Solid electrolyte, electrode, and solid electrolyte battery

Abstract

To provide a solid electrolyte, an electrode, and a solid electrolyte battery having superior resistance to humidity.SOLUTION: This solid electrolyte has a coating layer attached to its surface, wherein the coating layer contains polyparaxylylene or diamond-like carbon.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte, an electrode, and a solid electrolyte battery. [Background technology]

[0002] In recent years, electronics technology has made remarkable advances, with efforts being made to make portable electronic devices smaller, lighter, thinner, and more multifunctional. There is also a strong demand for batteries, which serve as the power source for electronic devices, to be smaller, lighter, thinner, and more reliable. For this reason, solid electrolyte batteries, which use a solid electrolyte as the electrolyte, have attracted attention. Known solid electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, and complex hydride-based solid electrolytes (such as LiBH4).

[0003] Solid electrolytes have a problem in that they react with moisture in the air, resulting in a decrease in ionic conductivity. For example, Patent Document 1 discloses the use of a solid electrolyte containing a crosslinked polymer of a cyclic compound having a siloxane bond. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 017525 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need to study configurations that can improve the moisture resistance of solid electrolytes, in addition to the configuration disclosed in Patent Document 1.

[0006] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a solid electrolyte, an electrode, and a solid electrolyte battery that are excellent in moisture resistance. [Means for solving the problem]

[0007] The solid electrolyte according to the first aspect has a coating layer attached to the surface, and the coating layer contains polyparaxylylene or diamond-like carbon.

[0008] In the solid electrolyte according to the above aspect, the coating layer may have a thickness of 1 nm or more and 1000 nm or less.

[0009] In the solid electrolyte according to the above aspect, the polyparaxylylene may be one or more selected from the group consisting of polyparaxylylene, poly2-chloroparaxylylene, poly2,5-dichloroparaxylylene, and polydifluoroparaxylylene.

[0010] In the solid electrolyte according to the above embodiment, the contact angle of water is 70° or more and 105° or less.

[0011] In the solid electrolyte according to the above embodiment, the Rockwell hardness is R80 or more and R122 or less, or the Vickers hardness is 700 or more and 1900 or less.

[0012] The solid electrolyte according to the above embodiment may contain a compound represented by the following formula (1): A a E b G c X d ···(1) In formula (1), A is at least one element selected from the group consisting of Li, Cs, Ca, Rb, Sr, and Ba; E is at least one element selected from the group consisting of Mg, Al, Sc, Y, Nb, Zr, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Ta, W, and lanthanoids; and G is O, OH, BO2, BO3, BO4, BO6, BO7, CO3, NO3, AlO2, SiO3, SiO4, SiO7, SiO9, SiO 11 , SiO 18 , PO3, PO4, P2O7, P3O 10, SO3, SO4, SO5, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, BF4, PF6, B((COO)2), (COO)2, N, AlCl4, CF3SO3, CH3COO, CF3COO, OOC-(CH2)2-COO, OOC-CH2-COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH2-COO, C6H5SO3, OOC-CH=CH-COO (maleate), OOC-CH=CH-COO (fumarate), C(OH)(CH2COOH)2COO, AsO4, BiO4, CrO4, MnO4, PtF6, PtCl6, PtBr6, PtI6, SbO4, SeO4, TeO4, HCOO, SCN, NH2, CH3O, CH3CH2O, O-(CH2)-O (ethylene glycolate), O-CH2-CH(OH)-CH2-O (glycerolate), OOCCH2COO (malonate), ethylenediamine tetraacetate, citrate, nitrilotriacetate, penicillamineate, dimercapto - l ate, cyclopentadienyl, and is at least one group selected from the group consisting of; X is at least one element selected from the group consisting of F, Cl, Br, I; a satisfies 0.5 ≦ a < 6; b satisfies 0 < b < 2; c satisfies 0 ≦ c ≦ 6.0; d satisfies 0 < d ≦ 6.1.

[0013] In formula (1) of the solid electrolyte according to the above aspect, E may contain Zr.

[0014] The electrode according to the fourth aspect includes the solid electrolyte according to the above aspect.

[0015] The solid electrolyte battery according to the fifth aspect includes the solid electrolyte according to the above aspect.

Advantages of the Invention

[0016] The solid electrolyte according to the present embodiment is excellent in moisture resistance.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic cross-sectional view of the solid electrolyte battery according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0019] "Solid electrolyte" A solid electrolyte is a material that can move ions when an external electric field is applied. Solid electrolytes can be used as a component of the solid electrolyte layer or electrodes of solid electrolyte batteries.

[0020] The solid electrolyte according to this embodiment has a coating layer on its surface. The coating layer may cover at least a part of the surface of the solid electrolyte.

[0021] The coating layer contains polyparaxylylene or diamond-like carbon. The polyparaxylylene is, for example, one or more selected from the group consisting of polyparaxylylene, poly2-chloroparaxylylene, poly2,5-dichloroparaxylylene, and polydifluoroparaxylylene. The polyparaxylylene is particularly preferably polydifluoroparaxylylene. The diamond-like carbon is a compound having a diamond bond (sp 3 ) and graphite bonds (sp 2 ) is an amorphous carbon layer having both.

