Solid electrolyte composition, method for manufacturing a laminate comprising a solid electrolyte sheet and electrodes, and method for manufacturing a battery

Abstract

A solid electrolyte composition 1000 according to the present invention comprises a solvent 102, a solid electrolyte 101 and a binder 103, while containing an ion conductor 111 that is dispersed in the solvent 102. If the specific surface area of the solid electrolyte 101 is represented by Sα and the specific surface area of the ion conductor 111 is represented by Sβ, 0.40 < Sβ / Sα < 0.80 is satisfied. With respect to this solid electrolyte composition 1000, 0.45 < Sβ / Sα < 0.75 may be satisfied.

Description

[Technical Field]

[0001] This disclosure relates to a solid electrolyte composition, a method for manufacturing a laminate comprising a solid electrolyte sheet and electrodes, and a method for manufacturing a battery. [Background technology]

[0002] Patent Document 1 discloses a method for producing a laminate comprising a solid electrolyte sheet and an electrode by applying a solid electrolyte composition containing a solvent, a solid electrolyte, and a binder to an electrode, and then drying the resulting coating film. This method for producing such a laminate is called the wet-on-dry method. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-126777 [Overview of the Initiative]

[0004] The purpose of this disclosure is to provide a solid electrolyte composition suitable for the wet-on-dry method.

[0005] A solid electrolyte composition in one aspect of this disclosure is: Solvent and, An ion conductor comprising a solid electrolyte and a binder, and dispersed in the solvent, Includes, The specific surface area of ​​the solid electrolyte is S α It is expressed as such, and the specific surface area of ​​the ion conductor is S β When expressed as 0.40 β / S α The condition <0.80 is satisfied.

[0006] This disclosure provides a solid electrolyte composition suitable for wet-on-dry manufacturing. [Brief explanation of the drawing]

[0007] ​[Figure 1] Figure 1 is a schematic diagram of a solid electrolyte composition according to Embodiment 1. [Figure 2] Figure 2 is a diagram illustrating a method for determining the solvent retention rate of a solid electrolyte composition. [Figure 3] Figure 3 is a flowchart showing the method for manufacturing a laminate according to Embodiment 2. [Figure 4] Figure 4 is a cross-sectional view of the laminate according to Embodiment 2. [Figure 5] Figure 5 is a cross-sectional view of the battery according to Embodiment 3. [Modes for carrying out the invention]

[0008] (Knowledge that forms the basis of this disclosure) In the field of conventional secondary batteries, organic electrolytes obtained by dissolving electrolyte salts in organic solvents are mainly used. However, secondary batteries using organic electrolytes raise concerns about leakage. It has also been pointed out that they generate a large amount of heat in the event of a short circuit or other malfunction.

[0009] On the other hand, all-solid-state rechargeable batteries, which use inorganic solid electrolytes instead of organic electrolytes, are attracting attention. All-solid-state rechargeable batteries do not leak. Because inorganic solid electrolytes have high thermal stability, it is expected that heat generation in the event of a short circuit or other malfunction will also be suppressed.

[0010] Incidentally, in order to put all-solid-state secondary batteries using solid electrolytes into practical use, it is necessary to prepare a fluid solid electrolyte composition containing a solid electrolyte. For example, a solid electrolyte sheet can be formed by coating the surface of an electrode with a solid electrolyte composition. The solid electrolyte sheet plays a role, for example, as a diaphragm in the battery. In order to improve the energy density of the battery, it is necessary to make the solid electrolyte sheet, which acts as a diaphragm, thin while preventing contact between the positive and negative electrodes.

[0011] To make the solid electrolyte sheet used as a diaphragm thinner, it is necessary to reduce the wet film thickness when applying the solid electrolyte composition using a coating machine such as a die coater. In this disclosure, wet film thickness refers to the total thickness of the film of the solid electrolyte composition formed by coating. When the wet film thickness is reduced, the applied solid electrolyte composition becomes more susceptible to the effects of electrode wettability and electrode surface irregularities. If defects such as streaks occur in the dry coated film due to these effects, it becomes difficult to guarantee its function as a diaphragm. A dry coated film refers to a film obtained by removing the solvent from the applied solid electrolyte composition. Streaks refer to streaky patterns that occur due to the uneven thickness of the coated film. Electrodes are usually composed of a wide variety of materials such as active material, solid electrolyte, and binder, and have an active material layer with a relatively large porosity. Therefore, when a solid electrolyte composition is applied on top of the active material layer by a wet-on-dry method, the solvent contained in the solid electrolyte composition penetrates into the active material layer, making it easy for streaks to occur in the coated film.

[0012] According to the inventors' research, in order to produce a good solid electrolyte sheet with suppressed surface irregularities, the solid electrolyte composition needs to retain a certain amount of solvent. When a solid electrolyte composition with poor solvent retention is used, surface irregularities are likely to occur on the solid electrolyte sheet. Therefore, when using a solid electrolyte composition with poor solvent retention, it is necessary to apply the solid electrolyte composition under conditions of a large wet film thickness in order to obtain a solid electrolyte sheet that reliably prevents contact between the positive and negative electrodes. On the other hand, if the solvent retention performance of the solid electrolyte composition can be improved, the occurrence of surface irregularities can be suppressed even when the wet film thickness is reduced. In other words, safety can be ensured even when designing a solid electrolyte sheet with a small thickness.

[0013] Furthermore, one possible method is to suppress solvent penetration by pre-compressing the electrodes before applying the solid electrolyte composition. However, if the electrodes are excessively compressed, the bonding between the current collector and the active material layer, and between the active material layer and the solid electrolyte sheet, may decrease, resulting in a decline in battery performance. Therefore, in order to produce a thin solid electrolyte sheet with suppressed surface irregularities, it is necessary to improve the solvent retention performance of the solid electrolyte composition.

[0014] To prepare a fluid solid electrolyte composition, it is necessary to mix, for example, an organic solvent with an ion conductor containing a solid electrolyte and a binder. The inventors prepared solid electrolyte compositions by mixing various ion conductors with organic solvents and investigated the solvent retention performance of the obtained solid electrolyte compositions. As a result, it was found that the solvent retention performance was improved in certain solid electrolyte compositions. Furthermore, it was found that when using a solid electrolyte composition with improved solvent retention performance, a solid electrolyte sheet with suppressed surface irregularities could be produced even when the wet film thickness was adjusted to be smaller when applying the solid electrolyte composition to an electrode. Based on these observations, the present invention was conceived.

[0015] (Summary of one aspect of this disclosure) The solid electrolyte composition relating to the first aspect of this disclosure is: Solvent and, An ion conductor comprising a solid electrolyte and a binder, and dispersed in the solvent, Includes, The specific surface area of ​​the solid electrolyte is S α It is expressed as such, and the specific surface area of ​​the ion conductor is S β When expressed as 0.40 β / S α The condition <0.80 is satisfied.

[0016] ​According to the first aspect, the solid electrolyte composition tends to be excellent in solvent retention performance. With such a solid electrolyte composition, a thin and favorable solid electrolyte sheet can be easily produced by a wet-on-dry process. According to this solid electrolyte sheet, the energy density of a battery can be improved. In a solid electrolyte sheet formed from the solid electrolyte composition, a decrease in ionic conductivity tends to be suppressed. As described above, the solid electrolyte composition is suitable for the wet-on-dry process.

[0017] In the second aspect of the present disclosure, for example, in the solid electrolyte composition according to the first aspect, 0.45 < S β / S α < 0.75 may be satisfied.

[0018] According to the second aspect, the solvent retention performance of the solid electrolyte composition can be further improved.

[0019] In the third aspect of the present disclosure, for example, in the solid electrolyte composition according to the first or second aspect, 0.45 < S β / S α < 0.70 may be satisfied.

[0020] According to the third aspect, the solvent retention performance of the solid electrolyte composition can be further improved.

[0021] In the fourth aspect of the present disclosure, for example, in the solid electrolyte composition according to any one of the first to third aspects, the binder may contain an elastomer.

[0022] According to the fourth aspect, the elastomer tends to be excellent in flexibility and elasticity. Therefore, the elastomer is suitable as a binder for a solid electrolyte sheet formed from the solid electrolyte composition.

[0023] In the fifth aspect of the present disclosure, for example, in the solid electrolyte composition according to the fourth aspect, the elastomer may contain a repeating unit derived from styrene.

[0024] According to the fifth embodiment, elastomers tend to have excellent flexibility and elasticity. Therefore, elastomers are suitable as binders for solid electrolyte sheets formed from solid electrolyte compositions.

[0025] In a sixth aspect of this disclosure, for example, in a solid electrolyte composition according to any one of the first to fifth aspects, the solvent may contain an aromatic hydrocarbon.

[0026] According to the sixth embodiment, the binder tends to have high solubility in aromatic hydrocarbons. In particular, elastomers containing repeating units derived from styrene have high solubility in aromatic hydrocarbons. When the binder has high solubility in aromatic hydrocarbons, the binder can be efficiently adsorbed by the solid electrolyte in the solid electrolyte composition. This can further improve the solvent-retaining performance of the solid electrolyte composition.

[0027] In a seventh aspect of this disclosure, for example, in the solid electrolyte composition according to the sixth aspect, the solvent may contain tetralin.

[0028] According to the seventh embodiment, tetralin has a relatively high boiling point. Tetralin not only improves the solvent retention performance of the solid electrolyte composition, but also allows for the stable production of the solid electrolyte composition through a kneading process.

[0029] In the eighth aspect of this disclosure, for example, the solid electrolyte composition according to any one of the first to seventh aspects may further contain a dispersant.

[0030] According to the eighth aspect, the dispersant can, for example, mitigate the interactions between particles of the solid electrolyte. Therefore, the dispersant allows the binder to be adsorbed more efficiently by the solid electrolyte. This can further improve the solvent-retaining performance of the solid electrolyte composition.

[0031] In the ninth aspect of this disclosure, for example, in the solid electrolyte composition according to the eighth aspect, the dispersant may contain an amine compound.

[0032] According to the ninth aspect, the amine compound is suitable for improving the dispersibility of solid electrolytes. The amine compound is suitable as a dispersant for solid electrolyte compositions.

[0033] In a tenth aspect of this disclosure, for example, in the solid electrolyte composition according to the ninth aspect, the dispersant may contain imidazoline or an imidazoline derivative.

[0034] According to the tenth embodiment, imidazoline or imidazoline derivatives are suitable for improving the dispersibility of solid electrolytes. Imidazolin or imidazoline derivatives are suitable as dispersants for solid electrolyte compositions.

[0035] The manufacturing method relating to the 11th aspect of this disclosure is: A method for manufacturing a laminate comprising a solid electrolyte sheet and an electrode, The aforementioned manufacturing method is A solid electrolyte composition according to any one of the first to tenth embodiments is applied to an electrode to form a coating film, The solvent is removed from the coated film to produce a solid electrolyte sheet, Includes.

[0036] According to the eleventh embodiment, a laminate can be manufactured that has a good solid electrolyte sheet in which the occurrence of surface irregularities is suppressed.

[0037] A battery manufacturing method according to the twelfth aspect of this disclosure is: A solid electrolyte composition according to any one of the first to tenth embodiments is applied to the first electrode to form a coating film, The solvent is removed from the coated film to produce a solid electrolyte sheet, The second electrode is placed on the solid electrolyte sheet, Includes.

[0038] According to the twelfth embodiment, the electrolyte layer contained in the battery can be made thinner. As a result, a battery with a high energy density can be manufactured.

