WO2023176967A1 - 固体電解質層、及び全固体二次電池 - Google Patents

固体電解質層、及び全固体二次電池 Download PDF

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Publication number
WO2023176967A1
WO2023176967A1 PCT/JP2023/010634 JP2023010634W WO2023176967A1 WO 2023176967 A1 WO2023176967 A1 WO 2023176967A1 JP 2023010634 W JP2023010634 W JP 2023010634W WO 2023176967 A1 WO2023176967 A1 WO 2023176967A1
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Prior art keywords
solid electrolyte
phase region
layer
positive electrode
solid
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PCT/JP2023/010634
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English (en)
French (fr)
Japanese (ja)
Inventor
啓子 竹内
禎一 田中
泰輔 益子
岳夫 塚田
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TDK Corp
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TDK Corp
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Priority to JP2024508280A priority Critical patent/JPWO2023176967A1/ja
Priority to CN202380027197.5A priority patent/CN118946936A/zh
Priority to EP23770919.1A priority patent/EP4495953A4/en
Publication of WO2023176967A1 publication Critical patent/WO2023176967A1/ja
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H01B1/08—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a solid electrolyte layer and an all-solid secondary battery.
  • the sulfide-based solid electrolyte Since the sulfide-based solid electrolyte has excellent plasticity, it is possible to form an interface between the solid electrolyte and the active material by compacting it. However, sulfide-based solid electrolytes generate hydrogen sulfide when they react with water, which poses a safety problem.
  • oxide-based solid electrolytes are safe as there is no risk of generating hydrogen sulfide due to reaction with water.
  • oxide-based solid electrolytes are safe as there is no risk of generating hydrogen sulfide due to reaction with water.
  • it is necessary to make it dense, and for this purpose, it is necessary to sinter it at a high temperature.
  • the oxide solid electrolyte and active material react, forming a reaction layer with low ionic conductivity at the interface between the oxide solid electrolyte and the active material. may be generated.
  • LSPO Li 3+x Si x P 1-x O 4
  • LSPO has a problem in that its ionic conductivity is as low as 1 ⁇ 10 ⁇ 6 S/cm (see Non-Patent Document 2).
  • the solid electrolyte layer according to one embodiment of the present invention includes a first phase region containing a first solid electrolyte containing Li, Si, P, and O and having a ⁇ -Li 3 PO 4 type crystal structure;
  • a second phase region includes a second solid electrolyte containing Li, Si, P, and O, having a composition different from that of the first solid electrolyte, and having a Li 4 SiO 4 type crystal structure.
  • the ratio of the volume of the first phase region to the volume of the second phase region is preferably 0.1 or more and 9 or less.
  • the ratio of the number of Si atoms to the number of P atoms contained in the first phase region is 0.1 or more and less than 1.5. It is preferable that [4] In the solid electrolyte layer according to any one of [1] to [3] above, the ratio of the number of Si atoms to the number of P atoms contained in the second phase region is 1.5 or more and 9 or less. It is preferable that
  • An all-solid-state secondary battery includes the solid electrolyte layer according to any one of [1] to [4] above, a positive electrode layer sandwiching the solid electrolyte layer, and a negative electrode layer. Equipped with.
  • the solid electrolyte layer of the present invention includes a first phase region including a first solid electrolyte containing Li, Si, P, and O and having a ⁇ -Li 3 PO 4 type crystal structure; and a second phase region including a second solid electrolyte having a composition different from that of the first solid electrolyte and having a Li 4 SiO 4 type crystal structure. Therefore, the solid electrolyte layer of the present invention has high ionic conductivity. Therefore, the all-solid-state secondary battery including the solid electrolyte layer of the present invention, the positive electrode layer sandwiching the solid electrolyte layer, and the negative electrode layer has good ionic conductivity.
  • FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a first embodiment.
  • FIG. 2 is a schematic cross-sectional view showing an enlarged part of the solid electrolyte layer 3 of the all-solid-state secondary battery 10 shown in FIG. 1.
  • FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a first embodiment.
  • FIG. 2 is a schematic cross-sectional view showing an enlarged part of the solid electrolyte layer 3 of the all-solid-state secondary battery 10 shown in FIG. 1.
  • FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a first embodiment.
  • FIG. 2 is a schematic cross-sectional view showing an enlarged part of the solid electrolyte layer 3 of the all-solid-state secondary battery 10 shown in FIG. 1.
  • FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery according to a first embodiment.
  • FIG. 2 is
  • the present inventor focused on the relationship between the crystal structure and ionic conductivity in a solid electrolyte layer containing an oxide-based solid electrolyte containing Li, Si, P, and O, and conducted extensive studies. layered.
  • a first phase region containing Li, Si, P and O and containing a first solid electrolyte having a ⁇ -Li 3 PO 4 type crystal structure In a solid electrolyte layer having a second phase region including a second solid electrolyte having a composition different from that of the first solid electrolyte and having a Li 4 SiO 4 type crystal structure, only the first phase region or the second phase region.
  • the inventors have discovered that the ionic conductivity is higher than that of a solid electrolyte layer consisting only of solid electrolyte layers, and have devised the present invention.
  • FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery 10 of this embodiment.
  • the all-solid-state secondary battery 10 includes a laminate 4 , a first external terminal 5 , and a second external terminal 6 .
  • the first external terminal 5 and the second external terminal 6 are made of a conductive material.
  • the first external terminal 5 and the second external terminal 6 are in contact with opposing surfaces of the laminate 4, respectively.
  • the first external terminal 5 and the second external terminal 6 extend in a direction intersecting (perpendicular to) the laminated surface of the laminated body 4 .
  • the laminate 4 includes a positive electrode layer 1 , a negative electrode layer 2 , and a solid electrolyte layer 3 sandwiched between the positive electrode layer 1 and the negative electrode layer 2 .
  • the laminate 4 is a sintered body in which a positive electrode layer 1 and a negative electrode layer 2 are laminated with a solid electrolyte layer 3 in between and sintered.
  • the number of positive electrode layers 1 and negative electrode layers 2 included in the laminate 4 may be one each, or two or more.
  • the solid electrolyte layer 3 is provided not only between the positive electrode layer 1 and the negative electrode layer 2, but also between the positive electrode layer 1 and the second external terminal 6, and between the negative electrode layer 2 and the first external terminal 5. There is also in between. Further, as shown in FIG. 1, one end of the positive electrode layer 1 is connected to the first external terminal 5.
  • the negative electrode layer 2 has one end connected to the second external terminal 6.
  • the all-solid-state secondary battery 10 is charged or discharged by transferring ions between the positive electrode layer 1 and the negative electrode layer 2 via the solid electrolyte layer 3.
  • Solid electrolyte layer The solid electrolyte layer 3 can move ions by an externally applied electric field.
  • the solid electrolyte forming the solid electrolyte layer 3 is a substance (for example, particles) that can move ions by an externally applied electric field.
  • FIG. 2 is a schematic cross-sectional view showing a part of the solid electrolyte layer 3 of the all-solid-state secondary battery 10 shown in FIG. 1 in an enlarged manner. As shown in FIG. 2, the solid electrolyte layer 3 has a first phase region 31 and a second phase region 32.
  • the first phase region 31 includes a first solid electrolyte containing Li, Si, P, and O, and having a ⁇ -Li 3 PO 4 type crystal structure.
  • the first phase region 31 may be made of a first solid electrolyte.
  • the second phase region 32 includes a second solid electrolyte that includes Li, Si, P, and O, has a composition different from that of the first solid electrolyte, and has a Li 4 SiO 4 type crystal structure.
  • the second phase region 32 may be made of a second solid electrolyte. It is preferable that the solid electrolyte layer 3 consists of only a first phase region 31 and a second phase region 32.