[0022] The thickness of the coating layer is, for example, 1 nm to 1000 nm, preferably 5 nm to 900 nm, and more preferably 10 nm to 800 nm. The thickness of the coating layer can be measured from a cross-sectional image taken using a transmission electron microscope. The thickness of the coating layer is calculated as the average value of the thicknesses measured at any five points.

[0023] The solid electrolyte may be in the form of a powder (particles) or a sintered body obtained by sintering the powder. The solid electrolyte may also be a compact obtained by compressing the powder, a compact obtained by molding a mixture of the powder and a binder, or a coating formed by applying a coating containing the powder, a binder, and a solvent and then heating to remove the solvent. The main structure of the solid electrolyte may be amorphous or crystalline.

[0024] The solid electrolyte to be coated with the coating layer is not particularly limited, and examples of the solid electrolyte include oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, and complex hydride-based solid electrolytes.

[0025] The solid electrolyte is preferably a halide-based solid electrolyte, and A a E b G c X d It is more preferable that the solid electrolyte contains a compound represented by (1). In addition to the above compounds, the solid electrolyte may contain unavoidable impurities, materials derived from the raw materials, etc. If the solid electrolyte is a halide-based solid electrolyte, it has good compatibility with polyparaxylylene or diamond-like carbon. This can be explained by the HSAB (Hard and Soft Acid and Base) rule.

[0026] The HSAB rule is explained below. The HSAB rule states that hard acids and hard bases tend to bond, while soft acids and soft bases tend to bond. Hard acids and hard bases have small ionic radii, while soft acids and soft bases have large ionic radii.

[0027] In the halide-based solid electrolyte represented by the above formula (1), E is a hard acid with a relatively small ionic radius. Therefore, this E is likely to bond with a hard base. For example, when E is Zr 4+ In the case of Zr, a complex called zirconocene dichloride is known. 4+It has a structure in which cyclopentadienyl is sandwiched from above and below. Cyclopentadienyl has many π electrons and is a hard base. These π electrons are 4+ It is thought that the molecules are attracted to the large positive charge of the tetravalent cation of the cation. The skeleton of polyparaxylylene is an aromatic xylene. Like the aromatic cyclopentadienyl, the aromatic xylene also has many π electrons and is considered to be a hard base. These π electrons are also 4+ It is believed that the halide-based solid electrolyte and polyparaxylylene are strongly attracted to each other by the large positive charge of 4. Therefore, it is believed that the halide-based solid electrolyte and polyparaxylylene are easily compatible and adhere strongly to each other.

[0028] Diamond-like carbon is sp 3 and sp 2 It is a mixture of sp 3 and sp 2 The properties vary depending on the ratio of sp 2 When the number of π electrons increases, the properties become similar to those of graphite, and it is considered to be a hard base with many π electrons. 4+ It is believed that the electrons are attracted to the large positive charge of the halide-based solid electrolyte, which is tetravalent. Therefore, it is believed that the halide-based solid electrolyte and the diamond-like carbon are easily compatible with each other and adhere strongly to each other.

[0029] In formula (1), A is at least one element selected from the group consisting of Li, Cs, Ca, Rb, Sr, and Ba; E is at least one element selected from the group consisting of Mg, Al, Sc, Y, Nb, Zr, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Ta, W, and lanthanoids; and G is O, OH, BO2, BO3, BO4, BO6, BO7, CO3, NO3, AlO2, SiO3, SiO4, SiO7, SiO9, SiO 11 , SiO 18 , PO3, PO4, P2O7, P3O 10, SO3, SO4, SO5, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, BF4, PF6, B((COO)2), (COO)2, N, AlCl4, CF3SO3, CH3COO, CF3COO, OOC-(CH2)2-COO, OOC-CH2-COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH2-COO, C6H5SO3, OOC-CH=CH-COO (maleate), OOC-CH=CH-COO (fumarate), C(OH)(CH2COOH)2COO, AsO4, BiO4, CrO4, MnO4, PtF6, PtCl6, PtBr, PtI6, SbO4, SeO4, TeO4, HCOO, SCN, NH2, CH3O, CH3CH2O, O-(CH2)-O (ethylene glycolate), O-CH2-CH(OH)-CH2-O (glycerolate), OOCCH2COO (malonate), ethylenediamine tetraacetate, citrate, nitrilotriacetate, penicillamineate, dimercapto - urate, cyclopentadienyl, and is at least one group selected from the group consisting of X is at least one element selected from the group consisting of F, Cl, Br, I, a satisfies 0.5 ≦ a < 6, b satisfies 0 < b < 2, c satisfies 0 ≦ c < 6.0, and d satisfies 0 ≦ d ≦ 6.1.

[0030] In formula (1), A is at least one element selected from the group consisting of Li and Cs, Ca, Rb, Sr, Ba. It is preferable that A contains only Li or a part of Li is substituted with at least one selected from the group consisting of Cs, Ca, Rb, Sr, Ba. When a part of Li is substituted with Cs, Ca, Rb, Sr, Ba, the potential window on the reduction side of the solid electrolyte becomes wider.

[0031] For example, when A contains Li and Ba, the ratio of Li to Ba is preferably 0.001 or more and 0.06 or less, more preferably 0.015 or more and 0.036 or less, in terms of molar ratio (Ba / (Li + Ba)). Also, for example, when A contains Li and Cs, the ratio of Li to Cs is preferably 0.005 or more and 0.10 or less, more preferably 0.01 or more and 0.04 or less, in terms of molar ratio (Cs / (Li + Cs)). When the solid electrolyte satisfies these relationships, the potential window on the reduction side of the solid electrolyte becomes wider.

