Negative electrode for all-solid-state battery, all-solid-state battery, and negative electrode active material for all-solid-state battery

Abstract

[Solution] A negative electrode for an all-solid-state battery comprising a negative electrode active material and a solid electrolyte, wherein the negative electrode active material comprises a carbon material having a planar spacing (d002) measured by XRD of 0.336 nm or more and less than 0.350 nm and a springback rate of 13% or more.

Description

Technology Field

[0001] The present disclosure relates to a negative electrode for an all-solid-state battery, an all-solid-state battery, and a negative electrode active material for an all-solid-state battery. Background Technology

[0002] Rechargeable lithium-ion rechargeable batteries are widely used as power sources for various electronic devices. Recently, the use of lithium-ion rechargeable batteries is also being considered as power sources for vehicles, such as electric vehicles and hybrid vehicles.

[0003] Most commercially available lithium-ion rechargeable batteries currently utilize a liquid electrolyte dissolved in a flammable organic solvent. Consequently, it is necessary to implement countermeasures, such as installing safety devices to suppress temperature rise in the event of a short circuit. Therefore, rechargeable batteries in which the electrolyte is in a solid state (all-solid-state batteries) are being proposed. All-solid-state batteries offer superior safety in the event of a short circuit compared to batteries using electrolytes containing organic solvents. For this reason, safety devices can be simplified, and it is believed that the manufacturing cost and productivity of rechargeable batteries are excellent.

[0004] All-solid-state batteries are mainly composed of a positive electrode containing a positive active material, a solid electrolyte layer, and a negative electrode containing a negative active material. Lithium titanate (LTO) is the mainstream negative active material for all-solid-state batteries, but the use of carbon materials such as graphite is also being considered (for example, see Japanese Patent Publication No. JP 2018-206487). The problem to be solved

[0005] Carbon materials are promising as negative electrode active materials for all-solid-state batteries in terms of increasing capacity and reducing costs, but there is room for improvement in cycle characteristics (the rate of retention of battery capacity after repeated charge-discharge cycles). Furthermore, from the perspective of increasing battery capacity, improvement in initial charge-discharge efficiency is also desired.

[0006] The present disclosure aims to provide, in light of the above circumstances, a negative electrode for an all-solid-state battery capable of manufacturing an all-solid-state battery having excellent cycle characteristics and initial charge / discharge efficiency, an all-solid-state battery having said negative electrode, and a negative electrode active material used in said all-solid-state battery. means of solving the problem

[0007] The means for solving the above problem include the following embodiments.

[0008] <1> Includes a negative electrode active material and a solid electrolyte, wherein the negative electrode active material has a plane spacing (d) measured by XRD. 002 A negative electrode for an all-solid-state battery comprising a carbon material having a length of 0.336 nm or more and less than 0.350 nm and a springback rate of 13% or more.

[0009] <2> The above carbon material is a negative electrode for an all-solid-state battery as described in <1>, having a volume average particle diameter of 5 μm to 30 μm.

[0010] <3> The BET specific surface area based on the nitrogen adsorption capacity of the above carbon material is 0.5 m 2 / g~10m 2 A negative electrode for an all-solid-state battery as described in <1> or <2>, with a g / g.

[0011] <4> A negative electrode for an all-solid-state battery as described in any one of <1> to <3>, wherein the mass ratio (negative electrode active material:solid electrolyte) of the negative electrode active material and the solid electrolyte included in the all-solid-state battery is 5:95 to 70:30.

[0012] <5> The above solid electrolyte is a sulfide solid electrolyte, a negative electrode for an all-solid-state battery as described in any one of <1> to <4>.

[0013] <6> A solid-state battery comprising a negative electrode for a solid-state battery as described in any one of <1> to <5>, a positive electrode, and a solid electrolyte layer disposed between the negative electrode for a solid-state battery and the positive electrode.

[0014] <7> Planar spacing measured by XRD (d002 A negative electrode active material for an all-solid-state battery, which is a carbon material having a length of 0.336 nm or more and less than 0.350 nm and a springback rate of 13% or more. Effects of the invention

[0015] According to the present disclosure, a negative electrode for an all-solid-state battery capable of manufacturing an all-solid-state battery having excellent cycle characteristics and initial charge / discharge efficiency, an all-solid-state battery having the negative electrode, and a negative electrode active material used in the all-solid-state battery are provided. Brief explanation of the drawing

[0016] [Fig. 1] This is a cross-sectional view schematically showing an example of the configuration of an all-solid-state battery. Specific details for implementing the invention

[0017] The following describes in detail embodiments for carrying out the present disclosure. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not mandatory unless specifically stated otherwise. The same applies to numerical values ​​and their ranges, and this does not limit the present invention.

[0018] In the present disclosure, the term “process” includes, in addition to processes independent from other processes, processes that cannot be clearly distinguished from other processes, provided that the purpose of such processes is achieved.

[0019] In the numerical range indicated by "~" in the present disclosure, the numerical values ​​listed before and after "~" are included as the minimum value and the maximum value, respectively.

[0020] In the numerical ranges described stepwise in the present disclosure, an upper or lower limit value described in one numerical range may be substituted with an upper or lower limit value of another numerical range described stepwise. Additionally, in the numerical ranges described in the present disclosure, an upper or lower limit value of said numerical range may be substituted with a value shown in the examples.

[0021] In the present disclosure, each component may include multiple types of the corresponding substance. Where multiple types of substances corresponding to each component exist in the composition, the content or content of each component refers to the content or content of the total of the corresponding multiple types of substances present in the composition, unless specifically determined otherwise.

[0022] In the present disclosure, particles corresponding to each component may be included in multiple types. If multiple types of particles corresponding to each component exist in the composition, the particle diameter of each component refers to the value of the mixture of the corresponding multiple types of particles existing in the composition, unless specifically determined otherwise.

[0023] In the present disclosure, the term “layer” includes cases where, when observing the region in which the layer exists, it is formed in the entire region, in addition to cases where it is formed only in a part of the region.

