JP2023125396A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery with a low internal resistance.SOLUTION: An all-solid battery comprises a sintered body having a positive electrode, a negative electrode, and a solid electrolyte layer between the positive and negative electrodes. The positive electrode contains LiCoO2. The solid electrolyte layer contains Li3+xSixP1-xO4 (0.4≤x≤0.8).SELECTED DRAWING: Figure 1

Description

The present invention relates to an all-solid-state battery.

In recent years, electronics technology has made remarkable progress, and portable electronic devices are becoming smaller, lighter, thinner, and more multifunctional. Along with this, there is a strong desire for batteries that serve as power sources for electronic devices to be smaller, lighter, thinner, and more reliable, and all-solid-state batteries that use solid electrolytes as electrolytes are attracting attention.

There are two types of all-solid-state batteries: thin-film types and bulk types. Thin film types are produced using thin film techniques such as physical vapor deposition (PVD) and sol-gel methods. The bulk mold is manufactured using a powder molding method, a sintering method, or the like. All-solid-state batteries have different applicable materials and different performances due to differences in manufacturing methods.

For example, Patent Document 1 discloses a sintered all-solid-state battery using an oxide-based solid electrolyte as the solid electrolyte. In the all-solid-state battery described in Patent Document 1, several materials that can be applied to the positive electrode active material layer and the solid electrolyte layer are proposed.

International Publication No. 2007/135790

Some of the all-solid-state batteries described in Patent Document 1 have high internal resistance.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an all-solid-state battery with low internal resistance.

In order to solve the above problem, the following means are provided.

(1) An all-solid-state battery according to a first aspect includes a sintered body having a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode, and the positive electrode includes LiCoO ₂ , the solid electrolyte layer includes Li _3+x Si _x P _1-x O ₄ (0.4≦x≦0.8).

(2) In the all-solid-state battery according to the above aspect, the positive electrode may further include a metal or alloy containing any one selected from the group consisting of Ag, Pd, Au, and Pt.

(3) In the all-solid-state battery according to the above aspect, the positive electrode includes a positive electrode current collector layer and a positive electrode active material layer in contact with the solid electrolyte layer, and the positive electrode current collector layer includes LiCoO ₂ and Ag, A metal or an alloy containing any one selected from the group consisting of Pd, Au, and Pt may also be included.

The all-solid-state battery according to the above embodiment has low internal resistance.

FIG. 1 is a cross-sectional view of an all-solid-state battery according to a first embodiment. FIG. 1 is an enlarged cross-sectional view of a characteristic portion of the all-solid-state battery according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of a characteristic portion of another example of the all-solid-state battery according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of a characteristic portion of the positive electrode of another example of the all-solid-state battery according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of a characteristic portion of the positive electrode of another example of the all-solid-state battery according to the first embodiment. FIG. 3 is an enlarged cross-sectional view of a characteristic portion of another example of the all-solid-state battery according to the first embodiment.

Hereinafter, this embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following explanation, characteristic parts of the present invention may be shown enlarged for convenience in order to make it easier to understand, and the dimensional ratio of each component may differ from the actual one. be. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be implemented with appropriate changes within the scope of the invention.

Define direction. The stacking direction of the laminate 4 is defined as the z direction, one direction in the plane orthogonal to the z direction is defined as the x direction, and the direction orthogonal to the x direction and the z direction is defined as the y direction. Hereinafter, one direction in the z direction may be referred to as "up" and the opposite direction to this direction may be referred to as "down". Up and down do not necessarily correspond to the direction in which gravity is applied.

FIG. 1 is a schematic cross-sectional view of an all-solid-state battery 10 according to this embodiment. The all-solid-state battery 10 includes a laminate 4 and terminal electrodes 5 and 6. Terminal electrodes 5 and 6 are in contact with opposing surfaces of laminate 4, respectively. The terminal electrodes 5 and 6 extend in the z direction that intersects (orthogonally) the laminated surface of the laminated body 4.