[0032] In formula (1), a satisfies 0.5 ≤ a < 6, preferably satisfies 2.0 ≤ a ≤ 4.0, and more preferably satisfies 2.5 ≤ a ≤ 3.5. In the compound represented by formula (1), if a is 0.5 ≤ a < 6, the content of Li contained in the compound becomes appropriate and the ionic conductivity of the solid electrolyte increases.

[0033] In formula (1), E is at least one element selected from the group consisting of Mg, Al, Sc, Y, Nb, Zr, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Ta, W, and lanthanoids. E is an element that forms the skeleton of the halide-based solid electrolyte represented by formula (1). The lanthanoids are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. The solid electrolyte containing E has a wide potential window and high ionic conductivity. More preferably, E is any one of Al, Sc, Y, Zr, Hf, La, even more preferably Al or Zr, and particularly preferably contains Zr.

[0034] In formula (1), b is 0 < b < 2. Since the effect of containing E can be obtained more effectively, b is preferably 0.6 ≤ b. Also, when b ≤ 1, the density of the solid electrolyte becomes low and it becomes easier to secure a path for ion conduction.

[0035] In formula (1), G is O, OH, BO2, BO3, BO4, B3O6, B4O7, CO3, NO3, AlO2, SiO3, SiO4, Si2O7, Si3O9, Si4O 11 , SiO 18 , PO3, PO4, P2O7, P3O 10 , SO3, SO4, SO5, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, BF4, PF6, B((COO)2), (COO)2, N, AlCl4, CF3SO3, CH3COO, CF3COO, OOC-(CH2)2-COO, OOC-CH2-COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH2-COO, C6H5SO3, OOC-CH=CH-COO (maleate), OOC-CH=CH-COO (fumarate), C(OH)(CH2COOH)2COO , AsO4, BiO4, CrO4, MnO4, PtF6, PtCl6, PtBr6, PtI6, SbO4, SeO4, TeO4, HCOO, SCN, NH2, CHO, CHCHO, CHCHO, O-(CH2)-O (ethylene glycolate), O-CH2-CH(OH)-CH2-O (glycerate), OOCCH2COO (malonate), ethylenediaminetetraacetate, citrate, nitrilotriacetate, penicillamate, dimercaptoate, and cyclopentadienyl.

[0036] B((COO)2) is bisoxalatoborate, OOC-(CH2)2-COO is succinate, OOC-CH2-COO is malonate, OOC-CH(OH)-CH(OH)-COO is tartrate, OOC-CH(OH)-CH2-COO is malate, C6H5SO3 is benzenesulfonate, OOC-CH=CH-COO is maleate, OOC-CH=CH-COO is fumarate, and C(OH)(CH2COOH)2COO is citrate. Maleic acid is the trans isomer, and fumaric acid is the cis isomer; they have the same chemical formula, but are geometric isomers.

[0037] G is preferably, for example, O, OH, CO3, (COO)2, O-(CH2)-O, SO4, and particularly preferably O. O has a strong covalent bond with E, and it is difficult for E to be reduced.

[0038] In the compound represented by formula (1), 0 ≦ c ≦ 6.0, preferably 0.1 ≦ c, and more preferably 0.5 ≦ c. In this range, the solid electrolyte containing G has a wide potential window on the reduction side and is difficult to be reductively decomposed. Also, it is preferable that c ≦ 3.0. If the content of G is large, the ionic conductivity of the solid electrolyte decreases.

[0039] In formula (1), X is at least one selected from the group consisting of F, Cl, Br, and I. When the solid electrolyte contains X, the ionic conductivity of the solid electrolyte increases. It is particularly preferable that X contains Cl. When X is Cl, it becomes a solid electrolyte with high ionic conductivity and a good balance of oxidation resistance and reduction resistance.

[0040] In the compound represented by formula (1), 0 < d ≦ 6.1. In the compound represented by formula (1), it is preferable that 1 ≦ d. When 1 ≦ d, when the solid electrolyte is pressure-molded into a pellet shape, a pellet having sufficient strength can be obtained. Also, when 1 ≦ d, the effect of increasing the ionic conductivity due to the inclusion of X can be sufficiently obtained.

[0041] The halide solid electrolyte represented by formula (1) is, for example, Li2ZrCl6, Li2ZrOCl4, Li2ZrN 0.1 Cl 5.7 , Li2Zr(OH) 1.5 Cl 4.5 , Li2ZrCO3Cl4, Li2ZrSO4Cl4, Li2ZrPO3Cl4, Li2ZrCH3OCl5, Li2ZrNH2Cl5, Li2Zr(HCOO) 0.5 Cl 5.5 , Li2Zr(CH3COO) 0.2 Cl 5.8 , Li2Zr(CF3COO) 0.2 Cl 5.8, Li2Zr((COO)2) 0.1 Cl 5.8 , Li2Zr(EG) 0.1 Cl 5.7 (EG is the ethylene glycol anion, i.e. - O-(CH2)2-O - ), Li2Zr bis(cyclopentadienyl)Cl4, Li3YCl6, Li3YOCl4, Li3YSO4Cl4, Li3YCO3Cl4, LiNbOCl4, LiTaOCl4, etc.