[0024] <Cathode for All-Solid State Batteries>

[0025] The negative electrode for an all-solid-state battery of the present disclosure (hereinafter also referred to simply as the negative electrode) comprises a negative electrode active material and a solid electrolyte, and the negative electrode active material has a plane spacing (d) measured by XRD measurement. 002 It includes a carbon material having a length of 0.336 nm or more and less than 0.350 nm, and a springback rate of 13% or more.

[0026] The all-solid-state battery using the above-mentioned cathode exhibits superior cycle characteristics compared to conventional all-solid-state batteries using carbon materials as the cathode active material. Although the reason is not necessarily clear, it is thought to be as follows.

[0027] An all-solid-state battery is mainly composed of a positive electrode containing a positive active material, a layer containing a solid electrolyte (hereinafter also referred to as a solid electrolyte layer), and a negative electrode containing a negative active material. In addition, to promote the conduction of ions to the negative electrode, a solid electrolyte is also included in the negative electrode, and the solid electrolyte and the negative active material are in contact within the negative electrode.

[0028] It is known that carbon materials exhibit significant volume fluctuations due to the absorption and release of ions. Consequently, in all-solid-state batteries using carbon materials as negative electrode active materials, repeated charging and discharging can lead to a decrease in the contact area with the solid electrolyte within the negative electrode and particle breakdown due to volume fluctuations, making it prone to degraded cycle performance.

[0029] In this regard, the carbon material used as the negative electrode active material in the present disclosure has a springback rate of 13% or more.

[0030] The springback rate of carbon materials is an indicator representing the degree to which a carbon material returns to its original state when pressure is released from a compressed state created by applying a predetermined pressure. The higher the springback rate, the easier it is to return from a compressed state to its original state.

[0031] Carbon materials with a springback rate of 13% or more are thought to be in a state where irreversible deformation, such as the destruction of the particle structure, is less likely to occur compared to carbon materials with a springback rate of less than 13%. As a result, it is thought that the contact area between the carbon material and the solid electrolyte is sufficiently maintained even when charging and discharging are repeated, and the degradation of cycle characteristics is suppressed.

[0032] In addition to the above, as a result of the inventors' review, the planar spacing (d) measured by XRD as a negative electrode active material 002 An all-solid-state battery using a carbon material with a thickness of less than 0.350 nm has a planar spacing (d) in XRD measurement 002It was found that the initial charge / discharge efficiency was superior compared to all-solid-state batteries using carbon materials of 0.350 nm or larger. Although the reason is not necessarily clear, it is thought that the lithium ions inserted between the carbon layers are in a state where it is difficult for them to escape.

[0033] (Cathode active material)

[0034] The negative electrode active material is a planar spacing (d) in X-ray diffraction (XRD) measurement. 002 ) includes a carbon material having a length of 0.336 nm or more and less than 0.350 nm (hereinafter also referred to as a specific carbon material).

[0035] interplanar spacing (d) of carbon material 002 ) is an indicator representing the degree of scattering in the crystal structure of carbon materials, and the interplanar spacing (d 002 Carbon materials with a thickness of less than 0.340 nm are classified as graphite-based, and the interplanar spacing (d 002 There are cases where carbon materials with a thickness of 0.340 nm or more are classified as non-graphite.

[0036] Among non-graphite carbon materials, the interplanar spacing (d) 002 Carbon materials with a thickness of 0.340 nm or more and less than 0.350 nm are classified as soft carbon (digraphitized carbon), and the interplanar spacing (d 002 Carbon materials with a thickness of 0.350 nm or more are sometimes classified as hard carbon (hard graphitized carbon).

[0037] interplanar spacing (d) of a specific carbon material 002 ) is greater than 0.336 nm in terms of suppressing volume fluctuations due to lithium ion absorption and release. The interplanar spacing (d) of a specific carbon material 002 ) may be 0.339nm or larger, 0.340nm or larger, 0.342nm or larger, or 0.343nm or larger.

[0038] interplanar spacing (d) of a specific carbon material 002The larger the value, the smaller the fluctuation in volume due to the absorption and release of lithium ions tends to be. For this reason, it is thought that even if charge and discharge are repeated, the particles are less likely to be destroyed, and the contact area with the solid electrolyte is maintained, so the degradation of cycle characteristics tends to be more suppressed.

[0039] interplanar spacing (d) of a specific carbon material 002 ) is not specifically limited to a range of 0.336 nm or more and less than 0.350 nm, and may be 0.349 nm or less, or 0.348 nm or less.

[0040] In the present disclosure, the interplanar spacing (d) of the carbon material 002 ) is measured as follows.

[0041] To correct the diffraction peak positions, a sample is prepared by mixing silicon powder as an internal standard material in a Menow mortar for 3 minutes such that the mass ratio of the carbon material to the silicon powder (carbon material:silicon powder) is 3:2. Then, X-rays are irradiated onto the sample under the following conditions, and the spectrum of the diffraction peaks corresponding to the (111) plane of silicon and the (002) plane of carbon is measured.

[0042] (Measurement conditions)

[0043] · Characteristic X-ray: CuKα rays

[0044] · Scan speed: 0.25˚ / min

[0045] · Diverging slit: 1˚

[0046] · Scattering slit: 1˚

[0047] · Light receiving slit: 0.15mm

[0048] The diffraction angle θ corresponding to the (111) plane of the measured silicon Si (111) , the diffraction angle corresponding to the (002) plane of carbon is θ C(002) Thus, from the Bragg equation (1), the plane spacing (d 002 Produces ).

[0049] In Equation (1), the theoretical value of the diffraction angle corresponding to the (111) plane of silicon is θ Si -theoretical(111) Let = 14.221. λ is the X-ray wavelength (0.15418 nm for CuKα rays).

[0050]

[0051] A specific carbon material included in the cathode has a plane spacing (d 002 Even if ) is the same as only one type, the face spacing (d 002 ) may be a combination of two or more different types.

[0052] The measurement of the springback rate of carbon materials is carried out as follows.