The laminate 4 includes a positive electrode 1 , a negative electrode 2 , and a solid electrolyte layer 3 . The laminate 4 is a sintered body in which the positive electrode 1, the negative electrode 2, and the solid electrolyte layer 3 are laminated and sintered. The number of layers of the positive electrode 1 and the negative electrode 2 does not matter. Solid electrolyte layer 3 is located at least between positive electrode 1 and negative electrode 2. For example, the same solid electrolyte as the solid electrolyte layer 3 is present between the positive electrode 1 and the terminal electrode 6 and between the negative electrode 2 and the terminal electrode 5. The positive electrode 1 has one end connected to a terminal electrode 5. The negative electrode 2 has one end connected to the terminal electrode 6.

The all-solid-state battery 10 is charged or discharged by transferring ions between the positive electrode 1 and the negative electrode 2 via the solid electrolyte layer 3 . Although FIG. 1 shows a stacked type battery, a wound type battery may also be used. The all-solid-state battery 10 is used, for example, as a laminate battery, a square battery, a cylindrical battery, a coin battery, a button battery, or the like. Further, the all-solid-state battery 10 may be of a liquid injection type in which the solid electrolyte layer 3 is dissolved or dispersed in a solvent.

"Positive electrode"
FIG. 2 is an enlarged view of characteristic parts of the all-solid-state battery 10 according to the first embodiment. The positive electrode 1 includes, for example, a positive electrode current collector layer 1A and a positive electrode active material layer 1B.

[Positive electrode current collector layer]
The positive electrode current collector layer 1A includes, for example, a current collector 11 and a positive electrode active material 12. In this case, the area between the xy plane passing through the top of the current collector 11 and the xy plane passing through the bottom of the current collector 11 is regarded as the positive electrode current collector layer 1A.

The current collector 11 is made up of a plurality of current collector particles. The plurality of current collector particles are connected to each other and electrically connected in the xy plane. The positive electrode 1 includes, as the current collector 11, a metal or alloy containing any one selected from the group consisting of Ag, Pd, Au, and Pt. These metals or alloys do not melt even when the laminate 4 is heated in the air, and are difficult to oxidize. The current collector 11 is made of, for example, AgPd alloy, Au, or Pt.

The positive electrode active material 12 is mixed together with the current collector 11 in the positive electrode current collector layer 1A. The positive electrode active material 12 is in contact with the current collector 11 . When the positive electrode active material 12 is contained in the positive electrode current collector layer 1A, the transfer of electrons from the positive electrode active material 12 to the current collector 11 becomes smooth. The positive electrode 1 includes lithium cobalt oxide as the positive electrode active material 12. Lithium cobalt oxide is expressed as LiCoO ₂ and deviations from the stoichiometric composition are allowed.

Although FIG. 2 shows an example in which the current collector 11 is composed of a plurality of current collector particles, the current collector 11 is not limited to this case. FIG. 3 is an enlarged view of characteristic parts of another example of the all-solid-state battery according to the first embodiment. The positive electrode current collector layer 1C shown in FIG. 3 consists of a current collector 11. The current collector 11 may be in the form of a foil, a punched film, or an expanded film that spreads in the xy plane.

[Cathode active material layer]
The positive electrode active material layer 1B is formed on one or both sides of the positive electrode current collector layer 1A. The positive electrode active material layer 1B includes a positive electrode active material. The positive electrode active material layer 1B may include a conductive aid, a binder, and the solid electrolyte described above. When the positive electrode active material layer 1B includes a solid electrolyte, the boundary between the xy plane passing through the outermost part of the positive electrode active material and the boundary with the positive electrode current collector layer 1A (the xy plane passing through the outermost part of the positive electrode current collector) is , is regarded as the positive electrode active material layer 1B.