[0042] (Method of manufacturing solid electrolyte) When the solid electrolyte is in a powder state, it can be produced by, for example, a mechanochemical method. For example, raw material powders containing predetermined elements in a predetermined molar ratio are mixed and reacted. When the solid electrolyte is in a sintered state, it can be produced by, for example, a solid-state reaction method. For example, raw material powders containing predetermined elements in a predetermined molar ratio are mixed and molded, and then sintered in a vacuum or inert gas atmosphere.

[0043] When a halide raw material is contained in the raw powder, the halide raw material is likely to evaporate when the temperature is increased. Therefore, halogen gas may be present in the sintering atmosphere to compensate for the halogen. Furthermore, when a halide raw material is contained in the raw powder, sintering may be performed by hot pressing using a mold with high airtightness. In this case, the mold has high airtightness, so evaporation of the halide raw material due to sintering can be suppressed. By sintering in this manner, a solid electrolyte in the form of a sintered body made of a compound having a predetermined composition is obtained.

[0044] A coating layer is formed on the surface of the solid electrolyte prepared by the above procedure. When the coating layer is polyparaxylylene, it can be formed using, for example, a vapor deposition device (manufactured by Comelec). When the coating layer is diamond-like carbon, it can be formed using, for example, plasma CVD using hydrocarbon gas as a raw material, ionization vapor deposition, or sputtering using a solid carbon target.

[0045] The solid electrolyte according to this embodiment has a coating layer containing polyparaxylylene or diamond-like carbon, and therefore has excellent moisture resistance. This is thought to be because the polyparaxylylene or diamond-like carbon acts as a hydrophobic layer, preventing moisture from penetrating into the solid electrolyte. The solid electrolyte according to this embodiment is resistant to degradation by water, and its ionic conductivity is less likely to decrease even in the atmosphere. Therefore, by using the solid electrolyte according to this embodiment, a solid electrolyte battery can be fabricated not only in a glove box filled with an inert gas, but also in a dry room where the moisture content is below a certain level.

[0046] Polyparaxylylene and diamond-like carbon are mechanically harder than silicon-based resins. Therefore, there was a possibility that the coating of polyparaxylylene or diamond-like carbon could peel off during the battery manufacturing process. However, when coating layers were fabricated using polyparaxylylene or diamond-like carbon, peeling of these coatings and a decrease in performance were not confirmed. Furthermore, because polyparaxylylene or diamond-like carbon is mechanically hard, cracks may occur when compressed. These cracks act as paths for ion conduction, increasing the ionic conductivity of the solid electrolyte.

[0047] The solid electrolyte according to this embodiment has a water contact angle of 70° or more and 150° or less. Here, the contact angle of the solid electrolyte is measured using pellets obtained by pressure molding particles of the above-mentioned solid electrolyte. In general, solid electrolytes have high wettability and are not water-repellent. The solid electrolyte layer according to this embodiment is highly hydrophobic because it includes a solid electrolyte on which a coating layer containing polyparaxylylene or diamond-like carbon is formed.

[0048] A solid electrolyte with a large water contact angle is less likely to have a decrease in ionic conductivity even in a humid environment. Here, a method for increasing the contact angle of the solid electrolyte using polyparaxylylene or diamond-like carbon has been presented, but the present invention is not limited to this example, and the water contact angle may be increased using other means. For example, the water contact angle may be increased by using a resin other than polyparaxylylene or diamond-like carbon.

[0049] The solid electrolyte according to this embodiment has a Rockwell hardness of R80 or more and R122 or less, or a Vickers hardness of 700 or more and 1900 or less. The Rockwell hardness can be measured using an R scale in accordance with JIS K 7202-2 (2001). The Vickers hardness is measured in accordance with JIS Z 2244:2009. The hardness is measured using pellets obtained by pressure molding particles of the above-mentioned solid electrolyte, similar to the contact angle measurement.

[0050] The solid electrolyte layer according to this embodiment is hard, as shown by the hardness measured above. This is thought to be because the solid electrolyte layer is made of a solid electrolyte having a coating layer containing hard polyparaxylylene or diamond-like carbon. Because polyparaxylylene or diamond-like carbon is mechanically hard, it cracks when compressed, ensuring paths for ion conduction through the cracks, thereby increasing ion conductivity.

[0051] [Solid electrolyte battery] Fig. 1 is a cross-sectional schematic diagram of a solid electrolyte battery according to this embodiment. The solid electrolyte battery 10 shown in Fig. 1 includes a positive electrode 1, a negative electrode 2, and a solid electrolyte layer 3. The solid electrolyte layer 3 is sandwiched between the positive electrode 1 and the negative electrode 2. The above-mentioned solid electrolyte may be contained in the solid electrolyte layer 3, or in the positive electrode 1 or the negative electrode 2, or in both. External terminals (not shown) are connected to the positive electrode 1 and the negative electrode 2, and are electrically connected to the outside.