[0039] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0040] (Embodiment 1) Figure 1 is a schematic diagram of a solid electrolyte composition 1000 according to Embodiment 1. The solid electrolyte composition 1000 comprises an ion conductor 111 and a solvent 102. The ion conductor 111 comprises a solid electrolyte 101 and a binder 103. The ion conductor 111 is dispersed or dissolved in the solvent 102. That is, the solid electrolyte 101 and the binder 103 are dispersed or dissolved in the solvent 102. The specific surface area of ​​the solid electrolyte 101 is S α It is expressed as such, and the specific surface area of ​​the ion conductor 111 is S β When expressed as 0.40 β / S α The condition <0.80 is satisfied.

[0041] With the above configuration, the solvent retention performance of the solid electrolyte composition 1000 according to Embodiment 1 is improved. Therefore, by manufacturing a solid electrolyte sheet using the solid electrolyte composition 1000, a good solid electrolyte sheet with suppressed surface irregularities can be obtained. In particular, a laminate comprising a solid electrolyte sheet with suppressed surface irregularities and electrodes can be easily fabricated. Furthermore, this solid electrolyte sheet can improve the energy density of a battery by thinning the electrolyte layer contained in the battery. Examples of batteries include all-solid-state secondary batteries.

[0042] ​Patent Document 1 discloses the fabrication of a laminate comprising a solid electrolyte sheet and electrodes by a wet-on-dry method using a solid electrolyte composition containing a solvent, a solid electrolyte, and a binder. However, with the solid electrolyte composition disclosed in Patent Document 1, it is difficult to produce a solid electrolyte sheet that suppresses the decrease in ionic conductivity while suppressing the occurrence of defects such as unevenness. Patent Document 1 does not disclose anything about how the specific surface area of ​​the ion conductors contained in the solid electrolyte composition affects the solvent retention performance of the solid electrolyte composition.

[0043] The inventors investigated solid electrolyte compositions containing an ion conductor and a solvent. As a result, the inventors found that the specific surface area S of the solid electrolyte α The specific surface area S of the ion conductor relative to the ion conductor. β Ratio S β / S α We found that when the ratio is 0.80 or higher, the solvent retention performance of the solid electrolyte composition decreases. Furthermore, we found that defects occur in the solid electrolyte sheet formed from the solid electrolyte composition in this case. In particular, when the wet film thickness was set small to thin the solid electrolyte sheet and the solid electrolyte composition was applied to the electrode, the occurrence of defects was significant. It is presumed that the occurrence of defects is due to the penetration of the solvent contained in the solid electrolyte composition into the active material layer of the electrode when the solid electrolyte composition is applied to the electrode. More specifically, solvents with low reactivity with the solid electrolyte are usually used as solvents for solid electrolyte compositions in order to suppress the decrease in the ionic conductivity of the solid electrolyte. As a result, because the interaction between the solid electrolyte and the solvent is small, the solvent is rapidly lost from around the solid electrolyte when the solid electrolyte composition is applied to the active material layer. This causes the solid electrolyte to precipitate rapidly. As a result, it is thought that defects such as streaks occur in the solid electrolyte sheet.

[0044] Furthermore, the inventors of the present invention have found that the above ratio S β / S αWe found that when the value is 0.40 or less, the ionic conductivity of the ion conductor decreases sharply. This sharp decrease in ionic conductivity is presumed to be due to the solid electrolyte particles excessively adsorbing the binder, and the binder being positioned between multiple solid electrolyte particles, thereby inhibiting ionic conduction.

[0045] Based on the above findings, the inventors conducted further investigations. As a result, the above ratio S β / S α We found that by using a solid electrolyte composition in which the specific surface area of ​​the solid electrolyte 101 is greater than 0.40 and less than 0.80, it is possible to suppress the deterioration of the solvent-retaining performance and to suppress the rapid decrease in the ionic conductivity of the ion conductor. As described above, in Embodiment 1, the specific surface area of ​​the solid electrolyte 101 is S α It is expressed as such, and the specific surface area of ​​the ion conductor 111 is S β When expressed as 0.40 β / S α The condition <0.80 is satisfied. This improves the solvent retention performance of the solid electrolyte composition 1000. Furthermore, by using a solid electrolyte composition with high solvent retention performance, thinner solid electrolyte sheets can be easily manufactured by the wet-on-dry method. This solid electrolyte sheet can improve the energy density of the battery.

[0046] In Embodiment 1, ratio S β / S α Regarding 0.45 β / S α The condition <0.75 may be satisfied. This can further improve the solvent retention performance of the solid electrolyte composition 1000. Furthermore, with such a solid electrolyte composition 1000, thinner solid electrolyte sheets can be easily manufactured by a wet-on-dry process. With this solid electrolyte sheet, the energy density of the battery can be further improved.

[0047] In Embodiment 1, ratio S β / S α ​​Regarding 0.45 β / S α The condition <0.70 may also be satisfied. This can further improve the solvent retention performance of the solid electrolyte composition 1000. Furthermore, with such a solid electrolyte composition 1000, thinner solid electrolyte sheets can be easily manufactured by a wet-on-dry process. With this solid electrolyte sheet, the energy density of the battery can be further improved.

[0048] Specific surface area S of solid electrolyte 101 α For example, this refers to the specific surface area of ​​the particle group of the solid electrolyte 101. Specific surface area S α This can be measured, for example, by the following BET (Brunauer-Emmett-Teller) multipoint method. First, the nitrogen adsorption amount of the solid electrolyte 101 is measured by the nitrogen gas adsorption method using a commercially available gas adsorption meter. For nitrogen adsorption, multiple arbitrary points (e.g., 10 points) are measured at relative pressures in the range of 0.05 to 0.30. Next, based on the obtained data, the specific surface area S is calculated using the BET (Brunauer-Emmett-Teller) analysis method. α (Unit: m) 2 The specific surface area (S) can be calculated. Note that if no operations such as crushing or sintering are performed on the solid electrolyte 101 particle group during the preparation of the solid electrolyte composition 1000, the specific surface area of ​​the solid electrolyte 101 does not change significantly before and after the preparation of the solid electrolyte composition 1000. In this case, the specific surface area measured for the solid electrolyte 101 particle group used as a raw material for preparing the solid electrolyte composition 1000 is used as the specific surface area S. α It can be considered as follows: Alternatively, the ion conductor 111 contained in the solid electrolyte sheet 201 can be collected, and the ion conductor 111 can be washed with a solvent in which the solid electrolyte 101 constituting the ion conductor 111 is insoluble and other constituent materials, such as the binder 103, are dissolved to obtain a group of solid electrolyte particles 101, and the specific surface area can be measured to obtain the specific surface area S α ​This can be obtained. Here, the ion conductor 111 is collected, for example, by scraping off a part of the solid electrolyte sheet. Also, for example, when a styrene-based elastomer is used as the binder 103, aromatic hydrocarbon solvents, more specifically toluene, can be used as solvents for such cleaning.

[0049] Specific surface area S of ion conductor 111 β For example, this refers to the specific surface area of ​​the particle group of the ion conductor 111. Specific surface area S β Except for using a group of particles of the ion conductor 111 as the measurement sample, the specific surface area S α It can be measured by the same method. The particle group of ion conductors 111 can be obtained, for example, by drying the solid electrolyte composition 1000, thoroughly loosening the dried material by hand without using mechanical equipment such as a pulverizer, and then drying it further. In addition, the specific surface area S can be obtained by taking a sample of the ion conductors 111 contained in the solid electrolyte sheet 201 and measuring its specific surface area. β You can obtain this.

[0050] The solvent retention performance of the solid electrolyte composition 1000 can be evaluated by the solvent retention rate when the solid electrolyte composition 1000 is dropped onto an electrode. Figure 2 is a diagram illustrating a method for determining the solvent retention rate of the solid electrolyte composition 1000. The solvent retention rate can be determined by the following method. First, under conditions of 25°C, a droplet of solid electrolyte composition 1000 with a diameter of 3 mm to 5 mm is dropped onto an electrode. As the electrode, for example, a negative electrode formed by coating a composite material containing graphite and sulfide solid electrolyte onto a metal foil can be used. When the droplet is dropped, the solid electrolyte composition 1000 and the solvent 102 that seeps out from the solid electrolyte composition 1000 spread on the electrode. Figure 2 is a plan view image of the spread solid electrolyte composition 1000 and solvent 102. As shown in Figure 2, the solvent 102 spreads to surround the solid electrolyte composition 1000. Three minutes after dropping the liquid droplet, the area S1 (mm²) of the wetted solvent 102 was measured. 2) and the area S2 (mm²) of the solid electrolyte composition 1000 2 ) and are measured. In Figure 2, area S1 corresponds to the area of ​​a circle with diameter R1. Area S2 corresponds to the area of ​​a circle with diameter R2. The solvent retention rate of the solid electrolyte composition 1000 can be calculated based on areas S1 and S2 using the following formula. Solvent retention rate (%) = 100 × S² / S¹

[0051] It should be noted that the solvent retention rate measured by the above method is a value that can vary depending on the composition of the electrode used, the surface condition of the electrode, the porosity of the electrode, etc. Therefore, when evaluating the solvent retention performance of solid electrolyte composition 1000, it is necessary to standardize the electrodes used and evaluate them relatively.

[0052] The "solid electrolyte sheet" may also be a solid electrolyte layer supported by electrodes.

[0053] The solid electrolyte composition 1000 may be a fluid slurry. If the solid electrolyte composition 1000 is fluid, it is possible to form a solid electrolyte sheet by a wet method such as a coating method.

[0054] The solid electrolyte composition 1000 according to Embodiment 1 will be described in detail below.

[0055] [Solid electrolyte composition] The solid electrolyte composition 1000 in Embodiment 1 comprises an ion conductor 111 and a solvent 102. The ion conductor 111 comprises a solid electrolyte 101 and a binder 103. The ion conductor 111, solid electrolyte 101, solvent 102, and binder 103 will be described in detail below.

[0056] <Solid electrolyte> In Embodiment 1, the solid electrolyte 101 can be a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, a polymer solid electrolyte, a complex hydride solid electrolyte, or the like. The solid electrolyte 101 may also contain a sulfide solid electrolyte.

[0057] In this disclosure, “oxide solid electrolyte” means a solid electrolyte containing oxygen. The oxide solid electrolyte may further contain anions other than oxygen, such as sulfur and halogen elements.

[0058] In this disclosure, "halide solid electrolyte" means a solid electrolyte that contains a halogen element but does not contain sulfur. In this disclosure, a sulfur-free solid electrolyte means a solid electrolyte represented by a composition formula that does not contain a sulfur element. Therefore, a solid electrolyte containing a very small amount of sulfur, for example, a sulfur component of 0.1% by mass or less, is included in the category of sulfur-free solid electrolytes. A halide solid electrolyte may also contain oxygen as an anion other than a halogen element.

[0059] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These can be used. These include LiX, Li2O, and MO q Li p MO q The following may be added. In "LiX", element X is at least one selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q In ", element M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q In this expression, p and q are independent natural numbers.

[0060] As the sulfide solid electrolyte, for example, Li2S-P2S5 glass ceramics may be used. Li2S-P2S5 glass ceramics may contain LiX, Li2O, MO q Li pMO q Other materials may be added, and two or more selected from LiCl, LiBr, and LiI may be added. Since Li2S-P2S5-based glass ceramics are relatively soft materials, a solid electrolyte sheet containing Li2S-P2S5-based glass ceramics can be used to manufacture batteries with higher durability.