(Cathode active material)
The positive electrode active material is lithium cobalt oxide. Lithium cobalt oxide is expressed as LiCoO ₂ and deviations from the stoichiometric composition are allowed.

(Conductivity aid)
The conductive aid is not particularly limited as long as it improves the electron conductivity within the positive electrode active material layer 1B, and any known conductive aid can be used. Examples of conductive additives include carbon-based materials such as graphite, carbon black, graphene, and carbon nanotubes, metals such as gold, platinum, silver, palladium, aluminum, copper, nickel, stainless steel, and iron, and conductive oxides such as ITO. or a mixture thereof. The conductive aid may be in the form of powder or fiber.

(Binder)
The binding material bonds the various materials that constitute the positive electrode current collector layer 1A and the positive electrode active material layer 1B, the positive electrode active material layer 1B and the solid electrolyte layer 3, and the positive electrode active material layer 1B.

The binder can be used within a range that does not impair the function of the positive electrode active material layer 1B. The binder may not be included if unnecessary. The content of the binder in the positive electrode active material layer 1B is, for example, 0.5 to 30% by volume of the positive electrode active material layer. When the content of the binder is sufficiently small, the resistance of the positive electrode active material layer 1B becomes sufficiently low. Here, the volume % substantially matches the area % in a cross section measured with a scanning electron microscope, for example. Therefore, the area ratio in the cross section measured with a scanning electron microscope can be directly regarded as the volume ratio.

The binding material may be any material that can perform the above-mentioned bonding, and examples thereof include fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Furthermore, in addition to the above, as a binder, for example, cellulose, styrene/butadiene rubber, ethylene/propylene rubber, polyimide resin, polyamideimide resin, etc. may be used. Furthermore, a conductive polymer having electronic conductivity or an ion conductive polymer having ionic conductivity may be used as the binder. Examples of the conductive polymer having electron conductivity include polyacetylene. In this case, since the binder also functions as a conductive aid, there is no need to add a conductive aid. As the ion conductive polymer having ion conductivity, for example, those that conduct lithium ions etc. can be used, and polymer compounds (polyether polymer compounds such as polyethylene oxide and polypropylene oxide, polyphosphazene, etc.) can be used. etc.) and a lithium salt such as LiClO ₄ , LiBF ₄ , LiPF ₆ or an alkali metal salt mainly composed of lithium. Examples of the polymerization initiator used in the composite include photopolymerization initiators and thermal polymerization initiators that are compatible with the above monomers. Properties required of the binder include resistance to oxidation and reduction, and good adhesion.

Although specific examples of the positive electrode have been shown so far, the positive electrode is not limited to these examples. For example, FIGS. 4 and 5 are cross-sectional views of other examples of the positive electrode according to the first embodiment.

The positive electrode shown in FIG. 4 includes a positive electrode current collector layer 1D and a positive electrode active material layer 1B. The positive electrode current collector layer 1D includes a current collector 11, a positive electrode active material 12, and an oxide 13. The oxide 13 is, for example, an oxide containing Ag, and is AgCoO ₂ . The oxide 13 prevents Ag contained in the current collector 11 from being oxidized. When the oxide 13 is present between the current collector 11 and the positive electrode active material 12, the cycle characteristics of the all-solid-state battery 10 are improved.

The positive electrode shown in FIG. 5 includes a positive electrode current collector layer 1E, an intermediate layer 1F, and a positive electrode active material layer 1B. The positive electrode current collector layer 1E includes a current collector 11 and an oxide 13. The intermediate layer 1F is made of oxide 13. The example shown in FIG. 5 corresponds to the case where the thickness of the oxide 13 is thicker than the example shown in FIG. The oxide 13 prevents oxidation of Ag contained in the current collector 11, and improves the cycle characteristics of the all-solid-state battery 10.

