All solid state battery

Abstract

To provide an all-solid-state battery excellent in cycle characteristics.SOLUTION: In the present disclosure, there is provided an all-solid-state battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer. At least one layer of the positive electrode layer, the negative electrode layer and the solid electrolyte layer contains a sulfide solid electrolyte and a host-guest type binder. The host-guest type binder has a monomer unit containing a cyclic host group and a monomer unit containing a guest group. The gust group is included in the cyclic host group, and the host-guest type binder has a glass transition temperature (Tg) of 30°C or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to all-solid-state batteries. [Background technology]

[0002] It is known that sulfide solid electrolytes and binders are used in all-solid-state batteries. For example, Patent Document 1 discloses the use of polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylylene fluoride (PVDF), acrylic, ethyl methyl cellulose, or the like as binders used in all-solid-state batteries. In addition, Patent Document 2 discloses a gel battery using a gel electrolyte binder having a host-guest structure, although it is not a technology related to all-solid-state batteries. Furthermore, Patent Document 3 discloses a negative electrode having a negative electrode active material layer containing a polymer containing a cyclic host group and a guest group. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-069843 A [Patent Document 2] China Patent Application Publication No. 108258322 [Patent Document 3] JP 2019-204719 A Summary of the Invention [Problem to be solved by the invention]

[0004] An all-solid-state battery is prone to expansion and contraction due to charging and discharging, which may result in a decrease in performance such as cycle characteristics. The present disclosure has been made in view of the above-mentioned circumstances, and has as its main object to provide an all-solid-state battery having excellent cycle characteristics. [Means for solving the problem]

[0005] In order to solve the above problems, the present disclosure provides an all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein at least one layer of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a sulfide solid electrolyte and a host-guest type binder, the host-guest type binder has a monomer unit containing a cyclic host group and a monomer unit containing a guest group, the guest group is included in the cyclic host group, and the glass transition temperature (Tg) of the host-guest type binder is 30° C. or lower.

[0006] According to the present disclosure, at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a sulfide solid electrolyte and a host-guest type binder having a predetermined glass transition temperature, resulting in an all-solid-state battery with excellent cycle characteristics.

[0007] In the above disclosure, the cyclic host group may contain at least one of a cyclodextrin skeleton, a cyclophane skeleton, and a cucurbituril skeleton.

[0008] In the above disclosure, the guest group may contain an adamantyl group.

[0009] In the above disclosure, the negative electrode layer may contain a negative electrode active material, the sulfide solid electrolyte, and the host-guest binder.

[0010] In the above disclosure, the negative electrode active material may be a Si-based active material. Effect of the Invention

[0011] The present disclosure has an effect of providing an all-solid-state battery having excellent cycle characteristics. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure. [Diagram 2] FIG. 1 is a schematic diagram showing the structure of a host-guest type binder in the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The all-solid-state battery according to the present disclosure will be described in detail below.

[0014] Fig. 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure. The all-solid-state battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, a solid electrolyte layer 3 formed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, a negative electrode current collector 5 that collects current from the negative electrode layer 2, and a battery case 6 that houses these members. At least one layer of the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layer 3 contains a sulfide solid electrolyte and a host-guest type binder having a predetermined glass transition temperature.

[0015] According to the present disclosure, at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a sulfide solid electrolyte and a host-guest type binder having a predetermined glass transition temperature, resulting in an all-solid-state battery with excellent cycle characteristics.

[0016] As mentioned above, Patent Document 2 discloses a gel battery using a gel electrolyte binder having a host-guest structure. Binders having such a structure are known to have self-repairing properties, and it is expected that adding such binders to an electrode layer will enable self-repair even if cracks occur in the electrode layer. On the other hand, the binder disclosed in Patent Document 2 exhibits self-repairing properties when swollen in an organic solvent or electrolyte, that is, in a liquid-based battery, but is considered not to exhibit sufficient self-repairing properties in an all-solid-state battery in which the binder is used in a dry state. This is considered to be due to the following reasons.

