Electrode, battery using same, and method for producing electrode

Abstract

An electrode 10 according to the present disclosure comprises an electrode active material and a solid electrolyte that is in contact with the electrode active material, wherein the electrode active material contains an oxide containing titanium but not containing lithium and the oxide is present in the state of being particles with a median diameter of greater than 2 μｍ and less than 7 μｍ. A battery 100 according to the present disclosure comprises a positive electrode 20, a negative electrode 30, and an electrolyte layer 40 that is disposed between the positive electrode 20 and the negative electrode 30, wherein the positive electrode 20 or negative electrode 30 includes the electrode 10 according to the present disclosure.

Description

Electrode, battery using same, and method of manufacturing electrode

[0001] The present disclosure relates to an electrode, a battery using the same, and a method for manufacturing the electrode.

[0002] Research and development of solid-state batteries as next-generation batteries is actively underway. One of the challenges of solid-state batteries is the high resistance of their electrodes, which makes it difficult to extract the full battery capacity. Therefore, there is a need to reduce the electrode resistance. To reduce the electrode resistance, it is important to form a good interface between the solid electrolyte and the electrode active material. For example, a sintered body of a solid electrolyte and an electrode active material is suitable for use as an electrode for a solid-state battery because it is easy to form a good interface between the solid electrolyte and the electrode active material.

[0003] Patent Document 1 discloses that an electrode sintered body containing a solid electrolyte material and an electrode active material at a high density can be obtained by setting the ratio of the average particle size of the electrode active material to the average particle size of the solid electrolyte material to 12 to 79 times.

[0004] JP 2013-218838 A

[0005] In the prior art, it is desirable to improve the sinterability of the electrode to reduce its resistance.

[0006] The present disclosure provides an electrode comprising: an electrode active material; and a solid electrolyte in contact with the electrode active material, wherein the electrode active material includes an oxide that contains titanium and does not contain lithium, and the oxide is present in the form of particles having a median diameter of more than 2 μm and less than 7 μm.

[0007] According to the present disclosure, the sinterability of the electrode can be improved to reduce its resistance.

[0008] FIG. 1 is a cross-sectional view showing a schematic configuration of an electrode in a first embodiment. FIG. 2 is a process diagram showing a method for manufacturing an electrode. FIG. 3 is a cross-sectional view showing a schematic configuration of a battery in a second embodiment. FIG. 4 is a process diagram showing a method for manufacturing a battery. FIG. 5 is a graph showing a charge / discharge curve for the first cycle of a half cell using the electrode of Example 1. FIG. 6 is a graph showing the particle size distribution of TiO2 particles. FIG. 7A is an SEM image (3000x) of a cross section of the electrode of Example 1. FIG. 7B is an SEM image (10000x) of a cross section of the electrode of Example 1. FIG. 8 is an SEM image (10000x) of a cross section of the electrode of Example 2. FIG. 9A is an SEM image (3000x) of a cross section of the electrode of Comparative Example 2. FIG. 9B is an SEM image (10000x) of a cross section of the electrode of Comparative Example 2. FIG. 10 is an SEM image (10000x) of a cross section of the electrode of Comparative Example 4. 11A and 11B are SEM images (3000x magnification) of a cross section of the electrode of Example 3. Fig. 11B is an SEM image (10000x magnification) of a cross section of the electrode of Example 3.

[0009] (Findings forming the basis of the present disclosure) The present inventors investigated the production of electrodes using titanium-containing oxides as electrode active materials. Titanium-containing oxides have advantages such as low cost mass production, excellent charge / discharge characteristics, and high safety, and are therefore considered promising as electrode active materials for solid-state batteries.

[0010] Titanium-containing oxides are known for use in pigments, cosmetics, catalysts, and other applications. Oxides used in these applications typically have nanoparticle shapes on the nanometer order. However, according to the inventors' research, titanium-containing oxide nanoparticles tend to exist in the gaps between solid electrolyte particles during the molding process of electrode materials. In this case, the total contact area between the oxide nanoparticles and the solid electrolyte particles increases. Therefore, the oxide nanoparticles inhibit the sintering between solid electrolyte particles, worsening the sintering of the electrode and ultimately the ionic conductivity within the electrode. In addition, oxide nanoparticles tend to exist in the gaps between conductive additive particles, inhibiting the electron path and thereby worsening the electrical conductivity within the electrode. In other words, oxide nanoparticles are not necessarily suitable for producing electrodes with practical electrical and ionic conductivities. Therefore, when using titanium-containing oxides as electrode active materials, a technology is needed to improve the sintering of electrodes while suppressing the inhibition of sintering between solid electrolyte particles and the inhibition of the formation of electron paths between conductive additive particles.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0012] First Embodiment Fig. 1 is a cross-sectional view showing a schematic configuration of an electrode 10 according to a first embodiment. The electrode 10 includes an electrode active material and a solid electrolyte. The electrode 10 is manufactured by firing a compact of a powder material including an electrode active material powder and a solid electrolyte powder. The electrode 10 is used, for example, as a positive electrode or a negative electrode of a solid-state battery.

[0013] In this specification, "sintering" refers to the phenomenon in which bonding occurs between particles when a compact of powder material is heated, causing the compact to become dense with volumetric shrinkage. "Firing" refers to the heat treatment for sintering.

[0014] The electrode active material is a material capable of absorbing and releasing metal ions, such as lithium ions. In this embodiment, the electrode active material includes an oxide that contains titanium but does not contain lithium. In the electrode 10, the oxide serving as the electrode active material exists in the form of particles having a median diameter of more than 2 μm and less than 7 μm. The oxide particles are connected to each other by the sintered phase of the solid electrolyte. The median diameter of the oxide particles may be more than 3 μm and less than 7 μm, or may be more than 3.4 μm and less than 6 μm.

[0015] The electrode 10 has oxide particles of micrometer order size as the electrode active material. Oxide particles of this size may be present between solid electrolyte particles during powder molding, but the total contact area between the oxide particles and the solid electrolyte particles can be reduced compared to when oxide particles of nanometer order size are used. Therefore, oxide particles of micrometer order size can reduce the influence of sintering inhibitors and improve the sinterability of the electrode 10. In other words, a good contact interface can be formed between the oxide and the solid electrolyte. This reduces the resistance of the electrode 10. The sinterability of the electrode 10 can be determined, for example, by the porosity of the electrode 10.

