 μm is suitable for an electrode.

[0035] 2. Method for Manufacturing a Battery Component A method for manufacturing a battery component according to one aspect of the present invention is a method for manufacturing a battery component according to one aspect of the present invention, comprising: forming a sheet containing a sulfide solid electrolyte and a binder; supplying the sheet to a heat treatment apparatus; and heat treating the sheet at a temperature of 150°C or higher using the heat treatment apparatus.

[0036] According to this embodiment, a battery component according to one embodiment of the present invention can be manufactured. In this embodiment, the sheet contains a binder, which causes the sheet to heat up rapidly during heat treatment. Therefore, the influence of variations in the processing time (heating time) during heat treatment is reduced, and α-crystals can be stably formed. For example, as the area of ​​the sheet increases, the processing time tends to vary depending on the position within the sheet, but even in such cases, α-crystals can be stably formed. Therefore, it is also suitable for mass production on an industrial scale. The description of the battery component according to one embodiment of the present invention can be appropriately referenced when describing the method for manufacturing the battery component according to one embodiment of the present invention.

[0037] (Formation of Sheets) The method for forming the sheets is not particularly limited. The sulfide solid electrolyte can be formed into a sheet by the action of a binder. In one embodiment, the sheet is formed by a coating method. In this case, a coating solution containing the sulfide solid electrolyte, a binder, and a solvent (which may further contain other components such as electrode active material depending on the purpose and application) is applied to any substrate to form a coating film. Then, the solvent in the coating film can be removed to form a sheet. The coating solution may be prepared, for example, by kneading the constituent components (e.g., sulfide solid electrolyte, binder, and solvent).

[0038] Before being shared with the heat treatment apparatus, the sulfide solid electrolyte does not need to be α-crystalline; for example, it can be amorphous. Sheets containing amorphous sulfide solid electrolyte and a binder are easy to mass-produce, and by supplying these to a subsequent heat treatment apparatus, a battery component, which is a sheet-like member containing α-crystalline sulfide solid electrolyte and a binder, can be manufactured.

[0039] (Supplying the sheet to the heat treatment apparatus) In this embodiment, it is important that the sheet is already formed at the stage of supplying it to the heat treatment apparatus. This ensures that α crystals are stably formed by the heat treatment.

[0040] (Heat Treatment) The sheet is heat-treated at a temperature of 150°C or higher using a heat treatment apparatus. The heat treatment temperature may be 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, 190°C or higher, 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, 250°C or higher, 260°C or higher, or 280°C or higher. The upper limit is not particularly limited and may be, for example, 400°C or lower.

[0041] In one embodiment, the heat treatment apparatus is configured to bring a heating element, preheated to 150°C or higher, into contact with the sheet. This allows for more reliable rapid heating of the sheet and more reliable formation of α-crystals. In particular, α-crystals can be reliably formed even if the sheet contains a binder that may inhibit heat conduction. The material of the heating element is not particularly limited as long as it is a solid, but from the viewpoint of thermal conductivity, for example, metals, ceramics, etc. are preferred. The metal is not particularly limited, and for example, stainless steel (SUS) can be used. The shape of the heating element is not particularly limited, but for example, it may be plate-shaped. If the heating element is plate-shaped, its thickness is preferably, for example, 0.5 mm to 500 mm, 1 mm to 500 mm, 5 mm to 500 mm, and even more preferably 10 mm to 500 mm. This allows for more reliable rapid heating of the sheet and more reliable formation of α-crystals. The heating element is preferably connected to a heat source such as a heater.

[0042] In one embodiment, the heat treatment apparatus is configured to hold a sheet between a pair of heating members that have been preheated to 150°C or higher. In one embodiment, the heating members are plate-shaped. When the heating members are plate-shaped, for example, a sheet can be heated while being held between a pair of plate-shaped heating members. The thickness of the plate-shaped heating members is as described above. In one embodiment, the heating members are roll-shaped. When the heating members are roll-shaped, for example, a sheet can be heated while being held and conveyed between a pair of roll-shaped heating members that rotate relative to one another.