[0017] Patent Document 2 lists methyl methacrylate, acrylonitrile, hexafluoropropene, vinyl acetal, vinylidene, vinyl alcohol, and tetrafluoroethylene as constituent materials of the binder (polymer). Since all of these have a glass transition temperature (Tg) above room temperature, it is presumed that the Tg of the resulting binder is also above room temperature. Here, the battery is used assuming a temperature near room temperature. Therefore, if the Tg is higher than room temperature, the mobility of the polymer in the battery decreases. Since the polymer is used in a gel state in a liquid battery, it is considered that the influence of the mobility of the polymer caused by the Tg is small, but it is considered that the mobility of the polymer decreases significantly in an all-solid-state battery that uses a binder in a dry state. Therefore, even if a binder such as that disclosed in Patent Document 2 is applied to an all-solid-state battery, it is expected that the mobility of the polymer is small and the contact area of ​​the repaired part is small in the all-solid-state battery, so that the time required for self-repair is very long. As a result, it is considered that sufficient self-repairing ability is not exhibited.

[0018] On the other hand, the host-guest type binder in the present disclosure has a Tg of 30° C. or less. Therefore, the binder (polymer) has good mobility even in a solid-state battery in a dry state. If the polymer has good mobility, the cracks in the electrode layer can be sufficiently repaired, and the cycle characteristics of the all-solid-state battery are good. In addition, since the transport of ions in a battery depends on the molecular motion of the polymer, a battery using the binder in the present disclosure with good mobility also has good ion conductivity.

[0019] In addition, the host-guest type binder in the present disclosure is used together with a sulfide solid electrolyte in an all-solid-state battery. Since the interface of a sulfide solid electrolyte can be constructed at a relatively low temperature (for example, 250°C or less), it is considered that the binder does not decompose. On the other hand, an oxide solid electrolyte needs to be fired at a high temperature to construct the interface, and the binder may be carbonized and decomposed by the heat. Although the above Patent Document 3 discloses that a solid electrolyte can be used in a battery, it does not describe or suggest the use of a host-guest type binder together with a sulfide solid electrolyte. As shown in the examples described later, in the present disclosure, the cycle characteristics are significantly improved by using a host-guest type binder together with a sulfide solid electrolyte.

[0020] 1. Host-guest binder Fig. 2 is a schematic diagram showing the structure of a host-guest type binder in the present disclosure. As shown in Fig. 2, the host-guest type binder in the present disclosure has a monomer unit containing a cyclic host group and a monomer unit containing a guest group, and the guest group is included in the cyclic host group. The glass transition temperature of the host-guest type binder is 30°C or lower. In Fig. 2, the cyclic host group contains a cyclodextrin skeleton, and the guest group is an adamantyl group.

[0021] (1) Monomer Unit Containing a Cyclic Host Group The host-guest type binder in the present disclosure has a monomer unit (hereinafter also referred to as a first monomer unit) containing a cyclic host group. The host-guest type binder may have one type of the first monomer unit, or may have two or more types of the first monomer unit.

[0022] The cyclic host group contains, for example, at least one of a cyclodextrin skeleton, a cyclophane skeleton, and a cucurbituril skeleton, and may contain a substituent thereof.

[0023] Specific examples of cyclic host groups include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, calix[6]arene sulfonic acid, calix[8]arene sulfonic acid, 12-crown-4, 18-crown-6, [6]paracyclophane, [2,2]paracyclophane, cucurbit[6]uril, and cucurbit[8]uril. Among these, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin are preferred.

[0024] The chemical structure of the first monomer unit is represented, for example, by the following general formula (1).

[0025] [ka]

[0026] In the general formula (1), R represents a hydrogen atom or a methyl group, R 1 represents a divalent group formed by removing one hydrogen atom from a monovalent group such as a hydroxyl group, a thiol group, an alkoxy group which may have one or more substituents, a thioalkoxy group which may have one or more substituents, an alkyl group which may have one or more substituents, an amino group which may have one substituent, an amido group which may have one or more substituents, or an aldehyde group or a carboxyl group, n represents 0 or 1, and Host represents a cyclic host group.