"Solid electrolyte layer"
Solid electrolyte layer 3 includes a solid electrolyte. A solid electrolyte is a material that can move ions by an externally applied electric field. For example, the solid electrolyte layer 3 conducts lithium ions and inhibits the movement of electrons. The solid electrolyte layer 3 is, for example, a sintered body obtained by sintering.

The solid electrolyte layer 3 contains Li _3+x Si _x P _1-x O ₄ (0.4≦x≦0.8) as a solid electrolyte. Li _3+x Si _x P _1-x O ₄ (0.4≦x≦0.8) has a γ-Li ₃ PO ₄ structure and has excellent ionic conductivity.

"Negative electrode"
The negative electrode 2 includes, for example, a negative electrode current collector layer 2A and a negative electrode active material layer 2B containing a negative electrode active material.

[Negative electrode current collector]
The negative electrode current collector layer 2A includes, for example, a current collector 21 and a negative electrode active material 22. In this case, the area between the xy plane passing through the top of the current collector 21 and the xy plane passing through the bottom thereof is regarded as the negative electrode current collector layer 2A. Current collector 21 is made of the same material as current collector 11 . As shown in FIG. 3, the negative electrode current collector layer 2C may be a foil in which the current collector 21 spreads in the xy plane, or may be in a punched or expanded form.

The negative electrode active material 22 is mixed together with the current collector 21 in the negative electrode current collector layer 2A. The negative electrode active material 22 is in contact with the current collector 21 . When the negative electrode active material 22 is contained in the negative electrode current collector layer 2A, the transfer of electrons from the negative electrode active material 22 to the current collector 21 becomes smooth. The negative electrode active material 22 is the same as the negative electrode active material contained in the negative electrode active material layer 2B described later.

[Negative electrode active material layer]
The negative electrode active material layer 2B is formed on one or both sides of the negative electrode current collector layer 2A. The negative electrode active material layer 2B contains a negative electrode active material. The negative electrode active material layer 2B may include a conductive aid, a binder, and the solid electrolyte described above. When the negative electrode active material layer 2B includes a solid electrolyte, the boundary between the xy plane passing through the outermost part of the negative electrode active material and the boundary with the negative electrode current collector layer 2A (the xy plane passing through the outermost part of the negative electrode current collector) is It is regarded as the negative electrode active material layer 2B.

(Negative electrode active material)
The negative electrode active material is a compound that can absorb and release ions. The negative electrode active material is a compound that exhibits a lower potential than the positive electrode active material. Examples of the negative electrode active material include Li ₄ Ti ₅ O ₁₂ , LiTiO ₂ , Li ₂ TiO ₃ , and Li ₂ TiSiO ₅ .

(Conductivity aid)
The conductive aid improves the electronic conductivity of the negative electrode active material layer 2B. The same material as the positive electrode active material layer 1B can be used as the conductive aid.

(Binder)
The binding material joins various materials forming the negative electrode current collector layer 2A and the negative electrode active material layer 2B, the negative electrode active material layer 2B and the solid electrolyte layer 3, and the negative electrode active material layer 2B. As the binder, the same material as the positive electrode active material layer 1B can be used. The content ratio of the binder can also be the same as in the positive electrode active material layer 1B. If the binder is unnecessary, it may not be included.

Although FIG. 2 shows an example in which the negative electrode 2 includes the negative electrode current collector layer 2A and the negative electrode active material layer 2B, the present invention is not limited to this case. FIG. 6 is an enlarged view of a characteristic portion of another example of the all-solid-state battery according to the first embodiment. The negative electrode 2D shown in FIG. 6 includes a current collector 21 and a solid electrolyte 23. The current collector 21 is an AgPd alloy. The AgPd alloy also functions as an active material. When the AgPd alloy functions as a negative electrode active material, the all-solid-state battery has a high capacity and the energy density of the all-solid-state battery improves.

“Method for manufacturing all-solid-state batteries”
Next, a method for manufacturing the all-solid-state battery 10 will be explained. First, the laminate 4 is produced. The laminate 4 is produced, for example, by a simultaneous firing method or a sequential firing method.