[0053] 3,000 (±0.005) g of carbon material is filled into a cylindrical powder molding die (diameter 15.0 mm). Using an autograph, the density of the carbon material filled in the die is 1.65 g / cm³ 3 Uniaxial pressure is applied until it is reached. The density of the carbon material is 1.65 g / cm³ 3 After reaching [value], reduce the pressure until it becomes 0N, and hold it in that state (0N state) for 30 seconds. After holding for 30 seconds, pressurize the sample using an autograph, and the density ρ of the sample when the pressure reaches 2N after (g / cm 3 Measure ). From the obtained value, calculate the springback rate using the following formula.

[0054] Springback rate (%) = {(1.65 - ρ after ) / 1.65}×100

[0055] From the perspective of cycle characteristics, the springback rate of a specific carbon material may be 14% or more, 15% or more, 17% or more, 18% or more, or 20% or more.

[0056] The upper limit of the springback rate of a specific carbon material is not specifically limited, but it may be 65% or less, 60% or less, 50% or less, 40% or less, or 35% or less.

[0057] Methods for controlling the springback rate of carbon materials include controlling the degree of graphitization, particle shape, and particle diameter distribution of the carbon material, and reducing the pores of the carbon material.

[0058] It is preferable that the specific carbon material be in a particulate form. The specific carbon material in a particulate form may be unaggregated primary particles or aggregated secondary particles.

[0059] When a specific carbon material has a particle shape, it is preferable that the volume average particle diameter be 5 μm to 30 μm. If the volume average particle diameter of the specific carbon material is 5 μm or more, the initial charge / discharge efficiency tends to improve, and if it is 30 μm or less, the input / output characteristics tend to improve.

[0060] The volume average particle diameter of a specific carbon material may be 8 μm or more, 10 μm or more, or 12 μm or more. The volume average particle diameter of a specific carbon material may be 28 μm or less, 26 μm or less, or 24 μm or less.

[0061] In the present disclosure, the volume average particle diameter of the particle is defined as the particle diameter (median diameter, D50) at which the accumulation from the small diameter side in the volume-based particle size distribution measured by the laser diffraction and scattering method reaches 50%.

[0062] The volume average particle diameter can be measured, for example, by using a laser diffraction and scattering type particle size measuring device on particles suspended in water.

[0063] Certain carbon materials have a BET specific surface area of ​​0.5 m² based on nitrogen adsorption capacity. 2 / g~10 m2 It is desirable that it be / g.

[0064] The BET specific surface area of ​​a specific carbon material is 0.5 m² 2 If it is greater than / g, I / O characteristics tend to improve, and 10m 2 If it is 1 / g or less, the initial charge / discharge efficiency tends to improve.

[0065] The BET specific surface area of ​​a specific carbon material is 0.6 m 2 It can be more than / g, and 0.7m 2 It can be more than / g, and 0.8m 2 It may be greater than / g. The BET specific surface area of ​​a specific carbon material is 8m 2 / g or less is acceptable, and 6m 2 / g or less is acceptable, and 5m 2 / g or less is acceptable.

[0066] The BET specific surface area of ​​a specific carbon material is calculated from its nitrogen adsorption capacity in accordance with JIS Z 8830:2013. As an evaluation device, for example, the AUTOSORB-1 (product name) manufactured by QUANTACHROME can be used. When measuring the BET specific surface area, a pretreatment to remove moisture by heating is performed, as it is believed that moisture adsorbed on the surface and inside the sample affects the gas adsorption capacity. After performing the pretreatment, the evaluation temperature is set to 77K, and the measurement is performed with the evaluation pressure range set to less than 1 relative pressure (equilibrium pressure relative to saturated vapor pressure).

[0067] In the pretreatment, a measuring cell containing 0.05g of a measurement sample is depressurized to 10 Pa or less using a vacuum pump. Then, it is heated to 110°C and held at 110°C for at least 3 hours. After holding, it is naturally cooled to room temperature (25°C) while maintaining the depressurized state.

[0068] The mass ratio of the cathode active material and the solid electrolyte (cathode active material:solid electrolyte) included in the cathode is preferably 5:95 to 70:30, more preferably 10:90 to 50:50, and even more preferably 15:85 to 40:60.

[0069] The negative electrode active material may include only a specific carbon material, or it may include a negative electrode active material other than the specific carbon material.

[0070] As a negative electrode active material other than a specific carbon material, the planar spacing (d) measured by XRD 002 ) carbon materials with a diameter of 0.350 nm or larger, carbon materials with a springback rate of less than 13%, Nb2O5, Li4Ti5O 12 Examples include oxides such as SiO, metals or metalloids such as In, Al, Si, and Sn.

[0071] When the cathode active material comprises a specific carbon material and a cathode active material other than the specific carbon material, it is preferable that the proportion of the specific carbon material be 50 mass% or more of the total cathode active material, more preferable that it be 70 mass% or more, and more preferable that it be 80 mass% or more.

[0072] When the cathode active material comprises a specific carbon material and a cathode active material other than the specific carbon material, the proportion of the specific carbon material may be 99 mass% or less of the total cathode active material, or 95 mass% or less.

[0073] The amount of cathode active material included in the cathode may be 10 mass% or more of the total material constituting the cathode (excluding cathode current collectors and volatile components), 20 mass% or more, or 30 mass% or more.

[0074] The amount of cathode active material included in the cathode may be 95 mass% or less, 90 mass% or less, or 80 mass% or less of the total material constituting the cathode (excluding the cathode current collector and volatile components).

[0075] (Solid electrolyte)

[0076] The type of solid electrolyte included in the cathode is not particularly limited and can be selected from materials that can be used as electrolytes for all-solid-state batteries. Representative solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes.

[0077] From the perspective of high input, sulfide solid electrolytes and polymer solid electrolytes are preferred, and from the perspective of thermal stability, sulfide solid electrolytes are more preferred.

[0078] Solid electrolytes may be used in combination of one type or two or more types.

[0079] Examples of sulfide solid electrolytes include compounds containing a metal element that becomes a conductive ion and sulfur (S).