[0027] The ratio of the first monomer unit to the total monomer units constituting the host-guest type binder is, for example, 0.05 mol% or more, may be 0.5 mol% or more, or may be 1.0 mol% or more. On the other hand, the ratio of the first monomer unit to the total monomer units constituting the host-guest type binder is, for example, 3.0 mol% or less, may be 2.5 mol% or less, may be 2.0 mol% or less, or may be 1.5 mol% or less. If the ratio of the host monomer is too high or too low, sufficient adhesion may not be imparted.

[0028] The first monomer unit is usually formed using a monomer (host monomer) containing a cyclic host group. The host monomer is not particularly limited as long as it is a monomer from which the above-mentioned first monomer unit can be obtained. The first monomer unit may also be formed using a compound containing two or more cyclic host groups. Examples of such compounds include dicyclodextrin poly(allylamine) dendrimer (generation 0) monoacrylamide, dicyclodextrin poly(allylamine) dendrimer (generation 0) diacrylamide, dicyclodextrin poly(allylamine) dendrimer (generation 0) monoacrylate, dicyclodextrin poly(allylamine) dendrimer (generation 0) diacrylate, tricyclodextrin poly(allylamine) dendrimer (generation 0) monoacrylamide, tricyclodextrin poly(allylamine) dendrimer (generation 0) monoacrylate, etc.

[0029] (2) Monomer Unit Containing a Guest Group The host-guest type binder in the present disclosure has a monomer unit containing a guest group (hereinafter also referred to as a second monomer unit). The guest group is included in a cyclic host group. The host-guest type binder may have one type of second monomer unit, or may have two or more types of second monomer units.

[0030] The guest group is not particularly limited as long as it is a group that can be included in the corresponding cyclic host group. Examples of the guest group include linear, branched or cyclic alkyl groups having 1 to 18 carbon atoms. Specifically, alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, isohexyl, dodecyl, octadecyl, and adamantyl groups can be mentioned. Each of these may have a substituent. Among these, adamantyl and butyl groups are preferred, and adamantyl groups are particularly preferred. This is because when the cyclic host group has a cyclodextrin skeleton, the self-repairing property of the binder is particularly good.

[0031] The chemical structure of the second monomer unit is represented, for example, by the following general formula (2).

[0032] [ka]

[0033] In the general formula (2), R' represents a hydrogen atom or a methyl group, and R 2 represents a divalent group formed by removing one hydrogen atom from a monovalent group such as a hydroxyl group, a thiol group, an alkoxy group which may have one or more substituents, a thioalkoxy group which may have one or more substituents, an alkyl group which may have one or more substituents, an amino group which may have one substituent, an amido group which may have one or more substituents, or an aldehyde group or a carboxyl group; n represents 0 or 1; and Guest represents a guest group.

[0034] The ratio of the second monomer unit to the total monomer units constituting the host-guest type binder is, for example, 0.05 mol% or more, may be 0.5 mol% or more, or may be 1.0 mol% or more. On the other hand, the ratio of the second monomer unit to the total monomer units constituting the host-guest type binder is, for example, 3.0 mol% or less, may be 2.5 mol% or less, may be 2.0 mol% or less, or may be 1.5 mol% or less. If the ratio of the host monomer is too high or too low, sufficient adhesion may not be imparted.

[0035] The ratio of the first monomer unit and the second monomer unit to the total monomer units constituting the host-guest type binder is, for example, 0.1 mol% or more, may be 1.0 mol% or more, or may be 2.0 mol% or more. On the other hand, the ratio of the first monomer unit and the second monomer unit to the total monomer units constituting the host-guest type binder is, for example, 6.0 mol% or less, may be 5.0 mol% or less, may be 4.0 mol% or less, or may be 3 mol% or less.

[0036] The second monomer unit is usually formed using a monomer containing a guest group (guest monomer). The guest monomer is not particularly limited as long as it is a monomer that can give the above-mentioned second monomer unit.