[0043] In one embodiment, the sheet is heated as described above and then cooled. Note that cooling here does not necessarily mean cooling to a temperature lower than room temperature; cooling to room temperature (e.g., 15-30°C, hereafter the same) is sufficient. The heat treatment apparatus may include a cooling unit for cooling the heated sheet. In one embodiment, the cooling unit is configured to bring a cooling member, maintained at room temperature, into contact with the sheet. Note that, apart from the fact that the cooling member's temperature is approximately room temperature, the description of the heating member applies.

[0044] In one embodiment, the heating rate, processing temperature, processing time, and cooling rate in the heat treatment are set so that the XRD measurement of the obtained battery material shows one peak at 17.8 ± 0.7°. These conditions can be appropriately set according to the type, thickness, area, etc. of the sheet. The heating rate may be, for example, 20°C / min or more. The processing temperature may be, for example, 200 to 400°C. The processing time (holding time at the processing temperature) may be, for example, 0.1 to 60 seconds. The cooling rate may be, for example, 1°C / min to 500°C / min. In one embodiment, the heat treatment is terminated before the XRD measurement of the obtained battery material shows multiple peaks at 17.8 ± 0.7°. If the XRD measurement shows multiple peaks at 17.8 ± 0.7°, it is determined that β crystals or γ crystals have been formed, rather than α crystals. This means that the heating time is excessive, so the heating rate, processing temperature, processing time, and cooling rate can be readjusted so that the heating time is shortened (so that α crystals are formed). Furthermore, in this embodiment, the influence of varying processing times (heating times) in the heat treatment is reduced, allowing for stable generation of α-crystals (a wide tolerance range for heating time), thus facilitating the above-mentioned readjustment.

[0045] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0046] (Manufacturing example 1) Inside the glove box, Li ２ S 3.83g, P ２ S ５ 6.17 g and 600 g of 10 mmΦ zirconia balls were weighed and placed in a 500 mL zirconia pot, and the lid was screwed on. This was set in a Fritsch planetary ball mill P5 and operated at 220 rpm for 1 hour, followed by a 10-minute rest, for 40 cycles (the rotation direction was reversed after each cycle). The resulting powder was collected in a glove box and sieved through a 53 μm sieve, and Li ３ PS ４ The result was obtained. XRD measurements were performed on this sample (powder sample) under the following conditions. The results are shown in Figure 1.

[0047] <XRD Measurement> The powder sample was smoothly packed into a Rigaku airtight sample holder and placed in a Rigaku X-ray diffractometer (SmartLab). Measurement was performed using a focusing optical system with incident X-rays (Cu-Kα) under the conditions of scan range 2θ = 15-25° and scan speed 10° / min. From the results of the XRD measurement, the crystal structure of the sample was estimated as follows: ・α-crystal: If there is substantially one diffraction peak at 2θ = 17.8 ± 0.7° (according to the definition in this specification), it is determined to be an α-crystal. ・β-crystal, γ-crystal: If there are multiple peaks at 2θ = 17.8 ± 0.7°, it is a β-crystal or γ-crystal. Which it is is determined from other diffraction peak patterns, referring to Non-Patent Document 2. ・Amorphous: If no diffraction peaks are observed in the range of 2θ = 10.0 to 60.0°, it is determined to be amorphous. (If no diffraction peaks are observed within the scan range 2θ = 15.0–25.0°, widen the range to 2θ = 10.0–60.0° and repeat the measurement.)

[0048] (Comparative Example 1) Li obtained in Manufacturing Example 1 ３ PS ４ The powder was sandwiched between metal plates heated to 280°C and held for 2 seconds. Then, XRD measurements were performed (Figure 1, Table 1).