The simultaneous firing method is a method in which the materials forming each layer are laminated and then fired all at once to produce the laminate 4. The sequential firing method is a method in which firing is performed each time each layer is formed. The simultaneous firing method allows the laminate 4 to be produced in fewer work steps than the sequential firing method. Further, the laminate 4 produced by the simultaneous firing method is denser than the laminate 4 produced by the sequential firing method. Hereinafter, a case where the simultaneous firing method is used will be explained as an example.

First, each material of the positive electrode current collector layer 1A, the positive electrode active material layer 1B, the solid electrolyte layer 3, the negative electrode active material layer 2B, and the negative electrode current collector layer 2A constituting the laminate 4 is made into a paste. In the case of the example shown in FIG. 4, the current collector 11 is coated with the oxide 13 and then made into a paste. In the case of the example shown in FIG. 5, the material constituting the intermediate layer 1F is also made into a paste.

The method of forming each material into a paste is not particularly limited, and for example, a method may be used to obtain a paste by mixing powders of each material in a vehicle. Here, the vehicle is a general term for a medium in a liquid phase. Vehicles include solvents and binders.

Next, a green sheet is produced. Green sheets are obtained by applying a paste prepared for each material onto a base material such as PET (polyethylene terephthalate) film, drying it as necessary, and then peeling off the base material. . The method for applying the paste is not particularly limited, and for example, known methods such as screen printing, coating, transfer, and doctor blade can be used.

Next, green sheets produced for each material are stacked in a desired order and number of layers to produce a laminated sheet. When stacking green sheets, alignment and cutting are performed as necessary. For example, when producing a parallel type or series-parallel type battery, alignment is performed so that the end face of the positive electrode current collector layer 1A and the end face of the negative electrode current collector layer 2A do not match, and the respective green sheets are stacked. .

The laminated sheet may be manufactured using a method in which a positive electrode unit and a negative electrode unit are manufactured and then these units are laminated. The positive electrode unit is a laminated sheet in which a solid electrolyte layer 3, a positive electrode active material layer 1B, a positive electrode current collector layer 1A, and a positive electrode active material layer 1B are laminated in this order. In the case of the example shown in FIG. 5, an intermediate layer 1F is laminated between the positive electrode current collector layer 1A and the positive electrode active material layer 1B. The negative electrode unit is a laminated sheet in which a solid electrolyte layer 3, a negative electrode active material layer 2B, a negative electrode current collector layer 2A, and a negative electrode active material layer 2B are laminated in this order. The solid electrolyte layer 3 of the positive electrode unit and the negative electrode active material layer 2B of the negative electrode unit are stacked so as to face each other, or the positive electrode active material layer 1B of the positive electrode unit and the solid electrolyte layer 3 of the negative electrode unit are stacked so as to face each other.

Next, the produced laminated sheet is pressurized all at once to improve the adhesion of each layer. Pressure can be applied, for example, by a mold press, a hot water isostatic press (WIP), a cold water isostatic press (CIP), a hydrostatic press, or the like. It is preferable to pressurize while heating. The heating temperature during pressure bonding is, for example, 40 to 95°C. Next, the pressurized laminate is cut into chips using a dicing device. Then, the chips are subjected to a binder removal treatment and fired, thereby obtaining a laminate 4 made of a sintered body.

The binder removal process can be performed as a separate process from the firing process. When the binder removal step is performed, the binder component contained in the chip is thermally decomposed before the firing step, and rapid decomposition of the binder component during the firing step can be suppressed. The binder removal step is carried out, for example, by heating at a temperature of 300 to 800° C. for 0.1 to 10 hours in an air atmosphere. The atmosphere in the debinding step is an oxygen partial pressure environment in which the materials constituting the positive electrode, negative electrode, and solid electrolyte do not or cannot be easily oxidized, and the materials constituting the positive electrode, negative electrode, and solid electrolyte are under an oxygen partial pressure environment. The type of gas can be arbitrarily selected so as not to react with the gas. For example, it may be carried out in a nitrogen atmosphere, an argon atmosphere, a nitrogen-hydrogen mixed atmosphere, a water vapor atmosphere, or a mixture thereof.