  • the solid electrolyte layer 3 may include regions other than the first phase region 31 and the second phase region 32 as long as the effects of the present invention are not impaired.
  • the regions other than the first phase region 31 and the second phase region 32 may be made of a metal oxide having a composition and crystal structure different from those of the first phase region 31 and the second phase region 32, for example.
  • the first phase region 31 and the second phase region 32 may be distributed uniformly or unevenly. It is preferable that the first phase region 31 and the second phase region 32 are distributed substantially uniformly, since this facilitates contact with the first phase region 31 and the second phase region 32 and increases the area of the interface between the first phase region 31 and the second phase region 32. Moreover, the shape and size of the first phase region 31 and the second phase region 32 are not particularly limited, and may be in the form of irregular particles, for example, as shown in FIG. 2.
  • reference numerals 33 indicate grain boundaries between the first phase region 31 and the second phase region 32, between the first phase regions 31, and between the second phase regions 32.
  • a grain boundary layer 33a with high ion conductivity is formed in the grain boundary 33 between the first phase region 31 and the second phase region 32.
  • the grain boundary layer 33a includes a first phase region 31 including a first solid electrolyte having a ⁇ -Li 3 PO 4 type crystal structure, and a second phase region 31 including a second solid electrolyte having a Li 4 SiO 4 type crystal structure. Since the crystal phase is different from that of the region 32, it is estimated that it is formed at the interface between the first phase region 31 and the second phase region 32. Therefore, for example, if the solid electrolyte layer has only one crystal phase, such as a case where the solid electrolyte layer consists of only one of the first phase region 31 and the second phase region 32, a grain boundary layer with high ionic conductivity is not formed. . Therefore, a solid electrolyte layer having only one crystalline phase has a lower ionic conductivity than the solid electrolyte layer 3 of this embodiment in which a plurality of crystalline phases coexist.
  • the ratio between the volume of the first phase region 31 and the volume of the second phase region 32 (first phase region/second phase region) included in the solid electrolyte layer 3 is not particularly limited, but is 0.1 or more and 9 or less. It is preferably 0.25 or more and 4 or less, and even more preferably 0.5 or more and 1.5 or less.
  • the ratio of the volume of the first phase region 31 to the volume of the second phase region 32 is 0.1 or more and 9 or less, the first phase region 31 and the second phase region 32 are likely to come into contact with each other.
  • the area of the interface between the first phase region 31 and the second phase region 32 becomes larger, and many grain boundary layers 33a with high ionic conductivity are generated. Therefore, a solid electrolyte layer 3 having high ionic conductivity is formed.
  • the first solid electrolyte may be made of only Li, Si, P, and O, or may be made of ⁇ -Li 3 PO 4 type crystal, depending on the characteristics required for the all-solid secondary battery 10. At least one element selected from the group consisting of Ti, Co, Ni, and Mn may be included as long as the structure can be maintained.
  • the first phase region 31 also contains, for example, a sintering aid, the positive electrode layer 1 and/or the negative electrode layer 2 (the positive electrode layer 1 and the negative electrode layer 2), to the extent that the effects of the present invention are not impaired.
  • a component derived from the active material forming at least one of the layers 2) may be included.
  • the ratio of the number of Si atoms to the number of P atoms contained in the first phase region 31 is preferably 0.1 or more and less than 1.5, and Si/P is 0.8 or more and 1.5 or more. More preferably, it is 2 or less.
  • the ratio of the number of Si atoms to the number of P atoms (Si/P) contained in the first phase region 31 is 0.1 or more and less than 1.5, the first phase region 31 is stable (the bond is strong and Since it has a ⁇ -Li 3 PO 4 type crystal structure (hard to break), many grain boundary layers 33a with high ionic conductivity are generated at the interface with the second phase region 32. Therefore, a solid electrolyte layer 3 having high ionic conductivity is formed.