[0037] (3) Monomer units containing neither cyclic host groups nor guest groups The host-guest type binder in the present disclosure usually has a monomer unit (hereinafter also referred to as a third monomer unit) that does not contain a cyclic host group or a guest group. The third monomer unit is usually a main monomer unit in the host-guest type binder. The host-guest type binder may have one type of third monomer unit, or may have two or more types of third monomer units.

[0038] The ratio of the third monomer unit to all the monomer units constituting the host-guest type binder is, for example, 70 mol % or more, may be 80 mol % or more, or may be 90 mol % or more.

[0039] The third monomer unit is usually formed using a monomer (main monomer) that does not contain a cyclic host group or a guest group. The main monomer may be, for example, acrylic acid, methacrylic acid, or their derivatives such as esters and amides. Specifically, it may be methyl acrylate, ethyl acrylate, butyl acrylate (n-butyl acrylate and t-butyl acrylate), or butyl methacrylate (n-butyl methacrylate and t-butyl methacrylate).

[0040] (4) Host-guest binder The host-guest type binder in the present disclosure has a monomer unit containing a cyclic host group and a monomer unit containing a guest group. The cyclic host group and the guest group are as described above.

[0041] The host-guest binder in the present disclosure has a glass transition temperature (Tg) of 30° C. or lower. Tg may be 20° C. or lower, 10° C. or lower, or 0° C. or lower. Tg may be, for example, −40° C. or higher, −30° C. or higher, −20° C. or higher, or −10° C. or higher. Tg can be measured by a general method such as differential scanning calorimetry (DSC). Tg can be changed by adjusting the type and ratio of monomers constituting the binder.

[0042] The host-guest type binder in the present disclosure usually has a Tg. On the other hand, the host-guest type binder may or may not have a melting point (Tm). Usually, the former is a crystalline resin, and the latter is an amorphous resin. When the host-guest type binder has a Tm, the Tm may be 30°C or less, 20°C or less, or 10°C or less.

[0043] In the host-guest type binder, the guest group is included in the cyclic host group by host-guest interactions between the cyclic host group and the guest group, such as hydrophobic interactions, hydrogen bonds, intermolecular forces, electrostatic interactions, coordinate bonds, π-electron interactions, etc. Therefore, the host-guest type binder in the present disclosure can have a three-dimensional network structure with the above-mentioned host-guest interactions as crosslinking points.

[0044] The host-guest type binder of the present disclosure can be produced, for example, by mixing and dissolving the above-mentioned main monomer, host monomer, and guest monomer in an organic solvent, and then adding a polymerization initiator to cause a reaction. The organic solvent is not particularly limited as long as it can dissolve the above-mentioned monomers and does not deactivate the radicals generated by the polymerization initiator. Examples of the organic solvent include ethanol, N,N-dimethylformamide, dioxane, dimethyl sulfoxide (DMSO), acetone, chloroform, toluene, and hexane.

[0045] In addition, as the polymerization initiator, in the case of radical polymerization, for example, azo compounds, radical photoinitiators, and peroxides can be mentioned. In the case of ionic polymerization, for example, alkyl lithium compounds such as n-butyllithium and Lewis acids such as aluminum trioxide can be mentioned. The reaction temperature and reaction time can be adjusted as appropriate.

[0046] 2. Negative electrode layer The negative electrode layer in the present disclosure contains at least a negative electrode active material. The negative electrode layer preferably contains the above-described host-guest binder and sulfide solid electrolyte. Since the host-guest binder is the same as described in the above "1. Host-guest binder", the description here is omitted.

[0047] The negative electrode layer may contain only the above-described binder as the binder, or may contain other binders, but the former is preferred. The proportion of the binder in the negative electrode layer is, for example, 10% by weight or less, may be 5% by weight or less, or may be 3% by weight or less. On the other hand, the proportion of the binder in the negative electrode layer is, for example, 0.1% by weight or more.