The firing step is performed by placing the chip on a ceramic table, for example. Firing is performed, for example, by heating at 600 to 1000° C. in a nitrogen atmosphere. The firing time is, for example, 0.1 to 3 hours. The atmosphere of the sintering process is an oxygen partial pressure environment in which the materials constituting the positive electrode, negative electrode, and solid electrolyte do not or cannot be oxidized; The type of gas can be arbitrarily selected so that the gas does not react. For example, it may be carried out in a nitrogen atmosphere, an argon atmosphere, a nitrogen-hydrogen mixed atmosphere, a water vapor atmosphere, or a mixture thereof.

Alternatively, the sintered laminate 4 (sintered body) may be placed in a cylindrical container together with an abrasive material such as alumina, and barrel polishing may be performed. This allows the corners of the laminate to be chamfered. Polishing may be performed using sandblasting. Sandblasting is preferable because it allows you to remove only specific areas.

Terminal electrodes 5 and 6 are formed on mutually opposing side surfaces of the produced laminate 4. The terminal electrodes 5 and 6 can be formed using a sputtering method, a dipping method, a screen printing method, a spray coating method, or the like. The all-solid-state battery 10 can be manufactured through the steps described above. If the terminal electrodes 5 and 6 are to be formed only in predetermined portions, the above-described process is performed after masking with tape or the like.

The all-solid-state battery according to this embodiment has low internal resistance. This is considered to be because Li _3+x Si _x P _1-x O ₄ used in the solid electrolyte layer 3 and LiCoO ₂ used in the positive electrode active material layer 1B are difficult to react with each other. For example, when LiCoO ₂ is changed to LiMn ₂ O ₄ , an intermediate product is generated between the solid electrolyte layer 3 and the positive electrode active material layer 1B. This intermediate product is LiMn ₂ O ₄ or Li ₂ MnO ₃ containing excess Li, and is formed when Li in the solid electrolyte diffuses into the positive electrode active material layer 1B and reacts with the positive electrode active material. Ru. This intermediate product and the Li-deficient solid electrolyte cause an increase in the internal resistance of the all-solid-state battery. On the other hand, Li _3+x Si _x P _1-x O ₄ and LiCoO ₂ hardly react with each other and hardly produce intermediate products.

The embodiments of the present invention have been described above in detail with reference to the drawings, but each configuration and combination thereof in each embodiment is merely an example, and additions or omissions of configurations may be made within the scope of the spirit of the present invention. , substitutions, and other changes are possible.

"Example 1"
(Preparation of positive electrode paste)
To prepare the positive electrode current collector layer paste, a powder containing Ag, Pd, and LiCoO ₂ mixed in a mass ratio of 40:10:50 was used. Ethyl cellulose and dihydroterpineol were added to this powder and mixed. Ethylcellulose is the binder and dihydroterpineol is the solvent.

The positive electrode active material layer paste was prepared by adding and mixing ethyl cellulose and dihydroterpineol to LiCoO ₂ .

(Preparation of solid electrolyte layer paste)
Li ₂ CO ₃ , SiO ₂ and Li ₃ PO ₄ were used as starting materials and mixed at a molar ratio of 2:1:1. The mixture was wet-mixed for 16 hours using a ball mill using water as a dispersion medium. The mixture was calcined at 950° C. for 2 hours to produce Li _3.5 Si _0.5 P _0.5 O ₄ . Then, 100 parts by mass of this calcined powder, 100 parts by mass of ethanol, and 200 parts by mass of toluene were added to a ball mill and wet mixed. Then, 16 parts of a polyvinylbutyral binder and 4.8 parts by mass of benzylbutyl phthalate were further added and mixed to prepare a solid electrolyte layer paste.