[0052] The solid electrolyte battery 10 is charged or discharged by the exchange of ions between the positive electrode 1 and the negative electrode 2 via the solid electrolyte layer 3, and the exchange of electrons via an external circuit. The solid electrolyte battery 10 may be a laminate in which the positive electrode 1, the negative electrode 2, and the solid electrolyte layer 3 are stacked, or may be a wound body in which the laminate is wound. Solid electrolyte batteries are used, for example, in laminate batteries, prismatic batteries, cylindrical batteries, coin batteries, button batteries, etc.

[0053] <Solid electrolyte layer> The solid electrolyte layer 3 is sandwiched between the positive electrode 1 and the negative electrode 2. The solid electrolyte layer 3 contains a solid electrolyte that can transfer ions when an external voltage is applied. For example, the solid electrolyte conducts lithium ions and inhibits the transfer of electrons.

[0054] The solid electrolyte layer 3 is, for example, a halide-based solid electrolyte. The solid electrolyte layer 3 includes, for example, the above-mentioned solid electrolyte. When the above-mentioned solid electrolyte is contained in the positive electrode 1 or the negative electrode 2, the solid electrolyte contained in the solid electrolyte layer 3 is not limited to the above-mentioned solid electrolyte.

[0055] <Positive electrode> 1, the positive electrode 1 has a plate-like (foil-like) positive electrode current collector 1A and a positive electrode mixture layer 1B. The positive electrode mixture layer 1B is in contact with at least one surface of the positive electrode current collector 1A.

[0056] "Positive electrode current collector" The positive electrode current collector 1A may be made of any electrically conductive material that is resistant to oxidation during charging and corrosion. The positive electrode current collector 1A may be made of a metal such as aluminum, stainless steel, nickel, or titanium, or a conductive resin. The positive electrode current collector 1A may be in the form of a powder, foil, punched, or expanded.

[0057] "Positive electrode mixture layer" The positive electrode mixture layer 1B contains a positive electrode active material, and optionally a solid electrolyte, a binder, and a conductive additive.

[0058] (Cathode active material) The positive electrode active material is not particularly limited as long as it can reversibly absorb and release, and insert and extract (intercalate and deintercalate) lithium ions. Positive electrode active materials used in known lithium ion secondary batteries can be used. Examples of positive electrode active materials include lithium-containing metal oxides and lithium-containing metal phosphates.

[0059] Lithium-containing metal oxides include, for example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese spinel (LiMnO), and lithium manganese oxides represented by the general formula: LiNi x Co y Mn z O2 (x+y+z=1), lithium vanadium compounds (LiVOPO4, Li3V2(PO4)3), olivine-type LiMPO4 (where M represents at least one element selected from Co, Ni, Mn, and Fe), and lithium titanate (Li4Ti5O 12 ) etc.

[0060] The positive electrode active material may also be lithium-free. Examples of such positive electrode active materials include non-lithium-containing metal oxides (MnO2, V2O5, etc.), non-lithium-containing metal sulfides (MoS2, etc.), and non-lithium-containing fluorides (FeF3, VF3, etc.). When using a lithium-free positive electrode active material, the negative electrode is doped with lithium ions in advance, or a lithium-ion-containing negative electrode is used.

[0061] (binder) The positive electrode mixture layer 1B may contain a binder. The binder bonds together the positive electrode active material, solid electrolyte, and conductive additive that constitute the positive electrode mixture layer 1B. The binder also bonds the positive electrode mixture layer 1B and the positive electrode current collector 1A. The binder preferably has oxidation resistance and good adhesiveness.

[0062] Examples of binders used in the positive electrode mixture layer 1B include polyvinylidene fluoride (PVDF) or copolymers thereof, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid (PA) and copolymers thereof, metal ion crosslinked polyacrylic acid (PA) and copolymers thereof, maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted polyethylene (PE), or mixtures thereof. Among these, PVDF is particularly preferred as the binder.

[0063] The binder content in the positive electrode mixture layer 1B is not particularly limited, but is preferably 1% by mass to 15% by mass, and more preferably 3% by mass to 5% by mass, based on the total mass of the positive electrode active material, solid electrolyte, conductive additive, and binder. If the binder content is too low, it tends to be difficult to form a positive electrode 1 with sufficient adhesive strength. Conversely, if the binder content is too high, general binders are electrochemically inactive and do not contribute to discharge capacity, making it difficult to obtain sufficient volume or mass energy density.

[0064] (solid electrolyte) The positive electrode mixture layer 1B may contain a solid electrolyte. The solid electrolyte is, for example, the solid electrolyte described above. The solid electrolyte may be a solid electrolyte other than the solid electrolyte described above. The content of the solid electrolyte in the positive electrode mixture layer 1B is not particularly limited, but is preferably 1% by volume or more and 50% by volume or less, and more preferably 5% by volume or more and 30% by volume or less, based on the total mass of the positive electrode active material, the solid electrolyte, the conductive additive, and the binder.

[0065] (Conductive additive) The conductive additive improves the electronic conductivity of the positive electrode mixture layer 1B. Known conductive additives can be used. Examples of conductive additives include carbon materials such as carbon black, graphitized carbon black, graphite, carbon nanotubes, and graphene; metals such as aluminum, copper, nickel, stainless steel, iron, and amorphous metals; conductive oxides such as ITO; conductive polymers (polyaniline, polyacetylene, and the like); and mixtures thereof. The conductive additive may be in the form of powder or fiber.