[0061] Examples of oxide solid electrolytes include NASICON-type solid electrolytes represented by LiTi2(PO4)3 and its elemental substitutions, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGe4O 16 , LiSICON-type solid electrolytes such as Li4SiO4, LiGeO4 and their elemental substitutions, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those represented by elemental substitutions thereof, Li-BO compounds such as Li3PO4 and its N-substituted counterparts, LiBO2 and Li3BO3, with Li2SO4, Li2CO3, etc. added as a base, as well as glass ceramics, can be used.

[0062] The halide solid electrolyte includes, for example, Li, M1, and X. M1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li. X is at least one selected from the group consisting of F, Cl, Br, and I. Because the halide solid electrolyte has high thermal stability, it can improve the safety of the battery. Furthermore, because the halide solid electrolyte does not contain sulfur, it can suppress the generation of hydrogen sulfide gas.

[0063] In this disclosure, “metallic elements” are B, Si, Ge, As, Sb, and Te.

[0064] In this disclosure, “metallic elements” refers to all elements in groups 1 through 12 of the periodic table, excluding hydrogen, and all elements in groups 13 through 16 of the periodic table, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se.

[0065] In other words, in this disclosure, "metalloid elements" and "metal elements" are groups of elements that can become cations when they form inorganic compounds with halogen elements.

[0066] For example, the halide solid electrolyte may be a material represented by the following compositional formula (1). Li α M1 β X γ ...Equation (1)

[0067] In the above empirical formula (1), α, β, and γ are each independently greater than 0. γ can be 4, 6, etc.

[0068] With the above configuration, the ionic conductivity of the halide solid electrolyte is improved, and therefore the ionic conductivity of the solid electrolyte sheet formed from the solid electrolyte composition 1000 in Embodiment 1 can be improved. When this solid electrolyte sheet is used in a battery, the cycle characteristics of the battery can be further improved.

[0069] In the above compositional formula (1), element M1 may include Y (=yttrium). That is, the halide solid electrolyte may contain Y as a metallic element.

[0070] A halide solid electrolyte containing Y may be represented, for example, by the following compositional formula (2). Li a Me b Y c X6...Formula (2)

[0071] In formula (2), a, b, and c may satisfy a+mb+3c=6 and c>0. The element Me is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. m represents the valence of the element Me. In the case where the element Me includes a plurality of types of elements, mb is the total value of products of the composition ratio of each element and the valence of the corresponding element. For example, when Me includes element Me1 and element Me2, the composition ratio of element Me1 is b1, the valence of element Me1 is m1, the composition ratio of element Me2 is b2, and the valence of element Me2 is m2, mb is represented by m1b1+m2b2. In the above composition formula (2), the element X is at least one selected from the group consisting of F, Cl, Br, and I.

[0072] The element Me may be, for example, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, Gd and Nb.

[0073] As the halide solid electrolyte, for example, the following materials may be used. According to the following materials, the ionic conductivity of the solid electrolyte 101 is further improved, so the ionic conductivity of a solid electrolyte sheet formed from the solid electrolyte composition 1000 in Embodiment 1 can be improved. According to this solid electrolyte sheet, the cycle characteristics of a battery can be further improved.

[0074] The halide solid electrolyte may be a material represented by the following composition formula (A1). Li 6-3d Y d dX6···Formula (A1)

[0075] In composition formula (A1), the element X is at least one selected from the group consisting of Cl, Br, and I. In composition formula (A1), d satisfies 0<d<2.

[0076] The halide solid electrolyte may be a material represented by the following composition formula (A2). Li3YX6···Formula (A2)

[0077] In the composition formula (A2), element X is at least one selected from the group consisting of Cl, Br, and I.

[0078] The halide solid electrolyte may be a material represented by the following compositional formula (A3). Li 3-3δ Y 1+δ Cl6...Formula (A3)

[0079] In empirical formula (A3), δ satisfies 0 < δ ≤ 0.15.

[0080] The halide solid electrolyte may be a material represented by the following compositional formula (A4). Li 3-3δ Y 1+δ Br6...Formula (A4)

[0081] In empirical formula (A4), δ satisfies 0 < δ ≤ 0.25.

[0082] The halide solid electrolyte may be a material represented by the following compositional formula (A5). Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y ...Formula (A5)

[0083] In compositional formula (A5), the element Me is at least one selected from the group consisting of Mg, Ca, Sr, Ba, and Zn.

[0084] Furthermore, in the above composition formula (A5), -1 < δ < 2, 0 <a<3、 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0≦y≦6, and (x+y)≦6, The conditions are met.

[0085] The halide solid electrolyte may be a material represented by the following compositional formula (A6). Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y ... Formula (A6)

[0086] In the compositional formula (A6), the element Me is at least one selected from the group consisting of Al, Sc, Ga, and Bi.

[0087] Further, in the above-mentioned compositional formula (A6), -1<δ<1, 0<a<2, 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6, are satisfied.

[0088] The halide solid electrolyte may be a material represented by the following compositional formula (A7). Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y ... Formula (A7)

[0089] In the above-mentioned compositional formula (A7), the element Me is at least one selected from the group consisting of Zr, Hf and Ti.

[0090] Further, in the above-mentioned compositional formula (A7), -1<δ<1, 0<a<1.5, 0<(3-3δ-a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6, are satisfied.

[0091] The halide solid electrolyte may be a material represented by the following composition formula (A8). Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y ... Formula (A8)

[0092] In the composition formula (A8), the element Me is at least one selected from the group consisting of Ta and Nb.

[0093] Further, in the above composition formula (A8), -1<δ<1, 0<a<1.2, 0<(3-3δ-2a), 0<(1+δ-a), 0≦x≦6, 0≦y≦6, and (x+y)≦6, is satisfied.

[0094] The halide solid electrolyte may be a compound containing Li, M2, O (oxygen) and X2. The element M2 contains, for example, at least one selected from the group consisting of Nb and Ta. Also, X2 is at least one selected from the group consisting of F, Cl, Br and I.

[0095] The compound containing Li, M2, X2 and O (oxygen) has, for example, a composition formula: Li x M2O y X2 5+x―2y may be represented by the above. Here, x may satisfy 0.1<x<7.0. y may satisfy 0.4<y<1.9.

[0096] As more specific examples of the halide solid electrolyte, there may be mentioned Li3Y(Cl,Br,I)6, Li 2.7 Y 1.1(Cl,Br,I)6, Li2Mg(F,Cl,Br,I)4, Li2Fe(F,Cl,Br,I)4, Li(Al,Ga,In)(F,Cl,Br,I)4, Li3(Al,Ga,In)(F,Cl,Br,I)6, Li3(Ca,Y,Gd)(Cl,Br,I)6, Li 2.7 (Ti,Al)F6, Li 2.5 (Ti,Al)F6, Li(Ta,Nb)O(F,Cl)4, etc., can be used. In this disclosure, when an element in a formula is represented as "(Al,Ga,In)", this notation indicates at least one element selected from the group of elements in parentheses. That is, "(Al,Ga,In)" is synonymous with "at least one element selected from the group consisting of Al, Ga, and In". The same applies to other elements.

[0097] As a polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further improved. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. A single lithium salt may be used, or two or more may be used in combination.

[0098] Examples of complex hydride solid electrolytes that can be used include LiBH4-LiI and LiBH4-P2S5.

[0099] The shape of the solid electrolyte 101 is not particularly limited and may be needle-shaped, spherical, ellipsoidal, or the like. The shape of the solid electrolyte 101 may also be particulate.

[0100] If the solid electrolyte 101 is particulate (for example, spherical), the median diameter of the solid electrolyte 101 may be 1 μm or more and 100 μm or less, or 1 μm or more and 10 μm or less. When the median diameter of the solid electrolyte 101 is 1 μm or more and 100 μm or less, the solid electrolyte 101 can be easily dispersed in the solvent 102.

[0101] When the solid electrolyte 101 is particulate (for example, spherical), the median diameter of the solid electrolyte 101 may be 0.1 μm or more and 5 μm or less, or 0.5 μm or more and 3 μm or less. When the median diameter of the solid electrolyte 101 is 0.1 μm or more and 5 μm or less, the solid electrolyte sheet produced from the solid electrolyte composition 1000 may have higher surface smoothness and a denser structure.

[0102] The median diameter refers to the particle size at which the cumulative volume in the volume-based particle size distribution equals 50%. The volume-based particle size distribution is determined by laser diffraction scattering. The same applies to the other materials listed below.

[0103] Specific surface area S of solid electrolyte 101 α is 0.1m 2 / g or more 100m 2 It may be less than / g, 1m 2 / g or more 10m 2 It may be less than / g. Specific surface area S of solid electrolyte 101 α 0.1m 2 / g or more 100m 2 If the amount is less than or equal to / g, the solid electrolyte 101 can be easily dispersed in the solvent 102. Specific surface area S α This can be measured by the method described above.

[0104] The ionic conductivity of solid electrolyte 101 is 0.01 mS / cm². 2 It may be greater than or equal to 0.1 mS / cm 2 It may be greater than or equal to 1 mS / cm 2 The above is also acceptable. The ionic conductivity of the solid electrolyte 101 is 0.01 mS / cm. 2In such cases, the output characteristics of the battery can be improved.

[0105] <Binder> The binder 103 can improve the dispersibility of the solid electrolyte 101 in the solvent 102 and the adhesion between the particles of the solid electrolyte 101. Examples of binders 103 include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamide-imide, polyacrylonitrile, polyacrylic acid, polymethyl polyacrylate, polyethyl polyacrylate, polyhexyl polyacrylate, polymethacrylic acid, polymethyl polymethacrylate, polyethyl polymethacrylate, polyhexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylene sulfide, hexafluoropolypropylene, styrene-butadiene rubber, carboxymethylcellulose, and ethylcellulose. As binder 103, copolymers synthesized using two or more monomers selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid ester, acrylic acid, and hexadiene may also be used. These may be used individually or in combination of two or more.

[0106] The binder 103 may contain an elastomer from the viewpoint of excellent binding properties. An elastomer refers to a polymer that has rubber elasticity. The elastomer used as the binder 103 may be a thermoplastic elastomer or a thermosetting elastomer. Examples of elastomers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), hydrogenated styrene-butylene rubber (HSBR), and acrylated butadiene rubber (ABR). A mixture containing two or more of these selected materials may be used as binder 103. When binder 103 contains an elastomer, the solid electrolyte sheet produced from solid electrolyte composition 1000 tends to exhibit excellent flexibility and elasticity. In this case, battery life tends to improve.

[0107] The elastomer contained in binder 103 may contain repeating units derived from styrene. Repeating units refer to molecular structures derived from monomers and are sometimes called constituent units. In this disclosure, elastomers containing repeating units derived from styrene may be referred to as styrene-based elastomers. Styrene-based elastomers are suitable as binders for solid electrolyte sheets because they have superior flexibility and elasticity. The content of repeating units derived from styrene in the styrene-based elastomer is not particularly limited, and is, for example, 10% by mass or more and 70% by mass or less.

[0108] Examples of styrene-based elastomers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-butylene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butylene rubber (HSBR). Binder 103 may contain SBR or SEBS as the styrene-based elastomer. A mixture containing two or more selected from these may be used as binder 103. Because styrene-based elastomers are flexible, binder 103 containing a styrene-based elastomer can impart flexibility to the solid electrolyte sheet produced from the solid electrolyte composition 1000. As a result, the electrolyte layer of a battery using the solid electrolyte sheet can be made thinner, and the energy density of the battery can be further improved.