[0016] The median diameter of oxide particles serving as the electrode active material may be a value calculated from an electron microscope image of the cross section of the electrode 10. Specifically, the cross section of the electrode 10 is observed using a scanning electron microscope. The magnification is, for example, 3000x. Image analysis software is used to measure the Feret diameters of oxide particles present in two different observation fields. The "Feret diameter" is the length of the perpendicular line formed by sandwiching a particle between two parallel lines in a fixed direction. The number of particles to be measured is, for example, 185 or more. That is, the width of the observation field is adjusted so that 185 or more particles are included in the two different observation fields. Note that, if coarse particles generated by aggregation of secondary particles are present, it is difficult to say that such coarse particles accurately represent the structure of the electrode 10. Therefore, such coarse particles are excluded from the measurement target. Coarse particles are, for example, particles having a Feret diameter of 16.5 μm or more. Next, the volume of each particle is calculated assuming that it is a sphere having the measured Feret diameter. The particle size distribution is created by plotting particle size (= Feret diameter, in 0.1 μm increments) on the horizontal axis and the volume of particles with that particle size on the vertical axis. The particle size at which the cumulative volume in this particle size distribution is 50% is considered to be the median diameter of the oxide particles contained in electrode 10.

[0017] The median diameter may be the median diameter of secondary particles. Secondary particles may be produced by granulating primary particles of nanometer order size. Furthermore, primary particles of micrometer order size can be produced by hydrothermal synthesis.

[0018] Examples of oxides containing titanium include titanium(IV) oxide and composite oxides containing titanium and a transition metal other than titanium. These materials have the ability to absorb and release metal ions such as lithium ions, and are therefore suitable for the electrode 10 of this embodiment.

[0019] It is desirable that the oxide used as the electrode active material be capable of being co-sintered with the solid electrolyte. Specifically, it is desirable that the oxide is less likely to react with the solid electrolyte and maintain its crystalline structure even after sintering. For example, titanium (IV) oxide is suitable for the electrode 10 of this embodiment because it is less likely to react with a NASICON-type oxide solid electrolyte, which is a typical oxide solid electrolyte.

[0020] Examples of titanium(IV) oxide include anatase type (tetragonal crystal) titanium oxide, rutile type (tetragonal crystal) titanium oxide, and brookite type (rectangular crystal) titanium oxide.

[0021] The titanium oxide may contain anatase-type titanium oxide. The main component of the titanium oxide may be anatase-type titanium oxide. Anatase-type titanium oxide is suitable, for example, as an active material for lithium-ion secondary batteries. Furthermore, the use of anatase-type titanium oxide improves the sinterability of the electrode 10. "Main component" means the component that is contained in the largest amount by mass. 90% by mass or more of the titanium oxide may be anatase-type titanium oxide. The titanium oxide may substantially contain only anatase-type titanium oxide.

[0022] The structure of titanium oxide can be examined by X-ray diffraction measurement or Raman spectroscopy. The ratio of components contained in titanium oxide can be confirmed by analyzing the results of X-ray diffraction measurement by the Rietveld method.

[0023] Examples of composite oxides suitable for the electrode active material include composite oxides containing titanium and niobium. Composite oxides containing titanium and niobium also have the ability to absorb and release metal ions such as lithium ions, and are therefore suitable for the electrode 10 of this embodiment. The composite oxide containing titanium and niobium has a composition of, for example, TiNbO.

[0024] The oxide particles serving as the electrode active material may contain secondary particles. The secondary particles have multiple voids therein. When the oxide particles serving as the electrode active material occlude metal ions such as lithium ions, the voids absorb the volume change of the particles. As a result, good contact between the electrode active material and the solid electrolyte is maintained even when the battery is repeatedly charged and discharged. Furthermore, deterioration of sintered-type all-solid-state oxide batteries can be attributed to cracks occurring in the electrodes during charging and discharging, which deteriorates the contact between the active material and the solid electrolyte. Using secondary particles as the active material can reduce such deterioration.

[0025] The solid electrolyte may be an electrolyte suitable for forming the electrode 10. Examples of such electrolytes include oxide solid electrolytes. Examples of oxide solid electrolytes include solid electrolytes having a NASICON structure, solid electrolytes having a perovskite structure, solid electrolytes having a LISICON structure, and solid electrolytes having a garnet structure. Among these, a lithium-containing phosphate compound having a NASICON structure is suitable for the electrode 10.

[0026] NASICON-type solid electrolytes are materials that can be sintered at lower temperatures than other oxide solid electrolytes, such as solid electrolytes with a perovskite structure or a garnet structure. Being able to sinter at low temperatures means that it is advantageous for suppressing reactions between the electrode active material and the solid electrolyte. Furthermore, being able to sinter at low temperatures also makes it possible to avoid the transition from anatase-type titanium oxide to rutile-type titanium oxide.

[0027] The lithium-containing phosphate compound is Li 1+x Al x Ge 2-x The compound may have a composition of (PO4)3 (0≦x≦2). When a compound having such a composition is used for the solid electrolyte and an oxide containing titanium is used for the electrode active material, the effects of the configuration of this embodiment are more fully exhibited. In this specification, a compound having the above composition may be referred to as "LAGP."

[0028] Other examples of lithium-containing phosphate compounds include Li 1+x Al x Ti 2-x (PO4)3 (0≦x≦2). This compound may be referred to as "LATP" in this specification.

[0029] LAGP is more suitable for the electrode 10 of the present disclosure. Since LAGP does not contain Ti, it has a wider potential window on the negative side (negative side) than LATP. In this case, it is possible to select a negative electrode active material with a lower potential. This is advantageous for providing a high-voltage, high-capacity battery. One example that exhibits this effect is the combination of LAGP and titanium (IV) oxide. Furthermore, LAGP is an electrolyte that can be sintered at a lower temperature than LATP. Being able to sinter at a lower temperature means that it is advantageous for suppressing the reaction between the electrode active material and the solid electrolyte.

[0030] In the electrode 10, the solid electrolyte forms a mesh-like sintered phase. For example, in the cross section of the electrode 10, the length of the interface where the particles of the electrode active material and the sintered phase of the solid electrolyte are in contact with each other without any gaps is on the order of micrometers, and the sintered phase of the solid electrolyte forms a good interface with the particles of the electrode active material. The presence of such a contact interface contributes to reducing the resistance of the electrode 10.

[0031] The sintered phase of the solid electrolyte may be a phase in which particles of the solid electrolyte are bonded together and grain boundaries are lost. The sintered phase without grain boundaries exhibits excellent ionic conductivity and can form a good contact interface with particles of the electrode active material. Such a structure can be formed by using an amorphous solid electrolyte as the raw material for the electrode 10. For example, the structure of the sintered phase can be confirmed by observing the cross section of the electrode 10 at 10,000x magnification using a scanning electron microscope.