[0049] (Comparative Examples 2-5) Sheets were prepared in the same manner as in Comparative Example 1, except that the heating time was changed to 5 seconds (Comparative Example 2), 20 seconds (Comparative Example 3), 30 seconds (Comparative Example 4), and 60 seconds (Comparative Example 5). The crystal structure was evaluated by XRD (Figure 1, Table 1).

[0050]

[0051] Comparative Examples 1-5 are Li ３ PS ４ This is an example of an experiment in which the powder was rapidly heated, and as shown in Comparative Examples 1 to 3, precipitation of α-crystals is possible if the conditions are optimized to a narrow range. The α-crystal powder obtained in this way can be processed into battery components, but it has been difficult to industrially synthesize α-crystal powder on a large scale using this technology.

[0052] (Example 1) (Preparation of coating solution) First, a coating solution with the following composition was prepared. [Composition of coating solution] ・Li ３ PS ４: 99 parts by mass, Styrene butadiene thermoplastic elastomer (SBS) (TR2000 manufactured by JSR): 1 part by mass, Anisole: 88.7 parts by mass per 100 parts by mass of the total amount of the above two components (solids) Specifically, first, SBS was dissolved in anisole to prepare a 20% by mass SBS solution. 0.0253 g of this SBS solution was mixed with 0.43 mL of anisole and Li ３ PS ４ 0.5 g of solid electrolyte was added and the mixture was kneaded using a planetary agitator and defoamer (MAZERUSTAR KK-250S manufactured by Kurabo Industries Ltd.) under the following kneading conditions: [Kneading conditions] - Rotation: 1600 rpm - Revolution: 1600 rpm - Processing time: 300 seconds Next, the sample was treated in an ultrasonic cleaner for 5 minutes, and then kneaded twice more under the same kneading conditions as above to obtain a slurry-like coating solution.

[0053] (Preparation of Solid Electrolyte Sheet) The coating solution obtained above was applied to a 4.5 cm x 20 cm aluminum foil under the condition of a coating gap of 500 μm to form a coating film. The obtained coating film was dried at room temperature for 16 hours to remove the solvent (anisole), and then vacuum dried at 160°C for 2 hours to produce a solid electrolyte sheet (battery sheet). The film thickness of the sheet obtained at this stage was approximately 190 μm. Next, the sheet, which had been punched out to 9.9 mmΦ, was sandwiched between a pair of metal plates heated to 280°C and held for 2 seconds, then quickly sandwiched between a pair of metal plates kept at room temperature and cooled. The material of these metal plates was SUS, and its thickness was 10 mm.

[0054] (Evaluation) The solid electrolyte / SBS composition was scraped from the sheet obtained above, and the XRD was measured in the same manner as in Production Example 1 (Figure 2). In addition, the ionic conductivity was measured by the following method. The results are shown in Table 2.

[0055] <Ionic Conductivity Measurement Method> 80 mg of the sample was placed in a cylindrical tube with a diameter of 10 mmΦ and lightly pressed. Then, SUS powder v (mg) was spread on the top and bottom of the sample surface, and the tube was pressurized at 333 MPa for 5 minutes. Next, the pellet-shaped laminate was removed from the cylindrical tube, and its thickness L was measured. ０(cm) was measured. Separately, the weight of SUS powder was shaken several times and spread in a cylindrical tube with a diameter of 10 mmΦ, and after pressurizing at 333 MPa for 5 minutes, the thickness of the SUS pellet was measured. The thickness of the SUS pellet was plotted against the weight of the SUS powder, and a mathematical formula for the linear approximation curve was obtained. The amount of SUS powder v (mg) placed above and below the sample surface was substituted into the formula to calculate the thickness L １ (cm), and from L ０ subtracting L １ to determine the thickness L (cm) of the sample portion. The laminated body extracted above was placed in a coin cell, and with the four corners tightened with a torque of 0.5 Nm, the AC impedance was measured using an LCR meter (ZM2376 manufactured by NF Corporation). On the high-frequency side, the right end portion of the arc derived from lithium ion diffusion in the solid electrolyte was slightly observed, and the real part of the resistance R at the rightmost part of this arc was defined as the ion resistance of the sample. From the above-mentioned L, R, and the sample cross-sectional area A (cm ２ ), the ion conductivity σ was determined according to the formula σ = L / (RA).