[0109] The polymer contained in binder 103 may contain modifying groups. A modifying group refers to a functional group that chemically modifies all repeating units in the polymer chain, some repeating units in the polymer chain, or the terminal portion of the polymer chain. Modifying groups can be introduced into the polymer chain by substitution reactions, addition reactions, etc. Examples of modifying groups include elements with relatively high electronegativity, such as O and N, and elements with relatively low electronegativity, such as Si. Modifying groups containing such elements can impart polarity to the polymer. Examples of modifying groups include carboxylic acid groups, acid anhydride groups, acyl groups, hydroxyl groups, sulfo groups, sulfanyl groups, phosphoric acid groups, phosphonic acid groups, isocyanate groups, epoxy groups, silyl groups, amino groups, nitrile groups, and nitro groups. A specific example of an acid anhydride group is the maleic anhydride group. In binder 103, if the polymer contains modifying groups, the dispersibility of the solid electrolyte 101 contained in the solid electrolyte composition 1000 may be further improved. Binder 103 may contain SBR into which modified groups have been introduced.

[0110] The weight-average molecular weight (M) of the polymer contained in the binder 103 in Embodiment 1 w The weight-average molecular weight of the polymer contained in the binder 103 may be, for example, 1,000 to 1,000,000, or 10,000 to 500,000. By having a weight-average molecular weight of 1,000 or more of the polymer contained in the binder 103, the particles of the solid electrolyte 101 can adhere to each other with sufficient adhesive strength. By having a weight-average molecular weight of 1,000,000 or less of the polymer contained in the binder 103, ion conduction between the particles of the solid electrolyte 101 is less likely to be inhibited by the binder 103, thereby improving the charge and discharge characteristics of the battery. The weight-average molecular weight of the polymer contained in the binder 103 can be determined, for example, by gel permeation chromatography (GPC) measurement using polystyrene as a standard sample. In other words, the weight-average molecular weight is a value converted using polystyrene. In GPC measurement, chloroform may be used as the eluent.

[0111] <Ionic Conductors> As described above, the ion conductor 111 includes a solid electrolyte 101 and a binder 103. In the ion conductor 111, multiple particles of the solid electrolyte 101 are bound together via the binder 103.

[0112] In the ion conductor 111, the ratio of the mass of the binder 103 to the mass of the solid electrolyte 101 is, for example, 1% by mass or more, may be 2% by mass or more, 3% by mass or more, 5% by mass or more, or 8% by mass or more. The upper limit of the ratio of the mass of the binder 103 to the mass of the solid electrolyte 101 is, for example, 10% by mass.

[0113] The shape of the ion conductor 111 is not particularly limited and may be needle-shaped, spherical, ellipsoidal, or the like. The shape of the ion conductor 111 may also be particulate.

[0114] If the ion conductor 111 is particulate (for example, spherical), the median diameter of the ion conductor 111 may be 0.1 μm or more and 10 μm or less, or 0.5 μm or more and 3 μm or less.

[0115] Specific surface area S of ion conductor 111 β is 0.04m 2 / g or more 80m 2 It may be less than / g, 1m 2 / g or more 15m 2 It may be less than / g, and 1.5m 2 / g or more 5m 2 It may be less than / g, and 2.0m 2 / g or more 4.0m 2 It may be less than / g. Specific surface area S β This can be measured by the method described above.

[0116] The ionic conductivity of ion conductor 111 is 0.01 mS / cm². 2 It may be greater than or equal to 0.1 mS / cm 2 It may be greater than or equal to 1 mS / cm 2 That's fine too.

[0117] In the ion conductor 111 of the solid electrolyte composition 1000, the decrease in ionic conductivity tends to be suppressed. The decrease in ionic conductivity in the ion conductor 111 can be evaluated, for example, by the ratio of the ionic conductivity of the ion conductor 111 to the ionic conductivity of the solid electrolyte 101. In this disclosure, this ratio may be referred to as the ionic conductivity maintenance rate. The ionic conductivity maintenance rate is, for example, 30% or more, may be 40% or more, may be 50% or more, may be 60% or more, or may be 70% or more. The upper limit of the ionic conductivity maintenance rate is not particularly limited, and is, for example, 95%.

[0118] The ion conductor 111 can be prepared, for example, by mixing a solid electrolyte 101 and a binder 103. The mixing method is not particularly limited, and examples include a dry, mechanical grinding and mixing method of the solid electrolyte 101 and binder 103. A wet method may also be used, in which the solid electrolyte 101 is dispersed in a solution or dispersion containing the binder 103 and then mixed. The wet method allows for simple and uniform mixing of the binder 103 with the solid electrolyte 101. The solid electrolyte composition 1000 may also be prepared by preparing the ion conductor 111 in a solvent using the wet method.

[0119] <Solvent> Solvent 102 may be an organic solvent. An organic solvent is a compound containing carbon, such as a compound containing elements such as carbon, hydrogen, nitrogen, oxygen, sulfur, or halogen.

[0120] The solvent 102 may contain at least one selected from the group consisting of hydrocarbons, compounds having halogen groups, and compounds having ether bonds.

[0121] Hydrocarbons are compounds consisting only of carbon and hydrogen. Hydrocarbons may be aliphatic hydrocarbons. Hydrocarbons may be saturated hydrocarbons or unsaturated hydrocarbons. Hydrocarbons may be linear or branched. The number of carbon atoms in a hydrocarbon is not particularly limited and may be seven or more. By using hydrocarbons, a solid electrolyte composition 1000 with excellent dispersibility of the ion conductor 111 can be obtained. Furthermore, the decrease in the ionic conductivity of the solid electrolyte 101 due to mixing with the solvent 102 can be suppressed.

[0122] The hydrocarbon may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be monocyclic or polycyclic. The presence of a ring structure in the hydrocarbon allows the ion conductor 111 to disperse easily in the solvent 102. From the viewpoint of improving the dispersibility of the ion conductor 111 in the solid electrolyte composition 1000, the hydrocarbon may contain aromatic hydrocarbons. That is, the solvent 102 may contain aromatic hydrocarbons. The hydrocarbon may contain aromatic hydrocarbons. Styrene elastomers have high solubility in aromatic hydrocarbons. Therefore, if the binder 103 contains a styrene elastomer and the solvent 102 also contains aromatic hydrocarbons, the binder 103 can be efficiently adsorbed by the solid electrolyte 101 in the solid electrolyte composition 1000. This can further improve the solvent-holding performance of the solid electrolyte composition 1000.

[0123] A compound having a halogen group may consist only of carbon and hydrogen in the parts other than the halogen group. That is, a compound having a halogen group means a compound in which at least one hydrogen atom contained in a hydrocarbon is replaced with a halogen group. Examples of halogen groups include F, Cl, Br, and I. At least one selected from the group consisting of F, Cl, Br, and I may be used as the halogen group. A compound having a halogen group may have high polarity. By using a compound having a halogen group in solvent 102, the ion conductor 111 can be easily dispersed in solvent 102, so a solid electrolyte composition 1000 with excellent dispersibility can be obtained. As a result, a solid electrolyte sheet produced from the solid electrolyte composition 1000 may have excellent ionic conductivity and a denser structure.

[0124] The number of carbon atoms in the halogen-containing compound is not particularly limited and may be seven or more. This allows for the stable production of the solid electrolyte composition 1000 because the halogen-containing compound is less volatile. The halogen-containing compound may have a large molecular weight; that is, it may have a high boiling point.

[0125] The compound having a halogen group may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be monocyclic or polycyclic. The presence of a ring structure in the compound having a halogen group allows the ion conductor 111 to disperse easily in the solvent 102. From the viewpoint of improving the dispersibility of the ion conductor 111 in the solid electrolyte composition 1000, the compound having a halogen group may contain an aromatic hydrocarbon. The compound having a halogen group may contain an aromatic hydrocarbon.

[0126] A compound having a halogen group may have only a halogen group as a functional group. In this case, the number of halogens contained in the compound having a halogen group is not particularly limited. At least one selected from the group consisting of F, Cl, Br, and I may be used as the halogen group. By using such a compound in solvent 102, the ion conductor 111 can be easily dispersed in solvent 102, so that a solid electrolyte composition 1000 with excellent dispersibility can be obtained. As a result, the solid electrolyte sheet produced from the solid electrolyte composition 1000 may have excellent ionic conductivity and a denser structure. By using such a compound in solvent 102, the solid electrolyte sheet produced from the solid electrolyte composition 1000 may easily have a dense structure with fewer pinholes, unevenness, etc.

[0127] The compound having a halogen group may be a halogenated hydrocarbon. A halogenated hydrocarbon means a compound in which all the hydrogen atoms in the hydrocarbon are replaced by halogen groups. By using a halogenated hydrocarbon as solvent 102, the ion conductor 111 can be easily dispersed in solvent 102, so a solid electrolyte composition 1000 with excellent dispersibility can be obtained. As a result, the solid electrolyte sheet produced from the solid electrolyte composition 1000 may have excellent ionic conductivity and a denser structure. By using such a compound as solvent 102, the solid electrolyte sheet produced from the solid electrolyte composition 1000 may easily have a dense structure with fewer pinholes, unevenness, etc.

[0128] Compounds having ether bonds may consist only of carbon and hydrogen in the parts other than the ether bond. That is, a compound having an ether bond means a compound in which at least one of the CC bonds contained in a hydrocarbon is replaced with a COC bond. Compounds having ether bonds may have high polarity. By using a compound having an ether bond in solvent 102, the ion conductor 111 can be easily dispersed in solvent 102. Therefore, a solid electrolyte composition 1000 with excellent dispersibility can be obtained. As a result, a solid electrolyte sheet produced from the solid electrolyte composition 1000 may have excellent ionic conductivity and a denser structure.

[0129] The compound having an ether bond may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be monocyclic or polycyclic. The presence of a ring structure in the compound having an ether bond allows the ion conductor 111 to disperse easily in the solvent 102. From the viewpoint of improving the dispersibility of the ion conductor 111 in the solid electrolyte composition, the compound having an ether bond may contain an aromatic hydrocarbon. The compound having an ether bond may contain an aromatic hydrocarbon.

[0130] Examples of solvent 102 include ethylbenzene, mesitylene, pseudocumene, p-xylene, cumene, tetralin, m-xylene, dibutyl ether, 1,2,4-trichlorobenzene, chlorobenzene, 2,4-dichlorotoluene, anisole, o-chlorotoluene, m-dichlorobenzene, p-chlorotoluene, o-dichlorobenzene, 1,4-dichlorobutane, and 3,4-dichlorotoluene. These may be used individually or in combination of two or more.

[0131] From a cost perspective, commercially available xylene (mixed xylene) may be used as solvent 102. For example, a mixed xylene in which o-xylene, m-xylene, p-xylene, and ethylbenzene are mixed in a mass ratio of 24:42:18:16 may be used.

[0132] The solvent 102 may contain tetralin. Tetralin has a relatively high boiling point. Tetralin not only improves the solvent retention performance of the solid electrolyte composition 1000, but also allows for the stable production of the solid electrolyte composition 1000 through the kneading process.