[0032] In the electrode 10, the sintered phase of the solid electrolyte includes a crystalline phase and an amorphous phase. It is desirable for the sintered phase of the solid electrolyte to include a crystalline phase, since the electrode 10 exhibits higher ionic conductivity. As described below, the crystalline phase can be formed by appropriately adjusting the firing temperature. For example, firing at a temperature equal to or higher than the crystallization temperature of the solid electrolyte results in an electrode 10 containing a crystalline solid electrolyte. However, the solid electrolyte may also contain an amorphous phase. When an amorphous phase is included, the flexibility of the solid electrolyte increases, making it easier for the solid electrolyte to absorb volume changes due to expansion and contraction of the electrode active material.

[0033] The crystallinity of the solid electrolyte can be examined by X-ray diffraction measurement or a differential scanning calorimeter (DSC). When X-ray diffraction measurement is used, if only a halo pattern is observed in the X-ray diffraction pattern of the solid electrolyte, the solid electrolyte can be determined to be amorphous.

[0034] The electrode 10 may further contain a conductive additive. Examples of the conductive additive include carbon materials such as graphite, carbon black, carbon fiber, and carbon nanotubes. The graphite may be natural graphite or artificial graphite. Examples of carbon black include acetylene black and ketjen black. The carbon material may be crystalline or amorphous. The conductive additive typically has a particle shape on the order of nanometers or micrometers. Examples of the particle shape include spherical, oval, scaly, and fibrous.

[0035] The porosity of the electrode 10 is, for example, 30% or less. The lower limit of the porosity is not particularly limited and is, for example, 5%. The porosity can be calculated from the true density of each material contained in the electrode 10, the content of each material, the mass of the electrode 10, and the dimensions of the electrode 10.

[0036] The electrode 10 has an electrode active material content of, for example, 15% by mass or more and 60% by mass or less. The electrode 10 has a solid electrolyte content of, for example, 30% by mass or more and 80% by mass or less. The electrode 10 has a conductive additive content of, for example, 0.1% by mass or more and 10% by mass or less.

[0037] Next, a method for manufacturing the electrode 10 will be described. Fig. 2 is a process diagram showing the method for manufacturing the electrode 10. In this embodiment, the electrode 10 is manufactured by firing a compact of a mixture of an electrode active material and a solid electrolyte.

[0038] In step S1, raw materials are mixed to prepare a slurry. The raw materials for the slurry are, for example, an electrode active material, a solid electrolyte, a conductive additive, a binder, and a solvent. The binder and the solvent may be mixed in advance to prepare a binder solution, and the electrode active material, the solid electrolyte, and the conductive additive may be mixed into the binder solution to prepare the slurry.

[0039] The oxide particles serving as the electrode active material have a median diameter of more than 3 μm and less than 10 μm, as measured by, for example, a laser diffraction particle size analyzer. This configuration can improve the sinterability of the electrode 10. The median diameter measured by the laser diffraction particle size analyzer is usually larger than the median diameter determined from a cross-sectional SEM image.

[0040] The electrode active material, solid electrolyte, and conductive additive may each be a powder material. The median particle size of the solid electrolyte is preferably smaller than the median particle size of the electrode active material. When the electrode active material and the solid electrolyte satisfy this relationship, the sinterability of the electrode 10 can be improved. As a result, the resistance of the electrode 10 can be reduced.

[0041] The ratio of the median diameter of the particles of the electrode active material to the median diameter of the particles of the solid electrolyte is, for example, 2 or more and 30 or less. When the electrode active material and the solid electrolyte satisfy this relationship, the sinterability of the electrode 10 can be improved. As a result, the resistance of the electrode 10 can be reduced. The ratio of the median diameter of the particles of the electrode active material to the median diameter of the particles of the solid electrolyte may be 4 or more and 30 or less, or 4 or more and 20 or less.

[0042] The oxide particles serving as the electrode active material may have a particle diameter (D90) in the range of more than 6 μm and less than 15 μm. The use of such oxide particles can improve the sinterability of the electrode 10. As a result, the resistance of the electrode 10 can be reduced. D90 is the particle diameter at which the cumulative volume is 90% in a volume-based particle size distribution, and can be measured using a laser diffraction particle size distribution analyzer.

[0043] The BET specific surface area of ​​the oxide particles used as the electrode active material is 1 m 2 / g or more 7m 2 / g or less. When the BET specific surface area of ​​the oxide particles is appropriately adjusted, side reactions between the oxide particles and the solid electrolyte particles during firing are suppressed. As a result, the electrode 10 can have high ionic conductivity. Since side reactions between the oxide particles and the solid electrolyte particles result in the formation of an interfacial resistance layer, such side reactions should be suppressed.

[0044] The oxide particles serving as the electrode active material may include primary particles and secondary particles. The ratio (Dp / D50) of the average particle size (Dp) of the primary particles to the median size (D50) of the electrode active material particles is, for example, 0.6 or less. The ratio (Dp / D50) is preferably 0.16 or less. By using such oxide particles, the sinterability of the electrode 10 can be improved. As a result, the resistance of the electrode 10 can be reduced. The lower limit of the ratio (Dp / D50) is not particularly limited and is, for example, 0.05.

[0045] The average particle size (Dp) of primary particles of an oxide can be determined by the following method. Oxide particles are observed under a scanning electron microscope (magnification 30,000 times). 50 primary particles whose outlines can be confirmed in the obtained image are selected. The particle diameter of the major axis of the selected primary particles is measured. The average particle diameter of the 50 primary particles is calculated. The calculated value is regarded as the average particle size (Dp) of the primary particles.

[0046] As will be described later with reference to Fig. 6, the oxide particles serving as the electrode active material may have a bimodal particle size distribution. By using such oxide particles, the sinterability of the electrode 10 can be improved. As a result, the resistance of the electrode 10 can be reduced.

[0047] For example, in the volume-based particle size distribution of oxide particles as the electrode active material, a first peak may exist in the range of 0.5 μm to 2.5 μm, and a second peak may exist in the range of 3 μm to 9 μm. The second peak is larger than the first peak. By using such oxide particles, the sinterability of the electrode 10 can be improved. As a result, the resistance of the electrode 10 can be reduced.

[0048] The volume-based particle size distribution of the solid electrolyte particles may have a peak in the range of 0.2 μm to 2 μm. By using such a solid electrolyte, the sinterability of electrode 10 can be improved, and as a result, the resistance of electrode 10 can be reduced.

[0049] The particles of the solid electrolyte have a median diameter of, for example, 100 nm or more and 2000 nm or less.