[0056] (Examples 2 to 6) Sheets were prepared in the same manner as in Example 1 except that the heating time was changed to 5 seconds (Example 2), 10 seconds (Example 3), 20 seconds (Example 4), 30 seconds (Example 5), and 60 seconds (Example 6). The crystal structure was evaluated by XRD, and the ion conductivity was evaluated by the AC impedance method (Figure 2, Table 2).

[0057] (Comparative Example 6) A solid electrolyte sheet was prepared and evaluated in the same manner as in Example 1 except that heat treatment was not performed. XRD and AC impedance measurements were carried out (Figure 2, Table 2).

[0058]

[0059] Usually, Li ３ PS ４ has an ion conductivity of about 0.2 mS / cm whether it is amorphous or crystalline (β crystal). As shown in Comparative Example 6, when made into a sheet, the conductivity significantly decreases (presumably due to the addition of a binder). In contrast, it was confirmed that the conductivity is significantly improved by precipitating α crystals by rapid heating.

[0060] (Examples 7 to 12) An SBS solution, anisole, Li ３ PS ４ By finely adjusting the mixing ratio of the solid electrolyte, Li ３ PS ４ was set to 95 parts by mass, SBS was set to 5 parts by mass, and anisole was set to 95.6 parts by mass with respect to a total of 100 parts by mass of the solid content. A solid electrolyte sheet (sheet for battery) was produced in the same manner as in Example 1 except for this. The thickness of this sheet was about 190 μm. Next, the obtained sheet was sandwiched between metal plates heated to 280°C and heat-treated for holding times of 2 seconds (Example 7), 5 seconds (Example 8), 10 seconds (Example 9), 20 seconds (Example 10), 30 seconds (Example 11), and 60 seconds (Example 12). The results are shown in FIG. 3 and Table 3.

[0061] (Comparative Example 7) A solid electrolyte sheet was produced and evaluated in the same manner as in Example 7 except that heat treatment was not performed. The results are shown in FIG. 3 and Table 3.

[0062] (Comparative Example 8) A solid electrolyte sheet was produced and evaluated in the same manner as in Example 7 except that heat treatment was performed in an electric furnace heated to 280°C for 2 hours instead of sandwiching between metal plates and heating. The results are shown in FIG. 3 and Table 3.

[0063]

[0064] Usually, whether Li ３ PS ４ is amorphous or crystalline (β-crystal), the ionic conductivity is about 0.2 mS / cm. However, as shown in Comparative Examples 6 and 7, when made into a sheet, the conductivity greatly decreases (it is presumed that the addition of the binder is the main factor). On the other hand, it was confirmed that the conductivity was greatly improved by precipitating α-crystals by rapid heating. Also, it can be seen from Comparative Example 8 that even when β-crystals are precipitated by normal heating, the conductivity is improved nearly twice, but it was confirmed that when α-crystals are precipitated by rapid heating, the conductivity is further greatly improved.

[0065] Li ３ PS ４When the powder was rapidly heated, under heating conditions of 2 to 20 seconds, α-crystals precipitated, as indicated by a single XRD peak in the diffraction angle range of 17.0 ± 0.7°. However, with heating times of 30 seconds or more, two peaks were observed within the same diffraction angle range, indicating that α-crystals could not be precipitated. On the other hand, Li ３ PS ４ When rapidly heating the sheet, as can be seen from the results of heating for 60 seconds, it was found that it is possible to precipitate α crystals over a wider heating time range. When implementing the present invention at an industrial level, such as when rapidly heating a larger area sheet, it is conceivable that it may be difficult to precisely control the heating time regardless of the sheet position. In that sense, the wide range of heating conditions for achieving the desired structure control, as described above, is a great advantage.