[0080] Examples of metallic elements include Li, Na, K, Mg, and Ca. Among these, Li is preferred as a metallic element.

[0081] The sulfide solid electrolyte may include at least one selected from the group consisting of Li and S, and P, Si, Ge, Al, and B. Among these, a sulfide solid electrolyte containing Li, S, and P (hereinafter also referred to as an LPS-type sulfide solid electrolyte) is preferred.

[0082] In terms of ionic conductivity, sulfide solid electrolytes may contain halogen elements such as Cl, Br, and I. In terms of chemical stability, sulfide solid electrolytes may contain oxygen (O).

[0083] Specifically as LPS-type sulfide solid electrolytes, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiBr-LiI-Li2S-P2S5, Li2S-P2S5-Z m S n (In the formula, m and n are each positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y Examples include (where x and y in the formula are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In).

[0084] In the above description, "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using Li2S and P2S5 as raw materials, and the same applies to other descriptions.

[0085] Among LPS-type sulfide solid electrolytes, a sulfide solid electrolyte obtained using Li2S and P2S5 is preferred, and a sulfide solid electrolyte satisfying the following formula is more preferred.

[0086] Li3 +x+ 5y P1 - y S4(0<x≤0.6, 0<y≤0.2)

[0087] As an oxide solid electrolyte, NASICON(Na3Zr2PSi2O 12 Examples include compounds having a crystal structure of the ) type. Compounds having a NASICON-type crystal structure have high ionic conductivity and excellent stability in the atmosphere.

[0088] Examples of compounds having a NASICON-type crystal structure include lithium-containing phosphates. As phosphates, lithium phosphate complexes with Ti (e.g., Li1 + x Al x Ti2 -x Examples include (PO4)3), compounds in which all or part of the Ti in the above-mentioned complex lithium phosphate salt is substituted with tetravalent transition metals such as Ge, Sn, Hf, Zr, or trivalent transition metals such as Al, Ga, In, Y, La.

[0089] As a compound having a NASICON-type crystal structure, specifically, a Li-Al-Ge-PO-based material (Li 1+x Al x Ge 2-x (PO4)3), Li-Al-Zr-PO-based materials (Li1 + x Al x Zr2 -x (PO4)3), Li-Al-Ti-PO-based materials (Li 1+x Al x Ti 2-x (PO4)3) etc. can be cited.

[0090] Examples of polymeric solid electrolytes include mixtures (complexes) of polymeric compounds and electrolyte salts.

[0091] Specifically, examples of polymer compounds include polyether-based polymer compounds such as polyethylene oxide (PEO) and polypropylene oxide (PPO), polyamine-based polymer compounds such as polyethyleneimine (PEI), and polysulfide-based polymer compounds such as polyalkylene sulfide (PAS). Among these, polyether-based polymer compounds are preferred.

[0092] Specifically, as electrolyte salts, examples include lithium salts such as LiPF6, LiBF4, Li[FSI], Li[TFSI], Li[f3C], Li[BOB], LiClO4, LiBF3(CF3), LiBF3(C2F5), LiBF3(C3F7), LiBF3(C4F9), LiC(SO2CF3)3, CF3SO2OLi, CF3COOLi, and RCOOLi (where R in the formula is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group). Among these, imide-based lithium salts such as Li[TFSI] and Li[FSI] are preferred.

[0093] In the above, [FSI] means bis(fluorosulfonyl)imide anone, [TFSI] means bis(trifluoromethanesulfonyl)imide anone, [BOB] means bis(oxalate borate anone, and [f3C] means tris(fluorosulfonyl)carbon anone.

[0094] The amount of polymer compound in a mixture of polymer compound and electrolyte salt may be 1 mole or more, 5 moles or more, or 10 moles or more per 1 mole of electrolyte salt.

[0095] The amount of polymer compound in a mixture of polymer compound and electrolyte salt may be 50 moles or less, 40 moles or less, or 30 moles or less per 1 mole of electrolyte salt.

[0096] The polymeric solid electrolyte may be a polymeric compound having ion conductivity (hereinafter also referred to as an ion-conducting polymeric compound).

[0097] The ion-conducting polymer compound may be in a state where a base polymer is doped with a dopant. Although the base polymer typically tends not to exhibit ion conductivity, it is hypothesized that when a dopant is doped and the base polymer is oxidized or reduced, pairs of positive and negative charges are formed within the structure of the base polymer, thereby forming an ion conduction path.

[0098] The base polymer is not particularly limited as long as it is a polymer that can be oxidized or reduced by a dopant. Specifically, examples of base polymers include polyphenylene sulfide (PPS), poly(p-phenylene oxide) (PPO), polyetheretherketone (PEEK), polyphthalamide (PPA), polythiophene, polyaniline, polyacetylene, polythiazyl, polydiacetylene, polypyrrole, polyparaphenylene, polynaphtylene, polyanthracene, etc.

[0099] The dopant may be either an acceptor, which is an electron-accepting dopant, or a donor, which is an electron-donating dopant. In other words, the dopant may be either an oxidizing agent or a reducing agent.

[0100] Examples of acceptors (oxidizers) include halogens such as bromine, iodine, and chlorine; Lewis acids such as BF3, PF5, AsF5, and SbF5; proton acids such as HNO3, H2SO4, HClO4, HF, HCl, FSO3H, and CF3SO3H; transition metal halides such as FeCl3, MoCl5, WCl5, SnCl4, MoF5, RuF5, TaBr4, TaBr5, and SnI4; organic compounds such as 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone (chloranyl), tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE); and oxygen. The acceptor may be used as a single type or as two or more types.

[0101] Examples of donors (reducing agents) include alkali metals such as Li, Na, K, Rb, and Cs, alkaline earth metals such as Be, Mg, and Ca, ammonium salts such as tetraethylammonium salt and tetrabutylammonium salt, and hydrogen. The donor may be used as a single type or as two or more types.

[0102] The mass ratio of the base polymer to the dopant (base polymer:dopant) is preferably 99:1 to 20:80, more preferably 95:5 to 30:70, and even more preferably 90:10 to 50:50.