[0048] Examples of the negative electrode active material include metal active materials, carbon active materials, and oxide active materials. Examples of the metal active material include Li, In, Al, Si, Sn, and alloys containing at least one of these. Examples of the carbon active material include graphite, hard carbon, and soft carbon. Examples of the oxide active material include Li4Ti5O 12 , SiO, Nb2O5. Among these, Si-based active materials containing Si are particularly preferred. Examples of the Si-based active material include elemental Si, Si alloys, and SiO x (0 < x < 2). By using a Si-based active material, a high-capacity battery can be obtained. In addition, since the Si-based active material generally has a large expansion and contraction amount, when used together with the self-healing binder of the present disclosure, the effect of improving the cycle characteristics can be obtained more remarkably. Examples of the shape of the negative electrode active material include particulate form.

[0049] The sulfide solid electrolyte preferably contains Li, A (A is at least one of P, Ge, Si, Sn, B, and Al), and S. The sulfide solid electrolyte may further contain a halogen element. Examples of the halogen element include F, Cl, Br, and I. The sulfide solid electrolyte may further contain O.

[0050] The sulfide solid electrolyte has an anion structure with an ortho composition (PS4 3- Structure: SiS4 4- Structure, GeS4 4- Structure: AlS3 3- Structure, BS3 3- It is preferable that the anion has an ortho-composition (structure) as a main component of the anion. This is because the anion has high chemical stability. The ratio of the anion structure having the ortho-composition is, for example, 70 mol % or more, and may be 90 mol % or more, based on the total anion structures in the sulfide solid electrolyte. The ratio of the anion structure having the ortho-composition can be determined, for example, by Raman spectroscopy, NMR, or XPS.

[0051] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte or a glass ceramic-based sulfide solid electrolyte. The glass-based sulfide solid electrolyte can be obtained by vitrifying the raw material. The glass ceramic-based sulfide solid electrolyte can be obtained, for example, by heat treating the above-mentioned glass-based sulfide solid electrolyte. In addition, the sulfide solid electrolyte preferably has a predetermined crystal structure. Examples of the crystal structure include a Thio-LISICON type crystal structure, a LGPS type crystal structure, and an Argyrodite type crystal structure.

[0052] Specific examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m Sn (where m and n are positive numbers. Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In.) Specific examples of the composition of the sulfide solid electrolyte include xLi2S (1-x)P2S5 (0.7≦x≦0.8), yLiI zLiBr (100-yz)Li3PS4 (0≦y≦30, 0≦z≦30).

[0053] The negative electrode layer may contain a conductive assistant as necessary. Examples of the conductive assistant include carbon materials and metal materials. Examples of the carbon materials include vapor grown carbon fiber (VGCF), acetylene black, activated carbon, furnace black, carbon nanotubes, ketjen black, and graphene. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0054] 3. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material. The positive electrode layer preferably contains the above-mentioned host-guest type binder and sulfide solid electrolyte. The host-guest type binder and the sulfide solid electrolyte are the same as those described in "1. Host-guest type binder" and "2. Negative electrode layer" above, so the description here is omitted. Furthermore, the positive electrode layer may contain a conductive assistant as necessary. The conductive assistant is also the same as that of the above-mentioned negative electrode layer.

[0055] The positive electrode active material may be, for example, an oxide active material. Examples of the oxide active material include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 Examples of the positive electrode active material include spinel-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The surface of the positive electrode active material may be coated with an ion-conductive oxide such as LiNbO3. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0056] 4.Solid electrolyte layer The solid electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer. The solid electrolyte layer is a layer containing at least a solid electrolyte. The solid electrolyte layer preferably contains the host-guest type binder and sulfide solid electrolyte described above. The host-guest type binder and the sulfide solid electrolyte are the same as those described in "1. Host-guest type binder" and "2. Negative electrode layer" above, so the description here is omitted. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0057] 5.All-solid-state battery The all-solid-state battery in the present disclosure has the above-mentioned positive electrode layer, negative electrode layer, and solid electrolyte layer. In addition, it usually has a positive electrode current collector that collects the current of the positive electrode layer, and a negative electrode current collector that collects the current of the negative electrode layer. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0058] The all-solid-state battery in the present disclosure may be a primary battery or a secondary battery, but the latter is preferred because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. Note that the secondary battery also includes a secondary battery used as a primary battery (used only for one discharge after charging).