[0133] The boiling point of solvent 102 may be between 100°C and 250°C. Solvent 102 may also be a liquid at room temperature (25°C). Since such a solvent does not easily volatilize at room temperature, the solid electrolyte composition 1000 can be manufactured stably. Therefore, a solid electrolyte composition 1000 that can be easily applied to the surface of an electrode or substrate can be obtained. The solvent 102 contained in the solid electrolyte composition 1000 can be easily removed by drying as described later.

[0134] The water content of solvent 102 may be 10 ppm by mass or less. Reducing the water content can suppress the decrease in ionic conductivity due to the reaction of solid electrolyte 101. Methods for reducing the water content include dehydration using molecular sieves and dehydration by bubbling with an inert gas such as nitrogen or argon. Dehydration by bubbling with an inert gas is recommended from the viewpoint that oxygen can be removed at the same time as water. The water content can be measured with a Karl Fischer moisture analyzer.

[0135] The solvent 102 may be a liquid capable of dispersing the solid electrolyte 101. The solid electrolyte 101 does not necessarily have to be dissolved in the solvent 102. By preventing the solid electrolyte 101 from dissolving in the solvent 102, a solid electrolyte composition 1000 can be produced in which the ion-conducting phase formed during the production of the solid electrolyte 101 is preserved. Therefore, a decrease in ion conductivity can be suppressed in a solid electrolyte sheet produced using this solid electrolyte composition 1000.

[0136] The solvent 102 may partially or completely dissolve the solid electrolyte 101. Dissolving the solid electrolyte 101 can improve the density of the solid electrolyte sheet produced using this solid electrolyte composition 1000.

[0137] <Dispersant> The solid electrolyte composition 1000 may contain a dispersant. The dispersant may be a low molecular weight dispersant or a high molecular weight dispersant. For example, commercially available dispersants, wetting agents, or surfactants may be used as the dispersant. The dispersant can mitigate the interactions between the particles of the solid electrolyte 101. Therefore, the dispersant allows the binder 103 to be efficiently adsorbed onto the solid electrolyte 101. This can further improve the solvent retention performance of the solid electrolyte composition 1000.

[0138] In the solid electrolyte composition 1000, the dispersant may contain an amine compound. The amine compound is suitable for improving the dispersibility of the solid electrolyte 101. The amine compound is suitable as a dispersant for the solid electrolyte composition 1000. Examples of amine compounds include aliphatic amines such as methylamine and dimethylamine, aromatic amines such as aniline, and heterocyclic amines such as imidazole and imidazoline.

[0139] In the solid electrolyte composition 1000, the dispersant may contain imidazoline or an imidazoline derivative. Imidazolin or an imidazoline derivative is preferable because it improves the dispersibility of the solid electrolyte 101. Imidazolin or an imidazoline derivative is preferable as a dispersant for the solid electrolyte composition 1000. Examples of imidazoline derivatives include 1-hydroxyethyl-2-alkenylimidazoline.

[0140] In the solid electrolyte composition 1000, the ratio of the mass of the dispersant to the mass of the solid electrolyte 101 is not particularly limited, and may be, for example, 0.001% by mass or more and 10% by mass or less, or 0.01% by mass or more and 1.0% by mass or less. When the ratio of the mass of the dispersant is 0.001% by mass or more, the dispersibility of the solid electrolyte 101 can be improved in the solid electrolyte composition 1000. When the ratio of the mass of the dispersant is 10% by mass or less, the decrease in the ionic conductivity of the solid electrolyte 101 can be suppressed.

[0141] <Solid electrolyte composition> The solid electrolyte composition 1000 may be in the form of a paste or a dispersion. The ion conductor 111 is, for example, particles. In the solid electrolyte composition 1000, the particles of the ion conductor 111 are mixed with the solvent 102. In the production of the solid electrolyte composition 1000, the method of mixing the ion conductor 111 and the solvent 102, or the method of mixing the solid electrolyte 101, solvent 102, and binder 103 is not particularly limited. For example, mixing methods using mixing devices such as agitators, shakers, ultrasonic mixers, and rotary mixers are possible. For example, mixing methods using dispersion kneading devices such as high-speed homogenizers, thin-film swirling high-speed mixers, ultrasonic homogenizers, ball mills, bead mills, planetary mixers, sand mills, roll mills, and kneaders are possible. These mixing methods may be used individually or in combination of two or more.

[0142] The solid electrolyte composition 1000 can be manufactured, for example, by the following method. First, the solid electrolyte 101 and the solvent 102 are mixed, and then a binder solution, a dispersant solution, etc., are added. The resulting mixture is subjected to high-speed shearing using an in-line dispersion and grinding machine. Through this process, ion conductors 111 are formed, and the ion conductors 111 are dispersed and stabilized in the solvent 102, thereby producing a solid electrolyte composition 1000 with superior fluidity. Furthermore, from the viewpoint of producing a solid electrolyte composition 1000 with superior fluidity, the high-speed shearing may be performed under peripheral speed conditions that do not cause grinding of the solid electrolyte 101 particles, but do cause disintegration of the solid electrolyte 101 particles themselves. When grinding of the solid electrolyte 101 particles does not occur, the specific surface area of ​​the solid electrolyte 101 tends not to change significantly before and after the production of the solid electrolyte composition 1000. The solid electrolyte composition 1000 may also be manufactured by mixing the solvent 102 with a pre-prepared ion conductor 111, and then subjecting the resulting mixture to high-speed shearing.

[0143] The binder solution is, for example, a solution containing binder 103 and solvent 102. The composition of the solvent in the binder solution may be the same as or different from the composition of the solvent in the dispersion of solid electrolyte 101. The dispersant solution is, for example, a solution containing a dispersant and solvent 102. The composition of the solvent in the dispersant solution may be the same as or different from the composition of the solvent in the dispersion of solid electrolyte 101.

[0144] The solid content concentration of the solid electrolyte composition 1000 is appropriately determined according to the particle size of the solid electrolyte 101, the specific surface area of ​​the solid electrolyte 101, the type of solvent 102, and the type of binder 103. The solid content concentration may be 20% by mass or more and 70% by mass or less, or 30% by mass or more and 60% by mass or less. By setting the solid content concentration to 20% by mass or more, the viscosity of the solid electrolyte composition 1000 is increased, which suppresses dripping when the solid electrolyte composition 1000 is applied to a substrate such as an electrode. By setting the solid content concentration to 70% by mass or less, the wet film thickness when the solid electrolyte composition 1000 is applied to a substrate can be made relatively thicker, so that a solid electrolyte sheet with a more uniform film thickness can be manufactured.

[0145] (Embodiment 2) Embodiment 2 will be described below. Descriptions that overlap with Embodiment 1 will be omitted as appropriate.

[0146] The method for manufacturing a laminate comprising a solid electrolyte sheet and electrodes will be described below with reference to Figure 3. Figure 3 is a flowchart showing the method for manufacturing a laminate according to Embodiment 2.

[0147] The method for manufacturing the laminate may include steps S01, S02, and S03. Step S01 in Figure 3 is a kneading step for producing the solid electrolyte composition 1000, which is described in Embodiment 1. The method for manufacturing the laminate includes step S02 for applying the solid electrolyte composition 1000 in Embodiment 1 and step S03 for drying. Steps S01, S02, and S03 may be carried out in this order. From the above steps, a laminate 2000 having a good solid electrolyte sheet 201 with suppressed surface irregularities can be manufactured using the solid electrolyte composition 1000 in Embodiment 1.

[0148] Figure 4 is a cross-sectional view of the laminate 2000 according to Embodiment 2. The laminate 2000 can be manufactured by performing a step S02 in which a solid electrolyte composition 1000 is applied onto the electrode 202. This laminate 2000 can also be used as an electrode.

[0149] In step S02, the solid electrolyte composition 1000 is applied onto the electrode 202. This forms a coating film of the solid electrolyte composition 1000 on the electrode 202.

[0150] The electrode 202 may be a positive or negative electrode, or it may be a component obtained by coating a solid electrolyte on a positive or negative electrode. The positive or negative electrode may include, for example, a current collector and an active material layer disposed on the current collector. A laminate 2000 of the electrode 202 and the solid electrolyte sheet 201 is manufactured by coating the electrode 202 with a solid electrolyte composition 1000 and going through step S03 described later.

[0151] Coating methods include die coating, gravure coating, doctor blade coating, bar coating, spray coating, and electrostatic coating. From the standpoint of mass production, the die coating method may be used. The coating method may be continuous coating or intermittent coating.

[0152] With respect to the electrode 202, a pressing process may be performed before step S02, provided that the interfacial resistance between the active material layer and the current collector, and the interfacial resistance between the active material layer and the solid electrolyte layer, do not increase excessively. The pressing process can increase the packing density of the electrode 202. By increasing the packing density of the electrode 202, the penetration of the solvent into the electrode 202 in step S02 can be further suppressed, thereby enabling the production of a more uniform solid electrolyte sheet 201.

[0153] For electrode 202, the pressing process does not need to be performed before process S02. By omitting the pressing process, the interfacial resistance between the active material layer and the solid electrolyte layer can be further reduced, thereby improving the output characteristics of the battery.

[0154] In step S02, the wet film thickness is not particularly limited and may be, for example, 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, or 40 μm or less. The lower limit of the wet film thickness is not particularly limited and may be, for example, 1 μm.

[0155] In step S03, the solid electrolyte composition 1000 coated on the electrode 202 is dried. By drying the solid electrolyte composition 1000, for example, the solvent 102 is removed from the coated film of the solid electrolyte composition 1000, and a solid electrolyte sheet 201 is produced.

[0156] Methods for drying the solvent 102 from the solid electrolyte composition 1000 include hot air drying, infrared heating drying, reduced pressure drying, vacuum drying, high-frequency dielectric heating drying, and high-frequency induction heating drying. These methods may be used individually or in combination of two or more.

[0157] From the standpoint of manufacturing costs, solvent 102 may be removed from the solid electrolyte composition 1000 by hot air drying. The set temperature of the hot air may be 50°C to 250°C, or 80°C to 150°C.

[0158] The removal of solvent 102 can be confirmed, for example, by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), gas chromatography (GC), or gas chromatography-mass spectrometry (GC / MS). However, if the solid electrolyte sheet 201 retains ionic conductivity after drying, the solvent 102 does not necessarily need to be completely removed. That is, some of the solvent 102 may remain in the solid electrolyte sheet 201.

[0159] The ionic conductivity of the solid electrolyte sheet 201 may be 0.1 mS / cm or higher, or 1 mS / cm or higher. Adjusting the ionic conductivity to 0.1 mS / cm or higher may improve the output characteristics of the battery. The solid electrolyte sheet 201 may be subjected to pressure molding using a press or the like in order to improve its ionic conductivity.

[0160] (Embodiment 3) Embodiment 3 is described below. Descriptions that overlap with Embodiment 1 or Embodiment 2 will be omitted as appropriate.

[0161] Figure 5 is a cross-sectional view of the battery 3000 according to Embodiment 3.

[0162] The battery 3000 in Embodiment 3 comprises a positive electrode 301, a negative electrode 303, and an electrolyte layer 302.

[0163] The electrolyte layer 302 is located between the positive electrode 301 and the negative electrode 303.

[0164] The electrolyte layer 302 includes the solid electrolyte sheet 201 prepared in Embodiment 2.