[0103] Methods for doping a base polymer with a dopant include evaporating or sublimating the dopant and bringing the base polymer into contact with the vapor. In this case, the base polymer may be molded into a sheet shape. The conditions for evaporating or sublimating the dopant can be set according to the properties of the dopant. Doping of the base polymer with the dopant may be carried out by electrochemical treatment.

[0104] The amount of solid electrolyte included in the cathode may be 1 mass% or more of the total material constituting the cathode (excluding the cathode current collector and volatile components), 5 mass% or more, or 10 mass% or more.

[0105] The amount of solid electrolyte contained in the cathode may be 40 mass% or less of the total material constituting the cathode (excluding the cathode current collector and volatile components), 30 mass% or less, or 20 mass% or less.

[0106] The solid electrolyte may be in the form of particles. In this case, the volume average particle diameter of the solid electrolyte is preferably 0.1 μm to 100 μm. If the volume average particle diameter of the solid electrolyte is 0.1 μm or more, it tends to mix easily with carbon materials, and if it is 100 μm or less, the battery capacity tends to be sufficiently obtained.

[0107] The volume average particle diameter of the solid electrolyte may be 0.2 μm or more, 0.4 μm or more, or 0.5 μm or more.

[0108] The volume average particle diameter of the solid electrolyte may be 80 μm or less, 60 μm or less, or 50 μm or less.

[0109] The cathode may include components other than the cathode active material and solid electrolyte as needed. For example, it may include conductive materials, binders, etc.

[0110] Examples of conductive materials include carbon materials such as acetylene black, carbon black, and carbon fiber (except for the cathode active material described above). The conductive material included in the cathode material may be one type or two or more types.

[0111] The amount of conductive material included in the cathode may be 0.1 mass% or more, 0.3 mass% or more, or 0.5 mass% or more of the total material constituting the cathode (excluding the cathode current collector and volatile components).

[0112] The amount of conductive material included in the cathode may be 5 mass% or less of the total material constituting the cathode (excluding the cathode current collector and volatile components), 3 mass% or less, or 1 mass% or less.

[0113] Examples of binders include polymers having monomers such as tetrafluoroethylene, acrylic acid, maleic acid, and ethyl methacrylate as polymerization components, styrene-butadiene rubber, isoprene rubber, acrylic rubber, etc.

[0114] In cases where the cathode contains components other than the cathode active material and solid electrolyte, the total amount of the cathode active material and solid electrolyte may be 99.9 mass% or less, 99 mass% or less, or 97 mass% or less of the total material constituting the cathode (excluding the cathode current collector and volatile components).

[0115] In cases where the cathode contains components other than the cathode active material and solid electrolyte, the total amount of the cathode active material and solid electrolyte may be 85 mass% or more, 90 mass% or more, or 92 mass% or more of the total material constituting the cathode (excluding the cathode current collector and volatile components).

[0116] (Cathode current collector)

[0117] The cathode may be formed such that a layer containing the material constituting the cathode described above (hereinafter also referred to as the cathode active material layer) is formed on the cathode current collector.

[0118] The material of the cathode current collector is not particularly limited, but a conductive material containing copper (Cu) is preferred. Examples of conductive materials containing copper include foil-shaped materials such as electrolytic copper foil, rolled copper foil, and copper alloy foil, as well as plate-shaped materials and mesh-shaped materials.

[0119] The thickness of the negative active material layer formed on the negative current collector is not particularly limited and can be selected according to the size, performance, etc. of the all-solid-state battery including the negative electrode.

[0120] From the perspective of conductivity, the thickness of the negative active material layer may be 10 μm or more, 15 μm or more, or 20 μm or more.

[0121] In terms of suppressing deviation in charge and discharge caused by deviation in the charge level of the cathode active material near the surface of the cathode, the thickness of the cathode active material layer may be 100 μm or less, 75 μm or less, or 50 μm or less.

[0122] All-solid-state battery

[0123] The all-solid-state battery of the present disclosure comprises the aforementioned negative electrode, a positive electrode, and a solid electrolyte layer disposed between the negative electrode and the positive electrode.

[0124] Figure 1 is a cross-sectional view schematically illustrating an example of the configuration of an all-solid-state battery.

[0125] The all-solid-state battery (100) shown in FIG. 1 comprises a negative electrode (16) including a negative electrode active material layer (12) and a negative electrode current collector (14), a positive electrode (17) including a positive electrode active material layer (13) and a positive electrode current collector (15), and a solid electrolyte layer (11) disposed between the positive electrode (16) and the negative electrode (17).

[0126] In one embodiment, the negative electrode active material layer (12) comprises a negative electrode active material and a solid electrolyte identical to the solid electrolyte included in the solid electrolyte layer (11), and the positive electrode active material layer (13) comprises a positive electrode active material and a solid electrolyte identical to the solid electrolyte included in the solid electrolyte layer (11).

[0127] (anode)

[0128] The composition of the positive electrode is not particularly limited and can be selected from those generally used as positive electrodes for all-solid-state batteries. In one embodiment, the positive electrode comprises a positive electrode active material and a solid electrolyte.

[0129] Examples of positive electrode active materials include lithium transition metal compounds such as lithium transition metal oxides and lithium transition metal phosphates.

[0130] Examples of lithium transition metal oxides include lithium manganate, lithium nickelate, lithium cobaltate, and lithium transition metal oxides in which a portion of the transition metals such as Mn, Ni, and Co contained in these lithium transition metal oxides is substituted with one or more other transition metals, or metallic elements (typical elements) such as Mg and Al. That is, lithium transition metal oxides are LiM 1 O2 or LiM 1 2O4(M 1 It may be a compound represented by (containing at least one type of transition metal). Specifically as a lithium transition metal oxide, Li(Co 1 / 3 Ni 1 / 3 Mn 1 / 3 )O2, LiNi 1 / 2 Mn 1 / 2 O2, LiNi1 / 2Mn3 / Examples include 2O4.

[0131] In terms of improving energy density, it is preferable that the lithium transition metal oxide be a compound represented by the following formula.