[0050] The solid electrolyte particles used as raw materials may be amorphous. By pre-firing the amorphous solid electrolyte in a temperature range above the glass transition temperature and below the crystallization temperature, a good interface can be formed with the electrode active material particles at low temperatures. This is because the solid electrolyte has good flexibility in a temperature range above the glass transition temperature and below the crystallization temperature. The ionic conductivity of the electrode 10 is improved by subsequently firing the solid electrolyte in an appropriate temperature range above the crystallization temperature and below the melting point to increase the crystallinity of the solid electrolyte. Furthermore, amorphous solid electrolytes can be sintered at lower temperatures than crystalline solid electrolytes. Being able to sinter at low temperatures is advantageous in terms of suppressing the reaction between the electrode active material and the solid electrolyte.

[0051] The amorphous nature of a solid electrolyte can be confirmed by a differential scanning calorimetry (DSC). For example, if the crystallinity determined by DSC is 30% or less, the solid electrolyte can be said to be amorphous. The crystallinity can be calculated by the following formula. The measured heat of crystallization means the amount of heat generated by crystallization of the solid electrolyte sample being measured. The heat of crystallization of a completely amorphous solid electrolyte means the amount of heat generated by crystallization in an amorphous solid electrolyte in which only a halo pattern is observed in the X-ray diffraction pattern.

[0052] Crystallinity (%) = 100 x (Qa-Qs) / Qa Qs: Measured heat of crystallization (J / g) Qa: Completely amorphous crystallization heat (J / g)

[0053] In this specification, the term "median diameter" refers to the particle diameter when the cumulative volume in the volume-based particle size distribution is 50%. The volume-based particle size distribution is measured using a laser diffraction particle size distribution analyzer at the raw material stage. At the electrode 10 stage, it is measured by image analysis of the cross section.

[0054] The binder is decomposed and removed by firing. Thermoplastic resins such as polyvinyl butyral, polyvinylidene fluoride, cellulose, acrylic, urethane, and polyvinyl alcohol can be used as the binder. The solvent is typically an organic solvent such as absolute alcohol (e.g., absolute ethanol), toluene, butyl acetate, or NMP. The slurry may also contain a plasticizer. The type of plasticizer is not particularly limited, and phthalate esters such as dioctyl phthalate and diisononyl phthalate can be used.

[0055] The conductive additive may be a carbon material. The carbon material may contain amorphous carbon. The particles of the carbon material have a median diameter of 70 nm or less and a particle size of 60 nm or less. 2 The carbon material may have a BET specific surface area of ​​100 / g or less. By using such a carbon material, the sinterability of the electrode 10 can be improved. The lower limit of the median diameter of the carbon material particles is not particularly limited, and is, for example, 10 nm. The lower limit of the BET specific surface area of ​​the carbon material particles is not particularly limited, and is, for example, 10 m 2 / g.

[0056] In step S2, the slurry is applied to a substrate to form a coating film. The substrate may be a resin substrate, a glass substrate, a ceramic substrate, or a metal substrate. After the coating film is formed, the solvent is removed from the coating film. This results in a molded body for an electrode. To remove the solvent from the coating film, the coating film may be heated or air-dried. If necessary, the coating film may be pressed or hot-pressed. The slurry may be molded and dried without using a substrate.

[0057] The slurry may be applied to a substrate to form a coating film, and then the coating film may be pulverized, and the raw material powder obtained by pulverization may be pressed or hot-pressed to produce a green body for an electrode.

[0058] In step S3, the electrode compact is pre-fired. The pre-fired is carried out, for example, in air or in an inert atmosphere. The inert atmosphere is, for example, a nitrogen gas atmosphere or a rare gas atmosphere. A small amount of oxygen may be mixed into the inert atmosphere. The pre-fired temperature (ambient temperature) is, for example, 250°C to 600°C. The pre-fired firing time is, for example, 1 hour to 60 hours.

[0059] The pre-baking is preferably carried out in a temperature range where the binder is sufficiently removed, the solid electrolyte is softened above its glass transition temperature, and crystallization of the solid electrolyte does not proceed, thereby forming a good interface between the electrode active material and the solid electrolyte as the binder is removed.

[0060] In step S4, the electrode compact is sintered. The sintering is carried out, for example, in air or in an inert atmosphere. The inert atmosphere is, for example, a nitrogen gas atmosphere or a rare gas atmosphere. A small amount of oxygen may be mixed into the inert atmosphere. The sintering temperature (ambient temperature) is, for example, 550°C to 900°C. The sintering time is, for example, 1 hour to 15 hours.

[0061] During the sintering process, the particles of the solid electrolyte bond together to form a sintered phase without grain boundaries. The sintering process is preferably performed in a temperature range where the crystallization of the solid electrolyte proceeds appropriately. The improved crystallinity of the solid electrolyte leads to improved ionic conductivity of the electrode 10.

[0062] The electrode 10 can be manufactured through the above steps.

[0063] Second Embodiment FIG. 3 is a cross-sectional view showing a schematic configuration of a battery 100 according to a second embodiment.

[0064] The battery 100 includes a positive electrode 20, a negative electrode 30, and an electrolyte layer 40. The electrolyte layer 40 is disposed between the positive electrode 20 and the negative electrode 30. The electrode 10 described in the first embodiment is used for the positive electrode 20 or the negative electrode 30. By using the electrode 10 for the positive electrode 20 or the negative electrode 30, the effect of reducing resistance can be obtained in the positive electrode 20 or the negative electrode 30.

[0065] The electrode 10 described in the first embodiment is preferably used as the negative electrode 30. In this case, the oxide containing titanium acts as the negative electrode active material. Since the oxide containing titanium is suitable for the negative electrode active material, the electrode 10 is suitable for the negative electrode 30.

[0066] When the electrode 10 is used as the negative electrode 30, the titanium-containing oxide does not contain lithium when the battery 100 is in a state where no charge or discharge has been performed after assembly. In other words, the battery 100 is in a fully discharged state.

[0067] However, the electrode 10 can also be used as a positive electrode, in which case a material less noble than the oxide containing titanium, such as lithium metal, is used as the negative electrode active material.

[0068] The positive electrode 20 includes a positive electrode active material. The positive electrode active material is a material capable of absorbing and releasing metal ions such as lithium ions. Examples of the positive electrode active material include lithium-containing transition metal oxides and lithium-containing transition metal phosphates. Of these, lithium-containing transition metal phosphates are suitable for the electrode 10. Examples of lithium-containing transition metal phosphates include lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate. In addition to the positive electrode active material, the positive electrode 20 may also include a solid electrolyte, a conductive additive, and the like.