(Preparation of negative electrode paste)
The negative electrode paste used was a powder in which Ag, Pd, and Li _3.5 Si _0.5 P _0.5 O ₄ were mixed in a mass ratio of 40:10:50. Ethyl cellulose and dihydroterpineol were added to this powder and mixed.

(Production of all-solid-state battery)
Next, a positive electrode unit and a negative electrode unit were produced according to the following procedure. First, a positive electrode active material paste was printed on the solid electrolyte layer sheet to a thickness of 5 μm using screen printing. Next, the printed positive electrode active material paste was dried at 80° C. for 5 minutes. Then, on the dried positive electrode active material paste, a current collector paste was printed to a thickness of 5 μm using screen printing. Next, the printed positive electrode current collector paste was dried at 80° C. for 5 minutes. Then, on the dried positive electrode current collector paste, a positive electrode active material paste was printed again to a thickness of 5 μm using screen printing, and then dried. Thereafter, the PET film was peeled off. In this way, a positive electrode unit was obtained in which the positive electrode active material layer/positive electrode current collector layer/positive electrode active material layer were laminated in this order on the main surface of the solid electrolyte layer.

Next, a negative electrode paste was printed on the main surface of the solid electrolyte layer to a thickness of 10 μm. Next, the printed negative electrode paste was dried at 80° C. for 5 minutes.

As a laminate, a solid electrolyte unit was prepared by stacking five solid electrolyte layer sheets. Fifty electrode units (25 positive electrode units, 25 negative electrode units) were stacked alternately to sandwich the solid electrolyte unit. At this time, each unit is arranged so that the current collector layer of the odd-numbered electrode unit extends only to one end surface, and the current collector layer of the even-numbered electrode unit extends only to the opposite end surface. Staggered and stacked. Six solid electrolyte layer sheets were stacked on top of this stacked unit. Thereafter, this was molded by thermocompression bonding and then cut to produce a laminated chip. Thereafter, the laminated chips were co-fired to obtain a laminated body. For simultaneous firing, the temperature was raised to a firing temperature of 800° C. at a temperature increase rate of 200° C./hour in a nitrogen atmosphere, maintained at that temperature for 2 hours, and allowed to cool naturally after firing.

Terminal electrodes 5 and 6 were attached to the sintered laminate (sintered body) by a known method to produce an all-solid-state battery. The manufactured all-solid-state battery had the configuration shown in FIG. 6.

100 similar samples were made and the internal resistance was determined. Internal resistance was determined as the average of these samples. The internal resistance is determined by constant current charging (CC charging) at a constant current of 0.2C rate until the battery voltage reaches 4.0V in an environment of 25°C, then after a 1-minute break, charging at a constant current of 0.2C rate. It was determined by dividing the voltage drop (V) from the time of rest to the start of discharge by the discharge current (A) when discharging (CC discharge) until the battery voltage reaches 0V at a constant current of .

"Example 2"
Example 2 differs from Example 1 in that a powder of Au and LiCoO ₂ mixed at a mass ratio of 50:50 was used to prepare the positive electrode current collector paste. Other conditions were the same as in Example 1 to determine the internal resistance.

"Example 3"
Example 3 differs from Example 1 in that a powder of Pt and LiCoO ₂ mixed at a mass ratio of 50:50 was used when producing the positive electrode current collector paste. Other conditions were the same as in Example 1 to determine the internal resistance.

"Example 4"
Example 4 differs from Example 1 in that a powder containing Ag and Pd mixed at a mass ratio of 80:20 was used to prepare the positive electrode current collector paste (LiCoO ₂ was not added). different. Other conditions were the same as in Example 1 to determine the internal resistance.