  • the second solid electrolyte may be made of only Li, Si, P, and O, or may have a Li 4 SiO 4 type crystal structure depending on the characteristics required for the all-solid secondary battery 10. At least one element selected from the group consisting of Ti, Co, Ni, and Mn may be included as long as it can be retained.
  • an active material forming the positive electrode layer 1 and/or the negative electrode layer 2, etc. in addition to the second solid electrolyte, for example, a sintering aid, an active material forming the positive electrode layer 1 and/or the negative electrode layer 2, etc. It may also contain components derived from.
  • the ratio of the number of Si atoms to the number of P atoms contained in the second phase region 32 is preferably 1.5 or more and 9 or less, and it is preferable that Si/P is 2 or more and 4 or less. More preferred.
  • the ratio of the number of Si atoms to the number of P atoms (Si/P) contained in the second phase region 32 is 1.5 or more and 9 or less, the second phase region 32 becomes a stable Li 4 SiO 4 type crystal. structure, many grain boundary layers 33a with high ionic conductivity are generated at the interface with the first phase region 31. Therefore, a solid electrolyte layer 3 having high ionic conductivity is formed.
  • the first solid electrolyte and the second solid electrolyte are used as the materials for the solid electrolyte layer 3.
  • a sintering aid may also be used.
  • the solid electrolyte layer 3 may contain a sintering aid that remains without being removed during the firing process or the like for manufacturing the laminate 4. Any known sintering aid may be used as long as it has the effect of improving sinterability.
  • the sintering aid include compounds containing lithium (Li), boron (B), zinc (Zn), bismuth (Bi), and the like.
  • the positive electrode layer 1 includes, for example, a positive electrode current collector 1A and a positive electrode active material layer 1B. As shown in FIG. 1, the positive electrode active material layer 1B may be formed on both sides of the positive electrode current collector 1A, or may be formed only on one side.
  • the positive electrode current collector 1A has excellent electrical conductivity.
  • the positive electrode current collector 1A is made of, for example, a metal such as silver, palladium, gold, platinum, aluminum, copper, nickel, stainless steel, or iron, or an alloy containing at least one of them.
  • the positive electrode current collector 1A may contain, for example, a positive electrode active material such as a lithium vanadium compound (LiV 2 O 5 , Li 3 V 2 (PO 4 ) 3 , LiVOPO 4 ).
  • 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 and a solid electrolyte.
  • the positive electrode active material is not particularly limited as long as it is capable of reversibly releasing and inserting lithium ions and deintercalating and inserting lithium ions.
  • positive electrode active materials used in known lithium ion secondary batteries can be used.
  • the positive electrode active material is preferably one or more selected from, for example, transition metal oxides and transition metal composite oxides.
  • a positive electrode active material that does not contain lithium may be used.
  • a negative electrode active material doped with metallic lithium and/or lithium ions (at least one of metallic lithium and lithium ions) is placed in the negative electrode layer 2 in advance, and an all-solid secondary material is used.
  • the battery 10 can be used by starting from discharge.
  • positive electrode active materials that do not contain lithium include metal oxides (MnO 2 , V 2 O 5 , etc.).
  • 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 aids 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 ITO (indium tin oxide). conductive oxides, or mixtures thereof.
  • the conductive aid may be in the form of powder or fiber.
  • solid electrolyte The solid electrolyte contained in the positive electrode active material layer 1B improves the ionic conductivity within the positive electrode active material layer 1B.
  • the solid electrolyte one or a mixture of two or more of known solid electrolytes can be used.
  • the solid electrolyte may be the same as the first solid electrolyte or second solid electrolyte used for the solid electrolyte layer 3 described above.
  • the negative electrode layer 2 includes, for example, a negative electrode current collector 2A and a negative electrode active material layer 2B. As shown in FIG. 1, the negative electrode active material layer 2B may be formed on both sides of the negative electrode current collector 2A, or may be formed only on one side.
  • the configuration of the negative electrode current collector 2A is similar to the configuration of the positive electrode current collector 1A.
  • 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 and a solid electrolyte.