[0069] The electrolyte layer 40 includes a solid electrolyte. Examples of the solid electrolyte include a sulfide solid electrolyte, a halide solid electrolyte, a complex hydride solid electrolyte, a porous oxide solid electrolyte impregnated with an electrolytic solution, and an oxide solid electrolyte. The composition of the solid electrolyte included in the electrolyte layer 40 may be the same as or different from the composition of the solid electrolyte included in the positive electrode 20. The composition of the solid electrolyte included in the electrolyte layer 40 may be the same as or different from the composition of the solid electrolyte included in the negative electrode 30. The positive electrode 20, the electrolyte layer 40, and the negative electrode 30 may include solid electrolytes with the same composition.

[0070] In the battery 100, the positive electrode 20, the negative electrode 30, and the electrolyte layer 40 may be composed of a sintered body. In this case, the positive electrode 20, the negative electrode 30, and the electrolyte layer 40 can be integrally formed by co-firing. By integrating the positive electrode 20, the negative electrode 30, and the electrolyte layer 40 by co-firing, the positive electrode 20, the negative electrode 30, and the electrolyte layer 40 can be reliably in contact with each other, thereby improving the conductivity of metal ions such as lithium ions.

[0071] FIG. 4 is a process diagram showing a method for manufacturing the battery 100. First, in step ST1, slurries are prepared. Specifically, a positive electrode slurry, an electrolyte layer slurry, and an anode slurry are prepared. These slurries can be prepared in accordance with the method described in step S1 of FIG. 2. Note that the electrolyte slurry does not contain an electrode active material or a conductive additive.

[0072] In step ST2, green sheets are prepared. Specifically, a positive electrode green sheet, an electrolyte layer green sheet, and a negative electrode green sheet are prepared using a positive electrode slurry, an electrolyte layer slurry, and a negative electrode slurry. The green sheets can be prepared by applying the slurry to a substrate to form a coating film, and then drying the coating film. The green sheets are peeled off from the substrate at an appropriate time.

[0073] In step ST3, the green sheets are stacked. Specifically, the positive electrode green sheet, the electrolyte layer green sheet, and the negative electrode green sheet are stacked in this order and pressed together to obtain a laminate including the positive electrode green sheet, the electrolyte layer green sheet, and the negative electrode green sheet.

[0074] In steps ST4 and ST5, the pre-firing and main firing processes are performed. The pre-firing and main firing processes are as described in steps S3 and S4 of Fig. 2. Through the above processes, the sintered battery 100 is obtained.

[0075] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0076] (Technology 1) An electrode comprising: an electrode active material; and a solid electrolyte in contact with the electrode active material, wherein the electrode active material includes an oxide that contains titanium and does not contain lithium, and the oxide exists in the state of particles having a median diameter of more than 2 μm and less than 7 μm.

[0077] This configuration allows a good contact interface to be formed between the electrode active material and the solid electrolyte, thereby improving the sinterability of the electrode.

[0078] (Technology 2) The electrode according to Technology 1, wherein the oxide comprises at least one selected from the group consisting of titanium oxide and a composite oxide containing titanium and niobium. Titanium oxide has the ability to absorb and release metal ions such as lithium ions, and is therefore suitable for the electrode of the present disclosure. A composite oxide containing titanium and niobium also has the same ability, and is therefore suitable for the electrode of the present disclosure.

[0079] (Technology 3) The solid electrolyte is Li 1+x Al x Ge 2-x The electrode according to Technology 1 or Technology 2, having a composition of (PO4)3 (0≦x≦2). When a compound having such a composition is used for the solid electrolyte and an oxide containing titanium is used for the electrode active material, the effects of the configuration of the present disclosure are more fully exhibited.

[0080] (Technology 4) The electrode according to any one of Technologies 1 to 3, wherein particles of the oxide are bonded to each other by a sintered phase of the solid electrolyte, and the sintered phase includes an amorphous phase. This configuration imparts excellent ionic conductivity to the electrode.

[0081] (Technology 5) A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode or the negative electrode includes the electrode according to any one of technologies 1 to 4.

[0082] By using the electrode of the present disclosure as a positive electrode or a negative electrode, the resistance of the battery can be reduced.

[0083] (Technology 6) The battery according to Technology 5, wherein the negative electrode comprises the electrode. Since oxides containing titanium are suitable for negative electrode active materials, the electrode of the present disclosure is suitable for negative electrodes.

[0084] (Technology 7) A method for producing an electrode, comprising firing a compact of a mixture of an electrode active material and a solid electrolyte, wherein the electrode active material comprises oxide particles containing titanium and not containing lithium, and the oxide particles have a median diameter of more than 3 μm and less than 10 μm.

[0085] This configuration can improve the sinterability of the electrode.

[0086] (Technology 8) The method for producing an electrode according to Technology 7, wherein the median diameter of the particles of the solid electrolyte is smaller than the median diameter of the particles of the oxide. When the electrode active material and the solid electrolyte satisfy this relationship, the sinterability of the electrode can be improved.

[0087] (Technology 9) The BET specific surface area of ​​the particles of the oxide is 1 m 2 / g or more 7m 2 / g or less. When the BET specific surface area of ​​the oxide particles is appropriately adjusted, side reactions between the oxide particles and the solid electrolyte particles during firing are suppressed, and as a result, the electrode can have high ionic conductivity.

[0088] (Technology 10) The method for manufacturing an electrode according to any one of Technologies 7 to 9, wherein the particles of the oxide include primary particles and secondary particles, and the ratio of the average particle size of the primary particles to the median size of the particles of the oxide is 0.6 or less. By using such oxide particles, the sinterability of the electrode can be improved.

[0089] (Technology 11) A method for manufacturing a battery, comprising firing a laminate including a positive electrode green sheet, an electrolyte layer green sheet, and a negative electrode green sheet, wherein the positive electrode green sheet or the negative electrode green sheet is a molded body of a mixture including an electrode active material and a solid electrolyte, the electrode active material includes particles of an oxide that contains titanium and does not contain lithium, and the oxide particles have a median diameter of more than 3 μm and less than 10 μm.

[0090] This configuration allows for a good contact interface to be formed between the electrode active material and the solid electrolyte, improving the sinterability of the positive electrode or negative electrode and reducing the resistance of the sintered battery.