[0059] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0060] [Example 1] (Production of host-guest type binder) The host-guest type binder was produced by mixing and dissolving a cyclic host group-containing monomer (host monomer), a guest group-containing monomer (guest monomer) and a (meth)acrylic monomer as a main monomer in an organic solvent, and then adding a polymerization initiator to cause a reaction, as described below.

[0061] First, 100 parts by weight of dimethyl sulfoxide (DMSO) was added to the reaction vessel as an organic solvent. Next, 87 parts by weight of ethyl acrylate as the main monomer, 2 parts by weight of adamantan-1-yl acrylate (Ad-Ac) as the guest monomer, and 11 parts by weight of acrylic acid-beta-cyclodextrin (β-CDAc) as the host monomer were added to the reaction vessel. This is converted to mol%, and the main monomer: guest monomer: host monomer = 98:1:1. Next, these were stirred until uniform, and 0.2 parts by weight of azobisisobutyronitrile (AIBN) was added as a polymerization initiator. Then, the temperature was raised to 80 ° C and heating was performed while refluxing for 8 hours. The solution after the reaction was vacuum dried at 150 ° C to remove the remaining monomer and solvent. As a result, a dried binder (beta cyclodextrin adamantyl acrylate: β-CD-Ad-EA) was obtained. The binder was dissolved in MIBK (methyl isobutyl ketone) to prepare a 10 wt % MIBK solution, which was then used in the manufacture of the battery. Note that β-CDAc was prepared based on a conventional method, such as that described in JP-A-10-259202.

[0062] (Manufacturing of all-solid-state batteries) Cathode active material (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3O2) and sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5) were mixed so that the weight ratio of active material:sulfide solid electrolyte was 70:30. This mixture was weighed out to be 94.0 parts by weight per 100 parts by weight of the positive electrode layer. Next, 3.0 parts by weight of the PVDF binder solution in solid content and 3.0 parts by weight of the conductive assistant (vapor-grown carbon fiber, manufactured by Showa Denko K.K.) were weighed out to be 100 parts by weight of the positive electrode layer. Furthermore, methyl isobutyl ketone (dehydrated product) was added as a solvent (dispersion medium) so that the solid content rate was 60 wt%, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer (manufactured by SMT Co., Ltd., UH-50) to prepare a slurry for the positive electrode. Then, the slurry for the positive electrode was applied to the surface of an aluminum foil (positive electrode current collector) using an applicator and allowed to dry naturally for 5 minutes. Thereafter, the positive electrode layer was formed by drying with hot air at 100° C. for 60 minutes. In this way, a positive electrode having a positive electrode current collector and a positive electrode layer was produced.

[0063] The negative electrode active material (SiO, particle size 15.0 μm) and the sulfide solid electrolyte (LiI-Li2O-Li2S-P2S5) were mixed so that the weight ratio of the active material:sulfide solid electrolyte was 70:30. This mixture was weighed out to be 94.0 parts by weight per 100 parts by weight of the negative electrode layer. Next, the binder solution (10 wt% MIBK solution) was weighed out to be 3.0 parts by weight of solid content and 3.0 parts by weight of conductive assistant (vapor-grown carbon fiber, manufactured by Showa Denko K.K.) was weighed out to be 3.0 parts by weight per 100 parts by weight of the negative electrode layer. Methyl isobutyl ketone (dehydrated product) was added as a solvent (dispersion medium) to be 60 wt% solid content, and the mixture was kneaded for 1 minute using an ultrasonic homogenizer (manufactured by SMT Co., Ltd., UH-50). After that, the slurry was applied to the surface of the SUS foil (negative electrode current collector) using an applicator, and allowed to dry naturally for 30 minutes. Thereafter, the negative electrode layer was formed by drying with hot air at 100° C. for 60 minutes, thereby producing a negative electrode having a negative electrode current collector and a negative electrode layer.