  • 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.
  • the negative electrode active material the same material as the positive electrode active material can be used.
  • the negative electrode active material and the positive electrode active material used in the all-solid-state secondary battery 10 are determined in consideration of the potential of the negative electrode active material and the potential of the positive electrode active material.
  • 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.
  • solid electrolyte The solid electrolyte contained in the negative electrode active material layer 2B improves ion conduction within the negative electrode active material layer 2B.
  • the solid electrolyte one or a mixture of two or more of known solid electrolytes can be used.
  • the solid electrolyte may be the same as the first solid electrolyte or second solid electrolyte used for the solid electrolyte layer 3 described above.
  • the laminate 4 is produced.
  • the laminate 4 can be produced using, for example, a simultaneous firing method or a sequential firing method, and preferably produced using a simultaneous 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.
  • the laminate 4 produced by the simultaneous firing method is denser than the laminate 4 produced by the sequential firing method.
  • a method for manufacturing the laminate 4 will be described, taking as an example a case where the laminate 4 is manufactured using a co-firing method.
  • each material of the positive electrode current collector 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 2A that constitute the laminate 4 is made into a paste, and the paste is made into a paste corresponding to the material of each layer.
  • Manufacture paste is made into a paste corresponding to the material of each layer.
  • the paste of the solid electrolyte layer 3 is made by, for example, mixing particles made of the first solid electrolyte, particles made of the second solid electrolyte, and a sintering aid contained as necessary in a predetermined volume ratio. It can be obtained by turning a solid electrolyte material into a paste.
  • the method of turning each material used for manufacturing the laminate 4 into a paste is not particularly limited, and for example, a method of obtaining a paste by mixing powders of each material in a vehicle can be used.
  • the vehicle is a general term for a medium in a liquid phase.
  • the vehicle in this embodiment includes a solvent, a binder, and a plasticizer.
  • 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.
  • green sheets produced for each material are stacked in a desired order and number of layers to produce a laminated sheet.
  • alignment and cutting are performed as necessary.
  • alignment is performed so that the end face of the positive electrode current collector 1A and the end face of the negative electrode current collector 2A do not match, and the respective green sheets are stacked.
  • the green sheet that becomes the laminated sheet may be a positive electrode unit and a negative electrode unit that have been prepared in advance.
  • a paste for the solid electrolyte layer 3 is applied onto a base material such as a PET film using a doctor blade method, and dried to form a sheet-like solid electrolyte layer 3. do.
  • a paste for the positive electrode active material layer 1B is printed on the solid electrolyte layer 3 by screen printing and dried to form the positive electrode active material layer 1B.
  • a paste for the positive electrode current collector 1A is printed on the positive electrode active material 1B by screen printing and dried to form the positive electrode current collector 1A.
  • a paste for the positive electrode active material layer 1B is printed on the positive electrode current collector 1A by screen printing and dried to form the positive electrode active material layer 1B.
  • the positive electrode unit is a green sheet in which a solid electrolyte layer 3, a positive electrode active material layer 1B, a positive electrode current collector 1A, and a positive electrode active material layer 1B are laminated in this order.
  • a negative electrode unit is produced using the same procedure.
  • the negative electrode unit is a green sheet in which a solid electrolyte layer 3, a negative electrode active material layer 2B, a negative electrode current collector 2A, and a negative electrode active material layer 2B are laminated in this order.
  • the positive electrode unit and the negative electrode unit are laminated.
  • 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.
  • 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.
  • the positive electrode active material layer 1B, the positive electrode current collector 1A, the positive electrode active material layer 1B, the solid electrolyte layer 3, the negative electrode active material layer 2B, the negative electrode current collector 2A, the negative electrode active material layer 2B, and the solid electrolyte layer 3 a laminated sheet is obtained which is laminated in this order. Note that when stacking the positive electrode unit and the negative electrode unit, the positive electrode current collector 1A of the positive electrode unit and the negative electrode current collector 2A of the negative electrode unit are stacked while being alternately shifted.