[0091] Example 1 A slurry was prepared by mixing 20 parts by mass of TiO2 (anatase type), 75 parts by mass of LAGP (amorphous), 5 parts by mass of acetylene black (Li-400, manufactured by Denka Co., Ltd.), 38.75 parts by mass of binder solution, and 116.25 parts by mass of super-dehydrated ethanol. These raw materials were mixed using a planetary centrifugal mixer (Mixer, manufactured by Thinky Corporation) at 2000 rpm for 30 minutes. The binder solution was prepared by mixing 15 parts by mass of polyvinyl butyral (BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 140 parts by mass of super-dehydrated ethanol. The TiO2 particles used were secondary particles.

[0092] Before preparing the slurry, the particle size distribution of TiO2, the BET specific surface area of ​​TiO2, and the particle size distribution of LAGP were measured in advance. The particle size distribution of TiO2 and the particle size distribution of LAGP were measured using a laser diffraction particle size analyzer (Malvern Panalytical, Mastersizer 3000). D10, D50, and D90 were calculated from the particle size distribution. The results are shown in Table 1. The median diameter of TiO2 was 4.180 μm. The median diameter of LAGP was 0.888 μm. D10 is the particle diameter at which the cumulative volume is 10% in the volume-based particle size distribution. "Mastersizer" is a registered trademark of Malvern Panalytical.

[0093] The average particle size (Dp) of the primary particles of TiO2 was calculated using a scanning electron microscope by the method described above.

[0094] The BET specific surface area of ​​TiO2 was measured using the following method. A predetermined amount of TiO2 was placed in a measurement test tube, which was then connected to a specific surface area / pore distribution analyzer (Quantachrome, Autosorb iQ-MP). A nitrogen gas adsorption test was then conducted at an adsorption temperature of 77 K and an upper limit of the adsorption relative pressure of 0.99 (P / P0). Using the analytical software ASiQWin, analysis was performed using the BET method in the linear region of the adsorption isotherm, and the BET specific surface area was calculated. "Autosorb" is a registered trademark of Sysmex Corporation.

[0095] Next, the slurry was dried on a hot plate set at 80° C. After confirming that the ethanol had been sufficiently removed from the slurry, the dried film was coarsely pulverized and subjected to a vacuum drying treatment (80° C., 2 hours). The coarsely pulverized product after vacuum drying was placed in a mortar and manually pulverized for 15 minutes to obtain a raw material powder.

[0096] Next, 122 mg of the raw material powder was molded by uniaxial pressing using a Φ10.5 mm tablet press to obtain an electrode compact. The pressing conditions were 276 MPa and 1 minute. Next, the electrode compact was pre-fired to remove the binder. The pre-fired conditions were air, 530 ° C (ambient temperature), and 2 hours. Finally, the electrode compact was fired to obtain the electrode of Example 1. The firing conditions were nitrogen atmosphere, 700 ° C (ambient temperature), and 2 hours. The dimensions of the electrode of Example 1 were a diameter of 9.53 mm and a thickness of 0.6471 mm. The mass was 115.0 mg.

[0097] Example 2 An electrode of Example 2 was fabricated in the same manner as Example 1, except that LAGP (amorphous) with a median diameter of 0.300 μm was used, as shown in Table 1. The electrode of Example 2 had a diameter of 9.26 mm and a thickness of 0.6363 mm. The mass was 111.5 mg.

[0098] Comparative Example 1 An electrode of Comparative Example 1 was produced in the same manner as in Example 1, except that titanium oxide (anatase type) with a median diameter of 0.491 μm was used, as shown in Table 1. The dimensions of the electrode of Comparative Example 1 were a diameter of 9.96 mm and a thickness of 0.6528 mm. The mass was 114.9 mg. The titanium oxide particles used were secondary particles.

[0099] Comparative Example 2 An electrode of Comparative Example 2 was produced in the same manner as in Example 1, except that titanium oxide (anatase type) with a median diameter of 1.540 μm was used, as shown in Table 1. The dimensions of the electrode of Comparative Example 2 were a diameter of 9.96 mm and a thickness of 0.6380 mm. The mass was 114.4 mg. The titanium oxide particles used were secondary particles.

[0100] Comparative Example 3 An electrode of Comparative Example 3 was produced in the same manner as in Example 1, except that titanium oxide (anatase type) with a median diameter of 1.540 μm and LAGP (amorphous) with a median diameter of 0.300 μm were used, as shown in Table 1. The dimensions of the electrode of Comparative Example 3 were a diameter of 9.80 mm and a thickness of 0.6457 mm. The mass was 112.6 mg. The titanium oxide particles used were secondary particles.

[0101] Comparative Example 4 An electrode of Comparative Example 4 was produced in the same manner as in Example 1, except that titanium oxide (anatase type) with a median diameter of 0.675 μm was used, as shown in Table 1. The dimensions of the electrode of Comparative Example 4 were a diameter of 9.91 mm and a thickness of 0.6410 μm. The mass was 114.6 mg. The titanium oxide particles used were secondary particles.

[0102]

[0103] [Measurement of Density] The density of the electrode was calculated from the dimensions and mass of the electrode. The results are shown in Table 2.

[0104] [Porosity Measurement] The true density of each material used in the electrode fabrication was measured in advance. The electrode porosity was calculated using the electrode dimensions, the measured true density, and the content of each material. The electrode was considered to contain only TiO2, LAGP, and the conductive additive. The true density was measured by the He substitution method using a pycnometer (Ultrapyc 5000, manufactured by Anton Paar). With LAGP, an amorphous material is used as the starting material, but it is difficult to evaluate the density after sintering. Therefore, the theoretical density was used as the true density of LAGP. The results are shown in Table 2.

[0105] [Measurement of Ionic Conductivity] The electrical conductivity of the electrode was measured using the following method. First, the electrode was placed in a vacuum dryer and dried at 80°C for 1 hour. Next, a Li metal foil, a solid polymer electrolyte membrane, an electrode, a solid polymer electrolyte membrane, and a Li metal foil were stacked in this order and placed in a sealed two-electrode cell (manufactured by Hosen Co., Ltd.). A LiTFSI-PEO membrane was used as the solid polymer electrolyte membrane. The weight-average molecular weight Mw of the PEO contained in the LiTFSI-PEO membrane was 600,000. In the LiTFSI-PEO membrane, the molar ratio of PEO to LiTFSI was PEO:LiTFSI = 18:1. Then, chronoamperometry measurements were performed at measurement voltages of 0.1 V, 0.25 V, 0.5 V, and 0.75 V. The current value 70 seconds after the voltage application was used. The ambient temperature during the measurements was 60°C. The resistance was calculated from the relationship between voltage and current. The ionic conductivity was calculated using the electrode dimensions. The results are shown in Table 2.