[0066] (Examples 13-18) Li ３ PS ４ A solid electrolyte sheet (battery sheet) was manufactured in the same manner as in Example 7, except that the coating gap during film formation was set to 100 μm. The thickness of this sheet was 130 μm. Next, this sheet was sandwiched between metal plates heated to 280°C and heat-treated for holding times of 2 seconds (Example 13), 5 seconds (Example 14), 10 seconds (Example 15), 20 seconds (Example 16), 30 seconds (Example 17), and 60 seconds (Example 18). The XRD evaluation results are shown in Figure 4 and Table 4.

[0067]

[0068] Since heat is more easily transferred when the solid electrolyte sheet is thin, it is expected that the effect of rapid heating treatment will be greater. The effect of rapid heating was compared at two levels of sheet thickness, approximately 190 μm and 130 μm, but there was no difference in the ease of α crystal precipitation between the two. It can be said that heat is sufficiently transferred when the sheet thickness is approximately 200 μm or less. In lithium-ion batteries, the thickness of the solid electrolyte or electrode sheet is usually several hundred μm or less. Examples 7 to 18 clearly show that sufficient heat conduction for rapid heating is ensured at this thickness.

[0069] Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will find it easy to make many modifications to these exemplary embodiments and / or examples without substantially departing from the novel teachings and effects of the present invention. Therefore, many of these modifications fall within the scope of the present invention. All references to the documents described in this specification and to the application on which the Paris Convention priority claim of this application is based are incorporated herein by reference.

Claims

1. A sheet-like component comprising a sulfide solid electrolyte and a binder, wherein the battery component has one peak at 17.8 ± 0.7° in XRD measurement.

2. The battery component according to claim 1, further having a peak at 19.1 ± 0.5° in XRD measurement.

3. The sulfide solid electrolyte is Li ３ PS ４ The battery member according to claim 1 or 2.

4. The battery component according to any one of claims 1 to 3, wherein the binder comprises one or more selected from the group consisting of: styrene-butadiene-styrene block copolymer (SBS); polyvinylidene fluoride (PVDF); polytetrafluoroethylene (PTFE); ethylene propylene diene rubber (EPDM); cellulose resin; polyacrylic acid; and compounds containing phosphorus and sulfur atoms as constituent atoms and having disulfide bonds.

5. The battery component according to any one of claims 1 to 4, comprising 0.1 to 20% by mass of the binder.

6. The battery member according to any one of claims 1 to 5, further comprising an electrode active material.

7. A battery component according to any one of claims 1 to 6, formed on a metal sheet or a plastic sheet.

8. A method for manufacturing a battery component according to any one of claims 1 to 7, comprising: forming a sheet containing a sulfide solid electrolyte and a binder; supplying the sheet to a heat treatment apparatus; and heat treating the sheet at a temperature of 150°C or higher using the heat treatment apparatus.

9. The method for manufacturing a battery member according to claim 8, wherein the heat treatment apparatus is configured to bring a heating member, which has been preheated to 150°C or higher, into contact with the sheet.

10. The method for manufacturing a battery member according to claim 9, wherein the heat treatment apparatus is configured to sandwich the sheet between a pair of heating members that have been preheated to 150°C or higher.

11. The method for manufacturing a battery member according to claim 9 or 10, wherein the heating element is plate-shaped.

12. The method for manufacturing a battery member according to claim 9 or 10, wherein the heating element is rolled.

13. A method for manufacturing a battery component according to any one of claims 9 to 12, wherein the heating rate, processing temperature, processing time, and cooling rate in the heat treatment are set such that the XRD measurement of the obtained battery component has one peak at 17.8 ± 0.7°.

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