  • the produced laminated sheet is pressurized all at once to improve the adhesion of each layer to form a laminated substrate.
  • 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 pressurization can be, for example, 40 to 95°C.
  • the laminated substrate obtained after pressurization is cut using a dicing device to form a laminated body. Thereafter, the obtained laminate is subjected to binder removal and firing steps. As a result, a laminate 4 made of a sintered body is obtained.
  • the binder removal and firing steps can be performed, for example, by placing the laminate on a ceramic table.
  • the binder removal and firing process can be, for example, a process of heating at 550° C. to 1100° C. in an air atmosphere.
  • the heating time (baking time) can be, for example, 0.1 to 6 hours.
  • the heating temperature and firing time in the binder removal and firing steps can be determined as appropriate depending on the composition of each layer constituting the laminate 4.
  • the heating temperature in the binder removal and firing process is 550° C. or higher, a grain boundary layer with high ionic conductivity is formed at the grain boundaries 33 between the first phase region 31 and the second phase region 32 of the solid electrolyte layer 3. 33a is easily formed, and a solid electrolyte layer 3 having high ionic conductivity is formed.
  • the heating temperature in the binder removal and firing steps is 1100° C. or lower, coarsening of the particles constituting the first phase region 31 and the second phase region 32 is suppressed, and the amount of the grain boundary layer 33a increases. As a result, a solid electrolyte layer 3 having a first phase region 31 and a second phase region 32 and having high ionic conductivity is formed.
  • the heating temperature in the binder removal and firing steps is preferably 600°C to 1000°C.
  • the sintered laminate 4 (sintered body) may be placed in a cylindrical container together with an abrasive material such as alumina, and polished by a barrel polishing method. Thereby, the corners of the laminate 4 can be chamfered.
  • the laminate 4 may be polished using sandblasting. Sandblasting is preferable because only a specific portion of the surface of the laminate 4 can be scraped.
  • the first external terminal 5 and the second external terminal 6 are formed on mutually opposing side surfaces of the produced laminate 4, respectively.
  • the first external terminal 5 and the second external terminal 6 can be formed using a method such as a sputtering method, a dipping method, a screen printing method, or a spray coating method, respectively.
  • the all-solid-state secondary battery 10 can be manufactured through the above steps.
  • the all-solid-state secondary battery 10 of the present embodiment includes a first phase region 31 containing a first solid electrolyte containing Li, Si, P, and O and having a ⁇ -Li 3 PO 4 type crystal structure; A solid electrolyte layer 3 having a second phase region 32 including a second solid electrolyte containing Si, P, and O, having a composition different from that of the first solid electrolyte, and having a Li 4 SiO 4 type crystal structure. have Therefore, the solid electrolyte layer 3 of the all-solid-state secondary battery 10 of this embodiment has high ionic conductivity.
  • the principle by which the solid electrolyte layer 3 with high ionic conductivity is formed is not certain, but in the firing process etc. in the manufacturing process of the all-solid-state secondary battery 10, the crystal phase It is presumed that this is because a grain boundary layer 33a with high ionic conductivity is generated at the interface between the first phase region 31 and the second phase region 32, which have different values.
  • Example 1 Li 2 CO 3 , SiO 2 and Li 3 PO 4 were prepared as starting materials. Li 2 CO 3 , SiO 2 , and Li 3 PO 4 were weighed out so that the molar ratio was 2:1:1, and wet-mixed for 16 hours using a ball mill with water as a dispersion medium. The resulting mixture was calcined at 1200° C. for 2 hours to obtain particles consisting of Li 3.5 Si 0.5 P 0.5 O 4 . The obtained particles were subjected to X-ray diffraction measurement using CuK ⁇ rays using an X-ray diffraction device (X'pert PRO manufactured by PANlytical), and it was confirmed that the particles had a ⁇ -Li 3 PO 4 type crystal structure. . Through the above steps, particles made of the first solid electrolyte of Example 1 were obtained.