[0106] [Measurement of Electrical Conductivity] The electrical conductivity of the electrode was measured using the following method. First, the electrode was placed in a vacuum dryer and dried at 80°C for 1 hour. Next, a 290 nm thick Au thin film was formed on both sides of the electrode by sputtering. The electrode was placed in a sealed two-electrode cell (manufactured by Hosen Co., Ltd.). Chronoamperometry measurements were then performed at measurement voltages of 0.1 V, 0.25 V, 0.5 V, and 0.75 V. The current value was measured 70 seconds after the voltage was applied. The ambient temperature during measurement was 25°C. The resistance value was calculated from the relationship between voltage and current. The electrical conductivity was calculated using the electrode dimensions. The results are shown in Table 2.

[0107] [Measurement of the Amount of Interfacial Side Reaction] The amount of interfacial side reaction of the electrode was measured by the following method. First, the electrode was placed in a vacuum dryer and dried at 80°C for 1 hour. Next, a 290 nm thick Au thin film was formed on one side of the electrode by sputtering. Next, the Au thin film, electrode, solid polymer electrolyte membrane, and Li metal foil were laminated in this order, and these were placed in a sealed two-electrode cell (manufactured by Hosen Co., Ltd.) to obtain a half cell. A LiTFSI-PEO film was used as the solid polymer electrolyte membrane. Next, a charge-discharge test of the half cell was performed in constant current constant voltage (CCCV) mode at 60°C, and the charge-discharge curve for the first cycle was obtained. The half cell was discharged at a constant current of 0.01 C until the voltage reached 1.5 V, and then discharged at a constant voltage of 1.5 V for 5 hours. The half cell was charged at a constant current of 0.01 C until the voltage reached 3 V, and then charged at a constant voltage of 3 V for 5 hours.

[0108] FIG. 5 is a graph showing the charge-discharge curves of a half cell using the electrode of Example 1. The vertical axis represents the potential (unit: V) relative to the dissolution and deposition potential of lithium metal. The horizontal axis represents the capacity ratio (%) of each point on the graph, assuming the discharge capacity at the first cycle to be 100. As shown in FIG. 5, TiO2 has a plateau region at a potential lower than 2 V. Therefore, the driving potential region of TiO2 is less than 2 V. Furthermore, at 2 V (vs. Li / Li + Of the redox capacities observed in the potential region above 1000 kJ / s, the capacity value during discharge is defined as the "amount of interfacial side reaction Ci."

[0109] The redox capacity observed outside the TiO2 operating potential range captures the charge / discharge resulting from the diffusion layer (reaction layer) formed when Ti contained in TiO2 diffuses into LAGP during sintering. A small amount of interfacial side reaction means that the side reaction between LAGP and TiO2 during sintering is suppressed, and also means that the formation of a reaction layer associated with the side reaction is suppressed. Suppressing the formation of a reaction layer associated with the side reaction is desirable because it reduces the resistance of the electrode.

[0110] [Calculation of the Amount of Interfacial Side Reaction] The amount of interfacial side reaction Ci in the charge / discharge curves of the half cells using each electrode of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 was examined. The ratio of the amount of interfacial side reaction between LAGP and TiO2 due to sintering was calculated using the following formula. In other words, the "ratio of the amount of interfacial side reaction" listed in Table 1 is a relative value to the value of Comparative Example 4. (Ratio of the amount of interfacial side reaction) = 100 x A / B (%) A: Amount of interfacial side reaction Ci (mAh) of the half cell using each electrode B: Amount of interfacial side reaction Ci (mAh) of the half cell using the electrode of Comparative Example 4

[0111]

[0112] As shown in Table 2, the porosities of the electrodes of Examples 1 and 2 were 26.86% and 24.82%, respectively, which were significantly lower than the porosities of the electrodes of Comparative Examples 1 to 4.

[0113] As shown in Table 2, the electrodes of Examples 1 and 2 exhibited high electrical conductivity that was significantly higher than that of the electrodes of Comparative Examples 1 to 4. At the same time, the ionic conductivity of the electrodes of Examples 1 and 2 was higher than that of the electrodes of Comparative Examples 1 to 4. This result is presumably due to the low porosity of the electrodes of the Examples and the characteristic structure of the electrodes of the Examples.

[0114] The effect of the characteristic structure of the electrode of the example was also evident in the amount of interfacial side reaction. That is, the amount of interfacial side reaction in Example 1 was about 50% of the amount of interfacial side reaction in Comparative Example 4.

[0115] In this way, by appropriately adjusting the particle size of the titanium-containing oxide, the particle size of the solid electrolyte, and the relationship between them, the electrical properties of the electrode could be significantly improved.

[0116] FIG. 6 is a graph showing the particle size distribution of the TiO2 particles used in the examples and comparative examples. The horizontal axis shows particle diameter on a logarithmic scale. The vertical axis shows the ratio of the total volume of particles with the particle diameter shown on the horizontal axis to the total volume of the particles. As shown in FIG. 6, the TiO2 particles used in Examples 1 and 2 had a bimodal particle size distribution, i.e., two peaks. The first peak was in the range of 0.5 μm to 2.5 μm, and the second peak was in the range of 3 μm to 9 μm. The second peak was larger than the first peak.

[0117] The TiO particles used in the comparative example also exhibited a bimodal particle size distribution and contained relatively large particles. However, the porosity of the comparative electrode was low. It is presumed that the large particles contained in the TiO particles in the comparative example were merely weakly aggregated primary particles that were broken down into nano-order primary particles during processes such as slurry preparation and milling of the coated film. This is supported by the absence of large TiO particles in the SEM images of Figures 9A, 9B, and 10.

[0118] [Cross-section observation] Cross sections of the electrodes of the examples and comparative examples were formed by broad ion beam processing in an environment not exposed to the atmosphere. The cross sections were parallel to the thickness direction of the electrode. Next, the cross sections of the electrodes of the examples and comparative examples were observed with a scanning electron microscope (JEOL Ltd., JSM-7900F). The acceleration voltage was 3 kV, and the observation magnification was 3,000x or 10,000x.

[0119] 7A and 7B are SEM images (3000x or 10000x) of a cross section of the electrode of Example 1. FIG. 8 is an SEM image (10000x) of a cross section of the electrode of Example 2. FIGS. 9A and 9B are SEM images (3000x or 10000x) of a cross section of the electrode of Comparative Example 2. FIG. 10 is an SEM image (10000x) of a cross section of the electrode of Comparative Example 4.