[0064] 97.0 parts by weight of sulfide solid electrolyte and 3.0 parts by weight of PVDF binder solution in terms of solid content were added to the container. Furthermore, methyl isobutyl ketone was added as a solvent (dispersion medium) so that the solid content was 45 wt%. This was kneaded using an ultrasonic homogenizer (UH-50 manufactured by SMT Co., Ltd.) to obtain a slurry for the solid electrolyte layer. The slurry for the solid electrolyte layer was applied to an aluminum foil (transfer foil) using an applicator and allowed to dry naturally for 5 minutes. After that, the solid electrolyte layer was obtained by drying with hot air at 100°C for 30 minutes.

[0065] In an inert gas atmosphere, the positive electrode layer and the negative electrode layer were stacked so as to face each other with the solid electrolyte layer from which the aluminum foil had been removed sandwiched between them to obtain a laminate. This laminate was pressed at 4.3 tons. As a result, an all-solid-state battery was obtained.

[0066] [Examples 2 to 11] All-solid-state batteries were fabricated in the same manner as in Example 1, except that the type of host monomer, the type of main monomer, the amount of host monomer, the amount of guest monomer, and the type of negative electrode active material were changed as shown in Tables 1 and 2. In the tables, γ-CDAc stands for acrylic acid-γ-cyclodextrin, BA stands for butyl acrylate, MA stands for methyl acrylate, and nBMA stands for n-butyl methacrylate.

[0067] [Comparative Examples 1 to 3] In Comparative Example 1, an all-solid-state battery was fabricated in the same manner as in Example 1, except that ethyl methacrylate (EMA) was used as the main monomer and the Tg was set higher than 30°C. In Comparative Example 2, an all-solid-state battery was fabricated in the same manner as in Example 1, except that no host monomer or guest monomer was used. In Comparative Example 3, an all-solid-state battery was fabricated in the same manner as in Example 1, except that vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) was used as the binder.

[0068] [Comparative Example 4] An all-solid-state battery was fabricated in the same manner as in Example 1, except that a slide-ring material, polyrotaxane (manufactured by Advanced Soft Materials, Inc., product name: Selm Super Polymer SH3400P, weight average molecular weight 700,000), was used as the binder.

[0069] [Comparative Example 5] A liquid-type lithium-ion battery was fabricated as follows. LiNi as the positive electrode active material 1 / 3 Mn 1 / 3 Co 1 / 3 85 parts by weight of O2, 10 parts by weight of a conductive assistant (vapor-grown carbon fiber, manufactured by Showa Denko K.K.), and 5 parts by weight of a solid content of an NMP solution of polyvinylidene fluoride (PVDF) as a binder were weighed into a resin container. These were mixed in a hybrid mixer to prepare a slurry-like positive electrode mixture. This positive electrode mixture was applied to an aluminum foil (positive electrode current collector) with a doctor blade and dried at 110°C. As a result, a positive electrode in which a positive electrode layer was formed on one side of the aluminum foil was prepared. This positive electrode was roll-pressed to a predetermined density.

[0070] 95 parts by weight of natural graphite and 5 parts by weight of β-CD-Ad-EA as a binder and electrolyte were mixed. This mixture was dispersed in an unspecified amount of NMP to prepare a slurry-like negative electrode mixture. This negative electrode mixture was uniformly applied to a copper foil (negative electrode current collector), dried under reduced pressure for 12 hours in a 120°C atmosphere, and then pressure-molded using a roll press. This produced a negative electrode in which a negative electrode layer was formed on one side of the copper foil.

[0071] The prepared negative and positive electrodes and a separator (a microporous film made of polyethylene) were cut to a predetermined size. Then, the positive electrode, separator, and negative electrode were laminated in this order so that the positive electrode layer and the negative electrode layer faced each other with the separator in between to prepare a laminate. The laminate was fixed with tape so that the positive electrode, separator, and negative electrode would not shift. Aluminum foil (width 4 mm, length 40 mm, thickness 100 μm) and nickel foil (width 4 mm, length 40 mm, thickness 100 μm) were ultrasonically welded to the positive electrode and the negative electrode, respectively, as external lead terminals.