  • Li 2 CO 3 , SiO 2 and Li 3 PO 4 were prepared as starting materials. Li 2 CO 3 , SiO 2 , and Li 3 PO 4 were weighed out so that the molar ratio was 6:3:1, and wet-mixed for 16 hours using a ball mill with water as a dispersion medium. The resulting mixture was calcined at 1200° C. for 2 hours to obtain particles consisting of Li 3.75 Si 0.75 P 0.25 O 4 . The obtained particles were subjected to X-ray diffraction measurement using CuK ⁇ rays using an X-ray diffraction device (X'pert PRO manufactured by PANlytical), and it was confirmed that the particles had a Li 4 SiO 4 type crystal structure. Through the above steps, particles made of the second solid electrolyte of Example 1 were obtained.
  • Example 2 to Example 7 In the same manner as in Example 1, except that the ratio of particles made of the first solid electrolyte and particles made of the second solid electrolyte used as the material of the solid electrolyte layer was changed to a total of 100% by volume, Solid electrolyte layers of Examples 2 to 7 consisting of fired bodies were obtained.
  • Examples 8 to 11 Li 3.55 Si 0 . _ _ 55 P 0.45 O 4 , Li 3.33 Si 0.33 P 0.67 O 4 , Li 3.09 Si 0.09 P 0.91 O 4 , Li 3.05 Si 0.05 P 0.95 Particles consisting of O 4 were obtained.
  • the obtained particles were subjected to X-ray diffraction measurement using CuK ⁇ rays using an X-ray diffraction device (X'pert PRO manufactured by PANlytical), and it was confirmed that the particles had a ⁇ -Li 3 PO 4 type crystal structure. .
  • X'pert PRO manufactured by PANlytical
  • Examples 12 to 15 Li 3.67 Si 0 . _ _ 67 P 0.33 O 4 , Li 3.83 Si 0.83 P 0.17 O 4 , Li 3.91 Si 0.91 P 0.09 O 4 , Li 3.95 Si 0.95 P 0.05 Particles consisting of O 4 were obtained.
  • the obtained particles were subjected to X-ray diffraction measurement using CuK ⁇ rays using an X-ray diffraction device (X'pert PRO manufactured by PANlytical), and it was confirmed that the particles had a Li 4 SiO 4 type crystal structure.
  • X'pert PRO manufactured by PANlytical
  • Comparative Example 1 A solid electrolyte layer of Comparative Example 1 made of a fired body was prepared in the same manner as in Example 1 except that 100% by volume of particles made of the first solid electrolyte and no particles made of the second solid electrolyte were used. Obtained.
  • Comparative Example 2 A solid electrolyte layer of Comparative Example 2 consisting of a fired body was obtained in the same manner as in Example 1 except that particles consisting of the first solid electrolyte were not used and 100% by volume of particles consisting of the second solid electrolyte were used. Ta.
  • the composition of the first solid electrolyte (first phase region 31), The ratio of the number of Si atoms to the number of P atoms (Si/P in the first phase region), the composition of the second solid electrolyte (second phase region 32), and the ratio of Si to the number of P atoms contained in the second phase region 32
  • Table 1 shows the ratio of the number of atoms (Si/P in the second phase region).
  • the first phase region 31 is indicated as region A
  • the second phase region 32 is indicated as region B. Further, 100% by volume is expressed as 1.
  • composition of the first phase region 31 in the solid electrolyte layer of Examples 1 to 15, Comparative Example 1, and Comparative Example 2 is the same as the first solid electrolyte used as the material of the first phase region 31. It can be considered. Furthermore, the crystal structure of the first solid electrolyte in the first phase region 31 can be considered to be the same as the first solid electrolyte used as the material for the first phase region 31.