[0120] As shown in Figures 7A and 7B, in the electrode of Example 1, the electrode active material 12 (TiO2) maintained the state of large-diameter particles. The large-diameter particles of the electrode active material 12 were secondary particles with multiple voids inside. Grain boundaries of micrometer length were formed along the outer edges of the sintered phase of the solid electrolyte 14 (LAGP) and the particles of the electrode active material 12. As sintering progressed, grain boundaries between particles of the solid electrolyte 14 were no longer observed. The conductive additive 16 was uniformly dispersed throughout the electrode.

[0121] The median diameter (D50) of the electrode active material 12 was calculated by the method described above using an SEM image (magnification 3000x) of the cross section of the electrode of Example 1. As a result, the median diameter of the electrode active material 12 in the electrode of Example 1 was 3.5 μm. Secondary particles having a plurality of voids were considered to be the electrode active material 12.

[0122] As shown in FIG. 8, the electrode of Example 2 using a solid electrolyte with a median diameter of 0.300 μm also had the same structure as the electrode of Example 1 shown in FIGS. 7A and 7B.

[0123] The median diameter of the electrode active material 12 was calculated using an SEM image (magnification: 3000 times) of the cross section of the electrode of Example 2. As a result, the median diameter of the electrode active material 12 in the electrode of Example 2 was 3.6 μm.

[0124] 9A, 9B, and 10, in the electrodes of Comparative Examples 2 and 4, the particles of the electrode active material 12a were dispersed at nanometer-order sizes. Some of the particles of the electrode active material 12a were completely surrounded by the sintered phase of the solid electrolyte 14a, while many particles faced the voids in the electrode and were not in sufficient contact with the solid electrolyte 14a. The conductive additive 16a was uniformly dispersed throughout the electrode.

[0125] In the electrodes of Comparative Examples 2 and 4, the median diameter of the electrode active material 12a was clearly on the order of nanometers, and therefore measurement of the median diameter was omitted.

[0126] As shown in Figures 7A, 7B, and 8, in the electrodes of Examples 1 and 2, oxide (TiO2) particles having a maximum Feret diameter of more than 5 μm appeared in the cross-sectional SEM images. Specifically, oxide (TiO2) particles having a maximum Feret diameter of approximately 7 μm appeared in the cross-sectional SEM images. This also applies to Example 3 described below. As shown in Figures 9A, 9B, and 10, no oxides with such large particle sizes were observed in the cross-section of the electrode of the comparative example. The "maximum Feret diameter" is the maximum length of the perpendicular line formed by sandwiching a particle between two parallel lines.

[0127] (Example 3) An electrode of Example 3 was produced in the same manner as in Example 1, except that TiNbO (D50≦5 μm) was used instead of titanium oxide. The electrode of Example 3 had a diameter of 9.44 mm, a thickness of 0.6497 mm, and a mass of 115.1 mg.

[0128] The density, porosity, electrical conductivity, and ionic conductivity of the electrode of Example 3 were measured by the methods described above. The results are shown in Table 3.

[0129]

[0130] As shown in Table 3, the porosity of the electrode of Example 3 was 26.7%. Similar to the electrodes of Examples 1 and 2, the porosity of the electrode of Example 3 was also sufficiently low.

[0131] Like the electrodes of Examples 1 and 2, the electrode of Example 3 also exhibited good electrical and ionic conductivity.

[0132] The cross section of the electrode of Example 3 was observed with a scanning electron microscope using the method described above. Figures 11A and 11B are SEM images (3000x and 10000x magnification) of the cross section of the electrode of Example 3. The electrode of Example 3 also had the same structure as the electrodes of Examples 1 and 2 (Figures 7A, 7B, and 8).

[0133] The median diameter of the electrode active material 12 was calculated using SEM images of a plurality of observation fields of the electrode of Example 3. As a result, the median diameter of the electrode active material 12 in the electrode of Example 3 was 2.5 μm.

[0134] The electrodes of the present disclosure are suitable as electrodes for solid-state batteries.

Claims

1. An electrode active material; A solid electrolyte in contact with the electrode active material; Equipped with The electrode active material includes an oxide that contains titanium and does not contain lithium, The oxide is present in the form of particles having a median diameter of more than 2 μm and less than 7 μm; the oxide particles are bound to each other by a sintered phase of the solid electrolyte; The sintered phase comprises an amorphous phase; electrode.

2. The oxide includes at least one selected from the group consisting of titanium oxide and a composite oxide containing titanium and niobium.

2. The electrode of claim 1.

3. The solid electrolyte is Li 1+x A x Ge 2-x (P.O. 4 ) 3 (0≦x≦2) 2. The electrode of claim 1.

4. A positive electrode and A negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with The positive electrode or the negative electrode comprises the electrode according to claim 1 . battery.

5. The negative electrode comprises the electrode, 5. The battery of claim 4.

6. sintering a compact of a mixture of an electrode active material and a solid electrolyte; The electrode active material includes particles of an oxide that contains titanium and does not contain lithium, The oxide particles have a median diameter of more than 3 μm and less than 10 μm. A method for manufacturing an electrode.

7. a ratio of a median diameter of the particles of the oxide to a median diameter of the particles of the solid electrolyte is 2 or more and 30 or less; A method for producing the electrode according to claim 6.

8. The BET specific surface area of ​​the particles of the oxide is 1 m 2 / g or more 7m 2 / g or less, A method for producing the electrode according to claim 6.

9. the particles of the oxide include primary particles and secondary particles, a ratio of an average particle size of the primary particles to a median particle size of the oxide particles is 0.6 or less; A method for producing the electrode according to claim 6.

10. Firing a laminate including a positive electrode green sheet, an electrolyte layer green sheet, and a negative electrode green sheet; the positive electrode green sheet or the negative electrode green sheet is a molded body of a mixture containing an electrode active material and a solid electrolyte, The electrode active material includes particles of an oxide that contains titanium and does not contain lithium, The oxide particles have a median diameter of more than 3 μm and less than 10 μm. How batteries are manufactured.

11. An electrode active material; A solid electrolyte in contact with the electrode active material; Equipped with The electrode active material includes an oxide that contains titanium and does not contain lithium, The oxide is present in the form of particles having a median diameter of more than 2 μm and less than 7 μm; The solid electrolyte is an oxide solid electrolyte. electrode.

12. The oxide comprises at least one selected from the group consisting of titanium oxide and a composite oxide containing titanium and niobium.

12. The electrode of claim 11.

13. The solid electrolyte has a composition of Li1+xAlxGe2-x(PO4)3 (0≦x≦2), 12. The electrode of claim 11.

14. A positive electrode, A negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with The positive electrode or the negative electrode comprises the electrode according to claim 11 . battery.

15. The negative electrode comprising the electrode.

15. The battery of claim 14.