[0066] There are no particular limitations on the content of the conductive additive in the positive electrode mixture layer 1B. When the positive electrode mixture layer 1B contains the conductive additive, the content is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the total mass of the positive electrode active material, the solid electrolyte, the conductive additive, and the binder.

[0067] <Negative electrode> 1, the negative electrode 2 has a negative electrode current collector 2A and a negative electrode mixture layer 2B. The negative electrode mixture layer 2B is in contact with at least one surface of the negative electrode current collector 2A.

[0068] "Negative electrode current collector" The negative electrode current collector 2A only needs to be electrically conductive. Examples of materials that can be used as the negative electrode current collector 2A include metals such as copper, aluminum, nickel, stainless steel, and iron, and conductive resin foil. The negative electrode current collector 2A may be in the form of powder, foil, punched, or expanded.

[0069] "Negative electrode mixture layer" The negative electrode mixture layer 2B contains a negative electrode active material, and optionally a solid electrolyte, a binder, and a conductive additive.

[0070] (Negative electrode active material) The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions and insert and extract lithium ions. As the negative electrode active material, any negative electrode active material used in known solid electrolyte batteries can be used.

[0071] Examples of the negative electrode active material include carbon materials such as natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, and organic compound sintered bodies, Si, SiO x Metals that can combine with lithium, such as Sn and aluminum, their alloys, composites of these metals and carbon materials, lithium titanate (Li4Ti5O 12 ), oxides such as SnO2, metallic lithium, etc. The negative electrode active material is preferably natural graphite.

[0072] (binder) The negative electrode mixture layer 2B may contain a binder. The binder bonds together the negative electrode active material, solid electrolyte, and conductive additive that constitute the negative electrode mixture layer 2B. The binder also bonds the negative electrode mixture layer 2B and the negative electrode current collector 2A.

[0073] Examples of binders used in the negative electrode mixture layer 2B include polyvinylidene fluoride (PVDF) or copolymers thereof, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PA) and copolymers thereof, metal ion crosslinked polyacrylic acid (PA) and copolymers thereof, maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted polyethylene (PE), and mixtures thereof. Among these, it is preferable to use one or more binders selected from SBR, CMC, and PVDF.

[0074] The binder content in the negative electrode mixture layer 2B is not particularly limited, but is preferably 1% by mass or more and 15% by mass or less, and more preferably 1.5% by mass or more and 10% by mass or less, based on the total mass of the negative electrode active material, the conductive additive, and the binder.

[0075] (solid electrolyte) The negative electrode mixture layer 2B may contain a solid electrolyte. The solid electrolyte may be, for example, the solid electrolyte described above. The solid electrolyte may be a solid electrolyte other than the solid electrolyte described above. The content of the solid electrolyte is not particularly limited, but is preferably 1% by volume or more and 50% by volume or less, and more preferably 5% by volume or more and 30% by volume or less, based on the total mass of the negative electrode active material, solid electrolyte, conductive additive, and binder.

[0076] (Conductive additive) The conductive additive contained in the negative electrode mixture layer 2B can be the same as that in the positive electrode mixture layer 1B. The content of the conductive additive in the negative electrode mixture layer 2B is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 12% by mass or less, relative to the negative electrode active material.

[0077] <Exterior body> The exterior housing houses a battery element consisting of a positive electrode 1, a solid electrolyte layer 3, and a negative electrode 2. The exterior housing prevents moisture and other elements from entering the interior from the outside. The exterior housing is, for example, a metal laminate film made by coating both sides of a metal foil with a polymer film. The metal laminate film is formed into a bag shape and the opening is heat-sealed to form the exterior housing.

[0078] The metal foil is, for example, aluminum foil, stainless steel foil, etc. The polymer film disposed on the outside of the exterior body is preferably made of a polymer with a high melting point, such as polyethylene terephthalate (PET), polyamide, etc. The polymer film disposed on the inside of the exterior body is, for example, polyethylene (PE), polypropylene (PP), etc.

[0079] <External terminal> The external terminals include a positive electrode terminal and a negative electrode terminal. The positive electrode terminal is electrically connected to the positive electrode 1, and the negative electrode terminal is electrically connected to the negative electrode 2. The external terminals are made of a conductive material such as aluminum or nickel.

[0080] [Solid electrolyte battery manufacturing method] Next, a method for manufacturing a solid electrolyte battery according to this embodiment will be described. First, the solid electrolyte according to this embodiment is manufactured by the method described above.

[0081] Next, the positive electrode 1 is prepared. The positive electrode 1 is produced by applying a paste containing a positive electrode active material onto a positive electrode current collector 1A and drying it to form a positive electrode mixture layer 1B. The above-mentioned solid electrolyte may be added to the paste containing the positive electrode active material.

[0082] Next, the negative electrode 2 is prepared. The negative electrode 2 is produced by applying a paste containing a negative electrode active material onto a negative electrode current collector 2A and drying it to form a negative electrode mixture layer 2B. The above-mentioned solid electrolyte may be added to the paste containing the negative electrode active material.

[0083] The battery element can be produced, for example, by powder molding. A guide with a hole is placed on the positive electrode 1, and the guide is filled with a solid electrolyte. The solid electrolyte used here is, for example, the solid electrolyte described above. The surface of the solid electrolyte is then smoothed, and the negative electrode 2 is placed on top of the solid electrolyte. This sandwiches the solid electrolyte between the positive electrode 1 and the negative electrode 2. Pressure is then applied to the positive electrode 1 and the negative electrode 2 to pressure-mold the solid electrolyte. This pressure molding produces a laminate in which the positive electrode 1, solid electrolyte layer 3, and negative electrode 2 are stacked in this order.