  • the composition of the second phase region 32 in the solid electrolyte layer of Examples 1 to 15, Comparative Example 1, and Comparative Example 2 is the same as the second solid electrolyte used as the material of the second phase region 32. It can be considered as Further, the crystal structure of the second solid electrolyte in the second phase region 32 can be considered to be the same as the second solid electrolyte used as the material for the second phase region 32.
  • the volume ratio (volume %) of the first phase region 31 in the solid electrolyte layer 3 the solid electrolyte The volume ratio (volume %) of the second phase region 32 in the layer 3 and the ratio of the volume of the first phase region 31 to the volume of the second phase region 32 (first phase region/second phase region) were determined. The results are shown in Table 1.
  • the solid electrolyte layer 3 was cut to expose a cross section, and a clear cross section was obtained using a cross section polisher (CP). The obtained cross section was then observed at a magnification of 5,000 times using a scanning electron microscope (SEM) to obtain secondary electron composition images of 10 fields of view.
  • SEM scanning electron microscope
  • the particles with bright and dark contrasts in the obtained 10-field secondary electron composition images were analyzed for composition by energy dispersive X-ray analysis (EDS), and the first phase region 31 and second phase region 32 were analyzed. I determined it. After that, each secondary electron composition image is converted into a monochrome image and binarized, and the number of pixels in a portion corresponding to the first phase region 31 and a portion corresponding to the second phase region 32 in each field of view is measured, Added each.
  • EDS energy dispersive X-ray analysis
  • volume ratio (volume %) of the first phase region 31 (or second phase region 32) (number of pixels in the first phase region 31 (or second phase region 32) in the field of view/number of pixels in the entire field of view) x 100
  • volume ratio of the first phase region 31 to the volume ratio of the second phase region 32 is calculated, and (first phase region/second phase region) is calculated. did.
  • Electrodes were connected to both sides of the obtained solid electrolyte layer, and the ionic conductivity was measured using an impedance analyzer (manufactured by Solartron, model number SI1260) under conditions of an amplitude of 50 mV and a frequency of 0.5 Hz to 1 MHz. The results are shown in Table 1.
  • the solid electrolyte layers of Examples 1 to 15 had higher ionic conductivities than the solid electrolyte layers of Comparative Examples 1 and 2.
  • Examples 2 to 6 and 8 in which the ratio of the volume of the first phase region to the volume of the second phase region (first phase region/second phase region) is 0.1 or more and 9 or less.
  • the solid electrolyte layers of Examples 1 to 15 had higher ionic conductivity than the solid electrolyte layers of Examples 1 and 7.
  • Example 4 in which the ratio of the number of Si atoms to the number of P atoms included in the first phase region (Si/P in the first phase region) is 1, Si/P in the first phase region is 0.
  • the ionic conductivity was less than 1, and the ionic conductivity was higher than that of Example 11, in which region A and region B had the same volume ratio as Example 4.
  • Example 4 in which the ratio of the number of Si atoms to the number of P atoms included in the second phase region (Si/P in the second phase region) is 3, Si/P in the second phase region is more than 9. , and the ionic conductivity was higher than in Examples 14 and 15, in which region A and region B had the same volume ratio as in Example 4.

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WO2019044901A1 (ja) * 2017-08-30 2019-03-07 株式会社村田製作所 固体電解質及び全固体電池
WO2021145273A1 (ja) * 2020-01-16 2021-07-22 株式会社村田製作所 固体電池
JP2022042604A (ja) 2020-09-03 2022-03-15 ヤマハ発動機株式会社 鞍乗型車両

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019044901A1 (ja) * 2017-08-30 2019-03-07 株式会社村田製作所 固体電解質及び全固体電池
WO2021145273A1 (ja) * 2020-01-16 2021-07-22 株式会社村田製作所 固体電池
JP2022042604A (ja) 2020-09-03 2022-03-15 ヤマハ発動機株式会社 鞍乗型車両

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
IONICS, vol. 7, 2001, pages 469 - 473
See also references of EP4495953A4
SOLID STATE IONICS, vol. 283, 2015, pages 109 - 114

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