[0132] Li a Ni bCo c M 2 d O2 +e

[0133] During the meal, M 2 It is at least one selected from the group consisting of Al, Mn, Mg and Ca, and a, b, c, d and e are numbers satisfying 0.2≤a≤1.2, 0.5≤b≤0.9, 0.1≤c≤0.4, 0≤d≤0.2, and -0.2≤e≤0.2, respectively, and also satisfying b+c+d=1.

[0134] Specifically as lithium transition metal phosphates, LiFePO4, LiMnPO4, and LiMn x M 3 1 -x PO4(0.3≤x≤1, M 3 (It is at least one element selected from the group consisting of Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr) can be cited.

[0135] The positive active material included in the positive electrode may be of only one type or two or more types.

[0136] The positive active material is preferably in the form of particles. The particles may be unassembled primary particles or assembled secondary particles.

[0137] The volume average particle diameter of the positive active material may be 0.1 μm or more, 1 μm or more, or 5 μm or more.

[0138] The volume average particle diameter of the positive active material may be 30 μm or less, 25 μm or less, or 20 μm or less.

[0139] The amount of positive active material included in the positive electrode may be 60 mass% or more of the total material constituting the positive electrode (excluding positive current collectors and volatile components), 65 mass% or more, or 70 mass% or more.

[0140] The amount of positive active material included in the positive electrode may be 99 mass% or less of the total material constituting the positive electrode (excluding the positive current collector and volatile components), 95 mass% or less, or 90 mass% or less.

[0141] As a solid electrolyte included in the anode, the solid electrolyte that may be included in the cathode described above can be cited.

[0142] The solid electrolyte included in the anode may be the same or different from the solid electrolyte included in the cathode, but it is preferable that it be the same.

[0143] The amount of solid electrolyte included in the anode may be 1 mass% or more of the total material constituting the anode (excluding the anode current collector and volatile components), 5 mass% or more, or 10 mass% or more.

[0144] The amount of solid electrolyte included in the anode may be 40 mass% or less of the total material constituting the anode (excluding the anode current collector and volatile components), 30 mass% or less, or 20 mass% or less.

[0145] The anode may include components other than the anode active material and solid electrolyte as needed. For example, it may contain conductive materials, binders, etc. Examples of conductive materials and binders include those that may be included in the aforementioned cathode.

[0146] In cases where the anode contains components other than the anode active material and solid electrolyte, the total amount of the anode active material and solid electrolyte may be 99.9 mass% or less, 99 mass% or less, or 97 mass% or less of the total material constituting the anode (excluding the anode current collector and volatile components).

[0147] In cases where the anode contains components other than the anode active material and solid electrolyte, the total amount of the anode active material and solid electrolyte may be 85 mass% or more, 90 mass% or more, or 92 mass% or more of the total material constituting the anode (excluding the anode current collector and volatile components).

[0148] (Bipolar house whole)

[0149] The positive electrode may be formed such that a layer containing the material constituting the above-described positive electrode (hereinafter also referred to as the positive electrode active material layer) is formed on the positive electrode current collector.

[0150] The types of positive current collectors are not particularly limited and may include metals such as aluminum, stainless steel, and titanium, as well as thin materials, plate materials, and mesh-shaped materials containing carbon.

[0151] The thickness of the positive active material layer formed on the positive current collector is not particularly limited and can be selected according to the size, performance, etc. of the all-solid-state battery.

[0152] From the perspective of conductivity, the thickness of the positive active material layer may be 10 μm or more, 15 μm or more, or 20 μm or more.

[0153] From the perspective of reducing the volume of the anode, the thickness of the anode active material layer may be 100 μm or less, 75 μm or less, or 50 μm or less.

[0154] (Solid electrolyte layer)

[0155] The solid electrolyte layer functions to mediate the movement of ions between the anode and the cathode, as well as to electrically insulate the anode and the cathode.

[0156] As a solid electrolyte included in the solid electrolyte layer, examples include solid electrolytes that may be included in the aforementioned cathode and anode.

[0157] The solid electrolyte included in the solid electrolyte layer may be the same as or different from the solid electrolyte included in the cathode and anode, and it is preferable that it be the same.

[0158] The amount of solid electrolyte included in the solid electrolyte layer may be 30 mass% or more of the total material constituting the solid electrolyte layer (excluding volatile components), 40 mass% or more, or 50 mass% or more.

[0159] The amount of solid electrolyte included in the solid electrolyte layer may be 100 mass% or less of the total material constituting the solid electrolyte layer (excluding volatile components), 99 mass% or less, or 95 mass% or less.

[0160] The solid electrolyte layer may include components other than the solid electrolyte as needed. For example, it may contain a binder. Examples of binders include those that may be included in the aforementioned cathode.

[0161] The amount of components other than the solid electrolyte included in the solid electrolyte layer may be 1 mass% or more of the total material constituting the solid electrolyte layer (excluding volatile components), 3 mass% or more, or 5 mass% or more.

[0162] The amount of components other than the solid electrolyte included in the solid electrolyte layer may be 50 mass% or less, 40 mass% or less, or 30 mass% or less of the total material constituting the solid electrolyte layer (excluding volatile components).

[0163] The thickness of the solid electrolyte layer is not particularly limited and can be selected depending on the size, performance, etc. of the all-solid-state battery.

[0164] From the perspective of improving the strength and safety of the all-solid-state battery, the thickness of the solid electrolyte layer may be 5 μm or more, 10 μm or more, or 15 μm or more.

[0165] From the perspective of reducing internal resistance and high current characteristics of an all-solid-state battery, the thickness of the solid electrolyte layer may be 200 μm or less, 150 μm or less, or 100 μm or less.

[0166] <Cathode Active Material for All-Solid-State Batteries>

[0167] The negative electrode active material for an all-solid-state battery of the present disclosure has a plane spacing (d) measured by XRD. 002 It is a carbon material with a length of 0.336 nm or more and less than 0.350 nm, and a springback rate of 13% or more.