[0084] Next, external terminals are welded to the positive electrode current collector 1A of the positive electrode 1 and the negative electrode current collector 2A of the negative electrode 2, which form the laminate, by a known method, to electrically connect the positive electrode current collector 1A or the negative electrode current collector 2A to the external terminals. Thereafter, the laminate connected to the external terminals is housed in an exterior body, and the opening of the exterior body is heat-sealed to seal it. Through these steps, the solid electrolyte battery of this embodiment is obtained.

[0085] The solid electrolyte battery according to this embodiment includes a solid electrolyte having a predetermined composition, and therefore the ionic conductivity of the solid electrolyte is unlikely to decrease even in a moisture-containing atmosphere, resulting in excellent ionic conductivity.

[0086] The above describes the embodiments of the present invention in detail with reference to the drawings. However, each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications of the configurations are possible within the scope that does not deviate from the spirit of the present invention. [Example]

[0087] "Example 1" (Preparation of solid electrolyte) In a glove box with a dew point of approximately -85°C, lithium oxide (Li2O) and zirconium chloride (ZrCl4) were weighed out in a 1:1 molar ratio. The raw material powder was then placed in a zirconia sealed container for a planetary ball mill, which had already contained zirconia balls. The sealed container was then covered with a lid, screwed onto the container body, and sealed with polyimide tape between the lid and the container. The polyimide tape effectively blocks moisture. The zirconia sealed container was then placed in the planetary ball mill. The raw material powder was subjected to a mechanochemical reaction for 24 hours at a rotation speed of 500 rpm and a revolution speed of 500 rpm (rotation and revolution directions opposite). This reaction yielded the solid electrolyte Li2ZrOCl4.

[0088] The planetary ball mill is installed in a normal atmosphere (air). The zirconia sealed container for the planetary ball mill is screwed in and sealed with polyimide tape, and when the zirconia sealed container is set in the planetary ball mill, it is firmly pressed and fixed in place. Therefore, even in a normal atmosphere, it is thought that almost no moisture from the air gets mixed into the zirconia sealed container.

[0089] Next, a deposition apparatus (manufactured by Comelec) was used to coat the surface of the solid electrolyte with polyparaxylylene (Parylene N (registered trademark)) to a thickness of 10 nm. The structure of polyparaxylylene is shown below.

[0090] [ka]

[0091] [Measurement of ionic conductivity] The solid electrolyte with the polyparaxylylene vapor-deposited on it was brought into a dry room, and 0.2 g of the solid electrolyte was weighed onto aluminum foil. The dry room environment was air (oxygen concentration: approximately 21% by volume, oxygen partial pressure: 0.21 atm) with a dew point of -50°C (relative humidity: 2000 ppm) and a room temperature of 25°C. The weighed solid electrolyte was exposed to the dry room for 4 and 8 hours. Next, in a glove box with a dew point of approximately -85°C and circulating argon gas, the solid electrolyte powder exposed for the predetermined time in the dry room was loaded into a pressure molding die and pressure-molded under a load of approximately 30 kN to prepare a measurement cell for ionic conductivity.

[0092] The pressure molding die consists of a 10 mm diameter cylinder made of PEEK (polyether ether ketone), and upper and lower punches made of SKD11 material with a diameter of 9.99 mm.

[0093] Next, a 50 mm diameter, 5 mm thick stainless steel disk and a Teflon® disk with four screw holes were prepared and set into the pressure molding die as follows: stainless steel disk / Teflon® disk / pressure molding die / Teflon® disk / stainless steel disk, and the four screws were tightened with a torque of approximately 3 N m. Screws were also inserted into the screw holes on the sides of the upper and lower punches to serve as external connection terminals.

[0094] The external connection terminal was connected to a Bio-Logic EC-Lab electrochemical measurement system VMP-300, and ionic conductivity was measured using the impedance measurement method at a measurement frequency range of 1 MHz to 0.1 Hz, an amplitude of 10 mV, and a temperature of 25°C.

[0095] Similarly to measuring ionic conductivity, the water contact angle, Rockwell hardness, and Vickers hardness were measured using pellets obtained by pressure molding the solid electrolyte. The water contact angle was measured using a DM0-902 manufactured by Kyowa Interface Science Co., Ltd. The Rockwell hardness was measured using an HR-210MR manufactured by Mitutoyo Corporation, and the Vickers hardness was measured using an HM-102 manufactured by Mitutoyo Corporation. The water contact angle, Rockwell hardness, and Vickers hardness measurements were carried out in a dry room.

[0096] "Examples 2 to 5" Examples 2 to 5 differ from Example 1 in that the material of the coating layer coating the surface of the solid electrolyte was changed. Other conditions were the same as in Example 1, and the time change in ionic conductivity, water contact angle, and hardness of the solid electrolyte layer of Examples 2 to 5 were measured. The coating layers of Examples 2 to 5 were as follows:

[0097] Example 2: Poly-2-chloroparaxylylene (Parylene C (registered trademark)) in which one hydrogen atom on the benzene ring is substituted with chlorine. The chemical formula of poly-2-chloroparaxylylene of Example 2 is shown below.