[0165] The battery 3000 includes a good solid electrolyte sheet 201 in which the occurrence of surface irregularities is suppressed. The fact that the occurrence of surface irregularities is suppressed in the solid electrolyte sheet 201 means that the occurrence of defects in the solid electrolyte sheet 201 is suppressed. Therefore, even when using a thinner electrolyte layer 302, the possibility of contact (short circuit) between the positive electrode 301 and the negative electrode 303 can be reduced, thereby improving the energy density of the battery 3000.

[0166] The battery 3000 can be manufactured, for example, by combining the laminate 2000 in Embodiment 2 with an electrode having polarity opposite to that of the electrode 202 included in the laminate 2000. This method is superior to a transfer method in which a solid electrolyte sheet 201 formed on a substrate is transferred to the electrode in terms of reducing the number of parts. In other words, the above method is superior to the transfer method in terms of mass production. When electrode 202 is the positive electrode, the electrode having polarity opposite to that of electrode 202 is the negative electrode. When electrode 202 is the negative electrode, the electrode having polarity opposite to that of electrode 202 is the positive electrode. The positive or negative electrode includes, for example, a current collector and an active material layer disposed on the current collector. A layer containing a solid electrolyte may be provided on the active material layer of the positive electrode or on the active material layer of the negative electrode. Methods for combining electrodes having polarity opposite to that of electrode 202 include applying an electrode slurry onto the solid electrolyte sheet 201 of the laminate 2000, and bonding electrodes prepared by applying an additive to a current collector in advance and drying them to the laminate 2000.

[0167] A method for manufacturing the battery 3000 includes, for example, applying a solid electrolyte composition 1000 onto a first electrode to form a coating film, removing the solvent from the coating film to produce a solid electrolyte sheet 201, and arranging a second electrode on the solid electrolyte sheet 201. Methods for arranging the second electrode on the solid electrolyte sheet 201 include applying the second electrode composition onto the solid electrolyte sheet 201 and transferring the second electrode onto the solid electrolyte sheet 201. When the first electrode is the positive electrode, the second electrode is the negative electrode. When the first electrode is the negative electrode, the second electrode is the positive electrode. Each of the first and second electrodes includes, for example, a current collector and an active material layer arranged on the current collector. A layer containing a solid electrolyte may be provided on the active material layer of the first electrode or on the active material layer of the second electrode.

[0168] The electrolyte layer 302 is a layer containing an electrolyte material. Examples of the electrolyte material include solid electrolytes. That is, the electrolyte layer 302 may be a solid electrolyte layer. As the solid electrolyte contained in the electrolyte layer 302, the solid electrolyte exemplified as solid electrolyte 101 in Embodiment 1 may be used, for example, sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, polymer solid electrolytes, complex hydride solid electrolytes, etc. can be used.

[0169] The electrolyte layer 302 may contain a solid electrolyte as its main component. The electrolyte layer 302 may contain a solid electrolyte in an amount of 70% or more (70% by mass or more) of the total mass of the electrolyte layer 302.

[0170] With the above configuration, the output characteristics of the 3000 battery can be further improved.

[0171] The electrolyte layer 302 mainly contains a solid electrolyte and may also contain unavoidable impurities. Examples of unavoidable impurities include starting materials, by-products, and decomposition products used in the synthesis of the solid electrolyte.

[0172] The electrolyte layer 302 may contain 100% solid electrolyte by mass relative to the total electrolyte layer 302, excluding impurities that are unavoidable to be present.

[0173] With the above configuration, the output characteristics of the 3000 battery can be further improved.

[0174] The electrolyte layer 302 may contain two or more of the materials listed as solid electrolytes. For example, the electrolyte layer 302 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0175] The electrolyte layer 302 may be a layer made by laminating a layer using a solid electrolyte sheet 201 and a layer containing a solid electrolyte with a different composition from the solid electrolyte 101 contained in the solid electrolyte sheet 201. The electrolyte layer 302 may be a single layer made of the solid electrolyte sheet 201, or it may be two or more layers made of other solid electrolytes.

[0176] The electrolyte layer 302 is positioned between the layer using the solid electrolyte sheet 201 and the negative electrode 303, and may have a layer containing a solid electrolyte with a lower reduction potential than the solid electrolyte 101 contained in the solid electrolyte sheet 201. With the above configuration, the reductive decomposition of the solid electrolyte 101 that may occur due to contact between the solid electrolyte 101 and the negative electrode active material can be suppressed, thereby improving the output characteristics of the battery 3000. Examples of solid electrolytes with a lower reduction potential than the solid electrolyte 101 include sulfide solid electrolytes.

[0177] The thickness of the electrolyte layer 302 may be between 1 μm and 300 μm. When the thickness of the electrolyte layer 302 is 1 μm or more, the possibility of a short circuit between the positive electrode 301 and the negative electrode 303 is reduced. When the thickness of the electrolyte layer 302 is 300 μm or less, the battery 3000 can be easily operated at high power. In other words, if the thickness of the electrolyte layer 302 is appropriately adjusted, the safety of the battery 3000 can be sufficiently ensured, and the battery 3000 can be operated at high power.

[0178] The thickness of the solid electrolyte sheet 201 contained in the electrolyte layer 302 may be 1 μm or more and 30 μm or less, 1 μm or more and 15 μm or less, or 1 μm or more and 7.5 μm or less. When the thickness of the solid electrolyte sheet 201 is 1 μm or more, the possibility of a short circuit between the positive electrode 301 and the negative electrode 303 is reduced. When the thickness of the solid electrolyte sheet 201 is 30 μm or less, the internal resistance of the battery 3000 is reduced, enabling high-power operation and improving the energy density of the battery 3000. The thickness of the solid electrolyte sheet 201 is defined, for example, by the average value of any multiple points (e.g., 3 points) in a cross section parallel to the thickness direction.

[0179] The shape of the solid electrolyte contained in Battery 3000 is not particularly limited. The solid electrolyte may be needle-shaped, spherical, ellipsoidal, or the like. The solid electrolyte may also be particulate.

[0180] At least one selected from the group consisting of a positive electrode 301 and a negative electrode 303 may contain an electrolyte material, for example, a solid electrolyte. As the solid electrolyte, the solid electrolyte exemplified as the material constituting the solid electrolyte sheet 201 can be used. With the above configuration, the ion conductivity (e.g., lithium ion conductivity) inside the positive electrode 301 or the negative electrode 303 is improved, and the battery 3000 can be operated at high power.

[0181] In the positive electrode 301 or the negative electrode 303, a sulfide solid electrolyte may be used as the solid electrolyte, and the above-mentioned halide solid electrolyte may be used as the coating material for coating the active material.

[0182] The positive electrode 301 includes, for example, a material having the property of intercalating and releasing metal ions (e.g., lithium ions) as a positive electrode active material. Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(NiCoAl)O2, Li(NiCoMn)O2, and LiCoO2. When, for example, a lithium-containing transition metal oxide is used as the positive electrode active material, the manufacturing cost of the positive electrode 301 can be reduced, and the average discharge voltage of the battery 3000 can be improved. Li(NiCoAl)O2 means that Ni, Co, and Al are included in any ratio. Li(NiCoMn)O2 means that Ni, Co, and Mn are included in any ratio.

[0183] If the solid electrolyte contained in the positive electrode 301 is particulate (for example, spherical), the median diameter of the solid electrolyte may be 100 μm or less. When the median diameter of the solid electrolyte is 100 μm or less, the positive electrode active material and the solid electrolyte can be well dispersed in the positive electrode 301. This improves the charge and discharge characteristics of the battery 3000.

[0184] The median diameter of the solid electrolyte contained in the positive electrode 301 may be smaller than the median diameter of the positive electrode active material. This allows the solid electrolyte and the positive electrode active material to be well dispersed.

[0185] The median diameter of the positive electrode active material may be between 0.1 μm and 100 μm. When the median diameter of the positive electrode active material is 0.1 μm or more, the positive electrode active material and the solid electrolyte can be well dispersed in the positive electrode 301. As a result, the charge and discharge characteristics of the battery 3000 are improved. When the median diameter of the positive electrode active material is 100 μm or less, the lithium diffusion rate within the positive electrode active material is improved. Therefore, the battery 3000 can operate at high power.

[0186] In the positive electrode 301, the volume ratio "v1:100-v1" of the positive electrode active material to the solid electrolyte may satisfy the condition 30≦v1≦95. v1 represents the volume ratio of the positive electrode active material when the total volume of the positive electrode active material and solid electrolyte contained in the positive electrode 301 is set to 100. If 30≦v1 is satisfied, it is easier to ensure a sufficient energy density for the battery 3000. If v3≦95 is satisfied, it is easier to operate the battery 3000 at a high output.

[0187] The thickness of the positive electrode 301 may be between 10 μm and 500 μm. When the thickness of the positive electrode 301 is 10 μm or more, a sufficient energy density can be easily ensured for the battery 3000. When the thickness of the positive electrode 301 is 500 μm or less, the battery 3000 can be operated at a higher power output more easily.

[0188] The negative electrode 303 includes, for example, a material having the property of intercalating and releasing metal ions (e.g., lithium ions) as the negative electrode active material. Examples of negative electrode active materials include metallic materials, carbon materials, oxides, nitrides, tin compounds, and silicon compounds. The metallic material may be a pure metal or an alloy. Examples of metallic materials include lithium metal and lithium alloys. Examples of carbon materials include natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, and amorphous carbon. The capacity density of battery 3000 can be improved by using silicon (Si), tin (Sn), silicon compounds, and tin compounds. The safety of battery 3000 can be improved by using oxide compounds containing titanium (Ti) or niobium (Nb).

[0189] The median diameter of the negative electrode active material may be between 0.1 μm and 100 μm. When the median diameter of the negative electrode active material is 0.1 μm or greater, the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode 303. This improves the charge and discharge characteristics of the battery 3000. When the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion rate within the negative electrode active material improves. Therefore, the battery 3000 can operate at high power.

[0190] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte. This allows for good dispersion of the solid electrolyte and the negative electrode active material.

[0191] The volume ratio "v2:100-v2" of the negative electrode active material to the solid electrolyte contained in the negative electrode 303 may satisfy the condition 30≦v2≦95. v2 represents the volume ratio of the negative electrode active material when the total volume of the negative electrode active material and solid electrolyte contained in the negative electrode 303 is set to 100. If 30≦v2 is satisfied, it is easier to ensure a sufficient energy density for the battery 3000. If v2≦95 is satisfied, it is easier to operate the battery 3000 at high power.

[0192] The thickness of the negative electrode 303 may be between 10 μm and 500 μm. When the thickness of the negative electrode 303 is 10 μm or more, a sufficient energy density can be easily ensured for the battery 3000. When the thickness of the negative electrode 303 is 500 μm or less, the battery 3000 can be operated at a higher power output more easily.

[0193] The positive electrode active material and the negative electrode active material may be coated with a coating material to reduce the interfacial resistance between each active material and the solid electrolyte. Materials with low electronic conductivity may be used as the coating material. Examples of coating materials include oxide materials and oxide solid electrolytes.

[0194] Oxide materials used for coatings include SiO2, Al2O3, TiO2, B2O3, Nb2O5, WO3, and ZrO2.

[0195] Examples of oxide solid electrolytes used in coating materials include Li-Nb-O compounds such as LiNbO3, Li-BO compounds such as LiBO2 and Li3BO3, Li-Al-O compounds such as LiAlO2, Li-Si-O compounds such as Li4SiO4, Li2SO4, and Li4Ti5O 12Examples include Li-Ti-O compounds such as Li2ZrO3, Li-Zr-O compounds such as Li2MoO3, Li-Mo-O compounds such as LiV2O5, Li-WO compounds such as Li2WO4, and Li-PO compounds such as LiPO4. Oxide solid electrolytes have high ionic conductivity and high potential stability. Therefore, by using oxide solid electrolytes as coating materials, the charge and discharge efficiency of the 3000 battery can be further improved.