[0072] The laminate (battery element) was enclosed together with an electrolyte in a battery exterior made of an aluminum laminate material, and the battery was vacuum sealed to produce a liquid-based lithium-ion secondary battery. The electrolyte used was prepared by dissolving 1 mol / L of lithium hexafluorophosphate (LiPF6) as an electrolyte salt in a mixed solvent of equal volumes of ethylene carbonate (EC) and dimethyl carbonate (DMC).

[0073] [evaluation] (Peel strength measurement) The peel strength of the negative electrodes prepared in Examples 1 to 11 and Comparative Examples 1 to 5 was measured by the following method. The results are shown in Tables 1 to 3. One side of the double-sided tape was attached to the surface side of the negative electrode layer, and the other side was attached to a metal plate. The metal plate was fixed, and a portion of the negative electrode current collector where the negative electrode layer was not formed on the surface was connected to a load cell, and the metal part was moved vertically at a speed of 50 mm / min. The average load applied to the load cell at this time was divided by the width (2 cm) of the negative electrode layer to calculate the peel strength.

[0074] (Li ion conductivity measurement) The batteries obtained in Examples 1 to 11 and Comparative Examples 1 to 5 were subjected to measurement of Li-ion conductivity (room temperature) by the AC impedance method. A Solartron 1260 was used for the measurement, and the measurement conditions were an applied voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The results are shown in Tables 1 to 3. Each test cell was prepared as follows. First, the battery before charging was charged at a constant current of 0.1 C in an environment of 25°C ± 4°C until the terminal voltage per cell reached a set voltage, and then charged for 1 hour by constant current constant voltage charging, in which a constant voltage charge was performed to maintain the set voltage. After the initial charge, constant current constant voltage discharge was performed at 0.2 C for 10 hours to 4.2 V. Then, constant current charging was performed at a current value of 0.2 C to 4.0 V in an environment of 25 ± 4°C. The test cell used for conductivity measurement was thus prepared, and the above measurement was performed.

[0075] (Cycle test) For the batteries (test cells) produced in Examples 1 to 11 and Comparative Examples 1 to 5, a cycle of constant current / constant voltage charging at a current value of 1C for 2.5 hours to 4.2V and constant current discharging at a current value of 1C to 3.0V was repeated 300 times in an environment of 40°C. The capacity retention rate (%) was calculated by dividing the discharge capacity at the 300th cycle by the discharge capacity at the 5th cycle. This cycle test was performed on three test cells for each Example and Comparative Example, and the average value was calculated. The results are shown in Tables 1 to 3.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] As shown in Examples 1 to 11, it was confirmed that the all-solid-state battery using the binder of the present disclosure had good cycle characteristics. In particular, it was confirmed that the battery showed good cycle characteristics even when using a Si active material that expands and contracts greatly during charging and discharging.

[0080] In addition, as can be seen from Example 1 and Comparative Example 5, it was confirmed that the binder in the present disclosure is effective when used in a solid-state battery. This is believed to be due to the following reasons. The electrodes of liquid batteries are formed with a certain amount of voids so that the electrolyte can permeate. Therefore, the contact area between the negative electrode active materials is small, and the self-repairing property of the binder in the present disclosure is not fully utilized. [Explanation of symbols]

[0081] 1 ... Positive electrode layer 2 ... Negative electrode layer 3...Solid electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 6. Battery case 10...All-solid-state battery

Claims

1. An all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, At least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains a sulfide solid electrolyte and a host-guest type binder, The host-guest type binder has a monomer unit containing a cyclic host group and a monomer unit containing a guest group, the guest group is included in the cyclic host group, The host-guest type binder has a glass transition temperature (Tg) of 30° C. or lower.

2. The all-solid-state battery according to claim 1 , wherein the cyclic host group contains at least one of a cyclodextrin skeleton, a cyclophane skeleton, and a cucurbituril skeleton.

3. The all-solid-state battery according to claim 1 or 2, wherein the guest group contains an adamantyl group.

4. The all-solid-state battery according to claim 1 , wherein the negative electrode layer contains a negative electrode active material, the sulfide solid electrolyte, and the host-guest type binder.

5. The all-solid-state battery according to claim 4 , wherein the negative electrode active material is a Si-based active material.

Images