"Examples 5 to 9"
Examples 5 to 9 differ from Example 1 in that the mixing ratio of Li ₂ CO ₃ , SiO ₂ , and Li ₃ PO ₄ was changed when producing the solid electrolyte layer paste. Examples 5 to 9 differ from Example 1 in the composition ratio of the solid electrolyte layer. Other conditions were the same as in Example 1 to determine the internal resistance.

“Comparative Example 1”
Comparative Example 1 differs from Example 1 in the following points. In Comparative Example 1, the internal resistance was determined in the same manner as in Example 1.
Difference 1: To prepare the positive electrode current collector layer paste, a powder containing Ag and Pd mixed at a mass ratio of 80:20 was used.
Difference 2: The solid electrolyte used in the solid electrolyte paste was changed to Li _3.5 Ge _0.5 V _0.5 O ₄ .
Difference 3: The negative electrode paste was made into two layers: a negative electrode current collector layer paste and a negative electrode active material layer paste. As the negative electrode current collector layer paste, a powder containing Ag and Pd mixed at a mass ratio of 80:20 was used. The negative electrode active material layer paste was prepared by adding and mixing ethyl cellulose and dihydroterpineol to Li ₄ Ti ₅ O ₁₂ (Li _4/3 Ti _5/3 O ₄ ).
The all-solid-state battery after fabrication had the configuration shown in FIG. 3.

“Comparative Example 2”
Comparative Example 2 differs from Comparative Example 1 in that LiMn ₂ O ₄ was used as the positive electrode active material and Li _3.5 Si _0.5 P _0.5 O ₄ was used as the solid electrolyte. In Comparative Example 2, the internal resistance was determined in the same manner as in Example 1.

“Comparative Example 3”
Comparative Example 3 differs from Example 1 in that LiMn ₂ O ₄ was used as the positive electrode active material. In Comparative Example 3, the internal resistance was determined in the same manner as in Example 1.

The results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1 below.

Comparing Example 1 with Comparative Examples 1 and 3, Example 1 had a lower internal resistance than Comparative Examples 1 and 3. In Comparative Example 1 and Comparative Example 3, it is thought that the positive electrode active material and the solid electrolyte reacted and an intermediate product was generated. Furthermore, Examples 1 to 9 and Comparative Example 3 in which the AgPd alloy functions as the negative electrode active material have lower output voltage than Comparative Examples 1 and 2 in which Li _4/3 Ti _5/3 O ₄ functions as the negative electrode active material. was big. Moreover, when Example 1 and Example 4 were compared, when the positive electrode current collector layer contained the positive electrode active material, the internal resistance became lower. Further, when comparing Example 1 and Examples 5 to 9, the internal resistance changed depending on the composition of the solid electrolyte.

1... Positive electrode, 1A, 1C, 1D, 1E... Positive electrode current collector layer, 1B... Positive electrode active material layer, 1F... Intermediate layer, 2, 2D... Negative electrode, 2A, 2C... Negative electrode current collector layer, 2B... Negative electrode active Material layer, 3... Solid electrolyte layer, 4... Laminated body, 5, 6... Terminal electrode, 10... All-solid battery, 11, 21... Current collector, 12... Positive electrode active material, 13... Oxide, 22... Negative electrode active Substance, 23...Solid electrolyte

Claims (3)

A sintered body having a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode,
The positive electrode includes _LiCoO2 ,
An all-solid-state battery, wherein the solid electrolyte layer contains Li _3+x Si _x P _1-x O ₄ (0.4≦x≦0.8). The all-solid-state battery according to claim 1, wherein the positive electrode further includes a metal or an alloy selected from the group consisting of Ag, Pd, Au, and Pt. The positive electrode includes a positive current collector layer and a positive active material layer in contact with the solid electrolyte layer,
The all-solid-state battery according to claim 1 or 2, wherein the positive electrode current collector layer contains LiCoO ₂ and a metal or alloy containing any one selected from the group consisting of Ag, Pd, Au, and Pt.

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