[0098] [ka]

[0099] Example 3: Poly-2,5-dichloroparaxylylene (Parylene D (registered trademark)) in which two hydrogen atoms on the benzene ring are replaced with chlorine atoms. The chemical formula of poly-2,5-dichloroparaxylylene of Example 3 is shown below.

[0100] [ka]

[0101] Example 4: Polydifluoroparaxylylene (Parylene HT®) with α-hydrogen substituted with fluorine The chemical formula of the polydifluoroparaxylylene of Example 4 is shown below.

[0102] [ka]

[0103] Example 5: Diamond-like carbon

[0104] "Examples 6 to 9" Examples 6 to 9 differ from Example 4 in that the thickness of the coating layer applied to the surface of the solid electrolyte was changed. Other conditions were the same as in Example 4, and the water contact angle, Rockwell hardness, and ionic conductivity of the solid electrolyte layers of Examples 6 to 9 were measured over time. The results are shown in Table 1.

[0105] "Examples 10 to 26" Examples 10 to 26 differ from Example 1 in that the matrix of the solid electrolyte forming the coating layer was changed from LiZrOCl to another solid electrolyte. The other conditions were the same as in Example 1, and the water contact angle, Rockwell hardness, and ionic conductivity of the solid electrolyte layers of Examples 10 to 26 were measured over time and are shown in Table 1.

[0106] "Comparative Example 1" Comparative Example 1 differs from Example 1 in that no polyparaxylylene coating was performed. Other conditions were the same as in Example 1, and the contact angle with water, Rockwell hardness, and ionic conductivity were measured over time, and the results are shown in Table 1.

[0107] The measurement results of the ionic conductivity of Examples 1 to 26 and Comparative Example 1 are summarized in Table 1.

[0108] [Table 1]

[0109] As shown in Table 1, the solid electrolytes of Examples 1 to 26 coated with polyparaxylylene or diamond-like carbon showed a smaller decrease in ionic conductivity than the solid electrolyte of Comparative Example 1. [Explanation of symbols]

[0110] 1... positive electrode, 1A... positive electrode current collector, 1B... positive electrode mixture layer, 2... negative electrode, 2A... negative electrode current collector, 2B... negative electrode mixture layer, 3... solid electrolyte layer, 10... solid electrolyte battery

Claims

1. having a coating layer attached to the surface; The coating layer is a solid electrolyte containing polyparaxylylene or diamond-like carbon.

2. The solid electrolyte according to claim 1 , wherein the thickness of the coating layer is 1 nm or more and 1000 nm or less.

3. 2. The solid electrolyte according to claim 1, wherein the polyparaxylylene is at least one selected from the group consisting of polyparaxylylene, poly2-chloroparaxylylene, poly2,5-dichloroparaxylylene, and polydifluoroparaxylylene.

4. 2. The solid electrolyte according to claim 1, wherein the contact angle of water is 70° or more and 105° or less.

5. 2. The solid electrolyte according to claim 1, having a Rockwell hardness of R80 or more and R122 or less, or a Vickers hardness of 700 or more and 1900 or less.

6. The solid electrolyte according to claim 1 , comprising a compound represented by the following formula (1): A ａ E ｂ G ｃ X ｄ ・・・(1) In formula (1), A is at least one element selected from the group consisting of Li, Cs, Ca, Rb, Sr, and Ba; E is at least one element selected from the group consisting of Mg, Al, Sc, Y, Nb, Zr, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, Ge, In, Sn, Ta, W, and lanthanoids; and G is O, OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO ４ , Si ２ O ７ , Si ３ O ９ , Si ４ O １１ , Si ６ O １８ , P.O. ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , B.F. ４ , P.F. ６ , B((COO) ２ ), (COO) ２ , N, AlCl ４ , C.F. ３ SO ３ , C.H. ３ COO, CF ３ COO,OOC-(CH ２ ) ２ -COO,OOC-CH ２ -COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH ２ -COO, C ６ H ５ SO ３ , OOC-CH=CH-COO (maleate), OOC-CH=CH-COO (fumarate), C(OH)(CHCOOH) ２ COO, AsO ４ , Bio ４ , CrO ４ , MnO ４ , PtF ６ , PtCl ６ , PtBr ６ , PtI ６ , SbO ４ , SeO ４ , TeO ４ , HCOO, SCN, NH ２ , C.H. ３ O, CH ３ CH ２ O, O-(CH ２ )—O(ethylene glycolate), O—CH ２ -CH(OH)-CH ２ is at least one group selected from the group consisting of -O (glycerate), OOCCH2COO (malonate), ethylenediaminetetraacetate, citrate, nitrilotriacetate, penicillamate, dimercaptoate, and cyclopentadienyl; X is at least one element selected from the group consisting of F, Cl, Br, and I; a satisfies 0.5≦a<6, b satisfies 0<b<2, c satisfies 0≦c≦6.0, and d satisfies 0<d≦6.

1.

7. The solid electrolyte according to claim 6 , wherein in formula (1), E includes Zr.

8. An electrode comprising the solid electrolyte of claim 1.

9. A solid electrolyte battery comprising the solid electrolyte of claim 1.

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