[0196] At least one selected from the group consisting of the positive electrode 301, the electrolyte layer 302, and the negative electrode 303 may contain a binder for the purpose of improving the adhesion between particles. Examples of binders include those described above for the binder 103. When the binder contains an elastomer, each layer of the positive electrode 301, electrolyte layer 302, and negative electrode 303 contained in the battery 3000 tends to have excellent flexibility and elasticity. In this case, the durability of the battery 3000 tends to improve.

[0197] At least one selected from the group consisting of the positive electrode 301, the electrolyte layer 302, and the negative electrode 303 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery 3000.

[0198] The non-aqueous electrolyte solution comprises a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, cyclic carbonate solvents, chain carbonate solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, fluorine-containing solvents, and the like may be used. Examples of the cyclic carbonate solvent include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Examples of the chain carbonate solvent include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and the like. Examples of the cyclic ether solvent include tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane and the like. Examples of the chain ether solvent include 1,2-dimethoxyethane, 1,2-diethoxyethane and the like. Examples of the cyclic ester solvent include γ-butyrolactone and the like. Examples of the chain ester solvent include methyl acetate and the like. Examples of the fluorine-containing solvent include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, fluorodimethylene carbonate and the like. As the non-aqueous solvent, one type of non-aqueous solvent selected from the above may be used alone, or a mixture of two or more types of non-aqueous solvents selected from the above may be used.

[0199] The non-aqueous electrolyte solution may contain at least one fluorine-containing solvent selected from the group consisting of fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate and fluorodimethylene carbonate.

[0200] Examples of the lithium salt include LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, LiSO₃CF₃, LiN(SO₂F)₂, LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiN(SO₂CF₃)(SO₂C₄F₉), LiC(SO₂CF₃)₃ and the like. As the lithium salt, one type of lithium salt selected from the above may be used alone, or a mixture of two or more types of lithium salts selected from the above may be used. The concentration of the lithium salt in the non-aqueous electrolyte solution may be 0.5 mol / L or more and 2 mol / L or less.

[0201] As the gel electrolyte, a material obtained by impregnating a polymer material with a non-aqueous electrolyte can be used. Examples of the polymer material include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and polymers having an ethylene oxide bond.

[0202] The cations constituting the ionic liquid may be aliphatic chain quaternary cations such as tetraalkylammonium and tetraalkylphosphonium; aliphatic cyclic ammoniums such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium and piperidinium; nitrogen-containing heterocyclic aromatic cations such as pyridinium and imidazolium. The anions constituting the ionic liquid are PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2F)2 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , C(SO2CF3)3 - and the like. The ionic liquid may contain a lithium salt.

[0203] At least one selected from the group consisting of the positive electrode 301 and the negative electrode 303 may contain a conductive aid for the purpose of improving electronic conductivity. Examples of the conductive aid include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black and Ketjen black, conductive fibers such as carbon fiber and metal fiber, conductive powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyaniline, polypyrrole and polythiophene. Cost reduction can be achieved when a carbon material is used as the conductive aid.

[0204] The shapes of the 3000 battery include coin-type, cylindrical, rectangular, sheet-type, button-type, flat, and stacked types. [Examples]

[0205] The details of this disclosure will be explained below using examples and comparative examples. However, the solid electrolyte compositions, laminates comprising solid electrolyte sheets and electrodes, and batteries of this disclosure are not limited to the following examples.

[0206] <Example 1-1> [solvent] In all of the following steps, commercially available dehydrating solvents or solvents dehydrated by nitrogen bubbling were used as the solvent. The water content in the solvent was 10 ppm by mass or less.

[0207] [Preparation of binder solution] A binder solution was prepared by adding a solvent to the binder and dissolving or dispersing the binder in the solvent. The binder concentration in the binder solution was adjusted to between 5% by mass and 10% by mass. Next, the binder solution was dehydrated by nitrogen bubbling until the water content reached 10 ppm by mass or less.

[0208] In Example 1-1, tetralin was used as the solvent for the binder solution. Styrene-ethylene / butylene-styrene block copolymer (SEBS), a hydrogenated styrene-based thermoplastic elastomer, was used as the binder. The content of repeating units derived from styrene in SEBS was 32% by mass. The weight-average molecular weight of SEBS was M w The number was 230,000.

[0209] [Preparation of dispersant solution] The dispersant was dehydrated by adding molecular sieve 4A 1 / 16. A dispersant solution was prepared by adding the previously dehydrated solvent to the dehydrated dispersant. The concentration of the dispersant in the dispersant solution was adjusted to 5% by mass.

[0210] In Example 1-1, tetralin was used as the solvent for the dispersant solution. DISPERBYK-109 (manufactured by Bic Chemie Japan, main component 1-hydroxyethyl-2-alkenylimidazoline, amine value 140 mg KOH / g) was used as the dispersant.

[0211] [Preparation of solid electrolyte compositions] In an argon glove box with a dew point of -60°C or lower, tetralin, a dispersant solution, and a binder solution were added to Li2S-P2S5 glass ceramics (hereinafter referred to as "LPS"). These materials were mixed in a mass ratio of LPS:binder:dispersant = 100:1:0.25. Next, the resulting mixture was dispersed and kneaded by shearing using an in-line dispersion and grinding machine (manufactured by IKA Corporation, magic LAB). This yielded the solid electrolyte composition of Example 1-1. The solid content concentration of the solid electrolyte composition was 51% by mass.

[0212] [Specific surface area S α and S β [Measurement] First, the specific surface area S α and S β A sample was prepared for measurement to determine the specific surface area S. α LPS, a raw material for solid electrolyte compositions, was used as the sample for measurement. Specific surface area S β The sample for measuring was prepared by the following method. First, the solid electrolyte composition of Example 1-1 was dried in an argon glove box with a dew point of -60°C or lower. The drying of the solid electrolyte composition was carried out by heating at 100°C for 1 hour under a vacuum atmosphere. This removed the solvent from the solid electrolyte composition and yielded a solid. This solid was thoroughly loosened by hand and then heated again at 100°C for 1 hour under a vacuum atmosphere. This allowed the specific surface area S to be measured. β An ion conductor was obtained as a sample for measurement.

[0213] Next, using these measurement samples, the specific surface area S α and S βThe specific surface area was measured. A high-precision gas adsorption analyzer (MicrotracBEL, BELSORP MINI X) was used for the measurement. Before measurement, the sample was dried by vacuum heating at 80°C for approximately 1 hour inside the sample tube. For the measurement of specific surface area, the amount of nitrogen adsorbed by the sample was first measured using the nitrogen gas adsorption method. The amount of nitrogen adsorption was measured at approximately 10 points with relative pressures in the range of 0.05 to 0.30. Based on the obtained data, the specific surface area S was determined by the BET analysis method. α and S β The result was calculated.

[0214] In the solid electrolyte composition of Example 1-1, the specific surface area S of the solid electrolyte α The specific surface area S of the ion conductor relative to the ion conductor. β Ratio S β / S α The ratio was 0.77. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0215] <Examples 1-2> The solid electrolyte composition of Example 1-2 was prepared in the same manner as in Example 1-1, except that the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:2:0.25. In the solid electrolyte composition of Example 1-2, the ratio S β / S α The ratio was 0.72. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0216] <Examples 1-3> A solid electrolyte composition of Example 1-3 was produced by the same method as in Example 1-1, except that the solid content concentration of the solid electrolyte composition was adjusted to 45% by mass, no dispersant was used, the materials were mixed at a mass ratio of LPS:binder=100:3, and the mixed liquid was dispersed and kneaded by shearing using a homogenizer (manufactured by As One Corporation, HG-200) and a generator (manufactured by As One Corporation, K-20S). In the solid electrolyte composition of Example 1-3, the ratio S β / S α was 0.70. The solid electrolyte was the sulfide solid electrolyte LPS. The solvent was tetralin. The binder was SEBS.

[0217] <Example 1-4> A solid electrolyte composition of Example 1-4 was produced by the same method as in Example 1-3, except that modified styrene-butylene rubber (modified SBR) was used as the binder. In the solid electrolyte composition of Example 1-4, the ratio S β / S α was 0.66. The solid electrolyte was the sulfide solid electrolyte LPS. The solvent was tetralin. The binder was modified SBR.

[0218] <Example 1-5> A solid electrolyte composition of Example 1-5 was produced by the same method as in Example 1-1, except that when producing the solid electrolyte composition, the materials were mixed at a mass ratio of LPS:binder:dispersant=100:3:0.25. In the solid electrolyte composition of Example 1-5, the ratio S β / S α was 0.64. The solid electrolyte was the sulfide solid electrolyte LPS. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0219] <Example 1-6> The solid electrolyte composition of Example 1-6 was prepared in the same manner as in Example 1-1, except that modified SBR was used as the binder, the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:3:0.25, and the mixture was dispersed and kneaded by shearing using a homogenizer (AS ONE, HG-200) and a generator (AS ONE, K-20S). In the solid electrolyte composition of Example 1-6, specific S β / S α The ratio was 0.63. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was tetralin. The binder was modified SBR. The dispersant was DISPERBYK-109.

[0220] <Examples 1-7> The solid electrolyte composition of Example 1-7 was prepared in the same manner as in Example 1-3, except that the solid content concentration of the solid electrolyte composition was adjusted to 49% by mass, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:5:0.25. In the solid electrolyte composition of Example 1-7, the ratio S β / S α The ratio was 0.50. The solid electrolyte was LPS sulfide solid electrolyte. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0221] <Examples 1-8> The solid electrolyte composition of Example 1-8 was prepared in the same manner as in Example 1-3, except that the solid content concentration of the solid electrolyte composition was adjusted to 41% by mass, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:8:0.25. In the solid electrolyte composition of Example 1-8, specific S β / S α The ratio was 0.42. The solid electrolyte was LPS sulfide solid electrolyte. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0222] <Comparative Example 1-1> The solid electrolyte composition of Comparative Example 1-1 was prepared by the same method as in Example 1-6, except that polyvinylidene fluoride (PVDF) was used as the binder. In the solid electrolyte composition of Comparative Example 1-1, the specific S β / S α The ratio was 1.00. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was tetralin. The binder was PVDF. The dispersant was DISPERBYK-109.

[0223] <Comparative Example 1-2> The solid electrolyte composition of Comparative Example 1-2 was prepared in the same manner as in Comparative Example 1-1, except that the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:5:0.25. In the solid electrolyte composition of Comparative Example 1-2, the ratio S β / S α The ratio was 1.06. The solid electrolyte was LPS sulfide solid electrolyte. The solvent was tetralin. The binder was PVDF. The dispersant was DISPERBYK-109.

[0224] <Comparative Example 1-3> The solid electrolyte compositions of Comparative Examples 1-3 were prepared in the same manner as in Examples 1-4, except that diisobutyl ketone was used as the solvent, the solid content concentration of the solid electrolyte composition was adjusted to 57% by mass, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:0.5:0.25. In the solid electrolyte compositions of Comparative Examples 1-3, the ratio S β / S α The ratio was 0.80. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was diisobutyl ketone. The binder was modified SBR. The dispersant was DISPERBYK-109.