[0168] An all-solid-state battery using the above-mentioned negative electrode active material has superior cycle characteristics compared to a conventional all-solid-state battery using carbon materials as the negative electrode active material.

[0169] The above-mentioned cathode active material is used, for example, in the manufacture of the aforementioned cathode and all-solid-state battery.

[0170] The details and preferred embodiment of the above-described cathode active material are the same as the details and preferred embodiment of the cathode active material included in the cathode described above.

[0171] Examples

[0172] The present disclosure will be explained more specifically below by way of examples, but the present disclosure is not limited to these examples.

[0173] <Fabrication of All-Solid-State Batteries>

[0174] Planar spacing (d) measured by XRD 002 Carbon materials 1 to 8 as cathode active materials, each having values ​​shown in Table 1 for ) and springback rates, and a solid electrolyte were mixed such that the mass ratio (carbon material:solid electrolyte) was the value shown in Table 1.

[0175] As a solid electrolyte, a sulfide solid electrolyte obtained from Li2S (75 mol%) and P2S5 (25 mol%) (indicated as LPS in Table 1) and a polymer solid electrolyte obtained from a mixture (complex) obtained by mixing polyethylene oxide and Li [FSI] as an electrolyte salt in a molar ratio (polyethylene oxide:electrolyte salt) of 20:1 were used (indicated as PEO in Table 1).

[0176] A mixture obtained by mixing a carbon material and a solid electrolyte was weighed such that the amount of carbon material included in the mixture was calculated by the method described below, and pressure was applied to produce a disc-shaped pellet (thickness 3 mm, diameter 10 mm) with a relative density of 90% or more, which was used as a cathode.

[0177] A disc-shaped pellet (thickness 5 mm, diameter 10 mm) with a relative density of 95% or more was prepared using the same solid electrolyte used to make the cathode, and was used as a solid electrolyte layer.

[0178] A negative electrode, a solid electrolyte layer, and a lithium-indium alloy foil (counter electrode) attached to a Cu mesh were stacked in this order, placed inside a CR2032 type coin cell container, and sealed by sealing the top of the battery container through an insulating gasket to produce a coin-type half cell as an all-solid-state battery for evaluation.

[0179] Details of carbon materials 1 to 8 are shown below.

[0180] Carbon material 1: A sample prepared by filling a graphite crucible with coke A, which was granulated to have a volume average particle diameter of 20 μm, and holding it at a temperature of 3000°C under an inert atmosphere for 5 hours was designated as carbon material 1.

[0181] Carbon material 2: A sample prepared by filling a graphite crucible with coke B, which was set to have a volume average particle diameter of 16 μm, and holding it at a temperature of 1000°C under an inert atmosphere for 5 hours was designated as carbon material 2.

[0182] Carbon material 3: A sample prepared by filling a graphite crucible with coke B, which was set to have a volume average particle diameter of 9 μm, and holding it at a temperature of 3000°C under an inert atmosphere for 5 hours was designated as carbon material 3.

[0183] Carbon Material 4: Coke B, set to a volume-average particle diameter of 16 μm, was filled into a graphite crucible and heated to 1000°C under an inert atmosphere for 5 hours. Afterward, the sample was prepared by further classification to remove fine particles. This sample was designated as Carbon Material 4.

[0184] Carbon Material 5: Coke C and petroleum pitch, prepared to have a volume-average particle diameter of 15 μm, were mixed in a mass ratio of 97:3 (Coke C:Petroleum Pitch) and molded into a block shape. Afterward, the mixture was filled into a graphite crucible, heated to 3000°C under an inert atmosphere for 5 hours, and then cooled. The block was then manually loosened and sieved to produce a sample. This sample was designated as Carbon Material 5.

[0185] Carbon material 6: Coke B, ground to have volume-average particle diameters of 12 μm and 20 μm, was mixed in a mass ratio of 50:50 (12 μm:20 μm). Afterward, the mixture was filled into a graphite crucible and heated to 1000°C under an inert atmosphere for 5 hours to produce a sample. This sample was designated as carbon material 6.

[0186] Carbon Material 7: Coke B and petroleum pitch, prepared to have a volume-average particle diameter of 23 μm, were mixed in a mass ratio of 90:10 (Coke B:Petroleum Pitch) and molded into a block shape. Subsequently, the mixture was filled into a graphite crucible, heated to 3000°C under an inert atmosphere for 5 hours, and then cooled. After cooling, the block was crushed and sieved to obtain a powder. This powder and petroleum pitch were mixed in a mass ratio of 90:10 (Powder:Petroleum Pitch). This mixture was filled into a graphite crucible and heated to 1000°C under an inert atmosphere for 5 hours to produce a sample. This sample was designated as Carbon Material 7.

[0187] Carbon material 8: Coke A, which was prepared so that the volume average particle diameter was 16 μm, was designated as carbon material 8.

[0188] The details of coke A~C are shown below.

[0189] Coke A: Petroleum coke with a volume-average particle diameter of 18 μm

[0190] Coke B: Coal-based coke with a volume-average particle diameter of 14 μm

[0191] Coke C: Petroleum coke with a volume-average particle diameter of 7 μm

[0192] <Method for Calculating the Amount of Carbon Material in a Mixture>

[0193] (1) Carboxymethyl cellulose (CMC) as a thickener and styrene-butadiene rubber (SBR) as a binder were added to the carbon material used in the examples and comparative examples. The mass ratio of the carbon material:CMC:SBR was set to 98:1:1. A slurry was prepared by adding purified water, which is a dispersion solvent, to the mixture and kneading it. A predetermined amount (5 mg / cm²) of this slurry was applied substantially evenly and homogeneously to both sides of a rolled copper foil with a thickness of 10 μm, which serves as a current collector for the cathode. 2 A cathode plate was fabricated by coating. The density of the cathode active material layer of the cathode plate was 1.3 g / cm³. 3 did it.