[0225] <Comparative Example 1-4> The solid electrolyte compositions of Comparative Example 1-4 were prepared in the same manner as in Example 1-8, except that the solid content concentration of the solid electrolyte composition was adjusted to 37% by mass, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:12:0.25. In the solid electrolyte composition of Comparative Example 1-4, the ratio S β / S α The ratio was 0.35. The solid electrolyte was LPS sulfide solid electrolyte. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0226] <Comparative Example 1-5> The solid electrolyte compositions of Comparative Examples 1-5 were prepared in the same manner as in Examples 1-8, except that the solid content concentration of the solid electrolyte composition was adjusted to 37% by mass, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:15:0.25. In the solid electrolyte compositions of Comparative Examples 1-5, the ratio S β / S α The ratio was 0.28. The solid electrolyte was sulfide solid electrolyte LPS. The solvent was tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0227] <Comparative Example 1-6> The solid electrolyte compositions of Comparative Examples 1-6 were prepared in the same manner as those of Comparative Examples 1-5, except that mixed xylene was used as the solvent for the binder solution, and the materials were mixed in a mass ratio of LPS:binder:dispersant = 100:20:0.25. In the solid electrolyte compositions of Comparative Examples 1-6, the mixed xylene was a mixed solvent containing o-xylene, m-xylene, p-xylene, and ethylbenzene in a mass ratio of 24:42:18:16. β / S α The ratio was 0.19. The solid electrolyte was a sulfide solid electrolyte LPS. The solvent was a mixed solvent of xylene and tetralin. The binder was SEBS. The dispersant was DISPERBYK-109.

[0228] <Reference example 1-1> The solid electrolyte composition of Reference Example 1-1 was prepared by the same method as in Examples 1-3, except that a binder and dispersant were not used. In the solid electrolyte composition of Reference Example 1-1, the specific S β / S α The value was 1.00. The solid electrolyte was a sulfide solid electrolyte LPS.

[0229] <Reference example 1-2> The solid electrolyte composition of Reference Example 1-2 was prepared by the same method as in Examples 1-6, except that a binder was not used. In the solid electrolyte composition of Reference Example 1-2, the specific S β / S α The value was 0.97. The solid electrolyte was sulfide solid electrolyte LPS. The dispersant was DISPERBYK-109.

[0230] <Evaluation of Solid Electrolyte Compositions> [Measurement of solvent retention rate] The solvent retention rate was measured for the solid electrolyte compositions of Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-6, and Reference Examples 1-1 to 1-2 using the method described above. The solvent retention rate was measured in a dry room with a dew point of -40°C or lower. As the electrode, a negative electrode was used, formed by coating a composite material consisting of graphite, LPS, modified SBR, ethylcellulose, and a dispersant onto a roughened nickel foil. In the composite material, each material was composed in a mass ratio of graphite:LPS:modified SBR:ethylcellulose:dispersant = 70:30:1:0.25:0.05. The thickness of the roughened nickel foil was 12 μm. The thickness of the negative electrode was 110 μm. The packing density of the negative electrode was 55%.

[0231] [Measurement of the maintenance rate of ionic conductivity] The ionic conductivity retention rate was measured for the ionic conductors contained in the solid electrolyte compositions of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-6, as well as for the solid electrolytes contained in the solid electrolyte compositions of Reference Examples 1-1 to 1-2, using the following method. First, the specific surface area S βAn ion conductor or solid electrolyte was obtained from the solid electrolyte composition using the method described above. Next, 100 mg of the ion conductor or solid electrolyte was placed in an insulating outer cylinder and compressed and molded at a pressure of 740 MPa. Stainless steel pins were then placed above and below the compressed ion conductor or solid electrolyte. Current collector leads were attached to the stainless steel pins. Next, the inside of the insulating outer cylinder was isolated and sealed from the outside atmosphere using an insulating ferrule. Finally, the resulting cell was restrained from above and below using four bolts, and a surface pressure of 150 MPa was applied to the ion conductor or solid electrolyte to prepare a sample for measuring ionic conductivity. This sample was placed in a constant temperature bath at 25°C. The ionic conductivity of each sample was determined by electrochemical AC impedance method using a potentiostat / galvanostat (Solartron Analytical, 1470E) and a frequency response analyzer (Solartron Analytical, 1255B). Based on the obtained results, the ratio of the ionic conductivity of the ion conductor or solid electrolyte to the ionic conductivity of LPS, which is a raw material for the solid electrolyte composition, was calculated. This allowed us to determine the retention rate of ionic conductivity for the ion conductors contained in the solid electrolyte compositions of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-6, as well as for the solid electrolytes contained in the solid electrolyte compositions of Reference Examples 1-1 to 1-2.

[0232] The results of the above measurements are shown in Table 1.

[0233] [Table 1]

[0234] As can be seen from Table 1, ratio S β / S α In the solid electrolyte compositions of the examples, where the specific surface area S was greater than 0.40 and less than 0.80, unlike the solid electrolyte compositions of the comparative examples, both high solvent retention and high ionic conductivity retention were achieved. Note that in Reference Examples 1-1 and 1-2, the specific surface area S α This refers to the specific surface area of ​​the solid electrolyte raw material. Specific surface area Sβ This refers to the specific surface area of ​​the solid electrolyte after the preparation of the solid electrolyte composition. As can be seen from Table 1, in Reference Examples 1-1 and 1-2, the specific S β / S α The ratio was approximately 1. In other words, in Reference Examples 1-1 and 1-2, the specific surface area of ​​the solid electrolyte hardly changed during the manufacturing process of the solid electrolyte composition. From this result, it can be inferred that in the solid electrolyte compositions of the Examples and Comparative Examples, there was hardly any change in the specific surface area of ​​the solid electrolyte due to excessive pulverization, sintering, etc., during the manufacturing process.

[0235] <Example 2-1> [Fabrication of a laminate comprising a solid electrolyte sheet and electrodes] In an argon glove box with a dew point of -60°C or lower, the solid electrolyte composition of Example 1-1 was applied to the negative electrode using a die coater to create a coated film. The negative electrode contained graphite, silicon, LPS, and modified SBR. No prior pressing process was performed on the negative electrode. In the application of the solid electrolyte composition, three films with different wet film thicknesses were created by intermittent coating with a coating width of 98 mm and a length of 150 mm. The wet film thicknesses of the three films were 60 μm, 50 μm, and 40 μm, respectively. The laminate of Example 2-1 was prepared by drying the obtained coated films with hot air at a temperature between 80°C and 110°C.

[0236] <Example 2-2> The laminate of Example 2-2 was prepared by the same method as in Example 2-1, except that the solid electrolyte composition of Example 1-2 was used as the solid electrolyte composition.

[0237] <Example 2-3> The laminate of Example 2-3 was prepared by the same method as in Example 2-1, except that the solid electrolyte composition of Example 1-5 was used as the solid electrolyte composition.

[0238] <Comparative Example 2-1> The laminate of Comparative Example 2-1 was prepared by the same method as in Example 2-1, except that the solid electrolyte composition of Comparative Example 1-3 was used as the solid electrolyte composition.

[0239] <Evaluation of laminates> The solid electrolyte sheets of the laminates from Examples 2-1 to 2-3 and Comparative Example 2-1 were visually inspected. The results are shown in Table 2. In Table 2, "Good" means that the solid electrolyte sheet was free of streaks and the results were good. "Poor" means that the solid electrolyte sheet had streaks and the results were poor.

[0240] [Table 2]

[0241] As shown in Table 2, for the laminates of Examples 2-1 to 2-3, the solid electrolyte sheets fabricated under the condition of a wet film thickness of 60 μm showed suppressed surface irregularities, indicating favorable results. The weight per unit area of ​​these solid electrolyte sheets was 4.1 mg / cm². 2 The thickness of these solid electrolyte sheets after compression treatment was 21 μm. On the other hand, in the case of the laminate of Comparative Example 2-1, the solid electrolyte sheet produced under the condition of a wet film thickness of 60 μm showed unevenness and the results were unsatisfactory.

[0242] In Comparative Example 2-1, ratio S β / S α Comparative Examples 1-3 used solid electrolyte compositions with a large coefficient of change. These solid electrolyte compositions had low solvent retention, making it difficult to produce a good coating film. This is presumed to have caused unevenness in the solid electrolyte sheet in the laminate of Comparative Example 2-1.

[0243] As shown in Table 2, for the laminates of Examples 2-2 and 2-3, the solid electrolyte sheet coated under the condition of a wet film thickness of 50 μm showed suppressed surface irregularities, indicating good results. The weight per unit area of ​​these solid electrolyte sheets was 3.3 mg / cm².2 The thickness of these solid electrolyte sheets after compression treatment was 17 μm.

[0244] As shown in Table 2, for the laminates of Examples 2-3, the solid electrolyte sheet coated under the condition of a wet film thickness of 40 μm showed suppressed surface irregularities, indicating good results. The weight per unit area of ​​this solid electrolyte sheet was 2.7 mg / cm². 2 The thickness of this solid electrolyte sheet after compression treatment was 14 μm.

[0245] As can be seen from Tables 1 and 2, ratio S β / S α According to the solid electrolyte composition of the example, where the ratio was greater than 0.40 and less than 0.80, it was possible to produce a solid electrolyte sheet in which the decrease in ionic conductivity was suppressed while the occurrence of defects such as unevenness was suppressed. Thus, the solid electrolyte composition of the example was suitable for the wet-on-dry method. [Industrial applicability]

[0246] The solid electrolyte compositions of this disclosure can be used, for example, in the manufacture of all-solid-state lithium-ion secondary batteries. [Explanation of symbols]

[0247] 101 Solid electrolyte 102 Solvent 103 Binder 111 Ionic conductors 201 Solid Electrolyte Sheet 202 Electrode 301 Positive electrode 302 Electrolyte layer 303 Negative electrode 1000 solid electrolyte composition 2000 Laminate 3000 batteries

Claims

1. Solvent and, An ion conductor comprising a solid electrolyte and a binder, and dispersed in the solvent, Includes, The specific surface area of ​​the solid electrolyte is S α It is expressed as such, and the specific surface area of ​​the ion conductor is S β When expressed as, 0.45 < S β / S α < 0.70 is satisfied, Solid electrolyte composition.

2. The binder includes an elastomer. The solid electrolyte composition according to claim 1.

3. The elastomer contains repeating units derived from styrene, The solid electrolyte composition according to claim 2.

4. The solvent includes aromatic hydrocarbons. The solid electrolyte composition according to claim 1.

5. The solvent contains tetralin, The solid electrolyte composition according to claim 4.

6. Further containing a dispersant, The solid electrolyte composition according to claim 1.

7. The dispersant comprises an amine compound. The solid electrolyte composition according to claim 6.

8. The dispersant comprises imidazoline or an imidazoline derivative. The solid electrolyte composition according to claim 7.

9. A method for manufacturing a laminate comprising a solid electrolyte sheet and an electrode, The aforementioned manufacturing method is Applying the solid electrolyte composition according to any one of claims 1 to 8 onto an electrode to form a coating film, The solvent is removed from the coated film to produce a solid electrolyte sheet, including, A method for manufacturing laminates.

10. The solid electrolyte composition according to any one of claims 1 to 8 is applied to the first electrode to form a coating film, The solvent is removed from the coated film to produce a solid electrolyte sheet, The second electrode is placed on the solid electrolyte sheet, including, Battery manufacturing method.

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