[0194] (2) A coin-type battery was produced in which a single layer separator of polyethylene with a thickness of 30 μm (product name: Hypo, manufactured by Asahi Kasei Co., Ltd., “Hypo” is a registered trademark) was inserted between a negative plate (mass of carbon material: 7.54 mg) punched into a circle with a diameter of 14 mm and a Li metal plate punched into a circle with a diameter of 15 mm.

[0195] As a non-aqueous electrolyte for a coin-type battery, a mixture of cyclic carbonate ethylene carbonate (EC), chain carbonates dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 2:3:2 was used, in which lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1.2 mol / L as a lithium salt (electrolyte), and vinylene carbonate (VC) was added at a concentration of 1.0 mass%.

[0196] (3) The coin-type battery produced has a voltage of 0V (vs. Li / Li) at 0.2CA under conditions of 25℃. + Constant current charging up to ), and 0V (vs. Li / Li + From the point at which it reached ) constant voltage charging (initial charge) until the current value became 0.01CA at that voltage. Afterwards, it was discharged to 1.5V with a constant current of 0.2CA (initial discharge), and the initial discharge capacity (mAh) was measured. A 30-minute rest period was inserted between the charge and discharge.

[0197] (4) From the measured initial discharge capacity (YmAh) and the mass of carbon material (7.54mg) contained in the negative plate, the mass of carbon material (Xmg) at which the discharge capacity (designed battery capacity) of the coin-type battery becomes 0.3mAh was calculated using the following formula. The calculated mass of carbon material was used as the mass of carbon material in the mixture used to manufacture the all-solid-state battery.

[0198] X(mg)=(7.54(mg)×0.3(mAh)) / Y(mAh)

[0199] <Capacity Evaluation of All-Solid State Batteries>

[0200] As an indicator to determine whether the all-solid-state battery operates as designed, the ratio of the initial discharge capacity to the battery design capacity was calculated as follows.

[0201] Under conditions of 25°C, the all-solid-state battery was charged with a constant current to -0.57V (vs. Li / In) at a current value equivalent to 0.05 CA. Afterward, the all-solid-state battery was charged with a constant voltage until decayed at a current value equivalent to 0.005 CA. The capacity at this time was set as the initial charge capacity (mAh). After standing in this state for 30 minutes, the all-solid-state battery was discharged with a constant current to 1.0V (vs. Li / In) at a current value equivalent to 0.05 CA. The capacity at this time was set as the initial discharge capacity (mAh) of the all-solid-state battery.

[0202] From the initial discharge capacity and battery design capacity (0.3mAh) of the obtained all-solid-state battery, the capacity evaluation (%) was calculated using the following formula. The results are shown in Table 1.

[0203] Capacity Rating (%) = (Initial Discharge Capacity of Solid-State Battery / Design Capacity of Battery) × 100

[0204] <Measurement of Capacity Retention Rate and First Charge / Discharge Efficiency of All-Solid State Batteries>

[0205] The all-solid-state battery was charged and discharged 10 times under the same conditions as the measurement of the initial discharge capacity, and the 10th discharge capacity was measured. From the obtained values, the capacity retention rate (%) and the initial charge-discharge efficiency (%) were calculated using the following formula. The results are shown in Table 1.

[0206] Capacity retention rate (%) = (10th discharge capacity (mAh) / Initial discharge capacity (mAh)) × 100

[0207] Initial charge / discharge efficiency (%) = (Initial discharge capacity (mAh) / Initial charge capacity (mAh)) × 100

[0208]

[0209] As shown in Table 1, the plane spacing (d) in XRD measurements 002 The all-solid-state battery of the example using a carbon material having a diameter of 0.336 nm or more and less than 0.350 nm and a springback rate of 13% or more as the negative electrode active material exhibits good capacity evaluation and capacity retention rate, and also has excellent initial charge / discharge efficiency.

[0210] Planar spacing (d) in XRD measurement 002 The all-solid-state battery of Comparative Example 1, which uses a carbon material with a diameter of 0.336 nm or more and less than 0.350 nm but a springback rate of less than 13% as the negative electrode active material, has a capacity evaluation and capacity retention rate that are inferior to those of the example.

[0211] Although the springback rate is 13% or higher, the plane spacing (d) in XRD measurement 002 The all-solid-state battery of Comparative Example 2, which uses a carbon material with a diameter of 0.350 nm as the negative electrode active material, has an initial charge / discharge efficiency that is inferior to that of the example.

[0212] The disclosure of Japanese Patent Application No. 2020-215777 is incorporated herein by reference in its entirety.

[0213] All documents, patent applications, and technical specifications described in this specification are incorporated herein by reference to the same extent as they are specifically and individually recorded in which they are incorporated by reference.

Claims

Claim 1 It comprises a negative electrode active material and a solid electrolyte, wherein the negative electrode active material has a plane spacing (d) measured by XRD. 002 A negative electrode for an all-solid-state battery comprising a carbon material having a length of 0.339 nm or more and less than 0.350 nm and a springback rate of 13% or more. Claim 2 The negative electrode for an all-solid-state battery according to claim 1, wherein the carbon material is a particle with a volume average particle diameter of 5 μm to 30 μm. Claim 3 In claim 1 or claim 2, the BET specific surface area based on the nitrogen adsorption capacity of the carbon material is 0.5 m² 2 / g~10m 2 / g, negative electrode for all-solid-state batteries. Claim 4 A negative electrode for an all-solid-state battery according to claim 1 or claim 2, wherein the mass ratio of the negative electrode active material to the solid electrolyte (negative electrode active material: solid electrolyte) is 5:95 to 70:

30. Claim 5 A negative electrode for an all-solid-state battery according to claim 1 or claim 2, wherein the solid electrolyte is a sulfide solid electrolyte. Claim 6 A solid-state battery comprising a negative electrode for a solid-state battery as described in claim 1 or claim 2, a positive electrode, and a solid electrolyte layer disposed between the negative electrode for a solid-state battery and the positive electrode. Claim 7 Planar spacing (d) in XRD measurement 002 A negative electrode active material for an all-solid-state battery, which is a carbon material having a length of 0.339 nm or more and less than 0.350 nm and a springback rate of 13% or more.

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